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31.
O dealkylation and aliphatic and aromatic hydroxylation of 3-methoxy-17 beta-estradiol by Aspergillus alliaceus. 下载免费PDF全文
Aspergillus alliaceus UI 315 was examined for its ability to metabolize 3-methoxy-17 beta-estradiol. Preparative-scale incubations with this substrate afforded good yields of 6 beta-hydroxy-17 beta-estradiol, 4-hydroxy-17 beta-estradiol, and 4,6 beta-dihydroxy-17 beta-estradiol, which were identified by high-pressure liquid chromatography, 1H and 13C nuclear magnetic resonance, and high-resolution mass spectrometry. 相似文献
32.
Multinuclear NMR studies of DNA hairpins. 1. Structure and dynamics of d(CGCGTTGTTCGCG) 总被引:9,自引:0,他引:9
The solution structure of the hairpin formed by d(CGCGTTGTTCGCG) has been examined in detail by a wide variety of NMR techniques. The hairpin was characterized by proton NMR to obtain interproton distances and torsion angle information. An energy-minimized model was constructed that is consistent with these data. The hairpin consists of a B-DNA stem of four C-G base pairs and a loop region consisting of five unpaired bases. Three bases in the 5' of the loop are stacked over the 3' end of the stem, and the other two bases in the 3' of the loop are stacked over the 5' end of the stem. The phosphorus NMR spectrum revealed a phosphate in the stem region with an unusual conformation, and two phosphates, P9 and P10, were found to undergo intermediate exchange between conformations. The hairpin was also synthesized with a carbon-13 label in each of the thymidine C6 carbons, and relaxation measurements were performed to determine the extent of internal motions in the loop region. The loop bases are more flexible than the stem bases and exhibit subnanosecond motions with an amplitude corresponding to diffusion in a cone of approximately 30 degrees. 相似文献
33.
Multinuclear NMR studies of DNA hairpins. 2. Sequence-dependent structural variations 总被引:4,自引:0,他引:4
The solution conformation of three related DNA hairpins, each with five bases in the loop, is investigated by proton and phosphorus 2D NMR methods. The sequences of the three oligomers are d(CGCGTTGTTCGCG), d(CGCGTTTGTCGCG), and d(CTGCTCTTGTTGAGCAG). One pair of hairpins shares the same stem sequence but differs in the loop, and the appearance of an unusual phosphate torsion in the stem is found to depend on the sequence in the loop of the hairpin. The second pair of hairpins shares the same loop region but differs in the stem sequence in that the base pair which closes the loop is a C-G or G-C pair. The pattern of NOEs reveals that the stacking arrangement in the loop region depends on the base pair that closes the stem. These results suggest that hairpin loop conformation and dynamics are sensitive to small changes in the loop and adjacent stem sequences. These findings are discussed in relation to sequence-dependent thermodynamic changes that have been observed in RNA hairpins. 相似文献
34.
Lidija Simova Carolyn Williams Georgi D. Efremov Aleksandra Gordova-Muratovska Stojka Suštić Eila K. Watson Robert Williamson 《Human genetics》1990,85(4):432-433
Summary Chromosomes from 19 unrelated Southern Yugoslav families in which cystic fibrosis (CF) occurs were analysed for the presence
of the ΔF508 mutation, using polymerase chain reaction amplification followed by dot blot and polyacrylamide gel analysis.
Of the 38 CF chromosomes, 15 (39.5%) carry the ΔF508 deletion. Restriction fragment length polymorphism haplotypes for KM19/PstI, XV2c/TaqI and J3.11/PstI marker loci were determined and are compared for a total of 34 N and 37 CF chromosomes. 相似文献
35.
D Williamson I J McLennan A Bax M P Gamcsik J D Glickson 《Journal of biomolecular structure & dynamics》1990,8(2):375-398
Two-dimensional NMR experiments--one bond 1H-13C correlation spectroscopy and heteronuclear multiple bond correlation spectroscopy, both performed in the reverse detection mode--have been employed to unambiguously assign all of the 13C resonances of the antibiotic bleomycin and its zinc(II) complex. Previous 1H resonance assignments of bleomycin (Chen et al. (1977) Biochemistry 16, 2731-2738) were confirmed on the basis of homonuclear Hartmann-Hahn and homonuclear COSY experiments. The 13C assignments differ substantially from those previously obtained by other investigators (Naganawa et al., (1977) J. Antibiot. 30, 388-396; Dabrowiak et al., (1978) Biochemistry 17, 4090-4096) but are in agreement with those reported by Akkerman et al. (1988) (Magn. Reson. Chem. 26, 793-802). The more recent study employed similar two-dimensional correlation experiments (performed in the direct detection mode) in conjunction with attached proton tests. Their study often required model compound data to identify carbonyls adjacent to aliphatic moieties. Previous 13C NMR studies of the structure, pH titration, and molecular dynamics of bleomycin and its zinc complex have been reinterpreted in terms of the revised assignments. 相似文献
36.
A H Carey S Roach R Williamson J P Dumanski M Nordenskjold V P Collins G Rouleau N Blin P Jalbert P J Scambler 《Genomics》1990,7(3):299-306
DiGeorge syndrome is a human developmental field defect with the pathological features of an abnormality of embryogenesis at 4 to 6 weeks of gestation. Cytogenetic analyses of patients have revealed a number of instances of monosomy 22q11-pter in this condition. We have analyzed 52 DNA markers that map to 22q11-pter and have found 27 that are deleted in DiGeorge syndrome patients with known monosomy for part of this region and that are duplicated in patients with the der22 syndrome. The set of clones mapping to the DiGeorge region was further assigned to a proximal or a distal location within the deletion. 相似文献
37.
J M Menter M E Townsel C L Moore G D Williamson B J Soteres M S Fisher I Willis 《Pigment cell research / sponsored by the European Society for Pigment Cell Research and the International Pigment Cell Society》1990,3(2):90-97
Although pigment melanin has long been though of as "inert," recent work has attested to its chemical reactivity. In this communication, we report that either commercial synthetic melanin prepared by persulfate oxidation of tyrosine ("Sigma melanin") or sepia melanin extracted from cuttlefish markedly accelerates the in vitro oxygenation of p-hydroxyanisole (MMEH), catalyzed by mushroom or B-16 melanoma tyrosinase. Kinetics of 4-methoxy-1,2-benzoquinone formation (lambda max = 413 nm) or of molecular O2 uptake were biphasic, with an initial slow rate ("lag time") followed by a fast linear increase. The biphasic response reflects an initial slow hydroxylation followed by a fast dehydrogenation. Added melanin markedly decreased the lag time but had little effect on subsequent dehydrogenation. Similar effects were observed for tyrosine itself. A complex between MMEH and melanin appears to be the "active" species in these reactions. The results indicate that melanin acts as an electron conduit, which accepts electrons from the substrate and transfers them to tyrosinase. The magnitude of the effect depends on the type of melanin as well as on its oxidation state. Kinetic analysis indicates that both melanins are very efficient at transferring electron to tyrosinase, and that Sigma melanin is roughly threefold more efficient than sepia melanin. The qualitative similarity of reaction between the synthetic and "natural" melanins suggests that the former may serve as a first approximation to the in vivo situation. On the other hand, the observed quantitative differences and the sensitivity of these results to the chemical state of melanin suggests that this methodology might eventually be adapted as a non-destructive probe of melanin in situ.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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