Functional analysis of a cytoplasmic domain-deleted mutant of the CD4 molecule

The CD4 molecule is a receptor found on a subset of T lymphocytes. It has been proposed that, upon binding MHC class II molecules expressed on APC, the CD4 molecule enhances the responsiveness of the T cell by increasing intercellular avidity and/or by transducing an intracellular signal. We have analyzed the effect of removing the cytoplasmic domain of the CD4 molecule on the ability of the CD4 molecule to enhance T cell responsiveness. The cytoplasmic domain-deleted mutant of the CD4 molecule (CD4 delta) was found to be as efficient as the CD4 molecule at enhancing responsiveness to cells bearing the appropriate Ag. If subcellular Ag in the form of purified Ag incorporated into liposomes was used, the CD4 molecule was found to be much more efficient than the CD4 delta molecule at enhancing responsiveness. However, the defect in the ability of the CD4 delta molecule to enhance responsiveness could be compensated for by increasing the level of expression of the CD4 delta molecule.     

Geometric features of the DNA double helix in the supercoiled state

The geometric features of the DNA molecule in the supercoiled state were considered. A model of the supercoiled structure of the DNA molecule was constructed; the model takes into account its natural helicity. The force factors arising in the molecule at various superhelix angles were calculated.     

On the origin of the transfer RNA molecule.

Data and arguments are given in favour of the hypothesis that the primitive tRNA molecule may have originated from a direct duplication event involving one of the two halves of the tRNA molecule. It seems that a molecule capable of assuming a hairpin structure was involved as a precursor in this duplication. The two halves of the present tRNAs could, therefore, be considered as paralogous.     

Lactate biosensor and energy supply for the enzyme molecule

A biosensor of lactate has been constructed, made, and tested. The lactate biosensor uses the lactate dehydrogenase molecules from muscle. The lactate biosensor works according to the simplest scheme. An immobilized lactate dehydrogenase molecule binds a L-lactate molecule in the absence of the coenzyme NAD+. Then the L-lactate molecule is oxidized by the electric field of a metal electrode of the biosensor to generate an electron. The transfer of this electron between the immobilized lactate dehydrogenase molecule and the metal electrode of the biosensor is carried out without a redox mediator molecule. A new mechanism for the energy supply of the enzyme molecule is proposed to explain this effect. The new mechanism is based on the electric dipole-dipole interactions occurring in the enzyme molecule and surrounding water and on the thermal energy of this water.     

Dramatic differences in the motions of the mouth of open and closed cytochrome P450BM-3 by molecular dynamics simulations

Molecular dynamics trajectories were calculated separately for each of the two molecules in the asymmetric unit of the crystal structure of the hemoprotein domain of cytochrome P450BM-3. Each simulation was 200 ps in length and included a 10 Å layer of explicit solvent. The simulated time-average structure of each P450BM-3 molecule is closer to its crystal structure than the two molecular dynamics time-averaged structures are to each other. In the crystal structure, molecule 2 has a more accessible substrate binding pocket than molecule 1, and this difference is maintained throughout the simulations presented here. In particular, the substrate docking regions of molecule 1 and molecule 2 diverge in the solution state simulations. The mouth of the substrate binding pocket is significantly more mobile in the simulation of molecule 2 than in the simulation of molecule 1. For molecule 1, the width of the mouth is only slightly larger than its X-ray value of 8.7 Å and undergoes fluctuations of about 1 Å. However, in molecule 2, the mouth of the substrate binding pocket is dramatically more open in the time-average molecular dynamics structure (14.7 Å) than in the X-ray structure (10.9 Å). Furthermore, this region of the protein undergoes large amplitude motions during the trajectory that are not seen in the trajectory of molecule 1, repeatedly opening and closing up to 7 Å. Presumably, the binding of different substrates will induce the mouth region to adopt different conformations from within the wide range of structures that are accessible. © 1995 Wiley-Liss, Inc.     

Isolation and characterization of the precursor of type M collagen.

A 225000-Mr peptide has been purified from rat chondrosarcoma which is immunologically and biochemically related to type M collagen. Rotary shadowing shows this molecule to be twice the length of the type M molecule and has a prominent kink close to one end. We believe this molecule represents parent type M, the form of the molecule in vivo.     

高频激光-DNA分子相互作用体系相空间的局域特征

利用激光与DNA分子相互作用的动力学模型,借助适当的数值方法,讨论了系统动力学演化及相空间特性。结果表明：高频激光可使DNA分子的运动状态发生变化;特别地,相空间分析表明,高频激光的作用会使DNA分子运动在一些特定状态之间转变。从而可说明高频激光作用下DNA分子呈现新的有序运动现象。     

Acetylcarnitine: on the relationship between structure and function

Acetylcarnitine chloride, a molecule with cholinergic properties, has been studied by X-ray crystallographic techniques. Results show that a portion of the acetylcarnitine molecule is in the same configuration as the functionally similar acetylcholine molecule and other cholinergic molecules.     

Interaction of cytochrome c with the phosphorprotein phosvitin.

Candida krusei cytochrome c forms a molecular complex with phosphorprotein phosvitin in weakly alkaline solution of low ionic strength. At most, about 22 molecules of cytochrome c bind to a phosvitin molecule. The complex at the binding ratio below about 11 (half of the maximum ratio) as a much higher binding strength. Several lines of evidence indicate that the marked difference in the binding strength is due to the difference in negative charges on phosvitin molecule concerned in the binding of a cytochrome c molecule. The phosvitin-bound cytochrome c seems to have a preferred orientation with the front surface of the molecule containing the exposed heme edge in contact with the phosvitin molecule.     

A persistent model of the reptation movement of a DNA molecule

By using a persistent model of the movement of a DNA molecule, the penetration of the DNA molecule into a cell has been described. The method enables one to estimate the time and the rate of passage of the DNA molecule into the cell nucleus. The effect of the curvature of the molecule on its longitudinal movement has been studied. The results obtained can be applied to characterize long chain molecules.     

A Comparison Among the Models Proposed to Explain the Origin of the tRNA Molecule: A Synthesis

A comparison is made among all the models proposed to explain the origin of the tRNA molecule. The conclusion reached is that, for the model predicting that the tRNA molecule originated after the assembly of two hairpin-like structures, molecular fossils have been found in the half-genes of the tRNAs of Nanoarchaeum equitans. These might be the witnesses of the transition stage predicted by the model through which the evolution of the tRNA molecule passed, thus providing considerable corroboration for this model.     

Immunogenic structure of the influenza virus hemagglutinin

We chemically synthesized 20 peptides corresponding to 75% of the HA1 molecule of the influenza virus. Antibodies to the majority (18) of these peptides were capable of reacting with the hemagglutinin molecule. These 18 peptides are not confined to the known antigenic determinants of the hemagglutinin molecule, but rather are scattered throughout its three-dimensional structure. In contrast, antibody raised to intact hemagglutinin did not react with any of the 20 peptides. Taken together these results suggest that the immunogenicity of an intact protein molecule is not the sum of the immunogenicity of its pieces.     

Structural organization of the fibrinogen molecule

A brief review of the chemical structure of the fibrinogen molecule, its proteolytic fragmentation, physicochemical and functional properties of proteolytic fragments is presented. The previous notions on the structure of the fibrinogen molecule are considered as well as new data obtained by the methods of scanning microcalorimetry, electron microscopy and by other methods which permit suggesting some models for structural organization of the fibrinogen molecule.     

Improve the Performance of the All‐Small‐Molecule Nonfullerene Organic Solar Cells through Enhancing the Crystallinity of Acceptors

Significant development has been achieved in nonfullerene organic solar cells. However, most of the high‐efficiency nonfullerene systems are composed of polymer donors and fused‐ring acceptors, and only a few small molecule donors can work well. Herein, a new A–D–A small molecule donor named NDTSR with naphtho[1,2‐b:5,6‐b′]dithiophene (NDT) as building blocks is synthesized. Two energy levels well‐matched fused‐ring acceptors ITIC and IDIC are chosen to construct all‐small‐molecule solar cells with NDTSR, respectively. When mixed with IDIC, a high power conversion efficiency (PCE) of 8.05% is achieved, which is the highest efficiency for NDT‐based small molecule donor. However, the NDTSR:ITIC system only exhibits a low PCE of 1.77%. The big difference in the performance of these two systems should be attributed to the different morphology and phase separation resulting from the crystallinity and aggregation ability of the acceptors. The results demonstrate that NDT‐based small molecule is a promising candidate donor for all‐small‐molecule systems, while the crystallinity of fused‐ring acceptors is a critical factor for optimizing the phase separation in the active layer.     

A modified approach to the measurement problem: objective reduction in the retinal molecule prior to conformational change

A new analysis of the measurement problem reveals the possibility that collapse of the wavefunction may now take place just before photoisomerization of the rhodopsin molecule in the retinal rods. It is known that when a photon is initially absorbed by the retinal molecule which, along with opsin comprises the rhodopsin molecule, an electron in the highest pi orbital is immediately excited to a pi* orbital. This means that a measurement or transfer of information takes place at the quantum level before the retinal molecule commences the conformational change from cis to trans. This could have profound implications for resolving some of the foundational issues confronting quantum mechanics.     

Light-scattering study on the influence of link-glycoproteins and lysozyme on the hyaluronate molecular conformation in solution

The influence of link-glycoproteins and mammalian lysozyme on the configuration and size of the hyaluronate molecule in highly diluted solutions under physiological electrolytic and pH conditions was investigated by light-scattering techniques and confirmed by column chromatography, isopycnic flotation, and boundary centrifugation. It was consistently found that link-glycoproteins induce an increase in the basic structural dimensions of the hyaluronate molecule in solution. It was also found that this increase was reversed or prevented under the action of mammalian lysozyme. Changes in configuration of the hyaluronate molecule could be related to its aggregating capacity when the hyaluronate interacts with proteoglycan subunits. It is postulated that link-glycoproteins induce structural changes in the hyaluronate molecule that might improve its aggregating capacity while mammalian lysozyme prevents or regulates such improvement.     

Structure of the chromophore fragment of copsomycin

The chromophore moiety of the copsomycin molecule was isolated in the form of dimethyl ether as an individual substance from the products of antibiotic acid hydrolysis. Physicochemical properties of the chromophore were studied. UV, 1H and 13C NMR, mass spectrometry and elementary analysis showed that the copsomycin molecule moiety was identical to the chromophore moiety of the molecule of multiomycin or nosiheptide.     

Capillary electrophoresis study on the dimeric SOD enzyme in the presence of ascorbic acid

A Notable decrease of the peak intensity of the capillary electrophoregram due to the dimeric SOD molecule was observed when a solution containing copper(II) chloride and ascorbic acid was added to the SOD solution, indicating that the capillary electrophoresis method is useful to detect the dissociation of the dimeric SOD molecule in solution, and that dissociation of the dimeric SOD molecule is induced by the presence of hydrogen peroxide. The present results may give reasonable countermeasures towards the sporadic amyotrophic lateral sclerosis in future.     

A glycophospholipid covalently attached to the C-terminus of the Thy-1 glycoprotein

The Thy-1 glycoprotein is a very abundant cell surface molecule of rat thymocytes and neuronal cells with the properties of a molecule that inserts into the lipid bilayer. The hydrophobicity is due to a glycophospholipid component covalently attached to the carboxy group of the C-terminal cysteine residue. The mature glycoprotein does not contain a stretch of hydrophobic amino acids that could traverse the membrane bilayer. These findings present a new mode of membrane attachment for a cell surface molecule that can mediate lymphokine release and cell division after cross-linking by antibodies.     

Some structural and functional aspects of the cell adhesion molecule uvomorulin

The cell adhesion molecule uvomorulin (UM) was analysed by comparing antisera produced against the whole molecule (gp123) with antisera made against fragments of UM. Of the proteins recognized by different anti-UM antisera (molecular weights of 123, 102, 92 and 84 kDa), the 102 kDa molecule is not derived from gp123. The 102 kDa molecule is not glycosylated and is also different from gp123 by peptide map analysis. However, rabbit antisera raised against the purified 102 kDa protein interfered with the aggregation of embryonal carcinoma (EC) cells. Also, a monoclonal antibody selected to interfere with EC cell aggregation recognized the 102 kDa molecule as well as gp123. Thus, the functional site of cell adhesion seems not to be mediated by sugar residues. Experimental evidence is provided suggesting that UM is not only involved in the compaction of preimplantation embryos but seems to be an ubiquitous cell adhesion molecule regulating epithelial cell adhesion mechanisms.