Related Experiment Video
Updated: Apr 21, 2026

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
Published on: December 16, 2013
Comparability of higher order structure in proteins: chemometric analysis of second-derivative amide I Fourier
Gregory Stockdale1, Brian M Murphy, Jennifer D'Antonio
1Department of Statistical Sciences, Projects Clinical Platform, R&D, GlaxoSmithKline, King of Prussia, Pennsylvania, 19406.
Abstract:
Comparing higher order structure (HOS) in therapeutic proteins is a significant challenge. Previously, we showed that changes in solution conditions produced detectable changes in the second-derivative amide I Fourier transform infrared (FTIR) spectra for a variety of model proteins. Those comparisons utilized vector-based approaches, such as spectral overlap and spectral correlation coefficients to quantify differences between spectra. In this study, chemometric analyses of the same data were performed, to classify samples into different groups based on the solution conditions received. The solution conditions were composed of various combinations of temperature, pH, and salt types. At first, principal component analysis (PCA) was used to visually demonstrate that FTIR spectra respond to changes in solution conditions, which, presumably indicates variations in HOS. This observed when samples from the same solution condition form clusters within a PCA score plot. The second approach, called soft independent modeling of class analogy (SIMCA), was conducted to account for the within-class experimental error for the lysozyme spectra. The DModX values, indicative of the distance of each spectra to their respective class models, was found to be a more sensitive quantitative indicator of changes in HOS, when compared with the modified area of overlap algorithm. The SIMCA approach provides a metric to determine whether new observations do, or do not belong to a particular class or group. Thus, SIMCA is the recommended approach when multiple samples from each condition are available.
Related Concept Videos
¹H NMR: Interpreting Distorted and Overlapping Signals
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations
Spectroscopy of Carboxylic Acid Derivatives
NMR Spectroscopy Of Amines
IR Frequency Region: X–H Stretching
IR Frequency Region: Fingerprint Region

