Aromatic hydrazine-based fluorophores: Synthesis, spectroscopy and bioapplications

Abstract

In recent years, fluorescent probes have been one of the most essential tools for studying biological events in in solution, living cells, tissues and animals. Although there are many fluorophores commercially available, there is still a need of precisely designed fluorescent probes to understand the dynamics and function of biological systems at a specific site. Small molecule fluorescent probes can be designed to be used selective bioorthogonal chemistries to address the specificity in cells and in more complex biological environments. These probes offer powerful options to study functions of proteins in their native environments with minimal perturbation to living systems. The design of suitable fluorophores for bioorthogonal labeling requires consideration of both the reactivity of the functional group and the spectroscopic features of the fluorophore. Here, we discuss several aromatic hydrazine-containing fluorophores as synthetic targets, which are designed to react with an aldehyde or ketone introduced into a biomolecule at or near physiological conditions to form a stable product, a hydrazone. In these molecules, hydrazone formation alters the optical properties of the fluorophore, normally resulting in a significant increase in emission quantum yield upon covalent bond formation. In some cases, a red shift of the absorption and emission maxima is also observed when hydrazone forms. Background fluorescence due to unreacted initial fluorophore is low, which is a very useful feature for fluorescent imaging of labeled proteins in biological systems. Thus, this chapter will outline different strategies for synthesis of aromatic hydrazine-based fluorophores, spectroscopic properties and stability limitations of the probes that lead to possible applicability for biological systems.© 2013 Nova Science Publishers, Inc. All rights reserved.