Effect of local anesthetic drug procaine hydrochloride on the conformational stability of bovine hemoglobin: Multi-spectroscopic and computational approaches

Abstract

The interaction between bovine hemoglobin (BHb) and local anesthetic drug procaine hydrochloride (PCH) was examined by spectroscopic and computational studies. Intrinsic fluorescence analysis explored the ground-state complex formation in the binding of PCH with BHb through static quenching mechanism. The binding constants (K_b) are 29.38 × 10³, 22.54 × 10³ and 17.99 × 10³ M⁻¹ at 288, 298 and 308 K, respectively, and the ratio of BHb:PCH was 1:1 in the interaction mechanism of PCH and BHb. The acquired thermodynamic parameters (ΔH⁰, ΔG⁰ and ΔS⁰) demonstrated that interaction mechanism is spontaneous and enthalpy driven. The van der Waals forces and hydrogen bonding have been played a predominant role in the binding mechanism. The UV-vis spectroscopy validates the ground-state complexation between PCH and BHb and the binding constant (K_b) has been evaluated utilizing Benesi-Hildebrand equation. Fluorescence resonance energy transfer (FRET) results have demonstrated that the distance between donor (BHb) and acceptor (PCH) is very short (2.34 nm) suggesting a significant probability to energy transfer from BHb to PCH. Synchronous fluorescence results revealed that the alteration in the micro-environment of Tyrosine (Tyr) is more than tryptophan (Trp) residues suggesting that PCH molecule is close to Tyr residue. The secondary structure alterations were confirmed by CD, 3-D fluorescence and FT-IR spectroscopic measurements. Moreover, computational analyses further corroborated that PCH molecules are closer to Tyr residues as compared to Trp residues of BHb during the interaction process. The BHb-PCH complexes may contribute to a deeper understanding of the metabolism of drug, blood circulation process and may help to illustrate the relationship between functions and structure of BHb.

Communicated by Ramaswamy H. Sarma

Keywords:

• Procaine Hydrochloride (PCH)
• Bovine Hemoglobin (BHb)
• binding constant (K_b)
• fluorescence resonance energy transfer (FRET)
• molecular docking
• DFT calculations

Disclosure statement

No potential conflict of interest was reported by the author(s).

Acknowledgements

The authors are highly thankful to the Chairman, Department of Chemistry, A.M.U. Aligarh for providing the necessary facilities to carry out this research work. The PURSE and FIST grants from DST and SAP DRS-II grant from UGC are acknowledged. The authors express his sincere gratitude to University Grants Commission (UGC), New Delhi, for providing financial support.