[SCAN] Raman spectroscopy - a powerful tool for studying metalloproteins and metal-oxide materials for biosensor applications

Scan Seminar

Title: Raman spectroscopy - a powerful tool for studying metalloproteins and metal-oxide materials for biosensor applications

Speaker: Célia Silveira

From: Raman Spectroscopy of Metalloproteins Lab, ITQB

Abstract:

Raman spectroscopy allows probing the vibrational levels of molecules, thereby providing important information on molecular structures. Herein we show the application of this spectroscopic technique in the study of both inorganic (tungsten trioxide nanoparticles) and organic systems (metalloproteins).

Cytochrome cd1 nitrite reductases (cd1NiRs) catalyze the one electron reduction of nitrite to nitric oxide in denitrifying microorganisms. These homodimeric proteins contain in each subunit one heme c, the electron transfer site, and one heme d1, which is exclusive to this class of enzymes and constitutes the active site where the reduction of nitrite takes place. We have used resonance Raman (RR) spectroscopy to get insights into the structural features of Marinobacter hydrocarbonoclasticus cd1NiR, as well as on the redox properties of the enzyme. Surface enhanced RR (SERR) spectroelectrochemistry was employed to characterize the enzyme adsorbed on biocompatible metal electrodes and evaluate the impact of the immobilization on its structural and thermodynamic properties. The obtained results shed light on the potential utilization of cd1NiRs in bioelectrochemical devices for biotechnological applications.

Nanostructured metal oxides are currently receiving a lot of attention because of their interesting electrical, magnetic, optical and mechanical properties. Tungsten trioxides (WO3), for example, display distinctive physical and chemical properties, such as high conductivity, sensitivity, selectivity and biocompatibility, that make them very suitable for the construction of (bio)sensing electrodes. Herein we have used Raman spectroscopy to characterize the structural features of different WO3 nanoparticle films used as promoters of the electron transfer between heme proteins (cytochrome c and the ammonia forming cytochrome c nitrite reductase) and ITO electrodes. The WO3 films were analyzed in the absence of the proteins and after they were casted; simultaneously RR was used to evaluate the structural integrity of cytochrome c nitrite reductase, after immobilization on the tungsten films.