scholarly journals Electrostatics, Hydrogen Bonding, and Molecular Structure at Polycation and Peptide:Lipid Membrane Interfaces

2019 ◽  
Author(s):  
Naomi Dalchand ◽  
Qiang Cui ◽  
Franz Geiger
Keyword(s):  
Lipid Bilayers ◽  
Bacterial Resistance ◽  
Second Harmonic ◽  
High Surface ◽  
Ion Pairs ◽  
Supported Lipid Bilayers ◽  
Sum Frequency ◽  
Charge Densities ◽  
Line Shapes ◽  
Membrane Interfaces

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 in order 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 loop-like 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.<br>

scholarly journals Electrostatics, Hydrogen Bonding, and Molecular Structure at Polycation and Peptide:Lipid Membrane Interfaces

2019 ◽  
Author(s):  
Naomi Dalchand ◽  
Qiang Cui ◽  
Franz Geiger
Keyword(s):  
Lipid Bilayers ◽  
Bacterial Resistance ◽  
Second Harmonic ◽  
High Surface ◽  
Ion Pairs ◽  
Supported Lipid Bilayers ◽  
Sum Frequency ◽  
Charge Densities ◽  
Line Shapes ◽  
Membrane Interfaces

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 in order 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 loop-like 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.<br>

scholarly journals Coexistence of long and short DNA constructs within adhesion plaques

2020 ◽  
Author(s):  
Long Li ◽  
Mohammad Arif Kamal ◽  
Henning Stumpf ◽  
Franck Thibaudau ◽  
Kheya Sengupta ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Optical Resolution ◽  
Simultaneous Action ◽  
Supported Lipid Bilayers ◽  
Physical Mechanisms ◽  
Domain Structures ◽  
Membrane Interfaces ◽  
A Cell ◽  
Physical Effects ◽  
Relative Differences

Adhesion domains forming at the membrane interfaces between two cells or a cell and the ex-tracellular matrix commonly involve multiple proteins bridges. However, the physical mechanisms governing the domain structures are not yet fully resolved. Here we present a joint experimental and theoretical study of a mimetic model-system, based on giant unilammelar vesicles interacting with supported lipid bilayers, with which the underlying physical effects can be clearly identified. In our case, adhesion is induced by simultaneous action of DNA linkers with two different lengths. We study the organization of bridges into domains as a function of relative fraction of long and short DNA constructs. Irrespective of the composition, we systematically find adhesion domains with coexisting DNA bridge types, despite their relative differences in length of 9 nm. However, at short length scales, below the optical resolution of the microscope, simulations suggest the formation of nanodomains by the minority fraction. The nano-aggregation is more significant for long bridges, which are also more stable, even though the enthalpy of membrane insertion is the same for both species.

scholarly journals Beyond the Gouy-Chapman Model with Heterodyne-Detected Second Harmonic Generation

2019 ◽  
Author(s):  
Franz Geiger ◽  
Paul E. Ohno ◽  
HanByul Chang ◽  
Austin P. Spencer ◽  
Mavis D. Boamah ◽  
...  
Keyword(s):  
Second Harmonic Generation ◽  
Lipid Bilayers ◽  
Harmonic Generation ◽  
Rayleigh Scattering ◽  
Second Harmonic ◽  
Mean Field ◽  
Recent Model ◽  
Supported Lipid Bilayers ◽  
New Instrument ◽  
Interfacial Potential

<p>We report ionic strength-dependent phase shifts in second harmonic generation (SHG) signals from charged interfaces that verify a recent model in which dispersion between the fundamental and second harmonic beams modulates observed signal intensities. We show how phase information can be used to unambiguously separate the chi(2) and interfacial potential-dependent chi(3) terms that contribute to the total signal and provide a path to test primitive ion models and mean field theories for the electrical double layer with experiments to which theory must conform. Finally, we demonstrate the new method on supported lipid bilayers and comment on the ability of our new instrument to identify hyper-Rayleigh scattering contributions to common homodyne SHG measurements in reflection geometries.</p>

On Electronic and Charge Interference in Second Harmonic Generation Responses from Gold Metal Nanoparticles at Supported Lipid Bilayers

2016 ◽  
Vol 120 (37) ◽  
pp. 20659-20667 ◽  
Author(s):  
Julianne M. Troiano ◽  
Thomas R. Kuech ◽  
Ariane M. Vartanian ◽  
Marco D. Torelli ◽  
Akash Sen ◽  
...  
Keyword(s):  
Second Harmonic Generation ◽  
Metal Nanoparticles ◽  
Lipid Bilayers ◽  
Harmonic Generation ◽  
Second Harmonic ◽  
Supported Lipid Bilayers ◽  
Gold Metal

scholarly journals Perturbation of Hydrogen Bonding Networks over Supported Lipid Bilayers by Poly (Allylamine Hydrochloride)

2019 ◽  
Author(s):  
Naomi Dalchand ◽  
Merve Dogangun ◽  
Paul E. Ohno ◽  
Emily Ma ◽  
Alex Martinson ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Electrostatic Interactions ◽  
Supported Lipid Bilayers ◽  
Water Molecules ◽  
Interfacial Water ◽  
Sum Frequency ◽  
Biochemical Processes ◽  
Zwitterionic Lipids ◽  
Allylamine Hydrochloride

<div><div><div><p>Water is vital to many biochemical processes and is necessary for driving many fundamental interactions of cell membranes with their external environments, yet it is difficult to probe the membrane/water interface directly and without the use of external labels. Here, we employ vibrational sum frequency generation (SFG) spectroscopy to understand the role of interfacial water molecules above bilayers formed from zwitterionic (phosphatidylcholine, PC) and anionic (phosphatidylglycerol, PG, and phosphatidylserine, PS) lipids as they are exposed to the common polycation poly (allylamine hydrochloride) (PAH) in 100 mM NaCl. We show that as the concentration of PAH is increased, the interfacial water molecules are irreversibly displaced and find that it requires 10 times more PAH to displace interfacial water molecules from membranes formed from purely zwitterionic lipids when compared to membranes that contain the anionic PG and PS lipids. This outcome is likely due to difference in (1) the energy with which water molecules are bound to the lipid headgroups, (2) the number of water molecules bound to the headgroups, which is related to the headgroup area, and (3) the electrostatic interactions between the PAH molecules and the negatively charged lipids that are favored when compared to the zwitterionic lipid headgroups. The findings presented here contribute to establishing causal relationships in nanotoxicology and to understanding, controlling, and predicting the initial steps that lead to the lysis of cells exposed to membrane disrupting polycations, or to transfection.</p></div></div></div>

scholarly journals Hydrogen Bond Networks Near Supported Lipid Bilayers from Vibrational Sum Frequency Generation Experiments and Atomistic Simulations

2018 ◽  
Author(s):  
Merve Dogangun ◽  
Paul E. Ohno ◽  
Dongyue Liang ◽  
Alicia C. McGeachy ◽  
Ariana Gray Be ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Lipid Bilayers ◽  
Sum Frequency Generation ◽  
Atomistic Simulations ◽  
Supported Lipid Bilayers ◽  
Water Molecules ◽  
Specific Interactions ◽  
Sum Frequency ◽  
Hydrogen Bond Networks ◽  
Frequency Generation

<div> <div> <p>We report vibrational sum frequency generation (SFG) spectra in which the C–H stretches of lipid alkyl tails in fully hydrogenated single- and dual-component supported lipid bilayers are detected along with the O–H stretching continuum above the bilayer. As the salt concentration is increased from ~10 μM to 0.1 M, the SFG intensities in the O–H stretching region decrease by a factor of 2, consistent with significant absorptive-dispersive mixing between χ(2) and χ(3) contributions to the SFG signal generation process from charged interfaces. A method for estimating the surface potential from the second-order spectral lineshapes (in the OH stretching region) is presented and discussed in the context of choosing truly zero-potential reference states. Aided by atomistic simulations, we find that the strength and orientation distribution of the hydrogen bonds over the purely zwitterionic bilayers are largely invariant between sub-micromolar and hundreds of millimolar concentrations. However, specific interactions between water molecules and lipid headgroups are observed upon replacing phosphocholine (PC) lipids with negatively charged phosphoglycerol (PG) lipids, which coincides with SFG signal intensity reductions in the 3100 cm-1 to 3200 cm-1 frequency region. The atomistic simulations show that this outcome is consistent with a small, albeit statistically significant, decrease in the number of water molecules adjacent to both the lipid phosphate and choline moieties per unit area, supporting the SFG observations. Ultimately, the ability to probe hydrogen-bond networks over lipid bilayers holds the promise of opening paths for understanding, controlling, and predicting specific and non-specific interactions between membranes and ions, small molecules, peptides, polycations, proteins, and coated and uncoated nanomaterials.<br></p></div></div>

scholarly journals Hydrogen Bond Networks Near Supported Lipid Bilayers from Vibrational Sum Frequency Generation Experiments and Atomistic Simulations

2018 ◽  
Author(s):  
Merve Dogangun ◽  
Paul E. Ohno ◽  
Dongyue Liang ◽  
Alicia C. McGeachy ◽  
Ariana Gray Be ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Lipid Bilayers ◽  
Sum Frequency Generation ◽  
Atomistic Simulations ◽  
Supported Lipid Bilayers ◽  
Water Molecules ◽  
Specific Interactions ◽  
Sum Frequency ◽  
Hydrogen Bond Networks ◽  
Frequency Generation

<div> <div> <p>We report vibrational sum frequency generation (SFG) spectra in which the C–H stretches of lipid alkyl tails in fully hydrogenated single- and dual-component supported lipid bilayers are detected along with the O–H stretching continuum above the bilayer. As the salt concentration is increased from ~10 μM to 0.1 M, the SFG intensities in the O–H stretching region decrease by a factor of 2, consistent with significant absorptive-dispersive mixing between χ(2) and χ(3) contributions to the SFG signal generation process from charged interfaces. A method for estimating the surface potential from the second-order spectral lineshapes (in the OH stretching region) is presented and discussed in the context of choosing truly zero-potential reference states. Aided by atomistic simulations, we find that the strength and orientation distribution of the hydrogen bonds over the purely zwitterionic bilayers are largely invariant between sub-micromolar and hundreds of millimolar concentrations. However, specific interactions between water molecules and lipid headgroups are observed upon replacing phosphocholine (PC) lipids with negatively charged phosphoglycerol (PG) lipids, which coincides with SFG signal intensity reductions in the 3100 cm-1 to 3200 cm-1 frequency region. The atomistic simulations show that this outcome is consistent with a small, albeit statistically significant, decrease in the number of water molecules adjacent to both the lipid phosphate and choline moieties per unit area, supporting the SFG observations. Ultimately, the ability to probe hydrogen-bond networks over lipid bilayers holds the promise of opening paths for understanding, controlling, and predicting specific and non-specific interactions between membranes and ions, small molecules, peptides, polycations, proteins, and coated and uncoated nanomaterials.<br></p></div></div>

scholarly journals Hydrogen Bond Networks Near Supported Lipid Bilayers from Vibrational Sum Frequency Generation Experiments and Atomistic Simulations

2018 ◽  
Author(s):  
Merve Dogangun ◽  
Paul E. Ohno ◽  
Dongyue Liang ◽  
Alicia C. McGeachy ◽  
Ariana Gray Be ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Lipid Bilayers ◽  
Sum Frequency Generation ◽  
Atomistic Simulations ◽  
Supported Lipid Bilayers ◽  
Water Molecules ◽  
Specific Interactions ◽  
Sum Frequency ◽  
Hydrogen Bond Networks ◽  
Frequency Generation

<div> <div> <div> <p>We report vibrational sum frequency generation (SFG) spectra in which the C–H stretches of lipid alkyl tails in fully hydrogenated single- and dual-component supported lipid bilayers are detected along with the O–H stretching continuum above the bilayer. As the salt concentration is increased from ~10 μM to 0.1 M, the SFG intensities in the O–H stretching region decrease by a factor of 2, consistent with significant absorptive-dispersive mixing between χ(2) and χ(3) contributions to the SFG signal generation process from charged interfaces. A method for estimating the surface potential from the second-order spectral lineshapes (in the OH stretching region) is presented and discussed in the context of choosing truly zero-potential reference states. Aided by atomistic simulations, we find that the strength and orientation distribution of the hydrogen bonds over the purely zwitterionic bilayers are largely invariant between sub-micromolar and hundreds of millimolar concentrations. However, specific interactions between water molecules and lipid headgroups are observed upon replacing phosphocholine (PC) lipids with negatively charged phosphoglycerol (PG) lipids, which coincides with SFG signal intensity reductions in the 3100 cm-1 to 3200 cm-1 frequency region. The atomistic simulations show that this outcome is consistent with a small, albeit statistically significant, decrease in the number of water molecules adjacent to both the lipid phosphate and choline moieties per unit area, supporting the SFG observations. Ultimately, the ability to probe hydrogen-bond networks over lipid bilayers holds the promise of opening paths for understanding, controlling, and predicting specific and non-specific interactions between membranes and ions, small molecules, peptides, polycations, proteins, and coated and uncoated nanomaterials. Pre-edited version, 14 pages main text, 5 Figures, 1 Table, 29 pages Supporting Information available upon request.</p></div></div></div>

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