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Excimer
About: Excimer is a research topic. Over the lifetime, 3725 publications have been published within this topic receiving 75104 citations.
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TL;DR: In this article, pyrene was used as a probe to study the gelation of sodium deoxycholate at pH values close to neutrality, and the results suggest the formation of pyrene excimer as a result of the aggregation process: when two clusters carrying probes form a larger one, pyrene molecules can interact in both ground and excited states.
Abstract: Steady-state and time-resolved fluorescence have been used to study the gelation of sodium deoxycholate at pH values close to neutrality. Pyrene was used as a probe. The results suggest the formation of pyrene excimer as a result of the aggregation process: when two clusters carrying probes form a larger one, pyrene molecules can interact in both the ground and excited states. Fluorescence lifetimes for monomer and excimer pyrene are given and favorably compared to similar systems. A structure for the aggregates is also suggested.
47 citations
TL;DR: In this article, a variety of spectroscopic techniques have been used to demonstrate that genuine monomer emission can be observed from pyrene crystals and that emitting monomers appear to be located in disordered regions of the crystal situated within 5 × 102 nm of the surface.
Abstract: The phenomenon of monomer emission from excimer forming crystals has been investigated for pyrene and perylene. A variety of spectroscopic techniques have been used to demonstrate that genuine monomer emission can be observed from pyrene crystals. The emitting monomers appear to be located in disordered regions of the crystal situated within 5 × 102 nm of the surface. Both delayed monomer and excimer emission have been observed at 4.2°K and information on the range of the monomer exciton migration has been obtained. The low temperature emission observed from the dimeric α-form of perylene crystals appears to be either from highly perturbed perylene monomers located in disordered regions of the crystal or from impurities. The unusual temperature dependence previously observed for the emission spectrum of the monomeric β-form of perylene crystals is shown to be due largely to reabsorption effects.
46 citations
46 citations
TL;DR: It is shown that the presence of appreciable excimer fluorescence at temperatures below the N----X pretransition (initial excimer) is due to perturbation of the TM chain-chain interaction by the pyrenes at Cys-190, and that F-actin stabilizes tropomyosin by inhibiting the N ----X transition.
Abstract: The fluorescence of pyrene-TM [rabbit skeletal tropomyosin (TM) labeled at Cys with N-(1-pyrenyl)maleimide] consists of monomer and excimer bands [Betcher-Lange, S., & Lehrer, S.S. (1978) J. Biol. Chem. 253, 3757-3760]; an increase in excimer fluorescence with temperature is due to a shift in equilibrium from a chain-closed state (N) to a chain-open state (X) associated with a helix pretransition [Graceffa, P., & Lehrer, S.S. (1980) J. Biol. Chem. 255, 11296-11300]. In this study, we show that the presence of appreciable excimer fluorescence at temperatures below the N----X pretransition (initial excimer) is due to perturbation of the TM chain-chain interaction by the pyrenes at Cys-190. Fluorescence and ATPase titrations indicated that the label caused a decrease in TM binding to F-actin primarily due to reduced end to end TM interactions on the actin filament. Under conditions where pyrene-TM was bound to F-actin, however, the excimer fluorescence did not increase with temperature, indicating that F-actin stabilizes tropomyosin by inhibiting the N----X transition. The binding of myosin subfragment 1 (S1) to pyrene-TM-F-actin at low ratios to actin caused time-dependent changes in fluorescence. After equilibrium was reached, the initial excimer fluorescence was markedly reduced and remained constant over the pretransition temperature range. Further stabilization of tropomyosin conformation on F-actin is therefore associated with S1 binding. Effects of the binding of S1 to the F-actin-tropomyosin thin filament on the state of tropomyosin were studied by monitoring the monomer fluorescence of pyrene-TM.(ABSTRACT TRUNCATED AT 250 WORDS)
46 citations
Journal Article•
TL;DR: All aspects of excimer laser refractive surgery--techniques, indications and contraindications, clinical outcomes, and complications are discussed in detail.
Abstract: Excimer laser photorefractive keratectomy and excimer laser in situ keratomileusis are relatively new treatment modalities that can be used to correct refractive errors of the eye. They are most commonly used to correct myopia (nearsightedness) but can also be used to correct hyperopia (farsightedness) and astigmatism. The excimer laser alters the refractive state of the eye by removing tissue from the anterior cornea through a process known as photoablative decomposition. This process uses ultraviolet energy from the excimer laser to disrupt chemical bonds in the cornea without causing any thermal damage to surrounding tissue. The modified anterior corneal surface enables light to be focused on the retina, thereby reducing or eliminating the dependence on glasses and contact lenses. We discuss in detail all aspects of excimer laser refractive surgery--techniques, indications and contraindications, clinical outcomes, and complications.
46 citations