Search results for "Mali"

Utilization of C14-glucose for amino acids and protein synthesis by the sea urchin embryo

1962

Penetrant diffusion in frozen polymer matrices: A finite-size scaling study of free volume percolation

1996

The diffusion of penetrant particles in frozen polymer matrices is investigated by means of Monte Carlo simulations of the bond fluctuation model. By applying finite-size scaling to data obtained from very large systems it is demonstrated that the diffusion process takes place on a percolating free volume cluster describable by a correlated site percolation model which falls into the same universality class as random percolation. The diverging correlation length entails a pronounced dependence of the diffusion constant on the size of the simulated system. It is shown that this dependence is appreciable for a wide range of parameters around the transition. \textcopyright{} 1996 The American …

Polydispersity and Molecular Weight Distribution of Hyperbranched Graft Copolymers via “Hypergrafting” of ABm Monomers from Polydisperse Macroinitiat…

2013

The hypergrafting strategy designates the synthesis of hyperbranched graft copolymers (HGCs) in a grafting-from approach, using ABm monomers, from multifunctional, polydisperse macroinitiator cores by slow monomer addition. Hypergrafting leads to complex polymer topologies with defined molecular weight, degree of branching (DB), and polydispersity (PD). By a generating function formalism, a generally applicable equation for the PD of HGCs (PD = PDf + (m – 1)/f) is derived, where PDf is the polydispersity of the core and f its average functionality. In addition, the complete molecular weight distribution function has been calculated for varied m and f as well as for a given distribution of i…

Low-temperature specific heat of orientational glasses

1992

This review summarizes specific heat data measured at low temperatures (T<1 K) on orientational glasses. Three species of mixed molecular crystals exhibiting orientational disorder are considered, namely (KBr)1−x (KCN) x , (NaCN)1−x (KCN) x (Rb)1−x (NH4) x H2PO4. For intermediate concentrations of the anisotropic components, glass-like excitations have been observed. It is demonstrated that with respect to thermal properties, orientational disorder leads to the same “universal” behaviours than for structural disorder, i.e. a specific heat which varies below 1 K and for times 10−4 s–10 s as:C p(T,t)∞T 1×ln(t). The variation of the glass-like anomaly with compositional disorder is also discus…

Enzymatic Biosynthesis of Vomilenine, a Key Intermediate of the Ajmaline Pathway, Catalyzed by a Novel Cytochrome P 450-Dependent Enzyme from Plant C…

1995

Abstract Microsomal preparations from Rauwolfia serpentina Benth. cell suspension cultures cata­lyze a key step in the biosynthesis of ajmaline -the enzymatic hydroxylation of the indole alkaloid vinorine at the allylic C-21 resulting in vomilenine. Vomilenine is an important branch-point intermediate, leading not only to ajmaline but also to several side reactions of the biosynthetic pathway to ajmaline. The investigation of the taxonomical distribution of the enzyme indicated that vinorine hydroxylase is exclusively present in ajmaline-producing plant cells. The novel enzyme is strictly dependent on NADPH2 and O2 and can be inhibited by typical cytochrome P450 inhibitors such as cytochrom…

Untersuchungen �ber die L-�pfels�ure-abbauenden Enzyme von Schizosaccharomyces acidodevoratus

1970

Der Abbau von L-Apfelsaure wird bei Schizosaccharomyces acidodevoratus von einer Malat-Dehydrogenase (EC 1.1.1.37) und einer Oxalacetat-Decarboxylase (EC 4.1.1.3) katalysiert. Stoffwechselprodukt ist Brenztraubensaure. Eine Pyruvat-Decarboxylase (EC 4.1.1.1) und Alkohol-Dehydrogenase (EC 1.1.1.1) wandeln die Brenztraubensaure in Alkohol und CO2 um. In einer Nebenreaktion entsteht Acetoin. Lactat-Dehydrogenase (EC 1.1.1.27) ist nicht nachweisbar.

Enzymatic biosynthesis of raumacline

1995

Abstract The indole alkaloid, raumacline, is biosynthesized from ajmaline, when the latter was fed to cell suspensions of Rauwolfia serpentina . Formation in catalysed by two enzymes, a cell wall-bound peroxidase followed by a NADPH 2 -dependent reductase. The first enzyme cleaves ajmaline oxidatively leading to a C-21 epimeric mixture of 21-hydroxyraumacline, a novel alkaloid, which, in turn, is reduced under formation of raumacline. The peroxidase reaction is not specific for Rauwolfia cells whereas the reductase is present exclusively in Rauwolfia cell suspensions. The reductase has been purified to homogeneity. The enzyme is highly substrate specific, only accepting 21-hydroxyraumacline…

Effect of Ti(IY) on some indicators of physiological activity inCapsicum annuum, L.

1994

SummaryPaprika pepper (Capsicum annuum, L., cv. Negral) plants grown in a greenhouse were supplied Ti(IV) ascorbate through the roots or through leaves. Biomass production, peroxidase (donor: H2O, oxidoreductase; EC 1.11.1.7) activity, and malic acid, starch and chlorophyll concentrations were determined in different plant organs. It was observed that Ti increased the concentration of some of the metabolites studied and promoted both peroxidase activity and biomass production. The profitable effect of the Ti treatments could occur because they enhance the availability of other nutrients. This effect could be due to the low redox potential of the Ti+3/Ti+4 system that catalyzes the activity …

Über den Abbau von L-Äpfelsäure durch Hefen verschiedener Gattungen mit Malatenzym

1974

Summary (1) The aerobic assimilation of malic acid is not a character of certain yeast genera or species as was shown by testing more than 300 different strains. Single strains of the following-species were found to grow on malic acid as the only carbon source: Candida pulcherrima, C. utilis, C. mycoderma, Torulopsis famata, Pichia membranaefaciens, P. wickerhamii, Hansenula capsulata, Trigonopsis variabilis , and Zygosaccharomyces chevalieri . (2) During fermentation C. pulcherrima and T. famata decompose up to 40% and C. utilis up to 80% of the L-malic acid that is present in the medium. (3) L-Malic acid is decomposed to CO 2 and the corresponding amounts of ethanol or pyruvate by cell fr…

Alkaloids from Rauwolfia serpentina cell cultures treated with ajmaline

1993

Abstract A group of new alkaloids, the raumaclines, and some related alkaloids were isolated from Rauwolfia serpentina cell suspensions fed with high levels of ajmaline; their structures were determined and syntheses developed providing an essential prerequisite to the further study of their biosynthesis at the enzymatic level.