Water Structure Breaker Research Articles

Volumetric and viscometric studies of urea in binary aqueous solutions of glucose at different temperatures

Densities and viscosities of urea in (1.0, 2.5, and 5.0) mass% of aqueous glucose solutions have been measured at T = (298.15, 303.15, 308.15, and 313.15) K, respectively. Apparent molar volumes, limiting partial molar volume, and relative viscosity have been obtained from the density and viscosity data. Limiting partial molar expansibilities have also been calculated from the temperature dependence of limiting partial molar volumes. The viscosity data has been analyzed using the Jones–Dole equation. The results are used to establish the nature of solute–solute and solute–solvent interactions. The activation parameters of viscous flow have also been calculated on the basis of transition state treatment of the relative viscosity. Result shows that the solute acts as water structure breaker and posses’ weak solute–solvent interaction.

Molar volume, viscosity and conductance studies of ascorbic acid in water, 0.01 M aqueous sodium chloride and dextrose + 0.01 M aqueous sodium chloride

Molar volume, viscosity and conductance of ascorbic acid in water, 0.01 m aqueous sodium chloride and 2, 4 and 6 wt. % of dextrose in 0.01 m aqueous sodium chloride solutions have been evaluated from density, viscosity and conductance data respectively at temperatures 303.15, 308.15, 313.15 and 318.15 K. The solute-solvent interactions for ascorbic acid in water, 0.01 m aqueous sodium chloride and 2, 4 and 6 wt. % of dextrose in 0.01 m aqueous sodium chloride have been inferred from φ o v , B-coefficient of Jones-Dole equation and ∧ o m values. The structure making/ breaking behaviour of ascorbic acid is inferred from the sign of [∂ 2 φ o v /∂T 2 ] p ,dB/dT, transition state theory i.e. free energy contribution per mole of solute (Δμ 2 ) and free energy contribution per mole of solvent (Δμ 1 ) values and temperature coefficient of Walden product i.e. d(Λ o m η 0 )/dT. It has been found from viscosity and conductance studies that ascorbic acid behaves as structure-breaker in water, 0.01 m aqueous sodium chloride and 2, 4 and 6 wt. % of dextrose in 0.01 m aqueous sodium chloride solutions. The energy of activation for ascorbic acid in different systems has also been calculated from conductance and viscosity data.

Organic Additives and Electrolytes as Cloud Point Modifiers in Octylphenol Ethoxylate Solutions

AbstractCloud point measurements of nonionic surfactant Triton X‐100, an octylphenol ethoxylate, were carried out in the absence and presence of various organic additives such as n‐alkanols (methanol, ethanol, propanol and butanol), glycols (ethylene glycol, diethylene glycol and triethylene glycol), glycol ethers (ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and ethylene glycol monobutyl ether (EGMBE)) and electrolytes (LiCl, KCl, NaF, NaCl, NaBr, NaI, MgCl2 and AlCl3). The combined effect of these organic additives and electrolytes on cloud point (CP) measurement was also investigated. The effect of nature of cation, anion and valency of cation on CP is also reported. Among the n‐alkanols and glycol ethers as additives, n‐butanol and EGMBE were found to decrease the CP while all other additives increase the cloud point. The addition of electrolytes (LiCl, NaCl and KCl) to the solution of Triton X‐100 (TX‐100) decreases the CP but the rate of decrease in CP with concentration does not follow the lyotropic series of effect. Sodium halides (except NaI) also decrease the CP and the rate of decrease follows the lyotropic series of effect even in the presence of organic additives. NaI is a water structure breaker, hence it increases the cloud point. Further, cations of increasing valency lessen the depression in CP of TX‐100 with the rate of decrease in CP following the order Na+ > Mg2+ > Al3+ even in the presence of organic additives.

Molar volume, viscosity and conductance studies of nickel sulphate in water and aqueous mannitol

Molar volume, viscosity and conductance of nickel sulphate in water and 2, 4 and 6 wt. % of aqueous mannitol solutions have been evaluated from density, viscosity and conductance data respectively at temperatures 303.15, 308.15, 313.15 and 318.15 K. The solute-solvent interactions for nickel sulphate in water and various compositions of aqueous mannitol have been inferred from Φ 0 v , B-coefficient of Jones-Dole equation and Λ 0 m values. The structure making/breaking behaviour of nickel sulphate is inferred from the sign of [∂ 2 Φ o v /∂T 2 ] p , dBldT and temperature coefficient of Walden product i.e. d(Λ 0 m η 0 )/dT values. It has been found that nickel sulphate behaves as structure-breaker in water and structure-maker in 2, 4 and 6 wt. % of aqueous mannitol solutions from molar volume, viscosity and conductance studies. The energy of activation for nickel sulphate in different composition of aqueous mannitol have also been calculated from conductance and viscosity data.

Study of ion–solvent interactions and activation energy of LiBr in DMSO, H2O and DMSO–H2O mixtures at various temperatures

The Jones–Dole B coefficients of the electrolyte Lithium bromide (LiBr), reference salts tetra butyl ammonium tetra phenyl borate (BU4NBPh4), tetra butyl ammonium bromide (BU4NBr), and potassium chloride (KCl) in dimethylsulfoxide (DMSO), water, and DMSO–water mixtures were obtained at different temperatures range from 25 to 45 °C For this, the relative viscosities were measured for Lithium bromide (LiBr) and reference salts in DMSO, water, and DMSO–water mixtures at above-mentioned temperatures. The B coefficients of these electrolytes were behaved as structure makers in DMSO, while in H2O and DMSO–H2O mixtures, the B-coefficient values were less positive showing the weak structure-making effect. Ionic viscosity B coefficients allow us to assess the behavior of ions in the solvent mixtures. In this study it was observed that all the values of ionic B coefficient of (Li+) were positive and small showing the weak structure-making effects. It was also observed that Br− ions maintain negative B coefficient values in all DMSO–H2O mixtures, except in 60% DMSO mole fraction. From this it can be concluded that Br− ion behaved as a structure breaker in water and in all DMSO–H2O mixtures except in 60% DMSO mole fraction mixtures. The low B ± values of alkali metal ions and Br− ions in water are due to the breakdown of the tetrahedral structural of water and the formation of strongly structured solvated ion. It is also observed that the values of the energy of activation of the flow for LiBr are greater in DMSO–water mixtures and in pure water than in DMSO. This may be due the presence of a network of hydrogen bonds which cause the hindrance in the flow of the solution of LiBr in DMSO–water mixtures and in pure water than in DMSO.

Water structure and its influence on the flotation of carbonate and bicarbonate salts

Interfacial water structure is a most important parameter that influences the collector adsorption by salt minerals such as borax, potash and trona. According to previous studies, salts can be classified as water structure makers and water structure breakers. Water structure making and breaking properties of salt minerals in their saturated brine solutions are essential to explain their flotation behavior. In this work, water structure making–breaking studies in solutions of carbonate and bicarbonate salts (Na 2CO 3, K 2CO 3, NaHCO 3 and NH 4HCO 3) in 4 wt% D 2O in H 2O mixtures have been performed by FTIR analysis of the OD stretching band. This method reveals a microscopic picture of the water structure making/breaking character of the salts in terms of the hydrogen bonding between the water molecules in solution. The results from the vibrational spectroscopic studies demonstrate that carbonate salts (Na 2CO 3 and K 2CO 3) act as strong structure makers, whereas bicarbonate salts (NaHCO 3 and NH 4HCO 3) act as weak structure makers. In addition, the changes in the OD band parameters of carbonate and bicarbonate salt solutions are in agreement with the viscosity characteristics of their solutions.

3P116 フェノールレッドの吸光スペクトルに及ぼす水構造破壊作用を持つ高分子の効果(水・水和/電解質,ポスター発表,第45回日本生物物理学会年会)

3P116 フェノールレッドの吸光スペクトルに及ぼす水構造破壊作用を持つ高分子の効果(水・水和/電解質,ポスター発表,第45回日本生物物理学会年会)

Modulation of polyene antibiotics self-association by ions from the Hofmeister series

The toxicity of the antifungal polyene antibiotic amphotericin B (AMB) has been related to its low solubility, more specifically to a self-associated form termed toxic aggregate. In addition, AMB in aqueous medium gives rise to concentration, ionic strength, and time-dependent polydisperse systems. For this reason different approaches, including the use of several lipid aggregates, have been used in attempts to improve the drug's solubility and increase its therapeutic index. In this context, understanding AMB's self-association properties should help in the preparation of less toxic formulations. Ions from the Hofmeister series alter water properties: while kosmotropes (water structure makers—sulfate, citrate, phosphate) decrease solute solubility, chaotropes (water structure breakers—perchlorate, thiocyanate, trichloroacetate, and the neutral molecule urea) have opposite effects. This work reports a study of the effect of Hofmeister ions and urea on the self-aggregation of AMB and some of its derivatives. Optical absorption and circular dichroism spectra were used to monitor monomeric and aggregated antibiotic . While kosmotropes increased aggregation in a concentration-dependent manner, the opposite was observed for chaotropes. It is shown, for the first time, that thiocyanate and trichloroacetate can induce complete AMB monomerization. The understanding of these processes at the physicochemical and molecular levels and the possibility of modulating the aggregation state of AMB and its derivatives should contribute to elucidate the mechanisms of action and toxicity of this widely used antibiotic and to develop more efficient and less toxic preparations.

VOLUMETRIC AND VISCOMETRIC STUDIES OF NUCLEOSIDES, NUCLEOTIDES AND FURANOSE SUGAR IN AQUEOUS MEDIUM FROM 288.15 TO 298.15K

Density (r/g cm-3) and viscosity (h/10-2gcm-1s-1=1centipoise,CP) of guanosine monophosphate (GMP) and adenosine triphosphate (ATP) referred to as nucleotide, and 2-deoxy adenosine (DOA) and thymidine (TMD) as nucleoside along with their integral furanose sugar, 2-deoxy ribose (DOR) from 0.0004 to 0.0014mol kg-1 solution have been measured at 288.15, 293.15 and 298.15K at atmospheric pressure. The r was fitted into the Masson and h in Jones-Dole equationsfor apparentmolal volume (Vf/cm3mol-1) and viscositycoefficient((hr-1)/m=B/kg mol-1=103gmol-1) data. The Vfand h werealso regressed forV0f and h0 values known as the limiting constants and illustrate solute-solvent and solute-solutein teractions of systems. The apparent molal volume of their various integral units like adenine, guanine and thymine of nucleotides and nucleosidesareestimatedbyV0fTheV0fh0andB values have been used to elucidate the hydrophilic and hydrophobic interactions. The V0f values are negative over the whole range of the compositions which infer greater intermolecular forces and the biomolecules as water structure breakers.

Why 1,4-dioxane is a water-structure breaker

Computations performed for single and paired 1,4-dioxane molecules situated in vacuum and in water showed that the chair conformation is the most stable one. A pair of 1,4-dioxane rings forms a dimer, which is stabilized by two intermolecular hydrogen bonds. Two remaining oxygen atoms are available for interaction with the water molecules. The dimer retains the transfer from vacuum into water, although it results in significant distortion of the rings in terms of the bond distances and, particularly bond angles. The extent of distortion for both rings is different. In consequence, a fairly irregularly shaped bulk dimer exhibited a dipole moment. Such solute species could produce significant disorder of the water structure. Three 1,4-dioxane molecules in the chair conformation, under vacuum and in water, formed a trimer of differently distorted rings. The trimer was also energetically stabilized. Dioxane behaves similarly in nonaqueous, nonpolar and polar solutions. Stabilization energy and dipole moment was independent of the solvent polarity.

Applications of activation energy and transition state theory for nucleos(t)ides and furanose helix puckering interactions in aqueous medium from 288.15 to 298.15 K

Density ρ/103 kg m−3, viscosity η/10−1 kg m−1 s−1 and surface tension γ/N m−1 of nucleosides (2-deoxy adenosine (DOA), thymidine (TMD)), nucleotides (guanosine monophosphate (GMP), adenosine triphosphate (ATP)) and their integral furanose sugar, 2-deoxy ribose (DOR) solutions have been measured at three different temperatures. The ρ values were used for apparent molal volume (V χ /10−6 m3 mol−1), η and γ calculations; η fitted in extended Jones–Dole equation for B/kg mol−1 and D/(kg mol−1)2 coefficients. The γ and V χ were regressed against molality, m for limiting surface tension, γ0 and apparent molal volume, at m → 0. Partial molal volume () of water calculated from ρ values. Free energy of activation of viscous flow (/kJ mol−1) per mol of solvent was calculated from η0 and and of solution from B and , and of dropwise flow of biomolecules from γ0 and values. The and depict a state of activation energy for structure making and breaking of solvent. The B and γ0 values are used to calculate transition state functions, − and ≥ 0 or ≤ 0 for critical state molecular optimization to explain positive transitions of interacting heteromolecules. The , and are found to be negative inferring biomolecules as water structure breakers.

Urea parametrization for molecular dynamics simulations

Although the idea of urea as water structure breaker is widely spread, urea dimer formation is also thought to be an important factor influencing the behavior of urea–water solutions. We use this last idea to obtain a potential for urea to use in molecular dynamic simulations of protein unfolding processes and we compare this with the potentials obtained from density functional theory (DFT). Three potentials for urea are generated. One based on a parametrization for proteins to reproduce substantial dimer formation; and the other two from DFT quantum calculations. Simulations of 2 M and 8 M urea aqueous solutions with the three set of charges were performed. Cyclic dimers with very favorable interactions appear in the simulation with the non-DFT urea potential. Head-to-tail dimer formation occurs too, as found in crystals. This set of charges maintains a good balance between the urea-urea and urea-water interactions, with urea flexibility being important. In the simulations using the quantum derived charge sets dimers are rarely found and with very low interaction energies. Thus, the parametrization obtained from the DFT ab initio calculations is inadequate for molecular dynamics simulations of urea-aqueous solutions. However, the DFT calculations indicate that the urea molecule in water solution may have a planar structure as in the crystal.

Effect of Counterion Species on Colloidal Crystal

The effect of counterion species on the colloidal crystal structure in a dispersion was carefully investigated as a function of the degree of neutralization (alpha) by the ultra-small-angle X-ray scattering technique. The nearest neighbor interparticle distance (2D(exp)) first increased with decreasing alpha, and then decreased after passing through the maximum. This behavior was confirmed for K(+), Li(+), Ca(2+), TMA(+) (tetramethylammonium) as a counterion, and Na(+) in our previous report (Harada, T.; Matsuoka, H.; Ikeda, T.; Yamaoka, H. Langmuir 2000, 16, 1612). However, the alpha value of the maximum position (alpha(max)) largely depended on the counterion species, and it was in the order K(+) < Na(+) < TMA(+) approximately Li(+). This behavior was well characterized by the specific features of each ion: the alpha(max) map could be well superimposed in the Stokes radius-crystal ion radius relationship of counterions. The alpha(max) dependence on Stokes radius was very similar to that of the B coefficient by Jones and Dole except in the case of Ca(2+). In principle, the smaller the value for B, the smaller alpha(max), indicating that a water structure breaker such as K(+) can more easily destroy the colloidal crystal structure. In other words, the effect of the counterion species on colloidal crystal stability follows the Hofmeister series. Including Ca(2+), the relationship was linear for the alpha(max) values plotted as a function of the limiting equivalent conductivity of small ions. A counterion with larger conductivity would be a stronger breaker for the colloidal crystal structure.

Specific ion effects on the growth rates of Staphylococcus aureus and Pseudomonas aeruginosa

Motivated by recent advances in the physical and chemical basis of the Hofmeister effect, we measured the rate cell growth of S. aureus—a halophilic pathogenic bacterium—and of P. aeruginosa, an opportunistic pathogen, in the presence of different aqueous salt solutions at different concentrations (0.2, 0.6 and 0.9 M). Microorganism growth rates depend strongly on the kind of anion in the growth medium. In the case of S. aureus, chloride provides a favorable growth medium, while both kosmotropes (water structure makers) and chaotropes (water structure breakers) reduce the microorganism growth. In the case of P. aeruginosa, all ions affect adversely the bacterial survival. In both cases, the trends parallel the specific ion, or Hofmeister, sequences observed in a wide range of physico-chemical systems. The correspondence with specific ion effect obtained in other studies, on the activities of a DNA restriction enzyme, of horseradish peroxidase, and of Lipase A (Aspergillus niger) is particularly striking. This work provides compelling evidence for Hofmeister effects, physical chemistry in action, in these organisms.

Effects of ion species in aqueous phase on protein extraction into reversed micellar solution

We investigated the effect of cations on the protein extraction into AOT/isooctane reversed micellar solutions using alkaline and alkaline-earth metal ions. Cations greatly influenced the extraction ratio of protein in an order of K + <Rb + <Cs + <Na + <Li + in monovalent ions and Ba 2+ <Sr 2+ <Ca 2+ in divalent ones. Besides, the extraction ratio is totally higher in divalent ions than in monovalent ones. This effect of ions can be explained by classifying cations into water-structure forming and water-structure breaking ions. The effect of anions is less than that of cations and is in an order of SCN − <Br − <Cl − , consistent with that of lyotropic series. In addition, the extraction ratio is higher for proteins of higher hydrophobicity and it is supposed that the hydrophobicity and stability of the protein–surfactant complex are related to extraction efficiency.

Effect of urea, dimethylurea, and tetramethylurea on the phase behavior of dioleoylphosphatidylethanolamine

The phase behavior of dioleoylphosphatidylethanolamine in aqueous solutions of urea, N, N′-dimethylurea (DMU), and N, N, N′, N′-tetramethylurea (TMU) has been characterized by synchrotron X-ray diffraction and differential scanning calorimetry. All three solutes stabilize the lamellar liquid-crystalline phase at the expense of lamellar-gel phase and inverted hexagonal phase of the phospholipid when present in concentrations up to 3 M. X-ray diffraction data demonstrated that the repeat spacing of DOPE increased with increasing urea concentration, but decreased as the DMU and TMU concentrations increased. The repeat spacing of DOPE in the liquid-crystal phase dispersed in the three solutes is d(urea)> d(DMU)> d(TMU). The molecular mechanisms underlying these observations are discussed in terms of either membrane Hofmeister effect, where urea acts as a water structure breaker, or a direct insertion effect of the amphiphilic DMU and TMU molecules into the lipid head groups in the interfacial region of the phospholipid bilayer.

The use of water structure breakers, urea and guanidium chloride, new mobile phase modifiers in reversed-phase partition high-performance liquid chromatography.

Organic solvent-free mobile-phase systems in ion-pair reversed-phase partition high-performance liquid chromatography (IPRP-HPLC) are demonstrated; using urea at 3.0-7.0 molal (mol kg-1) as a modifier in a mobile phase on an octadecylsilanized silica column, four nitrophenolates and metal 4-(2-pyridilazo)resorcinol (PAR) chelates (in PAR chelates system an aqueous mobile phase with 15 wt% methanol was used) were separated rapidly within 6 min at no sacrifice to the separation efficiency. On the addition of urea in the mobile phase, reduced retention times of nitrophenolates and naphthalenesulfonates and also diminution of the height equivalent to a theoretical plate were observed. The addition of urea and guanidium chloride (GuCl) in the mobile phase gave rise to a decrease in the mobile phase volume; in turn, this meant an increased volume of the stationary phase. As the concentration of urea and GuCl in the mobile phase increased, the volume of the mobile phase in the column decreased within about 70% and 40% at 7.0 molal of urea and GuCl, respectively. A decrease in the mobile phase volume suggests an increase in the extent of solvation of the bonded hydrocarbon chain of the stationary phase. The possible explanations for the LC behavior with the urea and GuCl are turned into reduction of hydrophobic interaction in LC processes, solute partitioning and entangling of alkyl chain brushes, with the addition of urea. The water structure breakers, urea and GuCl, most likely affect the solvation states of both solute molecules and the hydrocarboneous stationary phase by changing the nature of the water solvent, which provides a new technique for fine tuning of the LC resolution of the analytes.

The flotation chemistry of potassium double salts: Schoenite, kainite, and carnallite

It is known from soluble salt flotation practice that the K, Mg double salts of kainite (KClMgSO 43H 2O), and carnallite (KClMgCl 26H 2O) are difficult to float and must be converted to other salts such as schoenite (K 2SO 4MgSO 46H 2O) and sylvite (KCl) in order to recover potash values. The flotation characteristics of these double salts have now been confirmed in some detail by carefully controlled laboratory experiments with both cationic and anionic collectors. The experimental results are discussed in view of recent experimental findings regarding the flotation characteristics of simple salts, in which the flotation response was shown to be determined by the interfacial water structure and whether the salt could be considered to be a water structure maker or a water structure breaker. The same approach can be use to explain the flotation response of the potassium double salts; schoenite, kainite, and carnallite. In addition, the sign of the surface charge of schoenite (K 2SO 4MgSO 46H 2O), was determined as a function of pH from nonequilibrium electrophoretic mobility measurements. Schoenite appears to exhibit three charge reversals (CR) which can be explained based on surface hydrolysis reactions. The flotation behavior of schoenite is further considered based on solution chemistry calculations, electrophoretic mobility measurements, and microflotation results.

On the Salt-Induced Activation of Lyophilized Enzymes in Organic Solvents: Effect of Salt Kosmotropicity on Enzyme Activity

The dramatic activation of enzymes in nonaqueous media upon co-lyophilization with simple inorganic salts has been investigated as a function of the Jones−Dole B coefficient, a thermodynamic parameter for characterizing the salt's affinity for water and its chaotropic (water-structure breaking) or kosmotropic (water-structure making) character. In general, the water content, active-site content, and transesterification activity of freeze-dried subtilisin Carlsberg preparations containing >96% w/w salt increased with increasing kosmotropicity of the activating salt. Degrees of activation relative to the salt-free enzyme ranged from 33-fold for chaotropic sodium iodide to 2480-fold for kosmotropic sodium acetate. Exceptions to the general trend can be explained by the mechanical properties and freezing characteristics of the salts undergoing lyophilization. The profound activating effect can thus be attributed in part to the stabilizing (salting-out) effect of kosmotropic salts and the phenomenon of preferential hydration.

Effect of Salts on the Micellization, Clouding, and Solubilization Behavior of Pluronic F127 Solutions

We have examined the effect of NaCl, Na2SO4, Na3PO4, and NaSCN on F127 solutions; properties examined were critical micellization temperature (cmt), cloud point, and solubilization of a model hydrophobic drug, propyl paraben. Static light scattering showed that the first three salts lower the cmt of F127 in the order Na3PO4>Na2SO4>NaCl. The extent of lowering depends on the salt concentration and can be ascribed to the water structure-making properties of these salts. NaSCN, a water structure breaker, was found to increase cmt. Pyrene fluorescence was used to study the changes in micellar interior in the presence of salts. We found that the micellar micropolarity is not significantly changed by salts, evidenced by a constant I1/I3 ratio of pyrene. However, the Ie/I3 ratio changes significantly with salts, being lower for NaCl, Na2SO4, and Na3PO4 and higher for NaSCN. This is consistent with an increase in the total hydrophobic micellar domain, in micellar microviscosity, or both. Solubilization of propylparaben increases in the presence of Na3PO4, consistent with a larger hydrophobic domain for solubilization. The thermodynamics of micellization continue to be entropically driven in the presence of salts, evidenced by a positive entropy overcoming an unfavorable enthalpy.