In vitro study of the interaction of cysteine with a thiazide diuretic (hydrochlorothiazide) at different ph by voltammetric and spectroscopic techniques

The interaction of cysteine (RSH) with a thiazide diuretic, hydrochlorothiazide (HCTZ) was characterized by UV-Vis absorption spectroscopy and square-wave voltammetry in Britton-Robinson (B-R) buffer solution (with pH 5, 7 and 9). On the square-wave voltamogram of cysteine, the reduction peak current of mercurous cysteine thiolate (Hg₂(RS)₂) decreased and its peak potential shifted to more positive values with the addition of HCTZ. This results showed that the RSH interacted with HCTZ. The stoichiometry of HCTZ-RSH molecular complex was determined by voltammetric data with the result of 1: 1. By using linear regression analysis of the voltammetric data at pH 5, 7 and 9, the apparent formation constants of HCTZ-RSH complex were calculated to be 9.54 × 10³, 2.80 × 10⁴ and 2.55 × 10⁴ M^?1, respectively. At the same time, this interaction was also supported by UV-Vis spectroscopic measurements. According to the voltammetric and spectroscopic results, it was suggested that the interaction mode between RSH and HCTZ molecules might be a combination of hydrophobic interactions and hydrogen bonds.     

Reversible high‐temperature phase transition of a manganese(II) formate framework with imidazolium cations

A new metal–formate framework, poly[1H‐imidazol‐3‐ium [tri‐μ₂‐formato‐manganese(II)]], {(C₃H₅N₂)[Mn(HCOO)₃]}_n, was synthesized and its structural phase transition was studied by thermal analysis and variable‐temperature X‐ray diffraction analysis. The transition temperature is around 435 K. The high‐temperature phase is tetragonal and the low‐temperature phase is monoclinic, with a β angle close to 90°. The relationship of the unit cells between the two phases can be described as: a_HT = 0.5a_LT + 0.5b_LT; b_HT = −0.5a_LT + 0.5b_LT; c_HT = 0.5c_LT. In the high‐temperature phase, both the framework and the guest 1H‐imidazol‐3‐ium (HIm) cations are disordered; the HIm cations are located about 2mm sites and were modelled as fourfold disordered. The Mn and a formate C atom are located on fourfold rotary inversion axes, while another formate C atom is on a mirror plane. The low‐temperature structure is ordered and consists of two crystallographically independent HIm cations and two crystallographically independent Mn²⁺ ions. The phase transition is attributable to the order–disorder transition of the HIm cations.     

Preparation,Crystal Structure,and Thermal Decomposition of the Intriguing Five‐coordinated Compound [Cu(IMI)4Cl]Cl (IMI = Imidazole)

The intriguing multi‐ligand compound [Cu(IMI)₄Cl]Cl ( 1 ) with the ligand imidazole (IMI) was synthesized and characterized by elemental analysis and FT‐IR spectroscopy. The crystal structure was determined by X‐ray single crystal diffraction and the crystallographic data showed that the compound belongs to the monoclinic P2₁/n space group [α = 8.847(2) Å, b = 13.210(3) Å, c = 13.870(3) Å, and β = 90.164(3)°]. Furthermore, the Cu^II ion is five‐coordinated by four nitrogen atoms from four imidazole ligands and a chlorine atom. The thermal decomposition mechanism was determined based on differential scanning calorimetry (DSC) and thermogravimetric (TG‐DTG) analysis. The non‐isothermal kinetics parameters were calculated by the Kissinger's method and Ozawa's method, respectively. The energy of combustion, enthalpy of formation, critical temperature of thermal explosion, entropy of activation (ΔS^≠), enthalpy of activation (ΔH^≠), and free energy of activation (ΔG^≠) were measured and calculated.     

有机溶剂/缓冲液两相体系中全细胞催化拆分环氧氯丙烷

研究了有机溶剂/缓冲液两相体系中重组大肠杆菌E.coli BL21 (DE3)全细胞水解动力学拆分外消旋环氧氯丙烷制备(R)-环氧氯丙烷的过程.结果表明,最适反应条件为:最适有机溶剂异辛烷与缓冲液的体积比7:3,最适缓冲液pH 8.0,底物浓度574mmol/L,全细胞加入量0.07g湿菌体/ml溶液,温度30℃.在此条件下于1L反应器中反应45min,(R)-环氧氯丙烷的摩尔产率、光学纯度和时空产率分别达到37.5%,99.3%ee和0.286mol/(L·h).与单一水相体系相比,异辛烷/缓冲液两相体系中底物浓度和(R)-环氧氯丙烷时空产率分别提高了55.2%和98.6%.     

Temperature-sensitive membranes prepared from blends of poly(vinylidene fluoride) and poly(N-isopropylacrylamides) microgels

In this study, temperature-sensitive membranes were prepared by phase transition of the mixture of the temperature-sensitive poly(N-isopropylacrylamides) (PNIPAAM) microgels and poly(vinylidene fluoride). The results of Fourier transformed infrared spectrometer, X-ray photoelectron spectroscopy, elemental analysis, and scanning electron microscope photographs indicate that the PNIPAAM microgels are distributed more in the inner membrane than on the surface. The scanning electron microscope photographs reveal the blend membranes having porous surfaces with nanometer sizes and porous cross-sections with micrometer sizes. The addition of the PNIPAAM microgels is found to improve the porosity, the pore size, water flux, as well as to enhance the hydrophilicity and anti-fouling property of the blend membranes. The blend membrane shows temperature-sensitive permeability and protein rejection with the most dramatic change at around 32 °C which is the lower critical solution temperature of PNIPAAM, when water or bovine serum albumin solution flow through. Specifically, below 32 °C, the blend membrane shows a high protein rejection ratio which decreases with increasing temperature and a low water flux which increases with increasing temperature; above 32 °C, the blend membrane shows a low protein rejection ratio which decreases with increasing temperature and a high water flux which increases with increasing temperature.     

Total synthesis of Daphnodorin A

A total synthesis of Daphnodorin A, a member of the Daphnodorins, was accomplished. Key features of the synthetic strategy include construction of 2-substituted-3-functionalized benzofuran via intramolecular Heck reaction and a mild Barton–McCombie deoxygenation process mediated by triethylborane. The total synthesis provided Daphnodorin A in 19.7% or 5.6% overall yield over 7 or 15 steps.     

Specific ion effects on the electrophoretic mobility of small,highly charged peptides: A modeling study

In this work, we use coarse‐grained modeling to study the free solution electrophoretic mobility of small highly charged peptides (lysine, arginine, and short oligos thereof (up to nonapeptides)) in NaCl and Na₂SO₄ aqueous solutions at neutral pH and room temperature. The experimental data are taken from the literature. A bead modeling methodology that treats the electrostatics at the level of the nonlinear Poisson Boltzmann equation developed previously in our laboratory is able to account for the mobility of all peptides in NaCl, but not Na₂SO₄. The peptide mobilities in Na₂SO₄ can be accounted for by including sulfate binding in the model and this is proposed as one possible explanation for the discrepancy. Oligo arginine peptides bind more sulfate than oligo lysines and sulfate binding increases with the oligo length.     

Ultra‐fast LC–ESI‐MS/MS method for the simultaneous determination of six highly toxic Aconitum alkaloids from Aconiti kusnezoffii radix in rat plasma and its application to a pharmacokinetic study

A fast, sensitive, and efficient ultra‐fast LC–ESI‐MS/MS method was developed for the simultaneous quantitation of six highly toxic Aconitum alkaloids, that is, aconitine, mesaconitine, hypaconitine, benzoylaconine, benzoylmesaconine, and benzoylhypaconine, in rat plasma after oral administration of crude ethanol extracts from Aconiti kusnezoffii radix by ultrasonic extraction, reflux extraction for 1 h, and reflux extraction for 3 h, respectively. The separation of six Aconitum alkaloids and aminopyrine (internal standard) was performed on an InertSustain® C₁₈ column, and the quantification of the analytes was performed on a 4000Q ultra‐fast LC–MS/MS system with turbo ion spray source in the positive ion and multiple‐reaction monitoring mode. Absolute recoveries ranged within 65.06–85.1% for plasma samples. The intra‐ and interday precision and accuracy of analytes were satisfactory. The methods were validated with sensitivity reaching the lower LOQ for aconitine, mesaconitine, hypaconitine, benzoylaconine, benzoylmesaconine, and benzoylhypaconine, which were 0.025, 0.025, 0.050, 0.025, 0.025, and 0.100 ng/mL, respectively. The method was successfully applied to a pharmacokinetic study of six Aconitum alkaloids in rat plasma after oral administration of crude ethanol extracts from the raw root of Aconitum kusnezoffii Reichb. by three different extraction processes.     

Determination of 12 potential nephrotoxicity biomarkers in rat serum and urine by liquid chromatography with mass spectrometry and its application to renal failure induced by Semen Strychni

In previous nephrotoxicity metabonomic studies, several potential biomarkers were found and evaluated. To investigate the relationship between the nephrotoxicity biomarkers and the therapeutic role of Radix Glycyrrhizae extract on Semen Strychni‐induced renal failure, 12 typical biomarkers are selected and a simple LC–MS method has been developed and validated. Citric acid, guanidinosuccinic acid, taurine, guanidinoacetic acid, uric acid, creatinine, hippuric acid, xanthurenic acid, kynurenic acid, 3‐indoxyl sulfate, indole‐3‐acetic acid, and phenaceturic acid were separated by a Phenomenex Luna C₁₈ column and a methanol/water (5 mM ammonium acetate) gradient program with a runtime of 20 min. The prepared calibration curves showed good linearity with regression coefficients all above 0.9913. The absolute recoveries of analytes from serum and urine were all more than 70.4%. With the developed method, analytes were successfully determined in serum and urine samples within 52 days. Results showed that guanidinosuccinic acid, guanidinoacetic acid, 3‐indoxyl sulfate, and indole‐3‐acetic acid (only in urine) were more sensitive than the conventional renal function markers in evaluating the therapeutic role of Radix Glycyrrhizae extract on Semen Strychni‐induced renal failure. The method could be further used in predicting and monitoring renal failure cause by other reasons in the following researches.