Interfacial water and ion distribution determine <i>ζ</i> potential and binding affinity of nanoparticles to biomolecules

Liang, Dongyue; Dahal, Udaya; Zhang, Yongqian Kelly; Lochbaum, Christian A.; Ray, Dhiman; Hamers, Robert J.; Pedersen, Joel A.; Cui, Qiang

doi:10.1039/d0nr03792c

Cited by 15 publications

(27 citation statements)

References 104 publications

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“…This is qualitatively consistent with findings from previous simulations of functionalized nanoparticles − and further supports the role of hydrophobic packing that promotes asymmetric distribution of long surface ligands. Due to the charged nature of quaternary amine ligands, however, the degree of “ligand bundling” is minimal compared to previous studies of nanoparticles functionalized with charge-neutral ligands. , The difference between the current explicit solvent simulations and previous implicit solvent simulations further highlights the importance of treating solvent and ions carefully at the nanoparticle/solvent interface. ,− The diverse environment experienced by the head groups of long ligands due to clustering is qualitatively consistent with the significant difference between T 2 and T 2 * observed experimentally …”

Section: Discussionsupporting

confidence: 63%

“…This lower level of counter ion compensation leads to higher peak values for the apparent charge plots for C11Q65 and MTAB65, which explain their higher electrophoretic mobility values than C4Q65. This analysis highlights that the conformational characteristics of surface ligands can modify the electrostatic properties of the nanoparticle/solvent interface and therefore are expected to have an impact on the interactions between the nanoparticle and other (bio)molecules …”

Section: Results and Discussionmentioning

confidence: 99%

“…For the drift velocity simulations, the system setups are identical to the equilibrium MD simulations, unless specified otherwise. To compromise between convergence and preservation of the electrical double layer around the charged nanoparticle, an external electric field of 0.05 kcal·mol –1 ·Å –1 ·e –1 is applied (1 kcal·mol –1 ·Å –1 ·e –1 = 4.3 × 10 6 V/cm), similar to our recent work . A comparison to Nosé–Hoover thermostat shows that a damping coefficient smaller than 0.02 ps –1 is necessary for obtaining the correct magnitude of drift velocity, and a value of 0.02 ps –1 is applied in this work.…”

Section: Methodsmentioning

confidence: 94%

“…Experimentally, electrophoresis measurement is widely applied to characterize the electrostatic properties of the nanoparticles. ,− Along this line, we apply the drift velocity method ,, to estimate the electrophoretic mobilities of the nanoparticles; we chose to focus on mobility rather than electrostatic potential to avoid the difficulty of defining the slipping plane for the nanoparticles with long ligands such as MTAB, which leads to highly heterogeneous surfaces (vide infra). Under an external electric field, the mobility is computed as where v is the drift velocity of the nanoparticle and E is the strength of the external electric field.…”

Section: Methodsmentioning

confidence: 99%

“…As a follow-up study, we conduct explicit solvent molecular dynamics simulations for the similar gold nanoparticles and analyze both the conformational distribution and dynamics of surface ligands; an explicit comparison to the NMR relaxation measurement is made by computing T 2 via a model-free approach well established in the biophysics community. − To probe the effect of surface curvature, we compare the results for a small gold nanoparticle with those for a gold slab; since the packing effect discussed in previous work − is expected to be sensitive to chain length, we also compare several ligands with hydrophobic segments of variable lengths. Finally, we explore how the conformational characteristics of surface ligands impact electrostatic properties of nanoparticles by computing their mobilities via nonequilibrium molecular dynamics simulations; the results highlight that conformations of surface ligands are crucial to the surface potential of nanoparticles and therefore their interaction with other molecules …”

Section: Introductionmentioning

confidence: 99%

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Ligand Length and Surface Curvature Modulate Nanoparticle Surface Heterogeneity and Electrostatics

Liang

Dahal

et al. 2020

J. Phys. Chem. C

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Motivated by the recent nuclear magnetic resonance (NMR) analysis of functionalized gold nanoparticles (J. Am. Chem. Soc.201914143164327), we conduct explicit solvent atomistic simulations to characterize the conformational distribution and dynamics of surface ligands on a small gold nanoparticle of 2 nm diameter. Several quaternary alkyl amines are studied to probe the effect of chain length, and a gold slab system is studied to probe the effect of surface curvature. The simulations observe a higher degree of spatial heterogeneity as the ligand length increases, leading to a higher degree of local clustering of longer ligands. Due to the charged nature of the head groups, however, the degree of “ligand bundling” is minimal compared to previous studies of nanoparticles functionalized with charge-neutral ligands. Due to the considerable flexibility of long ligands, their local clustering is not long lived and rearranges at the time scale of 1–10 ns, suggesting that rearrangements of ligand conformation are unlikely to represent the kinetic bottleneck for nanoparticle–(bio)molecular interactions. The head group methyl proton T 2 relaxation time is computed using a model-free approach, and the results are in general agreement with experimental data, providing essential validation of the nanoparticle model and the simulation protocol. Analysis of contributions to the computed T 2 relaxation time suggests that to characterize the time scale of surface ligand dynamics, such measurements should focus on nanoparticles whose hydrodynamic radii are no larger than 3 nm; for larger particles, surface features such as ligand flexibility and heterogeneity can be qualitatively reflected through order parameters and T 2/T 2 *. Nonequilibrium molecular dynamics simulations show that conformational features of the ligands impact the electrostatic properties of the nanoparticle, which suggests that nanoparticle/(bio)molecular interactions can be modulated by perturbing the conformational ensemble of surface ligands.

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