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  • 1
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 2 (1974), S. 360-371 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The basal structure of the flagellum controls both activity and assembly. In order to define the steps involved in these processes, genetic analysis was performed. Twenty genes were found to be required for the complete assembly and function of the organelle. FlaE controls the length of the hook, flaA is required both to maintain flagellar structure and for chemotaxis, and flaI plays a role in regulating the synthesis of the entire structure. Mutations mapping close to flal (the cfs mutations) release flagellar synthesis from control by catabolite repression.The basal structure was purified and isolated. On SDS acrylamide gel electrophoresis, it contained at least six distinguishable components. One major band corresponded to the hook subunit with an apparent molecular weight of 42,000 daltons. The others had apparent molecular weights of 60,000, 40,000, 28,000, 25,000, and 18,000 daltons. The genes that correspond to these polypeptides have not been identified.In exploring the role of the mot and che genes, assays were developed for the function of individual flagellar filaments. The filaments were found to rotate and rotation could be modulated by changing their direction. Chemotaxis results from the modulation of flagellar rotation. Using the rotation assay the response of nonmotile cells to attractants and repellents was followed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 2 (1974), S. 609-616 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Lateral phase separations in lipid and lipid-protein systems are discussed with the aid of phase diagrams derived from spin-label measurements. Freeze-fracture data from E. coli membranes and model lipid-protein bilayers indicate that the protein tends to associate with fluid lipid phases.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 2 (1974), S. 558-581 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Internal dialysis techniques have been used to examine the influence of external and internal cations on Ca efflux from ATP-depleted squid axons. The main observation is that Ca efflux is promoted by external Na and inhibited by internal Na. The Na0 -dependent Ca efflux appears to be a function of [Na]03, and is also affected by the membrane potential; a 25 mV depolarization may cause as much as an e-fold decrease in Ca efflux. These data are consistent with a counter-transport exchange of 3Na+-for-1Ca2+. A Ca0-dependent Ca efflux has also been observed; it is prominent in Na sea water or Le sea water, and is markedly diminished in choline sea water. This flux is consistent with the idea of a Ca-Ca exchange diffusion process. Taken together, the Na0 - and the Ca0 -dependent Ca effluxes fit a two-site model for carrier-mediated Ca transport; one site binds two Na+ or one Ca2+, while the second site can bind either one Na+ or one Li+. The data reported here suggest that both sites must be filled on the inward journey, but that only the Ca-binding site need be occupied on the outward journey of the carrier. A mechanism of this type could derive sufficient energy from the Na and voltage gradients to maintain a [Ca2+]0/[Ca2+]i concentration ratio of about 104 in the absence of ATP. The present experiments do not, however, rule out the possible participation of a metabolically driven Ca transport mechanism in vivo.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 2 (1974), S. 189-195 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 2 (1974), S. 582-592 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The acetylcholine receptor from Torpedo californica electroplax has been studied at three levels of molecular organization: receptor-rich membrane fragments, solubilized and purified receptor, and reconstituted receptor in phospholipid vesicles. The binding of cholinergic ligands to the membrane-bound and the solubilized material is not cooperative, and the number of ligand sites is less than the number of toxin sites. In addition, the purified macromolecule contains the molecular features necessary for ion-translocation during postsynaptic depolarization, since a chemically excitable membrane can be formed from purified receptor and Torpedo phospholipids.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 2 (1974), S. 429-450 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Microtubule polymerization in vitro was examined using material purified from porcine brain tissue by a reversible temperature dependent assembly procedure, and was characterized by electron microscopy, viscometry, and sedimentation. The reaction was endothermic, colchicine sensitive, and occurred at neutral pH and moderate ionic strength. Divalent cations (calcium, magnesium) were inhibitory at millimolar concentrations, but stimulated polymerization at the micromolar level. Nucleoside triphosphates were required for assembly of purified subunits. As determined by quantitative sedimentation analyses, the reaction was an equilibrium process. Below a critical concentration of tubulin no assembly occurred. Analytical ultracentrifugation studies indicated that tubulin species with sO20, w of 6S and 30S were in equilibrium with each other, and that both were incorporated into microtubules. Electron microscopic analyses suggested that disc (or ring) structures might be intermediates in assembly, and that they were primarily utilized early in the polymerization process. Assembly could be seeded by mixing microtubular fragments from brain or flagella with brain microtubule subunits; depending on conditions of temperature and protein concentration, addition of subunits occurred either with unipolar or biased polar directionality. The possible significance of these properties of the polymerization reaction for control of assembly is discussed.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In part I of this paper (1) we give evidence that the P23-capsoid of τ-particles is transformed in situ into the P23*-capsid of normal phage. Using the polymorphism of phage T4, we have chosen polyheads as representative of P23 assemblies and giant phages as representative of P23* assemblies in order to study their surface crystals by optical filtration of micrographs. We found for polyheads a lattice constant of 112 Å with the typical hexameric, ringlike capsomer and for the giants a lattice constant of 124 Å with quite a different capsomer morphology, of the type (6+1). From the stoichiometry of the proteins composing the normal capsid we conclude that the protomer is a single P23* molecule and that the minor capsid-proteins must be in singular positions on the surface lattice or on the polyhedral head (center of capsomers, vertices, or basal part).We extrapolate the findings on the giant head to the normal head and give a geometric model which is consistent with 1,100 molecules of P23* per capsid.We discuss the part of form inheritance contributed by P23 and the other formgiving gene products and give evidence that morphologic characters are the result of pairs of a reaction chain of interacting gene products. The example we give is the giant head produced by a ts mutant in gene 24 at 36°C.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 2 (1974), S. 302-317 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 2 (1974), S. 196-201 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Bacteriophage T4 tail fibers are rodlike structures with a contour length of about 1400 Å, a diameter of about 45 Å, and a total mass of about 600,000 daltons. The assembly of the tail fibers and their subsequent attachment to the phage particle are under the control of 8 phage-induced proteins. The gene control and molecular weight of each protein are known. The sequence of gene-controlled steps has been determined by the characterization of intermediates that accumulate when various steps are blocked by mutation. The protein composition of the fibers and their precursors has been determined by purification and electrophoretic analysis.Four of the eight gene products are structural components of the tail fiber. These proteins are P34 (150,000 daltons, 2 copies), P37 (120,000 daltons, 2 copies), P35 (40,000 daltons, 1 copy), and P36 (24,000 daltons, 2 copies). The wac (whisker antigen control) gene product is a structural component of the phage whiskers. The remaining three gene products, P38, P57, and P63, are not structural components of the phage particle. Both P63 and the wac gene product promote the attachment of tail fibers to the phage particle. P63 has been shown to act catalytically. Both P38 and P57 are somehow involved in the folding of the major tail fiber structural proteins (P37 and P34). The normal requirement for P38 and P57 functions can be bypassed by secondary mutations.
    Additional Material: 2 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 2 (1974), S. 486-495 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Structural studies of tomato bushy stunt virus and Sindbis virus are discussed in terms of the information they provide about specificity and control in virus and membrane assembly.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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