Exciplex Studies. II. Indole and Indole Derivatives

Walker, M. S.; Bednar, Thomas W.; Lumry, Rufus

doi:10.1063/1.1711983

Cited by 166 publications

(55 citation statements)

References 23 publications

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“…(49,53) have made similar observations for indole in several mixtures of polar and nonpolar solvents and have proposed that a specific and stoichiometric complex, or "exciplex," is formed by the excited indole molecule and the polar solvent [an example of mechanism (2)]. This model has been applied with some success to observations of the fluorescence of indole in pentane in the presence of low levels of several alcohols, including methanol and butanol.…”

Section: Solventmentioning

confidence: 77%

“…(47) The influence of solvent upon the fluorescence properties of indole and tryptophan derivatives has received considerable attention. summarizes the effects of solvents of varying polarity upon the wavelengths of maximum fluorescence intensity for indole and N-acetyltryptophan methyl ester; the data are from Van Duuren, (29) Cowgill, (48) and Walker et al (49) The general pattern of behavior is unambiguous. The emission wavelength is dearly shifted to the red with increasing solvent polarity, whereas solvent effects on the absorption spectrum of indole are small.…”

Section: Solventmentioning

confidence: 91%

See 1 more Smart Citation

The Luminescence of the Aromatic Amino Acids

Weinryb

Steiner

1971

Excited States of Proteins and Nucleic Acids

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Section: Solventmentioning

confidence: 77%

Section: Solventmentioning

confidence: 91%

The Luminescence of the Aromatic Amino Acids

Weinryb

Steiner

1971

Excited States of Proteins and Nucleic Acids

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“…[10][11][12] It was suggested that indole forms an excited-state complex (exciplex) with solvent molecules, and that stabilization of the exciplex is achieved by charge transfer states. [13,14] A different explanation is level inversion, which proposes that due to its polar nature, the L a state is stabilized in the presence of a polar solvent, and becomes the lowest emitting state in polar solvents. [9] Computational studies of the photophysics of indole are inherently involved, as they require the accurate description of the excited states of the molecule along with a detailed account of its environment.…”

Section: Introductionmentioning

confidence: 98%

Explaining Level Inversion of the L_a and L_b States of Indole and Indole Derivatives in Polar Solvents

Brisker-Klaiman

Dreuw

2015

ChemPhysChem

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Quantum chemical methods are used to study the solvent effects on the spectra of indole and a series of methyl-substituted indoles. We focus on the low-lying L(a) and L(b) states and study their interplay. We find that the solvent mainly affects emission from the L(a) state, by stabilizing its energy in its excited-state geometry. The stabilization of the L(a) state increases with increasing solvent polarity, which accounts for the large fluorescence shift observed in indoles and leads to an inversion in the nature of the lowest emitting state, from L(b) in vacuum to L(a) in water. To the best of our knowledge, this is the first theoretical evidence for level inversion done for a series of indoles. The underlying mechanism of level inversion is analyzed in detail. The usual interpretation of level inversion in terms of their static dipole moment is criticized and an improved predictive measurement is suggested.

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“…1. In this model, the emitting state of a tryptophan exposed to solvent arises from an exciplex, i.e., the state reached by absorption is higher in energy than the state that emits (16). The magnitude of the splitting between the absorbing and emitting states depends upon environment, and is expected to be largest in Trp 62, which is exposed most fully to the aqueous solvent.…”

Section: Fluorescence Quantum Yieldsmentioning

confidence: 99%

Fluorescence of Lysozyme: Emissions from Tryptophan Residues 62 and 108 and Energy Migration

Imoto

Forster

Rupley

et al. 1972

Proc. Natl. Acad. Sci. U.S.A.

278

168

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The bulk of the fluorescence of lysozyme is located in Trp 62 and Trp 108. By examination of the fluorescence of derivatives in which Trp 62 and/or Trp 108 are specifically oxidized, it has been possible to detect a pH-dependent interaction between tryptophan residues. This interaction is interpreted as energy transfer from Trp 108 to Trp 62.The efficiency of tryptophan fluorescence in proteins varies widely from one protein to another, with quantum yields ranging from about 0.025 to greater than 0.4 (1). In proteins containing more than one tryptophan, each residue can contribute differently to the emission intensity (2). Studies of tryptophan emission in model compounds clearly demonstrate the great sensitivity of the emission intensity to environment (3); fluorescence measurements have been extensively used to obtain information about tryptophan environments in proteins (4). The analysis and interpretation of luminescence data when the protein contains more than one tryptophan are highly uncertain. It is seldom possible to separate unambiguously the contributions of each tryptophan to the total emission. Energy transfer from tyrosine to tryptophan is, in some cases, a complicating factor (5). Evidence for intertryptophanyl energy transfer has been presented (6), although such transfer is commonly ignored.Lysozyme is a very useful substrate for fluorescence studies for three reasons: (i) The tryptophan to tyrosine ratio is high (2: 1), and interference from tyrosine emission and/or tyrosine to tryptophan energy transfer is minimal; (ii) Derivatives can be prepared in which tryptophan (residue 62 or 108) is specifically oxidized (7); and (iii) The crystal structures of the native protein and several protein-saccharide complexes are known (8).In the present work, we evaluate the contributions of individual tryptophans to the emission and provide evidence for intertryptophanyl energy transfer in the fluorescence of lysozyme. MATERIALS AND METHODSThe quantum yields of native, oxindole 62, and oxindole 108 lysozymes were measured relative to tryptophan in H20 with an Aminco-Bowman spectrofluorometer (30°, 0.1 ionic strength). The emission spectra were corrected by comparison with a corrected tryptophan spectrum generously provided by the Turner Instrument Co. The quantum yields of oxindole 62,108 lysozyme were obtained with an instrument of conventional design but greater sensitivity, assembled in this laboratory. Absorbance at 280 nm was in all cases kept below 0.1. Guanidine hydrochloride (guanidine) was ultrapure from Mann; N-bromosuccinimide was from Matheson; lysozyme. was from Worthington. The oxindole-108 derivative was prepared by iodine oxidation to give the oxindolealanine-108, Glu 35 ester, followed by guanidine denaturation and refolding to generate the oxindolealanine-108 protein by hydrolysis of the ester (ref. 7; Imoto and Rupley, unpublished). N-bromosuccinimide oxidation (7) of native or oxindole-108 lysozyme gave the oxindole-62 or oxindole 62,108 derivatives. RESULTS Excitation and emiss...

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Exciplex Studies. II. Indole and Indole Derivatives

Cited by 166 publications

References 23 publications

The Luminescence of the Aromatic Amino Acids

The Luminescence of the Aromatic Amino Acids

Explaining Level Inversion of the L_a and L_b States of Indole and Indole Derivatives in Polar Solvents

Fluorescence of Lysozyme: Emissions from Tryptophan Residues 62 and 108 and Energy Migration

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Exciplex Studies. II. Indole and Indole Derivatives

Cited by 166 publications

References 23 publications

The Luminescence of the Aromatic Amino Acids

The Luminescence of the Aromatic Amino Acids

Explaining Level Inversion of the La and Lb States of Indole and Indole Derivatives in Polar Solvents

Fluorescence of Lysozyme: Emissions from Tryptophan Residues 62 and 108 and Energy Migration

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Explaining Level Inversion of the L_a and L_b States of Indole and Indole Derivatives in Polar Solvents