Theoretical reduction potentials for nitrogen oxides from CBS-QB3 energetics and (C)PCM solvation calculations

The complete basis set method, CBS-QB3, is used in combination with two continuum solvation models for aqueous solvation to compute reduction potentials previously determined experimentally for 36 nitrogen oxides and related species of the general formula H(V)C(W)N(X)O(Y)Cl(Z). The PCM model led to the correlation E(o)exp (vs NHE) = 0.84E(o)calc + 0.03 V with an average error of 0.12 V (2.8 kcal/mol) and a maximum error of 0.32 V (7.4 kcal/mol). The CPCM/UAKS model gave E(o)exp (vs NHE) = 0.83E(o)calc + 0.11 V with the same average error. This general method was used to predict reduction potentials (+/-0.3 V) for nitrogen oxides for which reduction potentials are not known with certainty: NO2/NO2- (0.6 V), NO3/NO3- (1.9 V), N2O3-/N2O3(2-) (0.5 V), HN2O3/HN2O3- (0.9 V), HONNO,H+/HONNOH (1.6 V), 2NO,H+/HONNO (0.0 V), 2NO/ONNO- (-0.1 V), ONNO-/ONNO(2-) (-0.4 V), HNO,H+/H2NO (0.6 V), H2NO,H+/H2NOH (0.9 V), HNO,2H+/H2NOH (0.8 V), and HNO/HNO- (-0.7 V).     

高效液相色谱法测定大鼠神经组织中的硝酸盐和亚硝酸盐

 建立了大鼠神经组织中亚硝酸盐和硝酸盐的高效液相色谱测定方法,以用于研究一氧化氮在糖尿病慢性神经病变中的作用。在1 μmol/L～25 μmol/L的浓度范围内,NO2-和NO3-的峰面积与浓度的线性相关系数>0.991;最低检测浓度分别为0.2 μmol/L和0.5 μmol/L;日内、日间相对标准偏差<14%。对各实验组大鼠的初步测定结果表明,糖尿病组及糖尿病胰岛素(IGF)治疗组的NO2-和NO3-水平均低于对照组。 关键词：高效液相色谱法;一氧化氮;硝酸盐;亚硝酸盐;糖尿病神经病变     

EXAFS study of aqueous Zr(IV) and Th(IV) complexes in alkaline CaCl(2) solutions: Ca(3)[Zr(OH)(6)](4+) and Ca(4)[Th(OH)(8)](4+)

A hitherto unknown type of aqueous complex, ternary Ca-MIV-OH complexes (M = Zr and Th), causes unexpectedly high solubilities of zirconium(IV) and thorium(IV) hydrous oxides in alkaline CaCl2 solutions (pHc = 10-12, [CaCl2] > 0.05 mol.L(-1), and pHc = 11-12, [CaCl2] > 0.5 mol.L(-1), respectively). The dominant aqueous species are identified as Ca3[Zr(OH)6]4+ and Ca4[Th(OH)8]4+ and characterized by extended X-ray absorption fine structure (EXAFS) spectroscopy. The number of OH- ligands in the first coordination sphere detected by EXAFS, NO = 6 (6.6 +/- 1.2) for Zr and NO = 8 (8.6 +/- 1.2) for Th, are consistent with the observed slopes of 2 and 4 in the solubility curves log [M]tot vs pHc. The presence of polynuclear hydrolysis species and the formation of chloride complexes can be excluded. EXAFS spectra clearly show a second coordination shell of calcium ions. The [Zr(OH)6]2- and [Th(OH)8]4- complexes with an unusually large number of OH- ligands are stabilized by the formation of associates or ion pairs with Ca2+ ions. The number of neighboring Ca2+ ions around the [Zr(OH)6]2- and [Th(OH)8]4- units is determined to be NCa = 3 (2.7 +/- 0.6) at a distance of RZr-Ca = 3.38 +/- 0.02 A and NCa = 4 (3.8 +/- 0.5) at a distance of RTh-Ca = 3.98 +/- 0.02 A. The Ca3[Zr(OH)6]4+ and Ca4[Th(OH)8]4+ complexes have first (M-O) and second (M-Ca) coordination spheres with the Ca2+ ions bound to coordination polyhedra edges.     

The inducing NO-vasodilation by chemical reduction of coordinated nitrite ion in cis-[Ru(NO(2))L(bpy)(2)](+) complex

The synthesis of [Ru(NO(2))L(bpy)(2)](+) (bpy = 2,2'-bipyridine and L = pyridine (py) and pyrazine (pz)) can be accomplished by addition of [Ru(NO)L(bpy)(2)](PF(6))(3) to aqueous solutions of physiological pH. The electrochemical processes of [Ru(NO(2))L(bpy)(2)](+) in aqueous solution were studied by cyclic voltammetry and differential pulse voltammetry. The anodic scan shows a peak around 1.00 V vs. Ag/AgCl attributed to the oxidation process centered on the metal ion. However, in the cathodic scan a second peak around -0.60 V vs. Ag/AgCl was observed and attributed to the reduction process centered on the nitrite ligand. The controlled reduction potential electrolysis at -0.80 V vs. Ag/AgCl shows NO release characteristics as judged by NO measurement with a NO-sensor. This assumption was confirmed by ESI/MS(+) and spectroelectrochemical experiment where cis-[Ru(bpy)(2)L(H(2)O)](2+) was obtained as a product of the reduction of cis-[Ru(II)(NO(2))L(bpy)(2)](+). The vasorelaxation observed in denuded aortic rings pre-contracted with 0.1 mumol L(-1) phenylephrine responded with relaxation in the presence of cis-[Ru(II)(NO(2))L(bpy)(2)](+). The potential of rat aorta cells to metabolize cis-[Ru(II)(NO(2))L(bpy)(2)](+) was also followed by confocal analysis. The obtained results suggest that NO release happens by reduction of cis-[Ru(II)(NO(2))L(bpy)(2)](+) inside the cell. The maximum vasorelaxation was achieved with 1 x 10(-5) mol L(-1) of cis-[Ru(II)(NO(2))L(bpy)(2)](+) complex.     

Bioactive constituents from Rollinia emarginata (Annonaceae)

From an Argentine collection of the tropical tree Rollinia emarginata (Annonaceae), vomifoliol, dehydrovomifoliol, blumenol C, loliolide, 7-epiloliolide, vanillin, dihydroactinolide, as well as other common plant constituents were obtained, and identified by their NMR and MS features compared with authentic samples. Antifeedant and toxic actions were exerted to the polyphagous moth Spodoptera frugiperda by the ethanol extract of the plant, at 250 ppm in the larval diet. Additionally, in greenhouse studies, a 200 ppm aqueous solution of the extract produced a post-emergency herbicidal effect on the annual weed common lambsquarter (Chenopodium album).     

Structural origin of two paramagnetic species in six-coordinated nitrosoiron(II) porphyrins revealed by density functional theory analysis of the g tensors

Potential energy and electron paramagnetic resonance (EPR) g tensor surfaces of model five- and six-coordinated porphyrins were examined. For both types of complexes, the NO ligand is preferably coordinated end-on, with a Fe-N-O bond angle of approximately 140 degrees. In the free five-coordinated structure, NO undergoes free rotation around the axial Fe-N(NO) bond. This motion is strongly coupled to the saddle-type distortion of the porphyrin ligand. Coordination by the second axial ligand (imidazole) raises the calculated barrier for NO rotation to about 1 kcal/mol, which is further increased by displacements of imidazole from the ideal axial position. The potential energy surface for the dissociation of the weakly coordinated imidazole ligand is exceptionally flat, with variation of the Fe-N(Im) bond length between 2.1 and 2.5 A changing the energy by less than 1 kcal/mol. Experimental orientations of both axial ligands, as well as the Fe-N(Im) bond length, are therefore likely to be determined by the environment of the complex. In contrast to the total energy, calculated EPR g-tensors are sensitive to the orientation of the NO ligand and to the Fe-N(Im) bond length. Contrary to a common assumption, the g tensor component closest to the free-electron value does not coincide with the direction of the Fe-N(NO) bond. From comparison of the calculated and experimental g-tensor components for a range of structures, the rhombic ("type I") EPR signal is assigned to a static structure with NO oriented toward the meso-C atom of the prophyrin ring, and RFe-N(Im) approximately 2.1 A (calcd g1 = 1.95, g2 = 2.00, g3 = 2.04; exptl g1 = 1.96-1.98, g2 = 2.00, g3 = 2.06-2.08). The axial ("type II") EPR signal cannot correspond to any of the static structures studied presently. It is tentatively assigned to a partially dissociated six-coordinated complex (RFe-N(Im) > 2.5 A), with a freely rotating NO ligand (calcd g parallel = 2.00, g perpendicular = 2.03; exptl g parallel = 1.99-2.00, g perpendicular = 2.02-2.03).     

Hyponitrite radical, a stable adduct of nitric oxide and nitroxyl

All major properties of the aqueous hyponitrite radicals (ONNO- and ONNOH), the adducts of nitric oxide (NO) and nitroxyl (3NO- and 1HNO), are revised. In this work, the radicals are produced by oxidation of various hyponitrite species in the 2-14 pH range with the OH, N3, or SO4- radicals. The estimated rate constants with OH are 4 x 10(7), 4.2 x 10(9), and 8.8 x 10(9) M(-1) s(-1) for oxidations of HONNOH, HONNO-, and ONNO2-, respectively. The rate constants for N3 + ONNO2- and SO4- + HONNO- are 1.1 x 10(9) and 6.4 x 10(8) M(-1) s(-1), respectively. The ONNO- radical exhibits a strong characteristic absorption spectrum with maxima at 280 and 420 nm (epsilon280 = 7.6 x 10(3) and epsilon420 = 1.2 x 10(3) M(-1) cm(-1)). This spectrum differs drastically from those reported, suggesting the radical misassignment in prior work. The ONNOH radical is weakly acidic; its pKa of 5.5 is obtained from the spectral changes with pH. Both ONNO- and ONNOH are shown to be over 3 orders of magnitude more stable with respect to elimination of NO than it has been suggested previously. The aqueous thermodynamic properties of ONNO- and ONNOH radicals are derived by means of the gas-phase ab initio calculations, justified estimates for ONNOH hydration, and its pKa. The radicals are found to be both strongly oxidizing, E degrees (ONNO-/ONNO2-) = 0.96 V and E degrees (ONNOH, H+/HONNOH) = 1.75 V, and moderately reducing, E degrees (2NO/ONNO-) = -0.38 V and E degrees (2NO, H+/ONNOH) = -0.06 V, all vs NHE. Collectively, these properties make the hyponitrite radical an important intermediate in the aqueous redox chemistry leading to or originating from nitric oxide.     

差分脉冲伏安法同时测定α-山竹黄酮和γ-山竹黄酮

研究了α-山竹黄酮和γ-山竹黄酮在玻璃碳电极上的电化学行为,研究了pH和静置时间等因素的影响,探讨了α-山竹黄酮和γ-山竹黄酮在玻璃碳电极上的氧化机理,建立了差分脉冲伏安法同时测定α-山竹黄酮和γ-山竹黄酮的方法。在pH 3.1的BR缓冲介质中,α-山竹黄酮在0.822 V产生灵敏的氧化峰,γ-山竹黄酮在0.426 V和0.700 V产生灵敏的氧化峰。对α-山竹黄酮,相应的氧化峰的峰高与浓度在5.00×10-6mol/L~2.00×10-4mol/L范围内呈良好的线性关系,线性相关系数为0.9950;对γ-山竹黄酮,其在0.426 V氧化峰的峰高与浓度在2.00×10-5mol/L~6.00×10-4mol/L浓度范围内呈良好的线性关系,线性相关系数为0.9904。该方法测量2.00×10-4mol/L的α-山竹黄酮和γ-山竹黄酮相对标准偏差分别为3.3%和4.1%(n=10)。     

Circulating Levels of Dephosphorylated-Uncarboxylated Matrix Gla Protein in Patients with Acute Coronary Syndrome

Vascular calcification contributes to the pathogenesis of coronary artery disease while matrix Gla protein (MGP) was recently identified as a potent inhibitor of vascular calcification. MGP fractions, such as dephosphorylated-uncarboxylated MGP (dp-ucMGP), lack post-translational modifications and are less efficient in vascular calcification inhibition. We sought to compare dp-ucMGP levels between patients with acute coronary syndrome (ACS), stratified by ST-elevation myocardial infarction (STEMI) and non-ST-elevation myocardial infarction (NSTEMI) status. Physical examination and clinical data, along with plasma dp-ucMGP levels, were obtained from 90 consecutive ACS patients. We observed that levels of dp-ucMGP were significantly higher in patients with NSTEMI compared to STEMI patients (1063.4 ± 518.6 vs. 742.7 ± 166.6 pmol/L, p < 0.001). NSTEMI status and positive family history of cardiovascular diseases were only independent predictors of the highest tertile of dp-ucMGP levels. Among those with NSTEMI, patients at a high risk of in-hospital mortality (adjudicated by GRACE score) had significantly higher levels of dp-ucMGP compared to non-high-risk patients (1417.8 ± 956.8 vs. 984.6 ± 335.0 pmol/L, p = 0.030). Altogether, our findings suggest that higher dp-ucMGP levels likely reflect higher calcification burden in ACS patients and might aid in the identification of NSTEMI patients at increased risk of in-hospital mortality. Furthermore, observed dp-ucMGP levels might reflect differences in atherosclerotic plaque pathobiology between patients with STEMI and NSTEMI.     

Kinetics and mechanism of the interaction of nitric oxide with pentacyanoferrate(II). Formation and dissociation of [Fe(CN)5NO]3 -

The interaction of NO with [Fe(CN)(5)H(2)O](3)(-) (generated by aquation of the corresponding ammine complex) to produce [Fe(CN)(5)NO](3)(-) was studied by UV-vis spectrophotometry. The reaction product is the well characterized nitrosyl complex, described as a low-spin Fe(II) bound to the NO radical. The experiments were performed in the pH range 4-10, at different concentrations of NO, temperatures and pressures. The rate law was first-order in each of the reactants, with the specific complex-formation rate constant, k(f)( )()= 250 +/- 10 M(-)(1) s(-)(1) (25.4 degrees C, I = 0.1 M, pH 7.0), DeltaH(f)() = 70 +/- 1 kJ mol(-)(1), DeltaS(f)() = +34 +/- 4 J K(-)(1) mol(-)(1), and DeltaV(f)() = +17.4 +/- 0.3 cm(3) mol(-)(1). These values support a dissociative mechanism, with rate-controlling dissociation of coordinated water, and subsequent fast coordination of NO. The complex-formation process depends on pH, indicating that the initial product [Fe(CN)(5)NO](3)(-) is unstable, with a faster decomposition rate at lower pH. The decomposition process is associated with release of cyanide, further reaction of NO with [Fe(CN)(4)NO](2)(-), and formation of nitroprusside and other unknown products. The decomposition can be prevented by addition of free cyanide to the solutions, enabling a study of the dissociation process of NO from [Fe(CN)(5)NO](3)(-). Cyanide also acts as a scavenger for the [Fe(CN)(5)](3)(-) intermediate, giving [Fe(CN)(6)](4)(-) as a final product. From the first-order behavior, the dissociation rate constant was obtained as k(d) = (1.58 +/- 0.06) x 10(-)(5) s(-)(1) at 25.0 degrees C, I = 0.1 M, and pH 10.2. Activation parameters were found to be DeltaH(d)() = 106.4 +/- 0.8 kJ mol(-)(1), DeltaS(d)() = +20 +/- 2 J K(-)(1) mol(-)(1), and DeltaV(d)() = +7.1 +/- 0.2 cm(3) mol(-)(1), which are all in line with a dissociative mechanism. The low value of k(d) as compared to values for the release of other ligands L from [Fe(II)(CN)(5)L](n)()(-) suggests a moderate to strong sigma-pi interaction of NO with the iron(II) center. It is concluded that the release of NO from nitroprusside in biological media does not originate from [Fe(CN)(5)NO](3)(-) produced on reduction of nitroprusside but probably proceeds through the release of cyanide and further reactions of the [Fe(CN)(4)NO](2)(-) ion.     

Photoactivation of vascular iNOS and elevation of cGMP in vivo: possible mechanism for photovasorelaxation and inhibition of restenosis in an atherosclerotic rabbit models

Recently, intravascular low-power red laser light (LPRLL) therapy has been proposed for the prevention of postangioplasty restenosis due to the observed inhibition of experimental neointimal formation. The objective of this study was to determine the impact of endoluminal LPRLL on vascular levels of inducible nitric oxide synthase (iNOS) and cyclic guanosine monophosphate (cGMP) to help define the mechanism of this effect. Eight atherosclerotic male adult New Zealand White rabbits weighing 4-6 kg were used in these studies. The iliac arteries were treated in separate zones with: (1) balloon inflation only; (2) laser illumination only; and (3) balloon inflation + laser illumination. An uninjured zone of the iliac artery served as a control. Laser irradiation (630 nm) was delivered to the vessel wall via a Cold laser Illuminator (Cook, Inc., Bloomington, IN), with a 3 mm-diameter balloon. Experiments demonstrated that vascular cGMP levels obtained immediately following treatment in the balloon only group was the lowest (0.29 +/- 0.05 pmol/mg protein) and significantly lower compared with the uninjured controls (1.01 +/- 0.07 pmol/ mg protein) (P < 0.001). In the laser only treated group cGMP levels were significantly increased (2.87 +/- 0.12 pmol/mg protein) compared with the uninjured control (P < 0.001) and the balloon only group (P < 0.001). Vascular cGMP levels in the balloon + laser group (2.09 +/0.07 pmol/mg protein) was also increased compared to the balloon only (P < 0.001) and control (P < 0.001) groups. Qualitative analysis of Western blot demonstrated that laser illumination induces iNOS. In contrast balloon dilatation did not induce iNOS. Balloon + laser treatment, however, tended to restore the expression of iNOS. Our study demonstrated that intravascular low dose laser irradiation induces iNOS and elevates vascular cGMP in an in vivo atherosclerotic rabbit model.     

Rapid determination of sulfonated naphthalenes and their formaldehyde condensates in aqueous environmental samples using synchronous excitation fluorimetry.

Sulfonated naphthalenes and their formaldehyde condensates (SNFC) were determined in aqueous environmental samples by spectrofluorimetry. A clean-up step using n-hexane to extract possibly interfering nonpolar compounds such as naphthalene is the only preparatory procedure. Synchronous excitation mode with a gammalambda of 105 nm allows the determination of SNFC in environmental samples without additional clean-up or analyte enrichment. Interferences by humic acids and nitrate occurred only at concentrations higher than 1 mg C L(-1) and 10 mg NO3- L(-1), respectively. The limit of detection was 0.2 microg L(-1), the average recovery was 104% and the confidence interval (95% certainty) was 24%. The response factor for the quantitative determination of total SNFC, depending on the distribution of the different SNFC components, was validated for groundwater from two field sites using an HPLC-FD (fluorescence detection) method as a reference method.     

The influence of chitosans with defined degrees of acetylation on the thermodynamic data for copper coordination

The interaction of copper with three different chitosans having degrees of deacetylation of 77.5, 81.5, and 86.1%, named C, A, and F, respectively, was followed by the batch method at 298+/-1 K and the values obtained were fitted to a modified Langmuir equation. These interactions were also obtained by calorimetric titration. Experimentally, 50.0 mg of each chitosan was suspended in doubly distilled water at 298.15+/-0.02 K under mechanical turbine stirring. The titration was performed by adding increments of 10 microl of a 0.10 mol dm3 Cu(NO3)2 aqueous solution and the calorimetric isotherms obtained were adjusted to a modified Langmuir equation. From the net thermal effects K and DeltaH values were calculated, also permitting the acquisition of other thermodynamic data for the chitosan-copper interaction at the solid/liquid interface. The exothermic enthalpic values of -45.65+/-1.97, -49.91+/-1.57, and -48.64+/-0.82 kJ mol(-1), for chitosans C, A, and F, respectively, reflect the degree of deacetylation. The spontaneity of the systems is shown by the negative DeltaG values, -36.1+/-0.2, 36.8+/-0.1, and -38.1+/-0.3 kJ mol(-1) for the same sequence of chitosans. The negative entropic values, -34, -44, and -35 J mol(-1) K(-1), are in agreement with an ordering of solvent as the complexation occurred. The intensity of the thermal effects and the thermodynamic data obtained from the copper/chitosan interactions can be associated with the ability of these biopolymers to extract copper from aqueous solutions.     

Enantiomeric determination of L- and D-lactic acid in human cerebrospinal fluid by chiral ligand exchange high-performance liquid chromatography

Enantiomeric determination of L- and D-lactate in human cerebrospinal fluid (CSF) was achieved by HPLC on a chiral stationary phase with UV detection. Samples were submitted to a solid-phase extraction procedure using Oasis HLB Plus Extraction Cartridge and L- and D-lactate in the extract were separated by Shodex ORpac CRX-453 B column, a ligand exchange column for chiral separation, using a mobile phase containing copper (II) ion. L- and D-lactate were determined in 25 min. Intra-assay precision in CSF was 4.98% (mean 1.85 mmol/L) for L-lactate and 10.1% (mean 4.96 micromol/L) for D-lactate (n = 5). Detection limits were between 1.0 (L-lactate) and 1.5 (D-lactate) pmol. The mean values (n = 3) of analytical recovery for L- and D-lactate were 95% and 107%, respectively. The mean +/- SD of concentrations of L- and D-lactate in CSF (n = 20) were 1.52 +/- 0.54 mmol/L and 10.98 +/- 5.15 micromol/L, respectively.     

Some Thermodynamic Data on Copper-Chitin and Copper-Chitosan Biopolymer Interactions

Chitin and chitosan are good removers of cations from aqueous solution and wastewater. The interactive effect of cation with both biopolymers in aqueous medium was studied by the batch method at 298 +/- 1 K. The results were fitted to the modified Langmuir equation. The same adsorption was followed by calorimetric titration. In this process, 50.0 mg of each polymer was suspended in 19.0 cm3 of bidistilled water at 298.15 +/- 0.02 K, maintained under mechanical turbine stirring. The titration was performed by adding increments of 10 μL of 0.10 mol dm-3 Cu(NO3)2 aqueous solution to the system. The resulting isotherm was also adjusted to a modified Langmuir equation. From the thermal effects K and DeltaH values were determined, enabling the calculation of DeltaG and DeltaS for the interaction of copper cations with chitin and chitosan, giving the enthalpic values of -19.85 +/- 0.34 and -41.27 +/- 1.57 kJ mol-1, respectively. The spontaneity of this interaction is shown from DeltaG values of -35.9 +/- 0.1 and -36.8 +/- 0.1 kJ mol-1, which are followed by DeltaS values of +54 and of -15 J mol-1 K-1, respectively. The complexation is probably associated with the lack of order of the chitin polymeric chain or with the freedom of water molecules initially bonded to cations. The copper ion is coordinated to the pendant groups of the polymeric chain to form stable complexes. Copyright 1999 Academic Press.     

Metallonitrosyl fragment as electron acceptor: intramolecular charge transfer, long range electronic coupling, and electrophilic reactivity in the trans-[NCRu(py)(4)(CN)Ru(py)(4)NO](3+) ion

The new complex trans-[NCRu(py)(4)(CN)Ru(py)(4)NO](PF(6))(3) (I) was synthesized. In acetonitrile solution, I shows an intense visible band (555 nm, epsilon = 5800 M(-1) cm(-1)) and other absorptions below 350 nm, associated with d(pi) --> pi(py) and pi(py) --> pi(py) transitions. The visible band is presently assigned as a donor-acceptor charge transfer (DACT) transition from the remote Ru(II) to the delocalized [Ru(II)-NO(+)] moiety. Photoinduced release of NO is observed upon irradiation at the DACT band. Application of the Hush model reveals strong electronic coupling, with H(DA) = approximately 2000 cm(-1). The difference between the optical absorption energy and redox potentials for the donor and acceptor sites (Ru(III,II), 1.40 V, and NO(+)/NO, 0.50 V, vs Ag/AgCl, 3 M KCl, respectively) (hnu - DeltaE(red)) is 1.33 eV, a large value which probably relates to the significant changes in distances and angles for the Ru-N-O moiety upon reduction. UV-vis absorptions, IR frequencies, and redox potentials are solvent-dependent. Controlled potential reduction (of NO(+)) and oxidation (of Ru(II) associated with the dicyano-chromophore) of I afford stable species, [NCRu(II)(py)(4)(CN)Ru(py)(4)NO](2+) (I(red)) and [NCRu(III)(py)(4)(CN)Ru(py)(4)NO](4+) (I(ox)), respectively, which are characterized by UV-vis and IR spectroscopies. I(red) shows an EPR spectrum characteristic of [Ru(II)-NO(*)] complexes. Compound I is electrophilically reactive in aqueous solution above pH 5: values of the equilibrium constant for the reaction [NCRu(py)(4)(CN)Ru(py)(4)NO](3+)+ 2 OH(-) <--> [NCRu(py)(4)(CN)Ru(py)(4)NO(2)](+) + H(2)O, K = 3.2 +/- 1.4 x 10(15) M(-2), and of the rate constant for the nucleophilic addition of OH(-), k = 9.2 +/- 0.2 x 10(3) M(-1) s(-1)(25 degrees C, I = 1 M), are obtained, with DeltaH = 90.7 +/- 3.8 kJ mol(-1) and DeltaS = 135 +/- 13 J K(-1) mol(-1). The oxidized complex, I(ox), shows an enhanced electrophilic reactivity toward OH(-). This addition reaction is followed by irreversible processes, which most probably lead to disproportionation of bound nitrite and other products.     

Spin-forbidden deprotonation of aqueous nitroxyl (HNO)

The first mechanistic study of a spin-forbidden proton-transfer reaction in aqueous solution is reported. Laser flash photolysis of alkaline trioxodinitrate (N(2)O(3)(2)(-), Angeli's anion) is used to generate a nitroxyl anion in its excited singlet state ((1)NO(-)). Through rapid partitioning between protonation by water and electronic relaxation, (1)NO(-) produces (1)HNO (ground state, yield 96%) and (3)NO(-) (ground state, yield 4%), which comprise a unique conjugate acid-base couple with different ground-state multiplicities. Using the large difference between reactivities of (1)HNO and (3)NO(-) in the peroxynitrite-forming reaction with (3)O(2), the kinetics of spin-forbidden deprotonation reaction (1)HNO + OH(-) --> (3)NO(-) + H(2)O is investigated in H(2)O and D(2)O. Consistent with proton transfer, this reaction exhibits primary kinetic hydrogen isotope effect k(H)/k(D) = 3.1 at 298 K, which is found to be temperature-dependent. Arrhenius pre-exponential factors and activation energies of the second-order rate constant are found to be: log(A, M(-)(1) s(-)(1)) = 10.0 +/- 0.2 and E(a) = 30.0 +/- 1.1 kJ/mol for proton transfer and log(A, M(-)(1) s(-)(1)) = 10.4 +/- 0.1 and E(a) = 35.1 +/- 0.7 kJ/mol for deuteron transfer. Collectively, these data are interpreted to show that the nuclear reorganization requirements arising from the spin prohibition necessitate significant activation before spin change can take place, but the spin change itself must occur extremely rapidly. It is concluded that a synergy between the spin prohibition and the reaction energetics creates an intersystem barrier and is responsible for slowness of the spin-forbidden deprotonation of (1)HNO by OH(-); the spin prohibition alone plays a minor role.     

High-performance thin-layer chromatography method for quantitative determination of oenothein B and quercetin glucuronide in aqueous extract of Epilobii angustifolii herba

A method was developed for separation and quantitative determination of oenothein B (OeB) and quercetin glucuronide (QG) in aqueous extract of Epilobii angustifolii herba by HPTLC-densitometry. The analyses were performed on HPTLC RP-18 WF(254) plates with 25% MeCN in water (+50mM H(3)PO(4)) as the mobile phase (distance of 8 cm) for OeB quantification and then with acetonitrile (distance of 4 cm) for QG quantification. OeB and QG were determined by densitometry at 270 and 350 nm, respectively. Their amounts were calculated using the regression equations of the calibration curves which were linear in a range of 1.14-2.28 microg spot(-1) for OeB and of 0.0768-0.6912 microg spot(-1) for QG. The amounts of OeB and QG in aqueous extract of Epilobii angustifolii herba measured by the method developed were 152.46+/-4.92 and 22.07+/-1.38 mg g(-1), respectively. The method was found to be relatively simple, specific, precise and accurate for the quality control of Epilobium angustifolium extracts.     

The stimulatory effect of IL-1beta on the insulin secretion of rat pancreatic islet is not related with iNOS pathway

Interleukin 1 (IL-1) is a pleiotropic cytokine with the potential to destroy pancreatic beta-cells, and thought to be involved in the pathogenesis of type I diabetes mellitus. Expression of inducible nitric oxide synthase (iNOS) and subsequent NO formation induced by IL-1beta may impair an islet function in rodents. Inhibition of iNOS may protect against cytokine-induced beta-cell suppression, although cytokines might also induce NO-independent impairment. To examine the role of NO in the IL-1beta treated cells, rat islets were treated with various concentrations (0, 0.5, 5, 50, 500 pmol/L) of IL-1beta with or without NG-monomethyl-L-arginine (NMMA; a competitive inhibitor of nitiric oxide synthase) for 2 or 6 h. Insulin secretion was stimulated in islets treated with 5, 50, and 500 pmol/ L of IL-1beta for 2 h and 0.5 pmol/L for 6 h, respectively. The stimulatory effect of IL-1beta on the insulin secretion of rat islets was not prevented by NMMA. Nitrate concentration was increased in a time- and concentration-dependent manner. Nitrate production was inhibited by NMMA. iNOS mRNA expression was increased at concentrations more than 5 pmol/L of IL-1beta in a dose dependent manner. iNOS mRNA was detectable after 2 h and peaked at 6 h but decreased after 24 h. These results suggested that the stimulatory effect of IL-1beta on the insulin secretion of rat islets is independent of iNOS-related NO production of IL-1beta and the enzyme activity of nitric oxide synthase.     

Study of complex formation in the manganese(II)/azide system

The complex formation between Mn(II) cations and N(3)(-) anions was studied in aqueous medium at 25 degrees C and ionic strength 2.0 M (NaClO(4)). Data of average ligand number, n (Bjerrum's function), were obtained from pH measurements on the Mn(II)/N(3)(-)/HN(3) system followed by integration to obtain Leden's function, F(0)(L). Graphical treatment of data and a matrix solution of simultaneous equations have given the following overall formation constants of mononuclear stepwise complexes: beta(1)=4.15+/-0.02 M(-1), beta(2)=6.61+/-0.04 M(-2), beta(3)=3.33+/-0.02 M(-3), beta(4)=0.63+/-0.01 M(-4). A linear plot of log K(n) vs. (n-1) shows no change in the configuration during complex formation. Slow spontaneous oxidation of solutions to Mn(III) occurs when the N(3)(-) concentration is greater than 1.0 M.