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31.
凝血酶和ADP刺激血小板肌动蛋白的聚合,腺苷、5′-氯-5′-脱氧腺苷及2′-脱氧腺苷抑制凝血酶和(或)ADP诱导的肌动蛋白聚合;腺苷和5′-氯-5′-脱氧腺苷对磷脂酰肌醇的磷酸化有抑制作用,且呈剂量效应关系;腺苷对凝血酶刺激的血小板中肌醇二磷酸的生成有抑制作用。本实验提示腺苷及其类似物对肌动蛋白聚合的抑制作用可能与它们对肌醇磷脂转换的抑制有关。 相似文献
32.
Summary Conformationally restricted cyclic analogues of angiotensin II (ANG II), Asp1-Arg2-Val3-Tyr4-Val5-His6-Pro7-Phe8, with a link between positions 3 and 5 have considerable biological activity. It is proposed that the spatial arrangement of the pharmacophore groups of Tyr4, His6 and Phe8 side chains and the C-terminal carboxyl group in ANG II and active analogues is similar. Conformational analysis of ANG II and two cyclic analogues c[Sar1, Lys3,Glu5]ANG II and c[Sar1,Hcy3,Mpt5]ANG II was performed, and a geometrical comparison of the low-energy conformations of these compounds allowed one to propose a model of receptor-bound conformation in terms of the spatial arrangement of the pharmacophore groups. This model is characterised by the close spatial location of the His6-Phe8 side chains and the Tyr4 C-terminal carboxyl group and is stabilised by the electrostatic interaction of Arg2 and the C-terminal carboxyl group.Abbreviations ANG II
angiotensin II
- Hcy
homocysteine
- Mpt
trans-4-mercaptoproline 相似文献
33.
The expansion of crop lands and increased logging for charcoal production in the Brazilian savannahs (cerrados) has reduced richness and abundance of Meliponini bees. This may be a consequence of limitation in the availability of potential nesting substrate. The role of a cerrado-tree (Caryocar brasiliense) in providing nesting substrate for Melipona quadrifasciata quadrifasciata was evaluated. Tree (p= 0.006) and branch (p= 0.001) diameters, number of suitable branches (n= 513), height of the trees and availability of trees suitable for bee nesting were all important to the conservation of M. quadrifasciata. However, the high availability of nesting substrate did not seem to limit nest density nor cause the clumped pattern of nest distributions found for the study site. Nests (n= 48) were found mainly in individuals of C. brasiliense (n= 46) suggesting an active tree selection. In addition, nests located on the highest branches (mean = 4.6 m, sd = 1 m, n= 46) had lower probability of being extirpated by human honey collectors. 相似文献
34.
Leixiang Yang Jingxu Gong Feng Wang Yongmin Zhang Yanguang Wang Xiaojiang Hao 《Journal of enzyme inhibition and medicinal chemistry》2013,28(4):399-404
In this work, we evaluated the antioxidant properties of the eight novel silybin analogues for their capacity to scavenge free radicals including superoxide anion radicals and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals in vitro. Compound 7d demonstrated an excellent antioxidant effect in scavenging superoxide anion free radical with an IC50 value of 26.5 μM, while the IC50 of quercetin (the reference compound) was 38.1 μM. Compounds 7b, 7e, 7h showed certain scavenging activities for both types of free radicals. 相似文献
35.
Ken-Ichi Nunami Mamoru Suzuki Kazuo Matsumoto Naoto Yoneda Kazuo Takiguchi 《Bioscience, biotechnology, and biochemistry》2013,77(4):1073-1075
We investigated GroEL substrates from Bacillus subtilis 168 using the single-ring mutant of B. subtilis GroEL. We identified 28 candidates for GroEL substrates, of which Spo0B, Ald, Eno, SpoIIP, and FbaA were involved in spore formation, and Rnc, Tuf, Eno, Tsf, and FbaA were essential for B. subtilis growth. As observed at the protein level, the amount of SpoIIP interaction with GroEL increased at 3 h after initiation of sporulation. 相似文献
36.
Factor XIII-mediated cross-linking of NH2-terminal peptide of alpha 2-plasmin inhibitor to fibrin 总被引:1,自引:0,他引:1
The NH2-terminal 12-residue peptide of alpha 2-plasmin inhibitor, Asn-Gln-Glu-Gln-Val-Ser-Pro-Leu-Thr-Gly-Leu-Lys-NH2 . AcOH, was found to be a good substrate for plasma transglutaminase (activated blood coagulation factor XIII) and rapidly incorporated into fibrin by the enzyme. A high concentration of the peptide inhibited the enzyme-mediated cross-linking of alpha 2-plasmin inhibitor to fibrin probably by competing with the inhibitor for the same site of fibrin alpha-chain. 相似文献
37.
Kazumi Funane Nathalie Libessart Douglas Stewart Toru Michishita Jack Preiss 《The protein journal》1998,17(7):579-590
Incubation of maize branching enzyme, mBEI and mBEII, with 100 μM diethylpyrocarbonate (DEPC) rapidly inactivated the enzymes.
Treatment of the DEPC-inactivated enzymes with 100–500 mM hydroxylamine restored the enzyme activities. Spectroscopic data
indicated that the inactivation of BE with DEPC was the result of histidine modification. The addition of the substrate amylose
or amylopectin retarded the enzyme inactivation by DEPC, suggesting that the histidine residues are important for substrate
binding. In maize BEII, conserved histidine residues are in catalytic regions 1 (His320) and 4 (His508). His320 and His508
were individually replaced by Ala via site-directed mutagenesis to probe their role in catalysis. Expression of these mutants
inE. coli showed a significant decrease of the activity and the mutant enzymes hadK
m values 10 times higher than the wild type. Therefore, residues His320 and His508 do play an important role in substrate binding. 相似文献
38.
Distamycin and netropsin are two oligopeptides which bind to DNA in a nonintercalative manner. Analogues of distamycin have
been synthesized and their binding with poly d(A-T) studied using ultraviolet absorption spectroscopy. Preliminary biological
activity tests on a gram positive bacteria using these analogues have also been carried out
Based on the lecture given by Dr. V. Sasisekharan at the Royal Society of Chemistry (Deccan Section) Bangalore, 26 June 1984. 相似文献
39.
《Process Biochemistry》2014,49(3):365-373
A three-stage control strategy independent of the organic substrate was developed for automated substrate feeding in a two-phase fed-batch culture of Cupriavidus necator DSM 545 for the production of the biopolymer polyhydroxybutyrate (PHB). The optimal feeding strategy was determined using glucose as the substrate. A combined substrate feeding strategy consisting of exponential feeding and a novel method based on alkali-addition monitoring resulted in a maximal cell concentration in the biomass growth phase. In the PHB accumulation phase, a constant substrate feeding strategy based on the estimated amount of biomass produced in the first phase and a specific PHB accumulation rate was implemented to induce PHB under limiting nitrogen at different biomass concentrations. Maximal cell and PHB concentrations of 164 and 125 g/L were obtained when nitrogen feeding was stopped at 56 g/L of residual biomass; the glucose concentration was maintained within its optimal range. The developed feeding strategy was validated using waste glycerol as the sole carbon source for PHB production, and the three-stage control strategy resulted in a PHB concentration of 65.6 g/L and PHB content of 62.7% while keeping the glycerol concentration constant. It can thus be concluded that the developed feeding strategy is sensitive, robust, inexpensive, and applicable to fed-batch culture for PHB production independent of the carbon source. 相似文献
40.
《Nucleosides, nucleotides & nucleic acids》2013,32(5-8):623-627
Abstract Preparation of the nucleoside analogues 1 and incorporation of 1, B = T, in deoxyribooligonucleotides by the phosphoramidite method is described. A two-step deprotection procedure was developed to reduce cleavage of the modified allylic unit. The binding properties of the modified oligonucleotides towards complementary DNA and RNA has been evaluated by Tm measurements showing a ΔTm of ?2 to ?6.5°C per modification. An oligonucleotide with two modifications at the 3′-end showed considerable resistance towards cleavage by a 3′-exonuclease. No antiviral activity against HIV-1 or HSV-1 was found for 1, B = G or T, or for any of the trihydroxy derivatives 5. 相似文献