Resonance Raman studies of blue copper proteins: effect of temperature and isotopic substitutions. Structural and thermodynamic implications

Journal Article · Tue Jan 01 04:00:00 EST 1985 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00306a025· OSTI ID:6712914

Blair, D F; Campbell, G W; Schoonover, J R; Chan, S I; Gray, H B; Malmstrom, B G; Pecht, I; Swanson, B I; Woodruff, W H; Cho, W K; English, A M

Resonance Raman spectra of the single-copper blue proteins azurin plastocyanin and stellacyanin and the multicopper oxidases laccase ascorbate oxidase and ceruloplasmin are reported. Cryoresonance Raman observations (10-77 K) are reported for selected azurins, stellacyanin, the plastocyanins, and the laccases. Isotope studies employing /sup 63/Cu//sup 65/Cu and H/D substitution are reported for selected azurins and stellacyanin, allowing identification of modes having significant copper-ligand (Cu-L) stretch and internal ligand deformation character. Principal conclusions include the following. The only Cu-L stretching mode near 400 cm/sup -1/ is the Cu-S(Cys) stretch, and the remainder of the elementary motions near this frequency are internal ligand deformations. All the observed modes near 400 cm/sup -1/ are highly mixed, and most derive their intensity from their fractional Cu-S(Cys) stretching character. The Cu-N(His) stretching motions are best identified with the ubiquitous peak(s) near 270 cm/sup -1/, although in azurin these modes have contributions from other coordinates. Internal histidine and cysteine motions contribute to the features near 400 cm/sup -1/. This is consistent with a single resonant electronic chromophore and extremely facile vibrational dephasing or other damping processes in the electronically excited state. Temperature effects upon the spectra suggest a significant temperature-dependent structure change at the plastocyanin active site, and a more subtle one in azurin. It is shown that the Cu-S(Cys) stretching frequency is closely correlated to the electron-transfer exothermicity for several proteins, thereby indicating the reduction potential can be fine tuned by the effects of polypeptide backbone structure on the copper-sulfur bond distance and the copper-ligand field. 41 references.

• Research Organization: Los Alamos National Labs., NM
• OSTI ID: 6712914
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 107; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
BOND ANGLE
CHEMICAL BONDS
COPPER COMPOUNDS
DATA
EXPERIMENTAL DATA
FREQUENCY DEPENDENCE
INFORMATION
MOLECULAR STRUCTURE
NUMERICAL DATA
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
PROTEINS
RAMAN SPECTRA
SPECTRA
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS