Free radical initiation in proteins and amino acids by ionizing and ultraviolet radiations and lipid oxidation--Part 22: ultraviolet radiation and photolysis

Sunlight Inactivation of Enveloped Viruses in Clear Water

Enveloped virus fate in the environment is not well understood; there are no quantitative data on sunlight inactivation of enveloped viruses in water. Herein, we measured the sunlight inactivation of two enveloped viruses (Phi6 and murine hepatitis virus, MHV) and a nonenveloped virus (MS2) over time in clear water with simulated sunlight exposure. We attenuated UV sunlight wavelengths using long-pass 50% cutoff filters at 280, 305, and 320 nm. With the lowest UV attenuation tested, all decay rate constants (corrected for UV light screening, k̂) were significantly different from dark controls; the MS2 k̂ was equal to 4.5 m2/MJ, compared to 16 m2/MJ for Phi6 and 52 m2/MJ for MHV. With the highest UV attenuation tested, only k̂ for MHV (6.1 m2/MJ) was different from the dark control. Results indicate that the two enveloped viruses decay faster than the nonenveloped virus studied, and k̂ are significantly impacted by UV attenuation. Differences in k̂ may be due to the presence of viral envelopes but may also be related to other differing intrinsic properties of the viruses, including genome length and composition. Reported k̂ values can inform strategies to reduce the risk from exposure to enveloped viruses in the environment.

Investigation and application of photochemically induced direct UV detection of low or non-UV absorbing compounds by capillary electrophoresis

Some low or non-UV absorbing compounds like amino acids might be accessible to direct UV detection by capillary electrophoresis (CE), due to the photochemical reaction in the detection window of the separation capillary under extremely strong alkaline conditions. However, with regards to the photochemical reaction procedure and the influencing factors in CE, no comprehensive studies have been done. Herein, two strategies were applied to investigate the photochemical reaction mechanism including the introduction of an additional UV lamp and the utilization of driving pressure. The former confirmed the occurrence of photolysis, while the latter solved the interference of electroosmotic flow (EOF). Furthermore, the online photochemical reaction and online preconcentration technique were combined to develop a rapid, simple and sensitive method for determination of seven essential amino acids (valine, leucine, phenylalanine, methionine, tryptophan, threonine and lysine). Eventually, the developed method was successfully applied to the analysis of real samples with good reproducibility and reliability. This novel and simple method, based on the photochemical reactions occurring in the detection window and coupling with online preconcentration techniques, shows a great potential for the rapid and sensitive detection of low or non-UV absorbing compounds.

Proteomic analysis of UVC irradiation-induced damage of plasma proteins: Serum amyloid P component as a major target of photolysis

Ultraviolet-C (UVC) irradiation is a pathogen inactivation method used for disinfection of pharmaceutical products derived from human blood. Previous studies have shown that UVC can potentially damage proteins through photolysis or can generate reactive species resulting in protein thiol oxidation. In this study, two fluorescence-based quantitative proteomic approaches were used to assess the effects of a novel UVC-disinfection strategy on human plasma fractions. We show minimal changes in protein content, but gross alterations in protein thiol reactivity, indicative of oxidative damage. We identify a number of the damaged proteins by mass spectrometry, including serum amyloid P component, and further demonstrate UVC-induced photolysis of its disulphide bond.

Mechanism of pH-dependent photolysis of aliphatic amino acids and enantiomeric enrichment of racemic leucine by circularly polarized light

It has been proposed that the origin of biological homochirality may be the result of irradiation of a racemic sample of amino acids by circularly polarized light (CPL). To determine the mechanism of enantiomeric enrichment, the irradiation of aliphatic amino acids by CPL was undertaken. An enantiomerically enriched sample (e.g., L isomer enrichment from r-CPL) was found to result from the preferential excitation/decomposition of one enantiomer over another via a Norrish Type II mechanism (leucine, valine, and isoleucine), with the enantiomeric excess dependent on the degree of protonation of the amino/carboxylic acid moiety.

Factors affecting DNA damage caused by lipid hydroperoxides and aldehydes

Single (SSB) and double strand breaks (DSB) in supercoiled plasmid DNA pBR322 reacted with linoleic acid hydroperoxides (LOOH) were followed by agarose gel electrophoresis to obtain definitive information about factors affecting LOOH interaction with DNA. In water, LOOH induced extensive DSB, which were metal mediated and increased with incubation time. Adventitious metal bound to DNA was sufficient to decompose LOOH to reactive radicals, activity that was not readily inhibited by chelators DTPA and desferrioxamine. Added Fe2+ and Fe3+ increased SSB and DSB, although the effects of Fe2+ were more extensive. Above 100 microM both valences inhibited DNA damage. Strand breakage by LOOH proceeded via lipid alkoxyl and peroxyl radicals. Aldehydic lipid peroxidation products induced strand breaks via oxidation of double bonds, not by reactions of the carbonyl groups. Lipophilic antioxidants BHA, BHT, and alpha-tocopherol were about 20 times more effective than hydrophilic free radical scavengers sodium benzoate, inositol, DMSO, and mannitol in preventing LOOH-induced strand breaks, supporting lipid phase localization of the damage.

Vitamin E protects proteins against free radical damage in lipid environments

The fragmentation of the membrane protein monoamine oxidase in submitochondrial particles was induced by defined free radicals during radiolysis and by a system dependent on hydrogen peroxide and a transition metal. By injection of alpha-tocopherol in vivo, the levels of this physiological antioxidant in the mitochondrial preparations could be elevated more than ten-fold. In both radical-generating systems the presence of high levels of alpha-tocopherol in the membrane substantially retarded the protein fragmentation, in parallel with lipid peroxidation. It is suggested that membrane-bound proteins are damaged during lipid peroxidation and that alpha-tocopherol protects cells against both types of damage.

Contact site of histones 2A and 2B in chromatin and in solution

Irradiation of isolated nuclei or of a complex of histones 2A (H2A) and 2B (H2B) with ultraviolet light produces a covalent cross-link between H2A and H2B. Sequence analysis of the peptides isolated from the H2A-H2B dimer formed in solution and in nuclei demonstrated that both dimers are produced through the covalent linkage of Tyr-40 of H2B and Pro-26 of H2A. Tyrosyl residues proximal to Tyr-40 did not produce a cross-link with H2A, thereby indicating that strict conformational parameters are required for production of the H2A-H2B cross-link. We conclude that the precise juxtaposition of Tyr-40 of H2B and Pro-26 of H2A in this region of the H2A/H2B contact site is not altered upon interaction of these histones with H3 and H4 (tetramer), DNA, or other chromosomal components during nucleosome assembly.