Title
Effect of 1,4-bis(3-dodecylimidazolium-1-yl) butane bromide on channel form of gramicidin vesicles
Author
Rajan Patel, Mehraj ud din Parray, Upendra Kumar Singh, Asimul Islam, Pannuru Venkatesu, Shailza Singh, Himadri B. Bohidar
Year
2016
Journal
Colloids and Surfaces A: Physicochemical and Engineering Aspects
Abstract
The present work is a brief overview of technical applications of surfactant that involves membrane interactions, and surfactant-based protocols to study biological systems. Herein, we investigate the effect of ionic liquid type gemini surfactant [C12-4-C12im]Br2, (1,4-bis(3-dodecylimidazolium-1-yl) butane bromide) on the channel form of gramicidin vesicle. Gramicidin is a linear pentadecapeptide antibiotic that adopts a wide range of environment dependent conformations. Gemini surfactants are a novel class of surfactants possessing better physicochemical properties than conventional surfactants. Several spectroscopic approaches viz. fluorescence, time resolved fluorescence, circular dichroism (CD) and red edge excitation shift (REES) were employed to elucidate the interaction between gramicidin vesicle and [C12-4-C12im]Br2. Fluorescence and time-resolved fluorescence studies confirmed the quenching and accessibility of gramicidin fluorescence by [C12-4-C12im]Br2 through static quenching mechanism. CD results show the change in orientation of tryptophan within gramicidin vesicle on the addition of [C12-4-C12im]Br2. REES results suggested the possible interaction between gramicidin and [C12-4-C12im]Br2. In order to further validate our results, we exploited techniques like dynamic light scattering (DLS), dynamic surface tension (DST) and scanning electron microcopy (SEM). DLS results reveal increase in the size of gramicidin vesicles upon interaction with [C12-4-C12im]Br2. To our surprise, the DST shows the surface activity of gramicidin vesicles decreases with increase in concentration of [C12-4-C12im]Br2, suggesting possible interaction and complex formation between gramicidin and [C12-4-C12im]Br2. SEM images of gramicidin vesicle with different concentrations of [C12-4-C12im]Br2 differ markedly showing aggregation on the surface of vesicles, again supporting the above results. Docking results provide deep molecular insight into the probable interaction between tryptophan and D-leucine residues of gramicidin with [C12-4-C12im]Br2 through hydrophobic interactions. This work has prime importance in future to design ionic liquids based biomaterials for drug/gene delivery.
Instrument
J-1500
Keywords
Circular dichroism, Secondary structure, Ligand binding, Vesicle interactions, Materials, Biochemistry