Peptide synthesis catalysed by papain immobilised on polymer supports: effect of the macromolecular structure and reaction conditions on synthesis

Papain immobilised on different types of polymeric supports was used for the synthesis of peptides in aqueous-organic solvent mixtures. The effects of the nature of the polymer support, degree of crosslinking, nature and length of the spacer grouping between the polymer backbone and the point of attachment of the enzyme, and reaction conditions like pH, concentration of nucleophile and the immobilised enzyme content on the course of the synthesis were investigated. Divinylbenzene-crosslinked polystyrene, divinylbenzenecrosslinked polyacrylamide and N,N'-methylene-bis-acrylamide-crosslinked polyacrylamide systems immobilised with papain were used for these studies. An increase in the length of the spacer arm and an increase in hydrophilicity invariably resulted in an increase in the yield of the peptide synthesis. Papain immobilised on polystyrene-PEG supports and tetraethyleneglycol-crosslinked polystyrene supports was determined to be more efficient in effecting peptide synthesis when compared to other polystyrene-based supports

Curing studies on epoxy resin with phosphorylated amine*

93-99<span style="font-size:14.0pt;line-height: 115%;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" color:black;mso-ansi-language:en-in;mso-fareast-language:en-in;mso-bidi-language:="" hi"="" lang="EN-IN">Mechanical properties of an epoxy resin system (neat resin castings) based on diglycidyl ether of bisphenol-A (DGEBA) cured with different amounts of phosphorous based amine, tris(3-aminophenyl) phosphine oxide (TAP) are reported. Influence of stoichiometric imbalance on the thermoelastic properties of the epoxy-amine system is also discussed. Testing of dynamic mechanical properties has been done using Rheovibron DDV-III-EA from ambient temperature to 250 °C. The results show that variation in stoichiometry can affect material properties such as modulus (Em) and glass transition temperature (Tg). Various parameters, viz. molecular weight between crosslinks (Mc), apparent front factor (a), and crosslink density (ρc) have been calculated for all the compositions. Also, the effect of thermal and boiling water ageing on material properties for 100 h are reported.</span

The epidemiology of AIDS in the Vellore region, Southern India

Objective: To describe the epidemiology of patients with AIDS in Vellore region, Southern India. Design and methods: Sixty-one patients with AIDS were diagnosed and treated between July 1987 and June 1992. Information on their demographic characteristics and probable modes of acquiring HIV infection was collected at interviews with them and their spouses. Results: There was a progressive increase in the number of patients seen over the 5 years. The mean ages of the 51 men and the 10 women were 33 and 29 years, respectively. Of the 44 patients from our district (population, 5 million), 28 were from Vellore town and 10 from rural areas. Forty-seven (92%) men had frequently used prostitutes. Of the women, four were prostitutes, one had had multiple sex partners and five had not had extramarital sexual contact. One man and one woman had no other risk factor except blood transfusion. Thirty-one (51%) patients had died by August 1992. Conclusion: The AIDS epidemic in this region is in its early ascending phase, with a doubling time of approximately 1 year. Most men with AIDS were infected by heterosexual contact with prostitutes, while some women were prostitutes themselves. Together with the male-to-female ratio of 5:1, these results suggest that the male population at risk has sex with a much smaller population of female prostitutes, constituting the major chain of transmission. HIV infection is occurring in both urban and rural populations