Abstract-The chloride channel ClC-Kb is expressed in the basolateral cell membrane of the distal nephron and participates in renal NaCl reabsorption. Loss-of-function mutations of ClC-Kb lead to classic Bartter syndrome, a rare salt-wasting disorder. Recently, we identified the ClC-Kb T481S polymorphism, which confers a strong gain-of-function effect on the ClC-Kb chloride channel. The present study has been performed to explore the prevalence of the mutation and its functional significance in renal salt handling and blood pressure regulation. As evident from electrophysiological analysis with the 2-electrode voltage-clamp technique, heterologous expression of ClC-Kb T481S in Xenopus oocytes gave rise to a current that was 7-fold larger than the current produced by wild-type ClC-Kb. The prevalence of the mutant allele was significantly higher in an African population from Ghana (22%) than in whites (12%). As tested in 1 white population, carriers of ClC-Kb T481S were associated with significantly higher systolic (by Ϸ6.0 mm Hg) and diastolic (by Ϸ4.2 mm Hg) blood pressures and significantly higher prevalence (45% versus 25%) of hypertensive (Ն140/90 mm Hg) blood pressure levels. Individuals carrying ClC-Kb T481S had significantly higher plasma Na ϩ concentrations and significantly decreased glomerular filtration rate. In conclusion, the mutation ClC-Kb T481S of the renal epithelial Cl

Field desorption mass spectra of a tripeptide Pro-Leu-Gly-NH,, a pentapeptide Cbz-Gly-Pro-Leu-Gly-Pro and a nonapeptide Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg are presented. In each case, a [MI? or [M + I]' peak of the peptide is obtained. Sufficient fragmentation of the peptide backbone occurred to allow sequence determination of all three peptides. The pentapeptide produced [MI:, [M + 1]+ and [M + 21: ions which also included molecules of ethylacetate, ethanol and/or water bound to the ion.

The main site of decomposition of methyl bromide in cocoa beans was shown to be in the alcohol-insoluble proteins of the shells. The methyl group of the fumigant becomes covalently bonded to the a-amino group of the various amino acids, the imidazole ring of histidine and the &-amino group of lysine. An amino acid analysis of cocoa beans shows that methionine is the limiting essential amino acid and that cysteine is concentrated in the alcohol-insoluble proteins of the nib.