far UV have demonstrated unusual CD spectra due
The aromatic and sulfur-containing side chains Trp, to aromatic side chains (13)(14)(15)(16)(17)(18)(19)(20)(21)(22). In most cases, the Tyr, Phe, Cys, and Met contribute to the CD spectra of tryptophan and tyrosine sidechains are found to be the peptides and proteins in the amide region, interfering sources of interference. Some workers have carried out with the analysis for secondary structure. We propose theoretical studies and calculated the rotational a method to correct the CD spectra of peptides understrength resulting from the interaction of these side going the helix-coil transition for contributions due chains with the electronic transitions of the peptide to absorbing side chains using singular value decombond (10,(23)(24)(25)(26).
position. The method uses the common basis vectors
The contribution from amino acid side chains beobtained from an analysis of the CD spectra of related comes a problem when a CD spectrum is interpreted peptides without the aromatic and sulfur-containing and analyzed for secondary structure. Several groups amino acids. The common basis vectors are fitted to a have investigated the CD spectra of peptides and proportion of the CD spectrum of the peptide being corteins containing different types and numbers of arorected, in the range that is unaffected by its sidematic side chains (27-29). The CD spectra for proteins chain contributions. Then the resulting coefficients or peptides of similar secondary structure but with diffrom the fitting are used along with the common basis ferent numbers of aromatic side chains are found to vectors to regenerate the entire corrected specbe different in the far UV. The estimate of structural trum. The method is illustrated for the CD spectra of content of these proteins by several algorithms yields the peptide sequence acetyl-Y-VAXAK-VAXAK-VAXAK-
information that is unreliable (29). The error in strucamide, where X is substituted with the 20 naturally tural estimates exists for both methods using a waveoccurring amino acids. This peptide model adopts a length range and those that rely on a single waverandom-coil conformation in 2 mM sodium phosphate buffer, pH 5.5, and becomes an a helix in methanol/ length. Recently, the contribution from aromatic side buffer solutions. The difference between the original chains was investigated in a series of short peptides and corrected spectra shows the contribution from the (27). The experiments showed that the contribution aromatic and sulfur-containing side chains. ᭧ 1997 from an aromatic tag located at the peptide terminal