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221.
Mingsheng Li Jiawei Shi Canice Chun-Yin Yiu Can Li Kenneth Kin-Yip Wong Lidai Wang 《Journal of biophotonics》2021,14(3):e202000392
Label-free chemical bond imaging is of great importance in biology and medicine. Photoacoustic imaging at the third near-infrared windows (1600-1870 nm, near-infrared-III) provides a stable molecular vibrational imaging tool for lipid-rich tissue owing to the first overtone transition of the C H bond at 1.7 μm. However, lacking high-energy pulsed laser sources at 1.7 μm and the strong water absorption significantly limit the signal-to-noise ratio of the lipid imaging, especially for thin lipid tissues. To circumvent this barrier, we develop near-infrared-III double-illumination optical-resolution photoacoustic microscopy (DIOR-PAM) for improving the sensitivity of label-free lipid imaging. Using the same laser, DIOR-PAM can enhance the sensitivity by nearly 100%, which we prove in the Monte Carlo simulation. We experimentally demonstrated 50% ~ 100% sensitivity enhancements on nonbiological and biological lipid-rich samples. 相似文献
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223.
P. K. S. Shin M. W. Yiu S. G. Cheung 《Marine and Freshwater Behaviour and Physiology》2004,37(3):147-160
The distribution and coexistence of the fiddler crabs U. vocans borealis and U. lactea lactea was investigated in the upper shore of a sandy beach with respect to particle size, water content and total organic carbon content of the sediments. A clear segregation of habitats between the two species was apparent. U. lactea lactea were only found in sediments with significantly lower total organic carbon content. U. lactea lactea had a higher ratio for the size of third maxilliped to body size than U. vocans borealis. There was no statistical difference in the median sediment particle size of the habitats where both species were found on the study shore. U. lactea lactea was larger on shores where U. vocans borealis were absent. Smaller U. vocans borealis individuals occupied sediments with higher water content and finer particles. Smaller individuals of U. vocans borealis also possessed fewer spoon-tipped setae on second maxilliped than their larger conspecifics, which were found mostly on coarser sediments. U. lactea lactea spent significantly more time on the surface than in the burrow during low tide when compared with U. vocans borealis. Both Uca species exhibited similar desiccation resistance. U. lactea lactea tends to keep its frontal region in close contact with sediments to maintain moisture when being exposed to air. 相似文献
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225.
Multiple phospholipase A2 (PLA2) isoenzymes found in a single snake venom induce a variety of pharmacological effects. These multiple forms are formed by
gene duplication and accelerated evolution of exons. We examined the amino acid sequences of 127 snake venom PLA2 enzymes and their homologues to study in which location most natural substitutions occur. Our data show that hot spots of
amino acid substitutions in this group of proteins occur mostly on the surface. A logistic model correlating the substitution
rates of each amino acid residue with their surface accessibility indicates that the probability of natural substitutions
occurring in the fully exposed residue is 2.6–3.5 times greater than that of substitutions occurring in buried residues. These
surface substitutions play a significant role in the evolution of new PLA2 isoenzymes by altering the specificity of targeting to various tissues or cells, resulting in distinct pharmacological effects.
Thus natural substitutions in PLA2 enzymes, in contrast to popular belief, are not random substitutions but appear to be directed toward modifying the molecular
surface.
Received: 11 May 1998 / Accepted: 29 June 1998 相似文献