Spectral distribution of photocurrent in poly(6-tert-butyl-3-methyl-3,4-dihydro-2H-1,3-benzoxazine)

The spectral distribution of photoconductivity in poly(6-tert-butyl-3-methyl-3,4-dihydro-2H-1,3-benzoxazine) was studied in the sandwich configuration with indium tin oxide and silver electrodes. The photocurrent was found to originate mainly from the bulk dissociation of excitons with lesser contribution from electrode-mediated exciton dissociation. The molecule was fluorescent, but in the presence of the electron acceptor molecule 2,4,6-trinitrophenol (TNP), the intensity was reduced. The reduction in fluorescence intensity corresponded to an increase in photocurrent. The molecule showed photoconductivity in the visible without any sensitizers, which makes it suitable for stable photorefractive composites.     

Extension of shelf-life of whole-wheat flour by gamma radiation

The effect of low-dose gamma irradiation (0.25–1.00 kGy) on pre-packed whole-wheat flour (atta) was assessed in terms of physico-chemical properties, nutritional quality, chapati-making quality and sensory attributes. Semi-pilot scale storage studies on irradiated pre-packed whole-wheat flour revealed that there was no adverse effect of irradiation and storage up to 6 months of whole-wheat flour treated at doses up to 1.00 kGy on total proteins, fat, carbohydrates, vitamin B₁ and B₂ content, colour index, sedimentation value, dough properties, total bacterial and mould count. Storage of wheat flour resulted in slight increase in moisture, free fatty acids, damaged starch, reducing sugars and slight decrease in gelatinization viscosity.
However, irradiation as such had no effect on any of these parameters. Irradiation at 0.25 kGy was sufficient to extend the shelf-life of atta up to 6 months without any significant change in the nutritional, functional attributes. Chapaties made from irradiated atta (0.25 kGy) were preferred even after 6 months storage, compared with the control.     

Stimulation of large-conductance Ca2+-activated K+ channels by Evans blue in cultured endothelial cells of human umbilical veins

The effect of Evans blue (EB) on large-conductance Ca2+-activated K+ (BKCa) channels was investigated in cultured endothelial cells of human umbilical veins. In whole-cell configuration, EB (50 microM) reversibly increased the amplitude of K+ outward currents (IK). When the patch pipettes were filled with 10 mM EGTA, its stimulatory effect on IK was unaltered. Further application of EB in the presence of suramin, a blocker of P2-purinergic receptor, or AOPCP, an inhibitor of 5'-nucleotidase, still increased IK. However, charybdotoxin (100 nM) suppressed EB-induced increase in IK. In inside-out configuration, bath application of EB (50 microM) did not change single channel conductance but significantly increased the activity of BKCa channels. The EB-induced increase in the activity of BKCa channels was independent on internal Ca2+. EB (50 microM) shifted the activation curve of BKCa channels to less positive membrane potentials by approximately 20 mV. The change in the kinetic behavior of BKCa channels caused by EB in these cells is due to an increase in mean open time and a decrease in mean closed time. These results indicate that EB can stimulate the activity of BKCa channel in endothelial cells. This effect is unrelated to its blockade of P2-purinergic receptors or inhibition of 5'-nucleotidase. The direct stimulation of these ionic channels by EB may contribute to its effect on capillary permeability.     

Enzymatic characteristics of recombinant medium isozyme of 2'-5' oligoadenylate synthetase

P69 is an isozyme of the medium size class of human 2'-5' oligoadenylate synthetases. In this study, recombinant P69 was expressed and used for enzymological and structural investigations. Bacterially expressed P69 was inactive whereas the same protein expressed in insect cells was highly active. Whether this difference could be due to differential post-translational modifications of the protein was investigated. Mutations of appropriate residues showed that myristoylation of the protein was not necessary for enzyme activity. In contrast, inhibition of glycosylation of P69, by tunicamycin treatment of the insect cells, produced an enzymatically inactive protein. Recombinant P69 produced in insect cells was purified by affinity chromatography. It was a dimeric glycoprotein, very stable and completely dependent on double stranded (ds) RNA for activity. The enzyme catalyzed the non-processive synthesis of 2'-5'-linked oligoadenylate products containing up to 30 residues. 2'-O-Methylated dsRNA was incapable of activating P69 and a 25-base pair dsRNA was as effective as larger dsRNA. This expression system will be useful for large scale production of P69 and its mutants for structural studies.