SATURATION EFFECTS IN FTIR SPECTROSCOPY: INTENSITY OF AMIDE I AND AMIDE II BANDS IN PROTEIN SPECTRA
National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia.
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In the present article the dependence between the film thickness of the BSA protein and the intensity and structure of the Amide I and II bands are presented. Protein films thicker than 4 mm are shown to be unsuitable for structural investigation using transmission infrared spectroscopy since the signal for Amide I is saturated. Saturation of the Amide I band in the protein film spectrum causes complete disruption in the structure of the Amide I band. Furthermore, the structure of the nearby Amide II band is also perturbed. Hence, in order to avoid such band distortions the protein film thickness should be below 4 mm, which corresponds to the absorption value of the strongest band in the spectrum below 1.2 absorption units.