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Lectures & Events
Monday
25
February
Dolfi and Lola Ebner Auditorium
11:00
"Augmenting biology through de novo protein design"
Prof. Dek Woolfson
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"Augmenting biology through de novo protein design"
Protein design—i.e., the construction of entirely new protein sequences that fold into prescribed structures—has come of age: it is possible now to generate a wide variety stable protein folds from scratch using rational and/or computational approaches. A challenge for the field is to move from what have been largely in vitro exercises to protein design in living cells and, in so doing, to augment biology. This talk will illustrate what is currently possible in this nascent field using de novo -helical coiled-coil peptides as building blocks.1 Coiled coils are bundles of 2 or more helices that wrap around each other to form rope-like structures. They are one of the dominant structures that direct natural protein-protein interactions. Our understanding of coiled coils provides a strong basis for building new proteins from the bottom up. The first part of this talk will survey this understanding,1 our design methods,2,3 and our current “toolkit” of de novo coiled coils.4-6 Next, I will describe how the toolkit can be used to direct protein-protein interactions and build complex protein assemblies in bacterial cells. First, in collaboration with the Savery lab (Bristol), we have used homo- and hetero-oligomeric coiled coils as modules in engineered and de novo transcriptional activators and repressors.7 Secondly, with the Warren (Kent) and the Verkade (Bristol) labs, we have engineered hybrids of a de novo heterodimer and a natural component of bacterial microcompartments to form a “cytoscaffold” that permeates E. coli cells.8 This can be used to support the co-localisation of functional enzymes. University of Bristol
Tuesday
26
February
Helen and Milton A. Kimmelman Building
11:00
Chemical and Biological Physics and Organic Chemistry Seminar
Prof Michael J. Therien
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Chemical and Biological Physics and Organic Chemistry Seminar
The trion, a three-body charge-exciton bound state, offers unique opportunities to simultaneously manipulate charge, spin and excitation in one-dimensional single-walled carbon nanotubes (SWNTs) at room temperature. Effective exploitation of trion quasiparticles requires fundamental insight into their creation and decay dynamics. Such knowledge, however, remains elusive for SWNT trion states, due to the electronic and morphological heterogeneity of commonly interrogated SWNT samples, and the fact that transient spectroscopic signals uniquely associated with the trion state have not been identified. Here length-sorted SWNTs and precisely controlled charge carrier-doping densities are used to determine trion dynamics using femtosecond pump-probe spectroscopy. Identification of the trion transient absorptive hallmark enables us to demonstrate that trions (i) derive from a precursor excitonic state, (ii) are produced via migration of excitons to stationary hole-polaron sites, and (iii) decay in a first-order manner. Importantly, under appropriate carrier-doping densities, exciton-to-trion conversion in SWNTs can approach 100% at ambient temperature. We further show that ultrafast pump-probe spectroscopy, coupled with these fundamental insights into trion formation and decay dynamics, enables a straightforward approach for quantitatively evaluating the extent of optically-driven free carrier generation (FCG) in SWNTs: this work provides fundamental new insights into how quantum yields for optically-driven FCG [Φ(Enn → h+ + e−)] in SWNTs may be modulated as functions of the optical excitation energy and medium dielectric strength. Collectively, these findings open up new possibilities for exploiting trions in SWNT optoelectronics, ranging from photovoltaics, photodetectors, to spintronics. Duke University
Monday
11
March
Max and Lillian Candiotty Building
11:00
"Supramolecular Assembly with Mechanical Action"
Prof. Myongsoo Lee
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"Supramolecular Assembly with Mechanical Action"
In this symposium, I will introduce our recent results how to construct dynamic self-assembled nanostructures exhibiting switchable functions, inspired by life systems. For example, synthetic tubular pores are able to undergo open-closed gating driven by an external signal, which function as an artificial enzyme. When self-assembled tubules embed DNA inside the hollow cavities, the DNA-coat assembly undergoes collective motion in helicity switching. In the case of toroid assembly, the static toroids are able to undergo spontaneous helical growth when they switch into out-of-equilibrium state. The helical growing drives actuation of spherical vesicles into tubular vesicles, reminiscent of microtubles. Moving from 1-D to 2-D structures, the internal pores are able to form chiral interior which selectively capture only one enantiomer in racemic solution with pumping action. I will discuss recently discovered these results with their complex functions. Jilin University
Monday
18
March
Camelia Botnar Building
11:00
"Smart Interfacial Materials: from Super-Wettability to Binary Cooperative Complementary Systems"
Prof. Lei Jiang
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"Smart Interfacial Materials: from Super-Wettability to Binary Cooperative Complementary Systems"
Beihang University
Thursday
04
April
Perlman Chemical Sciences Building
11:00
Chemical and Biological Physics Guest Seminar
Dr. Thorsten Auth
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Chemical and Biological Physics Guest Seminar
The cytoskeleton is a highly dynamic three-dimensional network of polar filamentous proteins and molecular motors. It provides structural stability for biological cells and it also generates and transmits mechanical forces. For example, in mesenchymal cell motility actin filaments polymerize at their plus ends, which exerts pushing forces on the cell membrane. Here, we present a generic two-dimensional model for an active vesicle, where self-propelled filaments attached to semiflexible polymer rings form mechanosensitive self-propelled agents. We find universal correlations between shape and motility. To probe the internal dynamics of flexocytes, we study the effect of substrate patterning on their mechanical response. The active vesicles reproduce experimentally observed shapes and motility patterns of biological cells. They assume circular, keratocyte-like, and neutrophil-like shapes and show both persistent random and circling motion. Interestingly, explicit pulling forces only are sufficient to reproduce this cell-like behavior. Also for the reflection of the vesicles at walls and the deflection of their trajectories at friction interfaces we find parallels to the behavior of biological cells. Our model may thus serve as a filament-based, minimal model for cell motility. Forschungszentrum Julich
Monday
15
April
Max and Lillian Candiotty Building
11:00
Thursday
30
May
Perlman Chemical Sciences Building
10:00
Chemical and Biological Physics Guest Seminar
Dr. Alexandre Kabla
[Info]