VEGF G-dörtlü yapisinin doksorobisin ile etkileşimi ve altın nanoparçacık-azasiyanin floresans probu ile tespiti

Vascular endothelial growth factor (VEGF) is a signal protein known to be regulating angiogenesis and it is up-regulated in many tumors. It had been reported that VEGF promoter region Pu22 can form a stable parallel G-quadruplex (G4) structure. G4 structures are formed in guanine rich nucleic acid sequences and they have gained considerable importance due to their involvement in vital cellular functions such as transcription. Concurrently, detecting and targeting G4s became an emerging field in drug design research. Within the scope of this thesis, in the first part, the interactions between the anti-cancer agent Doxorubicin (Dox) and the G4 structures formed by the VEGF promoter region Pu22 and Pu22T12T13 were investigated via UV-vis absorption, Circular Dichroism (CD) and Fluorescence spectroscopy experiments. Afterwards, the affinity of Dox towards different nucleic acid structures including several biologically important G4 structures was studied with competition dialysis experiments. Our investigations demonstrated that Dox had significant affinity to the G4 formed by the VEGF promoter region Pu22 and stabilizing the G4 structure. The competition dialysis results revealed that the affinity of Dox to Pu22 was higher than its affinity to other G4 forming sequences as BCL-2, C-myc, Her-2, K-ras and Human telomeric repeat. More importantly, our results revealed that Dox's affinity to Pu22 was comparable to its affinity to double stranded DNA, which might imply a new plausible action mechanism for Dox in-vivo. In the second part, a rapid, facile and sensitive off-on-off gold nanoparticle-Azacyanine5 (AuNPs-Aza5) fluorescence probe for the detection of G4 structures was developed. The proposed AuNPs-Aza5 fluorescence probe was characterized with UV-vis absorption, CD and Fluorescence spectroscopy, as well as Transmittance Electron Microscopy (TEM) and Dynamic Light Scattering (DLS) techniques. This sensing platform selectively responded to G4 structures including VEGF-Pu22, K-ras, C-myc and BCL-2, while exhibiting no similar response to the other secondary structures, such as single, double and triple stranded structures. VEGF promoter region Pu22 was chosen as the model G4 to investigate the analytical merits of the study and the off-on-off AuNPs-Aza5 probe displayed linear response to the model G4 between a concentration range of 0.032-0.347 M with a detection limit of 12.66 nM.