Problems involved in dialyzing low concentrations of inorganic pyrophosphate

Dialysis membrane interference in human T-lymphocyte proliferation assays

Dialysis with cellulose acetate membranes is frequently performed in the laboratory in order to remove possible interfering substances from various biological fluids. However, retentates from dialysis, compared to undialysed samples, inhibited the sub-maximal phytohaemagglutinin-induced proliferation of human T-lymphocytes. This inhibition was accentuated when the samples to be dialysed contained normal human serum. Four different membranes all produced similar degrees of inhibition when samples of varied composition were dialysed. It is unlikely that the inhibitory effect on the MNC/M phi-DC proliferations is due to glycerol, heavy metals or sulphuric compounds in the retentate. The most likely explanation of the inhibition is liberation of a substance from the membrane to the retentate during dialysis. Our experiments suggested two solutions. Simply boiling the dialysis tubing--internal as well as external--solved the problem. Another way to circumvent the problem is to use a commercially available dialysis membrane which is completely devoid of this inhibitory effect.

The effect of ethylenediaminetetra-acetate on Pseudomonas alcaligenes and the composition of the bacterial cell wall

1. EDTA in borate buffer has a marked bactericidal effect on Pseudomonas alcaligenes, which is more sensitive than Pseudomonas aeruginosa. The bactericidal effect is accompanied by solubilization of lipopolysaccharide and release of intracellular solutes. These effects are more pronounced at pH9.2 than 7.1. 2. Cell walls of P. alcaligenes were prepared and from them were obtained the readily extracted lipids and the fractions given by treatment with aqueous phenol. 3. The cell walls and the above components were analysed and results are compared with those for P. aeruginosa. 4. Lipopolysaccharide obtained by treatment of cell walls with aqueous phenol is contaminated with glycosaminopeptide to a variable extent. 5. The lipopolysaccharide contains less neutral sugar but more phosphorus than the lipopolysaccharide of P. aeruginosa; fucosamine is not a component of the lipopolysaccharide of P. alcaligenes.