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41.
42.
Stereospecific hydroxylation of 3-deoxy-1,2:5,6-di-O-isopropylidene-3-C-trans-and 3-C-cis-(methoxycarbonylmethylene)-α-D-ribo-hexofuranose (2 and 3, respectively), with potassium permanganate in pyridine afforded 3-C-[S- and R-hydroxy-(methoxycarbonyl)methyl]-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose, (6 and 7, respectively), in a combined yield, after chromatography, of 43%. Selective formation of monomethanesulfonates (9a and 10a) and p-toluenesulfonates (9b and 10b), followed by treatment with sodium azide and reduction of the azide, afforded the methyl 2-D-(and 2-L-)(3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-glucofuranos-3-yl)-glycinates (12a and 13a, respectively). Basic hydrolysis of the latter compounds yielded 2-D- and 2-L-(3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-glucofuranos-3-yl)glycine (12b and 13b, respectively). The structures of the glycosyl amino acids were correlated with that of L-alanine by circular dichroism. 相似文献
43.
Specific reduction of carboxyl groups in peptides and proteins by diborane 总被引:1,自引:1,他引:0
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1. The reaction of several peptides and proteins with diborane was studied under different conditions to determine those most suitable for the specific reduction of carboxyl groups. 2. In the reaction of model peptides and the cyclic peptides bacitracin and tyrocidin, reduction at 0 degrees was entirely specific for the carboxyl groups without affecting the peptide bonds. Acid amide residues were not reduced. Some tripeptides showed anomalous results in that the C-terminal residue was quite resistant to reduction. 3. Specific reduction of carboxyl groups was achieved in each of the following proteins: human serum albumin, egg albumin, adult human haemoglobin, sperm-whale apomyoglobin, horse heart cytochrome c and egg-white lysozyme. The C-terminal amino acid was usually reduced. 4. Conditions for specific reduction of all available carboxyl groups are not easily found and may vary from one substance to another. Specific reduction of a limited number of available carboxyl groups may be generally accomplished by reactions at -10 degrees . 5. It is suggested that this chemical modification, which has the advantage of permanence, may be useful in studying the role of carboxyl groups in the conformation of proteins and in the biological properties of peptides and proteins. 相似文献
44.
Effect of Lytic Enzymes of Acanthamoeba castellanii on Bacterial Cell Walls 总被引:3,自引:0,他引:3
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Extracts of Acanthamoeba castellanii (Neff) contain alpha- and beta-glucosidase, beta-galactosidase, beta-N-acetylglucosaminidase, amylase, and peptidase. All of these activities are optimal between pH 3 and 4. These extracts also were found to clarify suspensions of cell walls from nine different gram-positive bacteria, including Micrococcus lysodeikticus. The pH optimum for the lytic activity was between 3 and 4. The extent of lysis of the various cell walls did not correlate with the release of free amino groups and of free N-acetylated sugars from the walls during digestion with these extracts. Suspensions of cell walls of Escherichia coli (a gram-negative bacterium), Cordiceps militaris (a fungus), and Acanthamoeba cysts, as well as of colloidal chitin, were not clarified by incubation with these extracts, although reducing sugars were released from each of these materials. Exhaustive digestion of M. lysodeikticus walls by lysozyme released no free N-acetylglucosamine. The products of exhaustive digestion of this cell wall with Acanthamoeba extracts were free N-acetylglucosamine, free N-acetylmuramic acid, glycine, alanine, glutamic acid, lysine, and N-acetylmuramic acid peptide fragments. These results suggest that the amoeba extracts contain endo- and exo-hexosaminidases, in addition to beta-hexosaminidase and peptide hydrolases. 相似文献
45.
H. Rosenthal 《Helgoland Marine Research》1970,21(3):320-332
Zusammenfassung 1.Belone belone L. wurde von der künstlichen Befruchtung an bis zu einer Totallänge von annähernd 10 cm unter kontrollierten Laborbedingungen aufgezogen.2. Dottersacklarven zeigten unter verschiedenen Lichtbedingungen Igelstellungen, die in Anlehnung anMagnus (1967) als Fluchtintensionsbewegung interpretiert werden.3. Die Beutefanghandlungen erreichen schon zur Zeit der ersten Nahrungsaufnahme eine außerordentlich hohe Anfangstreffsicherheit.4. Larven und Jungfische nehmen Kunstfutter sehr gut von der Oberfläche her auf.5. Bei Totallängen zwischen 16 und 25 mm neigen die Jungfische besonders stark zum Kannibalismus.6. Die mit 12,5 mm Totallänge schlüpfenden Larven wuchsen bei 22° C in den ersten 14 Tagen im Mittel bis auf 29 mm, innerhalb von 35 Tagen auf 45 mm und in 80 Tagen auf etwa 93 mm heran. Bei einer Aufzuchttemperatur von 26° C wurden 90 mm Totallänge bereits nach 60 Tagen erreicht.7. Die Überlebensrate betrug während der Dottersackphase und zur Zeit der ersten Nahrungsaufnahme annähernd 100%. Die durch Kannibalismus verursachte Sterblichkeit erreichte mehr als 60%. Erhebliche Verluste wurden dabei sekundär durch Pilzinfektionen und parasitäre Ciliaten verursacht.
Feeding and growth of larvae and fry of the gar fishBelone belone
Artificially fertilizedBelone belone L. were reared under controlled conditions in the laboratory to a maximum total body length of approximately 10 cm. Percentage of successful prey catching (Artemia nauplii, Cyclopidae) attained high values already at the time when the larvae started to feed. Larvae and fry readily ingested dried food (tetramin, freeze-dried Daphnia) from the surface of the water. Fry of 16 to 25 mm total length exhibited intensive cannibalism. The larvae hatched at an average total length of 12.5 mm and attained a total length of 29 mm after the first 14 days at 22° C. Thirty-five days after hatching, average length had increased to 45 mm; after 80 days it averaged 93 mm. At 26° C, the fishes attained an overall length of 90 mm after 60 days. Survival was almost 100% in the 5 day period following hatching. After yolk absorption and first food intake, cannibalism occurred; it resulted in more than 60% mortality within the next 2 week period. Later causes of mortality were fungal infections, partly associated with injuries resulting from cannibalistic behaviour.相似文献
46.
Mutant male strains with an altered nucleic acid pump 总被引:3,自引:0,他引:3
47.
48.
Chr Rosenthal 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1965,34(8):316-324
Ohne ZusammenfassungMit 4 Abbildungen 相似文献
49.
An arginase, purified from the leaf of the jack bean, Canavalia ensiformis, can effectively hydrolyze both l- and d-arginine. Arginases, examined from a number of other plant and animal sources, exhibit marked substrate stereospecificity and fail to catabolize d-arginine. In order to provide essential nitrogen, jack bean leaf arginase also catabolizes l-canavanine, an arginine analog that is a predominant nitrogen-storing metabolite of this legume. The ability of arginase to metabolize both stereoisomers of arginine may result from the requirement for this enzyme to exhibit limited substrate specificity in order to hydrolyze both arginine and canavanine. 相似文献
50.