CALCULATION OF TRANSLATIONAL FRICTION AND INTRINSIC-VISCOSITY .2. APPLICATION TO GLOBULAR-PROTEINS

The translational friction coefficients and intrinsic viscosities of f our globular proteins (ribonuclease A, lysozyme, myoglobin, and chymot rypsinogen A) are calculated using atomic-level structural details. In clusion of a 0.9-Angstrom-thick hydration shell allows calculated resu lts for both hydrodynamic properties of each protein to reproduce expe rimental data. The use of detailed protein structures is made possible by relating translational friction and intrinsic viscosity to capacit ance and polarizability, which can be calculated easily. The 0.9-Angst rom hydration shell corresponds to a hydration level of 0.3-0.4 g wate r/g protein. Hydration levels within this narrow range are also found by a number of other techniques such as nuclear magnetic resonance spe ctroscopy, infrared spectroscopy, calorimetry, and computer simulation . The use of detailed protein structures in predicting hydrodynamic pr operties thus allows hydrodynamic measurement to join the other techni ques in leading to a unified picture of protein hydration. in contrast , earlier interpretations of hydrodynamic data based on modeling prote ins as ellipsoids gave hydration levels that varied widely from protei n to protein and thus challenged the existence of a unified picture of protein hydration.