@article {YANG2020120885,
	title = {Characterization of interaction between Bcl-2 oncogene promoter I-Motif DNA and flavonoids using electrospray ionization mass spectrometry and pressure-assisted capillary electrophoresis frontal analysis},
	journal = {Talanta},
	year = {2020},
	pages = {120885},
	abstract = {B-cell lymphoma 2 (Bcl-2) is an antiapoptotic protein which is believed to be a triggering factor in developing human tumors. The Bcl-2 C-rich promoter element has been shown to form the i-motif (IM) via cytosine-cytosine (C{\textendash}C+) base pair building blocks, which can be targeted through the binding of ligands associated with Bcl-2 expression modulation. In this work, we monitored IM development and thermodynamic stability within the Bcl-2 promoter via circular dichroism (CD) spectroscopy and electrospray ionization mass spectrometry (ESI-MS). The results demonstrated that at an acidic pH, as well as in a crowded molecular environment, the Bcl-2 promoter element predominantly exists in a stable intramolecular IM folded state. We further explored the potential of targeting of the Bcl-2 IM to increase chemotherapeutic efficacy. We first used a rapid ESI-MS screening assay to identify possible ligands, finding that three natural flavonoids (P1, P5 and P6) exhibited a clear affinity for IM binding at 1:1 stoichiometry. Relative to P6, P1 and P5 were expected to form the more stable complexes with the Bcl-2 IM in gas phase according to MS/MS data. We further used ESI-MS and pressure-assisted capillary electrophoresis frontal analysis (PACE-FA) to assess the binding constants for these flavonoids in gas and liquid phases, respectively, with the latter considering both specific and non-specific binding. We found P5 and P6 to specifically bind the Bcl-2 IM with binding constants of \~{}104 M-1. P1 binding was confirmed to be due to both specific and nonspecific interactions, and the specific binding constant (8.67 {\texttimes} 103 M-1) was found much less significant than the binding constant in gas phase. Taken all these observations into consideration, the specific binding of selected flavonoids to the Bcl-2 IM may prove to be a potential ligand for modulating Bcl-2 gene expression.},
	keywords = {Bcl-2 oncogene, circular dichroism, Electrospray ionization mass spectrometry, Flavonoids, I-motif, Pressure-assisted capillary electrophoresis frontal analysis},
	issn = {0039-9140},
	doi = {https://doi.org/10.1016/j.talanta.2020.120885},
	url = {http://www.sciencedirect.com/science/article/pii/S0039914020301764},
	author = {Yang Yang and Hengqing Fu and Cheng Qian and Huihui Li and David D.Y. Chen}
}
