Structural and thermal impacts of phosalone binding to human serum albumin: perspectives from molecular modeling and spectroscopic methods

Phosalone (Pln) is an organophosphate pesticide that poses potential risks to human health due to its widespread use. We investigated the interaction between Pln and human serum albumin (HSA) using molecular modeling and multi-spectral methods. Molecular docking studies identified the binding site and key residues involved in the interaction with Pln. Additionally, molecular dynamics (MD) simulations revealed that the average root mean square deviation (RMSD) of the complex exceeded that of the free HSA system, consistent with thermal stability studies indicating a decrease in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>T</mml:mi></mml:mrow><mml:mrow><mml:mi>m</mml:mi></mml:mrow></mml:msub><mml:mtext>.</mml:mtext></mml:math> Ultraviolet-visible (UV-vis) spectroscopic analyses confirmed the formation of a HSA-Pln complex. Extrinsic fluorescence analysis, utilizing the fluorescent dye 8-Anilinonaphthalene-1-sulfonic acid (ANS), demonstrated that the addition of Pln quenches the fluorescence of the HSA-ANS complex through static quenching. The Stern-Volmer constants (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>K</mml:mi></mml:mrow><mml:mrow><mml:mtext>sv</mml:mtext></mml:mrow></mml:msub></mml:math>) for the interaction between Pln and HSA-ANS were determined to be 47.99, 31.67, and 27.55 (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow><mml:mi>M</mml:mi></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:math>) at temperatures of 298, 308, and 318 K, respectively. The thermodynamic parameters were calculated as <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow><mml:mo>Δ</mml:mo><mml:mi>S</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msup></mml:math> = -39.88 (J. <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow><mml:mtext>mol</mml:mtext></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>K</mml:mi></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup><mml:mo>)</mml:mo></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow><mml:mo>Δ</mml:mo><mml:mi>H</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msup></mml:math>= -22.25 (kJ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow><mml:mtext>mol</mml:mtext></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:math>). These thermodynamic investigations revealed that hydrogen bonds and van der Waals forces are the primary interactions responsible for the formation of the (ANS-HSA)-Pln complex. Furthermore, FT-IR spectroscopy indicated that Pln induces a conformational change in HSA, suggesting its potential to cause structural damage. These findings provide valuable insights into the interaction mechanism between Pln and HSA, enhancing our understanding of the impact of pesticides on proteins and overall health.