Our next webinar will take place via the internet on Tuesday June 8th at 8PM EDT/1AM GMT (June 9). Sign up on our mailing list to receive the Zoom link!
We hope to see/hear from you all at one of our sessions or as one of the next speakers. If you are an early career scientist and would like to present your research, don't hesitate to submit an abstract today! For now, please learn more about our current speakers and their research below. We also thank the generous support from Cell Reports Physical Science.
Our featured speakers this week are Emma Guiberson (graduate student, Vanderbilt University, USA), Richa Gupta (graduate student, National University of Singapore, Singapore), and Lyndsay Kissell (graduate student, Portland State University, USA). The seminar will be guest-moderated by Dr. Scott Bagley from Pfizer.
LEARN MORE ABOUT THE SPEAKERS AND THEIR TALKS BELOW
Emma Guiberson (on twitter @chEMMAstry)
Biography: Emma Guiberson is a third year PhD Candidate in the Caprioli and Spraggins laboratories at Vanderbilt University using novel mass spectrometry techniques to study host pathogen interactions. She received her undergraduate degree at the University of Notre Dame with a dual major in chemistry and philosophy. In addition to research, Emma is passionate about the teaching of science and works with the Center for Teaching on campus.
Title of Talk: Discovery of Bile Acid-Associated Molecular Changes in the Murine Gastrointestinal Tract during Clostridioides difficile Infection
Abstract: Clostridioides difficile is a spore-forming pathogen that impacts half a million people annually in the U.S. alone. C. difficile infections (CDI) are characterized by the release of toxins that attack the intestinal linings, disrupting the normal gut flora. Previous C. difficile studies utilized primarily histological techniques and relied heavily on the role of the microbiome and studying the bacterial impact of CDI rather than the host. Matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) is a technology that allows for the molecular mapping of potentially thousands of analytes from a tissue’s surface in a spatially-resolved manner. In order to investigate both tissue and luminal content in the GI tract, intestinal samples were prepared in a histological “Swissroll” manner for imaging using MALDI IMS. This sample preparation allows for visualization of large sections of the GI tract simultaneously, but raises unique sample preparation considerations. Preliminary data show clear differences in the abundance and localization of primary bile acids between control and infected tissue. Primary bile acids are known germination factors for C. difficile spores, and initial data shows increased levels of the conjugated primary bile acid taurocholate (TCA, m/z 514.29) in infected species compared to noninfected samples. Liquid chromatography tandem mass spectrometry (LC-MS/MS) also shows clear quantitative differences along the GI tract between control and infected sample bile acid concentrations. Infected species show increased levels of TCA compared to both control and antibiotic-treated samples, indicating this increase is independent of antibiotic treatment despite being a major risk factor for CDI. To investigate the impact of perturbation of bile acids, additional mice were treated with cholestyramine to sequester bile acids in the intestine and determine the impact on bile acid production and bile acid pools, as well as the germination of C. difficile with access to limited germination factors, which showed stalled germination of C. difficile when treated with cholestyramine.
RICHA GUPTA (on twitter @gupta_richa1434)
Biography: Richa completed her undergraduate at Miranda House, University of Delhi, India. After that she moved to Hyderabad to pursue M.Sc. in Chemical Science from Hyderabad Central University, India. Then she moved to Delhi to take an Industrial position as Technical Consultant Chemistry in Scube Scientific, India. Richa has joined Prof. Rowan Young’s group in National University of Singapore as a graduate student in January 2018 and is working on selective C-F bond functionalization employing frustrated Lewis pair approach. In three years of PhD, she has published four peer-reviewed research articles and a patent.
Title of Talk: Selective C(sp3)-F bond Functionalization of Polyfluorocarbon Using Frustrated Lewis Pair Approach
Abstract: Mono and difluoromethyl groups are emerging as valuable motifs in organic and material chemistries and are present in several agrochemicals, synthetic materials, and pharmaceuticals. The inclusion of fluorine in such molecules is attractive to enhance solubility, chemical and biological activity, chemical resistivity, thermal stability and to act as a spectroscopic probe. Thus, direct access of these fluorine compounds is highly desirable from commercially available polyfluorides. However, polyfluorides groups generally suffer from ‘over-reaction’, where multiple C-F bonds are uncontrollably functionalized. We reported the Frustrated Lewis Pair (FLP) mediated C-F bond activation which allows selective monodefluorination via base capture of intermediate fluorocarbocations. Our methodology can be applied to aromatic, heteroaromatic and non-aromatic difluoro and trifluoromethyl groups to generate selectively fluoride substituted phosphonium, pyridinium and sulfonium salts. These salts can be further functionalized via nucleophilic substitution, Wittig coupling, photoredox alkylation, nucleophilic transfer, hydrophosphination and Suzuki coupling reactions to install a range of functional groups into the activated C-F position.
Lyndsay Kissell (on twitter @KissellLyndsay)
Biography: Lyndsay Kissell is a Ph.D. Candidate in the Lasseter Clare Research Group at Portland State University, the scientific arm of the Pacific Northwest Conservation Science Consortium. She previously attended the University of Louisville where she did research in the group of Dr. Francis Zamborini and graduated with a BA in Chemistry in 2012. Lyndsay’s graduate research employs numerous analytical spectroscopic techniques including fluorescence, electrochemical impedance, Raman, Fourier transform infrared, and fiber optic reflectance spectroscopies to answer questions related to cultural heritage materials.
Title of Talk: Development of a microsampling methodology coupled with surfaced enhanced Raman spectroscopy for elucidation of organic colorants on works of art on paper
Abstract: Due to incomplete written records of the production of historical artworks, there are often questions surrounding the materials used on a specific object. The understanding and identification of these materials is essential to the successful conservation of historical objects. Definitive chemical analysis of natural colorants is necessary for this understanding. Typically, colorant materials are particularly challenging to identify due to their relatively low abundance and the frequent chemical changes they have undergone as a result of environmental exposure. In the intricate nishiki-e (brocade) prints of the 18th century Japan, natural colorants were bound in a large excess of glue and printed in a thin layer on the finest quality Hosho paper. Of particular interest are the wide range of pink, red, and orange colors that appear in these works. Historically available organic red colorants are safflower, sappan, or madder inks, and recent works have suggested the contemporaneous usage of those three and mixing of colorants to produce a variety of hues. This project aimed to identify unknown colorants on nishiki-e prints by surface enhanced Raman spectroscopic (SERS) analysis of microsamples. First, we developed microsampling tool that utilized a small hydrogel surface in brief contact with the print to mechanically collect colorant particulate, on the order of 5-10 µm in size, without the use of harsh solvents or extended sampling times. The small samples retained on the hydrogel surface were then exposed to silver nanoparticles to allow for a plasmon resonance effect, and SERS was performed. SERS is advantageous as compared to other analytical techniques due to its superior sensitivity to analyte molecules, suppression of interfering molecular fluorescence, and unique chemical fingerprints resulting from the specific molecular structures being probed. There are, however, existing challenges such as dependence of molecule orientation in space and proximity to the SERS probe which results in an unavoidable variance in response. Additionally, since historic inks are not perfectly homogenous and the Raman spot sizes being sampled are small, many replicate measurements are required in order to produce a representative sample of spectral characteristics. These challenges can be addressed through compilation and analysis of laboratory produced standards, including accelerated aging techniques aiming to reproduce molecular (and in turn spectral changes due to exposure. Using this library of standards coupled with a genetic algorithm for matching, successful identification of organic red colorants was demonstrated. This methodology has been applied to works attributed to Suzuki Harunobu in the collection of the Portland Art Museum and was shown to both elucidate mixtures of red colorants and to identify colorants in areas of significant fading or color shifting. The results of this study will allow collections care personnel to better understand the use of individual colorants and colorant mixtures in late 18th century Japanese printmaking.
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