RIGID MULTILLAMELAR BILAYER COOPERATIVITY IS MODIFIED BY NON COVALENTLY LINKED NEURAMINIC-5-ACID. A ESPECTROPHOTOMETRIC DETERMINATION.

DEL VALLE ALONSO-ROMANOWSKI, SILVIA; L ROMERO, E; J MORILLA, M

GENERAL PHYSIOLOGY AND BIOPHYSICS

GENERAL PHYSIOL AND BIOPHYSICS

Lugar: Bratislava , Slovak Republic; Año: 2001 vol. 20 p. 113 - 129

0231-5882

By means of recording a simple serie of merocynine 540 spectra, we present a method to calculate the value proportional to cooperative unit size of membranes (n). Our calculations, applied to different liposomal  samples processed in the presence or absence of sugars, in high or low ionic strength showed two main results. First, that any temperature cycling in high ionic strength of rigid DPPCbilayers will modify the membrane cooperativity. Second, the presence of polysacharide Neu-5-ac in solution will always produce a strong drop in cooperativity of a rigid membrane of DPPC, whenever the negative charge is fully exposed. Tbhis last result indicates a differential ability of charged Neu-5-ac to disrupta rigid membrane structure, even in the absense of a covalent linkage and-remarkably- in fully hydrated media.