Interactions of lysozyme with hydrophobic and hydrophilic non-steroidal anti-inflammatory drugs: Spectroscopic and molecular docking analyses

Non-covalent molecular interaction of lysozyme with two very important non-steroidal anti-inflammatory drugs (paracetamol or acetaminophen and ibuprofen) were studied using fluorescence, UV-visible and circular dichroism spectroscopies. In addition, the interaction was also studied using molecular docking simulations. Changes in the difference UV-visible absorption spectra of lysozyme in presence of the drugs were the indication of the complex formation between drug and the protein. Fluorescence spectroscopic observations showed that the fluorescence intensity of lysozyme initially increased on the addition of paracetamol then start to decrease at higher concentrations of the latter, however, a constant increase in the fluorescence intensity of the protein was observed on the addition of ibuprofen. The irregular pattern observed in case of paracetamol was ascribed to the inner filter effect, which after correction turned into the uniform fluorescence enhancement. Both drugs have shown a good interaction with lysozyme, although, the interaction of ibuprofen was slightly stronger than the one with paracetamol. The binding of paracetamol with lysozyme was taken place with contribution of both hydrophobic forces as well as hydrogen bodings whereas in lysozyme-ibuprofen case, hydrophobic interactions were the dominating forces. Paracetamol as well as ibuprofen induced the secondary structure of lysozyme by increasing the alpha-helicity of the protein. Results obtained through molecular docking were in excellent agreement with the one obtained through experimental studies.