TY - JOUR
T1 - Electrostatics, Hydrogen Bonding, and Molecular Structure at Polycation and Peptide:Lipid Membrane Interfaces
AU - Dalchand, Naomi
AU - Cui, Qiang
AU - Geiger, Franz M.
N1 - Funding Information:
This work was supported by the National Science Foundation under the Center for Sustainable Nanotechnology, Grant CHE-1503408. F.M.G. acknowledges support from a Dow Chemical Company Professorship and from the Alexander von Humboldt Foundation.
Publisher Copyright:
© 2019 American Chemical Society.
PY - 2020/5/13
Y1 - 2020/5/13
N2 - Polycation and peptide-modified surfaces represent opportunities for developing potentially novel biocidal materials in a growing effort to combat bacterial resistance to traditional bactericides. It is well-known that the positive charge of these compounds is crucial to their function in biofouling prevention and as antimicrobials; however, methods for quantifying the number of positive charges on surface-bound polycations and peptides are necessary to predict, control, and optimize the design and therefore the utility of these compounds. This Spotlight on Applications reports on such an approach that combines second harmonic generation (SHG) spectroscopy, quartz crystal microbalance with dissipation monitoring (QCM-D), and atomistic simulations to obtain mechanistic insight into polycation-membrane interactions using supported lipid bilayers (SLBs) as our model system. We find that at high surface coverage, the large polycations we surveyed feature a considerably smaller percentage of ionization when compared to the smaller polycations and peptides. At these high charge densities, we suspect a pKa shift of the charged groups to lower charge-charge repulsion as well as the formation of a looplike conformation such that less monomeric units form contact-ion pairs with the bilayer. Our sum frequency generation (SFG) spectroscopy results complement our understanding of the polycation-membrane interaction. At a high density of the polycation poly(allylamine hydrochloride) (PAH), second-order spectral line shapes are consistent with the expulsion of interfacial water molecules possibly due to contact-ion pair formation between PAH and the lipid bilayer. This finding could be essential for understanding the underlying first steps of cell lysis and penetration by polycations and should be explored further.
AB - Polycation and peptide-modified surfaces represent opportunities for developing potentially novel biocidal materials in a growing effort to combat bacterial resistance to traditional bactericides. It is well-known that the positive charge of these compounds is crucial to their function in biofouling prevention and as antimicrobials; however, methods for quantifying the number of positive charges on surface-bound polycations and peptides are necessary to predict, control, and optimize the design and therefore the utility of these compounds. This Spotlight on Applications reports on such an approach that combines second harmonic generation (SHG) spectroscopy, quartz crystal microbalance with dissipation monitoring (QCM-D), and atomistic simulations to obtain mechanistic insight into polycation-membrane interactions using supported lipid bilayers (SLBs) as our model system. We find that at high surface coverage, the large polycations we surveyed feature a considerably smaller percentage of ionization when compared to the smaller polycations and peptides. At these high charge densities, we suspect a pKa shift of the charged groups to lower charge-charge repulsion as well as the formation of a looplike conformation such that less monomeric units form contact-ion pairs with the bilayer. Our sum frequency generation (SFG) spectroscopy results complement our understanding of the polycation-membrane interaction. At a high density of the polycation poly(allylamine hydrochloride) (PAH), second-order spectral line shapes are consistent with the expulsion of interfacial water molecules possibly due to contact-ion pair formation between PAH and the lipid bilayer. This finding could be essential for understanding the underlying first steps of cell lysis and penetration by polycations and should be explored further.
KW - SFG
KW - SHG
KW - atomistic simulations
KW - peptides
KW - polycation-membrane interactions
KW - surface and membrane potential
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U2 - 10.1021/acsami.9b17431
DO - 10.1021/acsami.9b17431
M3 - Article
C2 - 31889444
AN - SCOPUS:85078096564
SN - 1944-8244
VL - 12
SP - 21149
EP - 21158
JO - ACS Applied Materials and Interfaces
JF - ACS Applied Materials and Interfaces
IS - 19
ER -