Grazing Incidence X-ray Diffraction Studies of Lipid-Peptide Mixed Monolayers during Shear Flow

Pradip K Bera; Ajoy K Kandar; Rema Krishnaswamy; Philippe Fontaine; Marianne Impéror-Clerc; Brigitte Pansu; Doru Constantin; Santanu Maiti; Milan K Sanyal; A K Sood

doi:10.1021/acsomega.0c01261

Grazing Incidence X-ray Diffraction Studies of Lipid-Peptide Mixed Monolayers during Shear Flow

ACS Omega. 2020 Jun 9;5(24):14555-14563. doi: 10.1021/acsomega.0c01261. eCollection 2020 Jun 23.

Authors

Pradip K Bera¹, Ajoy K Kandar^{1

2}, Rema Krishnaswamy^{1

3}, Philippe Fontaine⁴, Marianne Impéror-Clerc⁵, Brigitte Pansu⁵, Doru Constantin⁵, Santanu Maiti⁶, Milan K Sanyal⁶, A K Sood¹

Affiliations

¹ Department of Physics, Indian Institute of Science, Bangalore 560012, India.
² Soft Condensed Matter, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 1, 3584 CC Utrecht, The Netherlands.
³ School of Liberal Studies, Azim Premji University, Bangalore 560100, India.
⁴ SOLEIL Synchrotron, L'Orme des Merisiers, Saint-Aubin, BP48, 91192 Gif-sur-Yvette Cedex, France.
⁵ Laboratoire de Physique des Solides, Unité Mixte de Recherche 8502 Centre National de la Recherche Scientifique, Université Paris-Sud 11, 91405 Orsay Cedex, France.
⁶ Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064, India.

Abstract

Grazing incidence X-ray diffraction (GIXD) studies of monolayers of biomolecules at an air-water interface give quantitative information of in-plane packing, coherence length of crystalline domains, etc. Rheo-GIXD measurements can reveal quantitative changes in the nanocrystalline domains of a monolayer under shear. Here, we report GIXD studies of monolayers of alamethicin peptide, DPPC lipid, and their mixtures at an air-water interface under steady shear stress. The alamethicin monolayer and the mixed monolayer show a flow jamming transition. On the other hand, the pure 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayer under constant stress flows steadily with a notable enhancement of the area/molecule and coherence lengths, suggesting the fusion of nanocrystallites during flow. The DPPC-alamethicin mixed monolayer shows no significant change in the area/DPPC molecule, but the coherence lengths of the individual phases (DPPC and alamethicin) increase, suggesting that the crystallites of individual phases grow bigger by merging of domains. More phase separation occurs in the system during flow. Our results show that rheo-GIXD has the potential to explore in situ molecular structural changes under rheological conditions for a diverse range of confined biomolecules at interfaces.