INTERACTION OF DOPAMINE WITH DNA, DEPENDING ON THE IONIC STRENGTH OF THE SOLUTION: POTENTIAL APPLICATION IN SENSOR...

Dopamine is one of the most important neurotransmitters in the central nervous system. Along with other mediators, such as serotonin, noradrenaline, adrenaline, it enormously contributes to the human mental health. Any concentration alterations of dopamine in the brain result in devastating consequences, expressed as mental disorders, movement deviations, etc. From this point of view, it is crucial to make possible to determine the concentration of dopamine in the blood, and, with more probability, in the urine. Dopamine concentration monitoring may be possible by implementation to create dopamine-sensitive biosensors, where there should be an underlayer, interacting with and detecting dopamine. Nucleic acids, particularly, DNA can serve as sensitive biomolecules for dopamine-sensors.

In this work, the interaction of DNA with dopamine, depending on the ionic strength of the solution, has been studied, using the method of UV-melting and absorption spectroscopy. In the experiments calf thymus DNA, dopamine hydrochloride ("Sigma-Aldrich", USA), physiological solution were used. Concentrations of DNA and dopamine were determined spectrophotometrically, using the following values of the extinction coefficients: 260=6600 M-1cm-1 for DNA and 280=2200 M-1cm-1 for dopamine hydrochloride. The experiments were carried out at the ionic strengths of the solution 0.02 M and 0.01 M Na+. The medium pH was equal to 7.0.

For this aim, the interaction between dopamine and DNA, depending on the solution ionic strength, was explored to reveal whether there exists a binding or not. The results, obtained in this study, show that dopamine binds to DNA, at least, in two regions at low ionic strength of the solution and, at least, in three regions at high ionic strength of the solution. It was shown that DNA-dopamine complex melting curve is shifted toward high temperatures, as compared to that of DNA. It results in melting temperature increasing by more, than 3-4C, in high concentration ratios dopamine/DNA. Besides, the absorption spectra of DNA start decreasing, while titrating by dopamine. The binding constant of dopamine with DNA was calculated and it was shown that for the strong binding this parameter is 1.2105 M-1 and for weak binding - 2.3103 M-1. From the data, obtained in this work, one can conclude that DNA may be used as a possible sensitive biomolecule in the dopamine-sensors.