Quantitative determination of low density lipoprotein oxidation by FTIR and chemometric analysis.
This study was conducted to develop a quantitative FTIR spectroscopy method to measure LDL lipid oxidation products and determine the effect of oxidation on LDL lipid and protein. In vitro LDL oxidation at 37 degrees C for 1 h produced a range of conjugated diene (CD) (0.14-0.26 mM/mg protein) and carbonyl contents (0.9-3.8 microg/g protein) that were used to produce calibration sets. Spectra were collected from the calibration set and partial least squares regression was used to develop calibration models from spectral regions 4000-650, 3750-3000, 1720-1500, and 1180-935 cm(-1) to predict CD and carbonyl contents. The optimal models were selected based on their standard error of prediction (SEP), and the selected models were performance-tested with an additional set of LDL spectra. The best models for CD prediction were derived from spectral regions 4000-650 and 1180-935 cm(-1) with the lowest SEP of 0.013 and 0.013 mM/mg protein, respectively. The peaks at 1745 (cholesterol and TAG ester C=O stretch), 1710 (carbonyl C-O stretch), and 1621 cm(-1) (peptide C=O stretch) positively correlated with LDL oxidation. FTIR and chemometrics revealed protein conformational changes during LDL oxidation and provided a simple technique that has potential for rapidly observing structural changes in human LDL during oxidation and for measuring primary and secondary oxidation products.
Lam
Henry S
HS
Department of Food Science, University of Arkansas, Fayetteville, Arkansas 72704, USA.
Proctor
Andrew
A
Nyalala
John
J
Morris
Manford D
MD
Smith
W Grady
WG
D006801:Humans; D008077:Lipoproteins, LDL / Q000737:chemistry* / Q000378:metabolism; D008297:Male; D010084:Oxidation-Reduction; D011487:Protein Conformation; D012044:Regression Analysis; D015203:Reproducibility of Results; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013223:Statistics as Topic
D008077:Lipoproteins, LDL