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1.
Elevated serum gamma-glutamyl transferase (GGT) levels were found in 29% of 155 chronic alcoholics undergoing detoxification treatment. Alkaline phosphatase (AP) was increased in 16%, alanine aminotransferase--SGPT (ALT) in 12% of the patients, while 23% had elevations of either AP or ALT or both. Of the foregoing parameters, GGT was the best single indicator of liver involvement. In course of the follow-ups GGT/ALT correlation improved, but GGT/AP correlation deteriorated. In 9 patients, abstinence during follow-up was associated with progressive decrease in previously elevated serum GGT. Because of its unique sensitivity, GGT may be useful as a screening and/or monitoring aid in alcoholism. 相似文献
2.
The light-induced free-radical signal of Photosystem II (observed after illumination at 77 °K) has been studied in chloroplasts as a function of the oxidation-reduction potential established prior to freezing. The intensity of the light-induced signal is unchanged in the potential region of +590 mV to +760 mV. At higher potential (+850 mV), there is a 30% decrease in signal intensity. The light-induced signal decreases to zero in the low-potential region, with a midpoint potential of +475 mV. These results are considered in terms of a Photosystem II reaction-center complex in which the light-induced free-radical signal arises from the oxidized form of the reaction-center chlorophyll, and this chlorophyll molecule is capable of being reduced at liquid-nitrogen temperature by a secondary electron donor which has a midpoint oxidation-reduction potential of +475 mV. 相似文献
3.
Interaction of plastocyanin with photosystem I: a chemical cross-linking study of the polypeptide that binds plastocyanin 总被引:10,自引:0,他引:10
Plastocyanin has been covalently cross-linked to photosystem I (PSI) by using a water-soluble cross-linker, N-ethyl-3-[3-(dimethylamino)propyl]carbodiimide. The cross-linking reaction is light stimulated and results in the disappearance of a single 19-kDa subunit of PSI with the formation of a new protein-staining component of 31 kDa. The new product at 31 kDa reacts with both plastocyanin and 19-kDa subunit antibodies. Carboxyl group modified plastocyanin does not form a cross-linked product with PSI, implying that the negatively charged surface-exposed groups on plastocyanin are necessary to stabilize binding. These results demonstrate a specific interaction of plastocyanin with PSI and further implicate a specific protein to which plastocyanin binds to facilitate electron transfer to the P700 reaction center. 相似文献
4.
Topography of the Protein Complexes of the Chloroplast Thylakoid Membrane : Studies of Photosystem II using Pronase Digestion and Chemical Labeling 总被引:1,自引:1,他引:0
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The accessibility of various Photosystem II (PSII)-associated polypeptides to the protease pronase and the chemical modifier trinitrobenzene-sulfonic acid (TNBS) has been investigated. Three polypeptides with apparent molecular weight of 32, 21, and 16 kilodaltons, known to be associated with O2 evolution, are all resistant to pronase digestion and TNBS labeling in intact thylakoids. All the polypeptides in the isolated PSII preparation were labeled with TNBS while a different pattern of labeling was observed when the PSII complex was isolated from TNBS-modified thylakoids. Attempts to prepare PSII particles from pronase-treated thylakoids using the Triton X-100 solubilization method were unsuccessful. Pronase-treated thylakoids were probed with antisera against the chlorophyll proteins of PSII using immunoblotting techniques. This allowed for a positive identification of proteolytic fragments from the respective proteins. The results are discussed in relation to the transmembrane organization of PSII in spinach thylakoids. 相似文献
5.
6.
Deoxyribonucleic Acid Base Composition of Clostridial Species 总被引:8,自引:7,他引:1
Ben'Ichiro Tonomura Richard Malkin Jesse C. Rabinowitz 《Journal of bacteriology》1965,89(5):1438-1439
7.
In situ laser Michelson interferometry was utilized to investigate mechanisms of growth and surface morphology in protein and virus crystallization, These included plant proteins canavalin and thaumatin and turnip yellow mosaic virus. The experimental apparatus allowed us to obtain interferometric patterns and investigate growth kinetics from growing macromolecular crystals as small as 20 μm. For the crystallization of canavalin, dislocations are the sources of growth steps on the surfaces. Supersaturation and time dependencies of the normal growth rates, tangential growth step velocities, and the slopes of the dislocation hillocks were measured. The kinetic coefficient β (rate of incorporation of protein molecules into the growing crystal) was estimated for canavalin to be 9 × 10-4 cm/sec. This is among the first estimates of such fundamental kinetic parameters for macromolecular crystallization. The change in the activities of dislocation sources under different growth conditions was also analyzed. Michelson interferometry was clearly demonstrated to be a useful tool for quantitative studies of macromolecular crystal growth. 相似文献
8.
Incubation of thylakoid membranes from spinach with low concentrations of mercuric chloride induces the loss of one of the iron-sulfur centers, FB, in Photosystem I (PS I) and inhibits the electron transfer from PS I to the soluble electron carrier, ferredoxin. Reconstitution of this damaged iron-sulfur center has been carried out by incubating treated thylakoid membranes with exogenous FeCl3 and Na2S in the presence of-mercaptoethanol under anaerobic conditions. Low temperature EPR measurements indicate that center FB is largely restored. Kinetic experiments show that the restored FB can be photoreduced from P700. However, these reconstituted thylakoid membranes are still incompetent in the photoreduction of ferredoxin and NADP+, even though ferredoxin binding to the modified membranes was not impaired, indicating additional changes in the structure of the PS I complex must have occurred. 相似文献
9.
Oh-oka Hirozo; Kakutani Saki; Matsubara Hiroshi; Malkin Richard; Itoh Shigeru 《Plant & cell physiology》1993,34(1):93-101
The photoactive reaction center (RC) complex from the greensulfur bacterium Chlorobium limicola f. thiosulfatophilum, strainLarsen, was isolated after solubilization and ammonium sulfatefractionation followed by ion-exchange chromatography. The spectrumof the complex was almost identical with that of the similarRC complex isolated by Feiler et al. [(1992) Biochemistry 31:26082614] except for the presence of cytochrome c551instead of c553 in the latter study. A molecular ratio of BChla to P840 of the isolated RC complex was assayed to be 2535.SDSPAGE analysis revealed that the isolated complex containedthree major polypeptides with apparent molecular masses of 68,41 and 21 kDa, respectively. The 21-kDa polypeptide was identifiedto be a heme-binding protein by staining the gel for peroxidaseactivity. The cytochrome c551 was oxidized by flash light ina biphasic manner with half times of 90 and 390 µs, respectively,that coincided with the reduction half times of P840+. Threedistinct iron-sulfur centers assigned to FA, FB and Fx, respectively,from their g-values were detected by EPR spectroscopy at cryogenictemperature. These results suggest that the present preparationcontains a minimal functional unit of the RC of this bacterium,and that this complex appears to lie on a evolutionary linebetween RC's of purple bacteria and photosystem I. (Received August 18, 1992; Accepted October 28, 1992) 相似文献
10.
mtDNA diversity in rhesus monkeys reveals overestimates of divergence time and paraphyly with neighboring species 总被引:4,自引:0,他引:4
Reconstructions of the human-African great ape phylogeny by using
mitochondrial DNA (mtDNA) have been subject to considerable debate. One
confounding factor may be the lack of data on intraspecific variation. To
test this hypothesis, we examined the effect of intraspecific mtDNA
diversity on the phylogenetic reconstruction of another Plio- Pleistocene
radiation of higher primates, the fascicularis group of macaque (Macaca)
monkey species. Fifteen endonucleases were used to identify 10 haplotypes
of 40-47 restriction sites in M. mulatta, which were compared with similar
data for the other members of this species group. Interpopulational,
intraspecific mtDNA diversity was large (0.5%- 4.5%), and estimates of
divergence time and branching order incorporating this variation were
substantially different from those based on single representatives of each
species. We conclude that intraspecific mtDNA diversity is substantial in
at least some primate species. Consequently, without prior information on
the extent of genetic diversity within a particular species, intraspecific
variation must be assessed and accounted for when reconstructing primate
phylogenies. Further, we question the reliability of hominoid mtDNA
phylogenies, based as they are on one or a few representatives of each
species, in an already depauperate superfamily of primates.
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