Coumarins as Fluorescent Labels of Biomolecules

Abstract

Important areas such as environmental sciences, medicine, pharmacy, and cellular biology are dependent on very sensitive analytical techniques. One of the most common methodologies used for their bioanalytical purposes is the fluorescent labelling. The synthesis of new fluorophores and the great development of fluorescent-labelling techniques combined with the enormous technological advances in the field of fluorescence microscopy allowed to deepen the structural knowledge of biomolecules. This new organic fluorophores form covalent bonds with the sample to be analyzed, producing stable bioconjugates that show fluorescence in a wide range of wavelengths, depending on the label used. Coumarin derivatives represent one of the most important chemical classes of organic fluorescent materials being one of the most extensively investigated and commercially significant groups of organic fluorescent materials. In this chapter, it is reviewed the use of fluorescent coumarin derivatives and their application to labelling biomolecules. These fluorescent labels allow researchers to study, and understand, biomolecular assemblies that exhibit complex sensitivity and selectivity. Reactive fluorescent coumarin derivatives are actually widely used in labelling biomolecules as peptides, proteins, oligonucleotides, nucleic acids, and carbohydrates, among other biological molecules.

Photoactivatable Fluorescent Tags for Dual-Modality Positron Emission Tomography Optical Imaging

“…Synthesis of the photoactivatable BODIPY analogue (3) was adapted from a published procedure. 46 Briefly, the methyl ester (10) was isolated in 18% yield after purification on silica gel by following the sequential reactions involving the following: (i) the condensation of methyl-4-formyl-benzoate with two equivalents of 2,4-dimethylpyrrole, (ii) oxidation using 2,3- RhodamineB-PEG 3 -ArN 3 (4) was obtained in three steps starting from rhodamine B. Rhodamine derivatives are prone to spirocyclization under basic conditions, and this results in a nonemissive isomer. 13 Therefore, to prevent spirocyclization, we introduced a piperazine moiety to lock the molecule in an "open" configuration by using methods adapted from Boltersdorf et al 47 Starting from rhodamine B, an amide bond formation with 1-Boc-piperazine was accomplished by using HBTU as an activating agent, whereupon purification on silica gel gave rhodamine (12) in 98% yield.…”

“…Many fluorescent dyes have been developed for protein labeling. The five main classes of fluorophores are derived from coumarin, fluorescein, BODIPY, rhodamine, and cyanine dyes. − As a reflection of the importance of fluorescent proteins, many different chemical technologies exist to modify proteins with fluorescent tags, but the majority of reagents rely on thermally mediated reactions that typically operate from room temperature to 37 °C. − For example, classic protein conjugation chemistry often involves amide bond formation using N -hydroxysuccinimide groups or thiourea synthesis from reagents bearing benzyl isothiocyanate (NCS) groups. − Labeling reagents built from these active functional groups are prone to hydrolysis, , and the protein conjugation chemistry is often intolerant to many of the formulation components (including salts, antioxidants like ascorbic acid, surfactants like polysorbate, or other solubilizing factors, such as amino acids or sugars) that are frequently present in high concentrations to stabilize mAbs …”

Design, Synthesis, Spectroscopic Characterisation and In Vitro Cytostatic Evaluation of Novel Bis(coumarin-1,2,3-triazolyl)benzenes and Hybrid Coumarin-1,2,3-triazolyl-aryl Derivatives

“…In addition to the compounds being potentially biologically active, fluorescence was observed with some of them, making them potentially suitable for application in fluorescence bioimaging. Coumarins are well-known fluorophores in labelling of biomolecules [27] because of the relatively large Stokes shift and high quantum yields, while in combination with 1,2,3-triazoles, new opportunities are opening up to investigate their potential as fluorescent probes for detecting biologically and environmentally important metal cations [28,29], anions [30] and biomolecules [31]. Therefore, the antiproliferative activity and basic photophysical properties of these newly prepared hybrids has been examined.…”

New Red-Shifted 4-Styrylcoumarin Derivatives as Potential Fluorescent Labels for Biomolecules

“…Cellular biology, medicine, pharmacy and environmental sciences require highly sensitive analytical techniques to track and detect nucleic acids, oligonucleotides, antibodies, amino acids, proteins, lipids, carbohydrates, and other biomolecules [ 1 , 2 , 3 , 4 , 5 , 6 ]. Most available techniques generally require labelling with a sensor, as fluorescent labels [ 7 , 8 ] electrochemical sensors [ 9 ], photochromic compounds [ 10 ], photo switchable biomaterials [ 11 ], colorimetric biosensors [ 12 ], radioactive tracers [ 13 ] and isotope markers [ 14 ].…”