Tham khảo tài liệu 'encyclopedia of smart materials (vols 1 and 2) - m. schwartz (2002) ww part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 3-5 m atmospheric transmission window. Roughly two orders of magnitude more total flux come from a 1000 K object compared to that from a 310 K object. An object at 310 K emits 27 of its total flux in the 8-12 m bandpass and in the 3-5 I m bandpass. Alternatively an object at 1000 K emits of its total flux in the 8-12 m bandpass and 36 in the 3-5 I m bandpass. This discussion of infrared emitting objects and which is the better emitter is important to keep in mind as we discuss biological infrared detectors. Bacterial Thermoreception Cellular processes are influenced by temperature and therefore cells must possess temperature-sensing devices that allow for the cell s survival in response to thermal changes. Virtually all organisms show some kind of response to an increase or decrease in temperature but sensing mechanisms are not well understood. When bacterial cells are shifted to higher temperatures a set of proteins known as heat-shock proteins are induced. These proteins include molecular chaperones that assist in refolding proteins that aggregate at higher temperatures as well as proteases that degrade grossly misfolded proteins 12 13 . Changes in temperatures can also be sensed by a set of coiled-coil proteins called methyl-accepting proteins MCPs that regulate the swimming behavior of the bacterium Escherichia coli 14 . Coiled-coil proteins are formed when a bundle of two or more alpha-helices are wound into a superhelix Fig. 6 15 . The MCPs can be reversibly methylated at four or five glutamate residues 16 . Methylation and demethylation it is presumed is the trigger that dictates the response during temperature the unwinding of TlpA helices is highly rev downshift in temperature leads once again to of functional dimers. Because TlpA is not irre tured it serves as an active thermosensing d that the denaturation and renaturation proc lows cells to adapt quickly to changes in te shown in Fig. 7 the change in the structur measured by circular dichroic .
