Synthesis, crystal structure, magnetic and redox properties of copper(II) complexes of N-alkyl(aryl) tBu-salicylaldimines

A series of novel copper(II) complexes, L₂Cu with newly synthesized 3,5--salicylaldimine (or 5--salicylaldimine) ligands derived from 2,4-di-tert-butyl phenol (or 4-tert-butyl phenol) and alkyl (aryl) amines have been prepared and their spectroscopic (IR, UV-Vis, ESI-MS), X-ray, magnetic and redox properties have been investigated. The X-ray crystallography analysis shows that all complexes are monomeric and their copper(II) centers are surrounded by phenolate oxygens and imine nitrogen atoms. Therefore, the coordination sphere around the copper atoms is N₂O₂ as seen in galactose oxidase active site. In addition, the geometric configurations of all complexes are square planar or slightly distorted square planar. The crystal system for all complexes is monoclinic, except for which is orthorhombic. The temperature dependence of magnetic susceptibility of complexes confirms the mononuclear structure of complexes. Oxidation of the Cu(II) complexes yielded the corresponding Cu(II)-phenoxyl radical species during the cyclic voltammetry experiments.     

NAD(P)H- and superoxide-dependent nitric oxide degradation by rat liver mitochondria

Mitochondria consume nitric oxide (NO) mainly through reaction with superoxide anion (). Here, we analyzed the sources for NO degradation by isolated rat liver mitochondria. Electron leakage from complex III and reverse electron transport to complex I accounted for -dependent NO degradation by mitochondria in the presence of a protonmotive force. Mitochondria incubated with NAD(P)H also presented intense generation and NO degradation rates that were insensitive to respiratory inhibitors and abolished after proteinase treatment. These results suggest that an outer membrane-localized NAD(P)H oxidase activity, in addition to the electron leakage from the respiratory chain, promotes -dependent NO degradation in rat liver mitochondria.     

Curcumin dramatically enhances retinoic acid-induced superoxide generating activity via accumulation of p47-phox and p67-phox proteins in U937 cells

The membrane bound cytochrome b558 composed of large gp91-phox and small p22-phox subunits, and cytosolic proteins p40-, p47- and p67-phox are important components of superoxide ()-generating system in phagocytes and B lymphocytes. A lack of this system in phagocytes is known to cause serious life-threatening infections. Here, we describe that curcumin, a polyphenol responsible for the yellow color of curry spice turmeric, dramatically activates the -generating system during retinoic acid (RA)-induced differentiation of human monoblastic leukemia U937 cells to macrophage-like cells. When U937 cells were cultured in the presence of RA and curcumin, the -generating activity increased more than 4-fold compared with that in the absence of the latter. Semiquantitative RT-PCR showed that co-treatment with RA and curcumin slightly enhanced gene expressions of the five components compared with those of the RA-treatment only. On the other hand, immunoblot analysis revealed that co-treatment with RA and curcumin caused remarkable accumulation of protein levels of p47-phox (to 7-fold) and p67-phox (to 4-fold) compared with those of the RA-treatment alone. These results suggested that curcumin dramatically enhances RA-induced -generating activity via accumulation of cytosolic p47-phox and p67-phox proteins in U937 cells. Therefore, it should have the potential as an effective modifier in therapy of leukemia and/or as an immunopotentiator.     

A facile synthesis of 5-thio-l-fucose and 5-thio-d-arabinose from d-arabinose

5-Thio-l-fucopyranose tetraacetate was synthesized in 11 steps from or d-arabinose diethyl dithioacetal by one-carbon elongation at C-5. Highly diastereo-selective addition of MeLi in ether to a derivative was achieved to give the corresponding 6-deoxy-β-d-altrofuranose isomer in good yield. A sulfur atom was introduced at C-5 of 6-deoxy-d-altrofuranose derivatives via substitution of a 5-tosylate with KSAc in HMPA with inversion of configuration, giving 5-thio-l-fucopyranose. A derivative was also prepared from 6-deoxy-β-d-altrofuranose derivatives. 5-Thio-d-arabinopyranose tetraacetate, the 5-demethyl analog of 5-thio-l-fucose, was also synthesized from in 5 steps. 5-Thio-d-arabinose showed weak inhibitory activity against α-l-fucosidase from bovine kidney (K_{i = 0.77 mM}).     

The uremic solute indoxyl sulfate acts as an antioxidant against superoxide anion radicals under normal-physiological conditions

The effect of the uremic solute indoxyl sulfate (IS) on scavenging superoxide anion radicals () generated from both the xanthine/xanthine oxidase (X/XO) system and activated neutrophils was investigated by electron paramagnetic resonance spectroscopy, combined with 2-ethoxycarbonyl-2-methyl-3,4-dihydro-2H-pyrrole-1-oxide (EMPO). The findings show that the presence of normal-physiological serum concentrations of IS (0.1-10 μM) resulted in decreased formation of EMPO-superoxide adduct without affecting XO activity. Furthermore, IS showed scavenging activity against cell-derived generated from activated neutrophils. In addition, IS also eliminated hydroxyl radicals. These findings suggest that IS acts as a novel endogenous antioxidant under normal-physiological conditions.     

Comprehensive inhibitor profiling of the Proteus mirabilis metalloprotease virulence factor ZapA (mirabilysin)

In this study we report for the first time the comprehensive inhibitor profiling of the Proteus mirabilis metalloprotease virulence factor ZapA (mirabilysin) using a 160 compound focused library of N-alpha mercaptoamide dipeptides, in order to map the and binding site preferences of this important enzyme. This study has revealed a preference for the aromatic residues tyrosine and tryptophan in and aliphatic residues in . From this library, six compounds were identified which exhibited sub- to low-micromolar K_i values. The most potent inactivator, SH–CO₂–Y–V–NH₂ was capable of preventing ZapA-mediated hydrolysis of heat-denatured IgA, indicating that these inhibitors may be capable of protecting host proteins against ZapA during colonisation and infection.     

n-acylation of β-amino alcohol by acyl migration following enzyme-catalyzed esterification

Lipase-catalyzed n-acylations of β-amino alcohols such as ethanolamine and l-serine were investigated. To prepare n-acyl derivatives by taking advantage of the acyl migration, we first carried out a screening of suitable enzymes for the desired reaction. As a result, we found a higher activity for n-acylation with Lipase L. This lipase had higher hydrolytic activity for the o-acyl compound but not the n-acyl compound. The observation shows that n-acylation results from the esterification and successive acyl migration into the amino group. Using Lipase L, we then investigated the n-acylation of ethanolamine or l-serine with fatty acids as acyl donors. The reaction parameters for the n-acylation were clarified.     

Inhibition by purine nucleotides of the release of reactive oxygen species from muscle mitochondria: indication for a function of uncoupling proteins as superoxide anion transporters

Release of reactive oxygen species (ROS), measured as the sum of hydrogen peroxide (H₂O₂) and superoxide anion radical (), from respiring rat heart and skeletal muscle mitochondria was significantly decreased by millimolar concentrations of GTP or GDP. Attempts to differentiate between the two forms of ROS showed that the release of rather than that of H₂O₂ was affected. Meanwhile, intramitochondrial ROS accumulation, measured by inactivation of aconitase, increased. These results suggest that guanine nucleotides inhibit the release of from mitochondria. As these nucleotides are known inhibitors of uncoupling proteins (UCPs), it is proposed that UCPs may function as carriers of , thus enabling its removal from the matrix compartment.     

Mixed-valence porphyrin π-cation radical derivatives: Electrochemical investigations

The electrochemistry of [Cu(OEP)] and [Ni(OEP)] are compared with the mixed-valence π-cations and . These electrochemical studies, carried out with cyclic voltammetry and hydrodynamic voltammetry, show that the mixed valence π-cations have distinct electrochemical properties, although the differences between the [M(OEP)]^+/0 and processes are subtle.     

Sterol chemical configuration influences the thermotropic phase behaviour of dipalmitoylphosphatidylcholine bilayers containing 5α-cholestan-3β- and 3α-ol

It is commonly believed that all membrane sterols are rigid all-trans ring systems with a fully extended alkyl side-chain and that they similarly influence phospholipid bilayer physical properties. Here, we report the sterol concentration-dependent, thermotropic phase behaviour of binary dipalmitoylphosphatidylcholine (DPPC)/sterol mixtures containing two similar 5α-H sterols with different functional group orientations (3α-OH or 3β-OH), which adopt an ideal all-trans planar ring conformation but lack the deformed ring B conformation of cholesterol (Chol) and epicholesterol (Echol), using differential scanning calorimetry (DSC). Our deconvolution of the DSC main phase transition endotherms show differences in the proportions of sterol-poor (sharp) and sterol-rich (broad) domains in the DPPC bilayer with increasing sterol concentration, which delineate gel/liquid-crystalline (P_β′/L_α) and disordered gel (L_β)/liquid-ordered (l_o) phase regions. There are similarities in the DPPC main phase transition temperature, cooperativity and enthalpy for each 3β-ol and 3α-ol pair with increasing sterol concentration and differences in the parameters obtained for both the sterol-poor and sterol-rich regions. The sterol-poor domain persists over a greater concentration range in both 3α-ol/DPPC mixtures, suggesting that either those domains are more stable in the 3α-ols or that those sterols are less miscible in the sterol-rich domain. Corresponding parameters for the sterol-rich domain show that at sterol concentrations up to 20 mol%, the 5α-H,3β-ol is more effective at reducing the phase transition enthalpy of the broad component () than Chol, but is less effective at higher concentrations. Although mixtures containing Echol and 5α-cholestan-3α-ol have similar positive slopes below 7 mol% sterol, suggesting that they abolish the L_β/l_o phase transition equally effectively at low concentrations, Echol is more effective than the saturated 3α-ol at higher sterol concentrations. A comparison of obtained for the saturated and unsaturated pairs suggests that the latter sterols stabilize the l_o phase and broaden and abolish the DPPC main phase transition more effectively than the saturated sterols at physiologically relevant concentrations, supporting the idea that the double bond of Chol and Echol promotes greater sterol miscibility and the formation of l_o phase lipid bilayers relative to corresponding saturated sterols in biological membranes.     

Mutations at position 1122 in the catalytic domain of the mouse ras-specific guanine nucleotide exchange factor CDC25 originate both loss-of-function and gain-of-function proteins

The role of two residues within the catalytic domain of CDC25^Mm, a mouse ras-specific guanine nucleotide exchange factor (GEF), was investigated by site-directed mutagenesis. The function of the mutant proteins was tested in vivo in both a Saccharomyces cerevisiae cdc25 complementation assay and in a mammalian fos-luciferase assay, and in in vitro assays on human and yeast Ras proteins. Mutants CDC25 and CDC25 were shown to be (partly) inactive proteins, similar to their yeast homologs. Mutant CDC25 showed higher nucleotide exchange activity than the wild type protein on the basis of both in vitro and in vivo assays. Thus, alanine and valine substitutions at position 1122 within the GEF catalytic domain originate mutations with opposite biological properties, indicating an important role for position 1122 in GEF function.     

Intracellular anion fluorescence assay for sodium/iodide symporter substrates

The sodium/iodide symporter (NIS) is primarily responsible for iodide accumulation in the thyroid gland for the synthesis of thyroid hormones; however, it can also transport other lyotropic anions in the thyroid gland and nonthyroid tissues. Some NIS substrates have important physiological or clinical roles, and others are environmental contaminants with health-related consequences. The aim of this study was to assess the utility of a yellow fluorescent protein variant, YFP–H148Q/I152L, as a biosensor to monitor the cellular uptake of NIS substrates, including thiocyanate (SCN⁻), nitrate (), chlorate (), perchlorate (), and perrhenate (). The fluorescence of purified YFP–H148Q/I152L was suppressed by anions with an order of potency of > = I⁻ = SCN⁻ = > ? Cl⁻. Anions also suppressed the fluorescence of YFP–H148Q/I152L expressed in FRTL-5, a thyroid cell line with high NIS expression. Quantitation of intracellular concentrations revealed differences among anions in the affinity and maximal velocity of NIS-mediated uptake as well as in the rate constant for passive efflux. These results suggest that YFP–H148Q/I152L can serve as an intracellular biosensor of NIS-transported anions and may be useful to study the physiology of endogenous anions as well as the health-related consequences of environmental anions.     

Compressible gas gills of diving insects: Measurements and models

Many diving insects collect a bubble of air from the surface to supply their oxygen requirements while submerged. It has been theorised that these air bubbles may also act as compressible gas gills, as the low oxygen partial pressure (PO₂) within the bubble caused by the insect's respiration creates a gradient capable of driving the diffusion of oxygen from the water into the bubble. Under these conditions nitrogen diffuses in the opposite direction, resulting in a situation where the volume of the bubble is continually shrinking while oxygen is obtained. This study measures changes in volume and PO₂ within the gas gills held by a tethered water bug, Agraptocorixa eurynome. Both gill volume and PO₂ drop rapidly at the beginning of a dive, but eventually the PO₂ reaches an apparently stable level while volume continually declines at a slower rate. Active ventilation of the gill is crucial to maintaining oxygen uptake. These measurements are used to calculate oxygen flux into the gas gill and the oxygen consumption rate of the bug. The effectiveness of a gas gill as a respiratory organ is also demonstrated by determining the critical PO₂ of the water bug and comparing this with measured gas gill PO₂ and calculated .     

Activity of Debaryomyces hansenii UFV-1 α-galactosidases against α-d-galactopyranoside derivatives

α-d-Galactopyranosides were synthesized and their inhibitory activities toward the Debaryomyces hansenii UFV-1 extracellular and intracellular α-galactosidases were evaluated. Methyl α-d-galactopyranoside was the most potent inhibitor compared to the others tested, with values of 0.82 and 1.12 mmol L⁻¹, for extracellular and intracellular enzymes, respectively. These results indicate that the presence of a hydroxyl group in the C-6 position of α-d-galactopyranoside derivatives is important for the recognition by D. hansenii UFV-1 α-galactosidases.     

Kinetics and mechanism of the aquation of the trinuclear cation, [μ3-oxo-triaqua-hexakis(acetato)tris(iron(III))]in perchloric acid media

The aquation of the title complex cation in aqueous perchloric acid proceeded via two steps, both postulated to be the proton attack on the oxygen atom which binds the acetate ligand to the metal centre, followed by Fe-O bond cleavage. This was followed by rapid decomposition to produce aqueous iron(III) and acetate ions. The first-order rate constants for the first and second steps at 25 °C are: k₁ = (4.16 ± 0.58) × 10⁻² s⁻¹ and k₂ = (2.09 ± 0.42) × 10⁻³ s⁻¹, respectively, and their corresponding activation parameters are . The spontaneous hydrolysis rate constants for the first and second steps were also determined at 25 °C and ionic strength of 1 mol dm⁻³ and they are k₀ = (3.10 ± 0.82) × 10⁻³ s⁻¹ and , respectively. The corresponding activation parameters are .     

A direct enzymatic synthesis of β-d-galactopyranosyl-d-xylopyranosides and their use to evaluate rat intestinal lactase activity in vivo

By enzymatic β-d-galactosylation of d-xylose a mixture of 4-, 3-, and (1, 4, and 7, respectively) was obtained in 50% isolated yield. Disaccharides 1, 4, and 7 are substrates of intestinal lactase isolated from lamb small intestine with K_m values of 250.0, 4.5, and 14.0 mM, respectively. The mixture was used to monitor the normal decline in lactase activity in rats that takes place after weaning. The data obtained by this method correlated with the levels of intestinal lactase activity in the same animals after being sacrificed.     

A trade-off relationship between energetic cost and entropic cost for in vitro evolution

In this paper, we consider two complementary cost functions for the landscape exploring processes to obtain the global optimum sequence through in vitro evolution protocol: one is the entropic cost C_etp, which is based on the deviation from the uniformity of a mutant distribution in sequence space, and the other is the energetic cost C_eng, which is based on the total number of sequences to be generated and evaluated. Based on a prior knowledge about the structure of a given fitness landscapes, the conductor of the experiment can think up the efficient search algorithm (ESA), which requires the minimum number of points (=sequences) to be searched up to the global optimum. For five typical fitness landscapes, we considered their respective (putative) ESA, and based on the ESA. As a result, we found a trade-off relationship between and for every case, that is, is approximately equal to the logarithm of the volume of the sequence space. and are interpreted in terms of the information-theoretic concepts.     

Protozoan predation on nitrification performance and microbial community during bioaugmentation

The effects of predation on nitrification performance and microbial community during bioaugmentation were investigated. Although most of the nitrification ability of the seed source was lost in the seeded reactors, bioaugmentation significantly enhanced the activity and community of the nitrifiers. The ammonium uptake rate (AUR) increased from 2.59 to 15.25 mg -N/L h and 2.88 to 13.36 mg -N/L h, and the nitrite uptake rate (NUR) increased from 0.80 to 4.02 mg -N/L h and 0.76 to 4.34 mg -N/L h for the reactors with and without protozoa inhibition, respectively. The population of nitrifiers increased, and the dominant nitrite oxidizing bacteria (NOB) transferred from Nitrospira to Nitrobacter. Predation had an evident influence on the microbial community of nitrifiers, especially the K-strategist, which was more vulnerable to predation than r-strategist during bioaugmentation due to its low growth rate. However, predation did not have a significant effect on the nitrification performance.     

Novel structural variation of silver(I)-pyridine complexes in nitromethane as studied by X-ray absorption spectroscopy

The XAFS spectra were measured at around the Ag K-edge of the Ag(I) ion in nitromethane (NM) with a variety of concentrations of pyridine (PY). In NM without PY, the Ag(I) ion is tetrahedrally solvated by four NM molecules similar to those in most solvents. The Ag-O bond length in NM solvent is longer than that in aqueous solution, indicating the low donating ability of NM. The mono-, bis-, tris-, and tetrakis-pyridine complexes are formed in NM by the addition of PY. The EXAFS analyses reveal that the structure of the formed PY complex in NM is linear for Ag(py)(nm)⁺, linear for , triangular for , and tetrahedral for . The longer Ag-O bond length for Ag(py)(nm)⁺ than that for and the release of bound NM molecules at the formation of Ag(py)(nm)⁺ are interpreted to be due to the strong σ donating property of PY. The Ag-N bond length (220 pm) for is intermediate between 216 pm for and 228 pm for . The formation equilibria of and are analyzed on the basis of the changeover of EXAFS spectra as a function of the total concentrations of Ag⁺ and PY in NM.