Purification, crystallization and X-ray diffraction analyses of the T. elongatus PSII core dimer with strontium replacing calcium in the oxygen-evolving complex

The core complex of photosystem II (PSII) was purified from thermophillic cyanobaterium Thermosynechococcus elongatus grown in Sr²⁺-containing and Ca²⁺-free medium. Functional in vivo incorporation of Sr²⁺ into the oxygen-evolving complex (OEC) was confirmed by EPR analysis of the isolated and highly purified SrPSII complex in agreement with the previous study of Boussac et al. [J. Biol. Chem. 279 (2004) 22809-22819]. Three-dimensional crystals of SrPSII complex were obtained which diffracted to 3.9 Å and belonged to the orthorhombic space group P2₁2₁2₁ with unit cell dimensions of a = 133.6 Å, b = 236.6 Å, c = 307.8 Å. Anomalous diffraction data collected at the Sr K-X-ray absorption edge identified a novel Sr²⁺-binding site which, within the resolution of these data (6.5 Å), is consistent with the positioning of Ca²⁺ in the recent crystallographic models of PSII [Ferreira et al. Science 303 (2004) 1831-1838, Loll et al. Nature 438 (2005) 1040-1044]. Fluorescence measurements on SrPSII crystals confirmed that crystallized SrPSII was active in transferring electrons from the OEC to the acceptor site of the reaction centre. However, SrPSII showed altered functional properties of its modified OEC in comparison with that of the CaPSII counterpart: slowdown of the Q_A-to-Q_B electron transfer and stabilized S₂Q_A⁻ charge recombination.     

Quantitative proteomics suggests metabolic reprogramming during ETHE1 deficiency

Deficiency of mitochondrial sulfur dioxygenase (ETHE1) causes the severe metabolic disorder ethylmalonic encephalopathy, which is characterized by early‐onset encephalopathy and defective cytochrome C oxidase because of hydrogen sulfide accumulation. Although the severe systemic consequences of the disorder are becoming clear, the molecular effects are not well defined. Therefore, for further elucidating the effects of ETHE1‐deficiency, we performed a large scale quantitative proteomics study on liver tissue from ETHE1‐deficient mice. Our results demonstrated a clear link between ETHE1‐deficiency and redox active proteins, as reflected by downregulation of several proteins related to oxidation‐reduction, such as different dehydrogenases and cytochrome P450 (CYP450) members. Furthermore, the protein data indicated impact of the ETHE1‐deficiency on metabolic reprogramming through upregulation of glycolytic enzymes and by altering several heterogeneous ribonucleoproteins, indicating novel link between ETHE1 and gene expression regulation. We also found increase in total protein acetylation level, pointing out the link between ETHE1 and acetylation, which is likely controlled by both redox state and cellular metabolites. These findings are relevant for understanding the complexity of the disease and may shed light on important functions influenced by ETHE1 deficiency and by the concomitant increase in the gaseous mediator hydrogen sulfide. All MS data have been deposited in the ProteomeXchange with the dataset identifiers PXD002741 ( http://proteomecentral.proteomexchange.org/dataset/PXD002741 ) and PXD002742 ( http://proteomecentral.proteomexchange.org/dataset/PXD002741 ).     

A mathematical model of intracranial pressure dynamics for brain hypothermia treatment

Brain hypothermia treatment is used as a neuroprotectant to decompress the elevated intracranial pressure (ICP) in acute neuropatients. However, a quantitative relationship between decompression and brain hypothermia is still unclear, this makes medical treatment difficult and ineffective. The objective of this paper is to develop a general mathematical model integrating hemodynamics and biothermal dynamics to enable a quantitative prediction of transient responses of elevated ICP to ambient cooling temperature. The model consists of a lumped-parameter compartmental representation of the body, and is based on two mechanisms of temperature dependence encountered in hypothermia, i.e. the van't Hoff's effect of metabolism and the Arrhenius' effect of capillary filtration. Model parameters are taken from the literature. The model is verified by comparing the simulation results to population-averaged data and clinical evidence of brain hypothermia treatment. It is possible to assign special model inputs to mimic clinical maneuvers, and to adjust model parameters to simulate pathophysiological states of intracranial hypertension. Characteristics of elevated ICP are quantitatively estimated by using linear approximation of step response with respect to ambient cooling temperature. Gain of about 4.9 mmHg degrees C(-1), dead time of about 1.0 h and a time constant of about 9.8h are estimated for the hypothermic decompression. Based on the estimated characteristics, a feedback control of elevated ICP is introduced in a simulated intracranial hypertension of vasogenic brain edema. Simulation results suggest the possibility of an automatic control of the elevated ICP in brain hypothermia treatment.     

Structural characterization of the zinc binding domain in cytosolic PSD-95 interactor (cypin): Role of zinc binding in guanine deamination and dendrite branching

Dendrite morphology regulates how a postsynaptic neuron receives information from presynaptic neurons. The specific patterning of dendrite branches is promoted by extrinsic and intrinsic factors that trigger the activation of functional signaling pathways. However, most of the regulating factors and the biochemical mechanisms involved in regulating dendrite branching are unknown. Our laboratory previously reported that cypin (cytosolic PSD-95 interactor) plays an active role in regulating dendrite branching in hippocampal neurons. Cypin-promoted increases in dendrite number are dependent on guanine deaminase activity. In order to identify the specific structural role of zinc-binding in cypin-mediated dendrite branching and guanine deaminase activity, we employed computational homology modeling techniques to construct a three dimensional structural model of cypin. Analysis of the protein-ion sequestration scaffold of this model identified several histidines and aspartic acid residues responsible for zinc binding. Single substitution mutations in these specific sites completely disrupted the guanine deaminase enzymatic activity and rendered cypin unable to promote dendrite branching in rat hippocampal neurons. The specific zinc ion-binding function of each residue in the protein scaffold was also confirmed by Inductively Coupled Plasma-Optic Emission Spectrometry. Inspection of our structural model confirmed that His82 and His84 coordinate with the zinc ion, together with His240, His279, and Asp330, residues that until now were unknown to play a role in this regard. Furthermore, promotion of dendrite branching by cypin is zinc-dependent.     

Trace elements distribution and species fractionation in the wheat (Triticum aestivum) plant

Abstract

The status of 13 trace elements’ (both essential and toxic) was investigated in individual parts of the winter wheat plant(Triticum aestivum) taken during its whole cultivation period. The study includes the determination of total concentrations, portions soluble in 0.02 mol L^?1 Tris-HCI buffer solution (pH = 7.5), and the fractionation of soluble species of elements by SEC and ICP/MS. Ligands of trace elements from a low-molecular weight SEC fraction were isolated by affinity chromatography and characterised by MALDI/MS analyses and by amino acids composition. Inhomogeneous accumulation of trace elements was found in the analysed plant tissues. The concentrations of elements are also affected by the maturity of the plants. The distribution of the soluble species of the elements between chromatographic fractions exhibited some regularity in all the samples. Substantial amounts of trace elements are located in a low-molecular weight fraction (< 2 kDa). Only chromatograms of Zn (grain) and Cu (all samples) contain significant medium-molecular and high-molecular weight fractions. Compounds isolated from the low-molecular weight fractions are rich in cystein and dicarboxylic amino acids or their amides. MALDI/MS spectra of these compounds isolated from shoots, straw and grain confirmed the presence of the phytochelatin PC₅.     

阿胶、新阿胶、黄明胶、马皮胶、杂皮胶的质量对比研究——Ⅱ、微量元素分析

本文用电感耦合等离子体发射光谱法测定了对人体具有营养、生理及临床意义的27种微量元素。结果表明,各类胶中这些元素的含量均有一个比较狭小的变动范围,可供质量鉴别时参考。除杂皮胶有多种元素含量超出各自的变动范围之外,阿胶、新阿胶、黄明胶中各元素含量比较相近,似可用猪皮、牛皮代用驴皮。阿胶的补血作用可能与其含铁量较高有关,阿胶的止血作用可能与其含钙有关。     

Determination of standard zinc values in the intact tissues of mice by ICP spectrometry

The most commonly encountered difficulties for the quantitative measurement of zinc in biological samples are the limited sample amount, total and effective digestion of connective and fatty residues, and low zinc concentrations. These problems often lead to the determination of lower zinc values than actually present, so that the sample preparation, digestion, and analytical procedure deserve careful attention. In this short communication, a new method for microwave tissue disintegration is described. The authors have obtained consistent and reproducible results with tissue samples of 0.5 g or less.