Valinomycin-induced pore formation in thin lipid film and its effect on splay and bend elastic constant

Abstract

Abstract

Valinomycin-induced rapid changes in the orientation patterns of lipid molecules under an applied field were observed in 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) thin films, aligned on polyvinyl-alcohol-coated indium tin oxide (ITO) glass electrodes both below (L_β) and above (L_α) phase transition temperatures of DPPC. With the increasing concentration of valinomycin, Freedericksz's transition patterns change significantly. The values of splay (κ₁₁) and bend (κ₃₃) elastic constant changed by several orders of magnitude depending upon the concentration of valinomycin in the DPPC thin films. From the micrographs of field emission scanning electron microscopy, it was clear that pore formation on DPPC thin films would be a reason behind the decay of elastic constant. The decay of elastic constant was described by an exponential decay formula, ${\displaystyle y\hspace{0.17em}\text{=}\hspace{0.17em}{A}_{\text{1}}{\text{e}}^{-x\text{/}{t}_{\text{1}}}+y_0}$. From this point of view, we propose that our system can be used as a biosensor to detect antibiotic-like valinomycin.

Keywords:

• valinomycin
• Freedericksz's transition
• biosensor
• lipid aggregates
• membrane elasticity

Acknowledgements

The helpful discussion with Dr Ashesh Nandy and Dr Smarajit Manna, Centre for Interdisciplinary Research and Education, and Dr Suman Bhandary, Bose Institute, are acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

We thank Defense Research and Development Organization (DRDO), Defense Ministry, India, for their financial support [grant number: ERIP/ER/1103954/M/01/1413].