Photosynthetic parameters of sexually different parts of Porphyra katadai var. hemiphylla (Bangiales, Rhodophyta) during dehydration and re-hydration

Physiological data from extreme habitat organisms during stresses are vital information for comprehending their survival. The intertidal seaweeds are exposed to a combination of environmental stresses, the most influential one being regular dehydration and re-hydration. Porphyra katadai var. hemiphylla is a unique intertidal macroalga species with two longitudinally separated, color distinct, sexually different parts. In this study, the photosynthetic performance of both PSI and PSII of the two sexually different parts of P. katadai thalli during dehydration and re-hydration was investigated. Under low-grade dehydration the variation of photosystems of male and female parts of P. katadai were similar. However, after the absolute water content reached 42%, the PSI of the female parts was nearly shut down while that of the male parts still coordinated well and worked properly with PSII. Furthermore, after re-hydration with a better conditioned PSI, the dehydrated male parts were able to restore photosynthesis within 1 h, while the female parts did not. It is concluded that in P. katadai the susceptibility of photosynthesis to dehydration depends on the accommodative ability of PSI. The relatively lower content of phycobiliprotein in male parts may be the cause for a stronger PSI after severe dehydration.

Characterizing a monotopic membrane enzyme. Biochemical, enzymatic and crystallization studies on Aquifex aeolicus sulfide:quinone oxidoreductase

Monotopic membrane proteins are membrane proteins that interact with only one leaflet of the lipid bilayer and do not possess transmembrane spanning segments. They are endowed with important physiological functions but until now only few of them have been studied. Here we present a detailed biochemical, enzymatic and crystallographic characterization of the monotopic membrane protein sulfide:quinone oxidoreductase. Sulfide:quinone oxidoreductase is a ubiquitous enzyme involved in sulfide detoxification, in sulfide-dependent respiration and photosynthesis, and in heavy metal tolerance. It may also play a crucial role in mammals, including humans, because sulfide acts as a neurotransmitter in these organisms. We isolated and purified sulfide:quinone oxidoreductase from the native membranes of the hyperthermophilic bacterium Aquifex aeolicus. We studied the pure and solubilized enzyme by denaturing and non-denaturing polyacrylamide electrophoresis, size-exclusion chromatography, cross-linking, analytical ultracentrifugation, visible and ultraviolet spectroscopy, mass spectrometry and electron microscopy. Additionally, we report the characterization of its enzymatic activity before and after crystallization. Finally, we discuss the crystallization of sulfide:quinone oxidoreductase in respect to its membrane topology and we propose a classification of monotopic membrane protein crystal lattices. Our data support and complement an earlier description of the three-dimensional structure of A. aeolicus sulfide:quinone oxidoreductase (M. Marcia, U. Ermler, G. Peng, H. Michel, Proc Natl Acad Sci USA, 106 (2009) 9625-9630) and may serve as a reference for further studies on monotopic membrane proteins. (C) 2010 Elsevier B.V. All rights reserved.

H5N1 avian influenza re-emergence of Lake Communication Qinghai: phylogenetic and antigenic analyses of the newly isolated viruses and roles of migratory birds in virus circulation

Highly pathogenic avian influenza H5N1 virus has swept west across the globe and caused serious debates on the roles of migratory birds in virus circulation since the first large-scale outbreak in migratory birds of Lake Qinghai, 2005. In May 2006, another outbreak struck Lake Qinghai and six novel strains were isolated. To elucidate these QH06 viruses, the six isolates were subjected to whole-genome sequencing. Phylogenetic analyses show that QH06 viruses are derived from the lineages of Lake Qinghai, 2005. Five of the six novel isolates are adjacent to the strain A/Cygnus olor/Croatia/1/05, and the last one is related to the strain A/duck/Novosibirsk/ 02/05, an isolate of the flyway. Antigenic analyses suggest that QH06 and QH05 viruses are similar to each other. These findings implicate that QH06 viruses of Lake Qinghai may travel back via migratory birds, though not ruling out the possibility of local circulation of viruses of Lake Qinghai.

力马河镍矿Re-Os同位素研究

四川力马河镍矿是峨眉山大火成岩省一个重要的岩浆硫化物矿床。本文通过对其主要岩、矿石类型Re、0s及其同位素组成的分析，综合探讨了成矿岩体原始岩浆性质、矿石硫化物成因、成矿机制及Re-Os同位素等时线年龄。结果表明，力马河镍不同类型岩矿石样品初始0s同位素组成是不均一的，富硫化物的网脉状矿石 及其选纯硫化物Os同位素组成初始值差异较小，其等时线年龄为265士35 Ma，与岩体错石SHRIMP年龄263士3Ma基本相当}硫化物含量较低的岩、矿石样品间初始Os同位素组成差异较大，其表观等时线年龄大于成矿年龄。分析认为。岩矿样品初始Os同位素组成的不均一是由含较高放射成因187Os丰度的硫化物熔体和含较低放射成因187Os丰度的硅酸盐熔体不同比例混合造成的。混合模型分析表明，硫化物含量超过3O％ 的矿石样品初始187 Os／188Os基本接近，硫化物含量低于3O ％的岩矿石样品初始 187Os／188Os随硫化物含量上的不同，差异很大，为岩浆硫化物矿床Re-Os等时线年龄出现多组年龄解的现象提供了一种可能的解释。成矿岩体中含放射成因187Os丰度最低的岩石样品 (t一260Ma)在5左右、Cu／Pd比值在7000左右，表明是基本没有受到地壳混染及硫化物熔离影响的原始岩浆结晶分异产物，估计原始岩浆Os含量在1×10 左右，为苦橄质岩浆。矿石硫化物Re／Os比值显著高于任何赋矿橄榄岩，7o,(￡一260Ma)高达110左右，综合分析揭示了力马河镍矿硫化物为二次熔离成因，模式分析认为，矿石硫化物是由原始岩浆经历R一2000左右的硫化物熔离后，其亏损岩浆再经R一200左右的硫化物熔离形成，与二次熔离相对应，成矿岩浆也经历了两次混染作用，分别为上、下地壳7％左右的混染。

粤北红岭钨矿中辉钼矿Re-Os同位素年代学及其地质意义

跃北红岭钨矿为产在热水复式岩体之中的中型钨多金属矿床, 矿化类型为石英脉型黑钨矿化和蚀变花岗岩型白钨矿化。对矿区含矿石英脉中8个辉钼矿样品进行Re-Os同位素测定, 获得等时线年龄及模式年龄的加权平均值分别为159.1±1.5Ma和158.8±0.88Ma. 等时线纵截距为-0.010±0.041, 说明样品中不存在可测定的初始187Os. 统计表明南岭地区中东段钨锡矿床的成矿年龄多集中在150~160Ma。粤北已有的几个钨矿成矿年龄与区域燕山期花岗岩大规模侵位时期一致，表明南岭地区花岗岩成岩成矿可能不存在明显的时差。