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This presentation gives an overview on a new technology for the measurement of biomolecule interaction that is termed Microscale Thermophoresis (MST).
The term Microscale Thermophoresis refers to the directed movement of molecules in optically generated microscopic temperature gradients. This thermophoretic movement is determined by the entropy of the hydration shell around the molecules. Almost all interactions between molecules and virtually any biochemical process related to a change in size, stability and conformation of molecules alters this hydration shell and can be quantified. Such changes allow quantification of binding affinities of proteins, nucleic acids and small molecules as well as measurement of enzymatic activities with MST. In addition also functional studies of small molecule inhibitors are possible. The microscopic temperature gradient is generated by an IR-Laser, which is strongly absorbed by water. The readout method of the interaction analysis is based on fluorescence: fluorescently labeled proteins/peptides/nucleic acids can be used as well as proteins expressed with GFP/YFP/RFP. In this presentation we will describe the technical details and the benefits of the Microscale Thermophoresis technology platform. We will show examples for interaction measurements ranging from protein – ribosome, protein – protein, small molecule – receptor binding studies to experiments where the interactions between a receptor incorporated in a vesicle and soluble proteins are analyzed.

Extracellular recordings have elucidated spatial neural representations without identifying underlying microcircuits. We labeled neurons juxtacellularly in medial entorhinal cortex of freely-moving rats with a novel friction-based pipette-stabilization system. In a linear maze novel to the animals, spatial firing of superficial layer neurons was reminiscent of grid cell activity. Layer 2 stellate cells showed stronger theta-modulation than layer 3 neurons and both fired during the ascending phase of field potential theta. Deep layer neurons showed little or no activity. Layer 2 stellate cells resided in hundreds of small patches. At the dorso-medial border of medial entorhinal cortex we identified larger patches, which contained polarized head-direction selective neurons firing during the descending theta-phase. Three axon systems interconnected the patches: centrifugal axons from superficial cells to single large patches; centripetal axons from large patch cells to single small patches, and circumcurrent axons interconnecting large patches. Our microcircuit analysis during behavior reveals modularity of entorhinal processing. If time permits I will complement these findings from entorhinal cortex with data from hippocampal whole-cell recordings in awake behaving animals.