Skip to main content
Article
Cucurbit[7]uril-Tetramethylrhodamine Conjugate for Direct Sensing and Cellular Imaging
Journal of the American Chemical Society
  • Andrew T Bockus, Trinity University
  • Lauren C Smith, Trinity University
  • Amy G Grice, Trinity University
  • Omar A Ali, Trinity University
  • Carolyn C Young, Trinity University
  • William Mobley, Trinity University
  • Ashley Leek, Trinity University
  • James Lewis Roberts, Trinity University
  • Brittany Vinciguerra
  • Lyle D Isaacs
  • Adam R Urbach, Trinity University
Document Type
Article
Publication Date
12-1-2016
Abstract

This paper describes the design and synthesis of a conjugate (Q7R) comprising the synthetic host cucurbit[7]uril (Q7) linked to the fluorescent dye tetramethylrhodamine (TMR), and the characterization of its optical and guest-binding properties as well as its cellular uptake. Q7R was synthesized in two steps from monofunctionalized azidobutyl-Q7 and NHS-activated TMR. The fluorescence of Q7R is quenched upon guest binding, and this observable was used to determine equilibrium dissociation constant (Kd) values. Unexpectedly, the Kd values for guests binding to Q7R and to unmodified Q7 were essentially identical. Therefore, Q7R can directly report binding to Q7 without an energetic penalty due to the conjugated fluorophore. This result demonstrates a potentially general strategy for the design of single-component host-indicator conjugates that respond sensitively to analytes without perturbing the binding properties of the host. The unique properties of Q7R enabled measurement of Kd values across 3 orders of magnitude and at concentrations as low as 0.7 nM. This result is particularly relevant given the unmatched range of guests and binding affinities demonstrated for Q7. Confocal fluorescence microscopy of live and fixed HT22 neurons revealed the cellular uptake of Q7R and its punctate localization in the cytoplasm. Q7R did not alter cell growth at concentrations up to 2.2 μM over 4 days. These experiments demonstrate the feasibility of Q7R as a direct sensor for guest binding and as a cell-permeable compound for imaging applications. © 2016 American Chemical Society.

DOI
10.1021/jacs.6b11140
Publisher
American Chemical Society
Citation Information
Bockus, A. T., Smith, L. C., Grice, A. G., Ali, O. A., Young, C. C., Mobley, W., . . . Urbach, A. R. (2016). Cucurbit[7]uril-tetramethylrhodamine conjugate for direct sensing and cellular imaging. Journal of the American Chemical Society, 138(50), 16549-16552. https://doi.org/10.1021/jacs.6b11140