Photochemical inactivation of Pseudomonas aeruginosa

Adaptability to a broad range of environments together with relatively high resistance to antibiotics and to disinfectants makes Pseudomonas aeruginosa a concern in hospitals and in public health. We investigated whether UVA-mediated photochemical inactivation of P. aeruginosa could be accomplished with high efficiency while at the same time preserving the sensitivity of subsequent diagnostic tests. We characterized dose responses and bactericidal kinetic rates of 5-iodonaphthyl 1-azide (INA) and of amotosalen (AMO) as these substances exposed to UVA are known to inactivate germs with minimal impact to blood products or to viral antigens. Neither UVA without photochemicals nor INA or AMO in the dark inactivated bacteria. We found that AMO was ca 1000-fold more effective in inactivating P. aeruginosa cells than INA under similar conditions. Photoinactivation with either INA or AMO at conditions that abolished bacterial infectivity did not impair polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) testing. For comparison, similar titers of Bacillus atrophaeus spores (a surrogate for B. anthracis) remained unaffected at conditions that reduced the survival of P. aeruginosa below detection levels. The results presented in this study should assist in improved methods to inactivate P. aeruginosa in environmental, clinical and forensic samples without impairing subsequent nucleic acid- or immune-based analysis.     

Free radical inactivation of trypsin

Reactivities of free radical oxidants, ^.OH, Br^-·₂ and Cl₃COO^. and a reductant, CO^-·₂, with trypsin and reactive protein components were determined by pulse radiolysis of aqueous solutions at pH 7, 20°C. Highly reactive free radicals, ^.OH, Br^-·₂ and CO^-·₂, react with trypsin at diffusion controlled rates, k(^.OH + trypsin) = 8.2 × 10¹⁰ M^-1 s^-1, k(Br^-·₂ + trypsin) = 2.55 × 10⁹ M^-1 s^-1 and k(CO^-·₂ + trypsin) = 2.6 × 10⁹ M^-1 s^-1. Moderately reactive trichloroperoxy radical, k(Cl₃COO^. + trypsin) = 3 × 10⁸ M^-1 s^-1, preferentially oxidizes histidine residues. The efficiency of inactivation of trypsin by free radicals is inversely proportional to their reactivity. The yields of inactivation of trypsin by ^.OH, Br^-·₂ and CO^-·₂ are low, G(inactivation) = 0.6-0.8, which corresponds to ∾ 10% of the initially produced radicals. In contrast, Cl₃COO^. inactivates trypsin with ∾ 50% efficiency, i.e. G(inactivation) = 3.2.     

Photochemical inactivation of alpha- and poxviruses

The objective of this study was to determine whether photochemical inactivation of viruses could be accomplished with high efficiency while preserving the molecular integrity of viral targets allowing subsequent diagnostic tests to be performed at a lower level of containment and cost. We studied the effect of 5-iodonaphthyl 1-azide (INA) and amotosalen (AMO, also known as S-59), which are photochemicals known to target either viral proteins or nucleic acids, respectively. We found that vaccinia virus (VACV, an orthopox virus with a DNA genome) and pixuna virus (PIXV, an alphavirus with an RNA genome) were stable when irradiated with UVA alone or when exposed to either INA or AMO in the dark. AMO followed by UVA exposure was at least 1000-fold more virucidal than INA/UVA on vaccinia and pixuna viruses treated under similar conditions. Photoinactivation with either INA or AMO at conditions that abolished viral infectivity resulted in only minimal impairment of subsequent ELISA and PCR testing. The results presented in this study should assist in developing methods to inactivate in the field environmental and forensic samples suspected of viral contamination, thus limiting the need for costly security and safety operations after an accidental or intentional viral release.     

Serological properties of porcine trypsin subsequent to inactivation by various methods

Abstract— Porcine trypsin was inactivated by various methods (heat, autolysis, photodynamic action, ultraviolet light, and gamma-radiation) and the inactivated products were tested for their ability to precipitate porcine trypsin antiserum using the capillary fluid precipitin method. It was found that the chemical and structural modifications incurred with irradiation, sufficient to inactivate porcine trypsin, in contrast to heat and autolysis, did not interfere with those parts of the protein surface required for immunochemical reactivity.     

Probing the active site of trypsin with rose bengal: insights into the photodynamic inactivation of the enzyme

In this work the active site of trypsin has been probed with the dye rose bengal. The dye binds competitively to the enzyme, and it can be used as a probe of the active site of the enzyme. On the basis of the emission wavelength, the binding site of trypsin is relatively polar and is similar to that of acetone in its polarity. The triplet state of rose bengal is quenched by trypsin. This quenching may be caused by the tryptophan and tyrosine residues that are in the near vicinity of the trypsin active site. This quenching can compete with the formation of singlet oxygen from the excited triplet state of rose bengal. We demonstrate that the singlet oxygen involved in the photoinactivation of trypsin is produced by the free rose bengal in solution and the bound dye is incapable of producing singlet oxygen. This explains the lack of correlation between photoinactivation efficiency and sensitizer binding capability previously reported by Wade and Spikes.     

光化学烟雾

光化学烟雾是一种污染现象。本文从其形成机理、危害加以分析,并提出了防治措施。     

Photochemical synthesis of diaza-steroids

N-Iminopyridinium ylides 12 and 13 readily undergo regio-specific photoinduced ring expansion to the isomeric 1,2-diazepines 14 and 15 respectively. Similarly UV irradiation of the steroidal N-iminopyridinium ylide 25, which can be obtained from 19-nortestosterone, leads quantitatively and in a regiospecific manner to the corresponding diazepine 26. In a second photochemical reaction 26 gives the cyclobutene derivative 27. Variable temperature ¹H NMR and OCD measurements of the optically active diazepine 26 indicate that one of the two possible diastereoisomeric conformations is preferred.     

Photochemical crosslinking of polypropylene

A study was carried to determine experimentally the crosslinking of irradiated polypropylene by ultraviolet rays in vacuo. Three methods of detecting crosslinking were used: measuring the degree of swelling in decalin at room temperature, measuring the gel fraction in a tetrachloroethylene solution of the irradiated sample, and comparing the infrared spectra before and after irradiation. It was found that as the time of irradiation increases, the degree of swelling decreases, whereas the gel fraction in tetrachloroethylene solution increases. This shows that the crosslinking reaction proceeds with time. On the other hand, the infrared spectra of the irradiated sample remained almost unchanged, which shows that different bond species can hardly be formed by irradiation in vacuo. From these facts it may be concluded that the measurements amply confirm the hypothesis. Furthermore, it is demonstrated that ash residue in polypropylene plays an important role in photocrosslinking; that is, the photochemical primary process of the reaction is the absorption of light by the ash residue.     

Photochemical sulfochlorination of polyvinylthiophene

A study is made of the photochemical sulfochlorination of polyvinylthiophene, and the optimum conditions for introducing the chlorosulfonyl group determined.     

Photochemical transformations of xanthohumol

A photoinduced procedure for the addition of simple alcohols to xanthohumol, the major prenylated flavonoid of hop plants, has been developed. The reaction is regioselective, simple, and occurs in one pot to afford two new β adducts of xanthohumol.     

Photochemical Chlorophosphination of Phenylacetylene

Russian Journal of General Chemistry -