1
|
Higuchi H, Ikeda-Fukazawa T. Interactions between Water and a Hydrophobic Polymer. J Phys Chem B 2024; 128:1927-1935. [PMID: 38369787 DOI: 10.1021/acs.jpcb.3c07440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
To investigate the mechanisms of interactions between a hydrophobic polymer and water, molecular dynamics calculations and Raman spectroscopic measurements of cis-1,4-polyisoprene (PI)-water systems were performed. The results show that PI in water undergoes a coil-globule transition at around 248 K. The transition is attributed to changes in the density and diffusivity of water. The volume expansion of the supercooled liquid water induces the coil structure of PI. The phase separation of PI from water with an increase in the self-diffusion coefficient of water molecules results in the globule structure of PI. The self-diffusion coefficient of free water with PI is larger than that of pure water because PI has an effect to decrease the hydrogen-bonding strength of water. The result suggests that the effects of the coexisting water are important factors governing the physical and chemical properties of hydrophobic polymers.
Collapse
Affiliation(s)
- Hikaru Higuchi
- Department of Applied Chemistry, Meiji University, Kawasaki 214-8571, Japan
| | | |
Collapse
|
2
|
Naito H, Sumi T, Koga K. How do water-mediated interactions and osmotic second virial coefficients vary with particle size? Faraday Discuss 2024; 249:440-452. [PMID: 37791511 DOI: 10.1039/d3fd00104k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Abstract
We examine quantitatively the solute-size dependences of the effective interactions between nonpolar solutes in water and in a simple liquid. The potential w(r) of mean force and the osmotic second virial coefficients B are calculated with high accuracy from molecular dynamics simulations. As the solute diameter increases from methane's to C60's with the solute-solute and solute-solvent attractive interaction parameters fixed to those for the methane-methane and methane-water interactions, the first minimum of w(r) lowers from -1.1 to -4.7 in units of the thermal energy kT. Correspondingly, the magnitude of B (<0) increases proportional to σα with some power close to 6 or 7, which reinforces the solute-size dependence of B found earlier for a smaller range of σ [H. Naito, R. Okamoto, T. Sumi and K. Koga, J. Chem. Phys., 2022, 156, 221104]. We also demonstrate that the strength of the attractive interactions between solute and solvent molecules can qualitatively change the characteristics of the effective pair interaction between solute particles, both in water and in a simple liquid. If the solute-solvent attractive force is set to be weaker (stronger) than a threshold, the effective interaction becomes increasingly attractive (repulsive) with increasing solute size.
Collapse
Affiliation(s)
- Hidefumi Naito
- Department of Chemistry, Faculty of Science, Okayama University, Okayama 700-8530, Japan.
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Tomonari Sumi
- Department of Chemistry, Faculty of Science, Okayama University, Okayama 700-8530, Japan.
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Kenichiro Koga
- Department of Chemistry, Faculty of Science, Okayama University, Okayama 700-8530, Japan.
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| |
Collapse
|
3
|
Hosseni A, Ashbaugh HS. Osmotic Force Balance Evaluation of Aqueous Electrolyte Osmotic Pressures and Chemical Potentials. J Chem Theory Comput 2023; 19:8826-8838. [PMID: 37978934 PMCID: PMC10720338 DOI: 10.1021/acs.jctc.3c00982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 10/26/2023] [Accepted: 10/27/2023] [Indexed: 11/19/2023]
Abstract
Concentrated aqueous salt solutions are ubiquitous in problems of biological and environmental relevance. The development of accurate force fields that capture the interactions between dissolved species in solution is crucial to simulating these systems to gain molecular insights into the underlying processes under saline conditions. The osmotic pressure is a relatively simple thermodynamic property connecting the experimental and simulation measurements of the associative properties of the ions in solution. Milner [C. Gillespie and S. T. Milner, Soft Matter, 16, 9816 (2020)] proposed a simulation approach to evaluate the osmotic pressures of salts in solution by applying a restraint potential to the ions alone in solution and determining the resulting pressure required to balance that potential, referred to here as the osmotic force balance. Here, we expand Milner's approach, demonstrating that the chemical potentials of the salts in solution as a function of concentration can be fitted to the concentration profiles determined from simulation, additionally providing an analytical expression for the osmotic pressure. This approach is used to determine the osmotic pressures of 15 alkali halide salts in water from simulations. The cross interactions between cations and anions in solution are subsequently optimized to capture their experimental osmotic pressures.
Collapse
Affiliation(s)
- Alireza Hosseni
- Department of Chemical and
Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Henry S. Ashbaugh
- Department of Chemical and
Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| |
Collapse
|
4
|
Wang Y, Allen O, Collins E, Ashbaugh HS. Methane at the gas/water interface: Molecular simulations of surface adsorption and second surface virial coefficients. Colloids Surf A Physicochem Eng Asp 2022. [DOI: 10.1016/j.colsurfa.2022.129725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
|
5
|
Uttinger MJ, Hundschell CS, Lautenbach V, Pusara S, Bäther S, Heyn TR, Keppler JK, Wenzel W, Walter J, Kozlowska M, Wagemans AM, Peukert W. Determination of specific and non-specific protein-protein interactions for beta-lactoglobulin by analytical ultracentrifugation and membrane osmometry experiments. SOFT MATTER 2022; 18:6739-6756. [PMID: 36040122 DOI: 10.1039/d2sm00908k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Protein-protein interactions are essential for the understanding of biological processes. Specific protein aggregation is an important aspect for many biological systems. In particular, electrostatic interactions play the key role for protein-protein interactions, as many amino acids have pH-dependent charge states. Moreover, protein dissociation is directly related to the solution pH, ionic strength, temperature and protein concentration. The subtle interplay between different specific and non-specific interactions is demonstrated for beta-lactoglobulin (BLG) with a focus on low salt concentrations, thus mimicking technically relevant processing conditions. BLG is a well-characterized model system, proven to attain its monomer-dimer equilibrium strongly dependent upon the pH of the solution. In this manuscript, we present a unique combination of analytical ultracentrifugation and membrane osmometry experiments, which quantifies specific and non-specific interactions, i.e. in terms of the dimer dissociation constants and the second osmotic virial coefficient, at pH 3 and 7 and sodium chloride concentrations of 10 mM and 100 mM. This provides direct insight to protein-protein interactions for a system with a concentration-dependent monomer-dimer equilibrium. Moreover, using a coarse-grained extended DLVO model in combination with molecular dynamics simulations, we quantify non-specific monomer-monomer, monomer-dimer and dimer-dimer interactions as well as the binding free energy of BLG dimerization from theoretical calculations. The experimentally determined interactions are shown to be mainly governed by electrostatic interactions and further agree with free energy calculations. Our experimental protocol aims to determine non-specific and specific interactions for a dynamically interacting system and provides an understanding of protein-protein interactions for BLG at low salt concentrations.
Collapse
Affiliation(s)
- M J Uttinger
- Institute of Particle Technology, Interdisciplinary Center for Functional Particle Systems, Friedrich-Alexander-Universität Erlangen-Nürnberg, Haberstraße 9a, 91058 Erlangen, Germany.
| | - C S Hundschell
- Institute of Food Technology and Food Chemistry, Department of Food Colloids, Technical University Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - V Lautenbach
- Institute of Particle Technology, Interdisciplinary Center for Functional Particle Systems, Friedrich-Alexander-Universität Erlangen-Nürnberg, Haberstraße 9a, 91058 Erlangen, Germany.
| | - S Pusara
- Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - S Bäther
- Institute of Food Technology and Food Chemistry, Department of Food Colloids, Technical University Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - T R Heyn
- Institute of Human Nutrition and Food Science, Division of Food Technology, Kiel University, 24118 Kiel, Germany
| | - J K Keppler
- Laboratory of Food Process Engineering, Wageningen University, Wageningen, The Netherlands
| | - W Wenzel
- Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - J Walter
- Institute of Particle Technology, Interdisciplinary Center for Functional Particle Systems, Friedrich-Alexander-Universität Erlangen-Nürnberg, Haberstraße 9a, 91058 Erlangen, Germany.
| | - M Kozlowska
- Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - A M Wagemans
- Institute of Food Technology and Food Chemistry, Department of Food Colloids, Technical University Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - W Peukert
- Institute of Particle Technology, Interdisciplinary Center for Functional Particle Systems, Friedrich-Alexander-Universität Erlangen-Nürnberg, Haberstraße 9a, 91058 Erlangen, Germany.
| |
Collapse
|
6
|
Naito H, Okamoto R, Sumi T, Koga K. Osmotic second virial coefficients for hydrophobic interactions as a function of solute size. J Chem Phys 2022; 156:221104. [PMID: 35705398 DOI: 10.1063/5.0097547] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
To gain quantitative insight into how the overall strength of the hydrophobic interaction varies with the molecular size, we calculate osmotic second virial coefficients B for hydrophobic spherical molecules of different diameters σ in water based on molecular simulation with corrections to the finite-size and finite-concentration effects. It is shown that B (<0) changes by two orders of magnitude greater as σ increases twofold and its solute-size dependence is best fit by a power law B ∝ σα with the exponent α ≃ 6, which contrasts with the cubic power law that the second virial coefficients of gases obey. It is also found that values of B for the solutes in a nonpolar solvent are positive but they obey the same power law as in water. A thermodynamic identity for B derived earlier [K. Koga, V. Holten, and B. Widom, J. Phys. Chem. B 119, 13391 (2015)] indicates that if B is asymptotically proportional to a power of σ, the exponent α must be equal to or greater than 6.
Collapse
Affiliation(s)
- Hidefumi Naito
- Department of Chemistry, Faculty of Science, Okayama University, Okayama 700-8530, Japan
| | - Ryuichi Okamoto
- Department of Chemistry, Faculty of Science, Okayama University, Okayama 700-8530, Japan
| | - Tomonari Sumi
- Department of Chemistry, Faculty of Science, Okayama University, Okayama 700-8530, Japan
| | - Kenichiro Koga
- Department of Chemistry, Faculty of Science, Okayama University, Okayama 700-8530, Japan
| |
Collapse
|
7
|
Folberth A, van der Vegt NFA. Temperature induced change of TMAO effects on hydrophobic hydration. J Chem Phys 2022; 156:184501. [DOI: 10.1063/5.0088388] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The effect of trimethylamine-N-oxide (TMAO) on hydrophobic solvation and hydrophobic interactions of methane has been studied with Molecular Dynamics simulations in the temperature range between 280 and 370 K at 1 bar ambient pressure. We observe a temperature transition in the effect of TMAO on the aqueous solubility of methane. At low temperature (280 K), methane is preferentially hydrated, causing TMAO to reduce its solubility in water, while above 320 K, methane preferentially interacts with TMAO, causing TMAO to promote its solubility in water. Based on a statistical-mechanical analysis of the excess chemical potential of methane, we find that the reversible work of creating a repulsive methane cavity opposes the solubility of methane in TMAO/water solution more than in pure water. Below 320 K, this solvent-excluded volume effect overcompensates the contribution of methane–TMAO van der Waals interactions, which promote the solvation of methane and are observed at all temperatures. These van der Waals interactions with the methyl groups of TMAO tip the balance above 320 K where the effect of TMAO on solvent-excluded volume is smaller. We furthermore find that the effective attraction between dissolved methane solutes increases with the increasing TMAO concentration. This observation correlates with a reduction in the methane solubility below 320 K but with an increase in methane solubility at higher temperatures.
Collapse
Affiliation(s)
- Angelina Folberth
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, 64287 Darmstadt, Germany
| | - Nico F. A. van der Vegt
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, 64287 Darmstadt, Germany
| |
Collapse
|
8
|
Evidence of Many-Body Interactions in the Virial Coefficients of Polyelectrolyte Gels. Gels 2022; 8:gels8020096. [PMID: 35200477 PMCID: PMC8871429 DOI: 10.3390/gels8020096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 01/19/2022] [Accepted: 02/02/2022] [Indexed: 12/04/2022] Open
Abstract
Simulation studies of aqueous polymer solutions, and heuristic arguments by De Gennes for aqueous polyethylene oxide polymer solutions, have suggested that many-body interactions can give rise to the ‘anomalous’ situation in which the second osmotic virial coefficient is positive, while the third virial coefficient is negative. This phenomenon was later confirmed in analytic calculations of the phase behavior and the osmotic pressure of complex fluids exhibiting cooperative self-assembly into extended dynamic polymeric structures by Dudowicz et al. In the present study, we experimentally confirm the occurrence of this osmotic virial sign inversion phenomenon for several highly charged model polyelectrolyte gels (poly(acrylic acid), poly(styrene sulfonate), DNA, hyaluronic acid), where the virial coefficients are deduced from osmotic pressure measurements. Our observations qualitatively accord with experimental and simulation studies indicating that polyelectrolyte materials exhibit supramolecular assembly in solution, another symptomatic property of fluids exhibiting many-body interactions. We also find that the inversion in the variation of the second (A2) and third (A2) virial coefficients upon approach to phase separation does not occur in uncharged poly(vinyl acetate) gels. Finally, we briefly discuss the estimation of the osmotic compressibility of swollen polyelectrolyte gels from neutron scattering measurements as an alternative to direct, time-consuming and meticulous osmotic pressure measurements. We conclude by summarizing some general trends and suggesting future research directions of natural and synthetic polyelectrolyte hydrogels.
Collapse
|
9
|
Sumi T, Imamura H. Water-mediated interactions destabilize proteins. Protein Sci 2021; 30:2132-2143. [PMID: 34382697 PMCID: PMC8442971 DOI: 10.1002/pro.4168] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 08/06/2021] [Accepted: 08/09/2021] [Indexed: 01/29/2023]
Abstract
Proteins are folded to avoid exposure of the nonpolar groups to water because water‐mediated interactions between nonpolar groups are a promising factor in the thermodynamic stabilities of proteins—which is a well‐accepted view as one of the unique effects of hydrophobic interactions. This article poses a critical question for this classical view by conducting an accurate solvation free‐energy calculation for a thermodynamic cycle of a protein folding using a liquid‐state density functional theory. Here, the solvation‐free energy for a leucine zipper formation was examined in the coiled‐coil protein GCN4‐p1, a typical model for hydrophobic interactions, which demonstrated that water‐mediated interactions were unfavorable for the association of nonpolar groups in the native state, while the dispersion forces between them were, instead, responsible for the association. Furthermore, the present analysis well predicted the isolated helical state stabilized by pressure, which was previously observed in an experiment. We reviewed the problems in the classical concept and semiempirical presumption that the energetic cost of the hydration of nonpolar groups is a driving force of folding.
Collapse
Affiliation(s)
- Tomonari Sumi
- Research Institute for Interdisciplinary Science, Okayama University, Kita-ku, Japan.,Department of Chemistry, Faculty of Science, Okayama University, Kita-ku, Japan
| | - Hiroshi Imamura
- Department of Applied Chemistry, College of Life Sciences, Ritsumeikan University, Kusatsu, Japan
| |
Collapse
|
10
|
Riera M, Hirales A, Ghosh R, Paesani F. Data-Driven Many-Body Models with Chemical Accuracy for CH4/H2O Mixtures. J Phys Chem B 2020; 124:11207-11221. [DOI: 10.1021/acs.jpcb.0c08728] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Marc Riera
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093, United States
| | - Alan Hirales
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093, United States
| | - Raja Ghosh
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093, United States
| | - Francesco Paesani
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093, United States
- Materials Science and Engineering, University of California San Diego, La Jolla, California 92093, United States
- San Diego Supercomputer Center, University of California San Diego, La Jolla, California 92093, United States
| |
Collapse
|
11
|
Mochizuki K. Reduction of water-mediated repulsion drives poly(N-vinylcaprolactam) collapse upon heating. Phys Chem Chem Phys 2020; 22:1053-1060. [PMID: 31867584 DOI: 10.1039/c9cp05491j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Thermo-sensitive aqueous polymers undergo a coil-to-globule transition on heating, with drastic chemical and structural changes. We performed molecular dynamics simulations for PVCL in water to study the driving forces for the polymer's collapse.
Collapse
Affiliation(s)
- Kenji Mochizuki
- Department of Chemistry and Materials
- Faculty of Textile Science and Technology
- Shinshu University
- Nagano 386-8567
- Japan
| |
Collapse
|
12
|
Barnett JW, Ashbaugh HS. Evaluation of second osmotic virial coefficients from molecular simulation following scaled-particle theory. MOLECULAR SIMULATION 2019. [DOI: 10.1080/08927022.2019.1639698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- J. Wesley Barnett
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA, USA
| | - Henry S. Ashbaugh
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA, USA
| |
Collapse
|
13
|
Abstract
Hydration-shell vibrational spectroscopy provides an experimental window into solute-induced water structure changes that mediate aqueous folding, binding, and self-assembly. Decomposition of measured Raman and infrared (IR) spectra of aqueous solutions using multivariate curve resolution (MCR) and related methods may be used to obtain solute-correlated spectra revealing solute-induced perturbations of water structure, such as changes in water hydrogen-bond strength, tetrahedral order, and the presence of dangling (non-hydrogen-bonded) OH groups. More generally, vibrational-MCR may be applied to both aqueous and nonaqueous solutions, including multicomponent mixtures, to quantify solvent-mediated interactions between oily, polar, and ionic solutes, in both dilute and crowded fluids. Combining vibrational-MCR with emerging theoretical modeling strategies promises synergetic advances in the predictive understanding of multiscale self-assembly processes of both biological and technological interest.
Collapse
Affiliation(s)
- Dor Ben-Amotz
- Department of Chemistry , Purdue University , West Lafayette , Indiana 47907 , United States
| |
Collapse
|
14
|
Chialvo AA, Crisalle OD. On the behavior of the osmotic second virial coefficients of gases in aqueous solutions: Rigorous results, accurate approximations, and experimental evidence. J Chem Phys 2019; 150:124503. [DOI: 10.1063/1.5047525] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Affiliation(s)
| | - Oscar D. Crisalle
- Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611, USA
| |
Collapse
|
15
|
Okamoto R, Onuki A. Theory of nonionic hydrophobic solutes in mixture solvent: Solvent-mediated interaction and solute-induced phase separation. J Chem Phys 2018; 149:014501. [DOI: 10.1063/1.5037673] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Ryuichi Okamoto
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Akira Onuki
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| |
Collapse
|
16
|
Ashbaugh HS, Barnett JW, Saltzman A, Langrehr M, Houser H. Connections between the Anomalous Volumetric Properties of Alcohols in Aqueous Solution and the Volume of Hydrophobic Association. J Phys Chem B 2018; 122:3242-3250. [PMID: 28968101 DOI: 10.1021/acs.jpcb.7b08728] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The partial molar volumes of alcohols in water exhibit a non-monotonic dependence on concentration at room temperature, initially decreasing with increasing concentration before passing through a minimum and rising to the pure liquid plateau. This anomalous behavior is associated with hydrophobic interactions. We report molecular simulations of short chain alcohols and alkanes in water to examine the volumetric properties of these mixtures at infinite dilution over a range of temperatures. Our simulations find this anomaly disappears at a crossover temperature, above which the solute volume only varies monotonically with concentration. A Voronoi volume analysis of solution configurations finds that solutes in clusters take up less space than individual solutes at low temperature and more space at elevated temperatures. These changes in cluster volumes are subsequently shown to correlate with the derivative of the solute partial molar volume with respect to solute concentration. The changes in solute volume upon nonpolar solute association impact the response of molecular-scale hydrophobic interactions for assembly with increasing pressure.
Collapse
Affiliation(s)
- Henry S Ashbaugh
- Department of Chemical and Biomolecular Engineering , Tulane University , New Orleans , Louisiana 70118 , United States
| | - J Wesley Barnett
- Department of Chemical and Biomolecular Engineering , Tulane University , New Orleans , Louisiana 70118 , United States
| | - Alexander Saltzman
- Department of Chemical and Biomolecular Engineering , Tulane University , New Orleans , Louisiana 70118 , United States
| | - Mae Langrehr
- Department of Chemical and Biomolecular Engineering , University of Delaware , Newark , Delaware 19716 , United States
| | - Hayden Houser
- Department of Chemical and Biomolecular Engineering , Tulane University , New Orleans , Louisiana 70118 , United States
| |
Collapse
|
17
|
Koga K, Yamamoto N. Hydrophobicity Varying with Temperature, Pressure, and Salt Concentration. J Phys Chem B 2018; 122:3655-3665. [PMID: 29357255 DOI: 10.1021/acs.jpcb.7b12193] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Temperature-, pressure-, and salt-concentration-induced variations in the solubility of small nonpolar solutes in aqueous solution and the corresponding variations in the solvent-induced pair attraction between such solute molecules are investigated. The variations in the solvation free energy of a solute and those in the solvent-induced pair attraction are well reproduced by a mean-field approximation in which the repulsive cores of solute molecules are treated as hard spheres and the mean-field energy of a solute molecule is taken to be the average potential energy that the solute molecule feels in solution. The mechanisms of variation in the solvation free energy and those of variation in the solvent-induced pair potential, with increasing temperature, pressure, and salt concentration, are clarified. Correlations between the solvation free energy and the solvent-induced pair potential at a contact distance in temperature, pressure, and salt concentration variations are near linear in any mode of variation, but the slope of the linear relation is dependent on the mode of variation and is determined by a ratio of the solvation thermodynamic quantities characteristic of each mode of variation.
Collapse
Affiliation(s)
- K Koga
- Research Institute for Interdisciplinary Science , Okayama University , Okayama 700-8530 , Japan.,Department of Chemistry, Faculty of Science , Okayama University , Okayama 700-8530 , Japan
| | - N Yamamoto
- Department of Chemistry, Faculty of Science , Okayama University , Okayama 700-8530 , Japan
| |
Collapse
|
18
|
Tang D, Delpo C, Blackmon O, Ashbaugh HS. Note: Second osmotic virial coefficients of short alkanes and their alcohol counterparts in water as a function of temperature. J Chem Phys 2018; 148:016101. [DOI: 10.1063/1.5008573] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Affiliation(s)
- Du Tang
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, USA
| | - Courtney Delpo
- Department of Chemistry, Ursinus College, Collegeville, Pennsylvania 19426, USA
| | - Odella Blackmon
- Department of Chemistry, William Carey University, Hattiesburg, Mississippi 39401, USA
| | - Henry S. Ashbaugh
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, USA
| |
Collapse
|
19
|
Sumi T, Maruyama Y, Mitsutake A, Mochizuki K, Koga K. Application of reference‐modified density functional theory: Temperature and pressure dependences of solvation free energy. J Comput Chem 2017; 39:202-217. [DOI: 10.1002/jcc.25101] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 10/18/2017] [Accepted: 10/19/2017] [Indexed: 01/04/2023]
Affiliation(s)
- Tomonari Sumi
- Division of Superconducting and Functional MaterialsResearch Institute for Interdisciplinary Science, Okayama University, 3‐1‐1 Tsushima‐Naka, Kita‐kuOkayama700‐8530 Japan
- Department of Chemistry, Faculty of ScienceOkayama University, 3‐1‐1 Tsushima‐Naka, Kita‐kuOkayama700‐8530 Japan
| | - Yutaka Maruyama
- Co‐Design Team, FLAGSHIP 2020 Project, RIKEN Advanced Institute for Computational Science, 7‐1‐26, Minatojima‐minami‐machiKobe650‐0047 Japan
| | - Ayori Mitsutake
- Department of PhysicsKeio University, 3‐14‐1 Hiyoshi, Kohoku‐kuYokohama Kanagawa223–8522 Japan
| | - Kenji Mochizuki
- Division of Superconducting and Functional MaterialsResearch Institute for Interdisciplinary Science, Okayama University, 3‐1‐1 Tsushima‐Naka, Kita‐kuOkayama700‐8530 Japan
| | - Kenichiro Koga
- Division of Superconducting and Functional MaterialsResearch Institute for Interdisciplinary Science, Okayama University, 3‐1‐1 Tsushima‐Naka, Kita‐kuOkayama700‐8530 Japan
- Department of Chemistry, Faculty of ScienceOkayama University, 3‐1‐1 Tsushima‐Naka, Kita‐kuOkayama700‐8530 Japan
| |
Collapse
|
20
|
|
21
|
Resolving solvophobic interactions inferred from experimental solvation free energies and evaluated from molecular simulations. Chem Phys Lett 2017. [DOI: 10.1016/j.cplett.2016.11.038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
22
|
Cerdeiriña CA, Widom B. Osmotic Second Virial Coefficients of Aqueous Solutions from Two-Component Equations of State. J Phys Chem B 2016; 120:13144-13151. [DOI: 10.1021/acs.jpcb.6b09912] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Claudio A. Cerdeiriña
- Departamento
de Física Aplicada, Universidad de Vigo, Campus del Agua, Ourense 32004, Spain
- Department
of Chemistry, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| | - B. Widom
- Department
of Chemistry, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| |
Collapse
|
23
|
Hatano I, Mochizuki K, Sumi T, Koga K. Hydrophobic Polymer Chain in Water That Undergoes a Coil-to-Globule Transition Near Room Temperature. J Phys Chem B 2016; 120:12127-12134. [DOI: 10.1021/acs.jpcb.6b08347] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- I. Hatano
- Research
Institute for Interdisciplinary Science and ‡Department of Chemistry, Faculty
of Science, Okayama University, Okayama 700-8530, Japan
| | - K. Mochizuki
- Research
Institute for Interdisciplinary Science and ‡Department of Chemistry, Faculty
of Science, Okayama University, Okayama 700-8530, Japan
| | - T. Sumi
- Research
Institute for Interdisciplinary Science and ‡Department of Chemistry, Faculty
of Science, Okayama University, Okayama 700-8530, Japan
| | - K. Koga
- Research
Institute for Interdisciplinary Science and ‡Department of Chemistry, Faculty
of Science, Okayama University, Okayama 700-8530, Japan
| |
Collapse
|
24
|
Pratt LR, Chaudhari MI, Rempe SB. Statistical Analyses of Hydrophobic Interactions: A Mini-Review. J Phys Chem B 2016; 120:6455-60. [PMID: 27258151 DOI: 10.1021/acs.jpcb.6b04082] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This review focuses on the striking recent progress in solving for hydrophobic interactions between small inert molecules. We discuss several new understandings. First, the inverse temperature phenomenology of hydrophobic interactions, i.e., strengthening of hydrophobic bonds with increasing temperature, is decisively exhibited by hydrophobic interactions between atomic-scale hard sphere solutes in water. Second, inclusion of attractive interactions associated with atomic-size hydrophobic reference cases leads to substantial, nontrivial corrections to reference results for purely repulsive solutes. Hydrophobic bonds are weakened by adding solute dispersion forces to treatment of reference cases. The classic statistical mechanical theory for those corrections is not accurate in this application, but molecular quasi-chemical theory shows promise. Finally, because of the masking roles of excluded volume and attractive interactions, comparisons that do not discriminate the different possibilities face an interpretive danger.
Collapse
Affiliation(s)
- Lawrence R Pratt
- Department of Chemical and Biomolecular Engineering, Tulane University , New Orleans, Louisiana 70118, United States
| | - Mangesh I Chaudhari
- Center for Biological and Engineering Sciences, Sandia National Laboratories , Albuquerque, New Mexico 87185, United States
| | - Susan B Rempe
- Center for Biological and Engineering Sciences, Sandia National Laboratories , Albuquerque, New Mexico 87185, United States
| |
Collapse
|
25
|
Affiliation(s)
- Dor Ben-Amotz
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907;
| |
Collapse
|
26
|
Mochizuki K, Sumi T, Koga K. Liquid-liquid phase separation of N-isopropylpropionamide aqueous solutions above the lower critical solution temperature. Sci Rep 2016; 6:24657. [PMID: 27098236 PMCID: PMC4838917 DOI: 10.1038/srep24657] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 04/04/2016] [Indexed: 02/01/2023] Open
Abstract
We investigate driving forces of the liquid–liquid phase separation of N-isopropylpropionamide (NiPPA) aqueous solutions above the lower critical solution temperature using molecular dynamics simulations. Spontaneous phase separations of the model aqueous solution with a modified OPLS-AA force field are observed above the experimentally determined cloud point. The destabilization toward the phase separation is confirmed by temperature dependence of the long-wavelength limit of the concentration-concentration structure factor, the dominant component of which is found to be an increasing effective attraction between NiPPA molecules. At varying temperatures, the potentials of mean force (PMFs) between a pair of NiPPA molecules at infinite dilution are obtained and decomposed into the nonpolar and Coulombic contributions. The nonpolar contribution, arising essentially from molecular volume, promotes association of NiPPA molecules with increasing temperature while the Coulombic one antagonizes the association. Thus, our analysis leads to a conclusion that the driving force of thermally induced aggregation of NiPPA molecules is the temperature dependence of the nonpolar contribution in PMF between NiPPA molecules, not the temperature dependence of the number or strength of hydrogen bonds between NiPPA and water molecules.
Collapse
Affiliation(s)
- Kenji Mochizuki
- Department of Chemistry, Faculty of Science, Okayama University, Okayama 700-8530, Japan.,Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Tomonari Sumi
- Department of Chemistry, Faculty of Science, Okayama University, Okayama 700-8530, Japan.,Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Kenichiro Koga
- Department of Chemistry, Faculty of Science, Okayama University, Okayama 700-8530, Japan.,Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| |
Collapse
|
27
|
Chaudhari MI, Rempe SB, Asthagiri D, Tan L, Pratt LR. Molecular Theory and the Effects of Solute Attractive Forces on Hydrophobic Interactions. J Phys Chem B 2016; 120:1864-70. [DOI: 10.1021/acs.jpcb.5b09552] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mangesh I. Chaudhari
- Center
for Biological and Material Sciences, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - Susan B. Rempe
- Center
for Biological and Material Sciences, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - D. Asthagiri
- Department
of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, United States
| | - L. Tan
- Department
of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - L. R. Pratt
- Department
of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| |
Collapse
|
28
|
Mochizuki K, Koga K. Cononsolvency behavior of hydrophobes in water + methanol mixtures. Phys Chem Chem Phys 2016; 18:16188-95. [DOI: 10.1039/c6cp01496h] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The molecular origin of cononsolvency behavior is explored using molecular dynamics simulations.
Collapse
Affiliation(s)
- Kenji Mochizuki
- Department of Chemistry
- Faculty of Science
- Okayama University
- Okayama 700-8530
- Japan
| | - Kenichiro Koga
- Department of Chemistry
- Faculty of Science
- Okayama University
- Okayama 700-8530
- Japan
| |
Collapse
|
29
|
Mochizuki K, Sumi T, Koga K. Driving forces for the pressure-induced aggregation of poly(N-isopropylacrylamide) in water. Phys Chem Chem Phys 2016; 18:4697-703. [DOI: 10.1039/c5cp07674a] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Driving forces for the pressure-induced aggregation of poly(N-isopropylacrylamide) in water are discussed.
Collapse
Affiliation(s)
- Kenji Mochizuki
- Department of Chemistry
- Faculty of Science
- Okayama University
- Okayama 700-8530
- Japan
| | - Tomonari Sumi
- Department of Chemistry
- Faculty of Science
- Okayama University
- Okayama 700-8530
- Japan
| | - Kenichiro Koga
- Department of Chemistry
- Faculty of Science
- Okayama University
- Okayama 700-8530
- Japan
| |
Collapse
|
30
|
Koga K, Holten V, Widom B. Deriving Second Osmotic Virial Coefficients from Equations of State and from Experiment. J Phys Chem B 2015; 119:13391-7. [DOI: 10.1021/acs.jpcb.5b07685] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- K. Koga
- Department
of Chemistry, Faculty of Science, Okayama University, Okayama 700-8530, Japan
| | - Vincent Holten
- Department
of Chemistry, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| | - B. Widom
- Department
of Chemistry, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| |
Collapse
|
31
|
Vafaei S, Tomberli B, Gray CG. McMillan-Mayer theory of solutions revisited: simplifications and extensions. J Chem Phys 2015; 141:154501. [PMID: 25338903 DOI: 10.1063/1.4897980] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
McMillan and Mayer (MM) proved two remarkable theorems in their paper on the equilibrium statistical mechanics of liquid solutions. They first showed that the grand canonical partition function for a solution can be reduced to one with an effectively solute-only form, by integrating out the solvent degrees of freedom. The total effective solute potential in the effective solute grand partition function can be decomposed into components which are potentials of mean force for isolated groups of one, two, three, etc., solute molecules. Second, from the first result, now assuming low solute concentration, MM derived an expansion for the osmotic pressure in powers of the solute concentration, in complete analogy with the virial expansion of gas pressure in powers of the density at low density. The molecular expressions found for the osmotic virial coefficients have exactly the same form as the corresponding gas virial coefficients, with potentials of mean force replacing vacuum potentials. In this paper, we restrict ourselves to binary liquid solutions with solute species A and solvent species B and do three things: (a) By working with a semi-grand canonical ensemble (grand with respect to solvent only) instead of the grand canonical ensemble used by MM, and avoiding graphical methods, we have greatly simplified the derivation of the first MM result, (b) by using a simple nongraphical method developed by van Kampen for gases, we have greatly simplified the derivation of the second MM result, i.e., the osmotic pressure virial expansion; as a by-product, we show the precise relation between MM theory and Widom potential distribution theory, and (c) we have extended MM theory by deriving virial expansions for other solution properties such as the enthalpy of mixing. The latter expansion is proving useful in analyzing ongoing isothermal titration calorimetry experiments with which we are involved. For the enthalpy virial expansion, we have also changed independent variables from semi-grand canonical, i.e., fixed {N(A), μ(B), V, T}, to those relevant to the experiment, i.e., fixed {N(A), N(B), p, T}, where μ denotes chemical potential, N the number of molecules, V the volume, p the pressure, and T the temperature.
Collapse
Affiliation(s)
- Shaghayegh Vafaei
- Department of Physics and Biophysics Interdepartmental Group, University of Guelph, Guelph, Ontario N1G2W1, Canada
| | - Bruno Tomberli
- Department of Physics, Capilano University, Vancouver, British Columbia V7J3H5, Canada
| | - C G Gray
- Department of Physics, University of Guelph, Guelph, Ontario N1G2W1, Canada
| |
Collapse
|
32
|
Kinoshita M, Kim JY, Kume S, Sakakibara Y, Sugiki T, Kojima C, Kurisu G, Ikegami T, Hase T, Kimata-Ariga Y, Lee YH. Physicochemical nature of interfaces controlling ferredoxin NADP(+) reductase activity through its interprotein interactions with ferredoxin. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1847:1200-11. [PMID: 26087388 DOI: 10.1016/j.bbabio.2015.05.023] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 05/27/2015] [Accepted: 05/29/2015] [Indexed: 01/27/2023]
Abstract
Although acidic residues of ferredoxin (Fd) are known to be essential for activities of various Fd-dependent enzymes, including ferredoxin NADP(+) reductase (FNR) and sulfite reductase (SiR), through electrostatic interactions with basic residues of partner enzymes, non-electrostatic contributions such as hydrophobic forces remain largely unknown. We herein demonstrated that intermolecular hydrophobic and charge-charge interactions between Fd and enzymes were both critical for enzymatic activity. Systematic site-directed mutagenesis, which altered physicochemical properties of residues on the interfaces of Fd for FNR /SiR, revealed various changes in activities of both enzymes. The replacement of serine 43 of Fd to a hydrophobic residue (S43W) and charged residue (S43D) increased and decreased FNR activity, respectively, while S43W showed significantly lower SiR activity without affecting SiR activity by S43D, suggesting that hydrophobic and electrostatic interprotein forces affected FNR activity. Enzyme kinetics revealed that changes in FNR activity by mutating Fd correlated with Km, but not with kcat or activation energy, indicating that interprotein interactions determined FNR activity. Calorimetry-based binding thermodynamics between Fd and FNR showed different binding modes of FNR to wild-type, S43W, or S43D, which were controlled by enthalpy and entropy, as shown by the driving force plot. Residue-based NMR spectroscopy of (15)N FNR with Fds also revealed distinct binding modes of each complex based on different directions of NMR peak shifts with similar overall chemical shift differences. We proposed that subtle adjustments in both hydrophobic and electrostatic forces were critical for enzymatic activity, and these results may be applicable to protein-based electron transfer systems.
Collapse
Affiliation(s)
- Misaki Kinoshita
- Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan
| | - Ju Yaen Kim
- Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan
| | - Satoshi Kume
- Cellular Function Imaging Team, Division of Bio-function Dynamics Imaging, RIKEN Center for Life Science Technologies, Kobe, Hyogo 650-0047, Japan
| | - Yukiko Sakakibara
- Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan
| | - Toshihiko Sugiki
- Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan
| | - Chojiro Kojima
- Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan
| | - Genji Kurisu
- Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan
| | - Takahisa Ikegami
- Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan
| | - Toshiharu Hase
- Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan
| | - Yoko Kimata-Ariga
- Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan.
| | - Young-Ho Lee
- Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan.
| |
Collapse
|
33
|
Ashbaugh HS, Weiss K, Williams SM, Meng B, Surampudi LN. Temperature and Pressure Dependence of Methane Correlations and Osmotic Second Virial Coefficients in Water. J Phys Chem B 2015; 119:6280-94. [DOI: 10.1021/acs.jpcb.5b02056] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Henry S. Ashbaugh
- Department
of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Katie Weiss
- Alfred University, Alfred, New York 14802, United States
| | - Steven M. Williams
- Department
of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Bin Meng
- Department
of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Lalitanand N. Surampudi
- Department
of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| |
Collapse
|
34
|
Abstract
Processes ranging from oil-water phase separation to the formation of solid clathrate hydrates send mixed messages regarding whether oil molecules hate or love to be surrounded by water. Recent experimental and theoretical results help decipher these mixed messages by illuminating the conditions under which the stability of a hydrophobic contact is expected to exceed thermal energy fluctuations - thus facilitating hydrophobic self-assembly and the emergence of structure from randomness. Important open questions remain regarding the dependence of hydrophobic interactions on molecular size and temperature, as well as the balance of direct and water-mediated interactions.
Collapse
Affiliation(s)
- Dor Ben-Amotz
- Purdue University, Department of Chemistry, West Lafayette, Indiana 47907, United States
| |
Collapse
|
35
|
Meng B, Ashbaugh HS. Effect of hydrostatic pressure on gas solubilization in micelles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:3318-3325. [PMID: 25730396 DOI: 10.1021/la503646z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Molecular dynamics simulations of anionic sodium decylsulfate and nonionic pentaethylene glycol monodecyl ether micelles in water have been performed to examine the impact of hydrostatic pressure on argon solubilization as a function of pressure. The potential-of-mean force between the micelles and argon demonstrates that nonpolar gases are attracted to the interiors of both micelles. The affinity of argon for micelle interiors, however, decreases with increasing pressure as a result of the comparatively higher molar volume of argon inside assemblies. We evaluate solubility enhancement coefficients, which describe the drop in the solute chemical potential as a function of the micellized surfactant concentration, to quantify the impact of micellization on gas solubilization. While argon is similarly attracted to the hydrophobic cores of both micelles, the gas is more effectively sequestered within nonionic micelles compared with anionic micelles as a result of salting out by charged head groups and accompanying counterions. The solubility enhancement coefficients of both micelles decrease with increasing pressure, reflecting the changing forces observed in the potentials-of-mean force. An analytical liquid drop model is proposed to describe the pressure dependence of argon solubilization within micelles that captures the simulation solubility enhancement coefficients after fitting an effective micelle radius for each surfactant.
Collapse
Affiliation(s)
- Bin Meng
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Henry S Ashbaugh
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| |
Collapse
|
36
|
Rankin BM, Ben-Amotz D, van der Post ST, Bakker HJ. Contacts Between Alcohols in Water Are Random Rather than Hydrophobic. J Phys Chem Lett 2015; 6:688-92. [PMID: 26262487 DOI: 10.1021/jz5027129] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Given the importance of water-mediated hydrophobic interactions in a wide range of biological and synthetic self-assembly processes, it is remarkable that both the sign and the magnitude of the hydrophobic interactions between simple amphiphiles, such as alcohols, remain unresolved. To address this question, we have performed Raman hydration-shell vibrational spectroscopy and polarization-resolved femtosecond infrared experiments, as well as random mixing and molecular dynamics simulations. Our results indicate that there are no more hydrophobic contacts in aqueous solutions of alcohols ranging from methanol to tertiary butyl alcohol than in random mixtures of the same concentration. This implies that the interaction between small hydrophobic groups is weaker than thermal energy fluctuations. Thus, the corresponding water-mediated hydrophobic interaction must be repulsive, with a magnitude sufficient to negate the attractive direct van der Waals interaction between the hydrophobic groups.
Collapse
Affiliation(s)
- Blake M Rankin
- †Purdue University, Department of Chemistry, West Lafayette, Indiana 47907, United States
| | - Dor Ben-Amotz
- †Purdue University, Department of Chemistry, West Lafayette, Indiana 47907, United States
| | | | - Huib J Bakker
- ‡FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| |
Collapse
|
37
|
|
38
|
Chaudhari MI, Sabo D, Pratt LR, Rempe SB. Hydration of Kr(aq) in Dilute and Concentrated Solutions. J Phys Chem B 2014; 119:9098-102. [DOI: 10.1021/jp508866h] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Mangesh I. Chaudhari
- Center
for Biological and
Material Sciences, Sandia National Laboratories, Albuquerque, New Mexico 87123, United States
| | - Dubravko Sabo
- Department of Chemistry, New York University, New York, New York 10003, United States
| | - Lawrence R. Pratt
- Department of Chemical
and
Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Susan B. Rempe
- Center for Biological and
Material Sciences, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| |
Collapse
|
39
|
Molecular-scale hydrophobic interactions between hard-sphere reference solutes are attractive and endothermic. Proc Natl Acad Sci U S A 2013; 110:20557-62. [PMID: 24297918 DOI: 10.1073/pnas.1312458110] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The osmotic second virial coefficients, B2, for atomic-sized hard spheres in water are attractive (B2 < 0) and become more attractive with increasing temperature (ΔB2/ΔT < 0) in the temperature range 300 K ≤ T ≤ 360 K. Thus, these hydrophobic interactions are attractive and endothermic at moderate temperatures. Hydrophobic interactions between atomic-sized hard spheres in water are more attractive than predicted by the available statistical mechanical theory. These results constitute an initial step toward detailed molecular theory of additional intermolecular interaction features, specifically, attractive interactions associated with hydrophobic solutes.
Collapse
|