Publication: Effect of a dirhamnolipid biosurfactant on the structure and phase behaviour of dimyristoylphosphatidylserine model membranes
Authors
Oliva, Alfonso ; Aranda Martínez, Francisco José ; Ortiz López, Antonio ; Teruel Puche, José Antonio
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Publisher
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DOI
https://doi.org/10.1016/j.colsurfb.2019.110576
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info:eu-repo/semantics/article
Description
Abstract
Rhamnolipids are bacterial biosurfactants containing one or two rhamnose rings and a hydrophobic hydrocarbon
portion. These compounds are mainly isolated from Pseudomonas spp culture media, and have been shown to
present outstanding biological activities. A number of experimental works have shown that the interaction of
rhamnolipids with target membranes could play a role in these actions. Therefore the study of the interaction of
purified rhamnolipids with the various phospholipid components of biological membranes is of great interest.
This paper shows the phase behaviour of mixtures of 1,2-dimyristolylphosphatidylserine (DMPS) with a dir hamnolipid (diRL) fraction produced by P. aeruginosa. This experimental approach has been based on the use of
physical techniques such as Differential Scanning Calorimetry (DSC) and Fourier-Transform Infrared
Spectroscopy (FTIR). DSC indicated that the presence of increasing concentrations of diRL in the bilayer resulted
in a progressive broadening of the gel to liquid-crystalline phase transition of DMPS. In addition a complex
thermal behaviour was observed, with the presence of more than one transition at higher concentrations of the
biosurfactant, indicating phase separation. FTIR showed that diRL increased the proportion of gauche rotamers of
DMPS, thus affecting acyl chain order. The change in the frequency of the carboxylate stretching band of DMPS
observed upon interaction with diRL pointed toward changes in the local environment of the polar headgroup of
the phospholipid, resulting in a modification of its conformation or insertion within the bilayer. This result was
corroborated by the effect of diRL on the carbonyl and phosphate stretching bands of DMPS, showing an increase
of the hydration both in the gel and in the liquid-crystalline phase. Molecular Dynamics (MD) simulations gave
further support to the experimental results, showing diRL cluster formation as well as an augmented exposition
of DMPS to the water layer in the presence of the biosurfactant.
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Citation
Colloids and Surfaces B: Biointerfaces. 185 (2020) 110576
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