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Zhao J, Dong T, Yu P, Wang J. Conformation and Metal Cation Binding of Zwitterionic Alanine Tripeptide in Saline Solutions by Infrared Vibrational Spectroscopy and Molecular Dynamics Simulations. J Phys Chem B 2021; 126:161-173. [PMID: 34968072 DOI: 10.1021/acs.jpcb.1c10034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this work, linear infrared (IR) spectroscopy and molecular dynamics (MD) simulations were used to examine the interaction of different metal cations (Na+, Ca2+, Mg2+, and Zn2+) with backbone (amide C═O) and C-terminal carboxylate (COO-) groups in zwitterionic alanine tripeptide (Ala3) in aqueous solutions with varying saline concentrations. Circular dichroism spectra and MD results suggest that Ala3 is predominantly in polyproline-II (PPII) conformation, whose amide-I and asymmetric carboxylate stretching IR vibration signatures are also supported by quantum-chemistry calculations. The zwitterionic form of Ala3 separates the two amide-I modes in frequency, which are weakly coupled modes, as revealed by two-dimensional IR measurement, and can be used to probe backbone-cation interactions at different scenarios (near charged or neutral chemical groups respectively). Cation concentration-dependent IR frequency red shifts in the amide-I mode are seen for both amide-I modes, whereas blue shifts are also seen in the amide-I mode far from the NH3+ group. The observed spectral changes are discussed from the perspective of the salting-in and salting-out abilities of the cations. In addition, all the metal cations studied here (except Zn2+) can specifically coordinate to the COO- group in bidentate and pseudo-bridging forms simultaneously. For Zn2+, only the pseudo-bridging form exists. Our results shed light on the macroscopic protein salting-in and salting-out phenomena from the perspective of key chemical bonds in peptides.
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Affiliation(s)
- Juan Zhao
- Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China.,University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Tiantian Dong
- Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China.,University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Pengyun Yu
- Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China.,University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Jianping Wang
- Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China.,University of Chinese Academy of Sciences, Beijing 100049, P. R. China
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2
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Hwang S, Beckley D, Alekseev KP, Nicholson EM. Hofmeister Effect in RT-QuIC Seeding Activity of Chronic Wasting Disease Prions. Front Bioeng Biotechnol 2021; 9:709965. [PMID: 34660549 PMCID: PMC8515057 DOI: 10.3389/fbioe.2021.709965] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Accepted: 08/16/2021] [Indexed: 11/13/2022] Open
Abstract
Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy (TSE) that causes a fatal neurodegenerative disease in cervids. Cases of CWD are rapidly increasing in North America among wild and farmed cervid populations, and potential for zoonotic transmission is not yet determined. Therefore, in order to manage the disease, it is imperative to devise a system that can detect CWD during its early phases to prevent spread to new captive herds through introduction of CWD-affected animals into otherwise CWD-free herds. Real-time quaking-induced conversion (RT-QuIC) assays have been applied to detect the presence of disease-associated prions from various samples in both animals and humans. In this study, we have tested the use of five Hofmeister anions that range from weakly hydrating to strongly hydrating: Na3citrate, Na2SO4, NaCl, NaI, and NaClO4 in RT-QuIC reactions for CWD seeding activity using different recombinant prion proteins as substrates. This work shows how the ionic environment of the RT-QuIC reaction can enhance or diminish the seeding activity. The use of Na2SO4 or NaI as the sodium salt for RT-QuIC using bank vole recombinant prion substrate for the detection of CWD using brain samples reduces the lag time to detect with reasonable specificity. For detection of the CWD in fecal samples, only NaI showed comparable reduction in lag time relative to NaCl but required reduced temperature to alleviate spontaneous fibril formation in negative control samples. Selection of the proper ion environment and recombinant prion protein substrate will make RT-QuIC a powerful diagnostic tool for early detection of CWD prions, further supporting CWD surveillance in wild and captive cervids.
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Affiliation(s)
- Soyoun Hwang
- United States Department of Agriculture, Agricultural Research Service, National Animal Disease Center, Virus and Prion Research Unit, Ames, IA, United States
| | - Danielle Beckley
- United States Department of Agriculture, Agricultural Research Service, National Animal Disease Center, Virus and Prion Research Unit, Ames, IA, United States.,U.S. Department of Energy, Oak Ridge Institute for Science and Education, Oak Ridge, TN, United States
| | - Konstantin P Alekseev
- United States Department of Agriculture, Agricultural Research Service, National Animal Disease Center, Virus and Prion Research Unit, Ames, IA, United States.,U.S. Department of Energy, Oak Ridge Institute for Science and Education, Oak Ridge, TN, United States.,N. F. Gamaleya National Research Center for Epidemiology and Microbiology, Moscow, Russia
| | - Eric M Nicholson
- United States Department of Agriculture, Agricultural Research Service, National Animal Disease Center, Virus and Prion Research Unit, Ames, IA, United States
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3
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Corbett KM, Ford L, Warren DB, Pouton CW, Chalmers DK. Cyclosporin Structure and Permeability: From A to Z and Beyond. J Med Chem 2021; 64:13131-13151. [PMID: 34478303 DOI: 10.1021/acs.jmedchem.1c00580] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cyclosporins are natural or synthetic undecapeptides with a wide range of actual and potential pharmaceutical applications. Several members of the cyclosporin compound family have remarkably high passive membrane permeabilities that are not well-described by simple structural metrics. Here we review experimental studies of cyclosporin structure and permeability, including cyclosporin-metal complexes. We also discuss models for the conformation-dependent permeability of cyclosporins and similar compounds. Finally, we identify current knowledge gaps in the literature and provide recommendations regarding future avenues of exploration.
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Affiliation(s)
- Karen M Corbett
- Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia
| | - Leigh Ford
- Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia
| | - Dallas B Warren
- Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia
| | - Colin W Pouton
- Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia
| | - David K Chalmers
- Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia
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4
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Park KC, Tsukahara T. Expansion of Ion Effects on Water Induced by a High Hydrophilic Surface of a Polymer Network. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:159-168. [PMID: 31880466 DOI: 10.1021/acs.langmuir.9b02892] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The spatial extent and anion-cation cooperativity of the ion effect on the structure and dynamics of water have long been debated but are still controversial. Previously, we experimentally demonstrated the extensive and cooperative effect of ions on water in a polyamide network by measuring the reflection wavelength (λ) on the ion sensor of poly(N-isopropylacrylamide) (PNIPAAm) hydrogel-immobilized photonic crystals. In the present study, we investigated the influence of the polymer surface on the ion effect by adopting a highly hydrophilic poly(N-isopropylacrylamide-co-N-acryloylaza-18-crown-6) hydrogel as a sensor matrix. In alkaline earth metal salt solutions, the copolymer hydrogel membrane sensor showed the redshift of λ for the specific combination of cations and anions, that is, Ca2+/Cl- and Sr2+/NO3-, which resulted from the concerted binding of ion pairs to the copolymer receptor. In alkali metal salt solutions, the ion sensor showed the blueshift of λ originating from the osmotic dehydration suppressed by the salts. The strength of the ion effect was evaluated by the average osmotic pressure (ΠA) required for the salt-inhibited dehydration in the early stage of hydrogel contraction. From the calculation results of ΠA for the copolymer and PNIPAAm hydrogels, it was found that the high hydrophilic copolymer surface more significantly enhanced the ion effect of structure-making cations (i.e., Li+) compared with borderline (Na+) and structure-breaking (K+ and Cs+) cations. Furthermore, the ion effect exhibited the higher ion cooperativity in combination with chloride anions than with nitrate anions. The enhancement of the long-range cooperative ion effect is derived from the expansion of the interactions between ions, water molecules, and the hydrophilic polymer network.
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Affiliation(s)
- Ki Chul Park
- Laboratory for Advanced Nuclear Energy , Institute of Innovative Research, Tokyo Institute of Technology , Tokyo 152-8550 , Japan
| | - Takehiko Tsukahara
- Laboratory for Advanced Nuclear Energy , Institute of Innovative Research, Tokyo Institute of Technology , Tokyo 152-8550 , Japan
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5
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Ghosh S, T D, Baul U, Vemparala S. Aggregation dynamics of charged peptides in water: Effect of salt concentration. J Chem Phys 2019; 151:074901. [DOI: 10.1063/1.5100890] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Affiliation(s)
- Susmita Ghosh
- The Institute of Mathematical Sciences, C.I.T. Campus, Taramani, Chennai 600113, India
- Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094, India
| | - Devanand T
- The Institute of Mathematical Sciences, C.I.T. Campus, Taramani, Chennai 600113, India
- Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094, India
| | - Upayan Baul
- Institue of Physics, Albert-Ludwigs-University of Freiburg, Hermann-Herder-Strasse 3, 79104 Freiburg, Germany
| | - Satyavani Vemparala
- The Institute of Mathematical Sciences, C.I.T. Campus, Taramani, Chennai 600113, India
- Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094, India
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6
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Park KC, Tsukahara T. Quantitative Evaluation of Long-Range and Cooperative Ion Effect on Water in Polyamide Network. J Phys Chem B 2019; 123:2948-2955. [PMID: 30888819 DOI: 10.1021/acs.jpcb.9b00717] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Despite long-standing research efforts to elucidate the specific ion effect on the structure and dynamics of water, the spatial extent affected by ions and the cooperativity of ions and counterions are still controversial. Here, we demonstrate an undoubtable evidence of long-range and cooperative ion effect on water molecules in a polyamide network by using a precision ion sensor of photonic crystal hydrogel membrane. The ion effect was quantitatively evaluated by means of the osmotic work per unit cell volume change of photonic crystal, Wunit, required for the ion-inhibited dehydration, which means a suppressed migration of water molecules by the extensive effect of ions beyond their immediate hydration shells. It was found that Wunit required for 14 vol % contraction of the membrane sensor in LiCl aqueous solutions was 7.7 times larger than that in Sr(NO3)2 solutions. The combination of structure-making Ca2+ and Sr2+ with nitrate anions lowered the ion effect than the chloride salts of borderline Na+ and Ba2+. Furthermore, the nitrate salt of Sr2+ exhibited a lower ion effect than the chloride salts of structure-breaking K+ and Cs+. These results have revealed that the ion effect acts to water extensively, which is modulated by cooperative interactions of ions and counterions.
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Affiliation(s)
- Ki Chul Park
- Laboratory for Advanced Nuclear Energy, Institute of Innovative Research , Tokyo Institute of Technology , Tokyo 152-8550 , Japan
| | - Takehiko Tsukahara
- Laboratory for Advanced Nuclear Energy, Institute of Innovative Research , Tokyo Institute of Technology , Tokyo 152-8550 , Japan
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7
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Effects of lyotropic anions on thermodynamic stability and dynamics of horse cytochrome c. Biophys Chem 2018; 240:88-97. [DOI: 10.1016/j.bpc.2018.06.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2018] [Revised: 06/09/2018] [Accepted: 06/10/2018] [Indexed: 11/19/2022]
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8
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Hale CS, Ornelas DN, Yang JS, Chang L, Vang K, Batarseh RN, Ozaki N, Rodgers VGJ. Interrogating the Osmotic Pressure of Self-Crowded Bovine Serum Albumin Solutions: Implications of Specific Monovalent Anion Effects Relative to the Hofmeister Series. J Phys Chem B 2018; 122:8037-8046. [PMID: 30074781 DOI: 10.1021/acs.jpcb.8b07000] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The free-solvent-based (FSB) model and osmotic pressure were used to probe the ion binding and protein hydration for self-crowded bovine serum albumin in 0.15 M NaF, NaCl, NaI, and NaSCN solutions. All experiments were conducted with solutions at pH 7.4. The regressed results of the FSB model behavior to the measured osmotic pressure were excellent, albeit, the osmotic pressure data for NaSCN were noisy. The resulting ion binding and hydration were realistic values and the covariance of the two parameters was exceptionally low, providing substantial credibility to the FSB model. The results showed that the kosmotropic F- and neutral Cl- solutions generated significantly higher ion binding and protein hydration than the chaotropic solutions of I- and SCN-. Further, the ionic strength ratio and resulting hydration implied that the chaotropic solutions had substantially higher aggregation than the other salts investigated. Overall, the FSB model provides an additional, complementary tool to contribute to the analysis of crowded protein solutions relative to anions in the Hofmeister series as it can interrogate crowded solutions directly; something that is not possible with many measurement techniques.
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Affiliation(s)
- Christopher S Hale
- Department of Bioengineering, B2K Group (Biotransport and Bioreaction Kinetics Group) , University of California , Riverside , California 92521 , United States
| | - Danielle N Ornelas
- Department of Bioengineering, B2K Group (Biotransport and Bioreaction Kinetics Group) , University of California , Riverside , California 92521 , United States
| | - Jennifer S Yang
- Department of Bioengineering, B2K Group (Biotransport and Bioreaction Kinetics Group) , University of California , Riverside , California 92521 , United States
| | - Larry Chang
- Department of Bioengineering, B2K Group (Biotransport and Bioreaction Kinetics Group) , University of California , Riverside , California 92521 , United States
| | - Kevin Vang
- Department of Bioengineering, B2K Group (Biotransport and Bioreaction Kinetics Group) , University of California , Riverside , California 92521 , United States
| | - Ramsey N Batarseh
- Department of Bioengineering, B2K Group (Biotransport and Bioreaction Kinetics Group) , University of California , Riverside , California 92521 , United States
| | - Noriko Ozaki
- Department of Bioengineering, B2K Group (Biotransport and Bioreaction Kinetics Group) , University of California , Riverside , California 92521 , United States
| | - Victor G J Rodgers
- Department of Bioengineering, B2K Group (Biotransport and Bioreaction Kinetics Group) , University of California , Riverside , California 92521 , United States
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9
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Silambarasan K, Joseph J. Electrochemical Diagnosis of Chemical Switch: Impact of Structural Changes on Charge Transport Mechanism of “Redox Anion Bound Polysilsesquioxane” Film. ChemElectroChem 2018. [DOI: 10.1002/celc.201800799] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
| | - James Joseph
- Electrodics and Electrocatalysis division; Central Electrochemical Research Institute; Karaikudi India
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11
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Hey JC, Doyle EJ, Chen Y, Johnston RL. Isomers and energy landscapes of micro-hydrated sulfite and chlorate clusters. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2018; 376:rsta.2017.0154. [PMID: 29431682 PMCID: PMC5805918 DOI: 10.1098/rsta.2017.0154] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 11/22/2017] [Indexed: 06/08/2023]
Abstract
We present putative global minima for the micro-hydrated sulfite SO32-(H2O) N and chlorate ClO3-(H2O) N systems in the range 3≤N≤15 found using basin-hopping global structure optimization with an empirical potential. We present a structural analysis of the hydration of a large number of minimized structures for hydrated sulfite and chlorate clusters in the range 3≤N≤50. We show that sulfite is a significantly stronger net acceptor of hydrogen bonding within water clusters than chlorate, completely suppressing the appearance of hydroxyl groups pointing out from the cluster surface (dangling OH bonds), in low-energy clusters. We also present a qualitative analysis of a highly explored energy landscape in the region of the global minimum of the eight water hydrated sulfite and chlorate systems.This article is part of the theme issue 'Modern theoretical chemistry'.
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Affiliation(s)
- John C Hey
- School of Chemistry, University of Birmingham, Birmingham B15 2TT, UK
| | - Emily J Doyle
- School of Chemistry, University of Birmingham, Birmingham B15 2TT, UK
| | - Yuting Chen
- School of Chemistry, University of Birmingham, Birmingham B15 2TT, UK
| | - Roy L Johnston
- School of Chemistry, University of Birmingham, Birmingham B15 2TT, UK
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12
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Zhao J, Wang J. Direct Anionic Effect on Water Structure and Indirect Anionic Effect on Peptide Backbone Hydration State Revealed by Thin-Layer Infrared Spectroscopy. J Phys Chem B 2018; 122:68-76. [PMID: 29232512 DOI: 10.1021/acs.jpcb.7b09591] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this work, the anionic effect on water structure and on the peptide backbone and water interaction was investigated directly in aqueous solution using thin-layer transmission infrared spectroscopy. The chaotropic anions were found to weaken the water hydrogen-bonding strength and red shift the HOH bending frequency, while the kosmotropic anions were found to strengthen the water hydrogen-bonding network and blue shift the HOH bending frequency. The kosmotropes, especially F-, blue shift the vibrational frequencies of both amide II and amide III bands of N-methylacetamide (NMA), indicating NMA is in the "salting-in" state; while the chaotropes (Cl-, NO3-, Br-, I-, and SCN-) red shift the frequencies of the two normal modes, indicating NMA is in the "salting-out" state. Furthermore, the changes of the vibrational frequencies of the HOH bending, amide II and III bands were found to generally follow the Hofmeister anionic series. Our results suggest that hydrated anion influences the peptide backbone mainly through the N-H group, but a weak and indirect effect through the amide C═O group also contributes. Thus, these amide modes can be used as vibrational measures of anionic influences on peptide backbone's hydration state. Our work also suggests that deuteration of the amide unit decreases the sensitivity of the amide II and III vibrational modes in this regard.
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Affiliation(s)
- Juan Zhao
- Beijing National Laboratory for Molecular Sciences; Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, P. R. China.,University of Chinese Academy of Sciences , Beijing 100049, P. R. China
| | - Jianping Wang
- Beijing National Laboratory for Molecular Sciences; Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, P. R. China.,University of Chinese Academy of Sciences , Beijing 100049, P. R. China
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13
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Johnson NO, Light TP, MacDonald G, Zhang Y. Anion–Caffeine Interactions Studied by 13C and 1H NMR and ATR–FTIR Spectroscopy. J Phys Chem B 2017; 121:1649-1659. [DOI: 10.1021/acs.jpcb.6b12150] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Nicolas O. Johnson
- Department of Chemistry and
Biochemistry, James Madison University, Harrisonburg, Virginia 22807, United States
| | - Taylor P. Light
- Department of Chemistry and
Biochemistry, James Madison University, Harrisonburg, Virginia 22807, United States
| | - Gina MacDonald
- Department of Chemistry and
Biochemistry, James Madison University, Harrisonburg, Virginia 22807, United States
| | - Yanjie Zhang
- Department of Chemistry and
Biochemistry, James Madison University, Harrisonburg, Virginia 22807, United States
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14
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Hey JC, Smeeton LC, Oakley MT, Johnston RL. Isomers and Energy Landscapes of Perchlorate-Water Clusters and a Comparison to Pure Water and Sulfate-Water Clusters. J Phys Chem A 2016; 120:4008-15. [PMID: 27223243 DOI: 10.1021/acs.jpca.6b01495] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hydrated ions are crucially important in a wide array of environments, from biology to the atmosphere, and the presence and concentration of ions in a system can drastically alter its behavior. One way in which ions can affect systems is in their interactions with proteins. The Hofmeister series ranks ions by their ability to salt-out proteins, with kosmotropes, such as sulfate, increasing their stability and chaotropes, such as perchlorate, decreasing their stability. We study hydrated perchlorate clusters as they are strongly chaotropic and thus exhibit different properties than sulfate. In this study we simulate small hydrated perchlorate clusters using a basin-hopping geometry optimization search with empirical potentials. We compare topological features of these clusters to data from both computational and experimental studies of hydrated sulfate ions and draw some conclusions about ion effects in the Hofmeister series. We observe a patterning conferred to the water molecules within the cluster by the presence of the perchlorate ion and compare the magnitude of this effect to that observed in previous studies involving sulfate. We also investigate the influence of the overall ionic charge on the low-energy structures adopted by these clusters.
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Affiliation(s)
- John C Hey
- School of Chemistry, University of Birmingham , Edgbaston, Birmingham B15 2TT, U.K
| | - Lewis C Smeeton
- School of Chemistry, University of Birmingham , Edgbaston, Birmingham B15 2TT, U.K
| | - Mark T Oakley
- School of Chemistry, University of Birmingham , Edgbaston, Birmingham B15 2TT, U.K
| | - Roy L Johnston
- School of Chemistry, University of Birmingham , Edgbaston, Birmingham B15 2TT, U.K
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