Study of the specific interaction between l-methionine chromatography support and nucleotides

The interaction of l-methionine-agarose with 5′-mononucleotide was investigated by saturation transfer difference (STD)-nuclear magnetic resonance (NMR) spectroscopy. Chromatographic experiments were also performed using homo-oligonucleotides of distinct molecular masses (1–30 nucleotides) to explore the effect of base hydrophobicity, temperature, pH and salt concentration on the retention of homo-oligonucleotides to l-methionine-agarose support. With STD-NMR, the results reveal that hydrophobic residues, such as the CH3 of thymine and adenine, can preferentially recognise the l-methionine side chain of the support. Also, 5′-TMP led to more contacts with the support, while 5′-UMP presented fewer STD contacts. For 5′-UMP, 5′-CMP and 5′-GMP, the main interaction with the support was through the sugar-phosphate backbone. Similar binding profiles were obtained using chromatographic experiments. Indeed, 5′-TMP had the highest retention time, followed by 5′-GMP, 3′-AMP, 5′-UMP and 5′-CMP. In general, the retention factor of homo-oligonucleotides was higher for ammonium sulphate concentration 1.5 M. For the polyT3–polyT30 series, the retention time increased by about three-fold, indicating that larger homo-oligonucleotides have more hydrophobic bases, thus enhancing contact with the l-methionine support. The temperature (5, 20 and 35 °C) did not influence homo-oligonucleotide retention. However, the retention time slightly increased when the pH was lower than 9. The STD-NMR technique combined with chromatographic experiments was thus successfully used to screen amino acid–nucleotide interactions.