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Sunday 26 January
Perlman Chemical Sciences Building
16:00
Chemical and Biological Physics Guest Seminar Dr Menahem (Hemi) Rotenberg [Info]

Chemical and Biological Physics Guest Seminar

Bioelectronics for cellular interrogation requires a minimally invasive introduction of an electrical probe to the cell. Despite tremendous developments in the field of electroceuticals in the past decades, the available technologies are still associated with major limitations. Micropipette electrodes, micro- and nanoelectrode arrays, and nano-field effect transistors allow intracellular access with extremely high spatial resolution. However, these technologies are substrate-bound, do not allow reconfigurable recording or stimulation, and lack deep tissue access, which limits their use to in vitro application. Optogenetics can offer numerous mechanistic insights into cellular processes, but its spatial resolution is limited, especially for 3D tissues. Moreover, it requires genetic modification, which limits its potential therapeutic applications. In this talk, I will present my recent studies of developing new approaches for bio-interfaces using silicon micro- and nanostructures for non-genetic optical modulation, spanning from sub cellular interrogation with extremely high spatial resolutions to whole organ optical modulation. For sub-cellular interrogation, we used tailored made photovoltaic silicon nanowires with p-i-n core-shell design. These nanowires were hybridized with living myofibroblasts and used as free sanding cell-silicon hybrids with leadless optical modulation capabilities. We used focused laser to perform intracellular electrical interrogation with high, sub-cellular spatial resolution. Thereafter, we used these hybrids to tackle a long-standing debate regarding electrical coupling between myofibroblasts and cardiomyocytes in vivo, by interrogating specific myofibroblasts within the 3D volume of the cardiac tissue. We also show this technology’s utility for neuronal investigation by hybridizing myelinating oligodendrocytes and interfacing them with neurons, allowing the investigation of calcium transients’ role in the myelination process with unprecedented spatial control. For whole organ interface we used flexible single crystalline silicon membranes, that were able to adhere and wrap around the heart and sciatic nerve. We used optical stimulation to perform heart pacing at different location on the heart, and sciatic nerve excitation. These results demonstrate potential biomedical applications for cardiac resynchronization therapy and sciatic nerve neuro-regenerative treatments. The James Franck Institute, the University of Chicago
Tuesday 28 January
Perlman Chemical Sciences Building
13:00
Chemical and Biological Physics Dept Seminar Dr Rinat Ankri [Info]

Chemical and Biological Physics Dept Seminar

Biomolecular imaging at the preclinical stage is an essential tool in various biomedical research areas such as immunology, oncology or neurology. Among all modalities available to date, optical imaging techniques play a central role, while fluorescence, in particular in the NIR region of the spectrum, provides high sensitivity and high specificity with relatively cheap instrumentation. Several whole-body optical pre-clinical NIR imaging systems are commercially available. Instruments using continuous wave (CW or time-independent) illumination allow basic small animal imaging at low cost. However, CW techniques cannot provide fluorescence lifetime contrast, which allows to probe the microenvironment and affords an increased multiplexing power. In the first part of my talk I will introduce our single photon, time-gated, phasor-based fluorescence lifetime Imaging method which circumvents limitations of conventional techniques in speed, specificity and ease of use, using fluorescent lifetime as the main contrast mechanism. In the second part of my talk I will present the tracking and multiplexing of two different cell populations, based on their different lifetimes (following their fluorescent dyes-loading). Despite major advantages of optical based NIR imaging, the reason that NIR imagers are not clinically used, is that only very few such fluorescent molecules absorb and emit in the NIR (or in the shortwave infrared, SWIR region), and even fewer have favorable biological properties (and FDA approval). I will introduce small lung cancer and dendritic cells tracking using small polyethylene glycol/phosphatidylethanolamine (PEG–PE) micelles loaded with NIR dyes (using commercial dyes as well as dyes synthesized in Prof. Sletten’s lab, UCLA Chemistry Dept.). Micelles’ endocytosis into cells affords efficient loading and exhibits strong bio stability, enabling to track the loaded cells for several days using these formulations, even though dyes were diluted by cells division (leading to reduced dye concentration within the dividing cells). Moreover, fluorescent lifetime contrast (achieved through our time-gated imaging method), significantly improved these cells detection. These advances in NIR fluorescence based imaging open up new avenues toward NIR and SWIR imaging for biomedical applications, such as tracking and monitoring cells during immunotherapy and/or drug delivery (treatment monitoring) for various types of disease. Postdoctoral Fellow, UCLA, CA
Tuesday 28 January
Helen and Milton A. Kimmelman Building
13:00
Catalyst Images, Imaging and Imagination: Visualizing Molecules and Atoms in Action on Catalytic Surfaces Prof. Bert M. Weckhuysen [Info]

Catalyst Images, Imaging and Imagination: Visualizing Molecules and Atoms in Action on Catalytic Surfaces

Catalysts play a pivotal role in modern society since they enable the production of chemicals and fuels that we rely on every day. The search for new and improved solid catalysts to speed up and access novel chemical reactions is a never-ending challenge, but has become increasingly important due to the environmental challenges that we are currently facing. For this purpose, constant improvements in synthesis methods are required in general, but more specifically, improvements in characterization methods in terms of spatiotemporal resolution is the key toward tailored catalytic reactions. In an ideal case, a real time visualization of the reactants, intermediates and reaction products on the surface of the catalyst is possible, allowing for a molecular movie of the catalytic reaction in space and time. Certain characterization techniques exist that are sensitive enough to measure the reactants at the reaction surface of the catalyst (e.g. vibrational spectroscopy). However, in order to really understand the catalytic behaviour, we need to move toward single molecules and atoms at the (sub-) nanometer scale. Improvements in this direction have already led to an increased understanding of the catalytic processes, but the combination of nanometer resolution in space and pico- to nanosecond resolution in time has remained largely elusive in the world of heterogeneous catalysis.  In this lecture, I will discuss the state-of-the-art of time- and space-resolved spectroscopy and microscopy methods for catalysis research, and discuss the movement in the field toward the visualization of individual molecules at catalyst surfaces to construct the ultimate “molecular movie of sustainability” (Figure 1). Special emphasis will be on the compatibility of operando characterization techniques with the desired reaction environment (e.g. liquid or gas phase) and what we can do to ensure the spatiotemporal resolution is not hampered by the reaction requirements of the catalytic reactions. I will touch upon a variety of techniques, ranging from (time-resolved and surface-enhanced) vibrational spectroscopy, single molecule fluorescence, scanning probe techniques combined with optical and vibrational spectroscopy, as well as X-ray spectroscopy and microscopy. Inorganic Chemistry and Catalysis, Utrecht University
Thursday 02 April
Gerhard M.J. Schmidt Lecture Hall
16:00
Ben May Center for Chemical Theory and Computation, lecture Prof. Kurt Binder [Info]

Ben May Center for Chemical Theory and Computation, lecture

Basic concepts related to interfaces between coexisting phases in thermal equilibrium can be traced back to the classic work of Gibbs, van der Waals, Landau, Cahn and Hilliard. Yet, these concepts still pose problems that are not well understood. The concept of an (intrinsic) interfacial profile is a key one for computing the interfacial free energy, but turns out to be ill-defined due to the inherent difficulties in separating the intrinsic profile from capillary wave broadening. A related problem is the failure of the idea of a free energy of homogeneous states inside the two-phase coexistence region in systems with short range forces. These difficulties can be avoided by computer simulation methods. Yet, the latter suffer from subtle finite size effects, which will be demonstrated in this lecture by extensive Monte Carlo simulations for 2D and 3D Ising models. It will be shown that one can understand them in terms of fluctuation phenomena associated with interfaces, such as translational degrees of freedoms of domains and "domain breathing". Correcting for these finite size effects, one can obtain accurate estimates for interfacial free energies, also for off-lattice models of fluids. Finally, it will be demonstrated that these concepts can be carried over to the study of curved interfaces (of droplets or bubbles, respectively), allowing the estimation of Tolman's length. Johannes Gutenberg Universitaet Mainz, Germany
Monday 18 May
Gerhard M.J. Schmidt Lecture Hall
13:00
Chemistry Colloquia Prof. Pamela Bjorkman [Info]

Chemistry Colloquia

The Division of Biology and Biological Engineering, Caltech