Counting charges on membrane-bound peptides

McGeachy, Alicia C.; Caudill, Emily R.; Liang, Dongyue; Cui, Qiang; Pedersen, Joel A.; Geiger, Franz M.

doi:10.1039/c8sc00804c

Cited by 28 publications

(49 citation statements)

References 104 publications

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“…when, however, other components in the system exhibit a net orientation, these can also contribute to the signal, as is, for instance, the case of lipid monolayers at the air-water interface 254 . Non-resonant sHG has been used to learn about the surface potential and charge of mineral surfaces as well as membranes 80,157,[271][272][273] , has been refined using heterodyne detection 268 and has been shown, in scattering geometry, to provide information on φ 0 from the surface of particles, droplets and vesicles 267,274,275 . using sHG microscopy, the aligned water molecules have been used as reporters of surface heterogeneity and dynamics at mineral interfaces 90 , asymmetrical lipid bilayer membranes 88 and neuronal membranes 276 .…”

Section: Kelvin Probe Microscopymentioning

confidence: 99%

“…Both phenomena effectively break the symmetry in the near-interface region, leading to enhanced sFG or sHG signals 88,90,156,163,169,276,288,289 . with the use of appropriate models, the signals can be converted into surface potential 80,82,84,157,159,254,[267][268][269][270][271][272][273][274][275]290,291 . Nir, near infrared.…”

Section: Box 5 | Surface-sensitive Nonlinear Optical Techniquesmentioning

confidence: 99%

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Water at charged interfaces

et al. 2021

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The ubiquity of aqueous solutions in contact with charged surfaces and the realization that the molecular-level details of water-surface interactions often determine interfacial functions and properties relevant in many natural processes have led to intensive research. Even so, many open questions remain regarding the molecular picture of the interfacial organization and preferential alignment of water molecules, as well as the structure of water molecules and ion distributions at different charged interfaces. While water, solutes and charge are present in each of these systems, the substrate can range from living tissues to metals. This diversity in substrates has led to different communities considering each of these types of aqueous interface. In this Review, by considering water in contact with metals, oxides and biomembranes, we show the essential similarity of these disparate systems. While in each case the classical mean-field theories can explain many macroscopic and mesoscopic observations, it soon becomes apparent that such theories fail to explain phenomena for which molecular properties are relevant, such as interfacial chemical conversion. We highlight the current knowledge and limitations in our understanding and end with a view towards future opportunities in the field.

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Section: Kelvin Probe Microscopymentioning

confidence: 99%

Section: Box 5 | Surface-sensitive Nonlinear Optical Techniquesmentioning

confidence: 99%

Water at charged interfaces

et al. 2021

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“…In this scenario, binding is cooperative. 33 When n < 1, anti-cooperative behavior is observed, meaning the affinity for binding decreases with an increasing concentration of adsorbate. Alternatively, adsorption to structurally or chemically heterogeneous surfaces can also result in artificially low n values 34,35 while electrostatics and reductions in dimensionality can explain high values for n. 36 In the work discussed here, the combined Gouy-Chapman/Langmuir and the Gouy-Chapman/Hill models were used to extract the equilibrium binding constant, the free energy of adsorption, and the interfacial charge density and charge per adsorbed polycation or peptide.…”

Section: (1)mentioning

confidence: 99%

“…45 This difference leads to substantially different binding modes of Arg8 and Lys8 peptides: Arg8 inserts more deeply into the bilayer to form a "buried" conformation, interacting with the lipids with up to 6 side chains whereas Lys8 is more likely to "stand-up" and interacts with the bilayer with 1 or 2 side chains. 33 Analysis of the interfacial electrostatic potential and charge distribution from the atomistic simulations also enabled us to examine the quantitative validity of the commonly used Gouy-Chapman model for converting measured surface potential to an effective surface charge density.…”

Section: Cationic Peptides At Lipid Bilayer Membranesmentioning

confidence: 99%

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

Dalchand¹,

Cui²,

Geiger³

2019

Preprint

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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 Dalchand et al.Page 2 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.

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“…Specifically, we investigate ion-specific outcomes in second harmonic generation (SHG) spectroscopy [33][34][35] featuring, for the first time, homodyne and heterodyne-detection (HD) using the Eisenthal χ (3) method under off-resonant conditions [36][37][38][39][40][41] using a newly developed HD-SHG spectrometer. 42 When the frequency of the incident fundamental electric field, Eω, is tuned off electronic or vibrational resonances, the second harmonic electric field, E2ω, produced at the interface is described by the following model: 7,13,[42][43][44][45][46][47][48][49][50][51][52][53] Under off-resonant conditions, the second-and third-order nonlinear susceptibilities of the interface, (2) and (3) , respectively, are purely real. The factor ∆ is the wave vector mismatch describing the inverse of the coherence length of the SHG process (1.1 x 10 7 m -1 in our case), 42 and is the z-(depth) dependent electric field produced by interfacial charges and ionic screening, given by = -dΦ(z)dz, where Φ(z) is the electrostatic potential.…”

Section: Introduction While Ion-specific Interactions At Charged mentioning

confidence: 99%

Specifics About Specific Ion Adsorption from Heterodyne-Detected Second Harmonic Generation

Boamah¹,

Ohno²,

Lozier³

et al. 2019

Preprint

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<p>Ion specific outcomes at aqueous interfaces remain among the most enigmatic phenomena in interfacial chemistry. Here, charged fused silica/water interfaces have been probed by homodyne- and heterodyne-detected (HD) second harmonic generation (SHG) spectroscopy at pH 7 and pH 5.8 and for concentrations of LiCl, NaCl, NaBr, NaI, KCl, RbCl, and CsCl ranging from 10 mM to several 100 mM. For ionic strengths around 0.1 mM to 1 mM, SHG intensities increase reversibly by up to 15% compared to the condition of zero added salt because of optical phase matching and electrical double layer. For ionic strengths above 1 mM, use of any combination of cations and anions produces decreases in SHG response by as much as 50%, trending with ion softness when compared to the condition of zero added salt. Gouy-Chapman model fits to homodyned SHG intensities for the alkali halides studied here show charge densities increase significantly with decreasing cation size. HD-SHG measurements indicate diffuse layer properties probed by the SHG process are invariant with ion identity, while Stern layer properties, as reported by chi(2), are subject to ion specificity for the ions surveyed in this work in the order of chi(2)RbCl=1/2 chi(2)NaCl=1/4 chi(2)NaI. Supporting Information available upon request to the Corresponding Author.</p>

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Counting charges on membrane-bound peptides

Cited by 28 publications

References 104 publications

Water at charged interfaces

Water at charged interfaces

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

Specifics About Specific Ion Adsorption from Heterodyne-Detected Second Harmonic Generation

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