STABILITY OF STRONTIUM(II) AND BARIOM(II) COMPLEXES WITH 18-CROWN-6 IN AQUEOUS SOLUTION AND THEIR EXTRACTABILITY AS PICRATES

When strontium(II) and barium(II) were extracted with 18-crown-6(l 8C6) and picrate ions into chloroform, log(distribution ratio of metal(II)) approached flat in a higher region of log[18C6], although it is reported that the distribution ratio of copper(II) or zinc(II) increases in proportion to the second order of 118C6]. From the extraction data analysis, the flat distribution ratio was explained by the formation of the aqueous complex with 18C6 and the stability constants for strontium(II) and barium(II) were determined to be 2.89 and 3.68 as logβ1respectively.     

SYNERGISTIC EXTRACTION OF EUROPIUM(III) WITH BENZOIC ACID AND THENOYLTRIFLUOROACETONE

ABSTRACT

The solvent extraction of europium(III) into solutions of thenoyltrifluoroacetone and benzoic acid in cyclohexane, carbon tetrachloride, benzene, chloroform, pentachloroethane, and tetrachloroethane has been measured at 25°C. It has been found that the extracted species involve two types of adducts, EuA₃· HB and EuA₃· 2HB where A denotes the TTA anion and HB the benzoic acid monomer. The magnitude of the adduct formation constants in different solvents has been correlated with the dimerization constants of benzoic acid in the solvents.     

EXTRACTION OF PALLADIUM(II) AND PLATINUM(IV) AS CHLOROCOMPLEX ACIDS INTO BASIC ORGANIC SOLVENTS

Solvent extraction of platinum(IV) and palladium(II) with tri-n-octylamine(TOA) in o-xylene from 4.0M (Na,H)(Cl, HSO₄) has been investigated at 298K in order to compare with similar extraction by trioctylphosphine oxide(TOPO). The dependence of the distribution ratio of platinum(IV) and pal 1adium(II) on TOA, hydrogen ion and chloride ion concentrations suggests the dominant extracted species of these metals would be 2:1 for proto-nated amine : chlorocomplex anion and the extraction should be essentially anion exchange reaction. The extraction constants (Kex = D[H⁺(T0A)C1 ] ²[C1 ]²), were evaluated as 10^6-3 and 10^5.8 for platinum(IV) and pal ladium(II), respectively. The anion exchange with protonated TOPO salt represented by H(T0P0)₂ ⁺C1  is less than that with protonated TOA salt by a factor of one order.     

Addition of Aliskiren to Angiotensin Receptor Blocker Improves Ambulatory Blood Pressure Profile and Cardiorenal Function Better than Addition of Benazepril in Chronic Kidney Disease

An altered ambulatory blood pressure (BP) and heart rate (HR) profile is related to chronic kidney disease (CKD) and cardiorenal syndrome. In this study, we examined the effects of aliskiren, when added to angiotensin II type 1 receptor blockers, on ambulatory BP and cardiorenal function in CKD. Thirty-six hypertensive CKD patients were randomly assigned to the aliskiren add-on group (n = 18) or the benazepril add-on group (n = 18). Ambulatory BP and cardiorenal function parameters were measured at baseline and 24 weeks after treatment. Compared with the benazepril group, nighttime systolic BP variability in the aliskiren group was lower after treatment. Albuminuria was decreased in the aliskiren group, but not in the benazepril group. In addition, left ventricular mass index (LVMI) was significantly lower in the aliskiren group than in the benazepril group after treatment. In the aliskiren group, multivariate linear regression analysis showed an association between changes in albuminuria and changes in nighttime systolic BP. Furthermore, there were associations between changes in LVMI and changes in daytime HR variability, as well as between changes in LVMI and changes in plasma aldosterone concentration. These results suggest that aliskiren add-on therapy may be beneficial for suppression of renal deterioration and pathological cardiac remodeling through an improvement that is effected in ambulatory BP and HR profiles.     

{beta}-sheet folding of fragment (16-36) of bovine pancreatic trypsin inhibitor as predicted by Monte Carlo simulated annealing

A tertiary structure prediction is described using Monte Carlosimulated annealing for the peptide fragment corresponding toresidues 16–36 of bovine pancreatic trypsin inhibitor(BPTI). The simulation starts with randomly chosen initial conformationsand is performed without imposing experimental constraints usingenergy functions given for generic interatomic interactions.Out of 20 simulation trials, seven conformations show a sheet-likestructure—two strands connected by a turn—althoughthis sheet-like structure is not as rigid as that observed innative BPTI. It is also shown that these conformations are mostlylooped and exhibit a native- like right-handed twist. Unlikethe case with the C-peptide of RNase A, no conspicuous -helicalstructure is found in any of the final conformations obtainedin the simulation. However, the lowest-energy conformation doesnot resemble exactly the native structure. This indicates thatthe rigid ß-sheet conformation of native BPTI merelycorresponds to a local minimum of the energy function if thefragment with residues 16–36 is isolated from the nativeprotein. A statistical analysis of all 20 final conformationssuggests that the tendency for the peptide segments to formextended ß-strands is strong for those with residues18–24, and moderate for those with residues 30–35.The segment of residues 25–29 does not tend to form anydefinite structure. In native BPTI, the former segments areinvolved in the ß-sheet and the latter in the turn.A folding scenario is also speculated from this analysis.     

Esterification of n‐butyric acid with n‐butyl alcohol and transesterification of (R, S)‐phenylethanol by lipase immobilized on cellulose acetate–TiO2 gel fibre

Lipase (EC 3.1.1.3) was immobilized on cellulose acetate–TiO₂ gel fibre by the sol–gel method. The immobilized lipases were used for esterification of n‐butyric acid with n‐butyl alcohol and enantioselective acylation of (R, S)‐phenylethanol using vinyl acetate as an acyl donor. Compared with native lipase, the activity of the immobilized lipase was stable and relatively unaffected by the water content of the solvent and the substrate concentration. The data indicate that the lipases are immobilized on the fibre surface and that enzyme activity is influenced by bound water. However, the thermal reactivity and enantioselectivity of the immobilized lipase were less than those of native lipase. This may not reflect thermal inactivation of the enzyme but rather significant thermal contraction of the gel fibre by cellulose crystallization, resulting in liberation of bound water and a decrease in the amount of enzyme which is available for the reaction. Copyright © 2001 Society of Chemical Industry     

Thermal stabilization of penicillolysin, a thermolabile 19 kDa Zn2+-protease, obtained by site-directed mutagenesis

Penicillolysin is a member of the clan MX and the family of M35 proteases. The enzyme is a thermolabile Zn(2+)- protease from Penicillium citrinum with a unique substrate profile. We expressed recombinant penicillolysin in Aspergillus oryzae and generated several site-directed mutants, R33E/E60R, A167E and T81P, with the intention of exploring thermal stabilization of this protein. We based our choice of mutations on the structures of homologous thermally stable enzymes, deuterolysin (EC 3.4.24.39) from A.oryzae and a peptidyl-Lys metallopeptidase (GfMEP) from the edible mushroom Grifora frondsa. The resulting mutant proteins exhibited comparable catalytic efficiency to the wild-type enzyme and some showed a higher tolerance to temperature.     

Promotion effect of bifunctional five‐membered cyclic dithiocarbonate on curing of one‐component epoxy resin by imines as latent initiator

This article deals with curing of a one‐component epoxy resin containing a bifunctional five‐membered cyclic dithiocarbonate 1 with an imine 2 as a latent initiator. When 1 was added to a mixture of epoxy resin and 2 , the curing rate and initial adhesive strength increased higher than that without 1 . It was supposed that the reaction of 1 and an amine released from 2 was much faster than the amine–epoxide reaction, and a thiol group formed by the reaction of 1 with the amine accelerated the amine–epoxide reaction. The adhesive strength of the one‐component epoxy resin containing 10 mol % of 1 exhibited the highest value. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 961–964, 2004     

Synthesis of Liquid Crystalline Organometallic Poly(arylene)s Containing 1,3-Type (η4-Cyclobutadiene)cobalt Moieties in the Main Chain

Novel organometallic poly(arylene)s containing 1,3-type (cyclobutadiene)cobalt moieties in the main chain were prepared by the Ni(0)-mediated dehalogenative polycondensation of monomers having (cyclobutadiene)cobalt moieties. The resulting poly(arylene)s were partly soluble in organic solvents and the number-average molecular weights (M _n) of soluble fractions were estimated to be 16,700–22,000 by GPC. The polymers showed the formation of a -conjugated structure, good solubility in common organic solvents, and thermotropic liquid crystallinity.