Articles written in Journal of Biosciences
Volume 2 Issue 1 March 1980 pp 1-13
High resolution nuclear magnetic resonance spectra of native or protease-treated hen’s egg yolk plasma (very low density lipoproteins) were taken either in water or deuterated water; the protease-treated samples showed a sharpening of choline methyl proton signal of phospholipid, indicating the hindrance of the choline head-group rotation by the phospholipids in the native very low density lipoproteins. With both native and the protease-treated egg yolk plasma, elevated temperatue increased the signal intensity and produced line-sharpening of Q choline methyl protons and the — CH2-C-protons of the methylene group adjacent to the carboxyl group of esterified fatty acids, indicating prior restriction of mobility of these groups. Total extracted lipids of egg yolk plasma containing traces of chloroform, methanol and water (which keep the sample in one phase) also gave similar temperature dependence. Addition of water to the same sample and sonication resulted in the loss of temperature dependence. Frozen and thawed protease-treated egg yolk plasma also behaved in a similar manner. The absence of temperature dependence in these latter two samples is believed to be due to formation of bilayers of phospholipids following phase separation of triglycerides and phospholipids. The results support a model in which the lipoprotein particles of the egg yolk plasma have a lipid-core structure containing triglycerides in the centre with a monomolecular layer of lecithin at the surface, the polar heads of which are surrounded by proteins.
Volume 11 Issue 1-4 March 1987 pp 299-309
Lipid thermal transition patterns of the very low density lipoproteins in native and variously treated egg yolk plasma and extracted total very low density lipoproteins lipids have been recorded by differential scanning calorimetry in the temperature range 220–300 K, after lowering the freeze endotherm of free water in the sample with ethylene glycol.
Three distinguishable patterns of lipid endotherms, designated types 1, 2 and 3 were obtained, respectively, from (i) native very low density lipoproteins in egg yolk plasma, (ii) freeze damaged very low density lipoproteins in gelled egg yolk plasma and (iii) extracted total lipids of very low density lipoproteins dispersed in water. Protein-depleted ‘lipid core’ particles of very low density lipoproteins obtained by exhaustive proteolysis of egg yolk plasma gave type 2 lipid transition pattern suggesting similarities in its lipid association with that of the freeze damaged very low density lipoproteins. Freezing the ‘lipid cores’ of very low density lipoproteins led to phase separation and gave type 3 lipid transition pattern of water-dispersed, phase-separated total very low density lipoprotein lipids. Relative heat uptake of native very low density lipoproteins in egg yolk plasma was about 15% lower than the freeze damaged sample or of the extracted total lipids.
Treatments which prevented aggregation and gelation of very low density lipoproteins in egg yolk plasma during frozen storage, namely with additives such as glycerol or NaCl, gave subsequent lipid transition pattern intermediate between type 1 and 2, indicating that while very low density lipoprotein aggregation is prevented, additives do not altogether prevent changes in lipid association in these particles.
Volume 23 Issue 5 December 1998 pp 537-538 Clipbord
Volume 26 Issue 2 June 2001 pp 193-203
Volume 27 Issue 5 September 2002 pp 443-444 Clipboard