LAUSR

Abstract The current work investigates the action of extracts of exopolysaccharides and proteins (EPS) from the microalgae Cryptomonas tetrapirenoidosa immobilized on Langmuir-Blodgett films (LB) of the lipid dioctadecyldimethylammonium bromide (DODAB). The main objective of this paper was to evaluate the changes provided in the structure of the lipid-algal biomolecules composite film by Polarization Modulation Infrared Reflection-Absorption Spectroscopy (PM-IRRAS) when these supramolecular structures are immersed in solutions with metallic ions of environmental interest. EPS was incorporated at DODAB monolayer as analyzed with surface pressure-area isotherms, PM-IRRAS and Brewster Angle Microscopy. The mixed films were transferred to solid supports as LB films and amide bands related to proteins present in the extract were analyzed since they are highly sensitive to molecular conformation. The films were put in contact with selected ions of environmental interest, such as lead, cooper, iron, and mercury, and changes in the protein structure were investigated with PM-IRRAS. The results showed a specific interaction of each ion with the LB films, which may be promising for building biosensors with specificity for metallic ions.