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11.
Mikkola S Oivanen M Neuvonen K Piitari S Ketomäki K Lönnberg H 《Nucleosides, nucleotides & nucleic acids》2000,19(10-12):1675-1692
Uridylyl-(3',5')-8-carboxymethylaminoadenosine has been synthesised, and its transesterification to uridine 2',3'-cyclic phosphate in the presence and absence of Zn2+ ion has been studied. The results show that a carboxylate function in the vicinity of the phosphodiester bond accelerates the metal ion promoted cleavage but not the metal ion independent reaction. Under acidic conditions, the predominant reaction is the cleavage of the side chain, giving the 8-amino derivative. 相似文献
12.
Elzagheid MI Mäki E Kaukinen U Oivanen M Lönnberg H 《Nucleosides, nucleotides & nucleic acids》2000,19(4):827-838
The hydrolytic reactions of the dimethyl ester of 3'-deoxy-3'-thioinosine 3'-S-phosphorothiolate have been followed over a wide aciditiy range by HPLC. At pH > 3, only hydroxide ion catalyzed isomerization to the 2'-dimethylphosphate takes place, whereas under more acidic conditions hydrolysis to the 2'-monomethylphosphate and 3'-S-monomethylphosphorothiolate competes. The latter is the only product accumulating in very acidic solutions (1 M hydrochloric acid). Mechanisms of the reactions are discussed. 相似文献
13.
The predilection muscles of Trichinella spiralis and T. nativa were studied in 2 experimental groups of 6 raccoon dogs (Nyctereutes procyonoides), the third group serving as a control for clinical signs. The infection dose for both parasites was 1 larva/g body weight.
After 12 weeks, the animals were euthanized and 13 sampling sites were analysed by the digestion method. Larvae were found
in all sampled skeleton muscles of the infected animals, but not in the specimens from the heart or intestinal musculature.
Both parasite species reproduced equally well in the raccoon dog. The median density of infection in positive tissues was
353 larvae per gram (lpg) with T. spiralis and 343 lpg with T. nativa. All the infected animals had the highest larvae numbers in the carpal flexors (M. flexor carpi ulnaris). Also tongue and eye muscles had high infection levels. There were no significant differences in the predilection sites
between these 2 parasite species. Trichinellosis increased the relative amount of fat, but not the body weight in the captive
raccoon dogs. Thus, Trichinella as a muscle parasite might have catabolic effect on these animals. 相似文献
14.
The hydrolytic stability of the S-(2-acetylthioethyl) (1a,b), S-(2-pivaloylthioethyl) (2a,b), and S-acetyloxymethyl (3a,b) protected Rp and Sp phosphoromonothiolates of 3',5'-TpT has been studied. Rather unexpectedly, an intramolecular hydroxide ion catalyzed acetyl migration from the protecting group to the nucleoside 3'- and 5'-hydroxy functions was found to compete with the intermolecular displacement of the AcSCH2CH2S- or AcOCH2S-ligand from the phosphorus atom of 1a,b and 3a,b, respectively. With the S-pivaloylthioethyl derivative 2a,b no such reaction took place. Additionally, the kinetics of the cleavage of the S-(2-mercaptoethyl) group from 4a,b, the products of enzymatic deacylation of 1a,b and 2a,b, were studied as a function of pH. 相似文献
15.
Mohamed Elzagheid Mikko Oivanen B. Colin N. M. Jones Richard Cosstick Harri Lönnberg 《Nucleosides, nucleotides & nucleic acids》2013,32(6-7):1265-1266
Abstract The pH-rate profiles (pH 0.2 to 9 at 90°C) for the competing hydrolytic reactions of (3′-deoxy-3′-thioinosylyl)-3′,5′-uridine (IspU) have been determined by an HPLC method. 相似文献
16.
Mikko Oivanen Harri Lönnberg Zygmunt Kazimierczuk David Shugar 《Nucleosides, nucleotides & nucleic acids》2013,32(1):133-144
Abstract A study has been made of a broad series of nucleosides and acyclonucleosides of a variety of benzimidazole analogues. Quantitative kinetic data are presented, and the mechanism of the reactions described, taking into account steric, electronic and conformational effects. The overall results are also compared with those of purine nucleosides. 相似文献
17.
G Remaud X X Zhou J Chattopadhyaya M Oivanen H L?nnberg 《Nucleic acids symposium series》1987,(18):145-148
Kinetics for the acidic hydrolysis of several N6-substituted 2'-deoxyadenosines were studied in a wide pH-range. The proportions of the partial reactions proceeding via mono- and di-protonated substrates were estimated on the bases of the rate profiles obtained and the acidity constants determined spectrophotometrically for the monocations. The site of the initial protonation was established by the effects that trifluoroacetic acid exerted on the 15N NMR chemical shifts. The exceptional lability of the monocations of N6-acyl protected compounds is suggested to result from the preferred N7 protonation. 相似文献
18.
Abstract Death-rate determinations indicated that a temperature a few tenths of a degree higher than Tmax was more deleterious to Klebsiella terrigena (ATCC 33257) than a somewhat higher temperature. The death rate at 40°C (Tmax + 0.5°C) was approximately 0.2 log units per h but about 0.01 log units per h between 42°C and 44°C. Sequential temperature-gradient and constant temperature incubations showed the same phenomenon qualitatively among 14 Enterobacteriaceae strains representing different species. 相似文献