Home General Physiology and Biophysics 2007 General Physiology and Biophysics Vol.26, p.290-297, 2007

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General Physiology and Biophysics Vol.26, p.290-297, 2007

Title: Effect of amphiphilic surfactant LDAO on the solubilization of DOPC vesicles and on the activity of Ca2+-ATPase reconstituted in DOPC vesicles
Author: J. Karlovska, F. Devinsky, P. Balgavy
Abstract: Solubilization of large unilamellar 1,2-dioleoylphosphatidylcholine (DOPC) vesicles by N-dodecyl-N,N-dimethylamine-N-oxide (LDAO) was studied using turbidimetry. From turbidity data, the LDAO partition coefficient between the aqueous phase and DOPC bilayers was obtained. Using this partition coefficient, the LDAO:DOPC molar ratio in the bilayer was calculated and effects of LDAO on the bilayer stability, bilayer thickness and on the phosphohydrolase activity of sarcoplasmic reticulum Ca2+ transporting ATPase (SERCA) reconstituted into DOPC were compared at the same LDAO:DOPC molar ratios in the bilayer. The sequence “bilayers in vesicles – bilayer fragments (flat mixed micelles) – tubular mixed micelles – globular mixed micelles” was suggested for the solubilization mechanism of DOPC vesicles from the combined turbidimetric and small-angle neutron scattering (SANS) results. The effective molecular packing parameter δ = 0.5, corresponding to the mixed bilayer – mixed tubular micelle transition, was calculated from fragmental DOPC and LDAO volumes at the molar ratio LDAO:DOPC = 2.00 in bilayers, in the middle of transition region observed earlier experimentally by small-angle neutron scattering (SANS). The bilayer thickness decrease induced by LDAO in DOPC observed by SANS did not result in the SERCA phosphohydrolase activity decrease and this indicates that some other factors compensated this bilayer effect of LDAO. The ATPase activity decrease at higher LDAO concentrations was caused by the bilayer deformation. This deformation resulted in the formation of non-bilayer aggregates in LDAO+DOPC system.
Keywords: N-dodecyl-N,N-dimethylamine-N-oxide — Dioleoylphosphatidylcholine — Unilamellar vesicles — Solubilization — Partition coefficient
Year: 2007, Volume: 26, Issue: Page From: 290, Page To: 297


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