A key problem in biological electron transfer is the independent measurement of the parameters upon which the rate constant for electron transfer depends. In this paper, we report evidence that quantitative resonance Raman spectroscopy may be such an independent probe of the electronic coupling parameter in proteins. The resonance Raman cross-sections of four species of azurin have been measured throughout the ca. 600-nm absorption band. The total resonance Raman intensity, as quantified by the cross-sections, is very similar for the four azurins in the 200-700 cm(-1) region. However, the resonance Raman intensity is distributed differentially among the vibrational modes, sometimes also accompanied by small frequency shirts. Correlations are attempted between this re-distribution of resonance Raman intensity and Cu-S bond length, Cu out-of-plane distance, backbone structure, and protein environment. Of these four parameters, the only significant correlation exists with the protein environment. A detailed analysis of the residues within 10 Angstrom of the copper site demonstrates a strong, anisotropic coupling between the copper site and Trp48, a residue previously implicated in intramolecular electron transfer pathways of azurin.