SOLVENT PERTURBATION STUDIES OF HEME PROTEINS AND OTHER COLORED PROTEINS .2. ON ENVIRONMENT AND LOCATION OF TRYPTOPHYL RESIDUES IN HEMOGLOBIN

The location and environment of the tryptophyl residues in hemoglobin have been investigated by the solvent perturbation technique of difference spectroscopy. The perturbation parameters obtained on horse hemoglobin, by use of six perturbants, suggest a substantial degree of burial of the six tryptophyl residues in the native protein. While it was not possible to analyze the solution data in terms of exposed, partly buried, and buried groups, comparison of the hemoglobin data with the literature data of ribonuclease and lysozyme, suggests that the sum of fractional exposures and perturbations due to six partly buried groups or perhaps four partly buried and two buried or largely buried chromophores would be most consistent with the observed hemoglobin perturbations. The perturbation parameters obtained on five additional mammalian hemoglobins with 20% ethylene glycol as perturbant suggest that the tryptophyl residues in the mammalian hemoglobins in solution are probably located in very similar environments. © 1969.