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21.
Chap T. Le 《Biometrical journal. Biometrische Zeitschrift》1988,30(1):87-92
The distribution-free test against ordered alternatives proposed by Jonckheere (1954) is based on the Kendall's rank correlation coefficient τ. A new rank test is proposed and illustrated with a numerical example. The proposed test is based on Spearman's σ and has similar functional structure as the Kruskal-Wallis test. A useful by-product is a test for departure from a trend. 相似文献
22.
23.
The effects produced on bacteriorhodopsin by low concentrations of several detergents have been studied by absorption and fourth-derivative spectrophotometry. Sodium dodecyl sulfate induces the appearance of the blue form of bacteriorhodopsin (λmax = 600 nm) at pH values up to 7.0 in a reversible manner. The apparent pK of the purple-to-blue transition raised with increasing concentration of SDS. Of the other detergents tested, only sodium dodecyl-N-sarcosinate showed a slight red-shift of the absorption band to 580 nm, whereas sodium taurocholate, Triton X-100 and cetyltrimethylammonium bromide did not favour the appearance of the blue form. The effect of SDS was found to be consistent with a localized conformational change that moves away the counter-ion of the protonated Schiff base. 相似文献
24.
Six bisindole alkaloids have been isolated from the leaves of Dyera costulata (Apocynaceae). One is the known ochrolifuanine A and the others are the novel ochrolifuanines E and F, and the 18-dehydroochrolifuanines A, E and F. 相似文献
25.
26.
Maria A. Papathanasopoulos Francois Krier Anne-Marie Revol-Junelles Gerard Lefebvre Jean Pierre Le Caer Alexander von Holy John W. Hastings 《Current microbiology》1997,35(6):331-335
Leuconostoc (Lc.) mesenteroides TA33a produced three bacteriocins with different inhibitory activity spectra. Bacteriocins were purified by adsorption/desorption
from producer cells and reverse phase high-performance liquid chromatography. Leucocin C-TA33a, a novel bacteriocin with a
predicted molecular mass of 4598 Da, inhibited Listeria and other lactic acid bacteria (LAB). Leucocin B-TA33a has a predicted molecular mass of 3466 Da, with activity against Leuconostoc/Weissella (W.) strains, and appears similar to mesenterocin 52B and dextranicin 24, while leucocin A-TA33a, which also inhibited Listeria and other LAB strains, is identical to leucocin A-UAL 187. A survey of other known bacteriocin-producing Leuconostoc/Weissella strains for the presence of the three different bacteriocins revealed that production of leucocin A-, B- and C-type bacteriocins
was widespread. Lc. carnosum LA54a, W. paramesenteroides LA7a, and Lc. gelidum UAL 187-22 produced all three bacteriocins, whereas W. paramesenteroides OX and Lc. carnosum TA11a produced only leucocin A- and B-type bacteriocins.
Received: 11 April 1997 / Accepted: 10 June 1997 相似文献
27.
Summary Lactic acid produced by continuous culture of L.casei in an upflow packed bed reactor, was recovered with Amberlite IRA 400 in a fluidized bed column. Bed expansions of 1.25 and 2.25 were applied. Reutilization did not alter the capability of net recovery of 0.048 ± 0.01 g lactic acid/g resin. When 2200 cm/h of ascensional velocity was used, (bed expansion of 2.25), the resin adsorbed 39.3% of the initial lactic acid and 63.5% was eluted. This resin supported the highest exchange capacity of 0.126 g lactic acid/g resin. Applying high flow rates, the process has potential industrial applications due to the short time employed. 相似文献
28.
W Niewiarowski Z J Le?nikowski A Wilk P Guga A Okruszek B Uznański W Stec 《Acta biochimica Polonica》1987,34(2):217-231
Diastereomers of the title compound were obtained and absolute configuration was assigned by means of stereochemical correlation. Their reaction with 3'-O-methoxyacetylthymidine in the presence of triisopropylbenzenesulphonyl (4-nitro) triazole is neither chemo- nor stereo-selective and leads to diastereomeric pairs of dithymidyl (3',5')methanephosphonate and -methanephosphonothioate. Obtained results are discussed in terms of mechanism of activation of phosphodiesters under conditions known as "phosphotriester approach to oligonucleotide synthesis". 相似文献
29.
The immobilization of penicillin G acylase on chitosan 总被引:3,自引:0,他引:3
30.
Mean square optical anisotropies and molar Kerr constants were calculated for homopolypeptides of the 20 natural amino acids and of several enzymes and proteins in the random-coil state. The effect of hydration was taken into account in constructing the molecular potential that gives the conformational energies as a function of the rotational angles phi and psi of the backbone and chi(1) of the side chain. The Rotational Isomeric State model was used in calculated energies, the Valence Optical Scheme and the matrix calculus technique of Flory being employed in the evaluation of the optical properties. The results are compared with calculations for the same substances that were performed without taking into account the solvent, as well as with other similar studies. The Kerr constant is confirmed as being one of the most sensitive properties of a given polypeptide to the residue class and to the sequence of those residues. 相似文献