Quenching mechanisms

The rhodamine B-bound complex of Ir1 (387) shows only minor alterations in the absorption spectrum of bound rhodamine B as opposed to free dye however, its fluorescence is strongly quenched.626 Fluorescence is intense when the rhodamine dye is attached to an Ir111 center. The authors conclude that the excited-state quenching mechanism is via electron transfer. 

Kirilovsky, D. (2007). Photoprotection in cyanobacteria The orange carotenoid protein (OCP)-related non-photochemical-quenching mechanism. Photosynth Res 93 7-16. 

Foote, C. S., Y. C. Chang, and R. W. Denny. 1970. Chemistry of singlet oxygen. XI. Cis-trans isomerization of carotenoids by singlet oxygen and a probable quenching mechanism. J. Am. Chem. Soc. 92 5218-5219. 

Recently, a biexcitonic quenching mechanism has been proposed to explain the variation of scintillation intensity in liquid argon (LAr) with the LET and quality of incident radiation (Hitachi et al., 1992). According to this, quenching occurs mainly in the track core due to high-energy deposition density. This... 

The commercialization of inexpensive robust LED and laser diode sources down to the uv region (370 nm) and cheaper fast electronics has boosted the application of luminescence lifetime-based sensors, using both the pump-and-probe and phase-sensitive techniques. The latter has found wider application in marketed optosensors since cheaper and more simple acquisition and data processing electronics are required due to the limited bandwidth of the sinusoidal tone(s) used for the luminophore excitation. Advantages of luminescence lifetime sensing also include the linearity of the Stem-Volmer plot, regardless the static or dynamic nature of the quenching mechanism (equation 10) ... 

The phosphorescence of Pt2 (I OsKHq in aqueous solution is quenched by l,l-bis(2-sulfoethyl)-4,4f-bipyridinium inner salt (BSEP). Transient absorption attributable to BSEP ( nax 610 nn) is observed in flash kinetic spectroscopic studies of aqueous solutions containing Pt2( Os Hq and BSEP, thereby establishing an electron transfer quenching mechanism ... 

Y Kawamura, J Brooks, JJ Brown, H Sasabe, and C Adachi, Intermolecular interaction and a concentration-quenching mechanism of phosphorescent Ir(III) complexes in a solid film, Phys. Rev. Lett., 96 017404-1-017404-4, 2006. 

At an MEK concentration greater than 1 M, both the dynamic and the static quenching mechanisms have to be taken into account. Therefore, Frank and Vavilov s model of combined static and dynamic quenching model (28),... 

By using pulsed laser sources and fast measuring devices, direct observation of redox products in flash photolysis experiments provides evidence regarding oxidative and reductive quenching mechanisms in Ru(bpy)3+. 

These features are consistent with the reductive quenching mechanism of Ru(bpy)3+ ... 

Masuhara H, Shioyama H, Saito T et al (1984) Fluorescence quenching mechanism of aromatic hydrocarbons by closed-shell heavy metal ions in aqueous and organic solutions. J Phys Chem 88 5868-5873... 

E. R. Carraway, J. N. Demas, and B. A. DeGraff, Luminescence quenching mechanism for microheterogeneous systems, Anal Chem. 63, 332-336 (1991). 

Quenching Mechanisms of Tyrosine Emission in Polypeptides and Proteins... 

In testing the possibility of proton transfer as a quenching mechanism of tyrosine in oligopeptide/polynucleotide complexes, Brun et a/.(102) compared the fluorescence emission spectra of the tyrosine and O-methyltyrosine tripeptides. They noted that, in the complex, the O-methyltyrosine tripeptide had a unique secondary emission near 410 nm. Whether this emission is related to that observed by Libertini and Small(94) is an important question. While one must consider the possibility that two tyrosine side chains could be converted to dityrosine, (96) which has a fluorescence at 400 nm, another intriguing possibility is ambient temperature tyrosine phosphorescence. This could happen if the tyrosine side chain is in a rigid, protective environment, very effectively shielded from collisions with quenchers, particularly oxygen. 

In the case of horse liver alcohol dehydrogenase, a homodimeric enzyme, Subramanian et al.(202) used the relative phosphorescence of tyrosine and tryptophan to examine the effects of various ternary complexes known to selectively quench the fluorescence of the tryptophans of each subunit. One proposed quenching mechanism is the formation of a ground-state tyrosinate in a ternary complex at neutral pH.(201) This tyrosinate, by being a resonance... 

The phosphorescence lifetimes of various proteins at room temperature are given in Table 3.1. Some variability in the lifetimes reported from lab to lab is evident, possibly due to different enzyme preparation, removal of oxygen (see below), or other conditions. Nevertheless, when measured under the same conditions, it is apparent that the tryptophan lifetimes vary dramatically from protein to protein. Alkaline phosphatase exhibits the longest lifetime from a protein in solution with a lifetime of 1.5—1.7 s at 22°C, approaching the lifetime of 5.5 s at 77 K. The lifetime of free indole in solution is 15—30 /is at 22°C.(38 39) Therefore, in the absence of other quenching mechanisms, the lower limit for the phosphorescence lifetime of a fully exposed tryptophan moiety in a protein should be about 20 /is. 

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