scholarly journals Electrostatic Solvation Energy for Two Oppositely Charged Ions in a Solvated Protein System: Salt Bridges Can Stabilize Proteins

2010 ◽  
Vol 98 (3) ◽  
pp. 470-477 ◽  
Author(s):  
Haipeng Gong ◽  
Karl F. Freed
Keyword(s):  
Solvation Energy ◽  
Salt Bridges ◽  
Protein System ◽  
Charged Ions ◽  
Oppositely Charged

The negative ions of atomic and molecular oxygen

1943 ◽  
Vol 239 (806) ◽  
pp. 269-304 ◽  
Keyword(s):  
Excited State ◽  
Molecular Oxygen ◽  
Cross Section ◽  
Negative Ions ◽  
Excited Configuration ◽  
Virtual Level ◽  
Resonance Effects ◽  
Low Pressures ◽  
Charged Ions ◽  
Oppositely Charged

The properties, modes of formation and of destruction of the negative ions of atomic and molecular oxygen are examined in detail, using quantal theory to interpret and amplify the somewhat meagre experimental information. A detailed examination of the (Lf)2 (2j)2 (2/>)4 (3s) excited configuration of O - is made in an attempt to decide whether it can give rise to the observed stable excited state in which the attached electron has nearly zero binding energy. This is important in attachment, detachment and electron scattering phenomena as resonance effects will occur if the configuration is on the verge of stability or instability. The Hartree-Fock equations have been solved for the deepest (4P and 2P) terms of this configuration, polarization effects being allowed for by the introduction of a term involving a polarizability p regarded as an adjustable parameter. Stable excited P terms are only found when p is two to four times as large as the polarizability of O deduced from the refractivity of 0 2. This does not completely exclude identification of the excited state as belonging to the configuration considered. To examine the possible resonance effects, radiative attachment and detachment rates are calculated for a variety of values of the polarizability parameter p. The rapid variation of these quantities with p in the region where a real or virtual level of the 3^ electron, with small energy, exists makes it unlikely that definite theoretical values can be given until more information as to the proper value of p is forthcoming. Meanwhile, the parameter p provides a convenient correlation of the probabilities of the two processes with the energy of the 3* electron. The other possible attachment and detachment processes involving O and 0 ~ are also discussed. In order to interpret experiments on attachments of electron swarms in 0 2 and to decide how to extrapolate the results to low pressures, the deep electronic states of O^" are considered in detail, employing the empirical methods commonly used in studying molecular structure. It is found that their distribution is such as to make it most unlikely that Ofl~ ions can be formed with appreciable probability by attachment of slow electrons to Oz at low pressures, by a pressure-independent process other than direct radiative attachment. However, considerable difficulties and uncertainties are found in attempting a detailed interpretation of the experimental results at the higher pressures and more experiments are required. In the final section the formation of pairs of oppositely charged ions from molecules by impact of electrons or light quanta is investigated in terms of the theory of the crossing of molecular potentialenergy curves. The same theory is also applied to obtain information as to the possible magnitude of the cross-section for mutual neutralization of oppositely charged ions by electron transfer on impact. It is shown that a cross-section of between 10~13 and 10-12 cm.2 is quite likely to occur for atomic oxygen ions, but the occurrence of one as high as 1CH1 cm.2 is most unlikely. A detailed summary of results and conclusions is given.

scholarly journals Dipole-driven self-organization of zwitterionic molecules on alkali halide surfaces

2012 ◽  
Vol 3 ◽  
pp. 285-293 ◽  
Author(s):  
Laurent Nony ◽  
Franck Bocquet ◽  
Franck Para ◽  
Frédéric Chérioux ◽  
Eric Duverger ◽  
...  
Keyword(s):  
Substrate Surface ◽  
Crystal Surfaces ◽  
High Coverage ◽  
Force Microscopy ◽  
Atomic Force ◽  
Defect Sites ◽  
Low Coverage ◽  
Charged Ions ◽  
Oppositely Charged ◽  
Step Edges

We investigated the adsorption of 4-methoxy-4′-(3-sulfonatopropyl)stilbazolium (MSPS) on different ionic (001) crystal surfaces by means of noncontact atomic force microscopy. MSPS is a zwitterionic molecule with a strong electric dipole moment. When deposited onto the substrates at room temperature, MSPS diffuses to step edges and defect sites and forms disordered assemblies of molecules. Subsequent annealing induces two different processes: First, at high coverage, the molecules assemble into a well-organized quadratic lattice, which is perfectly aligned with the <110> directions of the substrate surface (i.e., rows of equal charges) and which produces a Moiré pattern due to coincidences with the substrate lattice constant. Second, at low coverage, we observe step edges decorated with MSPS molecules that run along the <110> direction. These polar steps most probably minimize the surface energy as they counterbalance the molecular dipole by presenting oppositely charged ions on the rearranged step edge.

Near-field plume properties of an ion beam formed by alternating extraction and acceleration of oppositely charged ions

2016 ◽  
Vol 25 (5) ◽  
pp. 055013 ◽  
Author(s):  
N Oudini ◽  
A Aanesland ◽  
P Chabert ◽  
S Lounes-Mahloul ◽  
A Bendib
Keyword(s):  
Ion Beam ◽  
Near Field ◽  
Charged Ions ◽  
Oppositely Charged

Ion trajectories in weak electrolytes

1980 ◽  
Vol 371 (1746) ◽  
pp. 413-427 ◽  
Keyword(s):  
Steady State ◽  
Electric Field ◽  
Applied Electric Field ◽  
Numerical Quadrature ◽  
Average Flow ◽  
Recombination Processes ◽  
Weak Electrolytes ◽  
The Mean ◽  
Charged Ions ◽  
Oppositely Charged

The equations of the mean relative trajectories of neighbouring oppositely charged ions in a weak electrolyte that has attained a steady state in a uniform applied electric field are determined analytically. Both the dissociation and recombination of ions are considered and the mean relative trajectories are defined in terms of the ensemble average flow patterns of the ions participating in these processes. For recombination of ions, the equation of the boundary of ionic attraction is also derived. The mean times involved in the dissociation and recombination processes are determined by using numerical quadrature. The results obtained are consistent with the Bjerrum (1926) theory of weak electrolytes.

scholarly journals ON THE CAUSE OF THE INFLUENCE OF IONS ON THE RATE OF DIFFUSION OF WATER THROUGH COLLODION MEMBRANES. II

1920 ◽  
Vol 2 (5) ◽  
pp. 563-576 ◽  
Author(s):  
Jacques Loeb
Keyword(s):  
Opposite Sign ◽  
Pure Water ◽  
Critical Value ◽  
Relative Influence ◽  
Double Layers ◽  
Electrical Double Layers ◽  
Charged Ions ◽  
Oppositely Charged ◽  
Charged Water

1. It had been shown in previous publications that when pure water is separated from a solution of an electrolyte by a collodion membrane the ion with the same sign of charge as the membrane increases and the ion with the opposite sign of charge as the membrane diminishes the rate of diffusion of water into the solution; but that the relative influence of the oppositely charged ions upon the rate of diffusion of water through the membrane is not the same for different concentrations. Beginning with the lowest concentrations of electrolytes the attractive influence of that ion which has the same sign of charge as the collodion membrane upon the oppositely charged water increases more rapidly with increasing concentration of the electrolyte than the repelling effect of the ion possessing the opposite sign of charge as the membrane. When the concentration exceeds a certain critical value the repelling influence of the latter ion upon the water increases more rapidly with a further increase in the concentration of the electrolyte than the attractive influence of the ion having the same sign of charge as the membrane. 2. It is shown in this paper that the influence of the concentration of electrolytes on the rate of transport of water through collodion membranes in electrical endosmose is similar to that in the case of free osmosis. 3. On the basis of the Helmholtz theory of electrical double layers this seems to indicate that the influence of an electrolyte on the rate of diffusion of water through a collodion membrane in the case of free osmosis is due to the fact that the ion possessing the same sign of charge as the membrane increases the density of charge of the latter while the ion with the opposite sign diminishes the density of charge of the membrane. The relative influence of the oppositely charged ions on the density of charge of the membrane is not the same in all concentrations. The influence of the ion with the same sign of charge increases in the lowest concentrations more rapidly with increasing concentration than the influence of the ion with the opposite sign of charge, while for somewhat higher concentrations the reverse is true.

AN EXAMINATION OF MAYER'S THEORY OF IONIC SOLUTIONS: THE CALCULATION OF THE RELATIVE APPARENT MOLAL HEAT CONTENT AND APPARENT MOLAL VOLUME OF SODIUM CHLORIDE IN AQUEOUS SOLUTIONS AT 25 °C.

1954 ◽  
Vol 32 (8) ◽  
pp. 802-811 ◽  
Author(s):  
G. C. Benson
Keyword(s):  
Sodium Chloride ◽  
Heat Content ◽  
Apparent Molal Volume ◽  
Good Representation ◽  
Molal Volume ◽  
Volume Formula ◽  
Heats Of Dilution ◽  
Solution Methods ◽  
Charged Ions ◽  
Oppositely Charged

Mayer's theory gives a good representation of the apparent molal volume [Formula: see text] of sodium chloride in aqueous solution at 25 °C up to a concentration 0.4 molar. Representation of the relative apparent molal heat content [Formula: see text] is also satisfactory but over a smaller range of concentration. The shape of the [Formula: see text] curve is strongly influenced by the temperature dependence of the distance of closest approach of oppositely charged ions in the solution. Methods of evaluating this term are considered. The utility of Mayer's theory for the extrapolation of experimental data to infinite dilution is illustrated in the case of [Formula: see text] and of intermediate heats of dilution.

Discrete water molecules in the vicinity of two oppositely charged ions

1969 ◽  
Vol 47 (8) ◽  
pp. 873-880 ◽  
Author(s):  
Dieter K. Ross
Keyword(s):  
Water Molecules ◽  
Cavity Size ◽  
Minimum Potential Energy ◽  
Spheroidal Cavity ◽  
Minimum Potential ◽  
Outer Water ◽  
Dielectric Continuum ◽  
Charged Ions ◽  
Oppositely Charged ◽  
Made In

An attempt is made to describe the water molecules in contact with an ion pair in an aqueous solution. One possible arrangement consisting of 10 nonpolarizable water dipoles is considered and a comparison of various energy terms is made in order to decide what factors are most important. The two ions and their attached water dipoles are enclosed in a spheroidal cavity embedded in a dielectric continuum to represent the bulk of the water. It is shown that the energy associated with the water molecules lying in the central region between the two ions is practically unaffected by the cavity size. On the other hand, although the behavior of the "outer" water molecules is extremely sensitive to the cavity size it is a good approximation to the more precise statistical problem to place them in the position of minimum potential energy.

scholarly journals ON THE CAUSE OF THE INFLUENCE OF IONS ON THE RATE OF DIFFUSION OF WATER THROUGH COLLODION MEMBRANES. I

1920 ◽  
Vol 2 (4) ◽  
pp. 387-408 ◽  
Author(s):  
Jacques Loeb
Keyword(s):  
Double Layer ◽  
Turning Point ◽  
Unit Area ◽  
Opposite Sign ◽  
Pure Water ◽  
Hydrogen Ions ◽  
Water Side ◽  
Molecular Concentration ◽  
Charged Ions ◽  
Oppositely Charged

1. In three previous publications it had been shown that electrolytes influence the rate of diffusion of pure water through a collodion membrane into a solution in three different ways, which can be understood on the assumption of an electrification of the water or the watery phase at the boundary of the membrane; namely, (a) While the watery phase in contact with collodion is generally positively electrified, it happens that, when the membrane has received a treatment with a protein, the presence of hydrogen ions and of simple cations with a valency of three or above (beyond a certain concentration) causes the watery phase of the double layer at the boundary of membrane and solution to be negatively charged. (b) When pure water is separated from a solution by a collodion membrane, the initial rate of diffusion of water into a solution is accelerated by the ion with the opposite sign of charge and retarded by the ion with the same sign of charge as that of the water, both effects increasing with the valency of the ion and a second constitutional quantity of the ion which is still to be defined. (c) The relative influence of the oppositely charged ions, mentioned in (b), is not the same for all concentrations of electrolytes. For lower concentrations the influence of that ion usually prevails which has the opposite sign of charge from that of the watery phase of the double layer; while in higher concentrations the influence of that ion begins to prevail which has the same sign of charge as that of the watery phase of the double layer. For a number of solutions the turning point lies at a molecular concentration of about M/256 or M/512. In concentrations of M/8 or above the influence of the electrical charges of ions mentioned in (b) or (c) seems to become less noticeable or to disappear entirely. 2. It is shown in this paper that in electrical endosmose through a collodion membrane the influence of electrolytes on the rate of transport of liquids is the same as in free osmosis. Since the influence of electrolytes on the rate of transport in electrical endosmose must be ascribed to their influence on the quantity of electrical charge on the unit area of the membrane, we must conclude that the same explanation holds for the influence of electrolytes on the rate of transport of water into a solution through a collodion membrane in the case of free osmosis. 3. We may, therefore, conclude, that when pure water is separated from a solution of an electrolyte by a collodion membrane, the rate of diffusion of water into the solution by free osmosis is accelerated by the ion with the opposite sign of charge as that of the watery phase of the double layer, because this ion increases the quantity of charge on the unit area on the solution side of the membrane; and that the rate of diffusion of water is retarded by the ion with the same sign of charge as that of the watery phase for the reason that this ion diminishes the charge on the solution side of the membrane. When, therefore, the ions of an electrolyte raise the charge on the unit area of the membrane on the solution side above that on the side of pure water, a flow of the oppositely charged liquid must occur through the interstices of the membrane from the side of the water to the side of the solution (positive osmosis). When, however, the ions of an electrolyte lower the charge on the unit area of the solution side of the membrane below that on the pure water side of the membrane, liquid will diffuse from the solution into the pure water (negative osmosis). 4. We must, furthermore, conclude that in lower concentrations of many electrolytes the density of electrification of the double layer increases with an increase in concentration, while in higher concentrations of the same electrolytes it decreases with an increase in concentration. The turning point lies for a number of electrolytes at a molecular concentration of about M/512 or M/256. This explains why in lower concentrations of electrolytes the rate of diffusion of water through a collodion membrane from pure water into solution rises at first rapidly with an increase in concentration while beyond a certain concentration (which in a number of electrolytes is M/512 or M/256) the rate of diffusion of water diminishes with a further increase in concentration.

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