Biomedical subjects

M de Cózar

Publications and source records attributed to M de Cózar.

4 recordsLinked to original sources

PubMed1987

Vibrational spectra and structure of myelin membranes.

Raman and infrared spectroscopy have been simultaneously applied, for the first time, to the study of myelin membranes and their proteolipid protein (PLP) so as to obtain information on the secondary structure of proteins and the ordering of lipid chains. The vibrational spectra were recorded at physiological pH using a non-denaturing detergent (n-octyl-beta-D-glucopyranoside) in phosphate buffer. Neither the buffer nor the detergent interfere spectroscopically with the amide bands from proteins. The spectra reveal that the predominant secondary structure in the polypeptide backbone in myelin is the helix. The proteolipid protein was found to be more disordered than the polypeptide arrangement of the myelin membrane, as deduced from the relative intensities and halfwidths of characteristic infrared amide I bands. beta-form and turns are also present, the amount of these structures being higher in PLP. The study of the Raman spectra of vC-C and vC-H regions made it possible to obtain information on the lipid chain order.

Animals↗

PubMed1987

Ionophoric properties of the proteolipid apoprotein from bovine brain myelin.

Ionophoric properties of the Proteolipid Apoprotein have been assayed. This is a highly purified and delipidated intrinsic myelin membrane protein, isolated from bovine brain white matter. The preparation of myelin membrane vesicles or the incorporation of purified protein into Dimiristoylphosphatidylcholine liposomes have been carried out. According to our results, the myelin Proteolipid protein may act as a Na+ and Rb+ (K+) unidirectional ionophoretic channel, which main physiological role could be related to the maintenance of ionic equilibrium of myelin sheath around the axons.

Animals↗

PubMed1983

The delipidation of brain proteolipid protein by ultrafiltration.

It has been very difficult to prepare the apoprotein moiety of brain white matter proteolipid so that it is completely devoid of complex lipids, without suffering aggregation and protein denaturation. The reason is that complex lipids are tightly bound to the proteolipid apoprotein. Using a new ultrafiltration method, we obtained, in a gradual way and in a relatively short time, more than 99% delipidation in water-saturated n-butanol, with and without 0.1 M acetic acid, and recovered up to 86% of the protein with no detectable reducing sugars remaining. The delipidated protein remained in solution and in a relatively nondenatured state for several days. In 2% sodium dodecyl sulfate (SDS)-aqueous media, 90% of the lipids were removed and the yield of recovered protein in solution was near 90%; nearly 6% of the reducing sugars remained in the apoprotein. A higher delipidation was obtained by washing with 0.1 M NaOH. The content of reducing sugars was greater but the protein was less stable. When 10% SDS was employed to dissociate lipid-protein interaction, an almost complete delipidation was obtained and reducing sugars disappeared.

Animals↗

PubMed1982

Method for lyophilizing brain proteolipid preparations that increases subsequent solubilization by detergents.

A frozen mixture of solubilized brain proteolipid proteins in chloroform-methanol is not sublimable in a vacuum. However, when 7 to 10 volumes of benzene were added to a chloroform-methanol solution containing 5 mg of proteolipid protein per ml, the proteolipid proteins remained in solution for a while and the frozen mixture was easily sublimated at 2mm Hg. Before the addition of benzene, higher concentrations of protein required the acidification of the medium to avoid precipitation of proteolipid proteins. In contrast to what happens when proteolipid proteins are obtained by the evaporation of the organic mixture at room temperature, the protein obtained by lyophilization was soluble in aqueous solutions of ionic and nonionic detergents. Sodium dodecyl sulfate at 0.6 to 0.7% concentration completely solubilized the proteolipid protein obtained by lyophilization. With the nonionic detergents Lubrol WX and Triton X-100, a solubilization between 50 and 65% was achieved. Sodium deoxycholate was practically ineffective. Triton X-100 showed selectivity in solubilizing certain proteins. The role of lipids in the solubilization of proteolipid proteins with detergents is discussed.

Animals↗