New pyrazole-tethered Schiffs bases as ligands for the Suzuki reaction

Pyrazole-tethered Schiffs base ligands 2 promote Suzuki coupling of aryl bromides and chlorides with phenylboronic acid efficiently under mild conditions.     

Immobilization of Aspergillus nidulans SU04 cellulase on modified activated carbon

The present study deals with the immobilization of Aspergillus nidulans SU04 cellulase onto modified activated carbon (MAC). The effect of contact time, cellulase concentration, MAC dosage, and temperature for maximum immobilization percentage and immobilization capacity is investigated. The equilibrium nature of immobilization is described by Langmuir and Freundlich isotherms. The kinetic data were tested using the pseudo first order. The activation energy of immobilization was evaluated to be 11.78?J?mol^?1. Results of the thermodynamic investigation indicate the spontaneity (?G <0), slightly endothermic (?H >0), and irreversible (?S >0) nature of the sorption process. Entropy and enthalpy were found to be 41.32 J?mol^?1?mg^?1 and 10.99?kJ?mol^?1, respectively. The Gibbs free energy was found to be ?22.79?kJ?mol^?1. At 80?rpm, 323?K, 2?h, 5?mg of MAC, immobilization capacity was 4.935?mg cellulase per mg of MAC from an initial cellulase concentration of 16?mg?ml^?1 with retention of 70% of native cellulase activity up to 10 cycles of batch hydrolysis experiments. The diffusion studies that were carried out revealed the reaction rate as ??mol?min^?1. At optimized conditions, immobilized cellulase had a higher Michaelis?CMenten constant, K _m of 1.52?mmol and a lower reaction rate, V _max of 42.2???mol?min^?1, compared with the free cellulase, the K _m and V _max values of which were 0.52?mmol and 18.9???mol?min^?1, respectively, indicating the affinity of cellulase for MAC matrix.     

Three-step synthesis of cyclopropyl peptidomimetics

An efficient approach to novel cyclopropyl peptidomimetics has been developed. The synthetic route involves a cyclopropanation using ethyl (dimethylsulfuranylidene)acetate (EDSA) as the key step and affords a cyclopropyl peptidomimetic core in three steps from protected amino acid Weinreb amides.     

Copolymerization of n‐butylacrylate with methylmethacrylate by a novel photoinitiator, 1‐(bromoacetyl)pyrene

The photopolymerization efficiency of pyrene (Py), 1‐acetylpyrene (AP), and 1‐(bromoacetyl)pyrene (BP) for copolymerization of n‐butylacrylate (BA) with methylmethacrylate (MMA) was compared. A kinetic study of solution copolymerization in DMSO at 30 ± 0.2°C showed that the Py could not initiate copolymerization even after 20 h, whereas with AP as initiator, less than 1% conversion was observed. However, introduction of a Br in α‐methyl group of AP significantly enhanced the percent conversion. The kinetics and mechanism of copolymerization of BA with MMA using BP as photoinitiator have been studied in detail. The system follows nonideal kinetics (R_p α [BP]^0.67[BA]¹[MMA]^0.98), and degradative solvent transfer reasonably explains these kinetic nonidealities. The monomer reactivity ratios (MRRs) of MMA and BA have been estimated by the Finemann–Ross and Kelen–Tudos methods, by analyzing copolymer compositions determined by ¹H‐NMR spectra. The values of r₁ (MMA) and r₂ (BA) were found to be 2.17 and 0.44, respectively, which suggested the high concentration of alternating sequences in the random copolymers obtained. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 261–267, 2007     

Working group report: Quantum chromodynamics

This is the report of the QCD working sub-group at WHEPP-8 which was part of the QCD and QGP working group. Discussion and work on some aspects of resummation and parton distribution are reported.     

Modulation of Fluorophore Environment in Host Membranes of Varying Charge

The net electrical charge of the biological membrane represents an important parameter in the organization, dynamics and function of the membrane. In this paper, we have characterized the change in the microenvironment experienced by a membrane-bound fluorescent probe when the charge of the phospholipids constituting the host membrane is changed from zwitterionic to cationic with minimal change in the chemical structure of the host lipid. In particular, we have explored the difference in the microenvironment experienced by the fluorescent probe 2-(9-anthroyloxy)stearic acid (2-AS) in model membranes of zwitterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and cationic 1-palmitoyl-2-oleoyl-sn-glycero-3-ethylphosphocholine (EPOPC) which are otherwise chemically similar, using the wavelength-selective fluorescence approach and other fluorescence parameters. Our results show that the microenvironment experienced by a membrane probe such as 2-AS is different in POPC and EPOPC membranes, as reported by red edge excitation shift (REES) and other fluorescence parameters. The difference in environment encountered by the probe in the two cases could possibly be due to variation in hydration in the two membranes owing to different charges.     

Optimization of cryopreservation of stem cells cultured as neurospheres: comparison between vitrification, slow-cooling and rapid cooling freezing protocols

We compared cryopreservation of mammalian neural stem cells (NSCs) cultured as neurospheres by slow-cooling (1 C/min) in 10% (v/v) DMSO and cryopreservation by immersion into liquid nitrogen in ethylene glycol (EG)-sucrose solutions that support vitrification (40% (v/v) EG, 0.6 M sucrose) or that do not (37% v/v) EG, 0.6 M sucrose and 30% (v/v) EG, 0.6 M sucrose); the concentration of penetrating cryoprotectant in the last two solutions was lowered with the intention to reduce their toxicity towards NSCs. To protect against contamination a straw-in-straw technique was employed. Vitrification offered the best combination of preservation of structural integrity of neurospheres, cell viability (>96%), multipotency and karyotype. Rapid cooling in 37% (v/v) EG, 0.6 M sucrose afforded good viability but did not preserve structural integrity. Rapid cooling in 30% (v/v) EG, 0.6 M sucrose additionally reduced cell viability to 77%. Slow-cooling reduced cell viability to 65% and damaged the neurospheres. This study suggests that, in contrast to freezing, vitrification has immense potential for the cryopreservation of stem cells cultured as neurospheres or in other structured cultures.