NOBCChE Collaborative is proud to announce our Faculty Seminar Series, highlighting faculty’s scientific expertise and covering a wide range of topics. Each seminar is free and open to the public, but registration is required.  Use the button above to register.

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October 28th - Psaras McGrier, PhD

Title: Synthesis and Design of Functional Covalent Organic Frameworks

Abstract: Covalent organic frameworks (COFs) are an advanced class of crystalline porous polymers that are composed of light elements (C, H, O, N, and B) linked via strong covalent bonds. COFs are generally constructed by using reversible bond forming reactions to yield crystalline materials with high surface areas, low densities, and high thermal stabilities. These features make COFs useful for carbon capture, gas storage, and sensory applications. This lecture will discuss employing a bottom-up approach to create novel functional COFs that can bind small metal cations (e.g., Li, Ca, etc.), and some low-oxidation state transition metals (e.g., Ni(0), Co(II), Fe(II), etc.). The prospect of utilizing these COFs for applications related to gas separations, catalysis, and energy storage will be highlighted.

November 18th - Peter Chen, PhD

Title: TBD

Abstract: TBD

December 16th - Gabriela Schlau-Cohen, PhD

Title: Why don't plants get sunburn? 

Abstract: In green plants, chlorophyll-containing proteins known as light-harvesting complexes (LHCs) capture solar energy and feed it to downstream molecular machinery. Under high light (i.e., sunny days), excess absorbed energy can cause damage. Thus, LHCs have evolved a feedback loop that triggers photoprotective energy dissipation, solving the so-called “intermittency problem” in solar energy. A long-standing proposal has been that conformational changes of the LHCs activate dissipative photophysical pathways among the chlorophyll. First, we use single-molecule spectroscopy to identify the conformational states of the LHCs, uncovering parallel conformational dynamics that regulate fast and slow changes in sunlight. Second, we use 2D electronic spectroscopy to map out the corresponding photophysics, revealing dissipative chlorophyll-to-carotenoid energy transfer, a hypothesized yet previously unobserved pathway. Collectively, these multi-timescale measurements elucidate the multi-timescale dynamics of photoprotection.

January 27th - Mary Jo Ondrechen, PhD

Title: How do enzymes impart catalytic superpowers to amino acids?

Abstract: Enzymes catalyze reactions under mild conditions that would otherwise require extreme conditions such as high temperature or strong acidity or basicity. To achieve this, enzymes often impart reactive chemical properties to amino acid sidechains that are far less reactive in the absence of the protein environment. In the enzymatic environment, active site amino acid sidechains that are weak Brønsted acids or bases in a small peptide can transform into a strong acid or base. The primary amine side chain of lysine, which would normally be protonated at neutral pH, can be deprotonated to serve as a nucleophile. We present a set of 20 enzymes that represent all six major EC classes and a variety of fold types for which experimental studies of the catalytic residues' mechanistic roles have been reported in the literature. For these 20 enzymes the computed electrostatic and proton transfer properties are investigated. The catalytic aspartates and glutamates are shown to be strongly coupled to at least one other aspartate or glutamate residue, and frequently to multiple other carboxylate residues, with intrinsic pKa differences less than ~1 pH unit. These catalytic acidic residues are sometimes coupled to a histidine, wherein the intrinsic pKa of the acid is higher than that of the His. Anion-forming residues, Tyr or Cys, with intrinsic pKa higher than that of the lysine, are found strongly coupled to all catalytic lysines in the set. Some catalytic lysines are also coupled to other lysines with intrinsic pKas within ~1 pH unit. Some basic principles about the design of enzyme active sites are discussed. The interactions described here provide important clues about how side chain functional groups that are weak Brønsted acids or bases for the free amino acid can become strong acids, bases, or nucleophiles in the enzymatic environment. Supported by NSF CHE-1905214. 

February 24th - Stephen Leffler Buchwald, PhD

Title: Palladium-Catalyzed Carbon-Heteroatom Bond Formation

Description: The history of the development of Pd-Catalyzed Carbon-Heteroatom Bond Formation as well as a description of the basic mechanistic considerations, recent examples and an application to the modification of proteins will be described.

March 31st - Christine Thomas, PhD

Title:  Incorporating Metal-Ligand and Metal-Metal Cooperativity into Catalysis

Abstract: The formation and cleavage of chemical bonds in catalytic reactions relies on accessible two-electron redox processes that are often challenging for base metals such as first row and early transition metals. Metal-ligand and metal-metal cooperativity provide a potential solution to this challenge by enabling heterolytic bond cleavage processes and/or facilitating redox processes. Both strategies will be discussed, showcasing the many ways that metal-ligand and bimetallic cooperativity can operate and the methods by which cooperativity can be built into catalyst design. A tridentate pincer ligand featuring a reactive N-heterocyclic phosphido fragment is found to be both redox active and an active participant in bond activation across the metal-phosphide bond, with catalytic applications in alkene hydroboration. A tetradentate bis(amido)bis(phosphide) ligand has been coordinated to iron and it has been shown that the resulting complex can activate two σ bonds across the two iron-amide bonds in the molecule without requiring a change in the formal metal oxidation state. In the context of metal-metal cooperativity, phosphinoamide-linked early/late heterobimetallic frameworks have been shown to support metal-metal multiple bonds and facilitate redox processes across a broad range of metal-metal combinations and the resulting complexes have been shown to activate small molecules and catalyze organic transformations.

April 28th - Daniel Suess, PhD

Title: The Ins and Outs of the Graduate School Admissions Process