Photoclickable dendritic molecular glue: Noncovalent-to-covalent photochemical transformation of protein hybrids

Abstract

A water-soluble dendron with a fluorescein isothiocyanate (FITC) fluorescent label and bearing nine pendant guanidinium ion (Gu +)/benzophenone (BP) pairs at its periphery (GlueBP-FITC) serves as a "photoclickable molecular glue". By multivalent salt-bridge formation between Gu+ ions and oxyanions, Glue BP-FITC temporarily adheres to a kinesin/microtubule hybrid. Upon subsequent exposure to UV light, this noncovalent binding is made permanent via a cross-linking reaction mediated by carbon radicals derived from the photoexcited BP units. This temporal-to-permanent transformation by light occurs quickly and efficiently in this preorganized state, allowing the movements of microtubules on a kinesin-coated glass plate to be photochemically controlled. A fundamental difference between such temporal and permanent bindings was visualized by the use of "optical tweezers". © 2013 American Chemical Society.