Mecanismos de interação molecular de polieletrólitos antimicrobianos em membranas modelo por espectroscopia vibracional não linear

Abstract

AGRADECIMENTOSA Deus, por tudo e por cada segundo de vida.A toda minha família, pelo amor, exemplo, suporte e compreensão em todos os momentos. Em especial: Pai, obrigado por me ensinar a ser paciente e organizado; Mãe, obrigado por me ensinar a trabalhar com amor e determinação; Maninha, obrigado por nunca me deixar esquecer que é a companhia das pessoas queridas que faz a vida valer a pena. A todos os docentes dos quais fui aluno -muito obrigado pela dedicação e paciência.Aos funcionários do Serviço da Pós-Graduação do IFSC, Silvio, Ricardo e Priscila, pelo profissionalismo, paciência e atenção.Às meninas da biblioteca, Cris, Neusa e Ana, por sempre serem muito atenciosas, Enfim, a todos os que estiveram presentes nesta longa trajetória, que eu já tenha mencionado ou não: saibam que eu sou um pedacinho de cada um de vocês e eu sou muito grato pela nossa convivência e experiência de vida compartilhada. showed that both PAH and CO led to a small expansion of DPPC monolayers. However, for DPPG monolayers both polyelectrolytes led to significant expansion, with CO causing a more dramatic effect. SFG spectra in the CH stretch range showed that the lipid chain conformation remained always well ordered in all cases (slightly less ordered upon interacting with PAH), despite membrane expansion. This indicates that CO were inserted in the monolayer, forming islands of CO within the lipid film. Changes in the SFG spectral lineshape of OH stretches for the interfacial water molecules indicated that PAH adsorption on both DPPC and DPPG films was able to overcompensate the lipid negative charge and led to an overall surface charge reversal. The SFG spectra of the phosphate groups also indicated that in pure water the DPPC headgroups had a more ordered orientation than in the case of DPPG. Nevertheless, upon interaction with the cationic polyelectrolytes, the DPPG headgroups also become ordered, with a preferential orientation towards the subphase. Experiments with the antimicrobials injected in the subphase under a condensed Langmuir film indicated that CO were also capable of monolayer penetration, albeit causing a reduced film expansion. This comparison indicates that the choice of experimental methodology affects the outcome, but both may be complementary, as they may represent different phases of a biomembrane lifecycle.The detailed view provided here for the molecular interaction of these polyelectrolytes with lipid films may shed light on the mechanism of their biocidal activity and aid on a rational design of new antimicrobial polymers.