Department of Chemistry and Biochemistry
Physical Chemistry Seminar Series

Anastassia Alexandrova, UCLA
May 13, 2024
2:00pm in Tykeson 140
Hosted by: Alexander Batelaan

Enzymes as Molecular Capacitors

Proteins have been shown to produce intramolecular electric fields, preorganized to help enzymatic catalysis. Using IR probes placed in proteins, and measuring their Stark shift, it became possible to assess the local fields at the location of the probe, and correlate those with the reactivity. The talk will show that in fact, 3-D fields in the entirety of the active site (as opposed to a particular bond) are relevant to catalysis.

I will show that the diverging reactivity of the natural Fe-heme proteins is strongly regulated by the electric field from the protein, outside of the primary coordination sphere of the Fe. Next, I will use Protoglobin as a model, which was evolved to efficiently catalyze carbene transfer reactions, to show that what directed evolution developed is a highly strategic electric field that facilitates the reaction. The field is strongly heterogeneous and curvy, aligned opposite to the direction of the electron flow in the reaction. I will demonstrate that electric fields are dynamic. Each protein can visit several characteristic fields, only some of which are strongly catalytic, and some may promote different reaction mechanisms.

The talk will highlight several methods for field analysis, directly as a vector object, and indirectly via the scalar field of electronic charge density. These ideas and methods pertain to our understanding f how enzymes work, how they evolve toward acquiring a function, and how they should be designed to be competitive with natural enzymes.

Organic-Inorganic-Materials Chemistry Seminar Series
Department of Chemistry and Biochemistry

Grace Han, Brandeis University
May 10 2024
3:00 pm in WIL 110
Hosted by Carl Brozek

Light-Responsive Materials for a Sustainable Future: Exploring Optically-Controlled Functional Organic Systems

Light-responsive materials hold immense potential in revolutionizing various fields including solar energy conversion and storage, recyclable catalysis, single-molecule sensing, and reversible nanomaterial assembly. These materials exhibit phase transitions, changes in solubility, and nanoscale mechanical alterations triggered by external stimuli, particularly light, through molecular-level structural changes. While the photo-switching of molecules has primarily been studied in dilute solutions, understanding this process in condensed liquid or solid environments is crucial for successful real-world applications. Currently, there is a lack of fundamental knowledge regarding the interaction between light and molecules in condensed phases, as well as the impact of photomechanical switching on intermolecular interactions.

This presentation aims to elucidate the design principles behind optically-controllable materials that integrate organic photoswitches or solid-state photochromes. Extensive exploration of various photochromic core structures and functional groups has been conducted to gain insights into the structure-property relationship of these stimuli-responsive material systems. Additionally, the talk will introduce the application of photo-controlled materials in solar photon and thermal energy storage as well as sustainable catalysis.

Thermo Fisher Discovery and Impact Symposium Series
Organic/Inorganic/Materials Chemistry Seminar Series

Erdost Yildiz, Max Planck Institute for Intelligent Systems
May 3, 2024 · 3:00 pm
Beetham Family Seminar Room, Room 127 Knight Campus
Hosted by Teresa Rapp

Microscale Robotics as a Research Tool for Cellular Biophysics

The human body consists of diverse cellular environments, which leads to various therapeutic and diagnostic challenges for medical experts. While improvements and discoveries of new pharmaceutical agents, devices, and methods are ongoing, a deeper investigation of cellular biophysics is required. From this perspective, mobile microrobotics is an emerging field that revolutionizes medical applications in the diagnostics and therapeutics of various diseases.

Thanks to wireless manipulation methods with various physical forces, microrobots can mimic cellular functions, manipulate cells, and deliver pharmaceutical and physical treatment agents on a micro- scale. In this talk, I will focus on the usage of mobile microrobots to understand cellular biophysics and give some examples from different organ systems.

Organic-Inorganic-Materials Chemistry Seminar Series
Department of Chemistry and Biochemistry

Professor David A. Leigh, University of Manchester, UK
April 26, 2024
3:00 pm, 110 Willamette Hall
Hosted by Mike Haley and Darren Johnson

Much Ado About Knotting

Knots are important structural features in DNA and some proteins, and play a significant role in the physical properties of both natural and synthetic polymers.¹ Although billions of prime knots are known to mathematics, few have been realized through chemical synthesis.² Here we will discuss the latest progress from our laboratory, including the synthesis of some of the most complex molecular knots and links (catenanes) to date^3-9 and the introduction of 2D molecular weaving.¹⁰

References
[1] “Molecular knots”, Angew. Chem. Int. Ed. 56, 11166 (2017).
[2] “Knotting matters: orderly molecular entanglements”, Chem. Soc. Rev. 51, 7779 (2022).
[3] “A synthetic molecular pentafoil knot”, Nat. Chem. 4, 15 (2012).
[4] “A Star of David catenane”, Nat. Chem. 6, 978 (2014).
[5] “Allosteric initiation and regulation of catalysis with a molecular knot”, Science 352, 1555 (2016).
[6] “Braiding a molecular knot with eight crossings”, Science 355, 159 (2017).
[7] “Stereoselective synthesis of a composite knot with nine crossings”, Nat. Chem. 10, 1083 (2018).
[8] “A molecular endless (74) knot”, Nat. Chem. 13, 117 (2021).
[9] “Vernier template synthesis of molecular knots”, Science 375, 1035 (2022). [10] “Self-assembly of a layered two-dimensional molecularly woven fabric”, Nature 588, 429 (2020).

Organic-Inorganic-Materials Chemistry Seminar Series
Department of Chemistry and Biochemistry

Professor David A. Leigh, University of Manchester, UK
April 24, 2024
4:00 pm, 182 Lillis Hall
Hosted by Mike Haley and Darren Johnson

Giving Chemistry Direction

In recent years examples of synthetic molecular machines and motors¹ have been developed,² all be they primitive by biological standards. Such molecules are best designed to work through statistical mechanisms. In a manner reminiscent of Maxwell’s Demon,³ random thermal motion is rectified through ratchet mechanisms,^3-8 giving chemistry direction.

It is increasingly being recognised that similar concepts can be applied to other chemical exchange processes⁹. Ratchet mechanisms—effectively chemical engines¹⁰ in which atalysis^4,6,7 of ‘fuel’ to ‘waste’ is used to drive another chemical process—can cause directional impetus in what are otherwise stochastic systems, including reversible chemical reactions. This is ushering in a new era of non-equilibrium chemistry, providing fundamental advances in functional molecule design and the first examples of molecular robotics,^11,12 overturning existing dogma and offering fresh insights into biology and molecular nanotechnology.

For a musical introduction, see ‘Nanobot’

[1] The Nobel Prize in Chemistry 2016–Advanced Information. Nobelprize.org. Nobel Media AB 2014. Web. 6 Oct, 2016, http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2016/advanced.html.
[2] “Rise of the molecular machines”, Angew. Chem. Int. Ed. 54, 10080 (2015).
[3] “A molecular information ratchet”, Nature 445, 523 (2007).
[4] “An autonomous chemically fuelled small molecule motor”, Nature 534, 235 (2016).
[5] “Rotary and linear molecular motors driven by pulses of a chemical fuel”, Science 358, 340 (2017).
[6] “A catalysis-driven artificial molecular pump”, Nature 594, 529 (2021).
[7] “Autonomous fuelled directional rotation about a covalent single bond”, Nature 604, 80 (2022). [8] “A tape-reading molecular ratchet”, Nature 612, 78 (2022).
[9] “Design, synthesis and operation of small molecules that walk along tracks”, J. Am. Chem. Soc. 132, 16134 (2010).
[10] “Chemical engines: Driving systems away from equilibrium through catalyst reaction cycles”, Nat. Nanotechnol. 16, 1057 (2021).
[11] “Sequence-specific peptide synthesis by an artificial small-molecule machine”, Science 339, 189 (2013).
[12] “Stereodivergent synthesis with a programmable molecular machine”, Nature 549, 374 (2017).