Solution thermodynamic approach to analyze protein stability in aqueous solutions.

Protein thermal stability was analyzed by a solution thermodynamic approach. The small energetic differences in hydrogen-bonds (HB) among amino acid resdues and water molecules were proved to be amplified by the large number of HB involved to bring about the equilibrium shift from folding to unfolding of proteins. In aqueous solutions, water activity (A) plays a key role in protein stability.

Enhanced Adsorption of a Protein-Nanocarrier Complex onto Cell Membranes through a High Freeze Concentration by a Polyampholyte Cryoprotectant.

The transportation of biomolecules into cells is of great importance in tissue engineering and as stimulation for antitumor immune cells. Previous freezing strategies at ultracold temperatures (-80 °C) used for intracellular transportation exhibit certain limitations such as extended time requirements and harsh delivery system conditions. Thus, the need remains to develop simplified methods for safe nanomaterial delivery.

Static and dynamic half-life and lifetime molecular turnover of enzymes.

The static half-life of an enzyme is the half-life of a free enzyme not working without substrate and the dynamic half-life is that of an active enzyme working with plenty amount of substrate. These two half-lives were measured and compared for glucoamylase (GA) and β-galactosidase (BG). The dynamic half-life was much longer than the static half-life by one to three orders of magnitude for both enzymes.

Cooperative hydration effect causes thermal unfolding of proteins and water activity plays a key role in protein stability in solutions.

The protein unfolding process observed in a narrow temperature range was clearly explained by evaluating the small difference in the enthalpy of hydrogen-bonding between amino acid residues and the hydration of amino acid residue separately. In aqueous solutions, the effect of cosolute on the protein stability is primarily dependent on water activity, aw, the role of which has been long neglected in the literature. The effect of aw on protein stability works as a power law so that a small change in aw is amplified substantially through the cooperative hydration effect.

Thermodynamic analysis of sol-gel transition of gelatin in terms of water activity in various solutions.

Sol-gel transition of gelatin was analyzed as a multisite stoichiometric reaction of a gelatin molecule with water and solute molecules. The equilibrium sol-gel transition temperature, Tt , was estimated from the average of gelation and melting temperature measured by differential scanning calorimetry. From Tt and the melting enthalpy, ΔHsol , the equilibrium sol-to-gel ratio was estimated by the van't Hoff equation.

Analysis of hydration parameter for sugars determined from viscosity and its relationship with solution parameters.

The hydration parameter h was obtained from the viscosity B-coefficients and the partial molar volume of solute, V2, for various sugars and urea in aqueous solutions. The parameter h showed a good correlation with the parameter α, determined from the activity coefficient of water, representing the solute-solvent interaction. The parameter h also showed a good correlation with the number of equatorial-OH groups (e-OH) for sugars, suggesting that the sugar molecules with the higher e-OH fit more to the water-structure.

Thermodynamic analysis of osmolyte effect on thermal stability of ribonuclease A in terms of water activity.

Thermal unfolding of ribonuclease A (RNase) was analyzed in various osmolyte solutions of glycine, proline, sarcosine, N,N-dimethylglycine, betaine, myo-inositol, taurine, and trimethylamine-N-oxide (TMAO). All the osmolytes tested stabilized the protein. The thermal unfolding curve was described well by the van't Hoff equation and the melting temperature and the enthalpy of protein unfolding were obtained.

Thermodynamic analysis of alcohol effect on thermal stability of proteins.

Thermal unfolding of ribonuclease A and α-chymotrypsinogen A was analyzed in various alcohol solutions of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, trifluoroethanol, and glycerol. The change in thermal unfolding ratio with temperature was described well by the van't Hoff equation and the melting temperature and the enthalpy of protein unfolding were obtained. The reciprocal form of the Wyman-Tanford equation, which describes the unfolded-to-folded protein ratio as a function of water activity, was applied to obtain a linear plot.

Thermodynamic analysis of protein unfolding in aqueous solutions as a multisite reaction of protein with water and solute molecules.

Thermal unfolding of ribonuclease A, lysozyme, and chymotrypsinogen A was analyzed as a multisite reaction of a protein molecule with water and solute molecules. The protein unfolding process in various solutions of sugars and denaturants was described well by the van't Hoff equation. The reciprocal form of the Wyman-Tanford equation, which describes the unfolded-to-folded protein ratio as a function of water activity, was successfully applied to obtain a good linear relationship.

PFG-NMR study for evaluating freezing damage to onion tissue.

We assessed the damage to onion tissue due to freeze-thawing as the water permeability determined by using PFG-NMR and light microscopy. The water diffusion in fresh onion tissue was restricted due to cellular barriers, and the estimated water permeability was 6.99 x 10(-6)m/s.

Lipase-catalyzed butanolysis of triolein in ionic liquid and selective extraction of product using supercritical carbon dioxide.

The lipase-catalyzed butanolysis of triolein was carried out in an ionic liquid, methyltrioctylammonium trifluoroacetate (MTOATFA). The addition of 80% MTOATFA to the reaction system gave the best result in terms of alcoholysis rate. The final product (butyloleate) was selectively extracted from the reaction mixture using supercritical carbon dioxide.

Hydration state change of proteins upon unfolding in sugar solutions.

Change in hydration number of proteins upon unfolding, Deltan, was obtained from the analysis of thermal unfolding behavior of proteins in various sugar solutions with water activity, a(W), varied. By applying the reciprocal form of Wyman-Tanford equation, Deltan was determined to be 133.9, 124.

A modified model for non-newtonian viscosity behavior of Aureobasidium pullulans culture fluid.

The culture fluid of the fungus Aureobasidium pullulans and the exopolysaccharide solution obtained by removal of the microbial cells exhibit a marked shear dependence of viscosity. The viscosity in a high shear rate region was a little higher than that predicted by a non-Newtonian viscosity equation derived previously on the basis of the concept of traveling force. In a sample exhibiting such high shear rate dependence, a hydrodynamic effect based on the fluid structure of the binding of contacting polymers and suspended microbial cells on viscosity becomes comparatively significant.

Characteristic behavior of viscosity and viscoelasticity of Aureobasidium pullulans culture fluid.

Measurements of dynamic viscoelasticity and steady flow viscosity were made for culture fluids obtained by cultivation of Aureobasidium pullulans IAM 5060 with initial pHs of 6 and 7 and for exopolysaccharide (EPS) solutions obtained by removal of microbial cells. The molecular weight of EPS of the pH 6 culture is about 850,000, and that of the pH 7 culture is much larger. In the present study, the complex viscosity shifted to a considerably larger value than that of the steady flow viscosity.

Effect of water potential on sol-gel transition and intermolecular interaction of gelatin near the transition temperature.

The sol-gel transition of gelatin, measured by thermal analysis and viscosity measurement, was analyzed in terms of the change in hydration state of polymer molecules. A new thermodynamic model was proposed in which the effect of water potential is explicitly taken into account for the evaluation of the free energy change in the sol-gel transition process. Because of the large number of water molecules involved and the small free energy change in the transition process, the contribution of water activity, a(W), was proved to be not negligible in the sol-gel transition process in solutions containing such low-molecular cosolutes as sugars, glycerol, urea, and formamide.

Relationship between the electrical and rheological properties of potato tuber tissue after various forms of processing.

The impedance at frequencies of 1-1000 kHz and dynamic bending storage modulus measured by the vibrating reed method were compared for potato tuber tissue, which had been processed by various methods. Raw potato tuber tissue strips were either heated for 30 min up to 100 degrees C or frozen-thawed. Some samples were osmotically dehydrated in a mannitol solution up to a concentration of 0.