title: Statistical comparison of Fourier transform infrared spectra.
abstract: Spectroscopic assessment of whether a biological sample has changed as a result of processing or degradation is generally carried out by qualitative comparison of spectra, without statistical analysis, resulting in a subjective evaluation of sample stability. Here, we present a formalism for quantitative statistical comparison of signal-averaged Fourier transform infrared spectra, commonly used to assess molecular properties of biological samples. Expressions are derived permitting the comparison of 1. single beam spectra; 2. transmittance spectra obtained by calculating the ratio of single beam spectra of a sample and background; and 3. absorbance spectra derived from transmittance spectra. An application of these results to the degradation of cartilage is presented. Two absorbance spectra of a cartilage sample taken in succession are found to be statistically identical with respect to the ratio of the amplitude of the amide I band to the amplitude of the amide II band. However, a spectrum of the same sample acquired after a 24-h degradation period, while similar to the spectrum of the fresh sample, is found to have an altered ratio of these spectral band amplitudes, consistent with degradation of the cartilage matrix.
authors.affiliation: National Institutes of Health, National Institute on Aging, Nuclear Magnetic Resonance Unit, Baltimore, Maryland 21224, USA.
authors.forename: Richard G
authors.initials: RG
authors.lastname: Spencer
authors.forename: Ericka F
authors.initials: EF
authors.lastname: Calton
authors.forename: Nancy Pleshko
authors.initials: NP
authors.lastname: Camacho
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D008954:Models, Biological; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*