Abstract

As cytosine (Cyt)-rich sequences, MYC i-motifs can form special four-stranded structures by intercalation of two parallel Cyt rich duplexes with hemi-protonated Cyt-Cyt base pairs.1 They have been found to contribute greatly to tumorigenesis and are overexpressed in many different types of cancer cells.2 Despite of the biological importance, their photophysical properties have still poorly understood so far. Here, we carry out study on excited state dynamics of MYC0 i-motif, one of the MYC i-motifs, by using combined methods of steady state spectroscopy, femtosecond broadband time-resolved fluorescence (fs-TRF) and transient absorption (fs-TA). This study shows that besides localized ππ* state like that of monomeric bases, the excited state dynamics of MYC0 i-motif particularly consists of multiple low-lying charge transfer states that are induced within the in-plane hemi-protonated base pair. 

References

1. Gehring, K.; Leroy, J. L.; Gueron, M., Nature 1993, 363 (6429), 561-565.
2. Ahmadi, S. E.; Rahimi, S.; Zarandi, B.; Chegeni, R.; Safa, M., J. Hematol. Oncol. 2021, 14 (1), 1-121.

Acknowledgements

We highly appreciate financial support from the Research Grants Council of Hong Kong (15302319 and 15301721).