Binding of vanadate to human erythrocyte ghosts and subsequent events

Spectroscopic techniques were used to investigate the interaction between vanadate and human erythrocyte ghosts. Direct evidence from ⁵¹V nuclear magnetic resonance (NMR) studies suggested that the monomeric and polymeric vanadate species may bind to the anion binding sites of band 3 protein of the erythrocyte membrane. The results of ⁵¹V NMR studies and the quenching effect of vanadate on the intrinsic fluorescence of the membrane proteins indicated that in the low concentration range of vanadate (<0.6 mm), monomeric vanadate binds mostly to the anion sites of band 3 protein with the dissociation constant close to 0.23 mm. The experiments of sulfhydryl content titration by the method of Ellman and residue sulfhydryl-labeled fluorescence spectroscopies clearly displayed that vanadate reacts directly with sulfhydryl groups. The appearance of the anisotropic election spin resonance (ESR) signal of vanadyl suggests that a small (c. 3%) amount of vanadate was reduced by sulfhydryl groups of membrane proteins. The fluidity and order of intact ghost membrane were reduced by the reaction with vanadate, as shown by the ESR studies employing the protein- and lipid-specific spin labels. It was concluded that although vanadates mainly bind to band 3 protein, a minor part of vanadate may oxidize the residue sulfhydryl groups of membrane proteins, and thus decrease the fluidity of erythrocyte membrane.     

Functional activity of RLIM/Rnf12 is regulated by phosphorylation-dependent nucleocytoplasmic shuttling

The X-linked gene Rnf12 encodes the ubiquitin ligase really interesting new gene (RING) finger LIM domain–interacting protein (RLIM)/RING finger protein 12 (Rnf12), which serves as a major sex-specific epigenetic regulator of female mouse nurturing tissues. Early during embryogenesis, RLIM/Rnf12 expressed from the maternal allele is crucial for the development of extraembryonic trophoblast cells. In contrast, in mammary glands of pregnant and lactating adult females RLIM/Rnf12 expressed from the paternal allele functions as a critical survival factor for milk-producing alveolar cells. Although RLIM/Rnf12 is detected mostly in the nucleus, little is known about how and in which cellular compartment(s) RLIM/Rnf12 mediates its biological functions. Here we demonstrate that RLIM/Rnf12 protein shuttles between nucleus and cytoplasm and this is regulated by phosphorylation of serine S214 located within its nuclear localization sequence. We show that shuttling is important for RLIM to exert its biological functions, as alveolar cell survival activity is inhibited in cells expressing shuttling-deficient nuclear or cytoplasmic RLIM/Rnf12. Thus regulated nucleocytoplasmic shuttling of RLIM/Rnf12 coordinates cellular compartments during mammary alveolar cell survival.     

Nanoporous Polytetrafluoroethylene/Silica Composite Separator as a High‐Performance All‐Vanadium Redox Flow Battery Membrane

A novel low‐cost nanoporous polytetrafluoroethylene (PTFE)/silica composite separator has been prepared and evaluated for its use in an all‐vanadium redox flow battery (VRB). The separator consists of silica particles enmeshed in a PTFE fibril matrix. It possesses unique nanoporous structures with an average pore size of 38 nm and a porosity of 48%. These pores function as the ion transport channels during redox flow battery operation. This separator provides excellent electrochemical performance in the mixed‐acid VRB system. The VRB using this separator delivers impressive energy efficiency, rate capability, and temperature tolerance. In additon, the flow cell using the novel separator also demonstrates an exceptional capacity retention capability over extended cycling, thus offering excellent stability for long‐term operation. The characteristics of low cost, excellent electrochemical performance and proven chemical stability afford the PTFE/silica nanoporous separator great potential as a substitute for the Nafion membrane used in VRB applications.     

Effects of Bacillus Subtilis-Zinc on Rats with Congenital Zinc Deficiency

Biological Trace Element Research - This study investigated the effects of dietary supplementation of Bacillus subtilis-zinc on growth rates of the body and organs, nutrient utilization, microbial...     

Systematics and Species Validity of the Dabieshan Pit Viper Protobothrops dabieshanensis Huang et al. 2012: Evidence from a Mitochondrial Gene Sequence Analysis

Aimed to evaluate the phylogenetic position of the recently described Protobothrops dabieshanensis Huang et al. （2012）, phylogenic relationships of 12 species within Protobothrops based on four mtDNA gene fragments （12S RNA, 16S RNA, ND4 and Cyt b） were reconstructed in our study. The result indicates a clade composed ofP dabiesha- nensis, P. jerdonii and P xiangchengsis with strong support. The genetic distance among P dabieshanensis, P jerdonii and P xiangchengsis was much lower than other congeners. Based on the data from the phylogenetic analysis and pre- viously described morphological differences, we conclude that P dabieshanensis is a valid species with close affinities to P jerdonii and P xiangchengsis.     

Spatial dynamics of Chinese Muntjac related to past and future climate fluctuations

Climate fluctuations in the past and in the future are likely to result in population expansions,shifts,or the contraction of the ecological niche of many speci...     

Endogenous 3,4-Dihydroxyphenylalanine and Dopaquinone Modifications on Protein Tyrosine: LINKS TO MITOCHONDRIALLY DERIVED OXIDATIVE STRESS VIA HYDROXYL RADICAL*

Oxidative modifications of protein tyrosines have been implicated in multiple human diseases. Among these modifications, elevations in levels of 3,4-dihydroxyphenylalanine (DOPA), a major product of hydroxyl radical addition to tyrosine, has been observed in a number of pathologies. Here we report the first proteome survey of endogenous site-specific modifications, i.e. DOPA and its further oxidation product dopaquinone in mouse brain and heart tissues. Results from LC-MS/MS analyses included 50 and 14 DOPA-modified tyrosine sites identified from brain and heart, respectively, whereas only a few nitrotyrosine-containing peptides, a more commonly studied marker of oxidative stress, were detectable, suggesting the much higher abundance for DOPA modification as compared with tyrosine nitration. Moreover, 20 and 12 dopaquinone-modified peptides were observed from brain and heart, respectively; nearly one-fourth of these peptides were also observed with DOPA modification on the same sites. For both tissues, these modifications are preferentially found in mitochondrial proteins with metal binding properties, consistent with metal-catalyzed hydroxyl radical formation from mitochondrial superoxide and hydrogen peroxide. These modifications also link to a number of mitochondrially associated and other signaling pathways. Furthermore, many of the modification sites were common sites of previously reported tyrosine phosphorylation, suggesting potential disruption of signaling pathways. Collectively, the results suggest that these modifications are linked with mitochondrially derived oxidative stress and may serve as sensitive markers for disease pathologies.Generation of reactive oxygen species (ROS)¹ and reactive nitrogen species is a normal consequence of aerobic metabolism that, in excess, results in oxidative stress that further leads to oxidative modification of proteins, lipids, and DNA, events that may lead to altered cellular function and even cell death (1, 2). Chronic oxidative stress is well recognized as having a central role in disease and is responsible for both direct alteration of biomolecular structure-function and compensatory changes in cellular processes (1–4). It is increasingly recognized that oxidative modifications of proteins can serve as potential biomarkers indicative of the physiological states and changes that occur during disease progression. Thus, the ability to quantitatively measure specific protein oxidation products has the potential to provide the means to monitor the physiological state of a tissue or organism, in particular any progression toward pathology. Given Parkinson disease (PD) as an example, a number of oxidative modifications on proteins pertinent to PD have been identified, further supporting the potential importance of oxidative modifications to disease pathogenesis (5).Many oxidative modifications on specific amino acid residues, such as protein carbonylation (6), cysteine S-nitrosylation (7–9), cysteine oxidation to sulfinic or sulfonic acid (10–12), methionine oxidation (13, 14), and tyrosine nitration (15–21) within complex protein mixtures, have been detected by MS-based proteomics; however, their low abundance levels within complex proteomes often hinder confident identification of these potentially significant modifications (22). For example, tyrosine nitration is a well studied post-translational modification mediated by peroxynitrite (ONOO⁻) or nitrogen dioxide (^·NO₂), which commonly occur in cells during oxidative stress and inflammation; however, only a small number of nitrotyrosine proteins have been identified from a given proteome sample because of insufficient analytical sensitivity and the chance of incorrect peptide assignments (19, 23). With recent advances in high resolution MS that provide high mass measurement accuracy, the ability to confidently identify modified peptides has been significantly enhanced (24).Hydroxyl radical (HO^·) is one of the most reactive and major species generated under aerobic conditions in biological systems (1, 25, 26). Among several HO^·-mediated oxidative modifications, the protein tyrosine modification 3,4-dihydroxyphenylalanine (DOPA) has been reported as a major product and index of HO^· attack on tyrosine residues in proteins (Fig. 1) (27, 28). DOPA is also formed on protein tyrosine residues via controlled enzymatic pathways through enzymes such as tyrosinase or tyrosine hydroxylase (28). Once formed, protein-bound DOPA has the potential to initiate further oxidative reactions through binding and reducing transition metals or through redox cycling between catechol and quinone (dopaquinone) forms (29, 30). Recent studies have suggested that protein-bound DOPA is involved in triggering antioxidant defenses (30) and mediating oxidative damage to DNA (31). Moreover, elevated levels of protein-bound DOPA have been reported in several diseases, including atherosclerosis, cataracts, and myocardial disease, and in PD patients undergoing levodopa therapy (26, 32–36). However, the specific DOPA-modified proteins, which could provide mechanistic knowledge of the progression of these diseases, have not been identified (27, 28). The ability to identify site-specific protein modifications should lead to a better understanding of the role of DOPA modification in disease pathologies as well as new molecular signatures or therapeutic targets for diseases.Open in a separate windowFig. 1.DOPA and dopaquinone formation from tyrosine.Therefore, in this study, we demonstrate the ability to identify site-specific DOPA and dopaquinone (DQ) modifications on protein tyrosine residues in normal mouse brain and heart tissues and their relative stoichiometries that are present in vivo under non-stressed conditions. Such endogenous protein modifications were detected using LC-MS/MS. The results from this global proteomics survey suggests that HO^· in tissues under normal conditions is generated largely from the mitochondria and metal-binding proteins where the resulting DOPA/DQ modifications have the potential to disrupt mitochondrial respiration as well as alter tyrosine phosphorylation signaling pathways such as 14-3-3-mediated signaling in brain tissue.     

A Stable Vanadium Redox‐Flow Battery with High Energy Density for Large‐Scale Energy Storage

The all‐vanadium redox flow battery is a promising technology for large‐scale renewable and grid energy storage, but is limited by the low energy density and poor stability of the vanadium electrolyte solutions. A new vanadium redox flow battery with a significant improvement over the current technology is reported in this paper. This battery uses sulfate‐chloride mixed electrolytes, which are capable of dissolving 2.5 M vanadium, representing about a 70% increase in energy capacity over the current sulfate system. More importantly, the new electrolyte remains stable over a wide temperature range of ?5 to 50 °C, potentially eliminating the need for electrolyte temperature control in practical applications. This development would lead to a significant reduction in the cost of energy storage, thus accelerating its market penetration.     

Whole genome PCR scanning reveals the syntenic genome structure of toxigenic Vibrio cholerae strains in the O1/O139 population

Vibrio cholerae is commonly found in estuarine water systems. Toxigenic O1 and O139 V. cholerae strains have caused cholera epidemics and pandemics, whereas the nontoxigenic strains within these serogroups only occasionally lead to disease. To understand the differences in the genome and clonality between the toxigenic and nontoxigenic strains of V. cholerae serogroups O1 and O139, we employed a whole genome PCR scanning (WGPScanning) method, an rrn operon-mediated fragment rearrangement analysis and comparative genomic hybridization (CGH) to analyze the genome structure of different strains. WGPScanning in conjunction with CGH revealed that the genomic contents of the toxigenic strains were conservative, except for a few indels located mainly in mobile elements. Minor nucleotide variation in orthologous genes appeared to be the major difference between the toxigenic strains. rrn operon-mediated rearrangements were infrequent in El Tor toxigenic strains tested using I-CeuI digested pulsed-field gel electrophoresis (PFGE) analysis and PCR analysis based on flanking sequence of rrn operons. Using these methods, we found that the genomic structures of toxigenic El Tor and O139 strains were syntenic. The nontoxigenic strains exhibited more extensive sequence variations, but toxin coregulated pilus positive (TCP+) strains had a similar structure. TCP+ nontoxigenic strains could be subdivided into multiple lineages according to the TCP type, suggesting the existence of complex intermediates in the evolution of toxigenic strains. The data indicate that toxigenic O1 El Tor and O139 strains were derived from a single lineage of intermediates from complex clones in the environment. The nontoxigenic strains with non-El Tor type TCP may yet evolve into new epidemic clones after attaining toxigenic attributes.