Quantum-mechanical kinetic study of the primary reaction of the photochemical cycle of Halobacterium halobium

A two-frequency oscillator model for the primary photochemical reaction bacteriorhodopsin batho-bacteriorhodopsin (K₆₁₀) is proposed. According to this model two conformational changes in the reaction are considered to take place: the first one is a distortion of the retinal in the bacteriorhodopsin active site and the second one is a conformational transition of the bacterioopsin, affecting the native structure hydrogen bonds. On the basis of this model the temperature dependences of the rate constants for normal and deuterated reactants are calculated in good agreement with the available experimental data. The relations of the reaction considered to the primary photochemical reaction of vision are discussed.     

Physiological and biochemical contributions to the taxonomy of the genus prototheca

Five physiological and biochemical characters, which had proved to be valuable for the taxonomy of the genus Chlorella, were studied in the genus Prototheca. There is no hydrogenase activity and no liquefaction of gelatin. Most strains are very acidtolerant (limit of growth at pH 2.0 or 2.5) and very salt-tolerant (limit of growth at 4 or 5% NaCl). Two strains grow well at 38°C. The 16 strains, which were previously assigned to seven taxa, fall into four different groups. Our results tend to support the assumption that Prototheca might be related to Chlorella protothecoides.     

Spatial patterns in coupled biochemical oscillators

Summary The effects of diffusion on the dynamics of biochemical oscillators are investigated for general kinetic mechanisms and for a simplified model of glycolysis. When diffusion is sufficiently rapid a population of oscillators relaxes to a globally-synchronized oscillation, but when diffusion of one or more species is slow enough, the synchronized oscillation can be unstable and a nonuniform steady state or an asynchronous oscillation can arise. The significance of these results vis-a-vis models of contact inhibition and zonation patterns is discussed.     

Inheritance of three electrophoretically determined protein bands in potato (Solanum tuberosum L.)

Summary A modified polyacrylamide gel electrophoresis technique is employed to resolve proteins for use as biochemical gene markers in potato. Dominant, duplicate dominant and complementary gene action are three modes of inheritance that adequately explain the segregation of three respective protein bands in two generations of crossing within diploid Phureja X haploid Tuberosum families.Scientific Journal Seires Article 10,171 of the Minnesota Agricultural Experiment Station     

Characteristics of the Photosystem II reaction centre. II. Electron donors

The properties of Photosystem II electron donation were investigated by EPR spectrometry at cryogenic temperatures. Using preparations from mutants which lacked Photosystem I, the main electron donor through the Photosystem II reaction centre to the quinone-iron acceptor was shown to be the component termed Signal II. A radical of 10 G line width observed as an electron donor at cryogenic temperatures under some conditions probably arises through modification of the normal pathway of electron donation. High-potential cytochrome b-559 was not observed on the main pathway of electron donation. Two types of PS II centres with identical EPR components but different electron-transport kinetics were identified, together with anomalies between preparations in the amount of Signal II compared to the quinone-iron acceptor. Results of experiments using cells from mutants of Scenedesmus obliquus confirm the involvement of the Signal II component, manganese and high-potential cytochrome b-559 in the physiological process leading to oxygen evolution.     

Inhibition of DNA synthesis in permeabilized L cells by novobiocin

Novobiocin was equipotent in inhibiting DNA and RNA synthesis in cultured mouse L cells. It also suppressed in vitro DNA and RNA synthesis in permeabilized L cells and nuclei; 50 percent inhibition of DNA and RNA synthesis was obtained by 1 mM and 20 mM novobiocin, respectively. ATP antagonized the effect of novobiocin. Nalidixic acid had a weak inhibitory effect on in vitro DNA synthesis; 10 mM nalidixic acid showed 60 percent inhibition. ATP did not antagonize nalidixic acid. The inhibitory effect of novobiocin exceeded that of aphidicolin. These findings suggest a participation of a gyrase- and/or type II topoisomerase-like enzyme in the DNA replication machinery in L cells.     

Distribution of gangliosides in parenchymal and non-parenchymal cells of rat liver

Parenchymal and non-parenchymal cells were isolated from rat liver with purities of more than 90%. Total and ganglioside sialic acid contents were higher in non-parenchymal cells than in parenchymal cells. Thin-layer chromatography of gangliosides showed that the main component in rat liver was ganglioside GM3 and that this was abundant in non-parenchymal cells. Parenchymal cells had ganglioside GD1b as the main component and less GM3 than non-parenchymal cells. These results suggested that the main ganglioside of rat liver, GM3, arises mainly from non-parenchymal cells.     

外阴皮肤营养不良组织中人乳头瘤病毒DNA的检测

采用Southern Blot分子杂交方法检测了9例外阴皮肤营养不良组织中人乳头瘤病毒DNA的存在情况。结果显示8例增生型营养不良组织中,2例HPV-16阳性,1例HPV33阳性,在3例组织中探测到HPV16相关序列,在1例混合型中也检测到HPV16相关序例,HPV DNA的总检出率为77％。结果提示外阴皮肤营养不良的发生可能与HPV感染有关。     

Tissue distribution,metabolism, and elimination of perfluorooctanoic acid in male and female rats

The elimination, tissue distribution, and metabolism of [1-¹⁴C]perfluorooctanoic acid (PFOA) was examined in male and female rats for 28 days after a single ip dose (9.4 μmol/kg, 4 mg/kg). A sex difference in urinary elimination of PFOA-derived ¹⁴C was observed. Female rats eliminated PFOA-derived radioactivity rapidly in the urine with 91% of the dose being excreted in the first 24 hr. In the same period, male rats eliminated only 6% of the administered ¹⁴C in the urine. The sex-related difference in urinary elimination resulted in the observed difference in the whole-body elimination half-life (t_1/2) of PFOA in males (t_1/2 = 15 days) and females (t_1/2 < 1 day). Analysis of PFOA-derived ¹⁴C in tissues showed that the liver and plasma of male rats and the liver, plasma, and kidney of female rats were the primary tissues of distribution. The relatively high concentration of PFOA in the male liver was further examined using an in situ nonrecirculating liver perfusion technique. It was shown that 11% of the PFOA infused was extracted by the liver in a single pass. The ability of the liver to eliminate PFOA into bile was examined in rats whose renal pedicles were ligated to alleviate sex differences in the urinary excretion of PFOA. In a 6-hr period following IP administration of PFOA, there was no apparent difference in biliary excretion, where both males and females eliminated less than 1% of the PFOA dose via this route. We hypothesized that the sex difference in the persistence of PFOA was due to a more rapid formation of a PFOA-containing lipid (i.e., a PFOA-containing mono-, di-, or triacylglycerol, cholesteryl ester, methyl ester, or phospholipid) in the male rat. Also, the increased urinary elimination of PFOA in females may have been due to increased metabolism to a PFOA-glucuronide or sulfate ester. However, no evidence that PFOA is conjugated to form a persistent hybrid lipid was obtained, nor were polar metabolites of PFOA in urine or bile detected. In addition, daily urinary excretion of fluoride in male and female rats before or after PFOA treatment were similar, suggesting that the parent compound is not defluorinated. Thus, the more rapid elimination of PFOA from female rats is not due to formation of a PFOA metabolite.