Research Article

Interactions Evaluation of 5-Fluorouracil Drug with Amino Acids Least Abundance in Protein

Abstract

In the beginning, the 5-FU drug (0.1 mM) and amino acids (tryptophan and cysteine; 1.0 mM) were prepared separately in potassium phosphate buffer at a physiological conditions (pH=7.4 and T=37◦C). The acidity function and temperature of prepared solutions were checking continuously, and the spectral measurements were achieved for these solutions individually. The experimental spectra of reactants (5-FU and amino acids) at pH=7.4 and T=37◦C were showed identical values for the standards (λmax = 266; 280, 190 nm for 5-FU, tryptophan and cysteine respectively). Then, the spectral lines of molecular complexes were followed as first order interactions for tryptophan (at 277 nm; k f =30.48×10−3 min–1; t1/2= 17.67 min) and cysteine (at 264 nm; k f =29.43×10−3 min–1; t1/2= 22.28 min). The mathematical calculations showed that, the interaction of cysteine with 5-FU was proceed in forward direction simply by regularity mode with a high stability (Keq=17.67). While, the molecular complex of tryptophan was behaved as a complicated reversible interaction by manner less stability than in cysteine (with; Keq=3.49). The non essential peaks of amino acids interactions (at 287 nm in tryptophan and 320 nm in cysteine) were explained as aggregation for transient molecular complexes, or it may be represent different interactions for the more one kind of reactants. The molecular complexes interactions (5-FU drug with tryptophan and cysteine) were occurred spontaneously, with free energies favourable for a physical forces (Van Der Waals forces) or hydrogen bonding (ΔG◦ < 10 kJ/mol) by a high chemical affinity.

Authors affiliation:

Razzaq Abd Al-Zahra Ibrahim (ORCID): Department of Biology, Science Faculty University of Kufa, Iraq.

How To Cite: R.A.A. Ibrahim. Interactions Evaluation of 5-Fluorouracil Drug with Amino Acids Least Abundance in Protein. Journal of Biomedicine and Biosensors, 6(3):76–83, 2026. https://doi.org/10.58613/jbb639