Effect of alcohols on photochemical transformations of mouse oxyhemoglobin

The spectral method was used to study the influence of such alcohols as xylene, mannitol, sorbitol and dulcitol on photochemical oxidation of mouse oxyhemoglobin molecules (6.68 X 10(-5) M). Mannitol (5.35 X 10(-4) M) was shown to exert a protective action with regard to UV-irradiated hemoproteid: the extent to which oxyhemoglobin molecules were oxidized in the presence of mannotol was lesser than that in its absence. Sorbiol or xylene (5.35 X 10(-4) M) added to an aqueous solution of hemoproteid failed to exert a photoprotective effect with respect to protein molecules.     

Atmospheric photochemical transformations enhance 1,3-butadiene-induced inflammatory responses in human epithelial cells: The role of ozone and other photochemical degradation products

Chemistry of hazardous air pollutants has been studied for many years, yet little is known about how these chemicals, once reacted within urban atmospheres, affect healthy and susceptible individuals. Once released into the atmosphere, 1,3-butadiene (BD) reacts with hydroxyl radicals and ozone (created by photochemical processes), to produce many identified and unidentified products. Once this transformation has occurred, the toxic potential of atmospheric pollutants such as BD in the ambient environment is currently unclear. During this study, environmental irradiation chambers (also called smog chambers), utilizing natural sunlight, were used to create photochemical transformations of BD. The smog chamber/in vitro exposure system was designed to investigate the toxicity of chemicals before and after photochemical reactions and to investigate interactions with the urban atmosphere using representative in vitro samples. In this study, we determined the relative toxicity and inflammatory gene expression induced by coupling smog chamber atmospheres with an in vitro system to expose human respiratory epithelial cells to BD, BDs photochemical degradation products, or the equivalent ozone generated within the photochemical mixture. Exposure to the photochemically generated products of BD (primarily acrolein, acetaldehyde, formaldehyde, furan and ozone) induced significant increases in cytotoxicity, IL-8, and IL-6 gene expression compared to a synthetic mixture of primary products that was created by injecting the correct concentrations of the detected products from the irradiation experiments. Interestingly, exposure to the equivalent levels of ozone generated during the photochemical transformation of BD did not induce the same level of inflammatory cytokine release for either exposure protocol, suggesting that the effects from ozone alone do not account for the entire response in the irradiation experiments. These results indicate that BDs full photochemical product generation and interactions, rather than ozone alone, must be carefully evaluated when investigating the possible adverse health effects to BD exposures. The research presented here takes into account that photochemical transformations of hazardous air pollutants (HAPs) does generate a dynamic exposure system and therefore provides a more realistic approach to estimate the toxicity of ambient air pollutants once they are released into the atmosphere.     

Structural mobility and transformations in globular proteins

Journal of Biosciences - Although globular proteins are endowed with well defined three-dimensional structures, they exhibit substantial mobility within the framework of the given three-dimensional...     

过氧化物氧还蛋白家族的功能及调节机制

过氧化物氧还蛋白(peroxiredoxin,Prx)家族是细胞中一类高丰度蛋白质,作为过氧化物酶对维持体内过氧化氢水平发挥着重要的作用,并且通过调控蛋白激酶的氧化还原状态参与细胞信号转导调控过程。Prx家族根据其参与催化反应的半胱氨酸残基数目分为典型双半胱氨酸型(2-Cys)、非典型双半胱氨酸型(atypical 2-Cys)和单半胱氨酸型(1-Cys)。Prx的活性受到寡聚化状态、磷酸化以及蛋白质水解的调控。     

Oligomeric state and stoichiometry of p24 proteins in the early secretory pathway

The p24 proteins belong to a highly conserved family of membrane proteins that cycle in the early secretory pathway. They bind to the coat proteins of COPI and COPII vesicles, and are proposed to be involved in vesicle biogenesis, cargo uptake, and quality control, but their precise function is still under debate. Most p24 proteins form hetero-oligomers, essential for their correct localization and stability. Functional insights regarding the mechanisms of their steady state localization and the role of interaction with coat proteins has been hampered by a lack of data on their concentration and state of oligomerization within the endoplasmic reticulum, the intermediate compartment, and Golgi complex. We have determined for all mammalian p24 family members the size of the oligomers formed and their stoichiometric relation in each of these individual organelles. In contrast to earlier reports, we show that individual members exist as dimers and monomers and that the ratio between these two forms depends on both the organelle investigated and the p24 protein. We find unequal quantities, with p23 and p27 building up concentration gradients, ruling out a simple 1:1 stoichiometry. In addition, we show differential cycling of individual p24 members. These data point to a complex and dynamic system of altering dimerizations of the family members.     

Topological aspects of conformational transformations in proteins

The topological aspects of the conformational transformations in proteins are investigated using a new peptide-ribbon representation of the tertiary structure. The topological parameters evaluated on a set of 49 proteins show striking regularities that extend beyond the secondary structures actually present and are interpreted as a manifestation of the topological invariance of conformational transformations in globular proteins.     

Oligomeric structure, dynamics, and orientation of membrane proteins from solid-state NMR

Solid-state NMR is a versatile and powerful tool for determining the dynamic structure of membrane proteins at atomic resolution. I review the recent progress in determining the orientation, the internal and global protein dynamics, the oligomeric structure, and the ligand-bound structure of membrane proteins with both alpha-helical and beta sheet conformations. Examples are given that illustrate the insights into protein function that can be gained from the NMR structural information.     

Heritability of UV-sensitivity and photo-reactivation ability in Drosophila embryos

In Drosohila the UV sensitivity at the zygot stage and PR ability of damage age induced by UV irradiation at 290–380 nm are heritable characters. The heritability of those characters is matroclinal. Resistance to UV irradiation dominates over sensitivity, and high PR ability is dominant over low. These characters are not associated with the pleotropic action of any of the genes in question.     

Emotion modulation of visual attention: categorical and temporal characteristics

Background

Experimental research has shown that emotional stimuli can either enhance or impair attentional performance. However, the relative effects of specific emotional stimuli and the specific time course of these differential effects are unclear.

Methodology/Principal Findings

In the present study, participants (n = 50) searched for a single target within a rapid serial visual presentation of images. Irrelevant fear, disgust, erotic or neutral images preceded the target by two, four, six, or eight items. At lag 2, erotic images induced the greatest deficits in subsequent target processing compared to other images, consistent with a large emotional attentional blink. Fear and disgust images also produced a larger attentional blinks at lag 2 than neutral images. Erotic, fear, and disgust images continued to induce greater deficits than neutral images at lag 4 and 6. However, target processing deficits induced by erotic, fear, and disgust images at intermediate lags (lag 4 and 6) did not consistently differ from each other. In contrast to performance at lag 2, 4, and 6, enhancement in target processing for emotional stimuli was observed in comparison to neutral stimuli at lag 8.

Conclusions/Significance

These findings suggest that task-irrelevant emotion information, particularly erotica, impairs intentional allocation of attention at early temporal stages, but at later temporal stages, emotional stimuli can have an enhancing effect on directed attention. These data suggest that the effects of emotional stimuli on attention can be both positive and negative depending upon temporal factors.     

Cholinergic modulation of anaphylactic shock: plasma proteins influence

Cholinergic drugs can modulate anaphylactic shock and change lymphocyte functions. Plasma proteins modulate effects of muscarinic antagonists during anaphylactic shock. The present investigation was carried out to study the antianaphylactic activity of methacine (antagonist at muscarinic receptors) in combination with neostigmine (anticholinesterase drug). However, it is not known whether plasma proteins-albumin, C-reactive protein (CRP) and immunoglobulin G (IgG) - modify the effects of cholinergic drugs like methacine, serotonin (5-HT) level in the lymphoid organs and quantity of antibody-forming cells (AFC) in the spleen of guinea pigs during experimental anaphylactic shock. It was shown that administration of methacine with neostigmine (40 min and 15 min prior to shock induction, accordingly) at the pathochemical stage revokes shock development. By blocking cholinesterase endogenous acetylcholine is increased and methacine blocks muscarinic receptors and therewith unwanted side effects in the airways (bronchoconstriction) and heart (bradycardia). Administration of the combination of methacine with neostigmine at the immunological stage (guinea pig sensitization) does not affect the course of anaphylactic shock. Administration of methacine with IgG at the pathochemical stage of shock significantly decreases shock intensity, while administration of methacine with CRP or albumin has no influence on the shock. Administration of IgG or CRP (not albumin) at the immunological stage of shock and albumin or IgG (not CRP) at the pathochemical stage leads to reduction of the anaphylactic reaction. Application of methacine with neostigmine or IgG (effective combinations of drugs) results in normalization of antibody response in the spleen and 5-HT level in the lymphoid organs. Administration of methacine with CRP or albumin (ineffective combinations of drugs) leads to increase of antibody response in the spleen and 5-HT level in the lymphoid organs. Administration of hexamethonium or aceclidine aggravated anaphylactic shock reaction. Thus, the combination of methacine with neostigmine can regulate the pathochemical stage of shock and the 5-HT release. At the pathochemical stage of shock IgG increases the antianaphylactic activity of methacine, but albumin and CRP abolish it.     

Oligomeric state of membrane transport proteins analyzed with blue native electrophoresis and analytical ultracentrifugation

Blue native electrophoresis is used widely for the analysis of non-dissociated protein complexes with respect to composition, oligomeric state and molecular mass. However, the effects of detergent or dye binding on the mass and stability of the integral membrane proteins have not been studied. By comparison with analytical ultracentrifugation, we have evaluated whether the oligomeric state of membrane transport proteins is reflected reliably with blue native electrophoresis. For the analysis we have used two well-characterized transporters, that is, the major facilitator superfamily protein LacS and the phosphotransferase system EII(Mtl). For another member of the major facilitator superfamily, the xyloside transporter XylP from Lactobacillus pentosus, the complete analysis of the quaternary structure determined by analytical ultracentrifugation and freeze-fracture electron microscopy is presented.Our experiments show that during blue native electrophoresis the detergent bound to the proteins is replaced by the amphipathic Coomassie brilliant blue (CBB) dye. The mass of the bound CBB dye was quantified. Provided this additional mass of bound CBB dye is accounted for and care is taken in the choice and concentration of the detergent used, the mass of LacS, XylP and EII(Mtl) and four other membrane (transport) proteins could be deduced within 10 % error. Our data underscore the fact that the oligomeric state of many membrane transport proteins is dimeric.     

Transglutaminase amine substrates for photochemical labeling and cleavable cross-linking of proteins

A new procedure for the photochemical labeling of peptides and for the production of cleavable cross-links between protein molecules is given. This method is mediated through the catalytic action of the enzyme guinea pig liver transglutaminase. Each of the labeling and cross-linking reagents described here is an amine substrate for transglutaminases and, because of the narrow specificity of these enzymes, is introduced covalently only at the gamma-carboxamide group of available peptide-bound glutamine residues. Cross-linking results either solely through the action of the enzyme in the case of a diamine substrate, or by subsequent photolysis in the case of photosensitive amine substrates. Cleavable bonds in several of the substrates are disulfide or vicinal hydroxyl groups. The validity of the procedure is demonstrated by the preparation of photosensitive derivatives of substance P and glucagon 1-6 and in the cleavable covalent cross-linking of guanidinated beta-casein.     

Oligomeric structure of p21 ras proteins as determined by radiation inactivation

Using radiation inactivation we determined that p21 ras proteins exhibit an oligomeric target size when assayed both structurally and functionally. Similar target sizes of p21 in ras-transformed cells and in purified preparations of the protein suggested that its structure is homo-oligomeric. p21 monomers were destroyed by radiation with the same target size as the GTP binding activity, indicating the occurrence of a tight association allowing energy transfer between the monomers. Irradiation in the presence of GTP, dithiothreitol, or EDTA did not change the target size. Normal (Gly12) and transforming (Lys12) forms of the protein exhibited similar target sizes. The homo-oligomeric structure suggests that p21 ras proteins do not conform to the structure of monomeric alpha subunits in classical G proteins (alpha beta gamma heterotrimers) and establishes similarities with other homo-oligomeric proteins (such as Escherichia coli CRP) which acquire the active conformation through subunit reorientation upon nucleotide binding.     

Topological aspects of the conformational transformations in polypeptides and proteins

The topological aspects of the conformational transformations in a polypeptide chain are investigated in relation to the problem of selecting the minimum-energy pathways in protein folding.     

Ionic channels: modulation by G proteins and by phosphorylation.

The gating of ion channels may be modulated by G proteins or by phosphorylation. Direct coupling between G proteins and ion channels has been shown in excised patches of membrane. Steps must now be taken to study the protein domains of G proteins and ion channels involved in the mutual interaction. The concept of channel modulation by protein kinases has recently been extended to include additional types of ion channel.     

Photochemical transformation of lactate dehydrogenase isoforms: UV-sensitivity in the presence of biogenous amines

It has been all round investigation of UV-irradiation influence in a wide dose range on the structural and functional properties of human blood lactate dehydrogenase (LDH) isoenzymes. The photoprotective action of biogenous amines on the functional activity of different enzyme isoforms was found. It has been established that the protective action of biogenous amines is caused by the formation of complex LDH--biogenous amine and by the acception of the active oxygen forms by the molecules of lactate dehydrogenase. Under the conditions of exogenous singlet oxygen generation in the presence of methylene blue, the inactivation of immobilized LDH tetramers and subunits was observed, that shows participation of this active intermediate in the processes of UV-modification of the enzyme in soluble and immobilized states. The scheme of processes of LDH molecules phototransformations in the presence of biogenous amines has been suggested.     

Cholesterol modulation of beta-adrenergic receptor characteristics

Cholesterol, a major structural component of plasma membranes, has a profound influence on cell surface receptor characteristics and on adenylate cyclase activity. beta-Adrenergic receptor number, adenylate cyclase activity, and receptor-cyclase coupling were assessed in rat lung membranes following preincubation with cholesteryl hemisuccinate. beta-Adrenergic receptor number increased by 50% without a change in antagonist affinity. However, beta-adrenergic receptor affinity for isoproterenol increased 2-fold as a result of an increase in the affinity of the isoproterenol high-affinity binding site. The increase in agonist affinity did not potentiate hormone-stimulated adenylate cyclase activity, which decreased 3-fold following cholesterol incorporation. However, the ratio of isoproterenol to GTP-stimulated activity was unchanged with cholesterol. Stimulation distal to the receptor by GTP, NaF, GppNHp, Mn2+ and forskolin also demonstrated 50-80% reduced enzyme activity following cholesterol incorporation. These data suggest that membrane cholesterol incorporation decreases catalytic unit activity without affecting transduction of the hormone signal.     

Bacteriocin factors responsible for UV-sensitivity and susceptibility to post-irradiation breakdown of DNA

Summary Lack of dose-modifying protection by acriflavine against UV killing of E. coli Bs-2 and Bs-11 is explained by their carrying an inducible colicin. Its induction could account for post-irradiation break-down of DNA.     

UV-sensitivity and UV-mutability of infectious lambdaDNA: reactivation, protection and mutability in various assay systems

Summary The UV-sensitivity of phage and its infectious DNA have been compared in experiments involving infection of normal cells by phage and transfection of lysozyme-EDTA spheroplasts or Ca⁺⁺-treated cells by phage DNA. It is shown that UV-irradiated DNA undergoes extensive HCR. Since intact phage and free phage DNA have the same survival after UV-irradiation in Hcr^- spheroplasts and cells, resp., and since survival is also identical in Ca⁺⁺-treated Hcr⁺ cells it is concluded that DNA in solution or packaged in the phage head provides the same target for the induction of lethal UV lesions. This conclusion is supported by the observation that cysteamine provides a similar radioprotection to the intact phage and its free DNA. Spheroplasts of Hcr⁺ cells, however, have an HCR capacity reduced by about 20% when compared with normal or Ca⁺⁺-treated cells. Moreover, UV-reactivation of irradiated DNA, which is absent in spheroplasts, occurs efficiently in Ca⁺⁺-treated cells. Possible reasons for the physiological difference between spheroplasts and normal cells are discussed. c-mutations, which are readily induced by UV in phage assayed with E. coli mul ^-, could not be induced in DNA when assayed with spheroplasts or Ca⁺⁺-treated cells of this strain. No mutants were also found with DNA extracted from UV-irradiated phage. The significance of the mode of entry of UV-irradiated DNA into a cell for the production of mutations is discussed.