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PubMed1993

Promoter-specific synthetic photoendonuclease: rose bengal-labeled T7 RNA polymerase.

We have constructed a synthetic photoendonuclease composed of T7 RNA polymerase linked to rose bengal. The promoter-specific polymerase confers site-specific binding, and the photosensitizer rose bengal allows light-induced DNA cleavage. Using a gentle labeling procedure, we find that the polymerase can be labeled with 1-30 rose bengals. Polymerase labeled to about 8 rose bengals per molecule retains the same efficiency and specificity of binding to promoter-containing DNA as unlabeled polymerase. At this level of rose bengal substitution, the synthetic endonuclease, in the presence of visible light, specifically cleaves linear or supercoiled DNA containing a T7 promoter. It induces frank single-strand breaks, rather than labile sites convertible to breaks upon additional treatments. Neither the free rose bengal moiety not bonded to polymerase nor the free (not bound to DNA) rose bengal-substituted polymerase cleaves DNA. Although rose bengal is an efficient generator of singlet oxygen, depletion of oxygen from reaction mixtures increases the cleavage rate. This indicates that singlet oxygen cleavage is not a major mechanism of DNA nicking by the synthetic endonuclease. At higher levels of rose bengal substitution, the labeled polymerase shows decreased binding efficiency and increased nonspecific binding to DNA without a T7 promoter; the specificity of DNA cleavage also decreases. These results indicate that the site specificity of rose bengal photocleavage by the synthetic endonuclease results from specific binding of the polymerase, and thus rose bengal photonicking reflects polymerase binding.

Binding Sites↗
PubMed1989

Rapid electrophysiological changes leading to arrhythmias in the aerobic rat heart. Photosensitization studies with rose bengal-derived reactive oxygen intermediates.

The objective of this study was to determine whether reactive oxygen intermediates (e.g., singlet oxygen and the superoxide radical) can rapidly induce electrophysiological disturbances leading to the genesis of arrhythmias, even in the absence of ischemia and reperfusion. Rat hearts (n = 6 per group) were perfused aerobically at 37 degrees C for 10 minutes without rose bengal and for 5 minutes with rose bengal (250 nmol/l), during which time no changes in coronary flow or heart rate were observed. Hearts were then uniformly illuminated for 20 minutes with green light (530-590 nm) from 200 fiber optic cables. With light and without rose bengal, or vice versa, all hearts remained stable. However, in the illuminated rose bengal group, electrophysiological changes (inversion of the terminal portion of the T wave and an increase in Q-T interval) were observed within 11.8 +/- 2.1 seconds (i.e., less than 60 beats). All hearts exhibited ventricular premature beats (within 2.2 +/- 0.7 minutes) and ventricular tachycardia (within 2.8 +/- 0.7 minutes) before the occurrence of complete atrioventricular block (within 5.5 +/- 0.9 minutes). During the illumination period, coronary flow progressively fell in the rose bengal-perfused hearts from 11.6 +/- 0.5 ml/min to 2.0 +/- 0.4 ml/min (p less than 0.05 when compared with any control group). When a similar progressive reduction in coronary flow was mimicked (with or without rose bengal), no arrhythmias occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerobiosis↗
PubMed2005

Inhibition of vesicular glutamate uptake by Rose Bengal-related compounds: structure-activity relationship.

Synaptic vesicular accumulation of glutamate is a vital initial step in glutamate transmission. We have previously shown that Rose Bengal, a polyhalogenated fluorescein analog, is a potent inhibitor of glutamate uptake into synaptic vesicles. Here, we report the structural features of Rose Bengal required for this inhibition. Various Rose Bengal-related compounds, with systematic structural variations, were tested. Results indicate that the four iodo groups and the phenyl group attached to the xanthene moiety are critical for potent inhibitory activity. Replacement of these groups with two iodo groups and an alkyl group, respectively, results in substantial reduction in potency. Of further interest in creating high potency is the critical nature of the oxygen atom which links the two benzene rings of xanthene. Thus, the phenyl group and multiple iodo groups, as well as the bridging oxygen of xanthene, are crucial elements of Rose Bengal required for its potent inhibitory action.

Animals↗
PubMed1979

Photodynamically induced alteration of cornea endothelial cell function.

Corneal endothelial cells were perfused in the specular microscope with varying concentrations of rose bengal. Corneas perfused with rose bengal in concentrations of 10(-6)M to 10(-5)M and exposed to light for periods of 0.5 to 5 min swelled at rates which were more rapid with both increasing concentration of rose bengal and increasing duration of light exposure. Corneas perfused with similar concentrations of rose bengal but not exposed to light did not swell. Combining rose bengal with 100 micrograms/ml superoxide dismutase did not reduce the corneal swelling following exposure to light, indicating that the photodynamically induced endothelial bengal perfusing solution eliminated corneal swelling following exposure of corneas to light. This indicates that the photodynamic effect of endothelium is secondary to cell functional alterations from the hydrogen peroxide produced during the dismutation reaction of superoxide free radical which is catalyzed by superoxide dismutase.

Animals↗
PubMed1999

Photodynamic crosslinking of proteins. III. Kinetics of the FMN- and rose bengal-sensitized photooxidation and intermolecular crosslinking of model tyrosine-containing N-(2-hydroxypropyl)methacrylamide copolymers.

As part of a study on the role of Tyr residues in the photosensitized intermolecular crosslinking of proteins, we have surveyed the kinetics of the rose bengal- and flavin mononucleotide (FMN)-sensitized photooxidation and crosslinking of a water-soluble N-(2-hydroxypropyl)methacrylamide copolymer with attached 6-carbon side chains terminating in tyrosinamide groups (thus the -OH group of the Tyr is free, but both the amino and carboxyl groups are blocked, simulating the situation of a nonterminal Tyr in a protein). The intermolecular photodynamic crosslinking of the Tyr copolymer can result only from the formation of Tyr-Tyr (dityrosine) bonds, because the copolymer itself is not photooxidizable. Rose bengal, primarily a Type II (singlet oxygen) sensitizer, sensitized the rapid photooxidation of the Tyr residue in the Tyr copolymer only at high pH, where the Tyr phenolic group is ionized; crosslinking did not occur with rose bengal under any of the reaction conditions used. In contrast, FMN, which can sensitize by both Type I (free radical) and Type II processes, sensitized the photooxidation of the Tyr copolymer over the pH range 4-9.5. Also, significant photocrosslinking occurred, but only from pH 4 to 8, with a maximum rate at pH 6. Crosslinking required the presence of oxygen. Studies with inhibitors, D2O as solvent, catalase and superoxide dismutase indicated that the photooxidation and photocrosslinking of the Tyr copolymer with FMN at pH 6 were not mediated by singlet oxygen, superoxide or hydrogen peroxide. It appears that crosslinking involves the abstraction of an H atom from the Tyr phenolic group to give Tyr and FMN radicals. The Tyr radical in one Tyr copolymer can then react with a Tyr radical in another Tyr copolymer to give an intermolecular dityrosine crosslink.

Cross-Linking Reagents↗
PubMed1988

Double vital staining of corneal epithelium after corneal transplantation with a rose bengal-fluorescein mixture.

Longitudinal double vital staining with 1% rose bengal (RB) and 1% fluorescein (Flu) has been carried out on 33 eyes subjected to penetrating corneal transplantation. At the conclusion of the operation pronounced desiccation of both donor's and recipient's epithelium was seen in a scant 50%, but abrasion in only 8%. the desiccation subsided during the first post-operative day, but the donor's epithelium was rejected in the majority (91%). Healing started on the third day, manifesting itself by Flu-punctate whorl-shaped epithelium invading or gliding across the wound. By the fifth day nearly complete healing had occurred. In 9% no renewal of epithelium was noticed. Subsequent control examinations revealed loose sutures (RB-stained mucous adhesions), evanescent cicatricial defects, and open suture canals (Flu). Graft rejection occurred in 8 cases. In 5 of these, well-defined massive peripheral staining of donor epithelium was seen (RB most widespread and sharply outlined), and in the remaining 3, uncharacteristic, diffuse, punctate staining.

Cornea↗
PubMedDate not supplied

Rose bengal-sensitized photooxidation of 2-chlorophenol in water using solar simulated light.

The decomposition of 2-chlorophenol (2CP) in an aqueous solution by means of photosensitized oxidation using rose bengal has been studied. The influence of initial 2CP concentration, pH of reaction mixture and oxygen content on reaction rate has been observed. The reaction of 2CP with singlet oxygen (type II of photooxidation) appeared the most important pathway of degradation. The rate constants of singlet oxygen quenching and reaction with 2CP were determined and the rate constant of excited rose bengal quenching by 2CP was also estimated. An attempt was made to identify the main photooxidation products.

Chlorophenols↗
PubMed2002

Site-directed photochemical disruption of the actin cytoskeleton by actin-binding Rose Bengal-conjugates.

The in situ light-induced, non-enzymatic digestion of cytoskeletal actin by a xanthene dye conjugated to heavy meromyosin, anti-actin antibodies and/or anti-myosin antibodies is reported. The dye Rose Bengal was conjugated to either anti-actin antibodies, anti-myosin antibodies or heavy meromyosin. Under our experimental conditions, visible light induced the non-enzymatic breakdown of cytoskeletal actin when mammalian tissue culture cells were probed either with Rose Bengal-conjugated anti-actin and/or anti-myosin antibodies. Similar results were obtained when tissue culture cells were probed with Rose Bengal-conjugated heavy meromyosin before irradiation with visible light. The in situ photochemical reaction depended on the presence of actin-binding Rose Bengal-conjugates.

Actins↗