December 1, 2020 Webinar Speakers

Our second JAWSChem Webinar will take place via the internet on Tuesday December 1st, 2020 at 8pm EST/1am GMT (Dec. 2). Please note that every week the seminar time will alternate to accommodate presenters and attendees from different time zones. Sign up on our mailing list to receive the zoom link!

Our featured speakers this week are Thomas Cross (undergraduate student; University of California, Irvine; Irvine, USA), Kamran Amin (graduate student; National Center for Nanoscience and Technology, Chinese Academy of Sciences, Beijing), and Dr. Dana Westmoreland (postdoctoral researcher; MIT, USA).


THOMAS CROSS (on twitter @dz_lmnz)

Biography: Thomas Cross is a senior undergraduate researcher in Prof. Rachel Martin’s Chemical Biology lab at the University of California, Irvine. Since joining the research scene in early March 2020, he has focused on understanding the mutational landscape of the SARS-CoV-2 main protease, publishing a first-author paper in Biochemistry in September 2020. He’s currently applying to graduate schools for a Ph.D. in Chemistry, with a focus on Computational Methods.

Title of Talk: Sequence characterization and molecular modeling of clinically relevant variants of the SARS-CoV-2 main protease

Abstract: The SARS-CoV-2 main protease (Mpro) is essential to viral replication and cleaves highly specific substrate sequences, making it an obvious target for inhibitor design. However, as for any virus, SARS-CoV-2 is subject to constant neutral drift and selection pressure, with new Mpro mutations arising over time. Identification and structural characterization of Mpro variants is thus critical for robust inhibitor design. Here we report sequence analysis, structure predictions, and molecular modeling for seventy-nine Mpro variants, constituting all clinically observed mutations in this protein as of April 29, 2020. Residue substitution is widely distributed, with some tendency toward larger and more hydro- phobic residues. Modeling and protein structure network analysis suggest differences in cohesion and active site flexibility, revealing patterns in viral evolution that have relevance for drug discovery.

KAMRAN AMIN (on twitter @kamraniat)

Biography: Kamran Amni is a CAS-TWAS president fellow for PhD at National Center for Nanoscience and Technology, Chinese Academy of Sciences under the supervision of Professor Wei Zhixiang. His research mainly focusses on synthesis of novel organic materials and fabrication of flexible devices for energy storage applications. He is also the president of International Students Association of NCNST. He was awarded with UCAS excellent student of the year award for the year 2018 and NCNST director award for the year 2017, 2018, 2019 and 2020 for his academic excellence. He has published first author paper in Advanced Materials and Macromolecular Rapid Communication and coauthor paper in Nature Communication, Nanoscale, Advanced Materials interfaces etc.

Title of Talk: Rational Material Design for Ultrafast Rechargeable Organic Lithium Ion Batteries

Abstract: It is very important to design the devices capable of fast charging and long life for commercial application. But fabrication of lithium ion batteries with high power and energy density is quite challenging. In recent years, a lot of work has been done to improve the rate performance and life of LIBs. We believe that better understanding of the kinetics limitations for faster batteries can guide us to design materials for ultrafast long-life batteries. To prove this, we started exploring redox active conjugated microporous polymers as an electrode for LIBs. In these systems interconnected microporous network can facilitate faster diffusion of ions. Large surface area can make the deep buried active sites accessible on or near to surface and conductivity can be improved by making composite with suitable conductive media. Combining all these effects together we were able to develop a lithium ion cell that can be charged as fast as 66C with significant capacity retention. Also, we found that cell can be charge and discharge for 3000 cycles without any capacity loss. Through carefully investigation we revealed that high surface area, porosity, and conductivity lead to energy storage process through surface or near surface pseudo capacitive energy storage mechanism which is usually found in supercapacitor and is faster than batteries. This study shows how we can transfer kinetically slow, diffusion controlled faradic reactions in batteries to faster pseudo capacitive reactions by rationally designing the materials. We expect that this will pave the way for high power batteries with high energy density.

DR. DANA WESTMORELAND (on twitter @DEWestmoreland)

Biography: Dr. Westmoreland received her PhD from Northwestern University, where she worked for Prof. Emily Weiss investigating the mechanisms by which organic capping ligands modify the absorption and emission energies of colloidal quantum dots. As a result of her graduate work, Dr. Westmoreland is interested in the chemical mechanisms of dynamic solution-phase systems. Due to this interest, Dr. Westmoreland recently began a postdoctoral appointment at MIT, where she works for Prof. Catherine Drennan investigating the structure-function relationships of bacterial metalloenzymes.

Title of Talk: N-Heterocyclic Carbene Ligands Delocalize the Exciton of CdSe Quantum Dots

Abstract: ReExciton-delocalization in semiconductor quantum dots (QDs), which arises from the mixing of inorganic and organic states at the QD-ligand interface, enables enhanced charge carrier extraction from QDs for either photocatalysis or charge transport in films, and is an attractive route towards achieving ultrafast and dynamic colorimetric sensing in biological systems. Previous demonstrations of exciton-delocalization in QDs used ligands that contain thiolate binding groups, like thiophenol and phenyldithiocarbamate. Thiolate-based exciton delocalizing ligands, however, suffer from several disadvantages, including i) instability due to disulfide formation upon oxidation, ii) quenching of the emission of the QD and therefore low photoluminescence quantum yields, and iii) in the case of phenyldithiocarbamates in particular, the spontaneous degradation of the ligand when unbound to a QD surface into multiple degradation products in solution. This work describes a new class of exciton-delocalizing ligands, N-heterocyclic carbenes (NHCs). We perform post-synthetic ligand exchange with three 1,3-methyl-4,5-disubsituted imidazolylidene NHC derivatives and use a combination of ground state optical spectroscopies and nuclear magnetic resonance spectroscopy to characterize the magnitude of delocalization for each NHC derivative. We show that NHC ligands do not significantly quench the QD emission up to optical band gap shifts of 106 meV, and that their exciton-delocalizing effect is fully reversible upon desorption of the NHC ligands from the QD surface. We correlate the magnitude of the exciton-delocalizing ability for each derivative with its π acidity, and discuss the potential of NHC-capped QDs as dynamic sensors.

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