1
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García-Arnáez I, Romero-Gavilán F, Cerqueira A, Azkargorta M, Elortza F, Suay J, Goñi I, Gurruchaga M. Proteomics as a tool to study the osteoimmunomodulatory role of metallic ions in a sol-gel coating. J Mater Chem B 2023; 11:8194-8205. [PMID: 37552201 DOI: 10.1039/d3tb01204b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/09/2023]
Abstract
The success of bone implants depends on the osteoimmunomodulatory (OIM) activity of the biomaterials in the interactions with the periimplantary tissues. Many in vitro tests have been conducted to evaluate the osteoimmunology effects of biomaterials. However, results of these tests have often been inconclusive. This study examines the properties of newly developed sol-gel coatings doped with two metal ions associated with bone regeneration, Ca and Zn. The study uses both proteomic methods and traditional in vitro assays. The results demonstrate that proteomics is an effective tool to scrutinize the OIM properties of the materials. Moreover, sol-gel coatings offer excellent base materials to evaluate the effects of metal ions on these properties. The obtained data highlight the highly tunable nature of sol-gel materials; studying the materials with different doping levels supplies valuable information on the interactions between the immune and bone-forming processes.
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Affiliation(s)
- Iñaki García-Arnáez
- Departament of Polymers and Advanced Materials: Physics, Chemistry and Technology, Universidad del País Vasco, Po Manuel de Lardizábal, 3, 20018 San Sebastián, Spain.
| | - Francisco Romero-Gavilán
- Department of Industrial Systems Engineering and Design, Universitat Jaume I, Av. Vicent Sos Baynat s/n, 12071 Castellón de la Plana, Spain
| | - Andreia Cerqueira
- Department of Industrial Systems Engineering and Design, Universitat Jaume I, Av. Vicent Sos Baynat s/n, 12071 Castellón de la Plana, Spain
| | - Mikel Azkargorta
- Proteomics Platform, CIC bioGUNE, Basque Research and Technology Alliance (BRTA), CIBERehd, ProteoRed-ISCIII, Bizkaia Science and Technology Park, 48160 Derio, Spain
| | - Félix Elortza
- Proteomics Platform, CIC bioGUNE, Basque Research and Technology Alliance (BRTA), CIBERehd, ProteoRed-ISCIII, Bizkaia Science and Technology Park, 48160 Derio, Spain
| | - Julio Suay
- Department of Industrial Systems Engineering and Design, Universitat Jaume I, Av. Vicent Sos Baynat s/n, 12071 Castellón de la Plana, Spain
| | - Isabel Goñi
- Departament of Polymers and Advanced Materials: Physics, Chemistry and Technology, Universidad del País Vasco, Po Manuel de Lardizábal, 3, 20018 San Sebastián, Spain.
| | - Mariló Gurruchaga
- Departament of Polymers and Advanced Materials: Physics, Chemistry and Technology, Universidad del País Vasco, Po Manuel de Lardizábal, 3, 20018 San Sebastián, Spain.
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2
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Hpone Myint K, Ding W, Willard AP. The Influence of Spectator Cations on Solvent Reorganization Energy Is a Short-Range Effect. J Phys Chem B 2021; 125:1429-1438. [PMID: 33525875 DOI: 10.1021/acs.jpcb.0c09895] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this manuscript, we use classical molecular dynamics simulation to explore the origin of specific cation effects on the rates of bulk-phase aqueous electron transfer (ET) reactions. We consider 0.6 M solutions of Cl- and a series of different cations: Li+, Na+, K+, Rb+, and Cs+. We evaluate the collective electrostatic fluctuations that drive Marcus-like ET and find that they are essentially unaffected by changes in the cationic species. This finding implies that the structure making/breaking properties of various cations do not exert a significant influence on bulk-phase ET reactions. We evaluate the role of ion pairing in these specific cation effects and find, unsurprisingly, that model redox anions that are more highly charged tend to pair more effectively with spectator cations than their monovalent counterparts. We demonstrate that this ion pairing significantly affects local electrostatic fluctuations for the anionic redox species and thus conclude that ion pairing is one of the likely sources of rate-dependent cation effects in aqueous ET reactions.
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Affiliation(s)
- Kyaw Hpone Myint
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Wendu Ding
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Adam P Willard
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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3
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Belousov R, Qaisrani MN, Hassanali A, Roldán É. First-passage fingerprints of water diffusion near glutamine surfaces. SOFT MATTER 2020; 16:9202-9216. [PMID: 32510065 DOI: 10.1039/d0sm00541j] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The extent to which biological interfaces affect the dynamics of water plays a key role in the exchange of matter and chemical interactions that are essential for life. The density and the mobility of water molecules depend on their proximity to biological interfaces and can play an important role in processes such as protein folding and aggregation. In this work, we study the dynamics of water near glutamine surfaces-a system of interest in studies of neurodegenerative diseases. Combining molecular-dynamics simulations and stochastic modelling, we study how the mean first-passage time and related statistics of water molecules escaping subnanometer-sized regions vary from the interface to the bulk. Our analysis reveals a dynamical complexity that reflects underlying chemical and geometrical properties of the glutamine surfaces. From the first-passage time statistics of water molecules, we infer their space-dependent diffusion coefficient in directions normal to the surfaces. Interestingly, our results suggest that the mobility of water varies over a longer length scale than the chemical potential associated with the water-protein interactions. The synergy of molecular dynamics and first-passage techniques opens the possibility for extracting space-dependent diffusion coefficients in more complex, inhomogeneous environments that are commonplace in living matter.
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Affiliation(s)
- Roman Belousov
- ICTP - The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151, Trieste, Italy.
| | - Muhammad Nawaz Qaisrani
- ICTP - The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151, Trieste, Italy. and SISSA - International School for Advanced Studies, Via Bonomea 265, 34136 Trieste, Italy
| | - Ali Hassanali
- ICTP - The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151, Trieste, Italy.
| | - Édgar Roldán
- ICTP - The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151, Trieste, Italy.
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4
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dos Santos AP, Uematsu Y, Rathert A, Loche P, Netz RR. Consistent description of ion-specificity in bulk and at interfaces by solvent implicit simulations and mean-field theory. J Chem Phys 2020; 153:034103. [DOI: 10.1063/5.0016103] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Alexandre P. dos Santos
- Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, 91501-970 Porto Alegre, RS, Brazil
- Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | - Yuki Uematsu
- Department of Physics, Kyushu University, 819-0395 Fukuoka, Japan
| | | | - Philip Loche
- Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | - Roland R. Netz
- Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
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5
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Okur HI, Hladílková J, Rembert KB, Cho Y, Heyda J, Dzubiella J, Cremer PS, Jungwirth P. Beyond the Hofmeister Series: Ion-Specific Effects on Proteins and Their Biological Functions. J Phys Chem B 2017; 121:1997-2014. [PMID: 28094985 DOI: 10.1021/acs.jpcb.6b10797] [Citation(s) in RCA: 423] [Impact Index Per Article: 60.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Ions differ in their ability to salt out proteins from solution as expressed in the lyotropic or Hofmeister series of cations and anions. Since its first formulation in 1888, this series has been invoked in a plethora of effects, going beyond the original salting out/salting in idea to include enzyme activities and the crystallization of proteins, as well as to processes not involving proteins like ion exchange, the surface tension of electrolytes, or bubble coalescence. Although it has been clear that the Hofmeister series is intimately connected to ion hydration in homogeneous and heterogeneous environments and to ion pairing, its molecular origin has not been fully understood. This situation could have been summarized as follows: Many chemists used the Hofmeister series as a mantra to put a label on ion-specific behavior in various environments, rather than to reach a molecular level understanding and, consequently, an ability to predict a particular effect of a given salt ion on proteins in solutions. In this Feature Article we show that the cationic and anionic Hofmeister series can now be rationalized primarily in terms of specific interactions of salt ions with the backbone and charged side chain groups at the protein surface in solution. At the same time, we demonstrate the limitations of separating Hofmeister effects into independent cationic and anionic contributions due to the electroneutrality condition, as well as specific ion pairing, leading to interactions of ions of opposite polarity. Finally, we outline the route beyond Hofmeister chemistry in the direction of understanding specific roles of ions in various biological functionalities, where generic Hofmeister-type interactions can be complemented or even overruled by particular steric arrangements in various ion binding sites.
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Affiliation(s)
- Halil I Okur
- Laboratory for Fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), School of Engineering (STI), École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland
| | - Jana Hladílková
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences , Flemingovo nam. 2, 16610 Prague 6, Czech Republic.,Division of Theoretical Chemistry, Lund University , P.O.B. 124, SE-22100 Lund, Sweden
| | | | - Younhee Cho
- Department of Chemistry, Texas A&M University , College Station 77843, Texas, United States
| | - Jan Heyda
- Institut für Weiche Materie und Funktionale Materialien, Helmholtz-Zentrum Berlin für Materialien und Energie , Hahn-Meitner Platz 1, 14109 Berlin, Germany.,Department of Physical Chemistry, University of Chemistry and Technology, Prague , Technická 5, 16628 Prague 6, Czech Republic
| | - Joachim Dzubiella
- Institut für Weiche Materie und Funktionale Materialien, Helmholtz-Zentrum Berlin für Materialien und Energie , Hahn-Meitner Platz 1, 14109 Berlin, Germany.,Institut für Physik, Humboldt-Universität zu Berlin , Newtonstrasse 15, 12489 Berlin, Germany
| | | | - Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences , Flemingovo nam. 2, 16610 Prague 6, Czech Republic
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6
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The ion–lipid battle for hydration water and interfacial sites at soft-matter interfaces. Curr Opin Colloid Interface Sci 2014. [DOI: 10.1016/j.cocis.2014.02.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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7
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Jas GS, Middaugh CR, Kuczera K. Non-exponential kinetics and a complete folding pathway of an α-helical heteropeptide: direct observation and comprehensive molecular dynamics. J Phys Chem B 2013; 118:639-47. [PMID: 24341828 DOI: 10.1021/jp410934g] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
We have performed a combined experimental and computational study of the folding of a 21-residue α-helix-forming heteropeptide (WH21). Temperature jump kinetics with improved dynamic range at several temperatures revealed non-exponential relaxation that could be well described with two time constants of 20 and 300 ns at 298 K. In the computational part, we performed multi-microsecond molecular dynamics simulations of WH21 in explicit water, using the AMBER03 and OPLS/AA potentials. The simulations were in good agreement with available experimental data on helix content and relaxation times. On the basis of 70 individual transitions, we identified the main pathways of helix unfolding. Three paths were found in both force fields, with unfolding progressing through (1) N-terminus, C-terminus, and center; (2) C-terminus, N-terminus, and center; and (3) C-terminus, center, and N-terminus. An additional fourth path starting in the central region and expanding to the termini was detected only with AMBER03. Intermediate structures sampled along the pathway included a central helix with frayed termini, an off-center helix, and a helical hairpin. The simulations suggest that the short relaxation should be assigned to partly cooperative fluctuations of several neighboring hydrogen bonds. Overall, by a combination of ultrafast kinetic measurements and detailed microscopic description through comprehensive molecular dynamics, we have obtained important new insights into the helix folding process.
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Affiliation(s)
- Gouri S Jas
- Department of Pharmaceutical Chemistry, The University of Kansas , Lawrence, Kansas 66047, United States
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8
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Yoda T, Sugita Y, Okamoto Y. Salt effects on hydrophobic-core formation in folding of a helical miniprotein studied by molecular dynamics simulations. Proteins 2013; 82:933-43. [PMID: 24214490 DOI: 10.1002/prot.24467] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 10/26/2013] [Accepted: 10/29/2013] [Indexed: 11/07/2022]
Abstract
We have investigated effects of salt ions on folding events of a helical miniprotein chicken villin headpiece subdomain HP36. Low concentrations of ions alter electrostatic interactions between charged groups of a protein and can change the populations of conformers. Here, we compare two data sets of folding simulations of HP36 in explicit water solvent with or without ions. For efficient sampling of the conformational space of HP36, the multicanonical replica-exchange molecular dynamics method was employed. Our analyses suggest that salt alters salt-bridging nature of the protein at later stages of folding at room temperature. Especially, more nonnative, nonlocal salt bridges are formed at near-native conformations in pure water. Our analyses also show that such salt-bridge formation hinders the fully native hydrophobic-core packing at the final stages of folding.
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Affiliation(s)
- Takao Yoda
- Nagahama Institute of Bio-Science and Technology, Tamura, Nagahama, Shiga, 526-0829, Japan; RIKEN Advanced Institute for Computational Science, Chuo-ku, Kobe, Hyogo, 650-0047, Japan
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9
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Lutter JC, Wu TY, Zhang Y. Hydration of Cations: A Key to Understanding of Specific Cation Effects on Aggregation Behaviors of PEO-PPO-PEO Triblock Copolymers. J Phys Chem B 2013; 117:10132-41. [DOI: 10.1021/jp405709x] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jacob C. Lutter
- Department of Chemistry and
Biochemistry, James Madison University, Harrisonburg, Virginia 22807, United States
| | - Tsung-yu Wu
- 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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10
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Ioannou F, Leontidis E, Archontis G. Helix Formation by Alanine-Based Peptides in Pure Water and Electrolyte Solutions: Insights from Molecular Dynamics Simulations. J Phys Chem B 2013; 117:9866-76. [DOI: 10.1021/jp406231g] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Filippos Ioannou
- Department
of Chemistry, and ‡Deparment of Physics, University of Cyprus, PO20537, CY1678, Nicosia, Cyprus
| | - Epameinondas Leontidis
- Department
of Chemistry, and ‡Deparment of Physics, University of Cyprus, PO20537, CY1678, Nicosia, Cyprus
| | - Georgios Archontis
- Department
of Chemistry, and ‡Deparment of Physics, University of Cyprus, PO20537, CY1678, Nicosia, Cyprus
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11
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Baldauf C, Pagel K, Warnke S, von Helden G, Koksch B, Blum V, Scheffler M. How Cations Change Peptide Structure. Chemistry 2013; 19:11224-34. [DOI: 10.1002/chem.201204554] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Indexed: 12/12/2022]
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12
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Gaborek TJ, Chipot C, Madura JD. Conformational free-energy landscapes for a peptide in saline environments. Biophys J 2012; 103:2513-20. [PMID: 23260053 DOI: 10.1016/j.bpj.2012.11.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Revised: 10/26/2012] [Accepted: 11/01/2012] [Indexed: 10/27/2022] Open
Abstract
The conformations that proteins adopt in solution are a function of both their primary structure and surrounding aqueous environment. Recent experimental and computational work on small peptides, e.g., polyK, polyE, and polyR, have highlighted an interesting and unusual behavior in the presence of aqueous ions such as ClO₄⁻, Na⁺, and K⁺. Notwithstanding the aforementioned studies, as of this writing, the nature of the driving force induced by the presence of ions and its role on the conformational stability of peptides remains only partially understood. Molecular-dynamics simulations have been performed on the heptapeptide AEAAAEA in NaCl and KCl solutions at concentrations of 0.5, 1.0, and 2.0 M. Metadynamics in conjunction with a three-dimensional model reaction coordinate was used to sample the conformational space of the peptide. All simulations were run for 2 μs. Free-energy landscapes were computed over the model reaction coordinate for the peptide in each saline assay as well as in the absence of ions. Circular dichroism spectra were also calculated from each trajectory. In the presence of Na⁺ and K⁺ ions, no increase in helicity is observed with respect to the conformation in pure water.
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Affiliation(s)
- Timothy J Gaborek
- Department of Chemistry and Biochemistry, Center for Computational Sciences, Duquesne University, Pittsburgh, Pennsylvania, USA.
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13
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Xiong K, Asher SA. Impact of ion binding on poly-L-lysine (un)folding energy landscape and kinetics. J Phys Chem B 2012; 116:7102-12. [PMID: 22612556 PMCID: PMC3381074 DOI: 10.1021/jp302007g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We utilize T-jump UV resonance Raman spectroscopy (UVRR) to study the impact of ion binding on the equilibrium energy landscape and on (un)folding kinetics of poly-L-lysine (PLL). We observe that the relaxation rates of the folded conformations (including π-helix (bulge), pure α-helix, and turns) of PLL are slower than those of short alanine-based peptides. The PLL pure α-helix folding time is similar to that of short alanine-based peptides. We for the first time have directly observed that turn conformations are α-helix and π-helix (bulge) unfolding intermediates. ClO(4)(-) binding to the Lys side chain -NH(3)(+) groups and the peptide backbone slows the α-helix unfolding rate compared to that in pure water, but little impacts the folding rate, resulting in an increased α-helix stability. ClO(4)(-) binding significantly increases the PLL unfolding activation barrier but little impacts the folding barrier. Thus, the PLL folding coordinate(s) differs from the unfolding coordinate(s). The-π helix (bulge) unfolding and folding coordinates do not directly go through the α-helix energy well. Our results clearly demonstrate that PLL (un)folding is not a two-state process.
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Affiliation(s)
- Kan Xiong
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260
| | - Sanford A. Asher
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260
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14
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Collins KD. Why continuum electrostatics theories cannot explain biological structure, polyelectrolytes or ionic strength effects in ion–protein interactions. Biophys Chem 2012; 167:43-59. [DOI: 10.1016/j.bpc.2012.04.002] [Citation(s) in RCA: 169] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2011] [Revised: 04/10/2012] [Accepted: 04/10/2012] [Indexed: 01/13/2023]
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15
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Ion specific influences on the stability and unfolding transitions of a naturally aggregating protein; RecA. Biophys Chem 2012; 163-164:56-63. [DOI: 10.1016/j.bpc.2012.02.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Revised: 02/13/2012] [Accepted: 02/18/2012] [Indexed: 10/28/2022]
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16
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Deublein S, Vrabec J, Hasse H. A set of molecular models for alkali and halide ions in aqueous solution. J Chem Phys 2012; 136:084501. [DOI: 10.1063/1.3687238] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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17
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Crevenna A, Naredi-Rainer N, Lamb D, Wedlich-Söldner R, Dzubiella J. Effects of Hofmeister ions on the α-helical structure of proteins. Biophys J 2012; 102:907-15. [PMID: 22385862 PMCID: PMC3283803 DOI: 10.1016/j.bpj.2012.01.035] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 12/15/2011] [Accepted: 01/11/2012] [Indexed: 01/20/2023] Open
Abstract
The molecular conformation of proteins is sensitive to the nature of the aqueous environment. In particular, the presence of ions can stabilize or destabilize (denature) protein secondary structure. The underlying mechanisms of these actions are still not fully understood. Here, we combine circular dichroism (CD), single-molecule Förster resonance energy transfer, and atomistic computer simulations to elucidate salt-specific effects on the structure of three peptides with large α-helical propensity. CD indicates a complex ion-specific destabilization of the α-helix that can be rationalized by using a single salt-free computer simulation in combination with the recently introduced scheme of ion-partitioning between nonpolar and polar peptide surfaces. Simulations including salt provide a molecular underpinning of this partitioning concept. Furthermore, our single-molecule Förster resonance energy transfer measurements reveal highly compressed peptide conformations in molar concentrations of NaClO(4) in contrast to strong swelling in the presence of GdmCl. The compacted states observed in the presence of NaClO(4) originate from a tight ion-backbone network that leads to a highly heterogeneous secondary structure distribution and an overall lower α-helical content that would be estimated from CD. Thus, NaClO(4) denatures by inducing a molten globule-like structure that seems completely off-pathway between a fully folded helix and a coil state.
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Affiliation(s)
- Alvaro H. Crevenna
- Cellular Dynamics and Cell Patterning, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Nikolaus Naredi-Rainer
- Physical Chemistry, Department for Chemistry and Biochemistry and Center for Nano Science (CeNS), Ludwig-Maximilians-Universität München, Munich, Germany
- Center for Integrated Protein Science Munich, Munich, Germany
| | - Don C. Lamb
- Physical Chemistry, Department for Chemistry and Biochemistry and Center for Nano Science (CeNS), Ludwig-Maximilians-Universität München, Munich, Germany
- Center for Integrated Protein Science Munich, Munich, Germany
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Roland Wedlich-Söldner
- Cellular Dynamics and Cell Patterning, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Joachim Dzubiella
- Physics Department T37, Technische Universität München, Garching, Germany
- Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin, Berlin, Germany
- Institut für Physik, Humboldt-Universität zu Berlin, Berlin, Germany
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18
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Ma L, Hong Z, Sharma B, Asher S. UV resonance Raman studies of the NaClO4 dependence of poly-L-lysine conformation and hydrogen exchange kinetics. J Phys Chem B 2012; 116:1134-42. [PMID: 22117822 PMCID: PMC3266997 DOI: 10.1021/jp208918n] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We used 204 nm excitation UV Resonance Raman (UVRR) spectroscopy to examine the effects of NaClO(4) on the conformation of poly-L-lysine (PLL). The presence of NaClO(4) induces the formation of α-helix, π-helix/bulge, and turn conformations. The dependence of the AmIII(3) frequency on the peptide Ψ Ramachandran angle allows us to experimentally determine the conformational population distributions and the energy landscape of PLL along the Ramachandran Ψ angle. We also used UVRR to measure the NaClO(4) concentration dependence of PLL amide hydrogen exchange kinetics. Exchange rates were determined by fitting the D(2)O exchanging PLL UVRR AmII' band time evolution. Hydrogen exchange is slowed at high NaClO(4) concentrations. The PLL AmII' band exchange kinetics at 0.0, 0.2, and 0.35 M NaClO(4) can be fit by single exponentials, but the AmII' band kinetics of PLL at 0.8 M NaClO(4) requires a double exponential fit. The exchange rates for the extended conformations were monitored by measuring the C(α)-H band kinetics. These kinetics are identical to those of the AmII' band until 0.8 M NaClO(4) whereupon the extended conformation exchange becomes clearly faster than that of the α-helix-like conformations. Our results indicate that ClO(4)(-) binds to the PLL backbone to protect it from OH(-) exchange catalysis. In addition, ClO(4)(-) binding also slows the conformational exchange between the extended and α-helix-like conformations, probably by increasing the activation barriers for conformational interchanges.
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Affiliation(s)
- Lu Ma
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, Tel: (412)-624-8570, Fax: (412)-624-0588
| | - Zhenmin Hong
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, Tel: (412)-624-8570, Fax: (412)-624-0588
| | - Bhavya Sharma
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, Tel: (412)-624-8570, Fax: (412)-624-0588
| | - Sanford Asher
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, Tel: (412)-624-8570, Fax: (412)-624-0588
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19
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Conformation of poly-L-glutamate is independent of ionic strength. Biophys Chem 2011; 162:1-5. [PMID: 22236769 DOI: 10.1016/j.bpc.2011.11.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 11/08/2011] [Accepted: 11/12/2011] [Indexed: 11/23/2022]
Abstract
CD and UV resonance Raman measurements surprisingly find that the charge screening of even 2 M concentrations of NaCl and KCl does not alter the unfolded PPII and 2.5(1)-helix conformations of poly-L-glutamate. These salts appear to be excluded from the region between the side chain charges and the peptide backbone. Furthermore, no direct ion pairing occurs between these salts and the side chain carboxylates.
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20
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von Hansen Y, Sedlmeier F, Hinczewski M, Netz RR. Friction contribution to water-bond breakage kinetics. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:051501. [PMID: 22181416 DOI: 10.1103/physreve.84.051501] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Revised: 09/14/2011] [Indexed: 05/31/2023]
Abstract
Based on the trajectories of the separation between water molecule pairs from MD simulations, we investigate the bond breakage dynamics in bulk water. From the spectrum of mean first-passage times, the Fokker-Planck equation allows us to derive the diffusivity profile along the separation coordinate and thus to unambiguously disentangle the effects of free-energy and local friction on the separation kinetics. For tightly coordinated water, the friction is six times higher than in bulk, which can be interpreted in terms of a dominant reaction path that involves additional orthogonal coordinates.
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Affiliation(s)
- Yann von Hansen
- Physik Department, Technische Universität München, D-85748 Garching, Germany
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Ioannou F, Archontis G, Leontidis E. Specific interactions of sodium salts with alanine dipeptide and tetrapeptide in water: insights from molecular dynamics. J Phys Chem B 2011; 115:13389-400. [PMID: 21978277 DOI: 10.1021/jp207068m] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
We examine computationally the dipeptide and tetrapeptide of alanine in pure water and solutions of sodium chloride (NaCl) and iodide (NaI), with salt concentrations up to 3 M. Enhanced sampling of the configuration space is achieved by the replica exchange method. In agreement with other works, we observe preferential sodium interactions with the peptide carbonyl groups, which are enhanced in the NaI solutions due to the increased affinity of the less hydrophilic iodide anion for the peptide methyl side-chains and terminal blocking groups. These interactions have been associated with a decrease in the helicities of more complex peptides. In our simulations, both salts have a small effect on the dipeptide, but consistently stabilize the intramolecular hydrogen-bonding interactions and "α-helical" conformations of the tetrapeptide. This behavior, and an analysis of the intermolecular interaction energies show that ion-peptide interactions, or changes in the peptide hydration due to salts, are not sufficient determining factors of the peptide conformational preferences. Additional simulations suggest that the observed stabilizing effect is not due to the employed force-field, and that it is maintained in short peptides but is reversed in longer peptides. Thus, the peptide conformational preferences are determined by an interplay of energetic and entropic factors, arising from the peptide sequence and length and the composition of the solution.
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