[Photosensitizing properties of 3,3'-diethylthiacarbocyanine in biological media].

The objective of the study is elucidation of perspectives of 3,3'-diathylcarbocyaine application as a photosensitizer for curing viral infections by photodynamic therapy. Lipid-containing bacteriophage PM-2 of Pseudoalteromonas espejiana was used as a model. The testing was carried out at a special installation modeling photodynamic exposure conditions towards a non-fractionated phage lysate. 3,3'-DECC demonstrated a rapid photo-bleaching when added tothe phage lysate but not to water. The initial rate of PM-2 phage photoinactivation was proportional to the square concentration of the dye in the range of 0.5-9 µmol/L. This confirms a hypothesis that the dimer is the principal photochemically active form of the dye. An improved ability to form dimers was found in the dye in the phage lysate (10-folds better than in the water). The dye formed a stable adduct with the bacteriophage material. This adduct had an extinction maximum at λ(max) = 594 nm and demonstrated the properties of a polymer (sedimentation under a low-speed centrifugation).

Purification and protein composition of PM2, the first lipid-containing bacterial virus to be isolated.

The marine, icosahedral bacteriophage PM2 was isolated in the late 1960s. It was the first phage for which lipids were firmly demonstrated to be part of the virion structure and it has been classified as the type organism of the Corticoviridae family. The host, Pseudoalteromonas espejiana BAL-31, belongs to a common group of marine bacteria. We developed a purification method producing virions with specific infectivity approximately as high as that of the lipid-containing phages PRD1 and φ6. The sensitivity of the virus to normally used purification media such as those containing sucrose is demonstrated. We also present an alternative host, a pseudoalteromonad, that allows enhanced purification of the virus under reduced salt conditions. We show, using N-terminal amino acid sequencing and comparison with the genomic sequence, that there are at least eight structural proteins in the infectious virus.

Modulation of metal-induced genotoxicity by Maillard reaction products isolated from coffee.

PM2 bacteriophage DNA was exposed to non-dialysable Maillard reaction products (MRPs) isolated from brewed (Br), boiled (Bo) and instant (I) coffee brew extracts in a Fe2+ catalysed Fenton reaction at four pH conditions (i.e. 7.5, 4.0, 3.2, 2.6). MRPs were incubated with DNA either directly with Fe2+, or following a short preincubation period conducted with Fe2+ in an atmosphere of oxygen or argon. Damage to supercoiled DNA resulting in strand scissions as characterized by both nicked circular and linear forms were found to occur either with coffee MRPs or Fe2+ alone, in a dose-dependent manner at all pH conditions tested. At low MRP concentrations, damage to DNA with respect to Fe2+ was lowered only when MRPs were preincubated with Fe2+ in argon or oxygen before incubating with DNA. The addition of MRPs and Fe2+ to DNA without preincubation, had no effects in protecting DNA damage. This finding showed that a preincubation step is necessary for MRPs to chelate Fe2+ in order to mitigate the Fenton reaction. In contrast, the protective effects against Fe2+-induced DNA breakage by MRPs were lost at high coffee MRP concentrations, irrespective of the incubation method used. Increasingly higher concentrations of MRPs in combination with Fe2+ actually enhanced the breakage of DNA with respect to the control. These results indicate that MRPs at high concentrations do not improve Fe2+ ion chelation, but rather accelerate the DNA breakage by possibly changing the redox state of the transition element.