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.
Tel.: +386 01
47 60 200, Fax: +386 01 42 59 244, e-mail: joze.grdadolnik@ki.si
Abstract
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.