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1.
2.
Levans produced by four Zymomonas mobilis strains showed antitumour activity against sarcoma 180 and Ehrlich carcinoma in Swiss albino mice. Levans from two strains (ZAP and CP4) had the highest effects. NMR analysis showed that the polymers were composed only of fructose units. The results suggested that the antineoplasic effect is associated to the polysaccharide molecular weight and that a particular molecular weight range may be responsible for this effect. 相似文献
3.
Methemoglobin and metmyoglobin catalyze the H2O2-dependent oxidation of styrene to styrene oxide and benzaldehyde. The formation of styrene oxide requires molecular oxygen as well as H2O2 but does not, as shown by inhibitor studies, involve the superoxide or hydroxyl radicals. Approximately 38, 67, and 78% of the oxygen in styrene oxide derives from 18O2 in the reactions catalyzed, respectively, by bovine hemoglobin, sperm whale myoglobin, and equine heart myoglobin, whereas 70, 55, and 35% of the oxygen can be shown to be derived from [18O]H2O2. However, a larger fraction of the epoxide oxygen than suggested by the labeling data (perhaps all) derives from molecular oxygen rather than H2O2 because the hemoproteins produce molecular oxygen from the peroxide. The epoxidation of styrene by methemoglobin gives equal amounts of the R and S enantiomers and, as shown by studies with trans-[1-2H]styrene, proceeds with partial (33%) loss of the olefin stereochemistry. The results are rationalized by H2O2-dependent formation of a protein radical that combines with molecular oxygen to give a protein-peroxy radical that oxidizes styrene. 相似文献
4.
5.
David A. Fuccillo Louis W. Catalano Jr. Flora L. Moder David A. Debus John L. Sever 《Applied microbiology》1969,17(4):619-622
A new disposable micro tissue culture plate was developed and tested for use in virological procedures. Miniature mammalian cell cultures (minicultures) were grown in these plates. Each plate contained 96 circular cultures in flat wells (7 mm in diameter). Replicate titrations of a number of viruses were performed in various tissues. Excellent reproducibility was demonstrated. Mean infectivity titers determined by miniculture methods were generally within 0.6 log10/ml of macro tube titrations. Standard tissue culture assay techniques such as hemadsorption, interference titration, and microneutralization were easily carried out with this method and were very reproducible. Development of this noncytotoxic disposable micro tissue culture plate now permits the routine performance of rapid, reliable, and reproducible tissue culture tests at a very significant reduction in cost and labor. 相似文献
6.
Variation in the ribosomal internal transcribed spacers (ITS1 and ITS2) among eight taxa of the Mimulus guttatus species complex 总被引:1,自引:0,他引:1
The internal transcribed spacer region (ITS1 and ITS2) of the 18S-25S
nuclear ribosomal DNA sequence and the intervening 5.8S region were
sequenced from three individuals in each of eight taxa of the Mimulus
guttatus species complex. Three discrete variants, or "types," of ITS
sequences were found, among which 30%-40% of sites differed, compared with
1%-2% within types. Dot plots indicate that these types were not related by
conspicuous rearrangements or inversions. More than one ITS type was often
found in the same taxon, and two of three ITS types span species
boundaries, indicating their presence prior to speciation. These ITS
sequences showed essentially no positional homology with the nearest
sequenced relative, tomato. In contrast, the 5.8S region was relatively
unvaried, with 8 of 162 sites varied in the sample among all eight taxa.
The phylogeny inferred by the most common ITS sequence type, rooted by the
two other ITS types, agreed with isozymes in showing the distinctness of M.
nudatus, M. laciniatus, and M. tilingii from the other five taxa.
相似文献
7.
Daniela L Catalano Dupuy Daniela V Rial Eduardo A Ceccarelli 《European journal of biochemistry》2004,271(22):4582-4593
Ferredoxin-NADP(H) reductases (FNRs) represent a prototype of enzymes involved in numerous metabolic pathways. We found that pea FNR ferricyanide diaphorase activity was inhibited by Zn2+ (Ki 1.57 microM). Dichlorophenolindophenol diaphorase activity was also inhibited by Zn2+ (Ki 1.80 microM), but the addition of ferrocyanide was required, indicating that the inhibitor is an arrangement of both ions. Escherichia coli FNR was also inhibited by Zn-ferrocyanide, suggesting that inhibition is a consequence of common structural features of these flavoenzymes. The inhibitor behaves in a noncompetitive manner for NADPH and for artificial electron acceptors. Analysis of the oxidation state of the flavin during catalysis in the presence of the inhibitor suggests that the electron-transfer process between NADPH and the flavin is not significantly altered, and that the transfer between the flavin and the second substrate is mainly affected. Zn-ferrocyanide interacts with the reductase, probably increasing the accessibility of the prosthetic group to the solvent. Ferredoxin reduction was also inhibited by Zn-ferrocyanide in a noncompetitive manner, but the observed Ki was about nine times higher than those for the diaphorase reactions. The electron transfer to Anabaena flavodoxin was not affected by Zn-ferrocyanide. Binding of the apoflavodoxin to the reductase was sufficient to overcome the inhibition by Zn-ferrocyanide, suggesting that the interaction of FNRs with their proteinaceous electron partners may induce a conformational change in the reductase that alters or completely prevents the inhibitory effect. 相似文献
8.
Variation in heat shock proteins within tropical and desert species of poeciliid fishes 总被引:8,自引:0,他引:8
Norris CE; diIorio PJ; Schultz RJ; Hightower LE 《Molecular biology and evolution》1995,12(6):1048-1062
The 70-kilodalton heat shock protein (hsp70) family of molecular
chaperones, which contains both stress-inducible and normally abundant
constitutive members, is highly conserved across distantly related taxa.
Analysis of this protein family in individuals from an outbred population
of tropical topminnows, Poeciliopsis gracilis, showed that while
constitutive hsp70 family members showed no variation in protein isoforms,
inducibly synthesized hsp70 was polymorphic. Several species of
Poeciliopsis adapted to desert environments exhibited lower levels of
inducible hsp70 polymorphism than the tropical species, but constitutive
forms were identical to those in P. gracilis, as they were in the
confamilial species Gambusia affinis. These differences suggest that
inducible and constitutive members of this family are under different
evolutionary constraints and may indicate differences in their function
within the cell. Also, northern desert species of Poeciliopsis synthesize a
subset of the inducible hsp70 isoforms seen in tropical species. This
distribution supports the theory that ancestral tropical fish migrated
northward and colonized desert streams; the subsequent decrease in
variation of inducible hsp70 may have been due to genetic drift or a
consequence of adaptation to the desert environment. Higher levels of
variability were found when the 30- kilodalton heat shock protein (hsp30)
family was analyzed within different strains of two desert species of
Poeciliopsis and also in wild-caught individuals of Gambusia affinis. In
both cases the distribution of hsp30 isoform diversity was similar to that
seen previously with allozyme polymorphisms.
相似文献
9.
D A Carson S Lawrance M A Catalano J H Vaughan G Abraham 《Journal of immunology (Baltimore, Md. : 1950)》1977,119(1):295-300
Although IgG rheumatoid factor may play a central role in the pathogenesis of rheumatoid arthritis, previously there have been no precise methods for its specific measurement in serum and synovial fluid. This paper describes a solid phase radioimmunoassay for the independent quantification of IgM and IgG rheumatoid factor reacting with the Fc fragment of human IgG. As measured by this assay, serum IgG rheumatoid factor levels differed significantly between patients with seropositive and seronegative rheumatoid arthritis and normal control subjects. In addition, several sera and joint fluids from patients with seropositive rheumatoid arthritis, even without vasculitis, were shown by gel chromatography to have acid-dissociable complexes of IgG rheumatoid factor suggestive of IgG-IgG dimer or trimer formation. 相似文献
10.
Treatment of PC12 and C6 cell cultures with recombinant basic fibroblast growth factor results in approximately a five to ten-fold stimulation of beta-amyloid precursor mRNA in the C6 astrocytoma cell line but only a slight induction of precursor mRNA in the PC-12 neuronal cell line. Stimulation of expression occurred at a hormone concentration of approximately 0.5 to 1 nM and was seen after 2 days. These results suggest that basic fibroblast growth factor may contribute to amyloidosis of Alzheimer's disease. 相似文献