ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The effect of concanavalin A (Con A) on the thermotropic behavior of positively charged, glycosyl-free lipids and their mixtures with zwitterionic lipids was investigated by differential scanning calorimetry.The gel to liquid-crystal phase transition enthalpy of pure dipalmitoylcholine (DPC) was found to be significantly increased in the presence of Con A (ΔH = 31.2 and 42.5 KJ mol-1 lipid in the presence and in absence of Con A, respectively). Addition of the lectin to DPC liposomes, furthermore, induces the appearance of a new phase transition centered at 320 K. These results are interpretable by a partial hydrophobic interdigitation of the lectin molecule into the liposomal bilayer.The effect of Con A on the phase behavior of three 2:1 mixtures of zwitterionic and of positively charged lipids was also investigated. Phase diagrams of the systems dipalmitoylphosphatidylcholine-dihydrosphingosine (DPPC-DHS), sphingomyelin-dipalmitoylcholine (SPM-DPC), and dimyristoylphosphatidylcholine-dipalmitoylcholine (DMPC-DPC) are presented. In lipid mixtures of limited miscibility (DPPC-DHS and SPM-DPC), Con A induces pronounced phase-separation effects. These effects are attributable to a direct hydrophobic interaction of the lectin with the liposomal bilayer and do not require the presence of specific receptor groups.The possible relationship between lectin-induced phase separations in the lipid matrix of biomembranes, and the observed changes in membrane permeability, membranal enzymatic activities, etc., is briefly discussed.
Additional Material:
11 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.360280403
