151
|
Kwong RWM, Perry SF. Cortisol regulates epithelial permeability and sodium losses in zebrafish exposed to acidic water. J Endocrinol 2013; 217:253-64. [PMID: 23503775 DOI: 10.1530/joe-12-0574] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The effects of cortisol on epithelial permeability and sodium (Na(+)) handling during acid exposure were investigated in larval zebrafish (Danio rerio). The results demonstrated that the whole-body absorption of the paracellular permeability marker polyethylene glycol-4000 (PEG-4000) decreased with increasing levels of exogenous cortisol. Western blot analysis revealed that the abundance of the epithelial tight junction proteins occludin-a and claudin-b was increased after cortisol treatment. Furthermore, translational gene knockdown of claudin-b using an antisense morpholino oligonucleotide caused an increase in the permeability to PEG-4000, which was mitigated by cortisol treatment, further suggesting a role for cortisol in reducing paracellular permeability. Exposure to acidic water (pH 4.0 vs 7.6) caused an expected increase in the diffusive loss of Na(+) and a decrease in whole-body Na(+) levels. These disruptive effects of acute acid exposure on Na(+) balance were reduced by treatment of larvae with exogenous cortisol. Translational knockdown of the glucocorticoid receptor (GR) abolished the effects of cortisol on epithelial PEG permeability, suggesting that activation of GR was probably the major signaling pathway for reducing epithelial permeability. During acid exposure, the epithelial PEG permeability in the GR morphants was significantly higher than in the control fish. Additionally, GR morphants exhibited a more pronounced diffusive loss of Na(+) than the control fish during acid exposure. These findings suggest that cortisol may help to minimize the negative consequences of acid exposure on Na(+) homoeostasis via GR-mediated reductions in epithelial permeability and paracellular Na(+) loss.
Collapse
Affiliation(s)
- Raymond W M Kwong
- Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, Ontario, Canada K1N 6N5.
| | | |
Collapse
|
152
|
Nguyen NC, Chen SS, Yang HY, Hau NT. Application of forward osmosis on dewatering of high nutrient sludge. BIORESOURCE TECHNOLOGY 2013; 132:224-229. [PMID: 23411452 DOI: 10.1016/j.biortech.2013.01.028] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 12/30/2012] [Accepted: 01/05/2013] [Indexed: 06/01/2023]
Abstract
A novel approach was designed to simultaneously apply low energy sludge dewatering and nutrient removal for activated sludge using forward osmosis (FO). In this study, the municipal wastewater sludge was spiked with different nutrient concentrations to evaluate FO dewatering performance. The results showed that sludge concentration reached 21,511 and 28,500mg/L after 28h from initial sludge concentration of 3000 and 8000mg/L with flow rate of 150mL/min. Moreover, nutrient and organic compounds in sludge solution were also successfully removed (around 96% of NH4(+)-N, 98% of PO4(3-)-P and 99% of dissolved organic carbon (DOC)) due to steric effect of FO membrane and multi barrier layer of sludge forming on membrane surface. Furthermore, the analysis from Scanning Electron Microscopy & Energy Dispersive X-ray Spectroscopy (SEM-EDS) images recorded that FO membrane was fouled by cake layer of sludge in the active layer and NaCl in the support layer.
Collapse
Affiliation(s)
- Nguyen Cong Nguyen
- Institute of Environmental Engineering and Management, National Taipei University of Technology, No. 1, Sec. 3, Chung-Hsiao E. Rd, Taipei 106, Taiwan, ROC
| | | | | | | |
Collapse
|
153
|
Gilles A, Mihai S, Nasr G, Mahon E, Garai S, Müller A, Barboiu M. Highly Selective Li
+
Ion Transport by Porous Molybdenum‐Oxide Keplerate‐Type Nanocapsules Integrated in a Supported Liquid Membrane. Isr J Chem 2013. [DOI: 10.1002/ijch.201300001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Arnaud Gilles
- Adaptive Supramolecular Nanosystems Group, Institut Européen des Membranes ‐ENSCM/UM2/CNRS 5635, IEM/UM II, CC 047, Place Eugène Bataillon, 34095, Montpellier, Cedex 5 (France) fax: +33‐467‐14‐91‐19
| | - Simona Mihai
- Adaptive Supramolecular Nanosystems Group, Institut Européen des Membranes ‐ENSCM/UM2/CNRS 5635, IEM/UM II, CC 047, Place Eugène Bataillon, 34095, Montpellier, Cedex 5 (France) fax: +33‐467‐14‐91‐19
| | - Gihane Nasr
- Adaptive Supramolecular Nanosystems Group, Institut Européen des Membranes ‐ENSCM/UM2/CNRS 5635, IEM/UM II, CC 047, Place Eugène Bataillon, 34095, Montpellier, Cedex 5 (France) fax: +33‐467‐14‐91‐19
| | - Eugene Mahon
- Adaptive Supramolecular Nanosystems Group, Institut Européen des Membranes ‐ENSCM/UM2/CNRS 5635, IEM/UM II, CC 047, Place Eugène Bataillon, 34095, Montpellier, Cedex 5 (France) fax: +33‐467‐14‐91‐19
| | - Somenath Garai
- Universität Bielefeld, Fakultät für Chemie, Postfach 10 01 31, 33501 Bielefeld (Germany)
| | - Achim Müller
- Universität Bielefeld, Fakultät für Chemie, Postfach 10 01 31, 33501 Bielefeld (Germany)
| | - Mihail Barboiu
- Adaptive Supramolecular Nanosystems Group, Institut Européen des Membranes ‐ENSCM/UM2/CNRS 5635, IEM/UM II, CC 047, Place Eugène Bataillon, 34095, Montpellier, Cedex 5 (France) fax: +33‐467‐14‐91‐19
| |
Collapse
|
154
|
Xu M, Sullivan K, Vanness G, Knauss KG, Higgins SR. Dissolution kinetics and mechanisms at dolomite-water interfaces: effects of electrolyte specific ionic strength. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:110-118. [PMID: 22681699 DOI: 10.1021/es301284h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Elucidating dissolution kinetics and mechanisms at carbonate mineral-water interfaces is essential to many environmental and geochemical processes, including geologic CO(2) sequestration in deep aquifers. In the present work, effects of background electrolytes on dolomite (CaMg(CO(3))(2)) reactivity were investigated by measuring step dissolution rates using in situ hydrothermal atomic force microscopy (HAFM) at 90 °C. Cleaved surfaces of dolomite were exposed to sodium chloride and tetramethylammonium chloride (TMACl) aqueous solutions with ionic strengths (I) ranging from 0 to 0.77 m at pH 4 and pH 9. HAFM results demonstrated that dolomite step retreat rates increased with increasing solution ionic strength and decreasing pH. Comparison of [481] and [441] steps revealed that the anisotropy of [481] and [441] step speeds became significant as solution ionic strength increased, with NaCl exerting more pronounced effects than TMACl for the same I. To interpret the different trends observed for NaCl and TMACl, a dissolution mechanism involving orientation-dependent ion adsorption and consequent edge free energy changes is proposed.
Collapse
Affiliation(s)
- Man Xu
- Department of Chemistry, Wright State University, 3640 Colonel Glenn Highway, Dayton, Ohio 45435, United States
| | | | | | | | | |
Collapse
|
155
|
|
156
|
Ge L, Bernasconi L, Hunt P. Linking electronic and molecular structure: insight into aqueous chloride solvation. Phys Chem Chem Phys 2013; 15:13169-83. [DOI: 10.1039/c3cp50652e] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
|
157
|
Yin J, Kim ES, Yang J, Deng B. Fabrication of a novel thin-film nanocomposite (TFN) membrane containing MCM-41 silica nanoparticles (NPs) for water purification. J Memb Sci 2012. [DOI: 10.1016/j.memsci.2012.08.020] [Citation(s) in RCA: 340] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
158
|
Airoldi M, Gennaro G, Giomini M, Giuliani AM, Giustini M. Effect of the alkaline cations on the stability of the model polynucleotide poly(dG-dC)·poly(dG-dC). J Biomol Struct Dyn 2012; 29:585-94. [PMID: 22066543 DOI: 10.1080/07391102.2011.10507407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
When the model polynucleotide poly(dG-dC)∙poly(dG-dC) [polyGC] is titrated with a strong acid (HCl) in unbuffered aqueous solutions containing the chlorides of the alkali metals in the concentration range 0.010 M-0.600 M, two transitions in the absorbance vs. pH plots are evidenced, characterized by the constants pK(a(₁)) and pK(a(₂)). The limiting values at infinite saline concentrations of these two constants, namely pK(∞)(a(₁)) and pK(∞)(a(₂)) obtained making use of the "one site saturation constant" equation or, in turn, of the double logarithmic plot: pK(a) vs. log([salt]⁻¹), exhibit a clear dependence on the nature of the cations. The effects of the different alkali cations on the pK(∞)(a) values follow the Hofmeister series. In fact, the pK(∞)(a(₁)) and the pK(∞)(a(₂)) values are smaller for Li+ and Na+ than for Rb+ and Cs+, with K+ at the border between the two, showing that the transitions require higher concentrations of protons to occur in the presence of high concentrations of the cosmotropic ions.
Collapse
Affiliation(s)
- Marta Airoldi
- Dipartimento di Chimica "S. Cannizzaro", Universita di Palermo, Viale delle Scienze, Pad. 17, 90128 Palermo, Italy
| | | | | | | | | |
Collapse
|
159
|
Tran AT, Zhang Y, Jullok N, Meesschaert B, Pinoy L, Van der Bruggen B. RO concentrate treatment by a hybrid system consisting of a pellet reactor and electrodialysis. Chem Eng Sci 2012. [DOI: 10.1016/j.ces.2012.06.001] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
|
160
|
Zhang T, Mu Y. Initial binding of ions to the interhelical loops of divalent ion transporter CorA: replica exchange molecular dynamics simulation study. PLoS One 2012; 7:e43872. [PMID: 22952795 PMCID: PMC3431404 DOI: 10.1371/journal.pone.0043872] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Accepted: 07/26/2012] [Indexed: 01/03/2023] Open
Abstract
Crystal structures of Thermotoga maritima magnesium transporter CorA, reported in 2006, revealed its homo-pentameric constructions. However, the structure of the highly conserved extracellular interhelical loops remains unsolved, due to its high flexibility. We have explored the configurations of the loops through extensive replica exchange molecular dynamics simulations in explicit solvent model with the presence of either Co(III) Hexamine ions or Mg(2+) ions. We found that there are multiple binding sites available on the interhelical loops in which the negatively charged residues, E316 and E320, are located notably close to the positively charged ions during the simulations. Our simulations resolved the distinct binding patterns of the two kinds of ions: Co(III) Hexamine ions were found to bind stronger with the loop than Mg(2+) ions with binding free energy -7.3 kJ/mol lower, which is nicely consistent with the previous data. Our study provides an atomic basis description of the initial binding process of Mg(2+) ions on the extracellular interhelical loops of CorA and the detailed inhibition mechanism of Co(III) Hexamine ions on CorA ions transportation.
Collapse
Affiliation(s)
- Tong Zhang
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Yuguang Mu
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| |
Collapse
|
161
|
Liu CK, Warr GG. Resiliently spherical micelles of alkyltrimethylammonium surfactants with multivalent, hydrolyzable counterions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:11007-11016. [PMID: 22642511 DOI: 10.1021/la301378j] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A series of C(12)-C(16) alkyltrimethylammonium surfactants with hydrolyzable phosphate (PO(4)(3-), HPO(4)(2-), and H(2)PO(4)(-)), oxalate (HC(2)O(4)(-) and C(2)O(4)(2-)), and carbonate (HCO(3)(-) and CO(3)(2-)) counterions have been prepared, and their micellar solution behavior has been characterized. Critical micelle concentrations were measured using electrical conductivity and were found to depend on both the counterion and its hydrolysis state. All monovalent counterions bind less strongly to the micelle surface than does bromide or chloride, whereas multivalent species bind more strongly. Small-angle neutron scattering reveals that, unlike alkyltrimethylammonium bromides and chlorides, micelles are small and spherical in the presence of hydrolyzable counterions of all valences and remain spherical even in the presence of added electrolyte. This is consistent with the strong solvation of even strongly bound hydrolyzable counterions, which prevents the screening of repulsions between adjacent headgroups necessary for sphere-cylinder transformations. Salts of multivalent hydrolyzable counterions could thus be used to control the micelle structure in novel ways.
Collapse
Affiliation(s)
- Connie K Liu
- School of Chemistry F11, The University of Sydney, NSW, Australia
| | | |
Collapse
|
162
|
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]
|
163
|
Dubiel EA, Vermette P. Solution composition impacts fibronectin immobilization on carboxymethyl-dextran surfaces and INS-1 insulin secretion. Colloids Surf B Biointerfaces 2012; 95:266-73. [DOI: 10.1016/j.colsurfb.2012.03.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Revised: 02/20/2012] [Accepted: 03/12/2012] [Indexed: 12/19/2022]
|
164
|
Hasuike M, Kuroki S, Satoh M. Double conformational transition of alkali metal poly(l-glutamate)s in aqueous ethanol. Biophys Chem 2012; 165-166:48-55. [DOI: 10.1016/j.bpc.2012.03.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 03/06/2012] [Accepted: 03/06/2012] [Indexed: 11/25/2022]
|
165
|
Luo J, Huang W, Song W, Hang X, Ding L, Wan Y. A pilot-plant test on desalination of soy sauce by nanofiltration. Sep Purif Technol 2012. [DOI: 10.1016/j.seppur.2012.01.026] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
|
166
|
Tansel B. Significance of thermodynamic and physical characteristics on permeation of ions during membrane separation: Hydrated radius, hydration free energy and viscous effects. Sep Purif Technol 2012. [DOI: 10.1016/j.seppur.2011.10.033] [Citation(s) in RCA: 278] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
|
167
|
Kaur S, Sundarrajan S, Gopal R, Ramakrishna S. Formation and characterization of polyamide composite electrospun nanofibrous membranes for salt separation. J Appl Polym Sci 2012. [DOI: 10.1002/app.36375] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
168
|
Liu M, Bertova A, Illy N, Brissault B, Penelle J, Ondrias K, Barbier V. A polymeric membrane permeabilizer displaying densely packed arrays of crown ether lateral substituents. RSC Adv 2012. [DOI: 10.1039/c2ra20548c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
169
|
Jafeen MJM, Careem MA, Skaarup S. A novel method for the determination of membrane hydration numbers of cations in conducting polymers. J Solid State Electrochem 2011. [DOI: 10.1007/s10008-011-1594-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
170
|
Merenbloom SI, Flick TG, Daly MP, Williams ER. Effects of select anions from the Hofmeister series on the gas-phase conformations of protein ions measured with traveling-wave ion mobility spectrometry/mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2011; 22:1978-90. [PMID: 21952780 PMCID: PMC3212098 DOI: 10.1007/s13361-011-0238-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Revised: 08/19/2011] [Accepted: 08/19/2011] [Indexed: 05/10/2023]
Abstract
The gas-phase conformations of ubiquitin, cytochrome c, lysozyme, and α-lactalbumin ions, formed by electrospray ionization (ESI) from aqueous solutions containing 5 mM ammonium perchlorate, ammonium iodide, ammonium sulfate, ammonium chloride, ammonium thiocyanate, or guanidinium chloride, are examined using traveling-wave ion mobility spectrometry (TWIMS) coupled to time-of-flight (TOF) mass spectrometry (MS). For ubiquitin, cytochrome c, and α-lactalbumin, adduction of multiple acid molecules results in no significant conformational changes to the highest and lowest charge states formed from aqueous solutions, whereas the intermediate charge states become more compact. The transition to more compact conformers for the intermediate charge states occurs with fewer bound H(2)SO(4) molecules than HClO(4) or HI molecules, suggesting ion-ion or salt-bridge interactions are stabilizing more compact forms of the gaseous protein. However, the drift time distributions for protein ions of the same net charge with the highest levels of adduction of each acid are comparable, indicating that these protein ions all adopt similarly compact conformations or families of conformers. No significant change in conformation is observed upon the adduction of multiple acid molecules to charge states of lysozyme. These results show that the attachment of HClO(4), HI, or H(2)SO(4) to multiply protonated proteins can induce compact conformations in the resulting gas-phase protein ions. In contrast, differing Hofmeister effects are observed for the corresponding anions in solution at higher concentrations.
Collapse
Affiliation(s)
- Samuel I. Merenbloom
- Department of Chemistry, University of California-Berkeley, Berkeley, California, USA
| | - Tawnya G. Flick
- Department of Chemistry, University of California-Berkeley, Berkeley, California, USA
| | | | - Evan R. Williams
- Department of Chemistry, University of California-Berkeley, Berkeley, California, USA
| |
Collapse
|
171
|
Divalent cation-dependent formation of electrostatic PIP2 clusters in lipid monolayers. Biophys J 2011; 101:2178-84. [PMID: 22067156 DOI: 10.1016/j.bpj.2011.09.039] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Revised: 08/30/2011] [Accepted: 09/19/2011] [Indexed: 11/22/2022] Open
Abstract
Polyphosphoinositides are among the most highly charged molecules in the cell membrane, and the most common polyphosphoinositide, phosphatidylinositol-4,5-bisphosphate (PIP(2)), is involved in many mechanical and biochemical processes in the cell membrane. Divalent cations such as calcium can cause clustering of the polyanionic PIP(2), but the origin and strength of the effective attractions leading to clustering has been unclear. In addition, the question of whether the ion-mediated attractions could be strong enough to alter the mechanical properties of the membrane, to our knowledge, has not been addressed. We study phase separation in mixed monolayers of neutral and highly negatively charged lipids, induced by the addition of divalent positively charged counterions, both experimentally and numerically. We find good agreement between experiments on mixtures of PIP(2) and 1-stearoyl-2-oleoyl phosphatidylcholine and simulations of a simplified model in which only the essential electrostatic interactions are retained. In addition, we find numerically that under certain conditions the effective attractions can rigidify the resulting clusters. Our results support an interpretation of PIP(2) clustering as governed primarily by electrostatic interactions. At physiological pH, the simulations suggest that the effective attractions are strong enough to give nearly pure clusters of PIP(2) even at small overall concentrations of PIP(2).
Collapse
|
172
|
Kim SG, Chung JS, Sutton RB, Lee JS, López-Maury L, Lee SY, Florencio FJ, Lin T, Zabet-Moghaddam M, Wood MJ, Nayak K, Madem V, Tripathy JN, Kim SK, Knaff DB. Redox, mutagenic and structural studies of the glutaredoxin/arsenate reductase couple from the cyanobacterium Synechocystis sp. PCC 6803. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1824:392-403. [PMID: 22155275 DOI: 10.1016/j.bbapap.2011.10.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 10/12/2011] [Accepted: 10/17/2011] [Indexed: 10/15/2022]
Abstract
The arsenate reductase from the cyanobacterium Synechocystis sp. PCC 6803 has been characterized in terms of the redox properties of its cysteine residues and their role in the reaction catalyzed by the enzyme. Of the five cysteines present in the enzyme, two (Cys13 and Cys35) have been shown not to be required for catalysis, while Cys8, Cys80 and Cys82 have been shown to be essential. The as-isolated enzyme contains a single disulfide, formed between Cys80 and Cys82, with an oxidation-reduction midpoint potential (E(m)) value of -165mV at pH 7.0. It has been shown that Cys15 is the only one of the four cysteines present in Synechocystis sp. PCC 6803 glutaredoxin A required for its ability to serve as an electron donor to arsenate reductase, while the other three cysteines (Cys18, Cys36 and Cys70) play no role. Glutaredoxin A has been shown to contain a single redox-active disulfide/dithiol couple, with a two-electron, E(m) value of -220mV at pH 7.0. One cysteine in this disulfide/dithiol couple has been shown to undergo glutathionylation. An X-ray crystal structure, at 1.8Å resolution, has been obtained for glutaredoxin A. The probable orientations of arsenate reductase disulfide bonds present in the resting enzyme and in a likely reaction intermediate of the enzyme have been examined by in silico modeling, as has the surface environment of arsenate reductase in the vicinity of Cys8, the likely site for the initial reaction between arsenate and the enzyme.
Collapse
Affiliation(s)
- Sang Gon Kim
- Department of Chemistry and Biochemistry and the Institute of Biomedical Studies, Baylor University, Waco, TX 76798-7348, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
173
|
Airoldi M, Gennaro G, Giomini M, Giuliani AM, Giustini M. Effect of the Alkaline Cations on the Stability of the Model Polynucleotide Poly(dG-dC)·Poly(dG-dC). J Biomol Struct Dyn 2011. [DOI: 10.1080/07391102.2011.10507395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
|
174
|
Waluyo I, Huang C, Nordlund D, Weiss TM, Pettersson LGM, Nilsson A. Increased fraction of low-density structures in aqueous solutions of fluoride. J Chem Phys 2011; 134:224507. [PMID: 21682525 DOI: 10.1063/1.3597606] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
X-ray absorption spectroscopy (XAS) and small angle x-ray scattering (SAXS) were utilized to study the effect of fluoride (F(-)) anion in aqueous solutions. XAS spectra show that F(-) increases the number of strong H-bonds, likely between F(-) and water in the first hydration shell. SAXS data show a low-Q scattering intensity increase similar to the effect of a temperature decrease, suggesting an enhanced anomalous scattering behavior in F(-) solutions. Quantitative analysis revealed that fluoride solutions have larger correlation lengths than chloride solutions with the same cations but shorter compared to pure water. This is interpreted as an increased fraction of tetrahedral low-density structures in the solutions due to the presence of the F(-) ions, which act as nucleation centers replacing water in the H-bonding network and forming stronger H-bonds, but the presence of the cations restricts the extension of strong H-bonds.
Collapse
Affiliation(s)
- Iradwikanari Waluyo
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | | | | | | | | | | |
Collapse
|
175
|
Zhao S, Zou L. Relating solution physicochemical properties to internal concentration polarization in forward osmosis. J Memb Sci 2011. [DOI: 10.1016/j.memsci.2011.06.021] [Citation(s) in RCA: 163] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
|
176
|
Le Duc Y, Michau M, Gilles A, Gence V, Legrand YM, van der Lee A, Tingry S, Barboiu M. Imidazole-Quartet Water and Proton Dipolar Channels. Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201103312] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
|
177
|
Le Duc Y, Michau M, Gilles A, Gence V, Legrand YM, van der Lee A, Tingry S, Barboiu M. Imidazole-Quartet Water and Proton Dipolar Channels. Angew Chem Int Ed Engl 2011; 50:11366-72. [DOI: 10.1002/anie.201103312] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2011] [Indexed: 01/11/2023]
|
178
|
Khoutorsky A, Heyman A, Shoseyov O, Spira ME. Formation of hydrophilic nanochannels in the membrane of living cells by the ringlike stable protein-SP1. NANO LETTERS 2011; 11:2901-4. [PMID: 21651305 DOI: 10.1021/nl201368w] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The assembly of functional junction between nerve cells and electronic sensing pads is a critical problem in the construction of effective neuroelectronic hybrid systems. Here, we demonstrate for the first time that the ringlike Stable Protein 1 (Sp1) and its derivatives can be used to generate hydrophilic nanochannels in the plasma membrane of living cells. Since SP1-derivatives can be linked to both the plasma membrane, gold or silicon surfaces, they may serve to ohmically link between cells interior and electronic sensing devices.
Collapse
Affiliation(s)
- Arkady Khoutorsky
- Department of Neurobiology, The Life Sciences Institute, Faculty of Science, Hebrew University of Jerusalem, Israel
| | | | | | | |
Collapse
|
179
|
Geng Y, Niu X, Magleby KL. Low resistance, large dimension entrance to the inner cavity of BK channels determined by changing side-chain volume. ACTA ACUST UNITED AC 2011; 137:533-48. [PMID: 21576375 PMCID: PMC3105516 DOI: 10.1085/jgp.201110616] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Large-conductance Ca2+- and voltage-activated K+ (BK) channels have the largest conductance (250–300 pS) of all K+-selective channels. Yet, the contributions of the various parts of the ion conduction pathway to the conductance are not known. Here, we examine the contribution of the entrance to the inner cavity to the large conductance. Residues at E321/E324 on each of the four α subunits encircle the entrance to the inner cavity. To determine if 321/324 is accessible from the inner conduction pathway, we measured single-channel current amplitudes before and after exposure and wash of thiol reagents to the intracellular side of E321C and E324C channels. MPA− increased currents and MTSET+ decreased currents, with no difference between positions 321 and 324, indicating that side chains at 321/324 are accessible from the inner conduction pathway and have equivalent effects on conductance. For neutral amino acids, decreasing the size of the entrance to the inner cavity by substituting large side-chain amino acids at 321/324 decreased outward single-channel conductance, whereas increasing the size of the entrance with smaller side-chain substitutions had little effect. Reductions in outward conductance were negated by high [K+]i. Substitutions had little effect on inward conductance. Fitting plots of conductance versus side-chain volume with a model consisting of one variable and one fixed resistor in series indicated an effective diameter and length of the entrance to the inner cavity for wild-type channels of 17.7 and 5.6 Å, respectively, with the resistance of the entrance ∼7% of the total resistance of the conduction pathway. The estimated dimensions are consistent with the structure of MthK, an archaeal homologue to BK channels. Our observations suggest that BK channels have a low resistance, large entrance to the inner cavity, with the entrance being as large as necessary to not limit current, but not much larger.
Collapse
Affiliation(s)
- Yanyan Geng
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, FL 33136, USA. ygeng@-med.miami.edu
| | | | | |
Collapse
|
180
|
Effect of highly concentrated salt on retention of organic solutes by nanofiltration polymeric membranes. J Memb Sci 2011. [DOI: 10.1016/j.memsci.2011.01.066] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
181
|
Pervaporative seawater desalination using NaA zeolite membrane: Mechanisms of high water flux and high salt rejection. J Memb Sci 2011. [DOI: 10.1016/j.memsci.2011.01.049] [Citation(s) in RCA: 136] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
182
|
Xu J, Feng X, Gao C. Surface modification of thin-film-composite polyamide membranes for improved reverse osmosis performance. J Memb Sci 2011. [DOI: 10.1016/j.memsci.2011.01.001] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
183
|
Richards LA, Richards BS, Schäfer AI. Renewable energy powered membrane technology: Salt and inorganic contaminant removal by nanofiltration/reverse osmosis. J Memb Sci 2011. [DOI: 10.1016/j.memsci.2010.11.069] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
|
184
|
Waluyo I, Huang C, Nordlund D, Bergmann U, Weiss TM, Pettersson LGM, Nilsson A. The structure of water in the hydration shell of cations from x-ray Raman and small angle x-ray scattering measurements. J Chem Phys 2011; 134:064513. [PMID: 21322711 PMCID: PMC3188634 DOI: 10.1063/1.3533958] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Accepted: 12/15/2010] [Indexed: 01/13/2023] Open
Abstract
X-ray Raman scattering (XRS) spectroscopy and small angle x-ray scattering (SAXS) are used to study water in aqueous solutions of NaCl, MgCl(2), and AlCl(3) with the particular aim to provide information about the structure of the hydration shells of the cations. The XRS spectra show that Na(+) weakens the hydrogen bonds of water molecules in its vicinity, similar to the effect of increased temperature and pressure. Mg(2+) and Al(3+), on the other hand, cause the formation of short and strong hydrogen bonds between the surrounding water molecules. The SAXS data show that Mg(2+) and Al(3+) form tightly bound hydration shells that give a large density contrast in the scattering data. From the form factors extracted from the SAXS data, we found that Mg(2+) and Al(3+) have, respectively, an equivalent of one and one and a half stable hydration shells that appear as a density contrast. In addition, we estimated that the density of water in the hydration shells of Mg(2+) and Al(3+) is, respectively, ∼61% and ∼71% higher than in bulk water.
Collapse
Affiliation(s)
- Iradwikanari Waluyo
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | | | | | | | | | | | | |
Collapse
|
185
|
Ren CL, Tian WD, Szleifer I, Ma YQ. Specific Salt Effects on Poly(ethylene oxide) Electrolyte Solutions. Macromolecules 2011. [DOI: 10.1021/ma1027752] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Chun-lai Ren
- National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China
| | - Wen-de Tian
- Center for Soft Condensed Matter Physics and Interdisciplinary Research, Soochow University, Suzhou 215006, China
| | - Igal Szleifer
- Department of Biomedical Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Yu-qiang Ma
- National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China
- Center for Soft Condensed Matter Physics and Interdisciplinary Research, Soochow University, Suzhou 215006, China
| |
Collapse
|
186
|
Levi MD, Sigalov S, Salitra G, Elazari R, Aurbach D. Assessing the Solvation Numbers of Electrolytic Ions Confined in Carbon Nanopores under Dynamic Charging Conditions. J Phys Chem Lett 2011; 2:120-124. [PMID: 26295530 DOI: 10.1021/jz1016922] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We propose herein a new reliable approach to assess solvation numbers of ions confined in carbon nanopores based on dynamic quartz crystal measurements. This was proved for the entire families of alkaline, alkaline-earth cations, and halogen anions. As-assessed hydration numbers appear in the sequence characteristic of a transition from the cosmotropic to a chaotropic-type behavior with the decrease of the ion's charge-to-size ratio. The information on the behavior of ions confined in nanometric space of different (especially charged) carbon materials is in high demand for the development of powerful supercapacitors, nanofiltration membranes, and chemical/biochemical sensors.
Collapse
Affiliation(s)
- Mikhael D Levi
- Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Sergey Sigalov
- Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Gregory Salitra
- Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Ran Elazari
- Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Doron Aurbach
- Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
| |
Collapse
|
187
|
Lewus RA, Darcy PA, Lenhoff AM, Sandler SI. Interactions and phase behavior of a monoclonal antibody. Biotechnol Prog 2011; 27:280-9. [DOI: 10.1002/btpr.536] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Revised: 07/30/2010] [Indexed: 11/11/2022]
|
188
|
Ferreira CC, Bergmann CP. Transport of Ca+2 and $${{\rm SO}_{4}^{-2}}$$ ions in Porous Media of Clay Product and its Association with the Efflorescence Phenomenon. Transp Porous Media 2011. [DOI: 10.1007/s11242-010-9610-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
|
189
|
Transport of Ca+2 and $${{\rm SO}_{4}^{-2}}$$ Ions in Porous Media of Clay Product and Its Association with the Efflorescence Phenomenon. Transp Porous Media 2010. [DOI: 10.1007/s11242-010-9598-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
|
190
|
Fujita K, Ohno H. Enzymatic activity and thermal stability of metallo proteins in hydrated ionic liquids. Biopolymers 2010; 93:1093-9. [PMID: 20665687 DOI: 10.1002/bip.21526] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Hydrated choline dihydrogen phosphate (Hy[ch][dhp]) containing 30 wt% water was investigated as a novel protein solvent. The Hy[ch][dhp] dissolved some metallo proteins (cytochrome c, peroxidase, ascorbate oxidase, azurin, pseudoazurin and fructose dehydrogenase) without any modification. These proteins retained the surroundings of the active site after dissolution in Hy[ch][dhp]. Some metallo proteins were found to retain their activity in the Hy[ch][dhp].
Collapse
Affiliation(s)
- Kyoko Fujita
- Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo184-8588, Japan
| | | |
Collapse
|
191
|
Beauchamp DL, Khajehpour M. Probing the effect of water-water interactions on enzyme activity with salt gradients: a case-study using ribonuclease t1. J Phys Chem B 2010; 114:16918-28. [PMID: 21114308 DOI: 10.1021/jp107556s] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Water molecules interact with one another via hydrogen bonds. Experimental and theoretical evidence indicates that these hydrogen bonds occur in two modalities--high- and low-angle hydrogen bonding--and that the addition of various solutes to water affects only the number of water molecules participating in a specific type of hydrogen bond interactions, not the nature of the water-water interactions. In this work, we have investigated the effect of each of these hydrogen bonding types upon the activity of the enzyme ribonuclease t1. This was done through perturbation of the water hydrogen bonding distribution by using various salts. Our results indicate that various salts differ in their ability to reduce the enzymatic activity of ribonuclease t1, and this ability is well correlated with the ability of each salt to promote high-angle hydrogen bonding in water. By applying the two-phase model of liquid water (i.e., liquid water being modeled as an equilibrium existing between two phases, LD and HD water), we demonstrate that our results are compatible with the assumption that increasing the population of high-angle hydrogen bonds among water molecules stabilizes the more compact, less active conformations of the enzyme. This indicates that the structures that proteins adopt in water solution depend upon the nature of interactions between water molecules.
Collapse
Affiliation(s)
- David L Beauchamp
- Department of Chemistry, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | | |
Collapse
|
192
|
Well-constructed cellulose acetate membranes for forward osmosis: Minimized internal concentration polarization with an ultra-thin selective layer. J Memb Sci 2010. [DOI: 10.1016/j.memsci.2010.05.056] [Citation(s) in RCA: 302] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
193
|
Zavitsas A. The Nature of Aqueous Solutions: Insights into Multiple Facets of Chemistry and Biochemistry from Freezing-Point Depressions. Chemistry 2010; 16:5942-60. [DOI: 10.1002/chem.200903063] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
194
|
Zavitsas AA. Ideal Behavior of Water Solutions of Strong Electrolytes and Non-electrolytes at High Concentrations. J SOLUTION CHEM 2010. [DOI: 10.1007/s10953-010-9503-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
195
|
Zahn R, Boulmedais F, Vörös J, Schaaf P, Zambelli T. Ion and Solvent Exchange Processes in PGA/PAH Polyelectrolyte Multilayers Containing Ferrocyanide. J Phys Chem B 2010; 114:3759-68. [DOI: 10.1021/jp9106074] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Raphael Zahn
- Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, University and ETH Zürich, Switzerland, and Centre National de la Recherche Scientifique, Institut Charles Sadron, 23 rue du Loess, BP 84047,67034 Strasbourg Cedex 2, France
| | - Fouzia Boulmedais
- Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, University and ETH Zürich, Switzerland, and Centre National de la Recherche Scientifique, Institut Charles Sadron, 23 rue du Loess, BP 84047,67034 Strasbourg Cedex 2, France
| | - János Vörös
- Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, University and ETH Zürich, Switzerland, and Centre National de la Recherche Scientifique, Institut Charles Sadron, 23 rue du Loess, BP 84047,67034 Strasbourg Cedex 2, France
| | - Pierre Schaaf
- Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, University and ETH Zürich, Switzerland, and Centre National de la Recherche Scientifique, Institut Charles Sadron, 23 rue du Loess, BP 84047,67034 Strasbourg Cedex 2, France
| | - Tomaso Zambelli
- Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, University and ETH Zürich, Switzerland, and Centre National de la Recherche Scientifique, Institut Charles Sadron, 23 rue du Loess, BP 84047,67034 Strasbourg Cedex 2, France
| |
Collapse
|
196
|
Shechter I, Ramon O, Portnaya I, Paz Y, Livney YD. Microcalorimetric Study of the Effects of a Chaotropic Salt, KSCN, on the Lower Critical Solution Temperature (LCST) of Aqueous Poly(N-isopropylacrylamide) (PNIPA) Solutions. Macromolecules 2009. [DOI: 10.1021/ma9018312] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
| | - Ory Ramon
- Laboratory of Biopolymers and Food-Nanotechnology, Department of Biotechnology & Food Engineering
| | - Irina Portnaya
- Laboratory of Biopolymers and Food-Nanotechnology, Department of Biotechnology & Food Engineering
| | | | - Yoav D. Livney
- Laboratory of Biopolymers and Food-Nanotechnology, Department of Biotechnology & Food Engineering
| |
Collapse
|
197
|
Tung KL, Jean YC, Nanda D, Lee KR, Hung WS, Lo CH, Lai JY. Characterization of multilayer nanofiltration membranes using positron annihilation spectroscopy. J Memb Sci 2009. [DOI: 10.1016/j.memsci.2009.07.020] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
198
|
|
199
|
Kobayashi M, Terayama Y, Hino M, Ishihara K, Takahara A. Characterization of swollen structure of high-density polyelectrolyte brushes in salt solution by neutron reflectivity. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/184/1/012010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
200
|
Guo F, Friedman JM. Charge density-dependent modifications of hydration shell waters by Hofmeister ions. J Am Chem Soc 2009; 131:11010-8. [PMID: 19603752 PMCID: PMC2745343 DOI: 10.1021/ja902240j] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Gadolinium (Gd(3+)) vibronic sideband luminescence spectroscopy (GVSBLS) is used to probe, as a function of added Hofmeister series salts, changes in the OH stretching frequency derived from first-shell waters of aqueous Gd(3+) and of Gd(3+) coordinated to three different types of molecules: (i) a chelate (EDTA), (ii) structured peptides (mSE3/SE2) of the lanthanide-binding tags (LBTs) family with a single high-affinity binding site, and (iii) a calcium-binding protein (calmodulin) with four binding sites. The vibronic sideband (VSB) corresponding to the OH stretching mode of waters coordinated to Gd(3+), whose frequency is inversely correlated with the strength of the hydrogen bonding to neighboring waters, exhibits an increase in frequency when Gd(3+) becomes coordinated to either EDTA, calmodulin, or mSE3 peptide. In all of these cases, the addition of cation chloride or acetate salts to the solution increases the frequency of the vibronic band originating from the OH stretching mode of the coordinated waters in a cation- and concentration-dependent fashion. The cation dependence of the frequency increase scales with charge density of the cations, giving rise to an ordering consistent with the Hofmeister ordering. On the other hand, water Raman spectroscopy shows no significant change upon addition of these salts. Additionally, it is shown that the cation effect is modulated by the specific anion used. The results indicate a mechanism of action for Hofmeister series ions in which hydrogen bonding among hydration shell waters is modulated by several factors. High charge density cations sequester waters in a configuration that precludes strong hydrogen bonding to neighboring waters. Under such conditions, anion effects emerge as anions compete for hydrogen-bonding sites with the remaining free waters on the surface of the hydration shell. The magnitude of the anion effect is both cation and Gd(3+)-binding site specific.
Collapse
Affiliation(s)
- Feng Guo
- Department of Biophysics and Physiology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, New York, U.S.A. 10461
| | - Joel M. Friedman
- Department of Biophysics and Physiology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, New York, U.S.A. 10461
| |
Collapse
|