The resonance Raman spectra of the cyanide adducts of cytochrome P-450 camphor in the substrate-free, camphor-bound, and adamantanone-bound forms are reported. Careful analyses of the difference patterns obtained by subtraction of various pairs of spectra of four CN- isotopomers provide convincing evidence for the presence of two structural conformers : one "essentially Linear" and the other bent. Both conformers persist for the substrate-bound derivatives. The linear conformer exhibits the nu(Fe-C) stretching mode at 413 cm(-1) and the delta(FeCN) bending mode at 387 cm(-1) for the substrate-free derivative. The corresponding values for the camphor-bound form are 416 and 392 cm(-1), while for the adamantanone derivative these occur at 423 and 387 cm(-1). The bent conformer exhibits a set of vibrational parameters which is characterized by a "zigzag" isotope shift pattern for both the lower frequency and the higher frequency mode. For the substrate-free form, the vibrational modes of both conformers are shown to be sensitive to (H2O)-H-1/(H2O)-H-2 exchange, confirming that they are both hydrogen bonded. While in the case of the linear conformer the H-bond donor is most likely the active site water cluster, the (presumably off-axis) donor for the bent conformer may be either another region of the water cluster or the threonine-252 (or aspartate-251) residue which may be in a position to interact with the polar CN- ligand. : one "essentially Linear" and the other bent. Both conformers persist for the substrate-bound derivatives. The linear conformer exhibits the nu(Fe-C) stretching mode at 413 cm(-1) and the delta(FeCN) bending mode at 387 cm(-1) for the substrate-free derivative. The corresponding values for the camphor-bound form are 416 and 392 cm(-1), while for the adamantanone derivative these occur at 423 and 387 cm(-1). The bent conformer exhibits a set of vibrational parameters which is characterized by a "zigzag" isotope shift pattern for both the lower frequency and the higher frequency mode. For the substrate-free form, the vibrational modes of both conformers are shown to be sensitive to (H2O)-H-1/(H2O)-H-2 exchange, confirming that they are both hydrogen bonded. While in the case of the linear conformer the H-bond donor is most likely the active site water cluster, the (presumably off-axis) donor for the bent conformer may be either another region of the water cluster or the threonine-252 (or aspartate-251) residue which may be in a position to interact with the polar CN- ligand.