Formation of bilayer structures by arbutin and lysophosphatidylcholine in lipid membranes

M. FRÍAS; S. B. DÍAZ; E. A. DISALVO

Rosario, Santa Fé, Argentina.

Congreso; XXXV Reunión Anual de la Asociación Argentina de Biofísica; 2006

Asociación Argentina de Biofísica

Arbutin, a 4-hydroxyphenyl-beta-glucopyranoside accumulated to high concentrations in drought and frost resistant plants is composed by a glucose and a phenol moiety 1. It decreases the dipole potential binding to the carbonyl dehydrated population and to the phosphate groups of phosphatidylcholine membranes. This compound inserts in the same sites as lysophosphatidylcholine (lysoPC), an amphiphilic compound that disrupt the bilayer into micelles Arbutin, a 4-hydroxyphenyl-beta-glucopyranoside accumulated to high concentrations in drought and frost resistant plants is composed by a glucose and a phenol moiety 1. It decreases the dipole potential binding to the carbonyl dehydrated population and to the phosphate groups of phosphatidylcholine membranes. This compound inserts in the same sites as lysophosphatidylcholine (lysoPC), an amphiphilic compound that disrupt the bilayer into micelles Previous works of this laboratory have shown that arbutin inhibit the lysis produced by lyso PC in the gel state (c. a. 18C). LysoPC promotes a more disorganized membrane phase. This decrease in order is hindered in the presence of arbutin. This effect could be ascribed to an insertion of lysoPC into the membrane lipids avoiding the disruption into micelles. In this paper, an analysis of the changes produced by lysoPC in the presence and the absence of arbutin is presented. Turbidity assays, in MLV suggest that the lysoPC incorporates in the bilayer when arbutin is present forming more bilayer. This hypothesis is corroborated by the titration of lysoPC of LUV of DMPC in the presence and the absence of arbutin and electron microscopy observations The effect is noticeable at 18ºC but is not observed at 25ºC In parallel, the addition of lysoPC to a solution of arbutin shows also a turbidimetry increase, which is not observed when the lysoPC is added to water. Thus, the structures formed in by lysoPC in the presence of arbutin are much larger than those formed by lysoPC in water. It is likely that lysoPC and arbutin may form a complex in which the absence of a chain in the lysoPC is compensated by the aligning of arbutin in a parallel array. This would form a complex with cylindrical shape that would fit in bilayers or form exogenous bilayers.