Folic acid complexes with human and bovine serum albumins

• Published in: Food chemistry 2011-12, Vol.129 (3), p.1148-1155
• Main Authors: Bourassa, P., Hasni, I., Tajmir-Riahi, H.A.
• Format: Article
• Language: English
• Subjects: acid value; amino acids; binding sites; Biological and medical sciences; bovine serum albumin; BSA; Conformation; Folic acid; Food industries; Fourier transform infrared spectroscopy; Fundamental and applied biological sciences. Psychology; HSA; humans; hydrogen bonding; Milk and cheese industries. Ice creams; Modelling; molecular models; protein secondary structure; Spectroscopy; transport proteins; ultraviolet-visible spectroscopy; Vitamin B
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2011.05.094

► Folic acid binds HSA and BSA via both hydrophobic and hydrophilic contacts. ► Stronger interaction was observed with BSA than HSA. ► Major alterations of protein conformation were observed in the presence of folic acid due to a partial protein unfolding. ► Serum albumins can act as carrier proteins to transport folic acid to target molecules. The interaction of folic acid with human serum (HSA) and bovine serum albumins (BSA) at physiological conditions, using constant protein concentration and various folic acid contents was investigated. FTIR, UV–visible and fluorescence spectroscopic methods as well as molecular modelling were used to analyse folic acid binding sites, the binding constant and the effect on HSA and BSA stability and conformations. Structural analysis showed that folic acid binds HSA and BSA via both hydrophilic and hydrophobic contacts with overall binding constants of Kfolic acid–HSA=8.1 (±0.5)×104M−1 and Kfolic acid–BSA=1.0 (±0.3)×105M−1. The number of bound acid molecules per protein was 1.7 (±0.4) for HSA and 1.5 (±0.3) for BSA complexes. Molecular modelling showed participation of several amino acids in folic acid–protein complexes stabilised by hydrogen bonding network. Folic acid complexation altered protein secondary structure by major reduction of α-helix from 59% (free HSA) to 35% (acid-complex) and 62% (free BSA) to 25% (acid-complex) with an increase in random coil, turn and β-sheet structures indicating protein unfolding. The results suggest that serum albumins might act as carrier proteins for folic acid in delivering it to target molecules.