Flouorescence techniques are uniquely suitable for probing cells because their sensitivity and specificity. Since fluorescence from a single cell can be detected with a microscope as an image, fluorescence microscopy has great petential for qualitative and quantitative studies on the structure and function of cells. Here, we have studied the receptor-mediated signal transduction in B cells, T cells and basophilic leukemia cells by confocal fluorescence microscopy. The results gave njew insights for the molecular mechanisms in immune response.
N-ethylmaleimide-sensitive factor (NSF) is originally characterized as a factor involved in intraGolgi protein transport reconstituted in a cell-free system. Later studies show that NSF is an ATPase and generally used as machinery for vesicle-mediated intracellular protein transport. This review summarizes the structure and function of NSF.
Recent progress in direct observation of surface monolayer at the air-water interface by fluorescence microscopy is reviewed in this article. Dynamic process of crystallization in two-dimensional molecular film is directly observed by a epifluorescence microscope. Crystallization process and morphological properties are largely dependent on the chemical structure of monolayer forming amphiphiles. Electrostatic interaction at the interface between charged monolayer and counter charged polyelectrolyte dissolved in water subphase strongly affects crystal-lization process of the monolayer. Some enzymatic reactions at the air-water interface can be visualized as morphological change of phospholipid monolayers.
Instead of the enumeration of amino acid changes in the usual studies of protein evolution, a novel approach is proposed to investigate the amino acid changes focusing on the properties of changed residues. This is illustrated by two analyses: one is the discrimination between adaptive changes and neutrat ones and another is the principal component analysis to assign similar region (s) of the proteins, which seem to be distantly related but cannot be easily detected by the usual similarity search. Throughout these analyses, concrete evidences are provided for divergence pattern and selective mode in amino acid changes, connecting some of the changes with functional changes.
The mollusc myoglobin possesses naturally occurring substitution at the distal E7 position (Val-E7) and its oxygen affinity is only slightly lower than those of the common mammalian myoglobins possessing the usual His E7. The structure-function relationship in this myoglobin is notexplained on the basis of the results obtained from the study of the site-directed mutation at the E7 position of mammalian myoglobin. The recent mutation, crystallographic and nuclear magnetic resonance spectroscopy studies have revealed that a guanidino NH proton of Arg E10 in the mollusc myoglobin serves as an alternative hydrogen-bond donor to the bound ligand to maintain a high ligand affinity. The functional properties of the mollusc myoglobin possessing the Val E7 are controlled by a mechanism different from that of the mammalian myoglobin possessing His E7.
A protocol using a simulated annealing in four-dimensional space is shown to have excellent sampling properties. In two systems of simulated data, using an unconstrained Ala 30 mer and BPTI, the protocol searches a sufficiently large conformational space and gives complete convergence of the optimization without any trace of initial structure dependence. As a result of an exhaustive sampling, the intrinsic nature of the calculated structures has been revealed. The average of the sampled structures always show a certain pattern of discrepancy from the X-ray structure. This discrepancy is due to the short distance nature of NMR data, and correlates with the characteristic shape of the molecule.