Vinyl chloride, trichloroethylene, and carbon tetrachloride showed irreversible binding of metabolites to tissue proteins, mainly of the liver.
Subsequently, the binding of TMPyP4 tetrachloride to human telomeric RNA G-quadruplexes was studied with ESI-TOF-MS technique.
In addition, the binding of TMPyP4 tetrachloride with both human telomeric DNA and RNA G-quadruplexes was also quantitatively carried out by ESI-TOF-MS analysis.
As shown in Fig. 3, TMPyP4 tetrachloride displayed a relatively less binding affinity than that of TMPyP4 tetratosylate, which was regarded to be ascribable to the contribution of tosyl anion's binding to DNA G-quadruplex.
Moreover, the binding capacity of TMPyP4 tetrachloride with human telomeric RNA G-quadruplex was one order of magnitude stronger than that with DNA counterpart.
This was verified by the results of less binding affinity of TMPyP4 tetrachloride with DNA G-quadruplex obtained from ESI-TOF-MS measurement, and of 2.27 °C less thermal stabilization of TMPyP4 tetrachloride for DNA G-quadruplex, compared to its tetratosylate under the same conditions.
The binding study of TMPyP4 tetrachloride to human telomeric DNA G-quadruplex was subsequently carried out under the same ESI-TOF-MS condition as that for TMPyP4 tetratosylate (Fig. 1c).
In addition, G-quadruplex binding activity of TMPyP4 tetrachloride was also quantitatively compared between two types of human telomeric G-quadruplexes, i.e., DNA and its RNA anologue, for a purpose of exploring its binding specificity with nucleic acid G-quadruplexes.
EGF: epidermal growth factor; EGFR: epidermal growth factor receptor; HCC: hepatocellular carcinoma; HSC: hepatic stellate cell; CCl4: carbon tetrachloride; TGF: transforming growth factor; HB-EGF: heparin-binding EGF-like growth factor; AREG: amphiregulin; GFAP: glial fibrillary acidic protein; EPC: endothelial progenitor cell The authors declare that they have no competing interests.
The binding constants (K1) and (K2) of TMPyP4 tetrachloride with DNA G-quadruplex derived from ESI-TOF-MS analysis were almost consistent with those obtained by solution method of ITC experiments [ 40], indicating that ESI-TOF-MS analysis is an alternative method to reliably measure G-quadruplex binding constant.
