Microbial hydroxylation of pregnenolone derivatives

Pregnenolone and pregnenolone acetate were incubated with the fungi Cunninghamella elegans, Rhizopus stolonifer and Gibberella fujikuroi. Incubation of with C. elegans yielded metabolites, 3beta,7beta,11alpha-trihydroxypreg-5-en-20-one, 3beta,6alpha,11alpha,12beta,15beta-pentahydroxypreg-4-en-20-one and 3beta,6beta,11alpha-trihydroxypreg-4-en-20-one, while incubation with G. fujikuroi yielded two known metabolites, 3beta,7beta-dihydroxypregn-5-en-20-one and 6beta,15beta-dihydroxypreg-4-ene-3,20-dione. Metabolites and were found to be new. Fermentation of by C. elegans yielded four known oxidative metabolites, androsta-1,4-diene-3,17-dione, 6beta,15beta-dihydroxyandrost-4-ene-3,17-dione and 11alpha,15beta-dihydroxypreg-4-ene-3,20-dione. Fermentation of with R. stolonifer yielded two known metabolites, 11alpha-hydroxypreg-4-ene-3,20-dione and. Compounds were screened for their cholinesterase inhibitory activity in a mechanism-based assay.     

Cholinesterase‐Inhibiting New Steroidal Alkaloids from Sarcococca hookeriana of Nepalese Origin

Bioassay‐guided phytochemical investigation of Sarcococca hookeriana has resulted in the isolation and structure elucidation of five new pregnane‐type steroidal alkaloids: (?)‐hookerianamide A (=(2β,3β,4β,20S)‐20‐(dimethylamino)‐3‐[(3‐methylbut‐2‐enoyl)amino]‐5α‐pregn‐16‐ene‐2,4‐diol; 1 ), (+)‐hookerianamide B (=(2α,3β,4β,20S)‐4‐acetoxy‐20‐(dimethylamino)‐3‐[(3‐methylbut‐2‐enoyl)amino]‐5α‐pregnan‐2‐ol; 2 ), (?)‐hookerianamide C (=(2β,3β,20S)‐2‐acetoxy‐20‐(dimethylamino)‐3‐[(3‐methylbut‐2‐enoyl)amino]‐5α‐pregnane; 3 ), (?)‐hookerianamine A (=(3β,20S)‐20‐(dimethylamino)‐3‐(methylamino)‐5α‐pregn‐14‐ene; 4 ), and (+)‐phulchowkiamide A (=(3β,20S)‐20‐(methylamino)‐3‐[(2‐methylbut‐2‐enoyl)amino]‐5α‐pregn‐2‐en‐4‐one; 5 ). These compounds, as well as the two chemically derived acetyl derivatives 6 and 7 , displayed cholinesterase inhibition in a concentration‐dependent manner.     

Phosphine-Triggered Structural Defects in Au44 Homologues Boost Electrocatalytic CO2 Reduction

The systematic induction of structural defects at the atomic level is crucial to metal nanocluster research because it endows cluster-based catalysts with highly reactive centers and allows for a comprehensive investigation of viable reaction pathways. Herein, by substituting neutral phosphine ligands for surface anionic thiolate ligands, we establish that one or two Au₃ triangular units can be successfully introduced into the double-stranded helical kernel of Au₄₄(TBBT)₂₈, where TBBT=4-tert-butylbenzenethiolate, resulting in the formation of two atomically precise defective Au₄₄ nanoclusters. Along with the regular face-centered-cubic (fcc) nanocluster, the first series of mixed-ligand cluster homologues is identified, with a unified formula of Au₄₄(PPh₃)_n(TBBT)_28−2n (n=0–2). The Au₄₄(PPh₃)(TBBT)₂₆ nanocluster having major structural defects at the bottom of the fcc lattice demonstrates superior electrocatalytic performance in the CO₂ reduction to CO. Density functional theory calculations indicate that the active site near the defects significantly lowers the free energy for the *COOH formation, the rate-determining step in the whole catalytic process.     

Biotransformation of <Emphasis Type="SmallCaps">l</Emphasis>-tyrosine to Dopamine by a Calcium Alginate Immobilized Mutant Strain of <Emphasis Type="Italic">Aspergillus oryzae</Emphasis>

The present research work is concerned with the biotransformation of l-tyrosine to dopamine (DA) by calcium alginate entrapped conidiospores of a mutant strain of Aspergillus oryzae. Different strains of A. oryzae were isolated from soil. Out of 13 isolated strains, isolate-2 (I-2) was found to be a better DA producer. The wild-type I-2 was chemically improved by treating it with different concentrations of ethyl methyl sulfonate (EMS). Among seven mutant variants, EMS-6 exhibiting maximal DA activity of 43 μg/ml was selected. The strain was further exposed with l-cysteine HCl to make it resistant against diversion and environmental stress. The conidiospores of selected mutant variant A. oryzae EMS-6 strain were entrapped in calcium alginate beads. Different parameters for immobilization were investigated. The activity was further improved from 44 to 62 μg/ml under optimized conditions (1.5 % sodium alginate, 2 ml inoculum, and 2 mm bead size). The best resistant mutant variable exhibited over threefold increase in DA activity (62 μg/ml) than did wild-type I-2 (21 μg/ml) in the reaction mixture. From the results presented in the study, it was observed that high titers of DA activity in vitro could effectively be achieved by the EMS-induced mutagenesis of filamentous fungus culture used.     

Effects of the Stepped-Doped Lower Waveguide and a Doped p-Cladding Layer on AlGaN-Based Deep-Ultraviolet Laser Diodes

Journal of Russian Laser Research - The performance of deep ultraviolet (DUV) laser diodes (LDs) may be affected by structural variations in the composition of AlGaN devices. In this work, we...     

3D Ellipsoidal Model for Mobile-to-Mobile Radio Propagation Environments

Geometrical models are mostly used for the study and analysis of the characteristics of radio communication channels. In this paper, a three-dimensional semi-ellipsoidal scattering model is proposed for mobile-to-mobile communication channels, where uniformly distributed scatterers are assumed to be confined within the semi-ellipsoids around mobile stations. The semi-ellipsoidal shape with adjustable dimensions is considered to model the scattering phenomenon in urban streets and canyons. Using the proposed scattering model, a closed-form expression for the joint probability density function of the Angle-of-Arrival in azimuth and elevation planes of the incoming multipath signals is derived at each mobile station. Moreover, various observations are made, which show the impact of scatterers’ elevation and streets’ orientation on the spatial characteristics of mobile-to-mobile communication channel.     

Measurements of the oscillator strengths for the 6p7s (1/2,1/2)1 → 6pnp (1/2,3/2)2 Rydberg transitions of lead

We report experimentally determined oscillator strength distribution in the bound region of lead corresponding to the 6p7s (1/2, 1/2)₁ → 6pnp (1/2, 3/2)₂ (20 ≤ n ≤ 52) Rydberg transitions. The absolute value of the photoionization cross section from the 6p7s (1/2, 1/2)₁ excited state at the first ionization threshold 6p (²P_1/2) has been determined as 27 ± 4 Mb using the saturation absorption technique. The threshold value of the photoionization cross section is used to calibrate the oscillator strengths of the above mentioned Rydberg transitions. Moreover, oscillator strengths in the bound region smoothly connect with the differential oscillator strength density at the first ionization threshold, and verify the fundamental condition of quantum defect theory.     

Solvent-free synthesis and antibacterial studies of some quinolinones

Abstract  

Solvent-free, microwave-induced condensation of 2-aminoaryl alkyl ketones and ethyl 3-oxobutanoate in the presence of amberlite Na sr1L gave quinolinones in high yield when compared to other catalysts. Further, N-alkylation of the quinolinones was carried out effectively with various halides using amberlite Na sr1L. An N-alkylated quinolinone exhibited enhanced activities against B. subtilis, E. coli, and P. aeruginosa, similar to standard drug ampicillin. Two compounds showed effective activity against S. aureus, and one resulted in moderate activity against E. coli.