Effect of the ionic strength of pulsed electric field treatment medium on the physicochemical and structural characteristics of lactoferrin

Pulsed electric field (PEF) treatment (35 kV cm(-1) for 19.2 μs using bipolar 2 μs pulses) was conducted on bovine lactoferrin (LF; 0.4 mg mL(-1)) prepared in simulated milk ultrafiltrate (SMUF), at concentrations between 0.2× and 2× normal strength, with electrical conductivities ranging from 0.17 to 1.04 S m(-1). The physicochemical and structural characteristics (LF content by a spectrophotometric and an ELISA method, surface hydrophobicity, electrophoretic mobility, far-UV circular dichroism spectra, and tryptophan fluorescence) of LF dissolved in SMUF of all strengths tested were not changed after PEF treatment. The PEF treatment of LF in 0.2 strength SMUF did not cause the release of LF-bound ferric ion into the aqueous phase, with a concentration of LF-bound iron being the same as that of the untreated LF control (174 μg L(-1)). However, in treatment media with higher ionic strengths, ferric ion was released from the LF molecule into the aqueous phase. The concentration of LF-bound iron decreased from 174 μg L(-1) for the LF treated in 0.2 strength SMUF to 80 μg L(-1) for that treated in double-strength SMUF. The results suggest that the PEF-induced iron depletion of LF does not appear to cause an appreciable conformational change in LF molecules. PEF treatment could be developed as a novel physical way to produce iron-depleted LF, as an alternative to the existing chemical method.     

The evaluation of adult plant resistance to powdery mildew (Erysiphe graminis f.sp. avenae) in transgressive lines of oats

Summary Previously identified segregant lines of oats with levels of adult plant resistance to powdery mildew (Erysiphe graminis f.sp. avenae) better than the resistant parent maintained this high level of resistance in field nurseries over two growing seasons. This enhancement was not expressed on inoculated detached leaves under laboratory conditions where no differences between the more resistant parent cv. Maldwyn and the most resistant segregants was detected. Reduced resistance was not detected in tests where leaf segments of the transgressive lines were inoculated with trained isolates. Problems associated with selecting for adult plant resistance under both field and laboratory conditions are discussed.     

Gating the selectivity filter in ClC chloride channels

ClC channels conduct chloride (Cl-) ions across cell membranes and thereby govern the electrical activity of muscle cells and certain neurons, the transport of fluid and electrolytes across epithelia, and the acidification of intracellular vesicles. The structural basis of ClC channel gating was studied. Crystal structures of wild-type and mutant Escherichia coli ClC channels bound to a monoclonal Fab fragment reveal three Cl- binding sites within the 15-angstrom neck of an hourglass-shaped pore. The Cl- binding site nearest the extracellular solution can be occupied either by a Cl- ion or by a glutamate carboxyl group. Mutations of this glutamate residue in Torpedo ray ClC channels alter gating in electrophysiological assays. These findings reveal a form of gating in which the glutamate carboxyl group closes the pore by mimicking a Cl- ion.     

Adrenalectomy and coat color in deer mice

Adrenalectomy in prairie deer mice is followed by a profound darkening of the fur which occurs with in 1 to 3 months. The phenomenon is most noticeable on the normally unpigmented ventral surfaces which turn dark gray or black. A possible mechanism for such hyperpigmentation would involve increased release of inelanocyte-stimulating hormones.     

Hemagglutinin variants of reovirus type 3 have altered central nervous system tropism

Variants of the Dearing strain of reovirus type 3 with antigenically altered hemagglutinin proteins are much less neurovirulent than the parental virus. When injected intracerebrally into mice these variants infected a subset of the brain neurons that were infected by the parental virus. When injected intraperitoneally, the variants did not spread to the brain. These results indicate that minor modifications of the reovirus hemagglutinin dramatically alter the ability of the virus to spread into and injure the central nervous system.     

Nanomechanical basis of selective gating by the nuclear pore complex

The nuclear pore complex regulates cargo transport between the cytoplasm and the nucleus. We set out to correlate the governing biochemical interactions to the nanoscopic responses of the phenylalanineglycine (FG)-rich nucleoporin domains, which are involved in attenuating or promoting cargo translocation. We found that binding interactions with the transport receptor karyopherin-beta1 caused the FG domains of the human nucleoporin Nup153 to collapse into compact molecular conformations. This effect was reversed by the action of Ran guanosine triphosphate, which returned the FG domains into a polymer brush-like, entropic barrier conformation. Similar effects were observed in Xenopus oocyte nuclei in situ. Thus, the reversible collapse of the FG domains may play an important role in regulating nucleocytoplasmic transport.