Rotational Motion Of Water Molecules Research Articles

Orientational relaxation in hydrogen-bonded systems: aqueous solutions of electrolytes

A model of the rotational motion of water molecules within ion hydration sheaths is proposed in the present paper. This model is based on the concept of a ‘boundary’ ion, according to which the parameters of the structural surroundings, as well as the translational, rotational and librational motions of water molecules within the first sphere, are the same as those for water molecules in water. The wide-band absorption spectra, α(ν)(0 < ν/cm–1 < 400), and the complex dielectric permittivity spectrum measured for the concentrated electrolyte solutions, are described on the basis of the model proposed in this paper. It is shown that the confined rotator/extended diffusion (CR/ED) model, which has been advanced previously for liquid water, is applicable for spectral calculations of the electrolyte solutions studied in the present paper.The typical characteristics of ions having hydrophilic and hydrophobic hydration, as well as the distinctions between the hydration sheaths of ions with negative and positive hydrations, are discussed. A new method is proposed to study the molecular nature of these phenomena at the level of elementary processes. The complex dielectric permittivity of the concentrated LiCl, NaCl, Nal, KCl and KBr solutions has been measured in the range 7–25 GHz at 25 °C. For electrolyte solutions, the wide band (0 ⩽v/cm–1⩽ 1000) dielectric spectra and the parameters of the proposed model are calculated.

Nuclear magnetic resonance study of ion hydration. 3. Anisotropic rotational motion of water molecules bound to the aluminum(III) ion

The H spin-lattice relaxation times, T1, of the separate free and coordinated water signals of aqueous Al(ClO4)3 solutions have been independently measured at temperatures between +10 and -65C and with varying salt concentrations. All inversion-recovery measurements of T1 showed a single exponential form in the above temperature range. Under low temperature conditions, only the intramolecular proton-proton interaction undergoing rotational motion contributes to T1. The experimental results showed that the difference between the two signals' T1 values of the free and coordinated waters arises as the temperature falls below ca -20C. It is assumed that the coordinated water molecules anisotropically rotate as ellipsoidal molecules at low temperatures, whereas the bulk water molecules isotropically rotate as spherical molecules throughout the temperature range. The theory of spin-lattice relaxation due to the anisotropic rotational diffusion by Woessner is applied to the analysis of the motion of the coordinated water molecules and the following conclusions are reached: (1) at low temperatures and low aluminum concentrations, the coordinated water molecules undergo anisotropic rotational motion as an axially symmetric ellipsoidal body whose axis of symmetry is the C2 axis of the H2O molecule; (2) the motion of the hydration water molecule is slowed for low Al concentrations.more » 27 references, 4 figures.« less

Ion concentrations surrounding the myofilaments.

My point of view is a radical departure from everybody elses. Cellular water has been looked at rather extensively. The more we look at it, the more we are confused. The kind of explanation I give here might have been overlooked in the past, but I think it provides clear and consistent physical interpretations. Let’s assume we have a dipole on the protein molecule in ionic water. The positive and negative charges are separated over a distance of about 100 A. This is shown in Figure 1. The energy required to deposit these charges would come from ATP. As you can see right away the small region between charges experiences a very high electric field strength. If we have a significant potential gradient, then the electric field energy rapidly increases (Field Energy = 1/2 eE2). Note that it is proportional to the dielectric constant. Now, the dielectric constant of liquid water is about 80. When water freezes and becomes solid, the dielectric constant increases to about 90. This might sound odd because intuitively the dielectric constant of ice should be less than 80 due to more restricted rotational motion of water molecules. But actually, the opposite is true.

Incoherent quasielastic neutron scattering from water in supercooled regime

Measurements of the quasielastic spectra have been made with a three-axis neutron spectrometer at constant-Q mode in a temperature range from 38/sup 0/C down to -20 /sup 0/C. Two energy resolutions both high (..delta..E = 100 ..mu.. eV) and low (..delta..E = 800 ..mu.. eV) were used to identify and separate a sharp component from a broad one. As temperature is decreased below zero the spectrum shows an increasing sharp component standing out on top of the broad one. The broad component is attributed to rotational motions of water molecules. A preliminary analysis of the linewidths gives a Q-independent relaxation time which has the same magnitude as the rotational relaxation time measured by nuclear magnetic resonance. The Q dependence of the sharp line is analyzed by a Q-dependent diffusion coefficient. A temperature-independent characteristic length l/sub 0/ = 0.5 A is obtained. We then attempt to relate this length to local geometry of protons associated with hydrogen bonding.

A Study of the Rotational Motion of Water Molecules absorbed on the Clay

A Study of the Rotational Motion of Water Molecules absorbed on the Clay

The dynamics of water in heterogeneous systems.

The basic principles of nuclear spin relaxation, dielectric relaxation and quasielastic neutron scattering and their use in studying the motions of water molecules are outlined. A summary is given of the time scales associated with the translational and rotational motions of water molecules and of intermolecular proton exchange in pure liquid water. A model is then proposed for the dynamics of water molecules in heterogeneous systems involving regions having differing compositions, water molecules within each region existing in environments both affected by interaction with the macromolecular components and free of their influence and including exchange of water molecules between different environments and regions. The lifetime of the interaction of water molecules with the macromolecular components is assumed long compared with the time for rotation of such bound molecules. Exchange of protons between water molecules and between water molecules and macromolecules is also considered. The ways in which such processes would be expected to affect the observed nuclear magnetic resonance, dielectric and neutron scattering behaviour are outlined. Particular emphasis is placed on nuclear spin relaxation phenomena and the existence and observation of residual dipolar and quadrupolar splittings in the n.m.r. spectra of1H and2H (D) nuclei in water molecules in such systems, these splittings arising from water molecules dynamically oriented at water/macromolecule interfaces. Details are then given of particular studies of water molecule dynamics in heterogeneous systems using n.m.r., dielectric and neutron scattering techniques. The systems discussed include moist protein powders, protein solutions, phospholipid/ water and soap/water mesophases, clay/water systems and biological polymers and tissues. It is concluded that water in these systems is highly mobile, that water molecules affected directly by a macromolecule tumble anisotropically about all axes relative to the macromolecule with correlation times in the region of 10-9s at 260 K and that these molecules exchange with water molecules free of the influence of the macromolecule with a lifetime in the dynamically oriented state of the order of 10-6s at temperatures around 300 K. The ability of nuclear magnetic relaxation studies to distinguish water in different regions of a tissue is discussed and examples are given of the study of the rate of water transport across membranes using these techniques.

Water at interfaces: Molecular structure and dynamics

Recent advances in molecular mechanics and dynamics of water on inorganic surfaces are reviewed. The structures of hydroxylated surfaces and water-hydroxyl adducts, determined by LEED-Auger studies and infrared spectroscopy, are described to a detail only recently resolved. New mechanistic concepts of nucleation and freezing have ensued from the analysis of time-correlation functions, showing that low-frequency angular perturbations dominate the different behavior of water in bulk phases and at surfaces. While the rotational motion of water molecules in the liquid phase can be interpreted as rotation modulated by making and breaking hydrogen bonds with the neighbors, water adsorbed on nucleating catalysis undergoes an irreversible and complete reorientation in a fraction of the rotational period.

NMR Evidence for the Motion of Br−Ions in the One‐Dimensional Conductor K2Pt(CN)4Br0.3 nH20

AbstractThe motion of Br ions in the one‐dimensional conductor K2Pt(CN)4Br0.3 2.6 H2O at room temperature is observed in the measurements of the NMR line width of Br81 nuclei. The temperature dependence of the NMR line width of H1 nuclei in K2Pt(CN)4Br0.3 × × 2.6 H20 shows that the rotational motion of water molecules is strongly correlated with the gradual metal‐to‐insulator transition in KCP.

Rotational correlation motion in liquid and adsorbed water

The rotational correlation functions of liquid water, of water adsorbed on a silica surface, and of water contained in a zeolite cavity have been determined from the infrared spectra of these systems. In all cases except in critical water and zeolite water, the rotational motion of water molecules is strongly vibrationally perturbed, which results in a periodic acceleration and slowing down (modulation) of the rotary motion. First order perturbation theory shows that the frequency of this modulation is determined by the difference between the average perturbation of the excited and ground vibrational levels. The average modulation frequencies are compared with those of the intermolecular bands of water and of the librations of ice. It is shown that tailing of vibration-rotation bands to low frequencies, observed in infrared and Raman bands of liquid water and to a lesser degree, also in adsorbed water, can be attributed to an attractive perturbation of the rotary motion, which is thought to be a precursor to an oriented hydrogen bond.

Proton Magnetic Resonance in Hydrates of Halogen Compounds of Mg, Ca, Sr and Ba

Proton resonance in crystal water of Mg(H 2 O) 6 Cl 2 , Mg(H 2 O) 6 Br 2 , CaI 2 6H 2 O, SrI 2 6H 2 O and MgI 2 8H 2 O was studied in temperature range from -90°C to +110°C and the same in CaCl 2 6H 2 O, CaBr 2 6H 2 O, SrCl 2 6H 2 O and SrBr 2 6H 2 O was studied in the range above room temperature, all in powdered states. Line shapes were recorded by the radiofrequency spectrometer with an automatic field scanning apparatus connected to the sweeping coils of a permanent magnet. Transitions of second moment and line shapes were observed for all the above salts. Experiments on single crystals of Mg(H 2 O) 6 Cl 2 and CaI 2 6H 2 O were also carried out at room temperature. In Mg(H 2 O) 6 Cl 2 , Mg(H 2 O) 6 Br 2 , CaI 2 6H 2 O, SrI 2 6H 2 O and BaI 2 6H 2 O, water molecules of hydration have the states of hindered rotational motion below melting point, but in CaCl 2 6H 2 O, CaBr 2 6H 2 O, SrCl 2 6H 2 O and SrBr 2 6H 2 O, these rotational states were not observed. The angle between the rotational axis of a water molecule and its inter-proton direction was estimated to be about 90° in the case of Mg(H 2 O) 6 Cl 2 . In the cases of CaI 2 6H 2 O and SrI 2 6H 2 O these angles are calculated to be 45° or 60°, and these results suggest the precession of the rotational axis, if rotational motion of water molecules is assumed to occur about an axis perpendicular to the inter-proton axis. Sharp peaks appearing in chlorides and bromides of Ca and Sr are interpreted as the narrowing due to random re-orientation of the rotational axis.