Partial least square analysis of lysozyme near-infrared spectra

Proteins possess strong absorption features in the combination range (5000- 4000 cm(-1)) of the near infrared (NIR) spectrum. These features can be use d for quantitative analysis. Partial least squares (PLS) regression was use d to analyze NIR spectra of lysozyme with the leave-one-out, full cross-val idation method. A strategy for spectral range optimization with cross-valid ation PLS calibration was presented. A five-factor PLS model based on the s pectral range between 4720 and 4540 cm(-1) provided the best calibration mo del for lysozyme in aqueous solutions. For 47 samples ranging from 0.01 to 10 mg/mL, the root mean square error of prediction was 0.076 mg/mL. This re sult was compared with values reported in the literature for protein measur ements by NIR absorption spectroscopy in human serum and animal cell cultur e supernatants.