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We investigated ultrastructural changes in the yeast Saccharomyces cerevisiae when exposed to compressed ethylene gas. Transmission electron microscopy (TEM) revealed that intracellular organelles in yeast cells treated with compressed ethylene at up to 0.640 MPa (6.4 atm), especially the nuclear and plasma membranes, were seriously damaged.

A standalone-type beryllium (Be) high-pressure crystallography vessel has been developed. Using a coupler-joint unit and a pressure valve, we could keep the pressure in the vessel constant at 100+/-1 MPa for more than 24 h without connecting to a pressure-generating apparatus. Diffraction spots of a glucose isomerase (GI) crystal under 100 MPa were collected using the vessel and a rotating copper-anode in-house x-ray generator (0.8 kW). We successfully collected a 2.0 A resolution data set of a 0.5 mm size GI crystal in an aqueous solution at 100 MPa.

The inhibitory action of compressed hydrocarbon gases on the growth of the yeast Saccharomyces cerevisiae was investigated quantitatively by microcalorimetry. Both the 50% inhibitory pressure (IP(50)) and the minimum inhibitory pressure (MIP), which are regarded as indices of the toxicity of hydrocarbon gases, were determined from growth thermograms. Based on these values, the inhibitory potency of the hydrocarbon gases increased in the order methane << ethane < propane < i-butane < n-butane. The toxicity of these hydrocarbon gases correlated to their hydrophobicity, suggesting that hydrocarbon gases interact with some hydrophobic regions of the cell membrane. In support of this, we found that UV absorbing materials at 260 nm were released from yeast cells exposed to compressed hydrocarbon gases. Additionally, scanning electron microscopy indicated that morphological changes occurred in these cells.

The activation volume, Δ V‡, of the solute incorporation process at the kink site of a glucose isomerase (GI) crystal was estimated using the pressure dependency of the step kinetic coefficient, βstep, and the three-dimensional nucleation rates J of GI crystals were analyzed using classical nucleation theory. Δ V‡ took a negative value. The sticking parameter, s, for the addition of a GI tetramer to a critical nucleus drastically increased with increasing pressure. This was probably due to the decrease in the activation energy needed for the addition of the GI tetramer. [ABSTRACT FROM AUTHOR]

Abstract: We measured the temperature dependence of the solubility, C e , of triclinic lysozyme crystals on temperature at two pressures (0.1 and 100MPa) and five pHs (4.3, 4.4, 4.5, 4.6, and 4.7) by in situ observation of the morphological changes in the crystals. The solubility increased with increase in temperature and pressure. The enthalpies of dissolution (ΔH) decreased with increase in pressure when we used the same 50mM sodium acetate buffer solution (pH=4.5 at 0.1MPa). The effects of pH on solubility were somehow complicated. Although the solubilities at pH 4.7 did not differ from those at pH 4.5, those at pH 4.3 were significantly larger than those at pH 4.5. Since the pH of an acetate buffer is known to decrease from 4.71 to 4.52 at 98.1MPa and 25°C , the pH of the acetate buffer (pH 4.5 at 0.1MPa) decreased to pH∼4.3 as pressure increased to 100MPa. Thus, from the viewpoint of “constant pH”, ΔH increased with increase in pressure, since ΔH at pH 4.3 and 0.1MPa was smaller than that at 100MPa. This inconsistency is probably due to the change in the hydration state of the crystal and solution with decreasing pH (from 4.5 to 4.3). [Copyright &y& Elsevier]