Dual‐Functional Small Molecules for Generating an Efficient Cytochrome P450BM3 Peroxygenase

We report a unique strategy for the development of a H₂O₂‐dependent cytochrome P450BM3 system, which catalyzes the monooxygenation of non‐native substrates with the assistance of dual‐functional small molecules (DFSMs), such as N‐(ω‐imidazolyl fatty acyl)‐l ‐amino acids. The acyl amino acid group of DFSM is responsible for bounding to enzyme as an anchoring group, while the imidazolyl group plays the role of general acid–base catalyst in the activation of H₂O₂. This system affords the best peroxygenase activity for the epoxidation of styrene, sulfoxidation of thioanisole, and hydroxylation of ethylbenzene among those P450–H₂O₂ system previously reported. This work provides the first example of the activation of the normally H₂O₂‐inert P450s through the introduction of an exogenous small molecule. This approach improves the potential use of P450s in organic synthesis as it avoids the expensive consumption of the reduced nicotinamide cofactor NAD(P)H and its dependent electron transport system. This introduces a promising approach for exploiting enzyme activity and function based on direct chemical intervention in the catalytic process.     

Antioxidant phenolic compounds from the rhizomes of Astilbe rivularis

The rhizomes of Astilbe rivularis, commonly known as ‘Thulo Okhati’ are widely used in Nepal as tonic for uterine and menstrual disorders. In our preliminary study, the 70% MeOH extract of the rhizomes showed potent antioxidant activity. Hence, present study was aimed for the isolation of potent antioxidant constituents. Bergenin (1), 11-O-galloylbergenin (2), (+)-catechin (3), (?)-catechin (4), (?)-afzelechin (5), (?)-epiafzelechin (6) and 2-(β-D-glucopyranosyloxy)-4-hydroxylbenzenacetonitrile (7) were isolated from the rhizomes. Structures of these compounds were elucidated on the basis of spectroscopic methods. All these isolated compounds were evaluated for their in vitro antioxidant activity by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. 11-O-Galloylbergenin (2), (+)-catechin (3), (?)-catechin (4), (?)-afzelechin (5) and (?)-epiafzelechin (6) showed potent antioxidant activity.     

Organocatalytic ring-opening polymerization of l-lactide in supercritical carbon dioxide under plasticizing conditions

The synthesis of poly-l-lactide (PLLA) in supercritical carbon dioxide (scCO₂) was accomplished using an organocatalyst. The reaction proceeded smoothly under CO₂ plasticizing polymerization (CPP) conditions at a lower temperature than those conventionally employed. This method allowed the formation of high-molecular-weight, pure PLLA, and therefore has the potential to reduce energy consumption and minimize production costs. Our method is non-toxic and efficient, affording a high-quality product while complying with volatile organic compound regulations. We can produce PLLA that meets the increasing standards (safety and high functionality) of the medical sector, while being applicable to full-scale industrial manufacturing and academic research.     

Zug-Druckversuche an Messingkristallen (Bauschingereffekt)

Zeitschrift für Physik A Hadrons and nuclei - Unsymmetrie der Verfestigung durch bleibende Verformungen (Bauschingereffekt) und Beseitigung der Unsymmetrie durch Anlassen. — Herstellung...     

Occurrence of L-2,4-diaminobutyrate decarboxylase activity in Acinetobacter.

Three strains of the genus Acinetobacter grown in a polyamine-free synthetic medium contained very high amounts of 1,3-diaminopropane, and there were also high concentrations in the extracellular growth medium. Little, if any, of the usual polyamines, putrescine, spermidine and spermine were found. There was no detectable activity of aminopropyltransferase (greater than 0.2 nmol spermidine formed/mg protein/h), which would be responsible for the formation of spermidine or spermine, expected precursors of 1,3-diaminopropane. These observations suggested the possibility of another mode of 1,3-diaminopropane biogenesis. Decarboxylation activity towards L-2,4-diaminobutyrate leading to the formation of 1,3-diaminopropane was detected in extracts of all three strains examined. The decarboxylase was partially purified from A. calcoaceticus ATCC 23055. The enzyme was active against only L-2,4-diaminobutyrate among the diamino acids tested and required pyridoxal phosphate as a cofactor. Mg2+ activated the enzyme.     

The new method for the determination of cobalt in sea water by solvent extraction with 2-nitroso-5-diethylaminophenol

Cobalt in sea waters can be determined spectrophotometrically by means of 2-nitroso-5-diethylaminophenol after extraction of the complex into 1,2-dichloro-ethane. No preliminary concentration is needed. Interferences are prevented by masking or by stripping from the organic phase. The method is applicable over the range 0–0.24 μg Co 1^-1 when 1–1 or 2–1 samples are taken. The relative standard deviation is 4% for 0.15 μg Co 1^-1. The stability of cobalt in sea water samples is discussed.     

Extraction—spectrophotometric determination of boric acid with 1,8-dihydroxynaphthalene-4-sulfonic acid and zephiramine

l,8-Dihydroxynaphthalene-4-sulfonic acid (DHNS) is described as a new reagent for the extraction—spectrophotometric determination of boric acid. The reagent and its boron complex are extracted into 1,2-dichloroethane as ion-associates with tetradecyldimethyl-benzylammonium chloride (zephiramine). The extracted complex of boron—DHNS—zephiramine has the composition 1:2:3 and is stable to back-washing with 1 M sodium chloride solution (pH 9.2), whereas the excess of reagent co-extracted is removed to the aqueous phase. The apparent molar absorptivity of the complex in the organic phase is 2.45 × 10⁴ l mol^-1 cm^-1 at 341 nm, which is 1.7 times larger than that with chromotropic acid. Addition of EDTA prevents most interferences. The improved method with DHNS is successfully applied to the determination of boron as boric acid in waters. The exchange equilibrium constants,

, for the reagent and complex were also determined for four monovalent anions (X^- = Cl^-, Br^-, NO₃^-and I^-). Some of these constants are compared with those pertaining to chromotropic acid and 1,8-dihydroxynaphthalene.