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Title: Electrostatic Control of Polymorphism in Charged Amphiphile Assemblies

Abstract

Stimuli-induced structural transformations of molecular assemblies in aqueous solutions are integral to nanotechnological applications and biological processes. In particular, pH responsive amphiphiles as well as proteins with various degrees of ionization can reconfigure in response to pH variations. Here, we use in situ small and wide-angle X-ray scattering (SAXS/WAXS), transmission electron microscopy (TEM), and Monte Carlo simulations to show how charge regulation via pH induces morphological changes in the assembly of a positively charged peptide amphiphile (PA). Monte Carlo simulations and pH titration measurements reveal that ionic correlations in the PA assemblies shift the ionizable amine pK ~ 8 from pK ~ 10 in the lysine headgroup. SAXS and TEM show that with increasing pH, the assembly undergoes spherical micelle to cylindrical nanofiber to planar bilayer transitions. SAXS/WAXS reveal that the bilayer leaflets are interdigitated with the tilted PA lipid tails crystallized on a rectangular lattice. The details of the molecular packing in the membrane result from interplay between steric and van der Waals interactions. We speculate that this packing motif is a general feature of bilayers comprised of amphiphilic lipids with large ionic headgroups. Altogether, our studies correlate the molecular charge and the morphology for a pH-responsive PA systemmore » and provide insights into the Å-scale molecular packing in such assemblies.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1]; ORCiD logo [2];  [1]; ORCiD logo [1]
  1. Northwestern Univ., Evanston, IL (United States)
  2. Northwestern Univ., Evanston, IL (United States); Northwestern Univ., Chicago, IL (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF)
OSTI Identifier:
1352225
Grant/Contract Number:  
AC02-06CH11357; NNCI-1542205; DMR-1121262; FG02-08ER46539; DMR-1006713
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry
Additional Journal Information:
Journal Volume: 121; Journal Issue: 7; Journal ID: ISSN 1520-6106
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
ENGLISH
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; vesicles; peptides and proteins; monomers; X-ray scattering; micelles

Citation Formats

Gao, Changrui, Li, Honghao, Li, Yue, Kewalramani, Sumit, Palmer, Liam C., Dravid, Vinayak P., Stupp, Samuel I., Olvera de la Cruz, Monica, and Bedzyk, Michael J. Electrostatic Control of Polymorphism in Charged Amphiphile Assemblies. United States: N. p., 2017. Web. doi:10.1021/acs.jpcb.6b11602.
Gao, Changrui, Li, Honghao, Li, Yue, Kewalramani, Sumit, Palmer, Liam C., Dravid, Vinayak P., Stupp, Samuel I., Olvera de la Cruz, Monica, & Bedzyk, Michael J. Electrostatic Control of Polymorphism in Charged Amphiphile Assemblies. United States. https://doi.org/10.1021/acs.jpcb.6b11602
Gao, Changrui, Li, Honghao, Li, Yue, Kewalramani, Sumit, Palmer, Liam C., Dravid, Vinayak P., Stupp, Samuel I., Olvera de la Cruz, Monica, and Bedzyk, Michael J. Wed . "Electrostatic Control of Polymorphism in Charged Amphiphile Assemblies". United States. https://doi.org/10.1021/acs.jpcb.6b11602. https://www.osti.gov/servlets/purl/1352225.
@article{osti_1352225,
title = {Electrostatic Control of Polymorphism in Charged Amphiphile Assemblies},
author = {Gao, Changrui and Li, Honghao and Li, Yue and Kewalramani, Sumit and Palmer, Liam C. and Dravid, Vinayak P. and Stupp, Samuel I. and Olvera de la Cruz, Monica and Bedzyk, Michael J.},
abstractNote = {Stimuli-induced structural transformations of molecular assemblies in aqueous solutions are integral to nanotechnological applications and biological processes. In particular, pH responsive amphiphiles as well as proteins with various degrees of ionization can reconfigure in response to pH variations. Here, we use in situ small and wide-angle X-ray scattering (SAXS/WAXS), transmission electron microscopy (TEM), and Monte Carlo simulations to show how charge regulation via pH induces morphological changes in the assembly of a positively charged peptide amphiphile (PA). Monte Carlo simulations and pH titration measurements reveal that ionic correlations in the PA assemblies shift the ionizable amine pK ~ 8 from pK ~ 10 in the lysine headgroup. SAXS and TEM show that with increasing pH, the assembly undergoes spherical micelle to cylindrical nanofiber to planar bilayer transitions. SAXS/WAXS reveal that the bilayer leaflets are interdigitated with the tilted PA lipid tails crystallized on a rectangular lattice. The details of the molecular packing in the membrane result from interplay between steric and van der Waals interactions. We speculate that this packing motif is a general feature of bilayers comprised of amphiphilic lipids with large ionic headgroups. Altogether, our studies correlate the molecular charge and the morphology for a pH-responsive PA system and provide insights into the Å-scale molecular packing in such assemblies.},
doi = {10.1021/acs.jpcb.6b11602},
url = {https://www.osti.gov/biblio/1352225}, journal = {Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry},
issn = {1520-6106},
number = 7,
volume = 121,
place = {United States},
year = {2017},
month = {2}
}

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