Human c‐KIT oncogene is known to regulate cell growth and proliferation, and thus, acts as a probable target in the treatment of gastrointestinal tumors (GIST). To identify small molecule ligands which can specifically bind with the G‐quadruplex (G4) in the c‐KIT promoter region as potential antitumor agents, we propose the combination of electrospray ionization–mass spectrometry (ESI‐MS), capillary electrophoresis frontal analysis (CE‐FA), and Taylor dispersion analysis (TDA) to accurately investigate the G4/ligands binding properties. First, ESI–MS was used for initial screening of natural products (NPs). CE‐FA was then used to calculate specific binding constants and the stoichiometry of the native state binding pair in solution. Next, TDA, a micro‐capillary flow technique was used to examine the effect of the ligand binding on the diffusivity and particle size of the c‐KIT G4. Two of the screened NPs, scopolamine butylbromide (L1) and isorhamnetin‐3‐O‐neohesperidoside (L3), were found to specifically bind to the c‐KIT G4 with binding constants of around 104 M–1 and 1:1 stoichiometry in a free solution. TDA data showed that ligand binding (both L1 and L3) induced the c‐KIT strands to fold into a tightly structured G4 with a decreased hydrodynamic radius. These ligands have the potential to be drug candidates for the regulation of c‐KIT gene transcription by stabilizing the G4 structure. This methodology not only increased the speed of analysis but also improved its accuracy and specificity compared with the conventional binding approaches.
The thermodynamic properties of molecular recognition in host-guest inclusion complexes can be studied by Taylor dispersion analysis (TDA). Host-guest inclusion complexes have modest size, and it is possible to get convergent results fast, achieving greater certainty for the obtained thermodynamic properties.Cyclodextrins (CDs) and their derivatives can be used as drug carriers that can boost stability, solubility, and bioavailability of physiologically active substances.A simple and effective approach for assessing the binding properties of CD complexes that are critical in the early stages of drug and formulation development is needed to fully understand the process of CD and guest molecules' complex formation. In this work, TDA was successfully used to rapidly determine interaction parameters, including binding constant and stoichiometry, between β-CD and folic acid (FA) along with the diffusivities of the free FA and its complex with β-CD. Additionally, the FA diffusion coefficient obtained by TDA was compared to the results previously obtained by nuclear magnetic resonance. Affinity capillary electrophoresis (ACE) was also used to compare the binding constants obtained by different methods. The results showed that the binding constants obtained by ACE were somewhat lower than those obtained by the two TDA procedures.
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