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931.
Three new diterpenoids have been detected in Salvia oxyodon and identified as 3β-hydroxy-dehydroabietic acid, 3β-acetoxy-abieta-8(14)-en-18-oic acid 9α,13α-endoperoxide and 3β-hydroxy-abieta-8(14)-en-18-oic acid 9α,13α-endoperoxide. Salvia lavandulifolia yielded two known compounds ursolic acid and galdosol. 相似文献
932.
Interactions of homologous and heterologous deoxyribonucleic acids and competent Bacillus subtilis cells. 总被引:2,自引:1,他引:1
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Glucosylated and nonglucosylated bacteriophage T4 deoxyribonucleic acids (DNAs) are able to bind to competent cells of Bacillus subtilis, although the former does so in a rather unstable fashion, probably because of the glucosylation. Several heterologous DNAs compete with homologous DNA for the same receptors in binding and in transformation. A different pattern in competition for DNA binding was observed for homologous and T4 glucosylated DNAs in intact cells as compared with protoplasts or membrane vesicles. The results are consistent with the existence of two types of receptor sites on the membrane of competent B. subtilis cells. 相似文献
933.
The light-induced hindrance of spin label motion increases linearly with light intensity. However, it has not been possible to unambiguously demonstrate light saturation due to the very high rates of spin label reduction at high light intensity. The light-induced hindrance of spin label motion may be mimicked in the dark by subjecting thylakoids to appropriately low pH regimes. Uncouplers such as gramicidin-D and methylamine reduce the light-induced hindrance to dark levels as does ethylenedinitrilotetraacetate (EDTA) treatment. Valinomycin plus KCl which destroys the electric potential is only partially effective in reducing the light-induced hindrance. These results indicate that protons in the aqueous lumen of the thylakoids are closely involved with the observed light-induced hindrance of spin label motion. 相似文献
934.
G C Wagner M Perez W A Toscano I C Gunsalus 《The Journal of biological chemistry》1981,256(12):6262-6265
Apoprotein suitable for heme reconstitution has been prepared by an acid/butanone extraction of cytochrome P-450cam at pH 2.5. Absorption spectra of apo-P-450cam indicate less than 2% residual holoenzyme. Four tryptophan residues per molecule were estimated from the aromatic absorbance region of denatured apoprotein. Heme-reconstituted holoprotein was purified in 30% yield to a specific activity equivalent to the native enzyme. Absorption and EPR spectra of 57Fe- and 54Fe-heme-enriched P-450cam reveal complete restoration of the native active site. 相似文献
935.
Dr. Donna M. Peehl Richard G. Ham 《In vitro cellular & developmental biology. Plant》1980,16(6):526-540
Summary A survey of commercially availabla media revealed that medium F-12 was superior to medium 199 for clonal growth of human epidermal
keratinocytes (HK) when supplemented with 10 μg/ml hydrocortisone (HC) plus dialyzed fetal bovine serum protein (FBSP), rather
than the whole serum used in previous studies. Qualitative and quantitative adjustment of the medium composition for optimal
clonal growth with minimal amounts of FBSP generated a new medium, MCDB 151, which supports clonal growth of HK with 10 μg/ml
HC and as little as 1 mg/ml FBSP (equivalent in protein concentration to 2.0% whole serum). MCDB 151 differs significantly
from MCDB 105, previously developed in this laboratory for normal human fibroblasts, and each medium selectively favors growth
of its own type of cell in primary cultures of disaggregated human neonatal foreskin cells. Differences in the amounts of
calcium and adenine in the two media appear to be among the most influential factors mediating the selective growth. Optimal
growth of HK occurs at a very low level of Ca2+ that causes the colonies to remain as monolayers rather than stratifying as they do in the presence of higher levels of calcium.
However, keratin synthesis, which was examined through use of highly specific fluorescent antibodies, is not affected by the
Ca2+ concentration. Agents that increase intracellular cyclic AMP levels appear to have no effect on HK growth in MCDB 151 with
10 μg/ml HC and 1.0 mg/ml FBSP.
This paper contains material from a thesis submitted to the Graduate School of the University of Colorado, Boulder, by Donna
M. Peehl in partial fulfillment of the requirements for the Ph.D. degree.
This work was supported by Grant CA 15305 from the National Cancer Institute and Grant AG 00310 from the National Institute
on Aging. 相似文献
936.
E Perez G Zamboni P L Parmeggiani 《Bollettino della Società italiana di biologia sperimentale》1980,56(10):1002-1006
The cAMP concentration in the preoptic region was studied in rats during exposure to low ambient temperature (Ta: -10 degrees C) and after return to control Ta (22 degrees C). With respect to control cAMP concentration, changes were observed consisting of a decrease (delta cAMP: 4.19 /+- 0.15 pM/mg Pr; p < 0.001) at low Ta and an increase (delta cAMP: 1.40 /+- 0.13 pM/mg Pr; P < 0.05) after return to control Ta. In contrast, cortical cAMP concentration decreased both at low Ta (delta cAMP: 2.94 /+- 0.09 pM/mg Pr; P < 0.005) and after return to control Ta (delta cAMP: 3.21 /+- 0.09 pM/mg Pr; P < 0.001). such cAMP changes in the preoptic region may be related to different activation levels of thermoregulatory and sleep mechanisms. 相似文献
937.
The population of a large central area of Argentina is affected by a syndrome designed as “regional and endemic chronic hydroarsenicism.”
A number of types of neoplasms, especially of skin, urinary bladder, and of digestive system, occur with higher frequency
in these areas. Drinking water in some of the affected areas contains from 0.1 to 1.2 mg/L of As. 相似文献
938.
Wendy Love Donna Millay James S. Huston 《Archives of biochemistry and biophysics》1981,207(2):300-310
This investigation pursued aspects of tubulin structure using limited tryptic digestion as a sensitive monitor of conformational state. A novel form of tubulin was analyzed that had been purified on hydroxyapatite in sodium phosphate buffer and exhibited interchain disulfide crosslinking. Circular dichroism spectra of this protein were highly reproducible and indicate it assumes a stable native state. Limited proteolysis of bovine brain microtubule protein in its assembled or disassembled states yielded a prominent 41,000-molecular-weight product as long as it was stabilized by GTP-containing buffers. Hydroxyapatite-purified tubulin yielded entirely different limited digestion products, with species having molecular weights of 48,000 and several between 35,000 and 19,000. Limited proteolysis was found to offer a useful probe of tubulin structure and to produce fragments which might prove valuable in analyzing its protein substructure. Discussion is given on the relevance of these results to the structural state assumed by tubulin and to the conformation of disulfide-linked tubulin reported to reside in the postsynaptic density. 相似文献
939.
Peter F. Daniel Donna F. De Feudis Ira T. Lott Robert H. McCluer 《Carbohydrate research》1981,97(2):161-180
The rapid separation and quantitative determination of per-O-benzoyl oligosaccharides were obtained using high performance, liquid chromatography. Oligosaccharides were completely O-benzoylated without concomitant N-benzoylation of acetamidodeoxyhexoses. Benzoylation prior to analysis allowed a quantitative determination of picomolar amounts because the absorbance at 230 nm of these derivatives is directly proportional to the number of benzoyl groups present. Separation by normal and reversed-phase chromatography was demonstrated, and the best resolution was obtained on an Ultrasphere octyl column. Excellent separations of oligosaccharides containing up to 10 sugar residues present in mannosidosis urine and of malto-oligosaccharides containing up to 15 sugar residues present in Karo syrup were achieved within an analysis time of 30 min. Anomers of maltose, maltotriose, and maltotetraose were separated; for this reason, reduction of complex samples prior to analysis is advisable. The effect of linkage configuration on retention time was tested with reduced, α-linked di- and tri-glucopyranosides. The presence of an acetamidodeoxyhexose residue in an oligosaccharide significantly reduced its retention time, whereas branching had the opposite effect. A linear response was obtained for the injection of 1–600 pmol of raffinose, and the detection limit was 0.5 pmol. Derivatization and analysis of raffinose was shown to yield reproducible results within the range 0.01–1 μmol, and, with special precautions to minimize losses, as little as 100 pmol could be analyzed successfully. 相似文献
940.
Day 6 1 2 -7 1 2 cow embryos were frozen in 1.4 M glycerol in PBS, at 0.3 degrees C/min to -30 (group I), -35 (group II), and -40 degrees C (group III) before being plunged into liquid nitrogen. They were subsequently thawed by direct transfer to water at 37 degrees C. In Experiment I, embryos frozen and thawed were cultured in vitro, 12 out of 19 embryos (63%) survived and there were no significant (p > 0.05) differences in survival rates among the three freezing groups. In Experiment II, 29 embryos frozen to -30 or -35 degrees C were transferred non-surgically to heifers on day 7. Seventeen of 29 recipients (59%) were pregnant at day 60. Five embryos frozen to -35 degrees C resulted in 5 pregnancies (100%) after thawing and surgical transfer. 相似文献