Control of reduction potential by protein matrix: Lesson from a spherical protein model

Factors that contribute to the control of reduction potential by protein matrix are examined within a spherical protein model. These include the nonpolar nature of protein matrices, solvent accessibility of the redox center, and net charges and dipoles of surrounding amino acids. Simple rules on their effects are established. In particular, surface charges have little effect on the reduction potential, and polar groups may either increase or decrease the reduction potential, depending on their orientations relative to the redox center, The effects of complex formation, proton titration, and ionic strength are also discussed.