Estimation of ^{3}J_{HN\hbox{-}H\alpha} and ^{3}J_{H\alpha\hbox{-}H\beta} coupling constants from heteronuclear TOCSY spectra

(3)J proton-proton coupling constants bear information on the intervening dihedral angles. Methods have been developed to derive this information from NMR spectra of proteins. Using series expansion of the time dependent density matrix, and exploiting the simple topology of amino acid spin-systems, formulae for estimation of (3)J(HN-Halpha) and (3)J(Halpha-Hbeta) from HSQC-TOCSY spectra are derived. The results obtained on a protein entailing both alpha-helix and beta-sheet secondary structure elements agree very well with J-coupling constants computed from the X-ray structure. The method compares well with existing methods and requires only 2D spectra which would be typically otherwise recorded for structural studies.     

H2O2 but not $${\hbox{O}_{2}^{-}}$$ elevated by oxidized LDL enhances human aortic smooth muscle cell proliferation

The oxidation of low density lipoprotein (LDL) as a key event in atherosclerosis suggests that antioxidant interventions may reduce the risk of atherosclerosis. However, the better strategies among antioxidant remedies for atherosclerosis remains difficult to be determined. Here, we show that oxidized LDL increases the steady-state level of intracellular hydrogen peroxide through stimulating the protein expressions of Nox1 and Cu/Zn superoxide dismutase (SOD) in human aortic smooth muscle cells (SMCs). The intracellular content of hydrogen peroxide rather than superoxide is a key modulator for vascular SMC (VSMC) proliferation, implying that without co-expression of catalase, increased Cu/Zn-SOD activity alone may not be beneficial to reduce the growth of VSMC in an atherosclerotic plaque.     

Towards superconductivity in hydrides: computational studies of two hypothetical ternary compounds, {\text{Yb}}^{{{\text{II}}}} {\text{BeH}}_{4} and {\text{Cs}}_{3} {\text{Yb}}^{{{\text{III}}}} {\text{H}}_{6}

Two examples of novel, as yet unsynthesized ternary lanthanide hydrides--Yb(II)BeH4 and Cs3Yb(III)H6--are investigated computationally. Their unprecedented electronic structure is discussed and the potential superconductivity of Cs3Yb(III)H6 explored. Methods of synthesis are postulated for both compounds.     

Ab initio molecular dynamics of the reactivity of vitamin C toward hydroxyl and $$ {HO}_2/{O}_2^{-} $$ radicals

Vitamin C is one of the most abundant exogenous antioxidants in the cell, and it is of the utmost importance to elucidate its mechanism of action against radicals. In this study, the reactivity of vitamin C toward OH and \( {HO}_2/{O}_2^{-} \) radicals in aqueous medium was analyzed by ab initio molecular dynamics using CPMD code. The simulations led to results similar to those of static studies or experiments for the pair of \( {HO}_2/{O}_2^{-} \) radicals but bring new insights for the reactivity with hydroxyl radical: the reaction takes place before the formation of an adduct and consists of two steps: first an electron is transferred to hydroxyl radical and then the ascorbyl radical loses a proton.

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Graphical Abstract Reactivity of vitamin C toward hydroxyl and \( {HO}_2/{O}_2^{-} \) radicals

     

ROS Scavenging and $${\text{NH}}_{4}^{ + }$$ Nitrogen Fertilizer Roles in Alleviation of Cd-Induced Oxidative Stress in Arabidopsis thaliana

Russian Journal of Plant Physiology - Arabidopsis thaliana (L.) Heynh. receiving ammonium, were transferred on modified Hoagland nutrient solution containing Cd (25 µM) alone or supplemented...     

{Omega}-oxidation of {alpha}-chlorinated fatty acids: identification of {alpha}-chlorinated dicarboxylic acids

Myeloperoxidase-derived HOCl targets tissue- and lipoprotein-associated plasmalogens to generate α-chlorinated fatty aldehydes, including 2-chlorohexadecanal. Under physiological conditions, 2-chlorohexadecanal is oxidized to 2-chlorohexadecanoic acid (2-ClHA). This study demonstrates the catabolism of 2-ClHA by ω-oxidation and subsequent β-oxidation from the ω-end. Mass spectrometric analyses revealed that 2-ClHA is ω-oxidized in the presence of liver microsomes with initial ω-hydroxylation of 2-ClHA. Subsequent oxidation steps were examined in a human hepatocellular cell line (HepG2). Three different α-chlorinated dicarboxylic acids, 2-chlorohexadecane-(1,16)-dioic acid, 2-chlorotetradecane-(1,14)-dioic acid, and 2-chloroadipic acid (2-ClAdA), were identified. Levels of 2-chlorohexadecane-(1,16)-dioic acid, 2-chlorotetradecane-(1,14)-dioic acid, and 2-ClAdA produced by HepG2 cells were dependent on the concentration of 2-ClHA and the incubation time. Synthetic stable isotope-labeled 2-ClHA was used to demonstrate a precursor-product relationship between 2-ClHA and the α-chlorinated dicarboxylic acids. We also report the identification of endogenous 2-ClAdA in human and rat urine and elevations in stable isotope-labeled urinary 2-ClAdA in rats subjected to intraperitoneal administration of stable isotope-labeled 2-ClHA. Furthermore, urinary 2-ClAdA and plasma 2-ClHA levels are increased in LPS-treated rats. Taken together, these data show that 2-ClHA is ω-oxidized to generate α-chlorinated dicarboxylic acids, which include α-chloroadipic acid that is excreted in the urine.     

IDENTITY OF {varepsilon}-CAROTENE AND {varepsilon}1-CAROTENE

-Carotene was isolated from previously known sources and itsspectral and adsorption properties compared with those of asimilar carotene recently observed in Cryptomonas ovata. Identitywas established. Similar comparisons with synthetic ₁-carotenepoint to the identity of the natural and synthetic compoundsand permit assignment of KARRER and EUGSTER's formulation for₁-carotene to the naturally occurring representative. ¹ Dedicated to Prof. H. TAMIYA on the occasion ot his 60th birthday. ²Contribution from the Scripps Institution of Oceanography,University of California, San Diego. (Received January 22, 1963; )     

Simulation of intracellular $$\hbox {Ca}^{2+}$$ transients in osteoblasts induced by fluid shear stress and its application

Intracellular \(\hbox {Ca}^{2+}\) transient induced by fluid shear stress (FSS) plays an important role in mechanical regulation of osteoblasts, but the cellular mechanism remains incompletely understood. Here, we constructed a mathematical model combined with experiments to elucidate it. Our simulated and experimental results showed that it was the delay of membrane potential repolarization to produce the refractory period of FSS-induced intracellular calcium transients in osteoblasts. Moreover, the results also demonstrated that the amplitude of FSS-induced intracellular calcium transient is crucial to the proliferation, while its duration is critical to the differentiation, of osteoblasts. Overall, the present study provides a way to understand the cellular mechanism of intracellular calcium transients in osteoblast induced by FSS and explains some of related physiological events.     

Column Chromatographic Separation of Chlorophyllide {alpha} and Pheophorbide {alpha}

Chlorophyllide a, pheophorbide a, chlorophyll a and pheophytina were separated in a short time by anion-exchange chromatographywith a short column of DEAE-Sepharose CL-6B. (Received February 16, 1984; Accepted April 13, 1984)     

Endor characterization and D2O exchange in the \begin{array}{*{20}c} {\mathop Z\nolimits^{\begin{array}{*{20}c} + \\ . \\ \end{array} } } \\ \end{array} /{\kern 1pt} \begin{array}{*{20}c} {\mathop D\nolimits^{\begin{array}{*{20}c} + \\ . \\ \end{array} } } \\ \end{array} radical in photosystem II

The early suggestion by Lozier and Butler (Photochem. Photobiol. 17, 133–137 (1973)) that EPR Signal II arises from radicals associated with the water-splitting process in PSII has been confirmed and extended over the intervening years. Recent work has identified the Signal II radicals, \(\begin{array}{*{20}c} {\mathop D\nolimits^{\begin{array}{*{20}c} + \\ . \\ \end{array} } } \\ \end{array}\) and \(\begin{array}{*{20}c} {\mathop Z\nolimits^{\begin{array}{*{20}c} + \\ . \\ \end{array} } } \\ \end{array}\) , with plastosemiquinone cation species. In the experiments presented here we have used ENDOR spectroscopy and D₂O/H₂O exchange to characterize these paramagnets in more detail. The ENDOR matrix region, which arises from protons which interact weakly with the unpaired electron spin, is well-resolved at 4 K and at least seven resonances are apparent. A number of hyperfine couplings in the 3–8 MHz range are observed and are suggested to arise from methyl or hydroxyl protons which occur as substituents on the plastosemiquinone cation ring or from amino acid protons hydrogen-bonded to the 1,4-hydroxyl groups. Orientation selection experiments are consistent with these possibilities. D₂O/H₂O exchange shows that the D⁺/Z⁺ site is accessible to solvent. However, the exchange occurs slowly and is not complete even after 72 hours which suggests that the free radicals are functionally isolated from solvent water.     

Coupling of secondary active transport with\Delta \tilde \mu _{H^ + }

Most nutrients and ions in bacteria, yeasts, algae, and plants are transported uphill at the expense of a gradient of the electrochemical potential of protons deltamu-H+ (a type of secondary active transport). Diagnosis of such transports rests on the determination of the transmembrane electrical potential difference deltapsi and the difference of pH at the two membrane sides. The behavior of kinetic parameters K(T) (the half-saturation constant) and J(max), (the maximum rate of transport) upon changing driving ion concentrations and electrical potentials may be used to determine the molecular details of the transport reaction. Equilibrium accumulation ratios of driven solutes are expected to be in agreement with the deltapsi and deltapH measured independently, as well as with the Haldane-type expression involving K(T) and J(max). Different stoichiometries of H+/solute, as well as intramembrane effects of pH and deltapsi, may account for some of the observed inconsistencies.     

Nutritional strategy for the preferential uptake of $${{\text{NO}}_{3}}^{ - } {\text{{-}N}}$$ NO 3 - -N by Phaeocystis globosa

Hydrobiologia - Phytoplankton productivity standardized to chlorophyll a and photon flux (mg C mg chl. a−1 mol photons−1) of natural communities from northern Bothnian Sea under dynamic...     

Delay decomposition approach to $$\mathcal {H}_{\infty }$$ filtering analysis of genetic oscillator networks with time-varying delays

In this paper, the \(\mathcal {H}_{\infty }\) filtering problem is treated for N coupled genetic oscillator networks with time-varying delays and extrinsic molecular noises. Each individual genetic oscillator is a complex dynamical network that represents the genetic oscillations in terms of complicated biological functions with inner or outer couplings denote the biochemical interactions of mRNAs, proteins and other small molecules. Throughout the paper, first, by constructing appropriate delay decomposition dependent Lyapunov–Krasovskii functional combined with reciprocal convex approach, improved delay-dependent sufficient conditions are obtained to ensure the asymptotic stability of the filtering error system with a prescribed \(\mathcal {H}_{\infty }\) performance. Second, based on the above analysis, the existence of the designed \(\mathcal {H}_{\infty }\) filters are established in terms of linear matrix inequalities with Kronecker product. Finally, numerical examples including a coupled Goodwin oscillator model are inferred to illustrate the effectiveness and less conservatism of the proposed techniques.     

Converting a {beta}-glycosidase into a {beta}-transglycosidase by directed evolution

Directed evolution was applied to the beta-glycosidase of Thermus thermophilus in order to increase its ability to synthesize oligosaccharide by transglycosylation. Wild-type enzyme was able to transfer the glycosyl residue with a yield of 50% by self-condensation and of about 8% by transglycosylation on disaccharides without nitrophenyl at their reducing end. By using a simple screening procedure, we could produce mutant enzymes possessing a high transferase activity. In one step of random mutagenesis and in vitro recombination, the hydrolysis of substrates and of transglycosylation products was considerably reduced. For certain mutants, synthesis by self-condensation of nitrophenyl glycosides became nearly quantitative, whereas synthesis by transglycosylation on maltose and on cellobiose could reach 60 and 75%, respectively. Because the most efficient mutations, F401S and N282T, were located just in front of the subsite (-1), molecular modeling techniques were used to explain their effects on the synthesis reaction; we can suggest that repositioning of the glycone in the (-1) subsite together with a better fit of the acceptor in the (+1) subsite might favor the attack of a glycosyl acceptor in the mutant at the expense of water. Thus these new transglycosidases constitute an interesting alternative for the synthesis of oligosaccharides by using stable and accessible donor substrates.     

Synergistic Ca2+ responses by G{alpha}i- and G{alpha}q-coupled G-protein-coupled receptors require a single PLC{beta} isoform that is sensitive to both G{beta}{gamma} and G{alpha}q

Cross-talk between Gα(i)- and Gα(q)-linked G-protein-coupled receptors yields synergistic Ca(2+) responses in a variety of cell types. Prior studies have shown that synergistic Ca(2+) responses from macrophage G-protein-coupled receptors are primarily dependent on phospholipase Cβ3 (PLCβ3), with a possible contribution of PLCβ2, whereas signaling through PLCβ4 interferes with synergy. We here show that synergy can be induced by the combination of Gβγ and Gα(q) activation of a single PLCβ isoform. Synergy was absent in macrophages lacking both PLCβ2 and PLCβ3, but it was fully reconstituted following transduction with PLCβ3 alone. Mechanisms of PLCβ-mediated synergy were further explored in NIH-3T3 cells, which express little if any PLCβ2. RNAi-mediated knockdown of endogenous PLCβs demonstrated that synergy in these cells was dependent on PLCβ3, but PLCβ1 and PLCβ4 did not contribute, and overexpression of either isoform inhibited Ca(2+) synergy. When synergy was blocked by RNAi of endogenous PLCβ3, it could be reconstituted by expression of either human PLCβ3 or mouse PLCβ2. In contrast, it could not be reconstituted by human PLCβ3 with a mutation of the Y box, which disrupted activation by Gβγ, and it was only partially restored by human PLCβ3 with a mutation of the C terminus, which partly disrupted activation by Gα(q). Thus, both Gβγ and Gα(q) contribute to activation of PLCβ3 in cells for Ca(2+) synergy. We conclude that Ca(2+) synergy between Gα(i)-coupled and Gα(q)-coupled receptors requires the direct action of both Gβγ and Gα(q) on PLCβ and is mediated primarily by PLCβ3, although PLCβ2 is also competent.     

N$_{3}^{-}$ azide anion confined inside finite-size carbon nanotubes

In this work, the confinement of an N\(_{3}^{-}\) azide anion inside finite-size single-wall zigzag and armchair carbon nanotubes of different diameters has been studied by wave function and density functional theory. Unrelaxed and relaxed interaction energies have been computed, resulting in a favorable interaction between the guest and host system. In particular, the largest interaction has been observed for the confinement in an armchair (5,5) carbon nanotube, for which a natural population analysis as well as an investigation based on the molecular electrostatic potential has been carried out. The nature of the interaction between the two fragments appears to be mainly electrostatic, favored by the enhanced polarizability of the nanotube wall treated as a finite system and passivated by hydrogen atoms. The results obtained are promising for possible applications of this complex as a starting point for the stabilization of larger polynitrogen compounds, suitable as a high-energy density material.