Inlet-line diversion decreased bacterial contamination during two-arm collections by more than 46%. Concurrently, doubling the sample volume was associated with a 54% relative increase in culture sensitivity. These interventions act cooperatively to decrease bacterial risk.

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Singlet oxygen (1O2) can react with cholesterol (Ch) to give three possible ene-addition hydroperoxides: 3 beta-hydroxy-5 alpha-cholest-6-ene-5-hydroperoxide (5 alpha-OOH), 3 beta-hydroxycholest-4-ene-6 alpha-hydroperoxide (6 alpha-OOH), and 3 beta-hydroxycholest-4-ene-6 beta-hydroperoxide (6 beta-OOH). The rates of dye-sensitized photogeneration and also the fates of 5 alpha-OOH and 6 beta-OOH in membrane bilayers have been studied and compared. Irradiation of unilamellar [14C]Ch/phospholipid vesicles in the presence of aluminum phthalocyanine tetrasulfonate or merocyanine 540 resulted in formation of 5 alpha-OOH and 6 beta-OOH, as determined by high performance liquid chromatography with radiochemical or electrochemical detection. The initial rate of 6 beta-OOH formation was 30-35% that of 5 alpha-OOH in a variety of liposomal systems. However, after a lag, 5 alpha-OOH invariably decayed via allylic rearrangement to 7 alpha-OOH (also known to be a free radical product), whereas 6 beta-OOH accumulated in unabated fashion until Ch depletion became limiting. Photooxidation of Ch in an isolated natural membrane (erythrocyte ghost) or in L1210 leukemia cells gave similar results. When the reaction was carried out in pyridine or methanol, the rate of 6 beta-OOH formation relative to 5 alpha-OOH was reduced by approximately half, with essentially no isomerization of the latter to 7 alpha-OOH.(ABSTRACT TRUNCATED AT 250 WORDS)

It has been reported that Zn7-metallothionein (MT), contains one weak binding site for Zn2+. To test this conclusion, rabbit liver MT isolated at pH 7 was reacted with chelating agents of modest affinity for Zn2+. Contrary to the previous study, no evidence was found for Zn2+ stoichiometically bound to the protein with an apparent stability constant of about 108. Indeed, stability constant measurements based upon competition between Zn7-MT and ligands of known stability with Zn2+ showed that all of the protein bound Zn2+ displayed the same stability constant at pH 7.4 and 25° C of (1.7±0.6) × 1011. Brief reaction of Zn7-MT with strong acid converted it into MT* and upon reneutralization into Zn7-MT*, which demonstrated reactivity of about 1 Zn2+/mol MT with competing ligands. Acid titration of Zn7-MT to pH 2 or below rapidly resulted in the formation of Zn7-MT* that displayed biphasic titration with base, revealing the rebinding of lower affinity Zn2+ between pH 5 and 7. Since MT is commonly acidified during preparation, care must be taken to document which form of the protein is present in subsequent experiments at pH 7.