Fluorescent labeling techniques in biomolecules: a flashback

Recent advancements in analytical methods relating organic chemistry, molecular biology, spectroscopy, engineering, and chemical biology have provided powerful tools to explore different selective fluorescent labeling techniques for analyzing molecular events in cells. New fluorescent labeling techniques have been developed and improvised depending on requirements like non-specificity, selectivity, small size, and of course, high yield. Along with synthesized small fluorophores that are used mostly for chemical labeling, fluorescent proteins such as green fluorescent protein (GFP) and its variants are used to label living cells genetically, both in vivo and in vitro. Fluorescent labeling has been extended over a large area of interdisciplinary research to visualize the functions and conditions of molecules using lower concentrations of the fluorescent material. Considering the wide applications of fluorescent techniques in various fields, the basic principles of different fluorescent labeling techniques relevant to chemistry and biology are discussed in this review.