Integrated Calendar

Imaging Flow Cytometry combines speed, sensitivity, and phenotyping abilities found in flow cytometry with the detailed imagery and functional insight of microscopy, for an extensive range of novel applications. It allows quantitating cellular morphology and the intensity and location of fluorescent probes on, in, or between cells, even in rare sub-populations and highly heterogeneous samples. The wide range of applications used include studying intracellular localization, shape changes and morphology, co-localization, nuclear translocation, cell signaling, T cell – APC interactions, DNA damage and repair, cell death and apoptosis, phagocytosis and internalization, FISH, vesicle trafficking, and many others.

Although animals and humans move daily through complex three-dimensional (3D) environments, practically nothing is known about the encoding of 3D head direction in the brain. Moreover, very little is known about how neural circuits represent the location or direction of spatial goals – which is essential for goal-directed navigation.
In the first part of the talk, I will present the first neural recordings of 3D head-direction cells from the hippocampal formation of flying and crawling bats, and will describe the functional organization and the surprising properties of these neurons. By using the head-direction system as an example, I will also discuss several theoretical considerations for the existence of both pure and conjunctive population codes in the brain.
In the second part, I will present our new findings that suggest the existence of goal-direction and goal-proximity signals in the bat hippocampus – a vectorial representation that could support goal-directed navigation.

KcsA has been extensively studied as a paradigm of structure-function relations in potassium channels. Structure determination of KcsA and several other related channels has revealed many of the molecular features of these membrane-embedded proteins. In this seminar I hope to illuminate certain unexplored aspects of potassium channel behavior using biomolecular NMR. Membrane proteins are notoriously challenging for structural study due to the need to stabilize them in a membrane-mimicking detergent- or lipid-based environment. Thus, the first necessary breakthrough was establishing that NMR is capable of addressing this large molecular assembly estimated at 120-170 kDa depending on choice of detergent. This achievement has laid the foundation for further investigations of KcsA activity, of which I will present two, (i) an under-appreciated pH-dependent oligomerization domain, and (ii) toxin inhibition of channel conduction. Together these examples demonstrate the versatility of solution NMR in uncovering the molecular mechanisms behind biological function involving protein structure and flexibility.