Surface Enhanced Raman Spectroscopy (SERS) has demonstrated significant benefit in the identification of biological molecules. In this paper we have examined how to identify and differentiate the 150 kDa protein myeloperoxidase (MPO) from its corresponding antibody (Ab) and their immunocomplex through the use of SERS. The SERS signal of these biological molecules was enabled by 40 nm gold nanoparticles. The SERS spectra for both MPO and the Ab (an IgG molecule) demonstrated results consistent with previous published work on the Raman spectra of MPO and IgG antibodies. The immunocomplex SERS spectra showed peak shifts and intensity variations that could be attributed to conformational changes that occur during immunocomplex formation. Several key spectral areas have been identified which correspond to specific amino acids being shielded from undergoing resonance while new amino acid residues are made visible in the SERS spectrum of the immunocomplex and could be a result of conformational binding. These results indicate that SERS can be used to identify binding events and distinguish an immunocomplex from its individual components.
We demonstrate the generation of 211-nm radiation using sum frequency mixing of the second and third harmonics of a cw mode-locked Nd: YLF laser operating at 76 MHz as an excitation source for resonance Raman spectroscopy. Owing to the relatively low peak power (∼4 W) but high average power (∼8 mW), we obtain good-quality spectra with relatively short collection times. In order to demonstrate the utility of this source, we have obtained the Raman spectra of several biological molecules and an inorganic molecule, ruthenium trisbipyridine, using 211-nm excitation.
SERS study on myeloperoxidase and its immunocomplex: Identification of binding interactions
