UV Raman Determination of the Environment and Solvent Exposure of Tyr and Trp Residues
نویسندگان
چکیده
We characterized the dependence of the 229 nm Raman cross sections of tyr and trp on solvent exposure in native horse and tuna cytochrome c and in horse and sperm whale myoglobin. Tyr and trp residues with larger solvent accessible surface areas have smaller 229 nm excited tyr and trp Raman cross sections. We observe that in water-propanol solvent mixtures the 229 nm excited tyr and trp Raman cross sections increase with decreasing water composition due to red shifts of the ∼220 nm tyr and trp absorption bands. The tyr and trp protein Raman cross section changes result from absorption red shifts for environments with increasing hydrogen bond donor basicity, decreasing hydrogen bond acceptor acidity, and increasing polarity. We empirically correlate changes in Raman cross sections with the tyr and trp residue solvent accessibility. The Raman cross sections of tyr and trp residues can now be quantitatively utilized to probe local protein environments.
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