Rapidly reversible chlorophyll fluorescence quenching induced by pulses of supersaturating light in vivo

The saturation pulse method provides a means to distinguish between photochemical and non-photochemical quenching, based on the assumption that the former is suppressed by a saturating pulse of light (SP) and that the latter is not affected by the SP. Various types of non-photochemical quenching have been distinguished by their rates of dark relaxation in the time ranges of seconds, minutes, and hours. Here we report on a special type of non-photochemical quenching, which is rapidly induced by a pulse of high-intensity light, when PS II reaction centers are closed, and rapidly relaxes again after the pulse. This high-intensity quenching, HIQ, can be quantified by pulse-amplitude-modulation (PAM) fluorimetry (MULTI-COLOR-PAM, high sensitivity combined with high time resolution) via the quasi-instantaneous post-pulse fluorescence increase that precedes recovery of photochemical quenching in the 100–400-µs range. The HIQ amplitude increases linearly with the effective rate of quantum absorption by photosystem II, reaching about 8% of maximal fluorescence yield. It is not affected by DCMU, is stimulated by anoxic conditions, and is suppressed by energy-dependent non-photochemical quenching (NPQ). The HIQ amplitude is close to proportional to the square of maximal fluorescence yield, Fm′, induced by an SP and varied by NPQ. These properties are in line with the working hypothesis of HIQ being caused by the annihilation of singlet excited chlorophyll a by triplet excited carotenoid. Significant underestimation of maximal fluorescence yield and photosystem II quantum yield in dark-acclimated samples can be avoided by use of moderate SP intensities. In physiologically healthy illuminated samples, NPQ prevents significant lowering of effective photosystem II quantum yield by HIQ, if excessive SP intensities are avoided.

     

Molecular docking using surface complementarity

A method is described to dock a ligand into a binding site in a protein on the basis of the complementarity of the inter-molecular atomic contacts. Docking is performed by maximization of a complementarity function that is dependent on atomic contact surface area and the chemical properties of the contacting atoms. The generality and simplicity of the complementarity function ensure that a wide range of chemical structures can be handled. The ligand and the protein are treated as rigid bodies, but displacement of a small number of residues lining the ligand binding site can be taken into account. The method can assist in the design of improved ligands by indicating what changes in complementarity may occur as a result of the substitution of an atom in the ligand. The capabilities of the method are demonstrated by application to 14 protein–ligand complexes of known crystal structure. © 1996 Wiley Liss, Inc.     

广东省蛇类新纪录——菱斑小头蛇

2007年6月23日,在广东省南昆山省级自然保护区采集到一条菱斑小头蛇(Oligodon catenata),为广东省蛇类新纪录。该新分布区的发现说明菱斑小头蛇在我国可能并非间断分布。     

Fluorescent two-dimensional difference gel electrophoresis unveils the potential of gel-based proteomics

Comparing different proteomes by classical two-dimensional electrophoresis is challenging and often complicated by substantial gel-to-gel variation. Separating two or more protein samples labelled with different fluorescent dyes in one single gel, as in two-dimensional difference gel electrophoresis, reduces this variability considerably. Recent technological innovations, specifically the introduction of a pooled internal standard, even further improve the quantification accuracy and statistical confidence of this method. In addition, decreasing the sample complexity by one of several protein or organelle fractionation procedures increases the number of spots investigated by this protein differential display methodology.     

Derangement of Hypothetical Proteins in Fetal Down's Syndrome Brain

The success of the Human Genome Project (HGP) enables prediction of proteins by computer programs from nucleic acid sequences and for which there is no experimental evidence. Clues for function of hypothetical proteins are provided by sequence similarity with proteins of known function in model organisms. The availability of this bulk of new data is of immediate importance to Down's syndrome (DS) research. DS is the most common human chromosomal abnormality caused by an extra copy of chromosome 21 and is characterized by somatic anomalies and mental retardation. In addition, overexpression of chromosome 21 genes is directly or indirectly responsible for mental retardation and other phenotypic abnormalities of DS. To allow insight into how trisomy 21 represents the phenotype of DS, we constructed a two-dimensional protein map and investigated expression of 8 hypothetical proteins in fetal DS (n = 7) and control (n = 7) brains (cortex). Two-dimensional electrophoresis (2-DE) with subsequent in-gel digestion of spots and matrix-assisted laser desorption/ionization (MALDI) spectroscopic identification followed by quantification of spots with specific software was applied. Quantitative analysis of hypothetical protein FLJ10849, hypothetical protein FLJ20113, and activator of hsp90 ATPase homologue 1 (AHA1) revealed levels comparable between DS and controls. By contrast, expression levels of hypothetical protein KIAA1185, hypothetical protein 55.2 kDa, hypothetical protein 58.8 kDa, actin-related protein 3beta (ARP3beta), and putative GTP-binding protein PTD004 were significantly decreased (P < 0.05) in fetal DS brain, and domain analysis suggests involvement in cytoskeleton, signaling, and chaperone system abnormalities.     

Expressional patterns of chaperones in ten human tumor cell lines

BACKGROUND: Chaperones (CH) play an important role in tumor biology but no systematic work on expressional patterns has been reported so far. The aim of the study was therefore to present an analytical method for the concomitant determination of several CH in human tumor cell lines, to generate expressional patterns in the individual cell lines and to search for tumor and non-tumor cell line specific CH expression.Human tumor cell lines of neuroblastoma, colorectal and adenocarcinoma of the ovary, osteosarcoma, rhabdomyosarcoma, malignant melanoma, lung, cervical and breast cancer, promyelocytic leukaemia were homogenised, proteins were separated on two-dimensional gel electrophoresis with in-gel digestion of proteins and MALDI-TOF/TOF analysis was carried out for the identification of CH. RESULTS: A series of CH was identified including the main CH groups as HSP90/HATPas_C, HSP70, Cpn60_TCP1, DnaJ, Thioredoxin, TPR, Pro_isomerase, HSP20, ERP29_C, KE2, Prefoldin, DUF704, BAG, GrpE and DcpS. CONCLUSIONS: The ten individual tumor cell lines showed different expression patterns, which are important for the design of CH studies in tumor cell lines. The results can serve as a reference map and form the basis of a concomitant determination of CH by a protein chemical rather than an immunochemical method, independent of antibody availability or specificity.     

Capacity of Lemna gibba L. (duckweed) for uranium and arsenic phytoremediation in mine tailing waters

The potential of Lemna gibba L. to clean uranium and arsenic contamination from mine surface waters was investigated in wetlands of two former uranium mines in eastern Germany and in laboratory hydroponic culture. Water and plants were sampled and L gibba growth and yield were monitored in tailing ponds from the field study sites. Contaminant accumulation, growth and yield experiments were conducted in the laboratory using synthetic tailing water. Mean background concentrations of the surface waters were 186.0+/-81.2 microg l(-1) uranium and 47.0+/-21.3 microg l(-1) arsenic in Site one and 293.7+/-121.3 microg l(-1) uranium and 41.37+/-24.7 microg l(-1) arsenic in Site two. The initial concentration of both uranium and arsenic in the culture solutions was 100 microg l(-1). The plant samples were either not leached, leached with deionized H2O or ethylenediaminetetracetic (EDTA). The results revealed high bioaccumulation coefficients for both uranium and arsenic. Uranium and arsenic content of L gibba dry biomass of the field samples were as follows: nonleached samples > deionized H2O leached (insignificant ANOVA p = 0.05) > EDTA leached. The difference in both arsenic and uranium enrichment were significantly high between the nonleached and the other two lead samples tested at ANOVA p > 0.001. Estimated mean L gibba density in surface water was 85,344.8+/-1843.4 fronds m(-2) (approximately 1319.7 g m(-2)). The maximum specific growth rate was 0.47+/-0.2 d(-1), which exceeded reported specific growth rates for L gibba in the literature. Average yield was estimated at 20.2+/-6.7 g m(-2) d(-1), giving approximately 73.6+/-21.4 t ha(-1) y(-1) as the annual yield. The highest accumulations observed were 896.9+/-203.8 mg kg(-1) uranium and 1021.7+/-250.8 mg kg(-1) arsenic dry biomass for a 21-d test period in the laboratory steady-state experiments. The potential extractions from surface waters with L gibba L. were estimated to be 662.7 kg uranium ha(-1) yr(-1) and 751.9 kg arsenic ha(-1) yr(-1) under the above conditions.     

NRMD: Nuclear Receptor Mutation Database

The NRMD is a database for nuclear receptor mutation information. It includes mutation information from SWISS-PROT/TrEMBL, several web-based mutation data resources, and data extracted from the literature in a fully automatic manner. Because it is also possible to add mutations manually, a hundred mutations were added for completeness. At present, the NRMD contains information about 893 mutations in 54 nuclear receptors. A common numbering scheme for all nuclear receptors eases the use of the information for many kinds of studies. The NRMD is freely available to academia and industry as a stand-alone version at: www.receptors.org/NR/.