This study was conducted to assess the effect of high hydrostatic pressure on monomer beta-lactoglobulin (BLg) at acid pH by fluorescence spectroscopy under pressure and by circular dichroism (CD) and (1)H NMR spectroscopies after release of pressure. The intrinsic (tryptophan) fluorescence measurement and the study of 8-anilinonaphthalene-1-sulfonate (ANS) binding to BLg indicated that at pH 2.0 the recovery of center of spectral mass or ANS fluorescence was almost complete upon pressure release. No difference in (1)H NMR spectra was observed between pressurized and unpressurized BLg. In addition, NMR detection of the H/D exchange of aromatic protein indicated that the conformation of the vicinity of tryptophan residues could be refolded almost completely after release of pressure. These results seemingly confirm that the pressure-induced denaturation of BLg at pH 2.0 is reversible. However, cis-parinaric acid binding ability of pressurized BLg was largely lost, although its retinol binding ability was the same as its unpressurized one. Furthermore, CD spectra of the far-UV region and 2D NMR spectra evidently revealed the difference in the conformation of the molecule between unpressurized and pressurized BLg. These results are interpreted as an existence of partially fragile structure in the BLg molecule by high pressure.

] made a thorough study of the e ect of pressure on G-and F-actins. However, all of the measurements in their study were made after the release of pressure. In the present experiment in situ observations were attempted by using eATP to obtain further detailed kinetic and thermodynamic information about the behaviour of actin under pressure. The dissociation rate constants of nucleotides from actin molecules (the decay curve of the intensity of¯uorescence of eATP-G-actin or eADP±F-actin) followed ®rst-order kinetics. The volume changes for the denaturation of G-actin and F-actin were estimated to be )72 mLámol )1 and )67 mLámol )1 in the presence of ATP, respectively. Changes in the intensity of¯uorescence of F-actin whilst under pressure suggested that eADP±F-actin was initially depolymerized to eADP±G-actin; subsequently there was quick exchange of the eADP for free eATP, and then polymerization occurred again with the liberation of phosphate from eATP bound to G-actin in the presence of excess ATP. In the higher pressure range (> 250 MPa), the partial collapse of the three-dimensional structure of actin, which had been depolymerized under pressure, proceeded immediately after release of the nucleotide, so that it lost the ability to exchange bound ADP with external free ATP and so was denatured irreversibly. An experiment monitoring eATP¯uorescence also demonstrated that, in the absence of Mg 2+ -ATP, the dissociation of 1 actin-heavy meromyosin (HMM) complex into actin and HMM did not occur under high pressure.

The equilibrium swelling curves of poly(N-isopropylacrylamide) gel are measured in four binary mixed solvent systems of water and organic alcohols. The organic alcohols chosen here are methanol, ethanol, 1-propanol, and 2-propanol, respectively. The re-entrant equilibrium swelling curves are obtained in these four binary mixed solvent systems of water and alcohols. The gel collapses into compact state when the concentration of alcohol is increased from water. The gel, then, swells again if the concentration of alcohol is increased further. The collapse transition of the gel occurs at the mole fraction of organic alcohol of X., = 0.04 except for the system of methanol and water in which the collapse transition of the gel occurs at X., = 0.14. We find that the re-swelling processes of the gel, in these binary mixed solvent systems, strongly depend on the species of the organic alcohols used.

To elucidate the synergistic effects of gelatin, thiourea, and chloride ions on the surface roughness, throwing power, and polarization curves for Cu deposition from electrore ning solutions, Cu electrodeposition was performed at a current density of 200 A•m −2 and a charge of 5 × 10 5 C•m −2 in an unagitated sulfate solution containing 0.708 mol•dm −3 of CuSO 4 and 2.04 mol•dm −3 of H 2 SO 4 at a temperature of 60 C. In solutions containing all three additives (gelatin, thiourea, and chloride ions), the surface roughness of deposited Cu decreased with increasing thiourea and gelatin concentrations and decreasing chloride ions concentration. On the other hand, the throwing power of deposited Cu improved with decreasing thiourea concentration and increasing gelatin concentration in solutions containing all three additives. The throwing power of deposited Cu was signi cantly improved in solutions containing both gelatin and chloride ions. The polarization resistance dE/di for Cu deposition increased in solutions containing both gelatin and chloride ions, resulting in an improvement in the throwing power of Cu deposition. As small amounts of thiourea have a depolarization effect on Cu deposition, a smoothing effect is expected to result from the promotion of deposition at recesses.