Guanidinium-Modified Phthalocyanines as High-Affinity G-Quadruplex Fluorescent Probes and Transcriptional Regulators


  • This work was supported by the Swiss National Science Foundation (grant no. 116868), the Dr. Helmut Legerlotz Stiftung, and the University of Zürich. We thank the University of Zürich Center for Microscopy and the Institute of Molecular Cancer Research, as well as Giulio Fiaschetti and Prof. Alexandre Arcaro for technical assistance.


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Fluorescence is ON and transcriptional control is OFF when the guanidinium-modified zinc phthalocyanine Zn-DIGP binds a G-quadruplex DNA from the c-Myc promoter. With an equilibrium dissociation constant Kd of less than 2 nM, this interaction is the strongest binding interaction between a G-quadruplex structure and a small molecule reported to date.