I worked on ligand -Nucleic acid (DNA) interaction for this I have done UV-Visible Spectroscopy of my synthetic chemical compound (Ligand) with the DNA. I did titration of the ligand with increasing concentration of DNA. Data shows (in attachment) the highest absorbance/Peak around 463 nm or 413 nm in the case of ligand only (A-0). In contrast, when the DNA was titrated with increasing concentration from A1 to A5, the intensity of peat at 463 nm and 413 nm decreased while the peak increased around 260 nm. However, no absorbing peak was found at 260 nm in the case of ligand only. What could be the significance of this blue shift and what could be the possibility of decreasing peak intensity at 463 and 413 nm? Does this shift indicate the ligand-DNA interaction?

In another experiment, I titrated different conformation of DNA with the same compound in which only the blue shift was observed, however, no change was found at 463 and 413 nm. Please explain this difference also. Does the ligand-DNA interaction happen in this condition also?

in all experiments, the baseline was subtracted and prior to the addition of DNA in increasing concentration I added a corresponding buffer to the ligand also and peak overlap to A-0 (ligand only peak)

Please find the attached graph for your kind reference.