Far-infrared (FIR) spectroscopy in the spectral region of 50–450 cm<sup>–1</sup> was used to study a series of protein higher-order structures constructed using β-lactoglobulin and polyomavirus capsid protein VP1. There were marked differences in the spectra for β-lactoglobulin monomer and dimer and between untreated β-lactoglobulin and heat-induced gels formed at neutral pH. Untreated β-lactoglobulin and heat-induced gels formed at acidic pH exhibited little difference in their spectra. Assembly of the quaternary structure of polyomavirus virus-like particles also caused large changes in the FIR spectra. These findings suggest that FIR spectroscopy may prove useful in studying some protein quaternary and higher-order structures. There was evidence of detection of β-lactoglobulin dimerization, intermolecular disulfide bonding in heat-induced neutral gels, and polyomavirus virus-like particle assembly but no evidence that FIR could detect β-lactoglobulin fibrils with their polymeric structure and hydrogen-bonded intermolecular β-pleated sheeting. Index Headings: Terahertz; Beta-lactoglobulin; β-lactoglobulin; Amyloid; Fibril; Polyomavirus; Virus-like particle; Quaternary structure; Vibrational spectrometry.
Vol. 6, Iss. 1 Virtual Journal for Biomedical Optics
Robert J. Falconer, Hidayatul A. Zakaria, Yuan Y. Fan, Andrew P. Bradley, and Anton P.J. Middelberg, "Far-Infrared Spectroscopy of Protein Higher-Order Structures," Appl. Spectrosc. 64, 1259-1264 (2010)