Biomedical subjects

B R Ratna

Publications and source records attributed to B R Ratna.

2 recordsLinked to original sources

PubMed1992

Effect of alcohol chain length on tubule formation in 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine.

Aqueous dispersions of 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine, on cooling below the chain melting temperature, form hollow cylindrical structures known as 'tubules'. We have studied the formation of tubules in methanol/water, ethanol/water and n-propanol/water. For each alcohol, there is a defined window of alcohol/water ratios in which the lipid precipitates with the tubule morphology. As the chain length of alcohol is increased, the window shifts towards lower alcohol fraction. Light scattering studies show that at very low lipid concentrations the tubules self-assemble directly from the isotropic phase where as for lipid concentrations greater than 4 mg/ml an intermediate L alpha phase is observed. These results indicate that the mechanism of tubule formation may be dependent on lipid concentration.

Alcohols↗

PubMed1991

Self-assembling phospholipid filaments.

Aqueous dispersions of double-chain phospholipids spontaneously assemble into closed bilayers called vesicles (or liposomes). Although the vesicles are in general topologically spherical, cylindrical and helical liposomes have sometimes been observed. We present here video-enhanced microscopic studies of a diacetylenic phospholipid dispersed in ethanol/water, which reveal the existence of unusual bilayer morphologies. On cooling the dispersion from the isotropic phase, we have observed the formation of long (of the order of hundreds of micrometres), thin (0.2-2 microns) filaments, which fluctuate strongly. When the temperature is decreased further, the filaments rapidly retract into a mass of lipid. At constant temperature, on the other hand, the filaments transform into torus or ring-like vesicles. Such non-spherical structures have been predicted theoretically but not previously observed experimentally.

Phosphatidylcholines↗