Alexander Kaplun

Interaction of the globular domain of human C1q with Salmonella typhimurium lipopolysaccharide.

Gram-negative bacteria can bind complement protein C1q in an antibody-independent manner and activate classical pathway via their lipopolysaccharides (LPS). Earlier studies have implicated the collagen-like region of human C1q in binding LPS. In recent years, a number of C1q target molecules, previously considered to interact with collagen-like region of C1q, have been shown to bind via the globular domain (gC1q). Here we report, using recombinant forms of the globular head regions of C1q A, B and C chains, that LPS derived from Salmonella typhimurium interact specifically with the B-chain of the gC1q domain in a calcium-dependent manner. LPS and IgG-binding sites on the gC1q domain appear to be overlapping and this interaction can be inhibited by a synthetic C1q inhibitor, suggesting common interacting mechanisms.

Interaction of N-(2-hydroxybenzyl)-ω-amino carbonic acids, novel amphipathic fatty acid derivatives, with membrane: partition coefficients

The methods for partition coefficient (Kp) determination were developed for different concentrations of N-(2-hydroxybenzyl)-omega-amino carbonic acids, a new class of amphipathic fatty acid derivatives (An), their deutero (AnD) and bromine (AnBr) derivatives. To do this the following methods were used: 2H-NMR, equilibrium dialysis, centrifugation and fluorescence spectroscopy. Kp dependence on the An concentration is discussed. Kp values for AnBr were more than 120-times higher than those for An, the differences between them being smaller than those for the corresponding An. This series of new amphipathic compounds can be used as probes for membrane studies.