Fermentation and isolation of C10-deacetylase for the production of 10-deacetylbaccatin III from baccatin III

10-Deacetylabaccatin III (10 DAB), an important precursor for paclitaxel semisynthesis, is enhanced in yew extracts using C10-deacetylase and C13-deacylase enzymes.(4) C10-deacetylase is an intracellular enzyme produced by the fermentation of a soil microorganism, Nocardioides luteus (SC 13912). During the fermentation of Nocardioides luteus, the growth of cells reaches a maximum growth at 28 h. C10-deacetylase enzyme activity starts at 26 h and peaks at 38 h of the fermentation. The cells are recovered by centrifugation. The C10-deacetylase enzyme was purified from the Nocardioides luteus cells. The enzyme was purified 190-fold to near homogeneity. The purified enzyme appeared as a single band on 12.5% SDS-PAGE analysis with a molecular weight of 40,000 daltons. (c) 1995 John Wiley & Sons, Inc.     

Herbicidal activity of phosphonic,phosphinic, and phosphonous acid analogues of phenylglycine and phenylalanine

A series of phosphonic, phosphinic, and phosphonous acid analogues of phenylglycine and phenylalanine was synthesized and tested as herbicides against Lepidium sativum and Cucumis sativus. Aminobenzylphosphonic acids exhibited notable herbicidal activity and thus represent a group of the most active herbicides found among aminophosphonic acids.     

Properties of acetylcholinesterase reconstituted in liposomes of a different charge

Acetylcholinesterase (AChE) purified from mouse brain was reconstituted in liposomes of a different charge, and the properties of liposome-associated AChE were investigated. Relative to the K_m value (38.5 M) of AChE bound to a neutral liposome, the value of AChE reconstituted in a negatively-charged liposome decreased to 23.3 M, whereas that of AChE in a positively-charged liposome increased to 90.9 M. Additionally, AChE bound to a positively-charged liposome expressed a wider range of optimum pH than the enzyme in a negatively-charged liposome. In a stability study, it was found that soluble AChE was unstable at pH 5.5 and 7.4, while it was relatively stable at pH 10. Noteworthy, the immobilization of AChE to liposome enhanced the stability of soluble enzyme at acidic and neutral pH. Moreover, in the stabilization of the enzyme, a neutral liposome was more effective than charged liposomes, of which a positively-charged liposome was more effective than a negatively-charged liposome at acidic pH. Based on these results, it is proposed that while the K_m value and the pH dependence of AChE activity are affected by the charge of liposome, the stability of AChE is determined mainly by a hydrophobic binding to a phospholipid membrane.This work was supported in part by Agency for Defense Development.     

Amino-modified silicate gels prepared by sol-gel processing as metal-ion sorbents

Two series of amino-modified silicate gels prepared by sol-gel processing were used to absorb Cu(II), Ni(II), Co(II), Mn(II) and Cr(III) from aqueous solutions. These easily prepared sorbents with various content of primary amino groups in series (A) or primary and secondary amino groups in series (AA) have reasonable stability. The gel composition, time and concentration dependence of the uptake of the metal ions by these materials were studied systematically. These materials would be further used as supports to disperse catalytically active phases by conventional wet chemical procedures. Apart from this they demonstrate potential for the preconcentration aid for transition metal analysis.     

MHC zygosity in the frog,Rana temporaria

The major histocompatibility complex (MHC) zygosity of the field-collected frogs, Rana temporaria, was detected by progeny testing. Groups of sibling tadpoles were grafted with intrafamilial tail-tip allografts and the ratio of rapidly rejected allografts to slowly rejected ones was estimated. Twenty-five percent of parental frogs appeared to be MHC homozygotes. Thus, MHC homozygosity in natural frog populations seems to be considerably higher than in wild mouse populations.     

Diversity concept in ecology

Hierarchy of systems organization is used as a framework in advancing methodological guidelines for posing correct questions related to ecological diversity.Diversity if defined in general terms as a property of a set of elements dependent on and determines: by the epistemological perspective. Ontological diversity, because it is indefinite, is regarded as unmeasurable.Ecological diversity — be it species, spatial, reproductive or trophic, is a particular case of diversity of matter and must be precisely defined on the studied level of system organization.Diversity measurements combining more than one level of organization are information-void, for data become irretrievable as a result of such a treatment.Hypotheses explaining diversity sources are briefly surveyed. An integrated model interrelating them is constructed as a result of some basic views on the structure of matter coupled with the empirical knowledge of involved factors. The model reflects hierarchies of systems, their dynamics, and the complexities of factors affecting diversity. The model's properties suggest that it is conceptually related to an imaginary model of organization of ecological systems. Parameters recognized as invariant components of this complexity are: habitat differentiation, ecological specialization of species, ambiental changes, and integration of this system.Finally, it is shown that the peculiar shape of the species abundances curve is a necessary consequence of stratification of the system structure, which is an intrinsic attribute of hierarchical organization.     

Chromatin proteins associated with micrococcal nuclease-sensitive and nuclease-resistant chromatin fractions of Kirkman-Robbins hepatoma and hamster liver

Micrococcal nuclease-sensitive (SP) and nuclease-resistant (PP) chromatin fractions from Kirkman-Robbins hepatoma and hamster liver were obtained. The molecular distribution of three non-histone proteins (NHCP1, NHCP2 and NHCP3), histones, and chromatin-bound protease activity between SP and PP fractions of both tissues was compared. Differences, mainly of quantitative nature, among non-histone proteins of neoplastic and normal tissue were observed. Moreover, it was found that polypeptides with mol. wt 81 000 (NHCP1), 39 000 (NHCP2) and 21 000, 35 000, 37 000 (NHCP1), 70 000, 112 000, 141 000, 157 000 (NHCP2), 30 000–33 000 (NHCP3) were associated only with the nuclease-sensitive part of chromatin of hepatoma and normal tissue, respectively. A major difference in histone compostion of hamster hepatoma and liver concerns histones H2A and H1. Furthermore, an enrichment of high mobility group proteins as well as other soluble non-histone proteins in an acid extract of the SP fraction was observed. Apparently chromatin-bound protease activity can be found in both fractions of chromatin.