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121.
Dictyostelium chromatin has been purified from nuclei in high yield by differential centrifugation and nuclease cleaving. Its chemical composition has been assayed, and its histones have been analyzed by gel electrophoresis, peptide fingerprints, amino acid composition, and ion-exchange chromatography. The mass ratios of DNA/RNA/histone/nonhistone are 1.0:0.18:0.98:1.02. There are four histones including one unusual histone, H7, which is the most abundant histone in the slime mold. The H4-like protein is the most conserved protein, while the other histones show both similarities and differences with mammalian histones. 相似文献
122.
One mechanism previously proposed for the abiotic accumulation of molecules of one chirality in nature is asymmetric adsorption on the chiral surfaces of optically active quartz crystals. Earlier literature in this field is reviewed, with the conclusion that previous investigations of this phenomenon, using optical rotation criteria, have afforded ambiguous results. We now have studied the adsorption of radioactive D- and L-alanine on powdered d- and l-quartz, using change in radioactivity level as a criterion for both gross and differential adsorption. d-Quartz preferentially adsorbed D-alanine from anhydrous dimethyl-formamide solution, and l-quartz L-alanine. The differential adsorption varied between 1.0 and 1.8%. The implications of these observations are discussed from the viewpoint of early chemical evolution and the origin of optically active organic compounds in nature. 相似文献
123.
124.
This paper reports a technique using microwaves to assist penetration of stains into biopsy sections of muscle and peripheral nerve. The technique results in more consistent and reliable staining of tissue sections for examination by light microscopy. 相似文献
125.
The presence of F3-F2a1 dimers and F1 oligomers in chromatin. 总被引:9,自引:0,他引:9
The oligomeric structure of histones in nuclei and chromatin has been studied by crosslinking nuclei and chromatin with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. Crosslinked histones were detected as new high molecular weight components on SDS gels, and the protomers of the crosslinked histones were identified by their characteristic 125I-fingerprints. The results show that a considerable portion of histones F3 and F2a1 exist in nuclei and chromatin as an F3-F2a1 dimer. Evidence is presented that histone F1 probably exists in chromatin as large oligomers. 相似文献
126.
W A Bonner 《Origins of life and evolution of the biosphere》1999,29(6):615-623
The chirality amplification mechanism proposed by Yamagata in 1966, relying on an Accumulation Principle which involved the parity violating energy difference (1 + epsilon) presumed to be operative at each step in the formation of a homochiral biopolymer, is briefly surveyed historically. The Accumulation Principle is then examined analytically and found to be incapable of producing a unique homochiral polymer in any realistic polymerization process. The extension of the Accumulation Principle to crystallizations which afford enantiomorphic crystals is also scrutinized and found to be misapplied and invalid. 相似文献
127.
Degradation of duplex DNA by S1 nuclease from Aspergillus 总被引:2,自引:0,他引:2
T St John J D Johnson J Bonner 《Biochemical and biophysical research communications》1974,57(1):240-247
128.
R Douce C A Mannella W D Bonner 《Biochemical and biophysical research communications》1972,49(6):1504-1509
The site of synthesis of CDP-diglyceride in purified plant mitochondria has been found to be located on the inner membrane. 相似文献
129.
Preparation of intaintact plant mitochondria 总被引:37,自引:0,他引:37
130.
Summary The general fine structure of intestinal cells and changes which occur in ultrastructure during development from fourth-stage to adult N. dubius are reported. In fourth-stage worms pigment granules are prominent in intestinal cells. In adults the number of pigment granules appears to be reduced and phagolysosomes containing membranous profiles and pigment material increase in number. Another reorganization of cell structure involves mitochondria which are randomly distributed in the cytoplasm of cells in fourth-stage worms, concentrated in the apical cytoplasm in worms in the molting process, and confined to the base of cells in adult worms. Other changes involved structure of the nucleus, rough endoplasmic reticulum and glycogen content of cells.This investigation was supported, in part, by NIH Fellowships I-FI-GM-32750 and 5-F02-AI-32750. 相似文献