Abstract
Background: The aim of this study was to investigate the potential of infrared (IR) spectroscopy as a fast and reagent-free adjunct tool in the diagnosis and screening of β-thalassemia.
Methods: Blood was obtained from 56 patients with β-thalassemia major, 1 patient with hemoglobin H disease, and 35 age-matched controls. Hemolysates of blood samples were centrifuged to remove stroma. IR absorption spectra were recorded for duplicate films dried from 5 μL of hemolysate. Differentiation between the two groups of hemoglobin spectra was by two statistical methods: an unsupervised cluster analysis and a supervised linear discriminant analysis (LDA).
Results: The IR spectra revealed changes in the secondary structure of hemoglobin from β-thalassemia patients compared with that from controls, in particular, a decreased α-helix content, an increased content of parallel and antiparallel β-sheets, and changes in the tyrosine ring absorption band. The hemoglobin from β-thalassemia patients also showed an increase in the intensity of the IR bands from the cysteine −SH groups. The unsupervised cluster analysis, statistically separating spectra into different groups according to subtle IR spectral differences, allowed separation of control hemoglobin from β-thalassemia hemoglobin spectra, based mainly on differences in protein secondary structure. The supervised LDA method provided 100% classification accuracy for the training set and 98% accuracy for the validation set in partitioning control and β-thalassemia samples.
Conclusion: IR spectroscopy holds promise in the clinical diagnosis and screening of β-thalassemia.
Characterization of protein secondary structure from NMR chemical shifts
