1
|
Rudani BA, Jakubowski A, Kriegs H, Wiegand S. Deciphering the guanidinium cation: Insights into thermal diffusion. J Chem Phys 2024; 160:214502. [PMID: 38828819 DOI: 10.1063/5.0215843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2024] [Accepted: 05/16/2024] [Indexed: 06/05/2024] Open
Abstract
Thermophoresis, or thermodiffusion, is becoming a more popular method for investigating the interactions between proteins and ligands due to its high sensitivity to the interactions between solutes and water. Despite its growing use, the intricate mechanisms behind thermodiffusion remain unclear. This gap in knowledge stems from the complexities of thermodiffusion in solvents that have specific interactions as well as the intricate nature of systems that include many components with both non-ionic and ionic groups. To deepen our understanding, we reduce complexity by conducting systematic studies on aqueous salt solutions. In this work, we focused on how guanidinium salt solutions behave in a temperature gradient, using thermal diffusion forced Rayleigh scattering experiments at temperatures ranging from 15 to 35 °C. We looked at the thermodiffusive behavior of four guanidinium salts (thiocyanate, iodide, chloride, and carbonate) in solutions with concentrations ranging from 1 to 3 mol/kg. The guanidinium cation is disk-shaped and is characterized by flat hydrophobic surfaces and three amine groups, which enable directional hydrogen bonding along the edges. We compare our results to the behavior of salts with spherical cations, such as sodium, potassium, and lithium. Our discussions are framed around how different salts are solvated, specifically in the context of the Hofmeister series, which ranks ions based on their effects on the solvation of proteins.
Collapse
Affiliation(s)
- Binny A Rudani
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
| | - Andre Jakubowski
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
| | - Hartmut Kriegs
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
| | - Simone Wiegand
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
| |
Collapse
|
2
|
Lee N, Mohanakumar S, Briels WJ, Wiegand S. Non-monotonic Soret coefficients of aqueous LiCl solutions with varying concentrations. Phys Chem Chem Phys 2024; 26:7830-7836. [PMID: 38375894 DOI: 10.1039/d3cp06061f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2024]
Abstract
We investigate the thermodiffusive properties of aqueous solutions of lithium chloride, using thermal diffusion forced Rayleigh scattering in a concentration range of 0.5-2 mole per kg of solvent and a temperature range of 5 to 45 °C. All solutions exhibit non-monotonic variations of the Soret coefficient ST with a concentration exhibiting a minimum at about one mole per kg of solvent. The depth of the minimum decreases with increasing temperature and shifts slightly towards higher concentrations. We compare the experimental data with published data and apply a recent model based on overlapping hydration shells. Additionally, we calculate the ratio of the phenomenological Onsager coefficients using our experimental results and published data to calculate the thermodynamic factor. Simple linear, quadratic and exponential functions can be used to describe this ratio accurately, and together with the thermodynamic factors, the experimental Soret coefficients can be reproduced. The main conclusion from this analysis is that the minimum of the Soret coefficients results from a maximum in the thermodynamic factor, which appears itself at concentrations far below the experimental concentrations. Only after multiplication by the (negative) monotonous Onsager ratio does the minimum move into the experimental concentration window.
Collapse
Affiliation(s)
- Namkyu Lee
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, Jülich D-52428, Germany.
- Department of Mechanical Engineering, Yonsei University, Seoul, Korea.
| | - Shilpa Mohanakumar
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, Jülich D-52428, Germany.
| | - W J Briels
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, Jülich D-52428, Germany.
- University of Twente, Computational Chemical Physics, Postbus 217, Enschede 7500 AE, The Netherlands.
| | - Simone Wiegand
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, Jülich D-52428, Germany.
- Chemistry Department - Physical Chemistry, University Cologne, Cologne D-50939, Germany
| |
Collapse
|
3
|
Mohanakumar S, Lee N, Wiegand S. Complementary Experimental Methods to Obtain Thermodynamic Parameters of Protein Ligand Systems. Int J Mol Sci 2022; 23:ijms232214198. [PMID: 36430678 PMCID: PMC9692857 DOI: 10.3390/ijms232214198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 11/10/2022] [Accepted: 11/12/2022] [Indexed: 11/18/2022] Open
Abstract
In recent years, thermophoresis has emerged as a promising tool for quantifying biomolecular interactions. The underlying microscopic physical effect is still not understood, but often attributed to changes in the hydration layer once the binding occurs. To gain deeper insight, we investigate whether non-equilibrium coefficients can be related to equilibrium properties. Therefore, we compare thermophoretic data measured by thermal diffusion forced Rayleigh scattering (TDFRS) (which is a non-equilibrium process) with thermodynamic data obtained by isothermal titration calorimetry (ITC) (which is an equilibrium process). As a reference system, we studied the chelation reaction between ethylenediaminetetraacetic acid (EDTA) and calcium chloride (CaCl2) to relate the thermophoretic behavior quantified by the Soret coefficient ST to the Gibb's free energy ΔG determined in the ITC experiment using an expression proposed by Eastman. Finally, we have studied the binding of the protein Bovine Carbonic Anhydrase I (BCA I) to two different benzenesulfonamide derivatives: 4-fluorobenzenesulfonamide (4FBS) and pentafluorobenzenesulfonamide (PFBS). For all three systems, we find that the Gibb's free energies calculated from ST agree with ΔG from the ITC experiment. In addition, we also investigate the influence of fluorescent labeling, which allows measurements in a thermophoretic microfluidic cell. Re-examination of the fluorescently labeled system using ITC showed a strong influence of the dye on the binding behavior.
Collapse
Affiliation(s)
- Shilpa Mohanakumar
- IBI-4—Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
| | - Namkyu Lee
- IBI-4—Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
| | - Simone Wiegand
- IBI-4—Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
- Chemistry Department-Physical Chemistry, University of Colgone, D-50939 Cologne, Germany
- Correspondence: ; Tel.: +49-2461-61-6654
| |
Collapse
|
4
|
Diaz-Marquez A, Stirnemann G. Mass effects for thermodiffusion in dilute aqueous solutions. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2022; 45:37. [PMID: 35445893 DOI: 10.1140/epje/s10189-022-00193-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Accepted: 04/11/2022] [Indexed: 06/14/2023]
Abstract
Thermodiffusion is the phenomenon by which molecules in a mixture present concentration gradients in response to an imposed temperature gradient. Despite decades of investigations, this effect remains poorly understood at a molecular level. A common, phenomenological approach is to individuate the molecular factors that influence the Soret coefficient, the parameter that quantifies the resulting concentration-gradient. Experimental studies, often performed on organic mixtures, as well as simulations of model particle systems have evidenced that the difference in masses between the mixture components has an important effect on the amplitude of the Soret coefficient. Here, we use molecular dynamics simulations of a thermophoretic setting to investigate the mass dependence of the Soret coefficient in dilute aqueous solutions. An advantage of simulation approaches is that they are not limited in the range of explored molecular masses, which is often limited to isotopic substitutions in the experiments. Our simulations reveal that the mass dependence of the Soret coefficient in these solutions is in agreement with previous experimental and simulation work on molecular-size systems. In particular, it is sensitive to the relative mass difference between the solute and the solvent, but not to their absolute mass. Adjusting the mass of the solvent and of the solute can turn a thermophobic solution into a thermophilic one, where solute accumulation is reversed. This demonstrates that the mass effect can indeed compensate for the other contributions to the Soret coefficient. Finally, we find that changing the molecular moments of inertia has a much more limited impact as compared to a change in the total molecular mass.
Collapse
Affiliation(s)
- Alejandro Diaz-Marquez
- CNRS Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique, PSL University, Université de Paris, 13 rue Pierre et Marie Curie, 75005, Paris, France
| | - Guillaume Stirnemann
- CNRS Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique, PSL University, Université de Paris, 13 rue Pierre et Marie Curie, 75005, Paris, France.
| |
Collapse
|
5
|
Mohanakumar S, Wiegand S. Towards understanding specific ion effects in aqueous media using thermodiffusion. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2022; 45:10. [PMID: 35106668 PMCID: PMC8807466 DOI: 10.1140/epje/s10189-022-00164-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 01/10/2022] [Indexed: 06/14/2023]
Abstract
Specific ion effects play an important role in scientific and technological processes. According to Hofmeister, the influence on the hydrogen bond network depends on the ion and leads to a specific order of the ions. Also thermodiffusion the mass transport caused by a temperature gradient is very sensitive to changes of the hydrogen bond network leading to a ranking according to hydrophilicity of the salt. Hence, we investigate various salt solutions in order to compare with the Hofmeister concept. We have studied three different sodium salts in water as a function of temperature (25-45[Formula: see text]C) and concentration (0.5-5 mol kg[Formula: see text]) using Thermal Diffusion Forced Rayleigh Scattering (TDFRS). The three anions studied, carbonate, acetate and thiocyanate, span the entire range of the Hofmeister series from hydrophilic to hydrophobic. We compare the results with the recent measurements of the corresponding potassium salts to see to what extent the cation changes the thermodiffusion of the salt.
Collapse
Affiliation(s)
- Shilpa Mohanakumar
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428, Jülich, Germany
| | - Simone Wiegand
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428, Jülich, Germany.
- Chemistry Department-Physical Chemistry, University Cologne, D-50939, Cologne, Germany.
| |
Collapse
|
6
|
Mohanakumar S, Kriegs H, Briels WJ, Wiegand S. Overlapping hydration shells in salt solutions causing non-monotonic Soret coefficients with varying concentration. Phys Chem Chem Phys 2022; 24:27380-27387. [DOI: 10.1039/d2cp04089a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We develop an intuitive picture that overlapping hydration shells in salt solutions cause non-monotonic Soret coefficients with varying concentration.
Collapse
Affiliation(s)
- Shilpa Mohanakumar
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
| | - Hartmut Kriegs
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
| | - W. J. Briels
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
- University of Twente, Computational Chemical Physics, Postbus 217, 7500 AE Enschede, The Netherlands
| | - Simone Wiegand
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
- Chemistry Department – Physical Chemistry, University Cologne, D-50939 Cologne, Germany
| |
Collapse
|
7
|
Rezende Franco L, Sehnem AL, Figueiredo Neto AM, Coutinho K. Molecular Dynamics Approach to Calculate the Thermodiffusion (Soret and Seebeck) Coefficients of Salts in Aqueous Solutions. J Chem Theory Comput 2021; 17:3539-3553. [PMID: 33942620 DOI: 10.1021/acs.jctc.1c00116] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
An approach to investigate the physical parameters related to ion thermodiffusion in aqueous solutions is proposed herein by calculating the equilibrium hydration free energy and the self-diffusion coefficient as a function of temperature, ranging from 293 to 353 K, using molecular dynamics simulations of infinitely diluted ions in aqueous solutions. Several ion force field parameters are used in the simulations, and new parameters are proposed for some ions to better describe their hydration free energy. Such a theoretical framework enables the calculation of some single-ion properties, such as heat of transport, Soret coefficient, and mass current density, as well as properties of salts, such as effective mass and thermal diffusion, Soret and Seebeck, coefficients. These calculated properties are compared with experimental data available from optical measurements and showed good agreement revealing an excellent theoretical predictability of salt thermodiffusion properties. Differences in single-ion Soret and self-diffusion coefficients of anions and cations give rise to a thermoelectric field, which affects the system response that is quantified by the Seebeck coefficient. The fast and slow Seebeck coefficients are calculated and discussed, resulting in values with mV/K order of magnitude, as observed in experiments involving several salts, such as K+Cl-, Na+Cl-, H+Cl-, Na+OH-, TMA+OH-, and TBA+OH-. The present approach can be adopted for any ion or charged particle dispersed in water with the aim of predicting the thermoelectric field induced through the fluid. It has potential applications in designing electrolytes for ionic thermoelectric devices in order to harvest energy and thermoelectricity in biological nanofluids.
Collapse
Affiliation(s)
- Leandro Rezende Franco
- Universidade de Sao Paulo, Instituto de Fisica, Cidade Universitaria, Sao Paulo 05508-090, SP, Brazil
| | - André Luiz Sehnem
- Universidade de Sao Paulo, Instituto de Fisica, Cidade Universitaria, Sao Paulo 05508-090, SP, Brazil
| | | | - Kaline Coutinho
- Universidade de Sao Paulo, Instituto de Fisica, Cidade Universitaria, Sao Paulo 05508-090, SP, Brazil
| |
Collapse
|
8
|
Mohanakumar S, Luettmer-Strathmann J, Wiegand S. Thermodiffusion of aqueous solutions of various potassium salts. J Chem Phys 2021; 154:084506. [DOI: 10.1063/5.0038039] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Affiliation(s)
- Shilpa Mohanakumar
- IBI-4: Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
| | - Jutta Luettmer-Strathmann
- Department of Physics and Department of Chemistry, The University of Akron, Akron, Ohio 44325-4001, USA
| | - Simone Wiegand
- IBI-4: Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
| |
Collapse
|
9
|
Thermophoresis: The Case of Streptavidin and Biotin. Polymers (Basel) 2020; 12:polym12020376. [PMID: 32046223 PMCID: PMC7077373 DOI: 10.3390/polym12020376] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 01/27/2020] [Accepted: 01/29/2020] [Indexed: 02/02/2023] Open
Abstract
Thermophoretic behavior of a free protein changes upon ligand binding and gives access to information on the binding constants. The Soret effect has also been proven to be a promising tool to gain information on the hydration layer, as the temperature dependence of the thermodiffusion behavior is sensitive to solute–solvent interactions. In this work, we perform systematic thermophoretic measurements of the protein streptavidin (STV) and of the complex STV with biotin (B) using thermal diffusion forced Rayleigh scattering (TDFRS). Our experiments show that the temperature sensitivity of the Soret coefficient is reduced for the complex compared to the free protein. We discuss our data in comparison with recent quasi-elastic neutron scattering (QENS) measurements. As the QENS measurement has been performed in heavy water, we perform additional measurements in water/heavy water mixtures. Finally, we also elucidate the challenges arising from the quantiative thermophoretic study of complex multicomponent systems such as protein solutions.
Collapse
|
10
|
Niether D, Wiegand S. Thermophoresis of biological and biocompatible compounds in aqueous solution. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:503003. [PMID: 31491783 DOI: 10.1088/1361-648x/ab421c] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
With rising popularity of microscale thermophoresis for the characterisation of protein-ligand binding reactions and possible applications in microfluidic devices, there is a growing interest in considering thermodiffusion in the context of life sciences. But although the understanding of thermodiffusion in non-polar mixtures has grown rapidly in recent years, predictions for associated mixtures like aqueous solutions remain challenging. This review aims to give an overview of the literature on thermodiffusion in aqueous systems, show the difficulties in theoretical description that arise from the non-ideal behaviour of water-mixtures, and highlight the relevance of thermodiffusion in a biological context. We find that the thermodiffusion in aqueous systems is dominated by contributions from heat of transfer, hydrogen bond interactions and charge effects. However, the separation of these effects is often difficult, especially in case of biological systems where a systematic exclusion of contributions may not be feasible.
Collapse
Affiliation(s)
- D Niether
- ICS-3 Soft Condensed Matter, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
| | | |
Collapse
|
11
|
Sarter M, Niether D, Koenig BW, Lohstroh W, Zamponi M, Jalarvo NH, Wiegand S, Fitter J, Stadler AM. Strong Adverse Contribution of Conformational Dynamics to Streptavidin-Biotin Binding. J Phys Chem B 2019; 124:324-335. [PMID: 31710813 DOI: 10.1021/acs.jpcb.9b08467] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Molecular dynamics plays an important role for the biological function of proteins. For protein ligand interactions, changes of conformational entropy of protein and hydration layer are relevant for the binding process. Quasielastic neutron scattering (QENS) was used to investigate differences in protein dynamics and conformational entropy of ligand-bound and ligand-free streptavidin. Protein dynamics were probed both on the fast picosecond time scale using neutron time-of-flight spectroscopy and on the slower nanosecond time scale using high-resolution neutron backscattering spectroscopy. We found the internal equilibrium motions of streptavidin and the corresponding mean square displacements (MSDs) to be greatly reduced upon biotin binding. On the basis of the observed MSDs, we calculated the difference of conformational entropy ΔSconf of the protein component between ligand-bound and ligand-free streptavidin. The rather large negative ΔSconf value (-2 kJ mol-1 K-1 on the nanosecond time scale) obtained for the streptavidin tetramer seems to be counterintuitive, given the exceptionally high affinity of streptavidin-biotin binding. Literature data on the total entropy change ΔS observed upon biotin binding to streptavidin, which includes contributions from both the protein and the hydration water, suggest partial compensation of the unfavorable ΔSconf by a large positive entropy gain of the surrounding hydration layer and water molecules that are displaced during ligand binding.
Collapse
Affiliation(s)
- Mona Sarter
- I. Physikalisches Institut (IA), AG Biophysik , RWTH Aachen , Sommerfeldstrasse 14 , Aachen D-52074 , Germany
| | | | | | - Wiebke Lohstroh
- Heinz Maier-Leibnitz Zentrum , Technische Universität München , Garching D-85747 , Germany
| | - Michaela Zamponi
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ) , Forschungszentrum Jülich GmbH , Lichtenbergstrasse 1 , Garching D-85748 , Germany
| | - Niina H Jalarvo
- Neutron Scattering Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831-6475 , United States
| | - Simone Wiegand
- Department für Chemie - Physikalische Chemie , Universität zu Köln , Cologne D-50939 , Germany
| | - Jörg Fitter
- I. Physikalisches Institut (IA), AG Biophysik , RWTH Aachen , Sommerfeldstrasse 14 , Aachen D-52074 , Germany.,Institute of Complex Systems, Molecular Biophysics (ICS-5) , Forschungszentrum Jülich GmbH , Jülich D-52428 , Germany
| | - Andreas M Stadler
- Institute of Physical Chemistry , RWTH Aachen University , Landoltweg 2 , Aachen D-52056 , Germany
| |
Collapse
|
12
|
Luettmer-Strathmann J. Configurational contribution to the Soret effect of a protein ligand system : An investigation with density-of-states simulations. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2019; 42:77. [PMID: 31222556 DOI: 10.1140/epje/i2019-11840-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 05/13/2019] [Indexed: 06/09/2023]
Abstract
Many of the biological functions of proteins are closely associated with their ability to bind ligands and change conformations in response to changing conditions. Since binding state and conformation of a protein affect its response to a temperature gradient, they may be probed with thermophoresis. In recent years, thermophoretic techniques to investigate biomolecular interactions, quantify ligand binding, and probe conformational changes have become established. To develop a better understanding of the mechanisms underlying the thermophoretic behavior of proteins and ligands, we employ a simple, off-lattice model for a protein and ligand in explicit solvent. To investigate the partitioning of the particles in a temperature gradient, we perform Wang-Landau-type simulations in a divided simulation box and construct the density of states over a two-dimensional state space. This method gives us access to the entropy and energy of the divided system and allows us to estimate the configurational contribution to the Soret coefficient. In this work, we focus on dilute solutions of hydrophobic proteins and investigate the effect of ligand binding on their thermophoretic behavior. We find that our simple model captures important aspects of protein-ligand interactions and allows us to relate the binding energy to the change in Soret coefficient upon ligand binding.
Collapse
Affiliation(s)
- Jutta Luettmer-Strathmann
- Department of Physics and Department of Chemistry, The University of Akron, 44325-4001, Akron, OH, USA.
| |
Collapse
|
13
|
Bjelčić M, Niether D, Wiegand S. Correlation between thermophoretic behavior and hydrophilicity for various alcohols ⋆. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2019; 42:68. [PMID: 31144058 DOI: 10.1140/epje/i2019-11831-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 04/30/2019] [Indexed: 06/09/2023]
Abstract
Recent experiments for various amides and sugars showed a clear correlation of the temperature dependence of the Soret coefficient with the hydrophilicity, quantitatively described by the logarithm of the 1-octanol/water partition coefficient log P . This coefficient is a measure for the hydrophilicity/hydrophobicity balance of a solute and is often used to model the transport of a compound in the environment or to screen for potential pharmaceutical compounds. In order to validate whether this concept works also for other water soluble molecules we investigated systematically the thermophoresis of mono- and polyhydric alcohols. As experimental method we use a holographic grating technique called infrared Thermal Diffusion Forced Rayleigh Scattering (IR-TDFRS). Experiments showed that the temperature dependence of the Soret coefficient of polyhydric alcohols also correlates with log P and lies on the same master plot as amides and sugars.
Collapse
Affiliation(s)
- Monika Bjelčić
- ICS-3 Soft Condensed Matter, Forschungszentrum Jülich GmbH, D-52428, Jülich, Germany
| | - Doreen Niether
- ICS-3 Soft Condensed Matter, Forschungszentrum Jülich GmbH, D-52428, Jülich, Germany
| | - Simone Wiegand
- ICS-3 Soft Condensed Matter, Forschungszentrum Jülich GmbH, D-52428, Jülich, Germany.
| |
Collapse
|
14
|
Wang Z, Niether D, Buitenhuis J, Liu Y, Lang PR, Dhont JKG, Wiegand S. Thermophoresis of a Colloidal Rod: Contributions of Charge and Grafted Polymers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:1000-1007. [PMID: 30607956 DOI: 10.1021/acs.langmuir.8b03614] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In this study, we investigated the thermodiffusion behavior of a colloidal model system as a function of the Debye length, λDH, which is controlled by the ionic strength. Our system consists of an fd-virus grafted with poly(ethylene glycol) (PEG) with a molecular mass of 5000 g mol-1. The results are compared with recent measurements on a bare fd-virus and with results of PEG. The diffusion coefficients of both viruses are comparable and increase with the increasing Debye length. The thermal diffusion coefficient, DT, of the bare virus increases strongly with the Debye length, whereas DT of the grafted fd-virus shows only a very weak increase. The Debye length dependence of both systems can be described with an expression derived for charged rods using the surface charge density and an offset of DT as adjustable parameters. It turns out that the ratio of the determined surface charges is inverse to the ratio of the surfaces of the two systems, which means that the total charge remains almost constant. The determined offset of the grafted fd-virus describing the chemical contributions is the sum of DT of PEG and the offset of the bare fd-virus. At high λDH, corresponding to the low ionic strength, the ST values of both colloidal model systems approach each other. This implies a contribution from the polymer layer, which is strong at short λDH and fades out for the longer Debye lengths, when the electric double layer reaches further than the polymer chains and therefore dominates interactions with the surrounding water.
Collapse
Affiliation(s)
- Zilin Wang
- ICS-3 Soft Condensed Matter , Forschungszentrum Jülich GmbH , D-52428 Jülich , Germany
| | - Doreen Niether
- ICS-3 Soft Condensed Matter , Forschungszentrum Jülich GmbH , D-52428 Jülich , Germany
| | - Johan Buitenhuis
- ICS-3 Soft Condensed Matter , Forschungszentrum Jülich GmbH , D-52428 Jülich , Germany
| | - Yi Liu
- ICS-3 Soft Condensed Matter , Forschungszentrum Jülich GmbH , D-52428 Jülich , Germany
| | - Peter R Lang
- ICS-3 Soft Condensed Matter , Forschungszentrum Jülich GmbH , D-52428 Jülich , Germany
| | - Jan K G Dhont
- ICS-3 Soft Condensed Matter , Forschungszentrum Jülich GmbH , D-52428 Jülich , Germany
- Department of Physics , Heinrich-Heine-Universität Düsseldorf , D-40225 Düsseldorf , Germany
| | - Simone Wiegand
- ICS-3 Soft Condensed Matter , Forschungszentrum Jülich GmbH , D-52428 Jülich , Germany
- Department für Chemie-Physikalische Chemie , Universität zu Köln , 50939 Cologne , Germany
| |
Collapse
|