Photocatalytic inactivation of influenza virus by titanium dioxide thin film

Titanium dioxide (TiO(2)) under ultraviolet (UV) light produces a strong oxidative effect and may therefore be used as a photocatalytic disinfectant. Although many studies on the photocatalytic inactivation of bacteria have been reported, few studies have addressed virus inactivation. In the present study, we demonstrated the inactivation of influenza virus through TiO(2) photocatalysis using TiO(2) nanoparticles immobilized on a glass plate. The influences of the UV intensity, UV irradiation time and bovine serum albumin (BSA) concentration in the viral suspensions on the inactivation kinetics were investigated. Additionally, we also determined whether the International Organization for Standardization (ISO) methodology for the evaluation of antibacterial activity of TiO(2) photocatalysis could be applied to the evaluation of antiviral activity. The viral titers were dramatically reduced by the photocatalytic reaction. Even with a low intensity of UV-A (0.01 mW cm(-2)), a viral reduction of approximately 4-log(10) was observed within a short irradiation time. The viral inactivation kinetics were associated with the exposure time, the UV intensity and the BSA concentration in virus suspensions. These results show that TiO(2) photocatalysis could be used to inactivate the influenza virus. Furthermore, a minor modification of the ISO test method for anti-bacterial effects of TiO(2) photocatalysis could be useful for the evaluation of antiviral activity.     

Kinetics of the inactivation of the protein-lipid complex, firefly luciferase, by sodium deoxycholate and its reactivation by phosphatidylcholine

Firefly luciferase has been shown to be a protein-lipid complex. Phospholipids and neutral lipids bound to luciferase have been identified. Sodium deoxycholate rapidly inactivated the enzyme, but an excess of phosphatidylcholine recovered luciferase activity. From the kinetics of inactivation and reactivation, a mechanism for interaction of the enzyme with detergents and phospholipids has been proposed. The substrates ATP and Mg2+ stabilized luciferase during delipidation.     

Comparison of two-pulse sodium inactivation with reactivation in Myxicola giant axons.

Values for the time constant of reactivation of the sodium conductance following depolarization sufficient to completely inactivate GNa have been compared over a 15 mV range of membrane potential with the time constants of inactivation during a depolarization prepulse. Over this range the reactivation time constants were consistently 30-50% larger than the inactivation time constants determined simultaneously at the same potential in the same axon. The data suggests that inactivation and reactivation do not occur by identical mechanisms, and therefore implies that there are at least three kinds of experimental procedures necessary to fully characterize the sodium inactivation process in any particular system.     

Estimation by radiation inactivation of the size of functional units governing Sendai and influenza virus fusion

The target sizes associated with fusion and hemolysis carried out by Sendai virus envelope glycoproteins were determined by radiation inactivation analysis. The target size for influenza virus mediated fusion with erythrocyte ghosts at pH 5.0 was also determined for comparison; a value of 57 +/- 15 kDa was found, indistinguishable from that reported previously for influenza-mediated fusion of cardiolipin liposomes [Gibson, S., Jung, C. Y., Takahashi, M., & Lenard, J. (1986) Biochemistry 25, 6264-6268]. Sendai-mediated fusion with erythrocyte ghosts at pH 7.0 was likewise inactivated exponentially with increasing radiation dose, yielding a target size of 60 +/- 6 kDa, a value consistent with the molecular weight of a single F-protein molecule. The inactivation curve for Sendai-mediated fusion with cardiolipin liposomes at pH 7.0, however, was more complex. Assuming a "multiple target-single hit" model, the target consisted of 2-3 units of ca. 60 kDa each. A similar target was seen if the liposomes contained 10% gangliosides or if the reaction was measured at pH 5.0, suggesting that fusion occurred by the same mechanism at high and low pH. A target size of 261 +/- 48 kDa was found for Sendai-induced hemolysis, in contrast with influenza, which had a more complex target size for this activity (Gibson et al., 1986). Sendai virus fusion thus occurs by different mechanisms depending upon the nature of the target membrane, since it is mediated by different functional units. Hemolysis is mediated by a functional unit different from that associated with erythrocyte ghost fusion or with cardiolipin liposome fusion.