Bioorthogonal reactions for coupling functional chemical entities in vitro and in vivo are of great interest in life sciences and medicine.  MBMR Biolabs focuses on the the development of new applications for the inverse-electron-demand Diels-Alder cycloadditon (also called tetrazine cycloaddition) – a copper-free  click chemistry reaction, developed in the laboratory of Professor Joseph M. Fox at University of Delaware.


The inverse-electron-demand Diels-Alder cycloaddition between trans-cyclooctenes and tetrazines is biocompatible and exceptionally fast[1].  The rate for Diels-Alder cycloaddition, reported to be as high as 2000 M-1 s-1, is on par with the rate for canonical copper-catalyzed azide-alkyne conjugation.  However, Diels Alder reaction does not exhibit the accompanying cell toxicity that prevents usage of those reagents in vivo or inside living cells in a variety of applications. 


Due to their small size and advantageous photophysical properties relative to fluorescent proteins, chemical fluorophores have the potential to be very useful for live cell imaging. Here we are presenting a variety of reagents that have been described in literature as building blocks for site-specific protein labeling[2], specific intracellular protein labeling,[3] lipid labeling, as well as tumor imaging[4] in live animals.  We are currently working on the development of more kits to be used both with in vitro and in vivo applications. 

[1] Blackman ML, Royzen, M, Fox JM.  Tetrazine ligation: fast bioconjugation based on inverse-electron-demand Dield-Alder reactivityJ Am Chem Soc 2008, 130: 13518-13519; Taylor MT, Blackman ML, Dmitrenko O, Fox JM: Design and synthesis of highly reactive dieophiles for the tetrazine-trans-cyclooctene ligationJ Am Chem Soc 2011, 133: 9646-9649.

[2] Seitchik JL, Peeler JC, Taylor MT, Blackman ML, Rhoads TW, Cooler RB, Refakis C, Fox JM, Mehl RA: Genetically encoded tetrazine amino acid directs rapid site-specific in vivo bioorthogonal ligation with trans-cyclooctenes.  J Am Chem Soc 2012, 134: 2898-2901; Lang K, Davis L, Wallace S, Mahesh M, Cox DJ, Blackman ML, Fox JM, Chin JW: Genetic encoding of bicyclononynes and trans-cyclooctenes for site-specific protein labeling in vitro and in live mammalian cells via rapid fluorogenic Diels-Alder reactions.  J Am Chem Soc 2012, 134:10317-10320.

[3] Liu DS, Tangpeerachaikul A, Selvaraj R, Taylor MT, Fox JM, Ting AY: Diels-Alder cycloaddition for fluorophore targeting to specific proteins inside living cells.  J Am Chem Soc 2011, 134: 792-795; Devaraj NK, Upadhyay R, Haun JB, Hilderbrand SA, Weissleder R: Fast and sensitive pretargeted labeling of cancer cells through a tetrazine/trans-cyclooctene cycloaddition.  Angew Chem Int Ed 2009, 48: 7013-7016.

[4] Rossin R, Renart Verkerk P, van den Bosch SM, Vulders RCM, Verel I, Lub J, Robillard MS: In vivo chemistry for pretargeted tumor imaging in live mice.  Angew Chem Int Ed 2010, 49:3375-3378; Li Z, Cai H, Hassink M, Blackman ML, Brown RCD, Conti PS, Fox JM: Tetrazine-trans-cyclooctene ligation for the rapid construction o F-18 labeled probes.  Chem Commun 2010, 46:8043-8045.