Biology

Sarah Allard

Nana Asabere

Christina Harview

Yang Gao

Kristin Jenkins
Nelly Khaselev
Dominique Mckeever
Jane Morris
Mahvish Qureshi
Katie Weng

Chemistry

Suzanne Ali

Kate Butler

Amber Hopkins

Clarah Chelagat Lelei

Erika Lippoldt

Erica Lo

Eden McQueeen

Amber Moore

Rebecca Rothstein

Ashton Shaffer

Sarah Tabi

Tu-Anh Vu

Computer Science

Kerstin Baer

Priscy Pais

Rebecca Rebhuhn-Glanz

Meena Seralathan

2008 Summer Science

Research Fellowship Program

and

Student Abstract

Undergraduate research initiatives are central to the College's approach to science education. All science majors are encouraged to conduct mentored research projects during the summer and/or academic year, and each year over 50% of all science majors do so. Students receive stipends for summer research and academic credit for research performed in the junior and senior years. Since 1989, each summer the College has provided 35-45 students with ten-week research stipends to conduct independent research under the guidance of Bryn Mawr faculty members in the sciences and mathematics. The summer program is enriched by professional development workshops and a poster session at which students present their research to the college community.

The College gratefully acknowledges the financial support for undergraduate research provided by:

Carlos Nathaniel Vicens and Maria Teresa Joglar de Vicens Fund
GlaxoSmithKline
Helen Louise Robinson '66 Fund for the Biological Sciences
Howard Hughes Medical Institute
Merck
National Institutes of Health
National Science Foundation
Office of the Undergraduate Dean
Robert Conner Undergraduate Biology Fellowship Fund

Biology 2008

Summer Science Research Abstract

Ecological compensation mechanisms within pollinator communities in the face of species loss

Sarah Allard and Kristin Jenkins

Mentor: Dr. Neal Williams

Ecosystem services are processes and contributions from the natural world that are essential to human well-being. Among the most important of these services is pollination, which is provided primarily by bees and is required for the successful production of half of the world’s crops. Recent declines in managed honeybees and concerns about food security in an increasingly populous world make it imperative that we understand the role of other wild bee species and the factors that influence pollination to ensure stable pollination. A series of recent articles suggest that pollination, like other ecosystem services, is dependent upon diversity and abundance of species within a system, thus loss of biodiversity may severely impact crop pollination and production. This may occur because the total level of pollination service provided depends on the number of individual bees visiting a crop and on the amount of pollination each individual provides.

Pollinator loss due to human influence could be compensated for by an increase in the number of individuals of remaining species, called numerical compensation. Alternatively species loss could be made up for not an increase in populations, but by an increase in the level of pollination performed by individuals, termed functional compensation. The level of pollination per pollinator is quantified as the number of pollen grains deposited on a single flower by a single bee.

To investigate functional and numerical compensation of pollinators visiting watermelon (Citrullus lanatus), we will survey the diversity and abundance of bees visiting watermelon flowers at a sample of farms in the Delaware Valley and then quantify the number of pollen grains deposited on flowers by members of the most common bee species. Higher deposition by bees at low-diversity farms compared to low deposition by bees at high-diversity farms would indicate the occurrence of functional compensation. An increasing abundance of certain bee species coupled with decreasing diversity would indicate that numerical compensation is occurring. Either of these processes could be expected to buffer pollination function against a loss of bee diversity and abundance. Our results will contribute to understanding the mechanisms that determine the role of native biodiversity on crop pollination and provide key information to farmers and conservation managers in the region.

Synaptotagmin's Role in Neuronal Outgrowth and Branching Patterns

Nana Asabere

Mentor: Professor Karen Greif

Essential to the nervous system are chemicals called neurotransmitters, signals that mediate nerve cell communication. Nerve cells are connected by extensions called ‘processes’ that emanate from the cell body and allow for the propagation of these chemical signals. It is at the synapse, the terminal ending of a process and the interface between it and an adjoining process, that neurotransmitters are released and interpreted by the post-synaptic terminal of an adjoining nerve cell. Before this can occur, synaptic vesicles—neurotransmitter storehouses—must fuse with the plasma membrane and subsequently release their contents via a process termed exocytosis. This step is essential to neuronal communication, and therefore regulates the efficiency with which a chemically encoded message can be transmitted.

Synaptotagmins (syt) are a family of membrane fusion proteins that trigger the release of neurotransmitters; consequently their role in neuronal communication is vital. While this particular function of syt has been extensively detailed, little is known about its functional involvement in nerve cell outgrowth. The following observations have alluded to such roles in the developing nerve cell: syt expression is apparent in developing neurons several days prior to synapse formation; a positive correlation is observed between increased production of syt in neurons and process branching; and an upregulation of syt mRNA is apparent during the peak period of synaptogenesis. The question at hand is this: if syt functions only in neurotransmitter exocytosis, why should it be expressed substantially before any such events occur in the nerve cell? The sum of these observations may implicate syt in developmental growth events of the nerve cell—specifically, process outgrowth, extension, and branching.

This particular project seeks to understand the effect of syt on processes extension, retraction, and branching from the cell body. We will utilize a powerful gene-silencing technique called RNA interference. If effective, RNA interference should decrease the intracellular concentration of syt and allow for the assessment of the effects of syt depletion on forebrain neurons in stage-8 chicken embryos. Results from these tests, will elucidate insights regarding syts functional involvement in neurite outgrowth.

Understanding the Function of SoxR in Streptomyces

coelicolor by Mutational Analysis

Yang Gao

Mentor: Dr. Monica Chander

SoxR is a transcriptional activator that has been extensively characterized in E. coli. In E. coli, SoxR is part of the defense mechanism used by the bacterium to protect itself from oxidative stress caused by drugs such as paraquat, and nitric oxide (NO). The chemical stresses are detected by SoxR via its iron sulfur ([2Fe-2S]) clusters. In the presence of oxidative stress, SoxR activates the expression of another transcriptional activator, SoxS, which in turn activates the expression of more than 40 genes that are responsible for reducing the stresses. The SoxR protein, and the specific DNA sequence it binds, is conserved throughout many other species of bacteria.

One of the species that possesses the homolog of the SoxR protein is Streptomyces coelicolor, a soil bacterium that is more complex than E. coli. One aspect of its complexity is that S. coelicolor produces and secretes secondary metabolites such as antibiotics into its surroundings to eliminate its competitors. It is hypothesized that SoxR in this organism functions to protect S.coelicolor from one such antibiotic, actinorhodin. This hypothesis is based on the fact that, while there is no soxS homolog in S. coelicolor, the conserved DNA sequence to which SoxR binds is found in the promoter regions of two genes, SCO2478 and SCO4266. These two genes are believed to be involved in detoxifying actinorhodin in S. coelicolor.

In order to elucidate the physiological role of SoxR in S.coelicolor, I will construct a soxR null mutant in S. coelicolor. Since SoxR is hypothesized to mediate self-toxicity against actinorhodin, the soxR mutation has the potential of being lethal to the organism. To circumvent this potential problem, the soxR deletion will be made in both the wild type strain (M145), as well as a mutant strain that does not produce actinorhodin (M512). Northern analysis carried out on the soxR mutant strain will allow us to verify that SoxR regulates SCO2478 and SCO4266, and will reveal the function of SoxR in S. coelicolor.

Tissue-specific expression and differential methylation at the

imprinted gene Rasgrf1 in Black 6/Castaneus mice.

Christina Harview

Mentor: Dr. Tamara Davis

Most mammalian genes are expressed biallelically; both the copy of the gene inherited from the mother, and the copy inherited from the father are expressed and functional.  However, about 85 out of the approximately 25,000 genes in the human genome have been found to be expressed monoallelically.  In other words, expression of imprinted genes is limited to only one parent’s copy: either the mother’s or the father’s genetic information is expressed, but not both.  Although imprinted genes account for very few of the total number of genes in the body, they are extremely important for normal development as evidenced by defects in expression leading to abnormal growth patterns and higher mortality in mice.

One proposed means by which this preferential expression is controlled is called DNA methylation.  During the methylation of DNA, methyl groups are added at the 5’ end of cytosines in CG pairs along the DNA strand.  This differential methylation of DNA acts as a way to mark maternal and paternal genes without changing their sequence and allows the cells to regulate their expression appropriately. 

My research focuses on one particular imprinted gene called the RAS protein-specific guanine nucleotide-releasing factor 1 (Rasgrf1), which affects long-term memory function and growth regulation in mice.  Rasgrf1 is paternally expressed and methylated, however, its expression profile has been found to be tissue-specific.  The scientific literature has reported monoallelic expression of Rasgrf1 in the brain and stomach, biallelic expression in the lung and thymus, and no expression in the liver and kidney.  I will assess and analyze the expression pattern in the Black 6/Castaneus strain of hybrid mice that is currently being used in my lab.  We have developed our own expression assay which has confirmed expression of Rasgrf1 in brain, stomach, lung, and thymus, but which has also detected expression in liver and kidney although the literature cites none. This discrepancy could be due to a difference in the strains of mice used for the analyses. My work will investigate whether the expression detected in liver and kidney is monoallelic or biallelic.

In addition, I will gather expression data for placenta, 8.5 dpc embryo head, and blastocysts, which has not previously been analyzed.  The overall goal of my research is to determine the exact expression pattern of Rasgrf1 and compare these data with the tissue-specific methylation patterns in order to determine how they are related to expression of Rasgrf1 in various tissues.

Methylation Analysis of Specific Regions on the Gtl2 Gene in Mice

Nelly Khaselev

Mentor: Dr. Tamara Davis

Imprinted genes are genes whose expression is determined by parent of origin. Normally, each cell contains two alleles (different copies of a single gene), one from each parent, in which both are equally expressed. Conversely, imprinted genes only express one allele: either the paternal or maternal allele is expressed. This research aims to progress towards understanding the mechanism of this type of gene regulation. We believe that DNA methylation, (the addition of a methyl group (CH3) to a cytosine- one nucleotide base of DNA) is a key process in the regulation and expression of imprinted genes. Methylation frequently occurs at imprinted genes on CpG sites in gene promoters - a short span of nucleotide sequence that signals a starting point for transcription. As a result of methylation on CpG sites, the chemical structure of the DNA is altered which affects its ability to be expressed. This research aims to locate methylated CpG sites to better understand imprinted gene regulation.

Gtl2 is an imprinted gene located on chromosome 12, which we are currently studying in this research project. Its paternal copy is methylated and only its unmethylated maternal copy is expressed in mice. To date, two differentially methylated CpG sites have been identified. I am investigating the methylation pattern at another CpG site, located in exon 3 of the Gtl2 gene. The specific region e3 (exon three) is of particular interest because it is rich in CpG residues that signify many potentially methylated sites. In the lab we identify methylated cytosines by a process called bisulfite mutagenisis. As a result of this process all unmethylated cytosine nucleotides are replaced by a thymine; allowing us to identify methylation sites by searching for unchanged cytosine nucleotides in the e3 region of GtL2 gene. Knowing the methylated sites on the GtL2 gene, will brings us one step closer to understanding imprinted

Just Keep Swimming, Just Keep Swimming…

Dominique McKeever

Mentor: Peter Brodfuehrer

 

In all organisms, including humans, rhythmic/repetitive behaviors such as walking are generated by central pattern generators (CPG), or networks of neurons (nerve cells).  In the medicinal leech, swimming, a rhythmic behavior, is produced by a CPG.  Swimming involves episodic sinusoidal movement caused by the alternating contraction of longitudinal muscles (muscles that run the length of the leech) on both the dorsal and ventral surfaces. When the central nervous system is isolated (i.e. the body wall has been removed), the fictive motor pattern for swimming can be produced by electrical stimulation of a peripheral nerve. Interestingly, the length of an elicited swim bout can differ from one bout to the next. The Brodfuehrer lab is currently investigating the neuronal mechanisms that influence the length of these swim episodes.

It has been hypothesized that a positive feedback loop drives the swim CPG and that cell 204, a swim-maintenance interneuron that directly excites several other CPG interneurons (known as oscillators) is a component of this positive feedback loop. The existence of a positive feedback loop indicates that as the activity of cell 204 increases, it activates oscillators to which it is coupled; as the activity of the oscillators increases, the activity of cell 204 also increases, and so on. This raises an interesting question: if a positive feedback loop is involved in generating swimming, why does swimming stop? Previous results have shown that blocking excitatory inputs (those signals that induce behavior) to a portion of the leech central nervous system, specifically segmental ganglion (a mass of cells) 10, decreases the length of the swim bouts elicited by peripheral nerve stimulation (the stimulation of nerves on another ganglion), supporting the hypothesis that a positive feedback loop is at work. My research this summer focuses on determining what factors affect swim bout duration and whether a positive feedback system exists in ganglia other than ganglion 10.

In an attempt to identify cells involved in controlling swimming, we will use electrical stimulation of both peripheral nerves (known as DP nerves) and individual cells in conjunction with an activity-dependent dye, Neurobiotin, tagged with fluorescently tagged anti-bodies. Theoretically, those cells active in the neural pathway for swimming will fluoresce because they will have taken-up the tagged Neurobiotin after being activated by the stimulation of a cell or nerve involved in the pathway. We will apply DNQX (6,7-Dinitroquinoxaline-2,3-dione), a non-NMDA receptor antagonist, to determine whether a positive feedback loop is present in a ganglion. The excitation of neurons vital to leech swimming is mediated by the binding of glutamate—a neurotransmitter (a chemical known to relay signals from one neuron to the next)—to non-NMDA receptors. DNQX binds to the non-NMDA receptors, inhibiting the binding of glutamate. If there is no decrease in swim bout length in the ganglion to which DNQX was applied, then that ganglion does not contain a positive feedback loop for swimming.

The nervous systems of vertebrates and invertebrates are more alike than most expect. Hopefully, with the exploration of central pattern generators vital to the everyday functionality of the leech, researchers can gain insight into the networks of neurons that affect behavior in humans.

Chemistry 2008

Summer Science Research Abstract

Synthesis and Electrochemical Analysis of Transition Metal Complexes

with Various Functionalities for Surface Modification

Suzanne Ali

Mentor: Prof. Jonas Goldsmith

It is possible to functionalize various surfaces by attaching various different types of organic ligands to them. The organic ligands are able to form complexes with transition metals, and an electrode composed of the surface material in question is placed into a solution containing a low concentration of the aforementioned metal complex. The interactions of various ligands with metal and carbon surfaces can be analyzed electrochemically, and in this manner the rate at which these ligands adhere to the surface, based on varying concentration, can be examined.

During this summer research period, we will synthesize 4-methyl-4-(5-bromobutyl)-2,2’-bipyridine and 4-methyl-4-(5-bromononyl)-2,2’-bipyridine. The alkyl halide will be replaced with an amine group (see Fig. 1), and then an amide group (see Fig. 1) attached to a polyaromatic moity, such as pyrene, as seen in figure 3. The purity of each synthesized compound will be determined through Nuclear Magnetic Resonance and Mass Spectrometry. Due to the nature of the experiments, it is necessary that each step of the synthesis produce a particularly pure product. We will then complex this molecule with a transition metal, such as cobalt or ruthenium, as seen in figure 3. Due to the chelate effect, the preference for the formation of a transition metal complex with a bidentate ligand, the bipyridine molecule will form particularly strong complexes. The extended pi electron system which the polyaromatic group possesses will cause it to adsorb strongly to a graphite surface, which has a similar extended pi electron system. Due to this affinity for adsorption, we can use a graphite electrode to observe this process.

We will also examine, electrochemically, the interactions of 4-methyl-4-(5-thiobutyl)-2,2’-bipyridine and 4-methyl-4-(5-thiononyl)-2,2’-bipyridine with gold surfaces. The thiol group (see Fig. 1), which, as with the amine group, replaces the alkyl halide, has strong affinity for gold surfaces. This affinity will cause the thiol group to adsorb strongly to the surface of the gold electrode, and we will be able to examine the interactions of transition metal complexes containing this ligand, as shown in figure 2, with a gold electrode.

Syntheses of [n]Phenacenes

Kate Butler

and
Amber Hopkins

Mentor: Dr. Frank Mallory

[n]Phenacenes are compounds that contain n benzene rings fused together in a zigzag pattern. An example of a [7]phenacene derivative is shown below.

R=alkyl group

The synthesis of [n]phenacenes is of particular importance for the investigation of whether pseudo one-dimensional versions of the pseudo two-dimensional graphite sheets possess similar patterns of conductivity to the graphite sheets. Previously, an [n]phenacene having 11 fused rings has been synthesized by the Mallory group. [n]Phenacenes with n > 6 are extremely insoluble, so to produce larger [n]phenacenes by chemical synthesis, solubilizing groups (R) must be attached. [n]Phenacenes with n > 11 have been attempted, but have proved unsuccessful due to issues of solubility based on the various R-groups used.

The most recently concluded study tested a branched 12-carbon chain and a straight 12-carbon chain as solubilizing groups, both of which proved to make the phenacene product too soluble. Currently, solubilizing groups of shorter carbon chains are the focus of our investigation in hopes of obtaining correct solubility. Two possible schemes contain 8-carbons each, one straight chain and one branched chain.

Using synthesis schemes beginning from 1-bromobutane and 1-bromooctane, a sequence of reactions will be explored in the attempted syntheses of [7]phenacene and [15]phenacene derivatives.

Using Polymerase Chain Reaction-Restriction Length Fragment Polymorphism (PCR-RFLP)

method to establish Genetic Variation in Local Mushrooms and Flies

Clarah Chelagat Lelei

Mentor: Dr. Susan White

Restriction Fragment Length Polymorphism (RFLP) is a variation in the DNA sequence in a genome. In PCR-RFLP technique restriction enzymes plays an important role in DNA cleavage. Restriction enzymes recognize a particular short segment of double stranded DNA that consists of 4 to 12 base pairs. These sites are called restriction sites and they vary in different species because it can occur in the middle of a DNA strand or at the ends. The sites are also palindromic- that is the 5’ to 3’ sequence on one strand is identical to the 5’ to 3’ sequence on the antiparallel complementary strand. The segments resulting from restriction digest vary in size and thus can be detected using gel electrophoresis. For example, HinfI restriction enzyme recognition site is 5’TCGA…3’, HaeIII recognizes 5’GGCC…3’ and Taqα1 recognizes 5’…GANTC…3’ The length of the cleaved DNA varies, and the variation can be detected by performing a gel electrophoresis. The aim of the research is to find out if PCR-RFLP can be used to explain the diversity in the local mushrooms and flies based on the DNA sequence.

My summer research will involve extraction of DNA from local mushroom species and flies. I will then amplify the DNA I have extracted using the Polymerase chain reaction. Specific regions of the DNA will be amplified by thermostat Taq polymerase. A pair of single stranded DNA will act as replication primers and delimits the region of the target molecule that will be amplified. The amplification will be followed by a restriction digest using different restriction enzymes. Then the agarose gel electrophoresis will be performed to visualize the differences in the resulting restriction digest.

If the PCR-RFLP method works, the results from this experiment will help in exploring the genetic variation in mushrooms. The results might also help in explaining why some mushrooms are edible and why some are poisonous and why some insects harmful. The method might also be applied to other species and this may help in answering questions concerning molecular diversity.

Synthesis and Characterization of DNA-Intercalating and Potential Photocleaving Ru(II)-bis(bipyridine)-Pteridinyl Complexes and Similar Co(III) Complexes

Erika Lippoldt

Mentors: Professor Sharon Burgmayer and Shannon Dalton

Abstract. Small transition metal molecules have been the object of many studies due to their interactions with DNA and the resulting effects on the regulation of DNA transcription and replication, as well as their potential as pharmaceuticals. Ru(II) compounds are especially useful as probes due to their stability and photophysical properties. Bis(bipyridyl) Ru(II) complexes of pteridinyl-phenanthroline ligands have been of particular interest because pteridinyl ligands possess H-bonding patterns complementary to the purine and pyrimidine bases of DNA and RNA. The pteridinyl ligand of these Ru-pteridine complexes is capable of inserting itself between the base pairs of DNA, thus binding to DNA via intercalation. Other metal complexes, including certain Co(III) complexes, have been known to cleave DNA in the presence of light (photoactivated cleavage of DNA). Such metallointercalators are practical for their high affinity for double-stranded DNA and because they include a range of redox-active metal centers and ligands.

In my summer research, I will synthesize five Ru-pteridinyl complexes previously studied in this laboratory by varying the pteridinyl-phenanthroline ligands, in addition to which I will synthesize the DNA intercalator [Ru(bpy)2(dppz)]2+, which has been much studied in other laboratories and is used here as a positive control. The multiple-step synthesis is similar for each complex: 1,10-phenanthroline-5,6-dione is synthesized and then reacted with a diamino-pyrimidine to obtain the various ligands, which are then coordinated to RuII by reacting them with Ru(bpy)2Cl2 to obtain the final Ru complex of the form [Ru((bpy)2(L)]2+, where L stands for any of the five ligands. The ligands of interest are L-amino, L-diamino, L-pterin, L-allox and L-Me2allox. All synthesis products are characterized using 1H-NMR, IR and ESI-MS. In addition to these syntheses, I will investigate the synthesis of analogous Co(III)-pteridinyl or other metal-pteridinyl complexes, which will be explored as DNA cleaving agents. DNA cleavage studies could lead to the determination of the metallointercalator-DNA binding sites as well as the discovery of useful DNA manipulation techniques and potential pharmaceuticals.

Functionalizing Surfaces with Transition Metal Complexes

Erica Lo

Mentor: Dr. Goldsmith

 

The nanotechnology field is growing rapidly thus novel methods in modulating behavior on the nanoscale is necessary for the development of nanoelectronics. In order to control the behavior of this technology, one must appeal to redox chemistry. Adding functionality to surfaces is possible through the synthesis of metal complexes with the appropriate substituents, allowing adsorption to various surfaces.

The focus of this research is to achieve the synthesis of a transition metal complex capable of the aforementioned functionalization. First, a bromoalkyl chain of varying lengths is to be added to a 4,4’-dimethyl-2,2’-bipyridine molecule giving 4-bromobutyl-4-methyl-2,2’-bipyridine or 4-bromononyl-4-methyl-2,2’-bipyridine. The added bromine will then be replaced with a thiol, an SH group, which has the capability of adsorbing to gold surfaces. The bipyridine portion of the molecule also enables the formation of a stable metal complex. In this case the transition metal is ruthenium as shown in Figure 1.

The second goal is to synthesize a molecule with the capability of adsorbing to varying carbon surfaces. The first step is the same as the formation of the previous molecule. Once the molecule has a bromoalkyl substituent, the bromine will be converted to an amine. This NH2 group will allow the coupling of polyaromatic groups resulting in a ligand with an extended pi system. The ligands will then form a complex with a transition metal giving a product as seen in Figure 2 where the polyaromatic group shown is pyrene. The manner of how these molecules adsorb to gold, platinum surfaces, or carbon surfaces will then be observed by using electrochemistry.

 

Figure 1.                                                        Figure 2.

Functionalization of a Variety of Carbon Surfaces with Transition Metal Complexes: Glassy Carbon, HOPG and SWNT

Eden McQueen

Mentor: Dr. Jonas Goldsmith

The behavior of several carbon surface types functionalized with the compound below (1) will be explored.

A sample of complex 1 was synthesized and re-crystallized to obtain a workable powder. Polished glassy carbon, highly oriented pyrolytic graphite, and single-walled carbon nanotubes (SWNT), were functionalized using 1 by dissolving the complex in acetonitrile and exposing the carbon surface to a dilute solution of 1. The HOPG and glassy carbon functionalized surfaces were characterized by the observed redox behavior on an electrode surface using cyclic voltammetry. Experiments used a range of concentrations from 0.1μM to 2.0μM, and were conducted over the period of 1.5 hours. For each data point the reduction peak height was recorded. The equation   was used to obtain the electrode coverage for each data point. The kinetics and thermodynamics of the adsorption process can be determined by an analysis of coverage (Γ) versus time and coverage versus concentration. In order to study the adsorption behavior of 1 on SWNT, an additional step was required to disperse and separate the SWNT material. Suspensions of SWNT were created using several solvents, including Milli-Q water, chloroform, ethanol, and isopropanol. A range of surfactants, SDS, PVP, PVA, and Triton X-100, were also used and compared as to their relative utilities for suspension formation. Suspensions that appeared to be well-distributed were diluted and filtered. Atomic force microscopy was used to characterize the appearance of the SWNT suspensions. The dispersions will also be cast onto metal electrodes to study their adsorption behavior.

A Thermal Denaturation method for distinguishing

between K-turn and non-K-turn RNA

Amber R. Moore

Mentor: Dr. Susan A. White

 

Abstract. Protein-RNA interactions are important for cellular growth and regulation.  Proper interactions between protein and RNA require both of their interfacial sites to be conserved for specific recognition and binding.  Organisms, like Saccharomyces cerevisiae (yeast), have evolved in ways that condense multi-component and multi-step pathways into more self-contained processes.  This allows the cell machinery to maintain, if not improve, its specificity and regulation, while increasing the efficiency of these vital mechanisms.  Knowledge of protein and RNA interactions continues to aid in the development of therapeutic    approaches for the treatment of various diseases.

The S.  cerevisiae autoregulatory ribosomal protein L30e, or RPL30, is capable of inhibiting the splicing and translation of its own transcript and mRNA by forming a protein-RNA complex.  The L30e protein has a single domain composed of four beta sheets and four alpha helices.  The L30e RNA is present in two strands and assumes a helix-internal loop-helix motif, commonly referred to as the kink-turn, or K-turn motif.  The internal loop, comprised of one strand with unpaired nucleotides and a second strand with missing nucleotides, connects a canonical stem (Watson-Crick base paired helix) to a non-canonical stem (helix containing some non-Watson-Crick base pairs).  L30e recognizes and binds to the K-turn RNA when there is an excess of L30e protein (not being incorporated into the ribosome).  This forms the L30e protein-RNA complex that represses further protein expression.  We expect to find that any RNA sequence mutation altering the K-turn will disturb the protein-RNA interaction of the L30e complex. 

              Thermal denaturation will be the applied method in differentiating between K-turn RNA and non-K-turn RNA while Mg2+ is present to simulate cellular conditions and assist the K-turn RNA in maintaining its sharp bent structure.  Results are expected to show differences in the stabilities among the RNA variants being tested: BP, KT12, and KTAU.  The BP (base paired) variant has complete Watson-Crick base pairing among the nucleotides, whereas the KT (kink turn) variant has non-Watson-Crick base pairing which causes the helix-internal loop-helix motif in the RNA.  KT12 has an adenine (A) replaced with a uracil (U) at the twelfth nucleotide position in the K-turn region of the RNA.  KTAU has the same A to U mutation, but it occurs outside of the K-turn region.  Thermal denaturation is not only expected to show differences in stability between the BP and KT RNA, but also between the KT variants with nucleotide mutations inside and outside of the K-turn region. 

Modeling the Molybdenum Cofactor

Rebecca Rothstein

Mentors:  Dr. Sharon J. Nieter Burgmayer and Graduate Student Kelly Ginnion

The second row transition metal molybdenum, atomic number 42, is a naturally occurring element in a countless number of biological reactions.  Assuming the role as a biological catalytic center, molybdenum occupies the catalytic site in more than forty essential enzymes, which control the oxidation-reduction reactions for a broad range of inorganic and organic substrates.  Considering the ubiquitous nature of molybdenum enzymes, with its presence in everything from simple bacteria to human beings, it is no wonder that the element has a profound evolutionary history, contributing significantly to the biological function of virtually every living organism.  From the human perspective alone, three molybdoenzymes—sulfite oxidase, xanthine oxidase and aldehyde oxidase—are essential for proper health.

Contrary to popular scientific belief, molybdenum has not survived the perils of evolution single-handedly but rather it is now believed that such enzymes are the chemical descendants of tungsten enzymes, whose origin was traced to the most ancient of organisms, archaebacteria. Consequently, it has been found that the structures and functions of tungsten enzymes in bacteria are similar to those of the molybdenum enzymes typically found in more complex species like human beings.  Molybdenum and tungsten enzymes are the only biological molecules to utilize the dithiolene as a metal ligand.  Together, the dithiolene ligand bound to the molybdenum center in all molybdenum enzymes has been identified by the name of the molybdenum cofactor (colloquially referred to as Moco) illustrated in figure 1 below.
             

Figure 1.  Moco consists of a pterin structure (blue) fused to a pyran (red) ring bearing an exocyclic dithiolene group (green) that is the site of metal coordination.

The identity of the molybdenum cofactor, the catalytic site in pyranopterin molybdenum enzymes, was sought through studies of the molybdenum enzymes and through synthetic efforts to assemble compounds that reproduce key spectroscopic, structural, and reactivity properties of the catalytic Mo center.  The Burgmayer laboratory has developed novel models for the molybdenum cofactor which incorporate key structural features in all Mo and W enzymes including a dithiolene chelate joined to a pterin.  The goal of this summer laboratory experience will be to synthesize the precursors of Moco models and then to utilize the starting material in order to build the pterin-dithiolene ligand.  Generally, the synthetic scheme will entail coupling a Mo-tetrasulfide complex with a pterinyl alkyne to produce [Tp*Mo(O/S)(pterin-dithiolene)] complexes in both Mo (4+) and Mo (5+) oxidation states.  While previous work has focused on the characterization on the purified Mo (5+) species, there is a strong hope of exploring the fascinating redox chemistry associated with Mo (4+) in the near future

Using Analytical Centrifugation to Identify and Study Kink-turned RNA

Ashton Shaffer

Mentor: Dr. Susan White

RNA (ribonucleic acid) makes it possible for the genetic instructions encoded in DNA to be used to assemble essential molecules like proteins. RNA’s structure allows it to participate in reactions like transcription, which is basically the production of a complementary copy of DNA, and splicing, which is the processing and editing of RNA prior to use for protein production. RNA’s secondary structure, when it is double stranded, tends to consist of nucleotides that base pair in the traditional Watson-Crick manner, where hydrogen bonds are formed only between guanine-cytosine and adenine-uracil, and form a helical configuration. It can, however, have a kink-turn, which contains three unpaired nucleotides followed by several nucleotides that do not exhibit Watson-Crick base pairing. L30, a protein found in yeast, has been found to autoregulate its transcription and splicing by binding to its own RNA transcript, which forms a kink-turn. Learning more about this mechanism of identification, binding, and regulation will provide insight into RNA-protein interactions, which makes kink-turned RNA and L30 particularly interesting.

Kink-turn RNA has previously been studied using radioactive isotopes in gel mobility experiments where the differences are only detected in the presence of Magnesium (Mg2+).
Our objective is to identify RNA with kink-turns without using techniques like radioactive gel electrophoresis and instead utilizing a process called analytical centrifugation. This alternate approach is based on the biophysical principles of hydrodynamics and observes the rate of migration of RNA as it is spun at high speeds in a fluid environment in order to infer its structure. We plan to test it both with and without Mg2+ in solution with the RNA to determine whether or not there are any discernable differences in the resulting RNA mobility. It has the added advantage of permitting us to study RNA in an environment that closely resembles what is actually present in a cell. Our hope is that analytical centrifugation will enable us to not only distinguish the difference between kink-turned and base paired RNA, but also to tell to what degree the RNA is kink-turned (larger and smaller angles). We are also interested to observe whether or not Mg2+ must be present in order to make these distinctions. Being able to differentiate kink-turned and base-paired RNA adds to our general understanding of how structural changes affect the ability of proteins and RNA to interact and the chemical mechanisms of transcription, splicing, and regulation.

Exploration of the Conjugate Addition Reactions of Carbon Nucleophiles

to Birch Cope Sequence Products

Sarah Tabi

Mentor Dr. Malachowski

Generally, I will be experimenting with different carbon nucleophiles of Birch Cope sequence products for multiple conjugate addition reactions. Below [Scheme 1] includes the outline of the starting materials that I have been synthesizing in order to do this. The last three steps of this scheme illustrate the Birch Cope sequence that will produce the starting material necessary for the aforementioned reactions.

I will delve into other carbon nucleophiles as well, including organocuprates, cyanide, and ketone/ester/nitro enolates. In this process, the steric limitations of the nucleophiles will be revealed.

In conducting these reactions, the stereoselectivity of the conjugate addition will become evident. The progress in this will aid in the asymmetric synthesis of cyclohexyl rings that possess multiple tertiary and quaternary asymmetric molecular sites. These types of structures are found in numerous biologically active molecular structures, such as saudin, anisatin, and jiadefenin. This type of understanding will help in future research involving the synthesis of complex, biologically active natural products.

Design Dithiocarbamate Inhibitors with Increase Binding Affinity

to Indoleamine 2,3-Dioxygenase (IDO)

Tu-Anh Vu

Mentor: Judith LaLonde

Indoleamine 2,3-dioxygenase (IDO) is an immunosuppressant enzyme that is the rate-limiting enzyme in the production of quinolinic acid from tryptophan through the kynurenine pathway. Researchers have suggested that tumors can elevate the levels of IDO and use it to facilitate an immune escape. Previous studies have shown that knockout mice without IDO perform better in chemotherapy treatments than mice with IDO. Thus, designing IDO inhibitors may improve patients' responses to caner treatments. In this study, we will design dithiocarbamate inhibitors with increased binding affinity to IDO. In previously published work, our group has shown that hydroxyl and thiol substitution on the benzyl ring of 4-phenyl-imidazole improve binding affinity. Docking calculations of the dithiocarbamate compounds predict that the dithiocarbamate group binds to the heme iron, while the amino-linked benzyl ring of the dithiocarbamate is buried in the back of the cavity. We will apply lessons learned from the -OH and -SH substitutions of phenyl-imidazole to the dithiocarbamate class of compounds. Computational chemistry methods will be used to vet in silico prototype compounds prior to synthesis. The genetic docking algorithm, Gold, is being used to evaluate twenty various substitutions of the amino-linked benzyl ring of the dithiocarbamate. Computational results will determine the best candidates for synthesis.

Computer Science 2008

Summer Science Research Abstract

Kerstin Baer and Priscy Pais

Mentor: Dr. Douglas Blank

Developmental Robotics is a relatively new approach to artificial intelligence. Instead of programming robots to perform pre-specified tasks, Developmental Robotics aims to equip them with a learning routine that allows them to make sense of their sensomotoric capabilities, discover their environment and perform self-motivated actions. Artificial neural networks have emerged as a promising learning and control mechanism. Modeled after biological neural networks, artificial networks consist of a set of interconnected units that perform calculations on a set of inputs (e.g. the sensor readings of a robot) to get some output that is appropriate for the given situation (e.g. motor commands for the robot). By manipulating the connections between units and adding more units when necessary, a neural network can adapt to new situations and learn more complex behaviors.

When a network-controlled robot is getting familiar with its environment, that is, learns to predict its environment, it has to make decisions where to move next to collect more information. Ideally the robot would pay attention to an object long enough to understand its basic features, but not so long that it forgets everything else around it. In this context we want to explore what it means for a robot to 'pay attention' to something. We intend to build an architecture around the neural network that might serve three purposes: make appropriate abstractions from the input data to make the robot “aware” of what it is paying attention to, guide the actions of the robot to keep it focused on the object of interest, and pre-process the input data to increase the network learning rate.

Meena Seralathan

Mentor: Dr. Doug Blank

Robotics is becoming a rapidly growing facet of computer science research. Specifically, research in artificial intelligence (AI) and developmental robotics (the study of programming robots to learn independently) has become increasingly popular with the development of more sophisticated software and hardware. Now, instead of worrying about the costs of a robot or the limitations of current hardware or software, one of the biggest questions posed in this field of research is how one can program a robot to act autonomously (that is, how a robot can be programmed to think for itself, "feel" for itself, and make decisions based on its own motivations).

In our research we will be exploring these concepts through a humanoid robot. We will try programming behaviors for the robot to see how easily it can interact autonomously with its environment (possibly with the use of a camera, IR sensors, light sensors, or touch sensors), and determining what sort of programs allow the robot to learn more about its environment, and what sorts of programs cause the robot to best remember the locations of obstacles or other important objects in the environment. We will also allow the humanoid robot to be simulated in the robotics software Pyro (Python Robotics), so we may test developmental programs for the robot without having to use a physical robot.

Rebecca Rebhuhn-Glanz

Mentor: Dr. Doug Blank

In the last few years, the number of students studying or majoring in computer science has dropped dramatically. Many students see computer science as hard and boring. In response, researchers at Bryn Mawr, Georgia Tech, and Microsoft Research have developed Myro, a program aimed at making computer science accessible and interesting to students through the use of robots. To this end, it enables educators to teach their introductory courses in a programming language that does not require students to worry about every last semi-colon and curly bracket, but still allows them to cover the basic concepts of programming thoroughly enough to allow students to move on to more traditional and sophisticated languages without difficulty. I am helping adapt Myro to work with several programming languages commonly used in introductory courses, as well as creating a new graphical programming language (tentatively named Dinah) that will allow students to design animations, games, and other interactive programs, and to communicate with a robot. This should make it easy for educators in other schools to use Myro in their own classes, and will attract more students to computer science.

Geology 2008

Summer Science Research Abstract

Improving Education on Energy Resources and Environmental Policy

Erin Lynch

Mentor: Dr. Don Barber

As global economies pump greenhouse gases and other emissions into the atmosphere, causing a variety of negative environmental impacts, the supply of non-renewable fossil fuels that the world relies on for energy is being rapidly consumed.  In order to address this unsustainable situation, improved education regarding the associated issues, including climate change is a critical need.  Through expanded education about the environmental, economic and social impacts of the changing climate, we will reach a point of literacy at which students are better able to assess what is being done to counteract these effects and what more there is to do in the line of policy and technology.  This project explores some of the methods of teaching climate change issues with a focus on alternative and renewable energy resources and the relevant public policy issues.  Students will begin the semester with an exploration of climate change and other impacts of our energy consumption patterns.  They will explore issues of energy usage and sustainability for the growing world population, taking into account the developing market for alternative and renewable energy.  After understanding the technology and capacity of these systems, students will begin to address the problems of policy-making for international environmental regulations.  Articles like “The Tragedy of the Commons,” written by Garrett Hardin provide a base for thinking about governing that which cannot be owned such as the atmosphere.   Through hands-on module and project development, like “Fish Banks, Ltd.,” a role playing game and microcosm for sustainability created by Dennis L. Meadows, students will learn about depletion and other issues facing the world’s shared resources.  Students will be asked to think about their own impact on the environment and by the end of the semester, students learn to use HOMER, an energy modeling program designed by the National Renewable Energy Laboratory, to assess personalized questions about energy use at home, on campus or in the community.   Through carefully selected readings and current events we are developing a curriculum that will enable students to begin to understand and address this multi-dimensional issue in order to work toward solutions. 

Physics 2008

Summer Science Research Abstract

Emily Altiere

and
Deborah Farrington

Mentor: David Nice

When a star more massive then our Sun nears the end of its life, it collapses into a very small and dense object, known as a neutron star. Due to conservation of angular momentum this neutron star will have a much greater rotation rate then the original star. Sometimes neutron stars emit beams of radio waves, which we detect as pulses due to the rapid rotation of the neutron star. This effect is similar to that of a lighthouse beam crossing our line of sight. This is why we call them pulsars.

We will use the Arecibo Observatory to look at 35 recently discovered radio pulsars within our Galaxy with periods ranging from milliseconds to seconds. Our research involves measuring the pulse intensity of these pulsars and looking for patterns and consistencies in these measurements on day-to-day and pulse-to-pulse time scales over a range of frequencies. The pulsar signal is a small fraction of the overall energy gathered by the telescope. (Other astronomical sources, as well as the amplifiers in the telescope, contribute to a large background noise.) Thus, measuring pulsar intensities is a challenging process. Although pulsars have been studied for many years, little is known about the process of their radio wave emission. Our measurements will help in the general understanding of the pulsar population, life cycle, emission mechanisms, and place in our Galaxy.

Methyl and tert-Butyl Rotation in Solid 5-tert-butyl-4-hydroxy-2-methylphenyl sulfide

Laura Popa

Mentor: Professor Peter Beckmann

We conduct variable temperature (90 K - 330 K) and variable frequency (8.50, 22.5, and 53.0 MHz) solid state 1H nuclear magnetic resonance (NMR) relaxation experiments on a sample of 5-tert-butyl-4-hydroxy-2-methylphenyl sulfide. The goal is to study the intramolecular reorientation of the methyl and tert-butyl groups present in this molecule and to correlate the motions of these groups with the molecular and crystal structure.

The reorientation of the methyl and tert-butyl groups is modeled by the motion of random quantum mechanical hopping, described by Poisson statistics, with an average time between hops modeled using the Canonical Ensemble. Due to their position in the molecule, different intramolecular groups need different energies to reorient. Previous experiments on planar aromatic molecules have shown that the methyl group that is in the plane of the aromatic structure reorients at the same rate as the entire tert-butyl group. The two out-of-plane methyl groups reorient at a different rate. By fitting the dependence of the 1H relaxation rate on temperature and NMR frequency, values of the rotational barriers for methyl and tert-butyl rotors are obtained.

Designing, Building and Programming Tevbot

Teyvonia Thomas

Mentors: Dr. Doug Blank and Dr. Elizabeth McCormack

Robots are complex mechanical systems capable of performing various physical and computational tasks normally controlled by humans, a pre-defined program, or a set of rules using artificial intelligence techniques. Robots have a wide range of applications including car production, space exploration, medical surgery, housekeeping, education and entertainment. The goal of my research is to acquire a fundamental knowledge and understanding of the process involved in the engineering of TevBot, the robot I will design and build. TevBot will be a multi-legged, articulated robot with the ability to avoid obstacles and cliffs, take various pictures and recall them, move periodically to specific locations (precision positioning), climb up small stairs, dance, do artwork and play games. Extensive research will be carried out on existing robots in order to understand the electronics, mechanics and the software required to manipulate these devices.

My project will begin with the exploration and modification of the Roomba (a robotic vacuum cleaner) in order to understand its hardware and software infrastructure and to give it new and complex behaviors. Both Myro (the software that controls the scribbler robot used in the introductory Computer Science course) and the software for the scribbler’s Fluke (a chip that provides a bluetooth, sensors and a color camera) will be expanded to control the Roomba. The Roomba’s academic and recreational purposes will then be explored. My research also involves assembling and programming various forms of robots including a humanoid, a hexapod spider and an obstacle detection car using a robot kit. This aspect of my project will give me a great deal of familiarity with the servos (electric motors) that will be used in building TevBot as well as the processor and software I will need to control and program TevBot. The remainder of the research will be devoted to building a prototype for TevBot and programming it as well as developing a graphical user interface that will enable users to easily control TevBot.

My hope is that this research will be used as a framework for a course in Physics and Computer Science that will empower and teach students how to design and build their own robots. I also intend to use this project as a platform for exploring and conducting more research into developmental robotics, a study that involves creating learning methods for robots to give them sophisticated behaviors that have not been directly programmed into them.

Psychology 2008

Summer Science Research Abstract

Memory and Aging

Margaret Cheng

Mentor: Professor Thapar

It is common knowledge that memory deteriorates with age. The working memory (short-term memory) of older adults is poorer than that of young adults and it is unclear why. Previous research has suggested that reduced memory ability may reflect a reduction in working memory capacity and/or the use of less effective strategies by older adults. This study aims to test these two hypotheses and determine whether older adults merely have insufficient memory storage capacity or whether the differences between working memory in older adults and young adults is due to differences in the cognitive strategies that they use (e.g. phonological rehearsal strategies, semantic-based and imagery-based strategies). This study will also examine the effect of prediction on performance and whether higher or lower confidence ratings impact performance. 20 young adults and 20 older adults will be recruited and tested on a series of working memory tasks. After each task, they will be given a questionnaire and asked to report the strategies they use and their confidence ratings. The results of this study will shed light on the effects of aging on memory performance and help us better understand why memory deteriorates with age.

Symbolic Gesture Transparency

Lena Kadota

Mentor: Lauren J Myers

We use symbols in everyday life, whether it be following traffic signs while driving to work, making sure to following care instructions while doing the laundry, or writing a letter, we are exposed to and use symbols in everyday life. Understanding how to read and use symbols is an important step in child development. The project described here strives to learn more about children’ understanding of gestural symbols in relation to previously found developmental trajectories and simple explanations of what the gesture represents and how it resembles it. Arbitrary gestures as used here refer to gestures that do not have an obvious resemblance to their referents – the things that the signs represent. Iconic symbols are those that do have a resemblance to their referent such, as the motion when pretending to rock a baby in ones arms.

We are interested in whether children can see the "transparency" in gestures that, to adults, resemble the things that they stand for. For instance, holding up your thumb and pinky to your ear means “to call” or “telephone” is a well known and iconic gesture whereas many people would not be able to guess that covering your face with your hands twice means “Halloween.” Children are not born with the insight to “see through” or recognize the resemblance between the gesture symbol to its referent, rather through experience they develop this understanding.

In the present study, we selected noun signs from American Sign Language Signs, using an a priori classification of iconicity versus relative arbitrariness to the referent. In Study 1, we will investigate whether children also perceive these signs as iconic and arbitrary. Three- to five-year-old children will be shown the signs and were asked to choose, from a series of six picture cards, which card they believe matches the gesture performed. We predict that older children will correctly identify the referent more often for the iconic gestures than for the arbitrary gestures, that younger children will score low in overall accuracy, and that younger children will show no difference in accuracy between conditions.

Next, Study 2 will examine the nature of the predicted effect of Study 1. Do younger children do not spontaneously see the resemblance to the referent for iconic gestures, or is the resemblance not apparent to them even upon explanation about the shared features between the symbol and referent? Thus, Study 2 will examine the effects of simple explanation about the gesture on children’s accuracy in identifying the correct referent. We hypothesize that in the condition with no explanation, participants would correctly identify the iconic gestures with more precision than the arbitrary gestures. In the condition with simple explanation, participants should perform equally well in the two categories because we will have provided them with insight into the commonalities between the symbol and the referent. These results should show that children’s developing insight into the commonalities between a symbol and its referent is one step in children's symbolic development. Through experience, we learn to “see through” a gesture to the referent that it stands for, regardless of whether the gesture is iconic or arbitrary.

A Preference for Hard Work?

Katherine Kellom

Mentor: Professor Paul Neuman

This experiment explores the effects of a particular history on what is ordinarily termed ‘work ethic.’ Other researchers demonstrated that pigeons prefer stimuli that had previously been correlated with larger response requirements over stimuli that had relatively smaller response requirements. Research in this laboratory with different procedures produced contrary findings, which support the general principle that pigeons prefer stimuli paired with a lower response requirement or a shorter delay to reinforcement, regardless of history. For this reason, we are attempting to replicate the original study with the same procedures. In training, either one or twenty pecks will be required in the presence of a response key lit yellow. Each response’s requirement will be followed by separate simple simultaneous discriminations: a peck in the presence of one color will produce food (SD) and a peck in the presence of the other will not be reinforced (SΔ). The test trials will involve either a choice between the two discriminative stimuli (SD FR1 and SD FR20) or a choice between the two s-deltas (SΔ FR1 or SΔ FR20).

Comprehension of Body-Part-as-Object and

Imagined-Object Gestures in Toddlers

Nicole Kurtz

Mentors: Professor Robert Wozniak and Kristin Kopple

        Body-Part-as-Object (BPO) and Imagined-Object (IO) gestures are two forms of empty-handed gestures that signify an object through visual resemblance to an action normally associated with the specific referent.  In BPO gestures, a body part takes the place of the object when an action related to that object is performed.  For example, a fist moving up and down in a pounding motion may represent the action of hammering.  In IO gestures, the observer must visualize or imagine the object.  For example, to convey the action of a hammer using an IO gesture, the hand is slightly opened as if grasping an imaginary hammer, while the arm flexes to perform the pounding action of hammering.  The goal of our research is to understand the age-of-onset for the comprehension of empty-handed gestures, determine whether one gesture form (BPO or IO) is more readily comprehended, and ask whether toddlers may profit from gesture comprehension training.  Furthermore, we are interested in whether gestures for certain objects (e.g., a hammer gesture versus a crayon gesture) are more easily comprehended than others.

        Participants included 60 typically-developing 30-month-old and 42-month-old males and females from the suburban Philadelphia area.  Each session was divided into 5 experimental phases: Spontaneous Behavior, Baseline, Training/Filler, Posttest, and Verbal Comprehension.  In each trial of the 5 phases, the participant retrieved objects from a box with four partitioned compartments, which held 4 randomized objects. The Spontaneous Behavior phase allowed the participant to freely select 2 objects of his/her choice.  The Baseline phase assessed the participant’s level of gesture comprehension prior to gesture comprehension training, as the experimenter asked the participant to retrieve target objects using either BPO or IO gestures.  The Training phase involved the experimenter asking the participant to retrieve target objects using BPO or IO gestures, but, contrary to the other phases, the child received verbal feedback about his/her performance.  For a participant not in the Training condition, a Filler task involved the experimenter asking him/her to retrieve target objects using verbal request instead of gestures.  The Posttest phase assessed the participant’s comprehension of gestures after receiving gesture comprehension training.  Finally, a Verbal Comprehension phase measured the participant’s language skills, as the experimenter verbally requested target objects.  

        Data were coded by examining which objects each participant chose in order to assess the participant’s initial level of gesture comprehension and improvements in gesture comprehension after gesture comprehension training.  We hypothesize that 42-month-old toddlers will comprehend gestures more successfully than the 30-month-old toddlers, that BPO gestures, which make less of a cognitive demand on the child, will be easier to comprehend than IO gestures, and that children will benefit from gesture comprehension training.

Ariel Puleo

Mentors: Professor Robert Wozniak, Graduate Student Rebecca Bubb

At the present time, Autism Spectrum Disorders (ASD) cannot be reliably detected in children until they reach the age of 3. At this time, many parents begin modified programs and give their children differentiated attention to help them and others cope with their impairments. Research suggests that earlier intervention will have beneficial results in the education and life skills of children with ASD. Thus, the goal of our research is to look at potential early indicators, such as toy play patterns, that can help identify those children who are likely to receive an eventual ASD diagnosis.

Study participants include 8-, 13-, and 18-month-old children who are either part of a no-risk (NR) control group, or part of an at-risk group. The at-risk group consists of the baby siblings of children who have an ASD diagnosis. Subjects were filmed playing in their homes for 45 minutes sessions, 20 minutes of which we are utilizing for this project. When looking at these 20-minute segments, we first determine whether a child is engaging with an object (they must handle or touch the object for more than a second), and then whether their object engagement is sensorimotor or functional. Sensorimotor actions include behaviors such as shake, bang, and rub, while functional play occurs when a child engages in an object in a way that utilizes one of its designed affordances, such as putting the lid on a box.

Since the films were recorded, some of these children have already received ASD diagnosis and it is possible that several more will. As these children are diagnosed, we expect to be able to look retrospectively at the data and discuss our results in terms of which toy-play behaviors may be significant indicators of later ASD diagnosis.

Gesture/Vocalization Combinations as Early Indicators of ASD diagnosis

Hayley Reed

Mentor: Rob Wozniak

Current research has shown that infants (Sibs-ASD) with an older sibling who has been diagnosed with autism are at an increased risk of having an autism spectrum disorder (ASD) themselves.  To date, however, very little research has been done to identify which of these younger siblings will actually receive an eventual ASD diagnosis. In this study, 18 Sibs-ASD and 18 comparison infants with an older sibling but no known risk of ASD (Sibs-NR) were videotaped at 13 and 18 months in naturalistic interaction and directed play with their primary caregiver. Each session took place at home and lasted for approximately 45 minutes. Videotapes were coded for infants’ use of communicative gestures and vocalizations. Gestures were coded as deictic (reach, give, show, point) or representational and vocalizations as words or non-words. In this aspect of the study, the particular focus is on communicative combinations. Communicative combinations involve a pairing between a gesture and a vocalization (e.g., Point to cat and say “cat”). Each infant’s data was coded for the number of reaches, gives, shows, and points they made that overlapped with a vocalization (word or non-word).  Data for Sibs-ASD who have gone on to receive as ASD diagnosis will be compared to that from non-diagnosed Sibs-ASD and Sibs-NR in the hope that the information collected will contribute towards an earlier ASD screening for all infants and therefore eventually allow for earlier treatment options.

The Effect of Instruction on Children’s Symbolic Understanding

Susanna Tolkin

Mentor: Professor Lauren J. Myers

Symbols are everywhere in our world; we use them when we read and write, we see them in our homes and every time we step outside, and we need them to communicate to others. In the most general sense, a symbol is anything used to represent anything else. Because we use symbols in communicative contexts, a deeper understanding of symbolic thought tells us more about how children's minds develop. Previous researchers have discussed pictorial representation as a complex interplay between several factors: the creator, the user, the picture, and the represented object. What remains to be shown is whether children flexibly adapt their symbols to the following conditions: (1) when they receive insight into the mind of the person who will be using their drawing, and (2) when they are made aware that a drawing is insufficient to communicate in a particular context. For instance, an inexperienced symbol-user may misunderstand a perfectly good drawing, and the failure should be attributed to the person, not the drawing. Similarly, if the drawing resembles both the intended object and another available object equally as well, failure could be attributed to the drawing (not the symbol-user). This study will investigate whether children are sensitive to the ways in which these factors influence effective drawing and communication.

Six- to eight-year-old children will be presented with a set of toys that can be easily represented by one simple symbol. For instance, a crosshatched circle that is used to represent three spherical toys with holes throughout their surfaces. The experimenter will then tell the child that the goal of the game is to draw one of the toys in order to communicate to an absent person. Previously, this person was supposed to use a drawing to select the target object from the array of toys, but failed to do so correctly on her initial attempt. We will vary the attribution for her failure: in the drawing condition, the symbol looked too much like all three toys, whereas in the audience condition, the symbol-user always performed poorly at this kind of game. Thus, in one condition, the liability rests with the drawing, but in the other condition the failure can be blamed on the naïve symbol-user. The child will then see a second set of toys that also possessed similar physical characteristics to each other. Next, the child will be asked to create one symbol to represent one toy so that the other person could figure out which toy to pick based on that symbol.

We predict that younger children will not understand that an object can be represented in many ways, and that their depictions of the target toy will be more ambiguous than the depictions created by the older children. Older children should be more likely to understand the subtleties of effective communication, and will therefore represent the object in multiple ways, such as by using words or more detailed drawings. Previous research also indicates that younger children will also be more likely to blame communication failure on the receiver. The results of this study will shed further light on the developmental progression of children's understanding of symbols and other people's minds.