1HNMR study of methotrexate–serum albumin (MTX–SA) binding in rheumatoid arthritis

Rheumatoid arthritis (RA) is an immunologically depended disease. It is characterized by a chronic, progressive inflammatory process. Methotrexate (4-amino-10-methylfolic acid, MTX) is the modifying drug used to treat RA.The aim of the presented studies is to determine the low affinity binding site of MTX in bovine (BSA) and human (HSA) serum albumin with the use of proton nuclear magnetic resonance (1HNMR) spectroscopy. The analysis of 1HNMR spectra of MTX in the presence of serum albumin (SA) allows us to observe the interactions between aromatic rings of the drug and the rings of amino acids located in the hydrophobic subdomains of the protein. On the basis of the chemical shifts σ [ppm] and the relaxation times T1 [s] of drug protons the hydrophobic interaction between MTX–SA and the stoichiometric molar ratio of the complex was evaluated.This work is a part of a spectroscopic study on MTX–SA interactions [A. Sułkowska, M. Maciążek, J. Równicka, B. Bojko, D. Pentak, W.W. Sułkowski, J. Mol. Struct. 834–836 (2007) 162–169].