Protein structure in KBr pellets by infrared spectroscopy.

In this work we analyzed the secondary structure of 13 globular proteins in KBr pellet through Fourier transform infrared spectroscopy (FTIR). The quantification was based in singular value decomposition (SVD) theory, a pattern recognition method. The results show better correlation for alpha helix (0.90) and beta sheet (0.84) in amide I band, similar to the results obtained for proteins in solution. These results show that the protein secondary structure is conserved in solid state, in opposition to the results observed by FTIR using resolution enhancement techniques. The SVD analysis also show that in KBr pellets the protein secondary structures have absorbances in different wavenumbers when compared to those in solution. In this way, the use of KBr pellet and the pattern recognition method can be an ideal method to analyze protein secondary structure by FTIR.