Log‐Normal Description of Fluorescence Spectra of Organic Fluorophores

Abstract

The smooth fluorescence bands of various organic fluorophores of different classes (e. g. indole, tryptophan, tyrosine, phthalimides, quinine sulfate, aminopyridines, acetylanthracenes) in different ionization states of their substituents and dissolved in various solvents can be accurately fitted on the frequency (wavenumber) scale by the four‐parametric log‐normal distribution curves up to the far spectral wings. This fact suggests that the log‐normal function is a good analytical description for smooth emission spectra of so‐called complex molecules. Examination of log‐normal parameters of 126 spectra of several tryptophan derivatives measured in different ionization states in various solvents revealed a straight‐linear relation between three shape parameters of the log‐normal function, namely, the positions of spectral maxima and of the two half‐maximal amplitudes. This fact indicates that only one parameter is needed to describe the band shape for the set of tryptophan derivatives. A similar linearity was also observed for the series of spectra of 1‐ and 2‐acetylanthracenes or 3‐amino‐N‐methyl‐phthalimides when varying the solvent. As a result, the spectral maximum position can entirely determine the shape of emission spectra of a series of a fluorophore derivatives in any environmental condition. Such a simplified mathematical representation significantly facilitates the problem of analytical resolution of composite fluorescence spectra, for instance, those of proteins.

Picosecond Fluorescence Relaxation Spectroscopy of the Calcium-Discharged Photoproteins Aequorin and Obelin

“…Fitting with two log-normal functions yields one distribution with skewness close to unity, and this function was therefore replaced by a Gaussian. Gaussian and log-normal lineshapes very adequately describe fluorescence emission spectra for a range of (bio)organic chromophores (20). As a consequence, this fitting procedure has the advantage over the first fitting procedure that it is closer to a physically meaningful description of the data.…”

“…In addition to the 45 ps decay component, there is a small component with ∼4 ns decay. The low energy band (21 000 (20) cm -1 at 25 ps) shifts 670(50) cm -1 in 260(50) ps and shows a slower redshift of 380(30) cm -1 in ∼4 ns. The intensity of this 21 000 cm -1 band decays biexponentially: 40% with a lifetime of 500(50) ps and 60% 2.7 ns.…”

The protein fluorescence and structural toolkit: Database and programs for the analysis of protein fluorescence and structural data

“…8 The input file for the fluorescence analysis contains the fluorescence spectra of protein measured without an external quencher of tryptophan fluorescence or with different concentrations of the quencher. Acrylamide, negatively charged iodide ions (I 2 ) or (NO 3 2 ) and positively charged cesium ions (Cs 1 ) can be used as quenchers of a The wavelengths of the most probable position of emission of tryptophan residues, which belong to various spectral classes, revealed from the analysis of the fluorescence spectra of 160 proteins. The wavelengths of the spectral positions of emission of tryptophan residues, which belong to various structural classes, predicted from the analysis of six structural parameters of environment of 137 tryptophan residues of 48 proteins from PDB.…”

The N-terminal Domain Tethers the Voltage-gated Calcium Channel β2e-subunit to the Plasma Membrane via Electrostatic and Hydrophobic Interactions

“…Data analysis was performed using Origin (OriginLab) and SigmaPlot (Systat Software). To infer the wavelength of maximal emission, a log-normal distribution was fitted to the spectra (22). For the quantification of binding of vesicles to the peptide, it was assumed that the fluorescence emission results from a two-state equilibrium between unbound and bound peptide.…”