RECENT DEVELOPMENTS IN RAMAN OPTICAL-ACTIVITY OF BIOPOLYMERS

Recent advances in Raman optical activity (ROA) instrumentation are ou tlined which have enhanced significantly the quality of vibrational RO A spectra of biopolymers in aqueous solution. Peptides, proteins, carb ohydrates, glycoproteins, and nucleic acids now provide excellent ROA spectra which contain detailed information about solution structure. R OA spectra can be measured just as easily in D2O as in H2O solution, a nd, as illustrated for bovine serum albumin and concanavalin A, a comp arison of the two can be highly informative. In addition to signatures of extended secondary structure, protein ROA spectra also contain sig natures related to loops and turns which are valuable for studying ter tiary structure and dynamics, exemplified here by a comparison of the ROA spectra of reduced lysozyme and unordered poly-l-lysine, by the RO A spectra of acid molten globule cu-lactalbumin at different temperatu res, which reveal a native-like tertiary fold, and by changes in the R OA spectrum of native lysozyme on binding to a saccharide inhibitor. C arbohydrate ROA spectra contain signatures of all the central features of their stereochemistry and, as shown by a comparison of laminaribio se with laminarin, can also probe extended secondary structure in poly saccharides. Results on a glycoprotein, orosomucoid, suggest that ROA can provide information about both the protein and the carbohydrate co mponents. Preliminary results on nucleic acids are outlined with the R OA spectra of Poly(rA). Poly(rU) and Poly(rI). Poly(rC) shown as examp les.