Seminars & Events

Throughout the academic year, the department hosts several seminars whose presenters range from department graduate students to internationally renowned professors and scientists. The calendar below includes all of our department seminars and events. It is updated frequently with titles and abstracts — you can subscribe using Google Calendar by clicking the "+GoogleCalendar" button in the lower right. 

Seminars

Friday Colloquium Series

Faculty members and graduate students invite professors from other institutions throughout the country and the world to speak at Brown on a Friday afternoon. Friday colloquiua topics span the various fields of chemistry represented by the department. Sometimes, a colloquium seminar is hosted jointly with another department or institute, such as IMNI, the Institute for Molecular and Nanoscale Innovation. Friday afternoons, 4:00pm - 5:00pm, MacMillan Hall 115. Refreshments served at 3:45pm.

Organic Chemistry Seminars

Organic chemistry graduate students are required to give at least two seminars. The first is a literature seminar on a topic of recent interest, and the second is the candidate's thesis research. Invited guests frequently present their research at Organic Seminars as well. Tuesday afternoons, 12:00pm - 1:00pm.

Inorganic Chemistry Seminars

Inorganic chemistry graduate students are expected to present one seminar per year on their own research or on another topic of current interest in inorganic chemistry. Research associates, faculty and invited guests often present inorganic seminars as well. Thursday afternoons, 12:00pm - 1:00pm.

Physical Chemistry Tea Sessions

Physical chemistry graduate students are expected to present one seminar per year. Topics covered include the graduate students' topics of interest with regard to current research, as well as their own research. Thursday afternoons, 3:00pm - 4:00pm.

A recap of 2019-2020 Chemistry Department events!

Upcoming Events

  • Title  Protein hydration and dynamics seen by fluorescence: studies on haloalkane-dehalogenases

    Abstract: The hydration and mobility of proteins are believed to profoundly affect their function1. However, only a few approaches for monitoring these characteristics within the relevant protein regions are available. Here we describe two fluorescence methods forsite-specific analysis of the extent of hydration and degree of the mobility in enzyme Haloalkane Dehalogenase. The first approach is based on recording “timed dependent fluorescence shift”(TDFS)2 placing the dye in the tunnel mouth of thisenzyme3,4. In a second approach, environment sensitive coumarin dye is inserted in the selected region employing the technology of the“unnatural aminoacid”5. By means of the steady state spectroscopy the degree of hydration can be determined including the presence of ‘structured water’6. Finally, the„gating“ dynamics of the enzymes can be traced by following the photoinduced electron transfer (PET) between the selected tryprophan and properly positioned fluorescence dye7. Both the hydration and dynamics monitored within the biologically relevant regions of the dehalogenase enzymes is then compared with their enzyme kinetics of various mutants, which can bring the deeper insight into the functioning of these enzymes.

    References:

    (1) Levy,Y.; Onuchic, J. N. Annu. Rev. Biophys.Biomolec. Struct.2006, 35, 389.

    (2) Jesenská,A., J. Sýkora, A. Olżyńska, J. Brezovský, Z. Zdráhal, J. Damborský, M. Hof. J. Am.Chem. Soc., 2009. 131(2): p. 494-501

    (3) Amaro, M.;Brezovsky, J.; Kovacova, S.; Maier, L.; Chaoupkova, R.; Sykora, J.; Paruch, K.;Damborsky, J.; Hof, M. J. Phys. Chem. B2013, 117, 7898.

    (4) Sykora, J.; Brezovsky, J.; Koudelakova,T.; Lahoda, M.; Fortova, A.; Chernovets, T.; Chaloupkova, R.; Stepankova, V.;Prokop, Z.; Kuta Smatanova, I.; Hof, M.; Damborsky, J. Nat. Chem. Biol.2014, 10, 428.

    (5) Summerer, D.; Chen, S.; Wu, N.; Deiters,A.; Chin, J. W.; Schultz, P. G. Proc.Natl. Acad. Sci. U. S. A.2006, 103, 9785.

    (6) Amaro, M.; Brezovsky, J.; Kovacova, S.;Sykora, J.; Bednar, D.; Nemec, V.; Liskova, V.; Kurumbang, N. P.; Beerens, K.;Chaloupkova, R.; Paruch, K.; Hof, M.; Damborsky, J. J. Am. Chem. Soc.2015, 137, 4988.

    (7) Kokkonen P, Sykora J, Prokop Z, Ghose A, Bednar D, Amaro M,Beerens K, Bidmanova S, Slanska M, Brezovsky J, Damborsky J, Hof M. J. Am. Chem. Soc., 2018 140 51 17999-18008

     

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  • Title: Combining Theory and Experiment to Develop Selective Three-Component
    Fe-Catalyzed Radical Cascades/Cross-Couplings

    Abstract: Despite advances in high-throughput screening methods leading to a surge in the discovery of catalytic reactions, our knowledge of the molecular-level interactions in the rate- and selectivity-determining steps of catalytic reactions, especially those involving highly unstable and reactive open-shell intermediates, is rudimentary. These knowledge gaps prevent control, suppression or enhancement, of competing reaction channels that can drive development of unprecedented catalytic reactions.
    In this talk, I will focus on our use of high-level quantum mechanical calculations, rigorously calibrated against experimental data, to interrogate the mechanisms and to guide the development of new catalysts and reagents for currently sluggish or unselective reactions. In particular, I will focus on our use of combined experimental and computational tools to understand and develop new (asymmetric) three-component iron-catalyzed radical cascade/cross-coupling reactions.

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  • Title: Amphiphilic Block Copolymer Synthesis via Metal-organic Insertion Light initiated Radical (MILRad) polymerization using Pd(II)diimine complexes

    Abstract: 

    Polyolefin-polar block copolymers are one of the most sought after structures due to their properties that arise from their microstructure and boost the performance of already known plastics. The limited availability is viewed as the bottleneck of future plastic development. A newly developed technique – MILRad polymerization- is an orthogonal platform which combines two polymerization techniques, providing a single approach. Coordination insertion and radical polymerization are bridged through the use of cationic diimine Pd(II) complexes. The presentation will illustrate how triggering homolysis in chain-walking catalysts with external stimuli can finally bridge the gap in metal-organic catalysis to access amphiphilic block copolymers. Detailed mechanistic studies have shown that the key for a successful formation of these blocks is based on the ring-opening of a photochemically inactive chelate with ligands such as ACN while avoiding chain transfer. Subsequent chain-walking to the carbon alpha to the carbonyl group yields a bond which is susceptible to bond homolysis by blue light. The generated polyolefin radicals are then capable of free radical polymerization with acrylates. The lecture will also teach about analytical tools which are necessary to elucidate key compounds and how the mechanistic studies have led to the broadening of the scope of available block copolymer structures. Some other aspects of the lecture will be dedicated towards the tuning of the individual blocks and investigations of the influence of ligands and Lewis acids on isomerization and polymerization.

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  • Rhodium-Group 13 Catalysts for Challenging Hydrodefluorination Reactions

    We have been developing heterobimetallic complexes that combine a reactive transition metal with a main group metal ion in a bonded unit. The synergistic combination of the different metals is hypothesized to create hybrid “metals” that may exhibit unique properties and reactivities. Rhodium catalysts that feature a Lewis acidic group 13 center were recently discovered to catalyze hydrodefluorination of challenging C-F substrates. We will present the catalyst optimization, substrate scope, and mechanistic insights for these Rh-group 13 catalysts.

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  • Title:  Theoretical and experimental advances in ultrafast x-ray scattering 

    Abstract: Molecular structure is a key concept and the exponential growth of entries in the Cambridge Structural Database and the Protein Data Bank is testament to its importance. New X-ray Free-Electron Lasers (XFELs) are making it possible to determine not only structure, but also structural dynamics – i.e. the dynamic changes in atomic positions that underpin molecular function. It turns out that ultrafast x-ray scattering provides a remarkable window onto ultrafast photochemical and photophysical dynamics. We will review recent experimental advances that include the mapping of atomic motions during a chemical reaction,1 the nascent science of excited-state structure determination,2 and observation of nearly-instant changes in electron density upon photoexcitation.3 We will investigate how scattering cross-sections, crucial for the interpretation of experiments, can be calculated and the physical insights gained from different types of scattering.4-6 Strikingly, the distinction between structural dynamics on one hand and spectroscopy on the other becomes increasingly blurred. Finally, we will look at future directions that may include the characterization of electronic states and measurement of coherence using x-ray scattering.6

     

    References

    1M. P. Minitti et al. Physical Review Letters 114 255501 (2015)

    2B. Stankus et al. Nature Chemistry 11 716 (2019)

    3H.W. Yong et al. Nature Communications 11 2157 (2020)

    4A. Kirrander et al. Journal of Chemical Theory and Computations 12 957 (2016)

    5N. Zotev et al. Journal of Chemical Theory and Computations 16 2594 (2020)

    6M. Simmermacher et al. Physical Review Letters 122 073003 (2019)

     

    http://www.kirrander.chem.ed.ac.uk

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  • Title: Beyond Watson & Crick: Roles for the DNA Quadruple Helix from Aging to Zika

    Abstract: The DNA double helix is often considered a static repository of genetic information like dusty old books on a library shelf. We now know that the Watson-Crick duplex, first drawn in 1953, undergoes considerable changes on a daily basis, both (a) alterations in the four base structures (the 4 letters of the code), and (b) unwinding of the duplex, not just to single strands but also refolding to quadruplexes, 4-stranded structures that punctuate DNA. These quadruple helices are common at the telomere ends of chromosomes where they play roles in aging and cancer, and they are also common in regulatory regions of genes that impact the timing of gene expression. We recently found that the RNA comprising the Zika virus genome is rich in G-quadruplex sequences as well. This lecture will introduce G and C-quadruplex structures and discuss important areas of biomedical research stemming from these non-canonical structures. 

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  • Title:  Free Radical Oxidation of Guanine—Mutagenic or Epigenetic

    Abstract:  ‘Free radicals’ and ‘oxidative stress’ sound like bad news in the context of the precious DNA constituting our genome, but yet we live and breathe in an atmosphere of O2, a diradical. This lecture will present the organic chemistry of guanine (G) oxidation to other heterocycles such as 8-oxoguanine (OG) and spirodihydantoin (Sp), followed by biophysical characterization of the impact of oxidized bases on DNA structure, then biochemical studies of how mutations arise from OG and Sp, and finally (the good news) that repair of oxidative DNA damage can alter gene expression allowing cells to respond appropriately to oxidative stress. In short—from organic chemistry to cell biology, there should be something for everyone!

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  • Title: Size- and Composition-Selected, Sub-Nano Catalysts. Preparation and Strategies for Enhanced Stability of Pt­nXm supported catalysts (X = B, Sn, Ge).

    Abstract: We have developed an approach, based on self-limiting deposition, to prepare size-selected, supported Pt cluster catalysts decorated with controlled numbers of heteroatoms of boron, tin, and germanium. The goal is to enhance stability of the sub-nano clusters, supported on alumina or silica, against thermal sintering and coking in high temperature hydrocarbon dehydrogenation reactions. It is found that all three alloying/doping elements do tend to enhance stability and suppress coking to different degrees, but the mechanism of coking reduction is quite different. A combination of experiments and detailed DFT calculations by the group of Anastassia Alexandrova are used to probe the varying effects.

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  • Natural products continue to inspire and serve as the basis of new medicines. They also provide intricate problems that expose limitations in the strategies and methods employed in chemical synthesis. Several strategies and methods that have been developed in our laboratory and applied to the syntheses of architecturally complex diterpenoid alkaloids, indole alkaloids, and several Lycopodium alkaloids, will be discussed. In addition, new ways to employ C–C bond cleavage in synthesis will be presented (i.e., break-it-to-make-it strategies).

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