Title : Interaction of anticancer drug gemcitabine with human plasma protein: Experimental and computational analysis
The interaction of common anticancer drug gemcitabine with human serum albumin (HSA), an important plasma protein, has been studied in details. A slight hyperchromic shift in the difference UV absorption spectra of HSA on the addition of gemcitabine gave a primary idea of the possible complex formation between them. Inner filter effect played an important role in the observed fluorescence quenching of HSA by gemcitabine that can be understood by comparing the observed and corrected fluorescence intensities obtained at λex = 280 nm and 295 nm. There was a large difference between the observed quenching at these two excitation wavelengths that becomes negligible after the correction of inner filter effect (IFE). Quenching of intrinsic fluorescence of HSA by gemcitabine increases with increase in temperature which suggested the existence of dynamic type of quenching. Overall, gemcitabine shows weak to fair interaction with HSA with binding ratio of around 1. Secondary structural analysis showed that low concentrations of gemcitabine didn’t affect the native structure of protein, however, higher concentrations affects it slightly with partial unfolding. Molecular docking simulation was also performed to understand the mode of binding as well as the most preferred binding site of gemcitabine into HSA.
- From this research, the effect of IFE, a known phenomenon in the fluorescence spectroscopy and causes the fluorescence decrement of the fluorophore by absorbing some of the radiations falls on the sample, on the fluorescence quenching of a protein by a ligand could be understood if one is considering the different excitation wavelengths for the study. The observed quenching will be dependent on the extent of the absorption of the light at a particular wavelength. Thus, if the study would be carried out at two excitation wavelengths which have different absorbances, the quenching will be different in each case, however, correction of the IFE could give the clear picture.
- The binding extent of a pharmacological active compound with plasma proteins like serum albumin is an important factor in understanding its therapeutic action. The substances which bind strongly take more time to release from the binding proteins while very weak or no binding may cause the drug not to reach at its site of action. From this study it can be seen that serum albumin are good carrier for the gemcitabine.
- This research is helpful in teaching as well as in research. In the teaching the inner filter effect could be demonstrated to the students and how it affects the actual data at various wavelengths could also be taught. In fluorescence spectroscopy related research, the understanding of the IFE and its correction are necessary.