Intrinsic Tryptophan Fluorescence in the Detection and Analysis of Proteins: A Focus on Förster Resonance Energy Transfer Techniques

Abstract

Förster resonance energy transfer (FRET) occurs when the distance between a donor fluorophore and an acceptor is within 10 nm, and its application often necessitates fluorescent labeling of biological targets. However, covalent modification of biomolecules can inadvertently give rise to conformational and/or functional changes. This review describes the application of intrinsic protein fluorescence, predominantly derived from tryptophan (λEX ∼ 280 nm, λEM ∼ 350 nm), in protein-related research and mainly focuses on label-free FRET techniques. In terms of wavelength and intensity, tryptophan fluorescence is strongly influenced by its (or the protein’s) local environment, which, in addition to fluorescence quenching, has been applied to study protein conformational changes. Intrinsic Förster resonance energy transfer (iFRET), a recently developed technique, utilizes the intrinsic fluorescence of tryptophan in conjunction with target-specific fluorescent probes as FRET donors and acceptors, respectively, for real time detection of native proteins.

Interaction between quinoline yellow and human serum albumin: spectroscopic, chemometric and molecular docking studies

“…Changes in intrinsic fluorescence of a protein arising from tryptophan (Trp), tyrosine (Tyr), and phenylalanine (Phe) residues can be used to determine the binding sites and binding modes of ligands with proteins . As shown in Fig.…”

Fluorescence based real time monitoring of fouling in process chromatography

“…2B). This may be because, the tyrosine fluorescence for the mAb molecules has been observed to be quenched by the presence of nearby tryptophan moieties either through resonance energy transfer or the ionization of its aromatic hydroxyl group14. This suggests that the proposed approach can be effectively used for monitoring both the degradation/leaching of the protein A ligand as well as the deposition of foulants on the resin surface.…”

Biphasically Modulating the Activity of Carboxypeptidase G2 with Ultrasound

“…3B). Trp had a 2-nm blue-shift in L2/L3-treated sample, indicating a decrease of polarity [17]. These data manifested that the conformational transformation played a part in the enzymatic modulation (i.e., alteration of the specific activity).…”