Brown Bag Lunch | Raju Badireddy

Title: "Assessment of Interactions of UV-sensitized Hydrophilic Fullerene Nanoparticles and Singlet Oxygen with Bacteriophages: Role of Association and Oxidation"

Date: 01/09/2012 | 12:00 pm - 1:00 pm
Location: 1441 CIEMAS/Fitzpatrick Center

Raju Badireddy, Ph.D.
Postdoctoral Associate
Department of Civil and Environmental Engineering

Abstract: The effects of ultraviolet (UV)-A sensitized singlet oxygen (1O2) and differential affinities of fullerenes, (namely, aqueous (aqu)-nC60, C60(OH)6, C60(OH)24, and C60(NH2)6) towards MS2 bacteriophage were investigated in this study. MS2 were inactivated by UVA alone at a rate 0.034 min-1, but in the presence of fullerenes (5 mg-carbon/mL) enhanced inactivation rates ranging from 1.74- to 11.4-fold were observed. 1O2 generation and MS2 inactivation followed first-order kinetics but not the inactivation versus 1O2 dose (concentration x time (CT), mg-min L-1) relationship described by the Chick-Watson model. Dissimilarities in 1O2 dose-dependent inactivation rates were probably due to differences in electrostatic interactions between the fullerenes and MS2, which consequently altered MS2 exposure to 1O2 dose. A novel dark-field based hyperspectral imagery analysis has been utilized for the first time to visualize the differences in affinities between fullerenes and MS2 followed by TEM imagery, which showed the presence of damaged MS2 due to 1O2. ATR-FTIR analysis revealed disordering in oxidized MS2 protein secondary structures and increase in protein carbonyl content confirmed by OxyBlot assay. Furthermore, FTIR spectra showed an increase in “exposed” disordered-RNA in the samples supporting that 1O2 ruptured the capsid, which resulted in damaged capsid or probably dissipated the torsional energy of the capsid. Thus, the MS2 inactivation mechanism appears to be governed by the extent of electrostatic interactions between MS2 and fullerenes and protein oxidation by UV-sensitized 1O2, both of these are dependent on the type of hydrophilic groups present on the fullerenes.