Slope Of Tie-line Research Articles

Molybdate ion partition in the aqueous two-phase system formed by CuSO4 + PEG 4000 + H2O at different pH and temperatures

In this study, the aqueous two-phase system (ATPS) formed by CuSO4+PEG 4000+H2O, for the partition of the molybdate ion at different pH values (1.5, 2.0 and 2.5) and at five different temperatures, T=(298.15, 308.15, 318.15, 328.15 and 338.15) K was studied. Two different salts, Na2MoO4 and (NH4)6Mo7O24, were used for the experimental partition tests. The extraction percent for the molybdate ion in the ATPS was studied as a function of pH and temperature. The experimental results indicate that the extraction percent increases with increasing temperature. The maximum extraction reached was 93.07% at pH=2.5 and T=338.15K, for the CuSO4+PEG+H2O+Na2MoO4 system, and 92.66% in the CuSO4+PEG+H2O+(NH4)6Mo7O24 system at pH=2.5 and T=318.15K.In addition, the pH effect on the liquid-liquid equilibria of the ATPS CuSO4+PEG+H2O at T=308.15K was studied, where no significant influence was observed in the working pH range (from 1.5 to 2.5). However, if it is compared with the literature data, it has a relevant importance. With decreasing pH, the two-phase area decreases, thus the tie-line slope also varied.Chen-NRTL and Wilson modified models were applied to correlate the liquid-liquid equilibrium. A good agreement between experimental data and correlated results was obtained.

Novel Aqueous Two-Phase System Consisting of 1,4-Bis(2-hydroxypropyl)-piperazine, Na2SO4, and H2O: Temperature-Dependent Equilibrium Data and Physical Properties

In this work, we have developed a novel aqueous two-phase system (ATPS) composed of 1,4-bis(2-hydroxypropyl)-piperazine (HPP), Na2SO4, and H2O, which can determine the liquid–liquid equilibrium and phase diagrams at the temperatures of 303.15–323.15 K. Simultaneously, the physical properties such as density, viscosity, refractive index, and surface tension have been determined for the top phases and bottom ones of the ATPS. The results indicate that temperature has no significant effect upon the biphasic region, implying a small enthalpy contribution during phase separation. However, the changes in temperature result in a decrease of tie line slope, because H2O molecules are transferred from the bottom phase to the top phase. In determining the physical properties of the system, viscosity and refraction index increase with the system components increasing, during the phase of both HPP and Na2SO4, while density and surface tension fall with the increase of system components in the top phase and decrease in...

Estimation of liquid‐liquid equilibrium of type 2 systems (water + valeric acid + monobasic ester or dibasic ester or alcohol) using SERLAS, SERLAS‐modified, and SERLAS‐integrated

This paper studies liquid‐liquid equilibrium (LLE) of the type 2 systems (water + valeric acid + dibasic ester or monobasic ester or alcohol) at T = (298.2 ± 0.1) K and p = (101.3 ± 0.7) kPa. Equilibrium distribution of valeric acid onto (water + solvent) two‐phase system is better for more structured diethyl sebacate and ethyl caprylate as compared to less structured diethyl succinate, diethyl malonate, ethyl valerate, and isoamyl alcohol. The two‐phase envelope size and the tie line slope on the phase diagrams are varying as follows: ethyl caprylate > diethyl sebacate > ethyl valerate > diethyl succinate ≈ diethyl malonate > isoamyl alcohol. The SERLAS‐integrated (solvation energy relation for liquid associated systems‐integrated) molecular model with nine physical descriptors, originated from LSER (linear solvation energy relation) principles in conjunction with group‐contribution method, is proposed and applied to the prediction of type 2 LLE properties. By combining SERLAS with UNIFAC‐Dortmund, we are able to get along with a simultaneous impact of both methods for satisfactorily simulating type 2 phase behaviour so long as solvent effects are concerned. SERLAS, SERLAS‐modified, SERLAS‐integrated, and UNIFAC‐original models have been stringently tested for consistency in reproducing phase equilibrium properties with average deviations inferior to 28.8 %, 44.3 %, 21.3 %, and 30.4 %, respectively.

Measurement and correlation of phase equilibria in aqueous two-phase systems containing polyethyleneglycol (2 000, 4 000, and 6 000) and sulfate salts (manganese sulfate and copper sulfate) at different temperatures (298.15, 318.15, and 338.15 K)

Liquid–liquid equilibrium (LLE) data were obtained for polyethylene glycol (PEG)-salt aqueous two-phase system (ATPS) at 298.15, 318.15 and 338.15 K. Two salts, copper sulfate and manganese sulfate, and PEG with different molecular weights, 2 000, 4000 (manganese sulfate only), and 6 000, were used. The effects of the molecular weight of PEG and temperature on phase separation and the salting-out effect were studied. For all aqueous two-phase systems, the increase in the polymer molecular weight provides a larger biphasic region. The temperature promoted an increase in the biphasic region, and the slope of tie-lines tended to decrease with increasing temperature. The Setschenow-type equation was used to evaluate the salting-out effect of MnSO4 and CuSO4, as well as the temperature and molecular weight of the PEG influence on the phase formation. The rank order of salting-out coefficients is Mn2+ > Cu+2 since the cation Mn2+ is more kosmotropic than Cu2+. NRTL and UNIQUAC models have been used to fit the 18 experimental LLE data. The interaction parameters of the models were estimated. The results show that the quality of fitting is better with the UNIQUAC model.

Modeling phase equilibria of ternary systems (water + formic acid + ester or alcohol) through UNIFAC-original, SERLAS, NRTL, NRTL-modified, and three-suffix Margules: Parameter estimation using genetic algorithm

Ternary liquid-liquid equilibrium (LLE) systems composed of (water + formic acid + ester or alcohol), exhibiting experimental phase diagrams of type 1, have been studied at T = (298.2 ± 0.1) K and P = (101.3 ± 0.7) kPa. The equilibrium distribution of formic acid onto (water + solvent) two-phase system is better for dibasic ester (diethyl sebacate, diethyl succinate) as compared to monobasic ester (ethyl caprylate, ethyl valerate) and isoamyl alcohol. The thermodynamic models SERLAS, UNIFAC-original, NRTL, NRTL-modified and three-suffix Margules have been deeply tested for consistency in simulating the ternary LLE behavior. An immediate goal is to estimate the interaction parameters of molecular models from ternary data only using a genetic algorithm. The genetic algorithm identifies globally optimal values by producing a population of candidate solutions from given upper and lower bounds of the interaction parameters. The reliability of existing models has been analyzed statistically with respect to three physical extraction factors. Essentially, SERLAS, UNIFAC-original, NRTL, NRTL-modified and three-suffix Margules yield mean errors of 3.4%, 19.4%, 4.2%, 4.4% and 8.6%, respectively, enabling the ternary phase behavior to be simulated satisfactorily. The UNIFAC-original prediction is moderately precise. NRTL is especially effective in correlating both the two-phase envelope size and the tie line slope. While SERLAS has proven reasonably successful in reproducing the physical extraction factors, yielding about equally accurately estimates for each ternary system.

Aqueous two-phase (polyethylene glycol + sodium sulfate) system for caffeine extraction: Equilibrium diagrams and partitioning study

Environmental friendly methods for liquid–liquid extraction have been taken into account due to critical conditions and ecotoxicological effects potentially produced by organic solvents applied in traditional methods. Liquid–liquid extraction using aqueous two phase systems (ATPSs) presents advantages when compared to traditional liquid–liquid extraction. (Polyethylene glycol (PEG)+sodium sulfate+water) ATPS was applied to study partition of caffeine. Binodal curves for ATPSs composed of PEG of different molecular weights (400g·mol−1, 4000g·mol−1 and 6000g·mol−1) sodium sulfate+water were determined by cloud point method at three different temperatures (293.15, 313.15 and 333.15)K. Liquid–liquid equilibrium (LLE) data (tie-lines, slope of the tie-line and tie-lines length) were obtained applying a gravimetric method proposed by Merchuck and co-workers at the same temperatures for aqueous (PEG 400+sodium sulfate) and aqueous (PEG 400+sodium sulfate+caffeine) systems. Reliability of the experimental tie-line (TL) data was evaluated using the equations reported by Othmer–Tobias and satisfactory linearity was obtained. Concerning to aqueous (PEG+sodium sulfate) system, the results pointed out that the higher PEG molecular weight the largest is the heterogeneous region. Moreover, temperature showed not to be relevant on binodal curves behavior, but it influenced on tie-line slopes. Partitioning of caffeine in aqueous (PEG 400+sodium sulfate) system was investigated at different temperatures and tie-lines lengths (TLLs). It was shown that the partitioning was depended on the temperature and TLL and at all conditions studied the salting out effect displayed higher influence leading caffeine partition preferentially into the PEG rich (top) phase.

Liquid–liquid equilibria, electrical conductivity, and refractive indices of Poly(ethylene glycol) + sodium sulfate + guanidine hydrochloride aqueous two-phase systems: Correlation and thermodynamic modeling

The initial recovery steps for recombinant protein were carried out using aqueous two-phase systems in the presence of guanidine hydrochloride. To investigate the phase behavior of such systems, equilibrium data was obtained for molecular weight fractions of PEG (3000 and 6000) + sodium sulfate (pH 7) + guanidine hydrochloride (5% and 10% mass) + water at 25 °C. Displacement of the binodal toward higher concentrations through an increase in guanidine hydrochloride concentration was clearly observed. A slightly larger two-phase was obtained as the PEG molecular weight increased from PEG 3000 to 6000. The experimental binodal data of the system was successfully correlated with Bleasdale equations (high R2 and low SE). The effects of molecular weight, guanidine hydrochloride concentration, tie-line length, and slope of tie-line on the partition behaviors of guanidine hydrochloride were examined at constant pH. The compositions of each aqueous phase were calculated using two thermodynamic models for the activity coefficient. The calculated results showed that the extended Pitzer and extended UNIQUAC models can predict the data in the quaternary system well. The fitted binary interaction parameters of the models were reported.

Equilibrium Data and Physical Properties of Aqueous Two Phase Systems Formed by PEG (1500 and 4000) g·mol–1 + Sodium Sulfate + Water at Different Temperatures and pH 2

Liquid–liquid equilibrium data and phase diagrams of aqueous two phase systems (ATPS) composed of polyethylene glycol (PEG) of molar mass (1500 and 4000) g·mol –1 + sodium sulfate + water were determined at temperatures of 293.15, 303.15, 313.15, and 323.15 K at pH 2. Temperature had no significant effect on the biphasic region, indicating a small enthalpic contribution in the phase separation process. The change in temperature however caused an increase in the tie line slope because water molecules were transferred from the upper phase to the lower phase. Increasing the molar mass of the polymer led to an increase in the biphasic region of the phase diagram. In determining the physical properties of the systems studied, it was observed that the increase in concentration increased the viscosity and the refraction index; while relative to temperature, the viscosity, refraction index, and density decreased.

Eutectoids with cementite as the major constituent in Fe–C–M alloys

The addition of a third element to hypereutectoid Fe–C alloys may cause inclusions of a minor constituent in the precipitate of cementite from austenite even if the initial austenite is supersaturated only with cementite. Cementite will often become the major constituent of this kind of microstructure. For Fe–C–Cu alloys this has been explained as the result of precipitation from supersaturated cementite. An alternative mechanism could be that the mixture of cementite and a minor constituent forms by simultaneous and cooperative growth of the two phases, i.e., by a reaction that may be regarded as eutectoid. This mechanism has already been applied to explain the occurrence of eutectoid colonies with cementite as the major constituent and a minor constituent for which there was no supersaturation initially.This phenomenon has been observed in hypereutectoid ternary Fe–C alloys with Al, Mn or Si. The necessary requirements on the ordinary isothermal phase diagram are now examined with a graphical method based on the slopes of tie-lines. It predicts the phenomenon in all cases where it has been observed, including Fe–C–Cu and not in the Fe–C–Ni and Fe–C–Cr systems where it has not been observed. The requirements become more evident when the calculated phase equilibria are plotted as an isothermal phase diagram with the alloy content as a function of the carbon activity instead of carbon content. Finally, a comparison is made with bainite in Fe–C alloys where ferrite is the major and cementite the minor constituent. The same two explanations have been proposed for that case.

Influence of Different Phase-Forming Parameters on the Phase Diagram of Several PEG–Salt Aqueous Two-Phase Systems

Different poly(ethylene glycol) (PEG) + potassium phosphate or sodium citrate aqueous two-phase systems (ATPS) were investigated at 23 °C, containing different PEG types (molecular weights 2000 g·mol–1 to 8000 g·mol–1) and pH values (5 to 9). Furthermore, the effect of the added salt NaCl (0 wt % to 8 wt %) on the PEG + potassium phosphate/sodium citrate ATPS was studied at 23 °C. The experimental binodal data were successfully correlated with the empirical nonlinear equation proposed by Hu. The effects of increasing molecular weight of PEG, pH, NaCl, and salt type on the obtained binodal curves were determined, resulting in a binodal curve shift toward the origin. Thus, an expansion of the two-phase region occurred by increasing molecular weight of the PEG, pH, and NaCl and due to the Gibbs free energy of hydration of ions of phosphate. Furthermore, the phase equilibrium compositions, tie-line lengths, slopes of tie-lines, critical points, and effective excluded volumes were obtained for all studied syst...

Prediction of partition coefficients of alkaloids in ionic liquids based aqueous biphasic systems using hybrid group method of data handling (GMDH) neural network

In this study, a hybrid GMDH–neural network model was developed in order to predict partition coefficients of alkaloids in aqueous biphasic system using different ionic liquids with the same inorganic salt. In order to accomplish this modeling, feed's weight percent compositions along with slope of tie-line (STL), tie-line length (TLL) and difference of molecular weight of salt and Ionic liquid were taken as the inputs and the desired partition coefficients (K) were estimated. Furthermore, the data set was divided into two parts: 80% of the data points were used for training and 20% for testing. For evaluation of the model's performance, partition coefficients obtained from the GMDH model were compared with their experimental values using different statistical measures. The proposed model can successively correlate and predict K-values and result a great agreement with the experimental data.

Phase Equilibrium of PEG 2000 + Triammonium Citrate + Water System Relating PEG Molecular Weight, Cation, Anion with Effective Excluded Volume, Gibbs Free Energy of Hydration, Size of Cation, and Type of Anion at (298.15, 308.15, and 318.15) K.

Phase equilibria of an aqueous two-phase system consisting of polyethylene glycol (PEG 2000) + triammonium citrate + water were determined at different temperatures (298.15, 308.15, and 318.15) K. The binodal curve moves toward the origin with an increase in temperature, resulting in an increase in the two-phase region with an increase in temperature. The effective excluded volume (EEV) of the above aqueous two-phase system was determined from the binodal data. The salting-out capacity of the system increases with the temperature and is explained by the increase of EEV with increase in temperature. The effect of PEG molecular weight, cation, and anion on the binodal curve was analyzed using EEV, Gibbs free energy of hydration (ΔGhyd), size of cation, and type of anions. The phase equilibrium compositions, tie-line length (TLL), and slope of tie-line (STL) were determined at (298.15, 308.15, and 318.15) K. The consistencies of the experimental equilibrium data were explained with the Othmer–Tobias and Bancroft equations. The salting-out coefficients were determined from tie-line compositions using Setschenow equation. The salting-out coefficient increases with the increase in temperature.

Experimental and numerical study of compositional two-phase displacements in layered porous media

This paper presents an experimental and numerical study to investigate the effects of viscous, capillary, and gravity forces on compositional two-phase displacements in layered porous media. We use glass bead packs of different sizes to construct a quasi 2-D porous medium of three layers with different uniform permeabilities. We adapt an analog ternary fluid system (isooctane, brine, and isopropanol) which allows us to control interfacial tension between the phases at ambient laboratory conditions. Flooding experiments mimic condensing drives and use immiscible and near miscible fluids from the analog ternary system. We report recovery of phases, compositional analysis, and snapshots of saturation distributions during each experiment.We show that the high flow capacity domain as defined by the high permeability layer and its thickness always dominate displacements. However, its degree depends on the location of the high-permeability layer and the balance between the driving forces. Compositional analysis of effluent indicates that the compositional path is slightly different for the low and high injection rates in the high interfacial tension (IFT) immiscible displacements whereas it is sensitive to the location of high-permeability layer in the low-IFT near-miscible floods. The Peclet numbers indicate the presence of dispersion in the experiments and crossflow affects the recoveries.We also perform black oil simulations to interpret the experimental observations. In general, we obtain consistent results between the experimentally measured and numerically obtained data. However, in order to account for the displacement physics and accurately predict the recovery performance, one may need to employ a fully compositional simulation model that captures the tie-line slopes correctly along with the transport properties and gravity. The compositional simulations can provide additional details in terms of component recoveries.

Measurement and Correlation of Phase Equilibria in Aqueous Two-Phase Systems Containing Polyoxyethylene Lauryl Ether and Diammonium Hydrogen Phosphate or Dipotassium Hydrogen Phosphate at Different Temperatures

The phase diagrams for the systems containing polyoxyethylene lauryl ether (Brij35) and K2HPO4/(NH4)2HPO4 have been determined experimentally at three temperatures, (288.15, 298.15, and 308.15) K. Three experiential equations were used to correlate the binodal data. The liquid–liquid equilibrium (LLE) data of these systems obtained by the experimental method were fitted by using Othmer–Tobias and Bancroft along with simple Setschenow-type equations. Furthermore, the effect of temperature on the binodal curve for the disquisitive systems has been discussed, and it was found that two-phase region expands with the increase in temperature, which is corresponded to the value of the effective excluded volume (EEV) calculated according to the binodal model. In the investigated systems, the free energy (ΔG), enthalpy change (ΔH), and entropy change (ΔS) were calculated, and it indicated that the phase separation processes are endothermic and driven by the entropy increase. That the slope of tie-line increases wit...

Impact of Self-Aggregation on the Formation of Ionic-Liquid-Based Aqueous Biphasic Systems

This work reports on the systematic investigation of the influence of the cation alkyl side-chain length of 1-alkyl-3-methylimidazolium chloride ionic liquids ([C(n)C(1)im]Cl, with n = 1-14), as well as the substitution of the most acidic hydrogen in the imidazolium core by a methyl group, in the formation of aqueous biphasic systems. Ternary phase diagrams, tie-lines, tie-line slopes, tie-line lengths, and critical points for the several systems (ionic liquid + water + K(3)PO(4)) were determined and reported at 298 K and atmospheric pressure. It is shown that the increase of the cation alkyl chain length enhances the formation of aqueous biphasic systems if alkyl chain lengths until the hexyl are considered. The results for longer alkyl side chains show, nevertheless, that the phenomenon is more complex than previously admitted and that the capacity of the ionic liquid to self-aggregate also governs its ability to phase separate. The effect of the alkyl side-chain length on the phase-forming ability of the studied systems was quantitatively evaluated based on their salting-out coefficients derived from a Setschenow-type behavior. The aptitude of each ionic liquid for liquid-liquid demixing as a function of the cation alkyl side-chain length clearly follows three different patterns. The results obtained for the trisubstituted cation indicate that the hydrogen-bonding interactions between the ionic liquid cation and water are not a relevant issue in the formation of aqueous two-phase systems. In general, for the [C(n)C(1)im]Cl series, a multifaceted ratio between entropic contributions and the ability of each ionic liquid to self-aggregate in aqueous media control the phase behavior.

Aqueous two-phase systems of copolymer L64 + organic salt + water: Enthalpic L64–salt interaction and Othmer–Tobias, NRTL and UNIFAC thermodynamic modeling

Phase diagrams of two-phase systems (ATPS) composed by the triblock copolymer L64 + organic salt (sodium tartrate, sodium succinate, sodium citrate, or ammonium citrate) + water, at different temperatures (278, 288, and 298 K) are presented in this work. Contrary to behavior of ATPS formed by inorganic salts, the study of the temperature influence in the liquid–liquid equilibrium behavior of L64–organic salts ATPS showed an exothermic character for phase separation process. Microcalorimetric measurements showed that this phase separation energy is around −0.2 kJ mol −1 for all organic salts. The module of slope of tie line (STL) tends to increase with an increase in temperature. The cation nature effect showed that the salt Na 3C 6H 5O 7 was more effective in promoting phase separation than (NH 4) 3C 6H 5O 7. The capacity of the different anions tested for inducing ATPS formation with L64 followed the order: C 6H 5O 7 3− > C 4H 4O 6 2− > C 4H 4O 4 2−. Because the salt–L64 interaction energy to be very similar, the cation and anion effects on the phase separation could be attribute to a process driven by entropy. The interaction parameters of the NRTL and UNIFAC models were estimated through the experimental data of all ternary systems. The results of the NRTL (with 64 tie-lines) and UNIFAC (with 27 tie-lines) were considered excellent with global root mean square deviations, respectively, of the 1.04% and 0.87%. The consistencies of the all tie-line experimental compositions were improved by applying the Othmer–Tobias correlation.

Equilibrium Phase Behavior of Triblock Copolymer + Sodium or + Potassium Hydroxides + Water Two-Phase Systems at Different Temperatures

Liquid−liquid equilibrium data for aqueous two-phase systems formed by a mixture of triblock copolymer L35 (Mn = 1900 g·mol−1), sodium hydroxide or potassium hydroxide, and water were measured as a function of four temperatures, (283.15, 293.15, 303.15, and 313.15) K. The influences of the temperature and cation on the behavior of these systems were analyzed. Temperature variation affected more intensively the tie-line slope than the binodal position. The exchange of sodium cation for the potassium also leads to an increase of the two-phase region of the diagrams in each studied temperature. The reliability of all the tie-line experimental data was ascertained by applying the Othmer−Tobias correlation. The interaction parameters of the NRTL model and UNIFAC model group-interaction parameter were estimated for the liquid−liquid equilibrium at temperatures between (283.15 and 313.15) K, with a total of 80 tie-lines for each model. The results of the predicted liquid−liquid equilibrium data by NRTL and UNIFA...

Liquid−Liquid Equilibria of Aqueous Biphasic Systems Composed of 1-Butyl-3-methyl Imidazolium Tetrafluoroborate + Sucrose/Maltose + Water

Phase behaviors of aqueous biphasic systems (ABSs) composed of 1-butyl-3-methyl imidazolium tetrafluoroborate ([bmim]BF4) + sucrose/maltose + water were reported in this work. Phase diagrams, including binodal curves, tie-lines, and the slope of tie-line (STL) were obtained at temperatures of T = (278.15, 288.15, 298.15, and 308.15) K. The binodal curve data were correlated using an empirical equation, and the tie-line data were correlated according to Othmer−Tobias and Bancroft equations. Good agreements with the experimental data were obtained, and results showed that these equations can be satisfactorily used to correlate the experimental data of the investigated systems at the given temperatures.

Liquid Phase Equilibria for Mixtures of (Water + Morpholine + Ethyl Nonanoate, Dimethyl Phthalate, or Isoamyl Alcohol) at 298.15 K

This work reports liquid−liquid equilibrium (LLE) data for the mixtures {water (1) + morpholine (2) + ethyl nonanoate, dimethyl phthalate, or isoamyl alcohol (3)} at 298.15 K and 101.3 kPa. The solubility curves and tie-line end compositions were examined for the related mixtures. The reliability of the experimental tie-line data was verified by using the Othmer−Tobias correlation. Distribution coefficients and separation factors were evaluated for the immiscibility region. Although all of the proposed solvents show low distribution coefficients, they can be served as convenient agents for extracting morpholine from aqueous medium, since they exhibit high separation factors. The experimental tie-line data were correlated by universal quasichemical activity coefficient (UNIQUAC) model representing the LLE data for these systems with respect to tie-line slopes only.

Thermodynamic Studies on the Cataract-Associated Mutant, E107a, of Human Gamma-D Crystallin: Molecular Basis for Cataract Formation

The E107A mutation in human gammaD-crystallin (HGD) is associated with nuclear cataract. The concentration of crystallins in the lens is extremely high, approaching that within protein crystals. The composition in the lens nucleus, i.e. the central core, is such that the alpha- and gamma crystallin weight fractions are comparable. In earlier studies we showed that mutations in HGD dramatically compromised protein solubility, while maintaining the overall protein structure. In contrast, in the E107A mutation neither the structure (circular dichroism and tryptophan fluorescence emission) and stability (thermal denaturation), nor the solubility are affected significantly. However, as expected, the mutation raises the pI by ∼1 pH unit, i.e. from 7.4 to 8.4. The increase in pI suggested a change in the interaction of E107A with alpha crystallin, which is negatively charged at neutral pH. To determine changes in such interaction, we compared the liquid-liquid phase boundaries in binary mixtures containing either HGD or E107A, and alpha crystallin. Our preliminary studies show that while the phase-separation temperatures of mixtures in the two cases (i.e. HGD+alpha and E107A+alpha) remain comparable, the nature of the paired compositions of the two phases in equilibrium are distinct. In particular, the tie-line slopes are altered in the direction predicted to correspond to increased alpha-gamma attraction, on the basis of molecular dynamics simulation and thermodynamic perturbation theory (1). Thus, it appears that increased attractive interactions between the E107A mutant of HGD and alpha crystallin could destabilize the crystallin mixture in the lens nucleus, and lead to increased light scattering and cataract.(1) N. Dorsaz, G. M. Thurston, A. Stradner, P. Schurtenberger and G. Foffi, J. Phys. Chem. B 113:1693-1709 (2009)Supported by: NIH Grant EY 18249-01 (G.T.) and EY 10535 (J.P.)