High-pressure effects on oxidation of nitrosylmyoglobin

The rate of oxidation of nitrosylmyoglobin by oxygen decreases with increasing hydrostatic pressure. At 15 °C in air-saturated solution with ionic strength 0.16 and pH 6.8 (tris-buffer), the first-order rate constant is smaller by a factor of 5 at 300 MPa compared to ambient conditions. The pressure-effect on rate is not primarily caused by protein denaturation, as the presence of urea (up to 4 M) at ambient pressure increases the rate of oxidation. From rate/pressure data a volume of activation of +8 ml·mol(-1) and a compressibility coefficient of activation of -3 × 10(-8) ml·mol(-1) Pa(-1) is estimated.