Title: Electrostatic shape control of a charged molecular membrane from ribbon to scroll

Abstract

Bilayers of amphiphiles can organize into spherical vesicles, nanotubes, planar, undulating, and helical nanoribbons, and scroll-like cochleates. These bilayer-related architectures interconvert under suitable conditions. Here, a charged, chiral amphiphile (palmitoyl-lysine, C₁₆-K₁) is used to elucidate the pathway for planar nanoribbon to cochleate transition induced by salt (NaCl) concentration. In situ small- and wide-angle X-ray scattering (SAXS/WAXS), atomic force and cryogenic transmission electron microscopies (AFM and cryo-TEM) tracked these transformations over angstrom to micrometer length scales. AFM reveals that the large length (L) to width (W) ratio nanoribbons (L/W > 10) convert to sheets (L/W → 1) before rolling into cochleates. Furthermore, a theoretical model based on electrostatic and surface energies shows that the nanoribbons convert to sheets via a first-order transition, at a critical Debye length, with 2 shallow minima of the order of thermal energy at L/W >> 1 and at L/W = 1. SAXS shows that interbilayer spacing (D) in the cochleates scales linearly with the Debye length, and ranges from 13 to 35 nm for NaCl concentrations from 100 to 5 mM. Theoretical arguments that include electrostatic and elastic energies explain the membrane rolling and the bilayer separation–Debye length relationship. These models suggest that the salt-induced ribbonmore » to cochleate transition should be common to all charged bilayers possessing an intrinsic curvature, which in the present case originates from molecular chirality. Our studies show how electrostatic interactions can be tuned to attain and control cochleate structures, which have potential for encapsulating, and releasing macromolecules in a size-selective manner.« less

Authors:

Gao, Changrui; Kewalramani, Sumit; Valencia, Dulce Maria; Li, Honghao; McCourt, Joseph M.; Olvera de la Cruz, Monica ;

• Search DOE PAGES for author "Olvera de la Cruz, Monica"
• Search DOE PAGES for ORCID "0000-0002-9802-3627"

Bedzyk, Michael J.

• Search DOE PAGES for author "Bedzyk, Michael J."
• Search DOE PAGES for ORCID "0000-0002-1026-4558"

Publication Date:

Mon Oct 14 00:00:00 EDT 2019

Research Org.:

Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1570475

Alternate Identifier(s):

OSTI ID: 1576003

Grant/Contract Number:  

FG02-08ER46539; AC02-06CH11357

Resource Type:

Published Article

Journal Name:

Proceedings of the National Academy of Sciences of the United States of America

Additional Journal Information:

Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Volume: 116 Journal Issue: 44; Journal ID: ISSN 0027-8424

Publisher:

National Academy of Sciences

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; bilayer assembly; electrostatics; nanoribbon; cochleate