scholarly journals Exchange Counterion in Polycationic Hydrogels: Tunability of Hydrophobicity, Water State, and Floating Capability for a Floating pH Device

Gels ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. 109
Author(s):  
Martin Danko ◽  
Zuzana Kronekova ◽  
Igor Krupa ◽  
Jan Tkac ◽  
Peter Matúš ◽  
...  
Keyword(s):  
Water Repellency ◽  
Water Molecules ◽  
Raman Spectrometry ◽  
Hydrophobic Contact ◽  
Water State ◽  
Fast Exchange ◽  
Tetrabutylammonium Chloride ◽  
Water Swelling ◽  
External Stimuli ◽  
Kinetics Of

Smart gel materials are capable of controlling and switching swelling, water state, and wettability properties triggered by external stimuli. In this study, we fabricated a series of polyelectrolyte hydrogels bearing a 3-trimethylammoniumpropyl pendant to a methacrylamide-based backbone and examined the switchability with hydrophobic-like counteranions. The exchange between the initial chloride and camphor sulfate (CaS), dodecyl sulfate (DS), and perfluorooctanoate (PFO) counterions was investigated. The kinetics of the exchange showed that the fast exchange (within 4 h) of PFO allowed for a favorable coordination for ion pairing, resulting in a decrease in hydration. The reversibility of the exchange to the Cl- ion was only enabled for the CaS ion due to its bulkiness, while the PFO and DS hydrogels were unable to exchange, even by using tetrabutylammonium chloride, which is a structurally similar reagent, due to aggregation or the coagulates in the collapsed state of the linear tails of the counterions. The hydrogels exhibited a modulable water state and water swelling. Moreover, the hydrogels containing DS and PFO, as counterions, showed surface hydrophobic (contact angle 90°) and high hydrophobic (110°) behavior, respectively. The Raman spectrometry fluorescence with a pyrene probe indicated an increase in strong hydrogen-bonded water molecules, water confinement, and hydrophobic domains in the PFO hydrogel. Moreover, the PFO-modified hydrogel demonstrated a free-floating ability on the water surface, with a strong water repellency, showing that it has the potential to be applied in a floating pH detection device to distinguish between volatile and nonvolatile bases in a controlled manner.

scholarly journals SOLVATION OF THE [Cr(NCS)4(IMIDAZOLE)2] ION IN ETHANOL-WATER MIXTURES

2002 ◽  
Vol 10 (11) ◽  
pp. 63-72
Author(s):  
lon Ganescu ◽  
George Bratulescu ◽  
Ion Papa ◽  
Anca Ganescu ◽  
Alin Barbu ◽  
...  
Keyword(s):  
Kinetic Parameters ◽  
Order Reaction ◽  
Water Molecules ◽  
Hydrogen Ions ◽  
Second Order Reaction ◽  
Acidic Solutions ◽  
The Third ◽  
Competitive Reactions ◽  
Different Temperatures ◽  
Kinetics Of

Salvation kinetics of [Cr(NCS)4(imidazole)2]- has been studied in ethanol-water mixtures at different temperatures. The first stage of the solvation consists of two competitive reactions: two NCS- ions are exchanged, presumably, by water molecules and simultaneously an imidazole molecule by ethanol, the latter in a second-order reaction, accelerated by hydrogen ions. The exchange of the amine is followed by the substitution of the first two NCS- ions. The third and fourth NCS- ions are substituted only in neutral and slightly acidic solutions. Kinetic parameters have been determined for reactions (1), (2), and (4). The influence of the solvent composition and acidity is discussed

Effects of water molecules on binding kinetics of peptide receptor on a piezoelectric microcantilever

2012 ◽  
Vol 101 (23) ◽  
pp. 233704 ◽  
Author(s):  
Sang Hui Kim ◽  
Yong Kyoung Yoo ◽  
Myung-Sic Chae ◽  
Ji Yoon Kang ◽  
Tae Song Kim ◽  
...  
Keyword(s):  
Binding Kinetics ◽  
Water Molecules ◽  
Peptide Receptor ◽  
Piezoelectric Microcantilever ◽  
Kinetics Of

scholarly journals Kinetics of Hydrogen Generation from Oxidation of Hydrogenated Silicon Nanocrystals in Aqueous Solutions

Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1413 ◽  
Author(s):  
Gauhar Mussabek ◽  
Sergei A. Alekseev ◽  
Anton I. Manilov ◽  
Sergii Tutashkonko ◽  
Tetyana Nychyporuk ◽  
...  
Keyword(s):  
Silicon Nanocrystals ◽  
Silicon Nanoparticles ◽  
Hydrogen Generation ◽  
Hydrogen Release ◽  
Water Molecules ◽  
Hydrogen Energy ◽  
Hydrogenated Silicon ◽  
Energy Applications ◽  
Kinetics Of ◽  
Silicon Nanopowders

Hydrogen generation rate is one of the most important parameters which must be considered for the development of engineering solutions in the field of hydrogen energy applications. In this paper, the kinetics of hydrogen generation from oxidation of hydrogenated porous silicon nanopowders in water are analyzed in detail. The splitting of the Si-H bonds of the nanopowders and water molecules during the oxidation reaction results in powerful hydrogen generation. The described technology is shown to be perfectly tunable and allows us to manage the kinetics by: (i) varying size distribution and porosity of silicon nanoparticles; (ii) chemical composition of oxidizing solutions; (iii) ambient temperature. In particular, hydrogen release below 0 °C is one of the significant advantages of such a technological way of performing hydrogen generation.

(Invited) Understanding the Complex Roles of Water Molecules in the HER/HOR Kinetics of Pt in Aqueous Solutions

2020 ◽  
Vol MA2020-01 (37) ◽  
pp. 1533-1533
Author(s):  
Qingying Jia ◽  
Ershuai Liu ◽  
Sanjeev Mukerjee
Keyword(s):  
Aqueous Solutions ◽  
Water Molecules ◽  
Kinetics Of

A Raman Spectral Study of the Kinetics of Hydrolysis of Acetonitrile Catalyzed by Hg(II)

1975 ◽  
Vol 53 (3) ◽  
pp. 427-436 ◽  
Author(s):  
Yu-Keung Sze ◽  
Donald E. Irish
Keyword(s):  
Time Span ◽  
Water Molecules ◽  
Specific Rate ◽  
Ammine Complexes ◽  
Kinetics Of Hydrolysis ◽  
Specific Rate Constant ◽  
Rate Of Hydrolysis ◽  
Raman Spectral ◽  
Kinetics Of ◽  
Hydrolysis Of

Raman spectroscopy has been employed to follow the relatively slow rate of hydrolysis of acetonitrile, catalyzed by mercury(II). Raman lines at 2275 and 2305 cm−1 are characteristic of CH3CN bound to Hg2+, and are distinct from lines of bulk solvent. The intensities of these new lines decrease with time. From the intensities, concentrations of bound acetonitrile, [CH3CN]B were calculated for a time span of 400 min. The data fit a second order rate law: Rate = k[CH3CN]B[H2O]. The specific rate constant, k, obtained from four sets of data for the system Hg(ClO4)2–CH3CN–H2O equals 1.05 ± 0.06 × 10−4 mol−1 1 min−1 at 25 °C. The energy of activation is 18.9 kcal mol−1. In the proposed mechanism water molecules attack acetonitrile molecules which are bound to Hg2+ and form a mercury(II)–acetamide complex. Raman lines characteristic of this species are observed. This species slowly converts to mercury(II) ammine complexes and acetic acid. Anions which coordinate with Hg2+ more strongly than CH3CN, such as nitrate or acetate, slow or prevent the hydrolysis reaction.

scholarly journals Properties of cupric ions in benzylamine oxidase from pig plasma as studied by magnetic-resonance and kinetic methods

1979 ◽  
Vol 177 (1) ◽  
pp. 289-302 ◽  
Author(s):  
R Barker ◽  
N Boden ◽  
G Cayley ◽  
S C Charlton ◽  
R Henson ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Water Molecule ◽  
Isoelectric Focusing ◽  
Gel Electrophoresis ◽  
Analytical Ultracentrifugation ◽  
The Other ◽  
Water Molecules ◽  
Fast Exchange ◽  
Benzylamine Oxidase ◽  
O2 Binding

Benzylamine oxidase from pig plasma has been studied by a variety of chemical and physical techniques. 1. Analytical ultracentrifugation, gel electrophoresis and isoelectric-focusing studies suggest that the enzyme is composed of two subunits with closely similar primary structures. 2. E.s.r. and n.m.r. measurements show that the enzyme contains two well-separated (greater than 0.6 nm) Cu2+ ions at chemically distinct sites. Each Cu2+ ion is coordinated by two water molecules, one ‘axial’ and the other ‘equatorial’. Both water molecules undergo fast exchange (10(5)–10(8) s-1) with solvent and are deprotonated in the pH r!ange 8–9, but only the equatorial water molecule is displaced by the inhibitors N3- and CN-. 3. Kinetic and e.s.r. measurements show that azide and cyanide compete against O2 binding and also make the two Cu2+ sites identical. It is concluded that Cu2+ must participate in the re-oxidation of reduced enzyme by molecular O2.

Diffusion kinetics of water molecules in a nanoporous adsorbent

2008 ◽  
Vol 72 (12) ◽  
pp. 1679-1683 ◽  
Author(s):  
P. O. Kapralov ◽  
V. G. Artemov ◽  
G. A. Gusev ◽  
V. I. Tikhonov ◽  
A. A. Volkov
Keyword(s):  
Water Molecules ◽  
Diffusion Kinetics ◽  
Kinetics Of

Al(iii)-NTA-fluoride: a simple model system for Al–F binding with interesting thermodynamics

2020 ◽  
Vol 49 (39) ◽  
pp. 13726-13736
Author(s):  
Eliška Hacaperková ◽  
Adam Jaroš ◽  
Jan Kotek ◽  
Johannes Notni ◽  
Michal Straka ◽  
...  
Keyword(s):  
Simple Model ◽  
Coordination Sphere ◽  
Model System ◽  
Water Molecules ◽  
Phosphate Anion ◽  
High Ph ◽  
Fast Exchange ◽  
Simple Model System ◽  
Ph Dependent ◽  
High Phosphate

Unsaturated AlIII complex shows a fast exchange of water molecules, hydroxide and fluoride anions in the coordination sphere, highly pH-dependent fluoride binding and release of fluorides at high pH or at high phosphate anion concentrations.

scholarly journals Kinetics of protein–ligand unbinding: Predicting pathways, rates, and rate-limiting steps

2015 ◽  
Vol 112 (5) ◽  
pp. E386-E391 ◽  
Author(s):  
Pratyush Tiwary ◽  
Vittorio Limongelli ◽  
Matteo Salvalaglio ◽  
Michele Parrinello
Keyword(s):  
Drug Design ◽  
Practical Importance ◽  
Binding Pocket ◽  
Water Molecules ◽  
The Mean ◽  
General Protein ◽  
Experimental Values ◽  
Rate Limiting ◽  
Kinetics Of

The ability to predict the mechanisms and the associated rate constants of protein–ligand unbinding is of great practical importance in drug design. In this work we demonstrate how a recently introduced metadynamics-based approach allows exploration of the unbinding pathways, estimation of the rates, and determination of the rate-limiting steps in the paradigmatic case of the trypsin–benzamidine system. Protein, ligand, and solvent are described with full atomic resolution. Using metadynamics, multiple unbinding trajectories that start with the ligand in the crystallographic binding pose and end with the ligand in the fully solvated state are generated. The unbinding rate koff is computed from the mean residence time of the ligand. Using our previously computed binding affinity we also obtain the binding rate kon. Both rates are in agreement with reported experimental values. We uncover the complex pathways of unbinding trajectories and describe the critical rate-limiting steps with unprecedented detail. Our findings illuminate the role played by the coupling between subtle protein backbone fluctuations and the solvation by water molecules that enter the binding pocket and assist in the breaking of the shielded hydrogen bonds. We expect our approach to be useful in calculating rates for general protein–ligand systems and a valid support for drug design.

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