Protection of photosynthetic O2 evolution against heat inactivation: the role of chloride,pH and coupling status

Heat inactivation of photosynthetic O₂ evolution was studied in isolated thylakoids from spinach (Spinacia oleracea) and mangrove (Avicennia marina) leaves. Different temperatures, salt, pH and uncoupler effects were investigated. From these results and others in the literature it was concluced that chloride loss from the membrane and, more specifically, the oxygen-evolving complex of photosystem II, may be the cause of inhibition of oxygen evolution during heat inactivation.Abbreviations Hepes 4-(2-hydroxyethyl)-1-piperazinethanesulfonic acid - Tris 2-amino-2-(hydroxymethyl)-1,3-propanediol - Tricine N-2-hydroxy-1, 1-bis (hydroxymethyl) ethyl glycine - EDTA ethylenediaminetetraacetic acid - FeCN K-ferricyanide     

Polymorphisms and deduced amino acid substitutions in the coding sequence of the ryanodine receptor (RYR1) gene in individuals with malignant hyperthermia.

Twenty-one polymorphic sequence variants of the RYR1 gene, including 13 restriction fragment length polymorphisms (RFLPs), were identified by sequence analysis of human ryanodine receptor (RYR1) cDNAs from three individuals predisposed to malignant hyperthermia (MH). All RFLPs were detectable in PCR-amplified products, and their segregation was consistent with our initial finding of linkage to MH in the nine families previously informative for one or more intragenic markers (MacLennan et al., 1990, Nature 343:559-561). Four amino acid substitutions were identified in the study: Arg for Gly248, Cys for Arg470, Leu for Pro1785, and Cys for Gly2059. Of 45 families tested, a single family presented the Arg for Gly248 substitution where it segregated with malignant hyperthermia, making it a candidate mutation for predisposition to MH in man. The other three polymorphic substitutions failed to segregate with malignant hyperthermia in those families in which they occurred, implying that they represent polymorphisms with little or no effect on the function of the RYR1 gene.     

Effect of polyols on the thermostability of pullulan-hydrolysing activity from Sclerotium rolfsii

Summary The influence of various polyols on the thermostability of pullulan-hydrolysing activity fromSclerotium rolfsii was studied. The half-life of the enzyme activity at 60°C was determined to be of the order of 30 min. In the presence of xylitol and sorbitol (3 M or more) there was a significant enhancement in the thermostability of the enzyme with retention of 100% activity after incubation for 7 h at 60°C. However, ethylene glycol and glycerol were found to have no protective effect. The stabilizing efficiency was found to be dependent on the concentration of the polyhydric alcohol used and the number of OH-groups present per molecule.     

Computational study of radiation chemical processing in comet nuclei

Cometary nuclei have been exposed to high levels of ionizing radiation since their formation. We present here some results of a computer model calculation of the effect of ionizing radiation on cometary material. The external (cosmic rays) and internal (embedded radionuclides) contributions in the processing of cometary nuclei are considered. As a first approximation we have used the available kinetic data of the liquid water system to model the radiation effects in a frozen cometary environment. Out data suggest that massive radiation chemical processing due to cosmic rays may have taken place only in the outer layers of comets. The internal contribution of radionuclides to the radiation processing of comet cores seems to be modest. Therefore, comets could be carriers of intact homochiral biomolecules.Part of this work was carried out during a leave at the Laboratory of Chemical Evolution.     

Serum protein polymorphisms (HP,GC, PI) in Muslims and Bodhs of Jammu and Kashmir,India

Two population groups of Jammu and Kashmir (India) — Muslims and Bodhs-have been typed for haptoglobin and for CG and PI subtype polymorphisms. The allele frequencies do not show significant differences between these two populations. HP and GC allele frequencies of Bodhs and Muslims differ considerably from with that observed in other North Indian populations. The PI allele frequencies of Bohds and Muslims differ considerably from those found in other Indian populations and are more similar to Mongoloid ones.     

Methane recovery from water hyacinth through anaerobic activated sludge process

The concepts of phase separation, anaerobic activated sludge process, and alkali pretreatment have been incorporated in this investigation with the objective of developing rational and cost-effective designs of diphasic anaerobic activated sludge systems, with and without alkali treatment, for methane recovery from water hyacinth (WH). Evaluation of process kinetics and optimization analyses of laboratory data reveal that a diphasic system with alkali treatment could be designed with an alkali pretreatment step (3.6% Na(2)CO(3) + 2.5% Ca(OH)(2) (w/w) of WH, 24 h duration) followed by an open acid phase (2.1 days HRT) and closed methane reactor with sludge recycle (5.7 days HRT, 7.7 days MCRT) for gas yield of 50 L/kg WH/d at 35-37 degrees C. Likewise, a diphasic system without alkali treatment could be designed with an open acid phase (2 days HRT) followed by closed methane reactor with sludge recycle (3.2 days HRT, 6 days MCRT) for gas yield of 32.5 L/kg WH/d at 35-37 degrees C. Detailed economic analyses bring forth greater cost-efficacy of the diphasic system without alkali treatment and reveal that the advantage accrued in terms of higher gas yield is overshadowed by the cost of chemicals in the diphasic system with alkali treatment.     

Phosphorylation of lipocortins in vitro by protein kinase C

Protein kinase C catalyzes the incorporation of about 1.1, 0.7 and 0.4 mole of phosphate per mole of Lipocortin-I (P35), Lipocortin-II (P36) and Lipocortin-85 (P36 oligomer) respectively. The phosphorylation is specific for protein kinase C and is dependent on the presence of both calcium and phospholipids. While Lipocortin-I is phosphorylated on threonine residues, Lipocortin-II and Lipocortin-85 are phosphorylated on serine residues. The substoichiometric phosphorylation of Lipocortin-85 appears to preclude the potential regulation of this protein by protein kinase C. The phosphorylation of Lipocortin-I on threonine residues and Lipocortin-II on serine residues suggests these proteins may be regulated by distinct phosphorylation-dephosphorylation reactions.     

Lipids of Cuscuta reflexa and changes in lipids of its host plants after infection

The lipid level (fresh weight basis) of Cuscuta reflexa Roxb. was related to the lipid content of the host plants Meilicago saliva L., Helianthus annuus L., Pisum sativum L. and Lantana camara L. Parasitizing by the dodder significantly increased the total lipid level of the hosts. The increase was mainly due to enhancement in the neutral lipid fraction.
The level of phospholipid in the parasite was always higher than in its hosts. Phospholidyl choline and phosphatidyl ethanolamine constituted about 65% of the total phospholipid of Cuscuta. This was followed by phosphatidyl inositol (ca 20%) and phosphatidyl glycerol (ca 12%). Phosphatidic acid constituted only ca 3% of the phospholipids of Cuscuta. Although the total phospholipid levels of various host plants were not affected as a result of the infection by Cuscuta, a significant decrease occurred in the levels of phosphatidyl eholine and phosphatidyl ethanolamine as well as marked increases in phosphatidyl inositol and phosphatidic acid. The infected tissue showed an increase in phospholipase D activity as compared with the controls. The results have been discussed in relation to changes in permeability of the infected tissue.     

Effects of fertilization and liming on the chemical soil conditions and element distribution in forest soils

Summary The distribution and storage of major elements in acid soils from a spruce and a beech forest was investigated after fertilization of NH₄NO₃ and KCl followed by Ca and Mg fertilization by 2 liming applications. All fertilizers were applied on top of the soil without mixing. Most of the added Ca and Mg was detected in the humus layer, a significant part of it still in carbonatic form. The effect of liming on mineral soil pH is very low, and was only observed in the 0–10 cm layer. However, base saturation of the mineral soil increased. The storage of C and N of the humus layer was not affected. N fertilization increased the N storage of the soil only under beech, but was followed by heavy NO₃-losses with seepage water under spruce. High leaching rates for K were also found in the spruce stand. The amount of K that was not leached increased the pool of exchangeable K in the deeper soil layer.