Improved Photobactericidal Activity of Ultraviolet-A Light in Combination with Isomerizable p-Coumaric Acid Derivatives.

In order to improve the photobactericidal activity of ultraviolet-A (UV-A) mediated by reactive oxygen species (ROS), the present study focused on trans-coumaric acid (trans-CA), which is isomerized by UV-A. Generation of ROS was expected during the isomerization of trans-CA. Trans-CA derivatives, in which the carboxyl group was modified with a methyl, n-butyl or phenyl group, thereby changing the interaction with the cellular membrane by quenching the anionic properties of the carboxyl group and changing the UV adsorption properties, were used. The photobactericidal activities of trans-CA derivatives were evaluated by using UV-A light (wavelength 350 to 385 nm). The number of surviving Escherichia coli NBRC12713 was determined by colony-forming assay. Derivative 4c, which was esterified with a phenyl group, reduced survival by more than 5.0-log at a dose of 7.4 J/cm(2) and by 3.2-log at a dose of 4.9 J/cm(2). This synergistic activity may have been caused by the absorption of photon energy from UV-A, which is attributable to the UV spectrum of 4c. The photobactericidal activity was comparable to that of riboflavin, a known photo-activated agent. Isomerized molecules serve as a promising lead for improving the photobactericidal activity of UV-A by activating molecule-mediated ROS generation.

Recordings from cultured newt olfactory receptor cells.

Freshly dissociated olfactory receptor cells (ORCs) are commonly used in electrophysiological research investigations of the physicochemical mechanisms of olfactory signal transduction. Because the morphology of cultured cells clearly becomes worse over time, the ORCs are examined traditionally within several days after dissociation. However, there has been a major concern that cells are affected soon after dissociation. To gain a better understanding of the reliability of data obtained from solitary cells, we obtained electrical data during the lifetime of single ORCs dissociated from the newt. The time course for the deterioration could be revealed by monitoring the membrane properties during culture. Although the number of living cells that were identified by trypan blue extrusion declined day by day, the remaining cells retained morphology and their fundamental electrical features until day 19. In some cells, the cilia and dendrite were observed until day 21, and the bipolar morphology until day 31. The fundamental features of cell excitation were maintained during culture without showing remarkable changes when they retained morphological features. The results suggest that electrical properties of cells are almost unchanged within several days. Furthermore, the dissociated newt ORCs can be used for several weeks that are almost comparable to the intrinsic lifetime of the ORCs in vivo.