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New reactive coenzyme analogues for affinity labeling of NAD+ and NADP+ dependent dehydrogenases
(1995)
Reactive coenzyme analogues ω-(3-diazoniumpyridinium)alkyl adenosine diphosphate were prepared by reaction of ω-(3-aminopyridinium)alkyl adenosine diphosphate with nitrous acid. In these compounds the nicotinamide ribose is substituted by hydrocarbon chains of varied lengths (n-ethyl to n-pentyl). The diazonium compounds are very unstable and decompose rapidly at room temperature. They show a better stability at 0 °C. L actate and alcohol dehydrogenase do not react with any of the analogues. Glyceraldehyde-3-phosphate dehydrogenase reacts rapidly with the diazonium pentyl compound. Decreasing the length of the alkyl chain significantly decreases the inactivation velocity. 3α,20β-Hydroxysteroid dehydrogenase reacts at 0 °C with the ethyl homologue and slowly with the propyl compound. The butyl-and pentyl analogues do not inactivate at 0 °C. Tests with 14C -labeled 2-(3-diazoniumpyridinium)ethyl adenosine diphosphate show that complete loss of enzyme activity results after incorporation of 2 moles of inactivator into 1 mole of tetrameric enzyme. 4-(3-Acetylpyridinium)butyl 2 ′-phospho-adenosine diphosphate, a structural analogue of NADP +, was prepared by condensation of adenosine-2,3-cyclophospho-5′-phosphomorpholidate with (3-acetylpyridinium)butyl phosphate, followed by hydrolysis of the cyclic phosphoric acid ester with 2 ′:3′-cyclonucleotide-3′-phosphodiesterase. Because of the redox potential (-315 mV) and the distance between the pyridinium and phosphate groups, this analogue is a hydrogen acceptor and its reduced form a hydrogen donor in tests with alcohol dehyd rogenase from Thermoanaerobium brockii. The reduced form of the coenzyme analogue also is a hydrogen donor with glutathione reductase. With other NADP +-dependent dehydrogenases the com pound has been show n to be a competitive inhibitor against the natural coenzyme. The acetyl group reacts with bromine to form the bromoacetyl group. This reactive bromoacetyl analogue is a specific active-site directed irreversible inhibitor of isocitrate dehydrogenase.
Metaleptea, vol. 16, no. 1, july 1995 : the orthopterists' newsletter / The Orthoperists' Society
(1995)
Early features
(1995)
In LaPolla 1990, I presented arguments to show that Chinese is a language in which there has been no grammaticalizalion of the syntactic relations "subject" and "object". This being the case, then syntactic relations cannot be what determines word order in Chinese. In this paper I will argue that, aside from a semantic rule that the actor of a verb, if expressed, must precede that verb, it is pragmatic relations (information structure) that are the main determinants of word order in Chinese.
Mosses new to Hong Kong (4)
(1995)
Sixteen moss species - Eurhynchium asperisetum (C. Muell.) Tak.; Rhynchostegium pallidifolium (Mitt.) Jaeg.; Bryum argenteum Hedw.; Bryum caespiticium Hedw.; Bryum capillare Hedw.; Platyhynidium riarioides (Hedw.) Dix.; Dicranella varia (Hedw.) Schimp.;Entodon virudulus Card.; Fissidens strictulus C. Muell.; Ectropothecium obtusulum (Card.) Iwats.; Caduciella guangdongensis Enroth.; Plagiomnium cuspidatum (Hedw.) T. Kop.; Plagiomnium vesicatum (Besch.) T. Kop.; Pyrrhobryum spiniforme (Hedw.) Mitt., Taxithelium nepalense (Schwaegr.) Broth. and Claopodium aciculum (Broth.) Broth. are reported new to Hong Kong. Among them, four are new to Guangdong Province of China.
Chromosome numbers with information on meiotic behaviour are recorded for the first time for the following taxa in the family Orthotrichaceae from Papua New Guinea - Desmotheca apiculata (Dozy & Molk.) Lindb. ex Card. n=6; Macromitrium incurvifolium (Hook. & Grev.) Schwaegr. n=9, M. longicaule C. Muell. n=6 (5+X/y), M. orthostichum Nees ex Schwaegr. n=7 (6+ X/y), M. salakanum C. Muell. n=9, M. similirete Bartr. n=9. M. streimannii Vitt n=9 (8+m); Schlotheimia emarginato-pilosa Herz. n=9 and S. macgregorii Broth. & Geh. n=11.
Studies of epiphyll ecology have been hindered by the biochemical and morphological variability of the leaf substrate. The use of artificial (plastic ribbon tape) leaves solved that problem in a study done at the Braulio Carrillo National Park, Costa Rica. It showed that after nine months of field exposure, relative epiphyll cover was similar in five leaf shapes and two sizes. Driptips do not affect epiphyll cover, which was four times higher under a clearing than in the shaded understory, for all leaf shapes and sizes.
Niche breadth and overlap values of Sphagnum species in Costa Rica are similar to those reported for Sphagnum-dominated peatlands in North America. Sphagnum magellanicum Brid. and S. sparsum Hampe have the broadest niche breadth of the common species in Costa Rica. Although S. sancto-josephense Crum & Crosby has a relatively narrow niche breadth, it is one of the most common species along with S. magellancium and S. sparsum in the Sphagnum habitats of Costa Rica. Niche overlap is high among species with the exception of S. platyphyllum (Braithw.) Warnst. which is found in habitats that are rich in iron. The pH, conductivity, and concentrations of Ca, Fe, Mg, Mn, Na, K, and P of Sphagnum habitats in Costa Rica are similar to those reported for páramo habitats in South America.
Life strategies of epiphytic bryophytes are studied along an altitudinal gradient from the eastern Congo basin (tropical lowland zone) to the mountains of the East-African graben (tropical subalpine/alpine Zone; BRYOTROP III-transect). Three strategies, Colonists, Perennial shuttle species and Perennial stayers can be observed, which are further subdivided according to their reproduction tactic (high sexual reproductive effort, high asexual reproductive effort, moderately or low sexual and asexual reproductive effort). Of these, only taxa with a long life span (perennials) are of importance, indicating the unchanging and constant ecological conditions and long-lasting microsites, provided by the epiphytic habitats. The basis for the life strategy pattern analysis along the altitudinal gradient were plant sociological investigations and the determination of the mean percentage cover values for the different life strategy categories. By this, the distribution and occurrence of the different strategies within the communities and the altitudinal zones can be shown.