Photoclickable Dendritic Molecular Glue: Noncovalent-to-Covalent
Photochemical Transformation of Protein Hybrids
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Abstract
A water-soluble dendron
with a fluorescein isothiocyanate (FITC)
fluorescent label and bearing nine pendant guanidinium ion (Gu<sup>+</sup>)/benzophenone (BP) pairs at its periphery (Glue<sup>BP</sup>-FITC) serves as a “photoclickable molecular glue”.
By multivalent salt-bridge formation between Gu<sup>+</sup> ions and
oxyanions, Glue<sup>BP</sup>-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”