Self-Assembled Nanostructures of Peptide Amphiphiles

Charge Regulation by Size Regulation

Gervasio Zaldivar, Sridhar Vemulapalli, Venkatareddy Udumula, Martin Conda Sheridan, Mario Tagliazucchi

Research output: Contribution to journalArticle

Abstract

Self-assembled nanostructures of peptide amphiphiles (PAs) with molecular structures C16K2 and C16K3 (where C indicates the number of carbon atoms in the alkyl chain and K is the lysine in the head group) were studied by a combination of theoretical modeling, transmission electron and atomic force microscopes, and acid-base titration experiments. The supramolecular morphology of the PAs (micelles, fibers, or lamellas) was dependent on the pH and ionic strength of the solution. Theoretical modeling was performed using a molecular theory that allows determining the equilibrium morphology, the size, and the charge of the soft nanoassemblies as a function of the molecular structure of the PA, and the pH and salt concentration of the solution. Theoretical predictions showed good agreement with experimental data for the pH-dependent morphology and size of the nanoassemblies and their apparent pKa's. Two interesting effects associated with charge regulation mechanisms were found: first, ionic strength plays a dual role in the modulation of the electrostatic interactions in the system, which leads to complex dependencies of the aggregation numbers with salt concentration; second, the aggregation number of the nanostructures decreases upon increasing the charge per PA. The second mechanism, charge regulation by size regulation, tunes the net charge of the assemblies to decrease the electrostatic repulsions. A remarkable consequence of this behavior is that adding an extra lysine residue to the charged region of the PAs can lead to an unexpected decrease in the total charge of the micelles.

Original languageEnglish (US)
Pages (from-to)17606-17615
Number of pages10
JournalJournal of Physical Chemistry C
Volume123
Issue number28
DOIs
StatePublished - Jun 24 2019

Fingerprint

Amphiphiles
Peptides
peptides
Nanostructures
lysine
Micelles
Ionic strength
Molecular structure
Lysine
micelles
molecular structure
Agglomeration
Salts
electrostatics
salts
molecular theory
lamella
Coulomb interactions
Titration
titration

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

Cite this

Self-Assembled Nanostructures of Peptide Amphiphiles : Charge Regulation by Size Regulation. / Zaldivar, Gervasio; Vemulapalli, Sridhar; Udumula, Venkatareddy; Conda Sheridan, Martin; Tagliazucchi, Mario.

In: Journal of Physical Chemistry C, Vol. 123, No. 28, 24.06.2019, p. 17606-17615.

Research output: Contribution to journalArticle

Zaldivar, Gervasio ; Vemulapalli, Sridhar ; Udumula, Venkatareddy ; Conda Sheridan, Martin ; Tagliazucchi, Mario. / Self-Assembled Nanostructures of Peptide Amphiphiles : Charge Regulation by Size Regulation. In: Journal of Physical Chemistry C. 2019 ; Vol. 123, No. 28. pp. 17606-17615.
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