Biophysical Society Thematic Meeting - June 28-July 1, 2015

New Biological Frontiers Illuminated by Molecular Sensors and Actuators

Poster Abstracts

29-POS Board 29 Functional Conformational Changes of Blue-light Sensing Cryptochrome Chongjun Ma , Pei Li, Yawei Dai, Yan-Wen Tan. Fudan University, Shanghai, China.

Cryptochromes, a kind of blue-light sensing proteins, are best known to regulate the entrainment of circadian rhythms responses in diverse organisms. More intriguingly, they are found to involve in the sensing of magnetic fields for insects and small animals. Algae, plant and animal cryptochromes possess vastly different size of carboxy-terminal (C-terminal) extensions, while the C-terminal domain is found to be significant in the functional response of plant cryptochromes. Here, we investigate the interaction partner, functional mechanism, and the possible C-terminal conformational changes of an alga cryptochrome (aCry). Protein pull-down assay is used to screen possible interaction partners of aCry, and a component of the circadian rhythm was found to directly interact with aCry in a blue-light dependent manner. We use single molecule Förster Resonance Energy Transfer (smFRET) to study the conformational changes of aCry. In the dark, aCry stays in the close conformation as monomer. Exposure to blue-light causes aCry to endure a conformational release of C-terminal domain from the PHR domain and partial homodimerization. Chemical reduction of the cryptochrome cofactor, FAD, induces further conformational extension in the presence and absence of blue-light. 30-POS Board 30 Tuning the Temperature of Single Cells: a New Tool to Study Temperature Sensing Hairong Ma . Drexel University, Philadelphia, USA. Temperature fluctuation is a common environmental cue that can affect many essential cellular activities including metabolism, proliferation, and apoptosis. Recent study shows that single cells can directly sense the environmental temperature change and respond through metabolic adjustment such as thermogenesis. Yet the mechanism of temperature sensing is largely unknown and remains an intriguing problem. The effort is stymied by the lack of appropriate tools that can induce a wide range of temperature perturbations in live cells with adequate time resolution. To address this problem we have developed a novel platform combining infrared laser induced temperature-jump (T-jump) and fluorescence live-cell imaging, whereupon we can tune the temperature of single cells or cell populations up to 60 degrees Celsius with millisecond resolved time resolution.

63