Integrated Calendar

Characterization of the overall topology and inter-subunit contacts of protein complexes, and their assembly/disassembly and unfolding pathways, is critical because protein complexes regulate key biological processes, including processes important in understanding and controlling disease. Tools to address structural biology problems continue to improve. Native mass spectrometry (nMS) and associated technologies such as ion mobility are becoming an increasingly important component of the structural biology toolbox. When the mass spectrometry approach is used early or mid-course in a structural characterization project, it can provide answers quickly using small sample amounts and samples that are not fully purified. Integration of sample preparation/purification with effective dissociation methods (e.g., surface-induced dissociation), ion mobility, and computational approaches provide a MS workflow that can be enabling in biochemical, synthetic biology, and systems biology approaches. Native MS can determine whether the complex of interest exists in a single or in multiple oligomeric states and can provide characterization of topology/intersubunit connectivity, and other structural features. Beyond its strengths as a stand-alone tool, nMS can also guide and/or be integrated with other structural biology approaches such as NMR, X-ray crystallography, and cryoEM.

Integrating information from different sensory systems is essential for faithful representation of the external world. Different senses represent different aspects of the surrounding world. They operate at different time scales, and integrate information presented at different distances from the body. For example, tactile sensation enables sensing very proximal objects, whereas the auditory system allows us to sense very distant objects as well. In many instances, however, we simultaneously sense the same object using two or more modalities. This occurs, for example, when we use a hammer. In this case, we watch our movements and get tactile and auditory feedbacks for fine-tuning and precision. In this work, we are interested in revealing how the primary sensory cortices of both the auditory and somatosensory vibrissa systems integrate information they receive from a given source, in this case when the animal touches an object by moving its whiskers. We ask if such touch signals can produce audible signals that can be perceived by the auditory system. Towards this aim, we severed the infraorbital nerve (ION) of mice to eliminate somatosensory sensation going from the whiskers and the pad to the cortex. We then head fixed the mice and presented a piece of aluminum foil to the whiskers. Our preliminary results show that when the mouse whisked against the object it produced audible sound as we examined by using highly sensitive ultrasonic microphones. This sound differs from the environment both in amplitude and frequency range. Many neurons in the primary auditory cortex responded to the sound generated by the contact of the whiskers with the object. We propose that mice can use the two sensory systems in a complimentary manner in order to produce comprehensive representation of their proximal environment, perhaps similar to the way cane is used by visually impaired people. To demonstrate if the animal can use this auditory sensation, we will train head fixed and ION severed mice to respond to objects that produce sound by the whiskers’ touch. Showing that the auditory sensation can be relevant for the animal in identifying objects.

Low dimensional materials offer very interesting material and physical properties due to reduced dimensionality. Nowadays, mostly 2D materials are the focus of attention. However, 1D systems often show far more exotic behavior, such as Tomanaga-Luttinger liquid, Peierls distortion, etc.. In this talk, we will present different classes of 1D molecular chains formed on metallic surfaces by on-surface synthesis, which physical and chemical properties were investigated by low temperature UHV scanning probe microscopy supported by theoretical analysis.
First, we will introduce a novel strategy to synthesize [1] a new class of intrinsically quasi-metallic one-dimensional (1D) -conjugated polymers featuring topologically non-trivial quantum states. Furthermore, we unveiled the fundamental relation between quantum topology, -conjugation and metallicity of polymers [2]. Thus, we will make a connection between two distinct worlds of topological band theory (condensed matter physics) and -conjugation polymer science (chemistry). We strongly believe this may stimulate new ways of thinking towards a design of novel organic quantum materials.
In second part, we will demonstrate unusual mechanical and electronic properties of hydrogen bonded chains formed on a metallic surface driven by quantum nuclaar effects within the chain. We will show, that the concerted proton tunneling not only enhances the mechanical stability of the chain, but it also gives rise to new in-band gap electronics states localized at the ends of the chain.

[1] A. Grande-Sanchez et al. Angew. Chem. Int. Ed. 131, 6631-6635 (2019).
[2] B. Cierra et al arXiv preprint arXiv:1911.05514

A fundamental problem in neuroscience is to elucidate the relationship between neuronal network anatomy and its functional dynamics. The nematode worm C. elegans is an ideal model to study these problems. Its nervous system has just 302 neurons and all synaptic connections between them have been fully mapped. Using a large-scale Ca2+-imaging approach, we previously discovered nervous system wide neuronal population dynamics in the worm that encode action commands. These dynamics feature various network attractor states during which neurons coordinate and synchronize their activities, thereby providing functional interaction maps. In this talk, I will discuss unpublished work where we combine graph-theoretical and experimental approaches to understand which anatomical features in network connectivity relate to these functional dynamics and interactions between neurons.

Less is more! By using extremely low power refocusing π pulses in echo train sequences the coherence lifetime, T2, of the central transition of half-integer quadrupolar nuclei can be largely extended. This effect is particularly impactful in systems dilute in NMR active nuclei, where sources of decoherence are scarce. Crucial to this lifetime extension is the avoidance of coherence transfer to short-lived non-symmetric “killing” transitions. For 17O in polycrystalline α-quartz we were able to retain coherent magnetization for over four minutes on the transverse plane. This translates into enormous sensitivity gains for echo train acquisition after addition of the long living echoes. By combining satellite population transfer schemes with a low power CPMG on 17O in quartz, we obtain over a 1000-fold sensitivity enhancement compared to a spectrum from a free induction decay acquired at a more typical rf field strength. This enhancement allows the acquisition of a highly resolved 17O spectrum within less than one hour, despite its low natural abundance and a spin-lattice relaxation time of approximately 900 s. In this talk I will present a thorough analysis of the effects of pulse power on the echo intensity, coherence lifetime and line shape integrity. Finally, we apply this approach on various crystalline and glassy inorganic solids, including other low sensitivity nuclei, such as 33S and 45Ca, showing that it can be beneficial for a large number of systems.