Abstract
The emerging inverse electron demand Diels-Alder (IEDDA) reaction stands out from other bioorthogonal reactions by virtue of its unmatchable kinetics, excellent orthogonality and biocompatibility. With the recent discovery of novel dienophiles and optimal tetrazine coupling partners, attention has now been turned to the use of IEDDA approaches in basic biology, imaging and therapeutics. Here we review this bioorthogonal reaction and its promising applications for live cell and animal studies. We first discuss the key factors that contribute to the fast IEDDA kinetics and describe the most recent advances in the synthesis of tetrazine and dienophile coupling partners. Both coupling partners have been incorporated into proteins for tracking and imaging by use of fluorogenic tetrazines that become strongly fluorescent upon reaction. Selected notable examples of such applications are presented. The exceptional fast kinetics of this catalyst-free reaction, even using low concentrations of coupling partners, make it amenable for in vivo radiolabelling using pretargeting methodologies, which are also discussed. Finally, IEDDA reactions have recently found use in bioorthogonal decaging to activate proteins or drugs in gain-of-function strategies. We conclude by showing applications of the IEDDA reaction in the construction of biomaterials that are used for drug delivery and multimodal imaging, among others. The use and utility of the IEDDA reaction is interdisciplinary and promises to revolutionize chemical biology, radiochemistry and materials science.
Highlights
Chemical site-selective protein modification has become increasingly popular for probing and controlling protein functions in vitro and in living systems
A related approach by Royzen et al showed that a cytidine triphosphate (CTP) analogue with a TCO group at the 5-position of the nucleobase is recognized by the T7 RNA polymerase, and is internally and site- incorporated in a RNA strand.[183]
BCNSia was metabolically incorporated into zebrafish embryos by systemic microinjection of BCNSia followed by reaction with a fluorogenic tetrazine probe, resulting in a robust BCNSia-dependent fluorescence of interior cells with minimal background (Fig. 32)
Summary
Chemical site-selective protein modification has become increasingly popular for probing and controlling protein functions in vitro and in living systems. Colloids and Interfaces, Germany, and the ETH Zurich, Switzerland, and worked as a Group Leader at Alfama Lda in Portugal He started his independent research career in 2013, and his research group interests focus on the development of site-selective chemical protein modification for basic biology and drug development. The IEDDA reaction has emerged as an important tool for probing the mechanism and function of bioactive molecules in living systems For such applications, the rate constant is of critical importance as very fast kinetics are required for labelling cellular processes that occur on biological time scales. We draw conclusions and present a brief prospect of the role of IEDDA reactions in the field of bioorthogonal chemistry
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