Photosensitive Damage Research Articles

Photosensitive damage of dipeptides: mechanism and influence of structure.

We illustrate the influence of the dipeptide structure on photosensitive damage and the kinetic mechanism was investigated using acenaphthenequinone (ACQ) as a triplet photosensitizer. With tyrosine (Tyr) serving as the core structure, two classic dipeptides with double (trptophan-tyrosine, Trp-Tyr) and single (tyrosine-alanine, Tyr-Ala and Ala-Tyr) active reaction sites were constructed, and the underlying photodamage mechanisms were investigated carefully. According to the experimental results, the proton-coupled electron transfer processes between ACQ and numerous Trp-Tyr reaction sites have independent reaction properties. The bimolecular quenching rate (kq) value is roughly equivalent to the sum of the rates of two amino acid monomers, and a novel intramolecular dynamic channel between Trp/N˙-Tyr and Trp-Tyr/O˙ was observed. The ACQ/Tyr-Ala system demonstrated the key role of steric hindrance on the kq in bimolecular reactions.

2-Oxopurine Riboside: A Dual Fluorescent Analog and Photosensitizer for RNA/DNA Research.

There is significant interest in developing suitable nucleoside analogs exhibiting high fluorescence and triplet yields to investigate the structure, dynamics, and binding properties of nucleic acids and promote selective photosensitized damage to DNA/RNA, respectively. In this study, steady-state, laser flash photolysis, time-resolved IR luminescence, and femtosecond broad-band transient absorption spectroscopies are combined with quantum chemical calculations to elucidate the excited-state dynamics of 2-oxopurine riboside in aqueous solution and to investigate its prospective use as a fluorescent or photosensitizer analog. The Franck-Condon population in the S1 (ππ*) state decays through a combination of solvent and conformational relaxation to its minimum in 1.9 ps. The population trapped in the 1ππ* minimum bifurcates to either fluoresce or intersystem cross to the triplet manifold within ca. 5 ns, while another fraction of the population decays nonradiatively to the ground state. It is demonstrated that 2-oxopurine riboside exhibits both high fluorescent (48%) and significant triplet (between 10% and 52%) yields, leading to a yield of singlet oxygen generation of 10%, making this nucleoside analog a dual fluorescent and photosensitizer analog for DNA and RNA research.

Evaluation of phototoxicity induced by the anticancer drug rucaparib

Rucaparib (RCP) is a potent selective inhibitor of both PARP-1 and PARP-2 enzymes that induces synthetic lethality in cancer cells. It is used for the treatment of breast and ovarian tumors harboring deleterious germline or somatic cancer susceptibility genes mutations. Although RCP has an indole chromophore in its structure, it displays a bathochromic shift of the absorption band towards the UVA region of sunlight, thus extending the active fraction of solar light able to produce photosensitivity reactions. In this context, it is highly interesting to study the photo(geno)toxicity disorders associated with this drug, bearing in mind that, for dermatologists it is crucial to understand the toxicity mechanism to improve clinical management. In the present work, RCP has shown to be potentially phototoxic, as observed in the neutral red uptake phototoxicity test. Moreover, this significant phototoxicity is attributed to both proteins and genomic DNA, as revealed in the protein photooxidation and comet assays. The results obtained are highly relevant concerning RCP photosafety and become clinically important in the context of identification of the cutaneous adverse events that can be associated with the targeted therapies. Interestingly, this is the first example of a PARP inhibitor able to induce photosensitized damage to biomolecules.

Photo-induced oxidative damage to dissolved free amino acids by the photosensitizer polycyclic musk tonalide: Transformation kinetics and mechanisms

Residue from the polycyclic musks (PCMs) in household and personal care products may harm human beings through skin exposure. To understand the health effects of PCMs when exposed to sunlight at molecular level, both experimental and computational methods were employed to investigate the photosensitized oxidation performance of 19 natural amino acids, the most basic unit of life. Results showed that a typical PCM, tonalide, acts as a photosensitizer to significantly increase photo-induced oxidative damage to amino acids. Both common and exceptional transformation pathways occurred during the photosensitization damage of amino acids. Experimental tests further identified the different mechanisms involved. The common transformation pathway occurred through the electron transfer from α amino-group of amino acids, accompanying with the formation of O2•-. This pathway was controlled by the electronic density of N atom in α amino-group. The exceptional transformation pathway was identified only for five amino acids, mainly due to the reactions with reactive oxygen species, e.g. 1O2 and excited triplet state molecules. Additionally, tonalide photo-induced transformation products could further accelerate the photosensitization of all amino acids with the common pathway. This study may support the protection of human health, and suggests the possible need to further restrict polycyclic musks use.

Graphene oxide: A potential bodyguard protecting proteins from photosensitive damage

Oxidative damage of proteins or DNA strands induced by UV irradiation certainly brings inflammation, gene mutation, immunosuppression, even causes carcinogenesis to creatures. Here, we show that graphene oxide nanosheets (GONs) can significantly reduce the photosensitizer-mediated oxidative damage of proteins, caused by UV irradiation. GONs act as absorbers, physically shielding the proteins from UV light, but they participate in the photochemical reactions between photo-activated species and proteins as well. They quench transient species of photosensitizers by energy transfer and electron transfer, reduce highly toxic singlet oxygen yield and repair damaged protein residues. Our results may help revise and broaden previous findings concerning photochemical behavior and photo-biological effects of GONs.

Tetrakis(N-methyl-p-pyridinio)porphyrin and its zinc complex can photosensitize damage of human serum albumin through electron transfer and singlet oxygen generation

The photosensitized protein-damaging activity of water-soluble freebase tetrakis([Formula: see text]-methyl-[Formula: see text]-pyridinio)porphyrin (H2TMPyP), and its zinc complex (ZnTMPyP) was investigated using human serum albumin (HSA) as a target protein. These porphyrins bound to HSA and caused photosensitized oxidation of the tryptophan residue. The protein damage was enhanced in deuterium oxide and inhibited by sodium azide, a physical quencher of singlet oxygen, suggesting the contribution of singlet oxygen. However, an excess amount of sodium azide could not completely inhibit protein damage. These findings suggest the partial contribution of another mechanism to the protein damage, possibly the electron transfer mechanism. The Gibbs free energy of the electron transfer mechanism showed that electron transfer-mediated tryptophan oxidation by photoexcited H2TMPyP is more advantageous than that by ZnTMPyP. Actually, the quantum yield of protein damage through electron transfer by H2TMPyP was larger than that by ZnTMPyP. In addition, this study demonstrated that the association between porphyrin and protein plays an important role in photosensitized protein damage.

Graphene Oxide Transparent Hybrid Film and Its Ultraviolet Shielding Property.

Herein, we first reported a facile strategy to prepare functional Poly(vinyl alcohol) (PVA) hybrid film with well ultraviolet (UV) shielding property and visible light transmittance using graphene oxide nanosheets as UV-absorber. The absorbance of ultraviolet light at 300 nm can be up to 97.5%, while the transmittance of visible light at 500 nm keeps 40% plus. This hybrid film can protect protein from UVA light induced photosensitive damage, remarkably.

Photochemical Property and Photodynamic Activity of Tetrakis(2-naphthyl) Porphyrin Phosphorus(V) Complex

Photochemical Property and Photodynamic Activity of Tetrakis(2-naphthyl) Porphyrin Phosphorus(V) Complex

Photochemical properties of gemifloxacin: A laser flash photolysis study

The photochemical properties of gemifloxacin (GEFX), a fluoroquinolone antibacterial drug that exhibits phototoxicity toward biological substrates, were studied in aqueous solutions by laser flash photolysis (LFP) and pulse radiolysis. GEFX triplet state (3GEFX∗) absorption spectra showed maximum absorption at 510nm. 3GEFX∗ was quenched by naproxen (NAP) via energy transfer with a rate constant of 1.2×108dm3mol−1s−1. The energy of 3GEFX∗ was 266kJmol−1 and the transient absorption spectra showed direct evidence of electron transfer from 2′-deoxyguanosine-5′-monophosphate, N,N,N′,N′-tetramethyl-p-phenylenediamine, and tryptophan to 3GEFX∗ with bimolecular reaction rate constants of 4.1×106, 2.0×107, and 2.2×107dm3mol−1s−1, respectively. The rate constants for reactions of GEFX with OH, eaq− were found to be 1.5×1010 and 1.4×1010dm3mol−1s−1, respectively. The mechanisms and products of the photosensitive damage of lysozyme were related to the GEFX concentration, irradiation time, and ambient conditions.

Photosensitive damage of lysozyme caused by pazufloxacin and the protective effect of ferulic acid

Laser flash photolysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) experiments were carried out to study the photosensitive damage induced by pazufloxacin (PAX) and the protection of lysozyme (Lyso) by ferulic acid (FCA), an active antioxidant. Transient absorption spectra revealed electron transfer from Lyso and FCA to (3)PAX*, with respective bimolecular reaction rate constants of 6.3x10(7) and 1.4x10(10) dm(3)/(mol s). A pulse radiolysis study was also performed to investigate the formation of Lyso radical cations. Results showed that FCA effectively inhibits the cross-linking of protein induced by fluoroquinolones. Finally, a mechanism of the protective effect of FCA on Lyso was proposed.

Photosensitized Damage Inflicted on Plasma Membranes of Live Cells by An Extracellular Generator of Singlet Oxygen—A Linear Dependence of A Lethal Dose on Light Intensity

We describe a study of the influence of a dose rate, i.e. light intensity or photon flux, on the efficiency of induction of a loss of integrity of plasma membranes of live cells in culture. The influence of a photon flux on the size of the light dose, which was capable of causing lethal effects, was measured in an experimental system where singlet oxygen was generated exclusively outside of live cells by ruthenium(II) phenantroline complex. Instantaneous, sensitive detection of a loss of integrity of a plasma membrane was achieved by fluorescence confocal imaging of the entry of this complex into a cell interior. We demonstrate that the size of the lethal dose of light is directly proportional to the intensity of the exciting light. Thus, the probability of a photon of the exciting light inflicting photosensitized damage on plasma membranes diminishes with increasing density of the incident photons.

Hypericin-mediated photooxidative damage of α-crystallin in human lens epithelial cells

St. John’s wort (Hypericum perforatum), a perennial herb native to Europe, is widely used for and seems to be effective in treatment of mild to moderate depression. Hypericin, a singlet oxygen-generating photosensitizer that absorbs in both the visible and the UVA range, is considered to be one of the bioactive ingredients of St. John’s wort, and commercial preparations are frequently calibrated to contain a standard concentration. Hypericin can accumulate in ocular tissues, including lenses, and can bind in vitro to α-crystallin, a major lens protein. α-crystallin is required for lens transparency and also acts as a chaperone to ensure its own integrity and the integrity of all lens proteins. Because there is no crystallin turnover, damage to α-crystallin is cumulative over the lifetime of the lens and can lead to cataracts, the principal cause of blindness worldwide. In this work we study hypericin photosensitization of α-crystallin and detect extensive polymerization of bovine α-crystallin exposed in vitro to hypericin and UVA. We use fluorescence confocal microscopy to visualize binding between hypericin and α-crystallin in a human lens epithelial (HLE) cell line. Further, we show that UVA irradiation of hypericin-treated HLE cells results in a dramatic decrease in α-crystallin detection concurrent with a dramatic accumulation of the tryptophan oxidation product N-formylkynurenine (NFK). Examination of actin in HLE cells indicates that this cytoskeleton protein accumulates NFK resulting from hypericin-mediated photosensitization. This work also shows that filtration of wavelengths <400nm provides incomplete protection against α-crystallin modification and NFK accumulation, suggesting that even by wearing UV-blocking sunglasses, routine users of St. John’s wort cannot adequately shield their lenses from hypericin-mediated photosensitized damage.

Reactive oxygen species from type-I photosensitized reactions contribute to the light-induced wilting of dark-grown pea (Pisum sativum) epicotyls.

Type-II, singlet oxygen-mediated photosensitized damage has already been shown to occur in epicotyls of dark-germinated pea (Pisum sativum L.) seedlings upon illumination, resulting in fast turgor loss and wilting. In this study we show evidence that the palette of reactive oxygen species (ROS) is more complex. Hydrogen peroxide, superoxide and hydroxyl radicals are also formed, suggesting the occurrence of type-I reactions as well. Moreover, hydrogen peroxide injection into the epicotyls in the dark was able to provoke wilting directly. Formation of hydroxyl radicals could also be triggered by the addition of hydrogen peroxide in the dark, preferentially in the mid-sections where wilting occurs, showing that potential mediators of a Fenton reaction are present in the epicotyls, but unevenly distributed. Localization of light-inducible ROS formation fully (hydrogen peroxide) or partially (superoxide radicals) overlaps with the distribution of monomer protochlorophyllide complexes, showing that these pigment forms are capable of provoking both type-I and type-II reactions.

Raman spectroscopic study of photosensitive damage to lysozyme structure sensitized by hypocrellin A

Laser Raman spectroscopy was used to detect the nature of the structural change in lysozyme sensitized by hypocrellin A (HA) at the molecular level. The results indicated that the orderly structure of lysozyme has been damaged by the active oxygen (1O2, O2−·and.OH, etc.) generated by HA, and cause the changes in H-bonds system of the main chain and the side chain of lysozyme.

Raman spectroscopic study on structure of human immunodeficiency virus (HIV) and hypericin-induced photosensitive damage of HIV

The first Raman spectra of HIV1-HIV2 in human sera and hypericin-induced photosensitive damage of the virus have been obtained. The prominent Raman lines in the spectra are assigned respectively to the carbohydrates of viral glycoprotein, RNA, protein and lipid. The spectra are dominated by Raman scattering of the carbohydrates. The lines of D-Mannose and N-acetylglucosamine in carbohydrates are obvious and there is a beta-configuration in the anomeric C1 position in D-Mannose. The viral RNA duplexes bound assumes an A-form geometry. The lines of backbone phosphate group, bases (involving interbase hydrogen bonding) and ribose of the RNA are complete and distinct. The secondary structure of the viral protein maintains alpha-helix, beta-sheet, beta-turn and random coil. Its side chains are rich and vary from tryptophan, phenylalanine and "buried" tyrosine; the stable conformation of the S-S bond of gauche-gauche-gauche; the two forms of C-S bonds of gauche and trans; to sulfhydrl group and ionized and unionized carboxyl groups. The viral lipid bilayer molecules are probably in the liquid ordered phase or the gel phase. It was observed that the hypericin-induced photosensitive damage of HIV1-HIV2 in human sera changed various components of HIV1-HIV2 in different degrees: The orderly A-form viral RNA would become a disordered viral RNA. There were a breakage of interbase hydrogen bonds and disruption of vertical base-base stacking interactions. In addition, the groups of ribos and four bases were damaged obviously. A decrease in ordered structure (alpha-helix and beta-sheet) of viral protein is accompanied by an increase in random coil. The Tyr buried in the three-dimensional structure of protein was damaged, but it was still "buried" and the damage of C-S bond of trans form was stronger. The groups of carbohydrates, including D-Mannos and N-acetyl glucosamine, in viral envelope glycoprotein had also been changed. The hydrophilic C-N bond of choline in viral lipid was damaged, which was the possible binding site to hypericin, whereas the viral lipids bilayers were still probably in the liquid ordered phase or the gel phase. So the space structure of HIV1-HIV2 was damaged under the experimental conditions, which might block viral infection and inhibit its growth and breeding. It is apparent that the laser Raman spectra have provided certain direct evidence at the molecular level for photosensitive damage of HIV1-HIV2.

Raman spectroscopic study on structure of human immu-nodeficiency virus (HIV) and hypericin-induced photosen-sitive damage of HIV

Raman spectroscopic study on structure of human immu-nodeficiency virus (HIV) and hypericin-induced photosen-sitive damage of HIV

Synthesis and Photodynamic Therapy Properties of a Water-Soluble Hypocrellin Modified by Cyclodextrin

Abstract For improving water solubility of hypocrellin B (HB), a cyclodextrin modified hypocrellin B (HBCD) was designed and synthesized. Electron spin resonance (ESR) measurement indicated that this HB derivative remained photodynamically active in terms of type I and type II mechanisms. HBCD is water-soluble and possesses stronger photosensitized damage ability to calf thymus DNA than hypocrellin B.

Photosensitized light-induced damage of IRBP (interphotoreceptor retinoid-binding protein): Effects on binding properties

Purpose. To determine if IRBP (interphotoreceptor retinoid-binding protein) is damaged following irradiation by visible light in the presence of bound all- trans retinal. Methods. Following irradiation of the IRBP-all- trans retinal complex, the retinal was removed and damage to IRBP measured as loss of titratable thiol groups, loss of tryptophan fluorescence, and changes in retinol-binding-induced fluorescence. Results. IRBP irradiated by itself showed only minimal loss of tryptophan fluorescence; this loss was substantially in-creased by irradiation in the presence of all- trans retinal. Thiol groups and retinol-binding activity were also shown to be reduced. The damage to IRBP seemed to involve photosen-sitization by the all- trans retinal, which was in turn protected from bleaching by the IRBP. The binding affinity was shown to be reduced ten-fold following irradiation. Conclusion. In the eye, IRBP can stabilise vitamin A and debatably may be responsible for transport of different forms of vitamin A between the photoreceptor cells and pigment epithelium. If this is the case, it would play a key role in rhodopsin regeneration after bleaching. IRBP also appears to be necessary to sustain photoreceptor cells. Light was shown to cause photosensitized damage to IRBP, and thus might impair the regeneration process and photoreceptor viability.

Raman spectroscopic characteristics of microcosmic and photosensitive damage on space structure of liposomes sensitized by hypocrellin and its derivatives

Raman spect-pic characteristics of microcosmic and photosensitive damage on space structure of DP-PC liposomes sensitized by hypocrellin and its derivatives are obvious. The trans conformation decreased and the gauche conformation increased. The longitudinal order-parameter in chains and the lateral order-parameter between chains decreased in different degrees. The lateral packing became loose. Photodamage on the liposomes sensitized by 5-Br-hypocrellin B was stronger than that by hypocrellins A and B.

Raman spectroscopic study of DNA after photosensitive damage caused by hypocrellins A and B

Laser Raman spectroscopy provided the direct evidence for microcosmic photodamage in space structure of DNA molecule. When photosensitive damage was made to space structure of calf thymus DNA by hypocrellins A and B. the Raman characteristic frequencies and the intensities of the bands assigned to various groups of the components of DNA (phosphate backbone dsoxyribose and four bases) changed at various degrees. There were not only the strsnd breakage, but also the breakage of some H-bonds and disruption of vertical base-base stacking interactions. The photosensitive damage of hypocrellin B on DNA was stronger than that of hypocrellin A on DNA.