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Michele Vittadello

Michele Vittadello

The City University of New York, USA

Title: Cytochrome c oxidase oxygen reduction induced by Cytochrome c onto nickel coordination surface based on graphene oxide in suspension

Biography

Biography: Michele Vittadello

Abstract

In vitro investigations on isolated components of the mitochondrial electron transport chain are expected to shed new light on the plethora of bioenergetic functions carried out by mitochondria, affecting the performance of living organisms. This study is focused on assessing the biocompatibility of graphene oxide (GO) derivatives with His-tagged cytochrome c oxidase (CcO), expressed and purified from Rhodobacter sphaeroides using the Gibson assembly method. As prepared GO was enriched with carboxylic acid groups yielding carboxylated GO (CGO). CGO was functionalized with nitrilotriacetic acid (NTA) yielding CGO-NiNTA, in the presence of Ni2+ ions. We investigated the reaction of horse-heart cytochrome c (Cyt c) with free CcO and CGO-NiNTA-CcO coordination complexes in suspension. Kinetic studies by UV-Visible absorption spectroscopy confirmed that free CcO oxidizes Cyt c and provided a similar indication for immobilized CcO. However, oxygen-consumption measurements using a Clark-type electrode suggested that CGO-based supports are capable of oxygen reduction reaction (ORR), especially in the presence of Ni2+ coordination centers. The ORR caused by immobilized CcO could be clearly distinguished from that of CGO-NiNTA in the presence of Cyt c and dithiothreitol (DTT) as a sacrificial reducing agent. The results indicate that while the protein content is about 3% by mass with respect to the support, the contribution to the oxygen consumption activity ranges from 39.3% to 71.0%, depending on the concentration of DTT. This finding indicates that the support stabilizes the free enzyme which, while capable of Cyt c oxidation, is unable to carry out oxygen consumption in solution. The turnover rate was as high as 599 O2 molecules per CcO unit per second.