Green DPSS laser for nanoparticles characterization by SERS and rRaman spectroscopy of heme proteins

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We request a narrow linewidth Diode-Pumped Solid State (DPSS) laser operating at 532 nm that will be used to obtain resonance Raman (rRaman) spectra of heme proteins (as described in current M. Couture Discovery Grant) and Surface-Enhanced Raman Spectra (SERS) of nanomaterial synthesized in order to build a flow-cell that will be used as a model of the vascular system (as described in B. Mutus Discovery Grant). M. Couture has a strong scientific program aimed at the detailed characterization of the catalytic mechanism of nitric oxide synthases (NOSs), which are the enzymes that synthesize the signalling molecule nitric oxide. For this, her laboratory is equiped with a high resolution Raman system that is used to get rRaman spectra of NOSs and other heme proteins. The current set-up uses a laser emitting in the blue-region of the absorption spectrum to get rRaman spectra of stable samples as well as those of short-lived kinetic intermediates using a custom-build continuous flow mixer. The requested green DPSS laser would allow Q-band (green) excitation of the heme active site to specifically enhance non-totally symmetric modes of the heme. This would complement our current studies with blue-excitation and be extremely important to assign the modes of the heme macrocycle and of the heme substituents. Once assigned, specific heme modes could reveal how the electron density on the cysteine sulfur of NOSs is shared with the heme, how it responds to substrate and cofactor binding and how this relates to the catalytic process in NOSs.