Acceleration of carbon-13 spin–lattice relaxation times in amino acids by electrolytes

✍ Scribed by Jinping Tian; Yingwu Yin

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 132 KB
• Volume: 42
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1374

✦ Synopsis

Measurements

of the enhancement, by various electrolytes, of the spin-lattice relaxation time of carbon-13 at different locations in a number of amino acids are reported. Spin-lattice relaxation times T 1 of all the carbons in amino acids generally tend to decrease with increase in the concentration of electrolytes, the largest effects often being observed for the charged carboxylate groups of the amino acids. Carboxylic carbons in amino acids are the sensitive 'acceptor' of the 13 C spin-lattice relaxation accelerating effects offered by electrolytes, and the 13 C spin-lattice relaxation accelerating ability of electrolytes decreases in the order Mg(ClO 4 / 2 > MgCl 2 > CaCl 2 > NaCl > KCl > LiClO 4 > NaOH. The mechanisms of the observed phenomena are discussed in terms of intermolecular interaction, paramagnetic impurities in electrolytes and other mechanisms; large contributions of intermolecular interactions with electrolytes are present on complex formation between amino acids and metal ions and the incoming 'unsaturation' of the primary solvation shell of cations with the increase in electrolyte concentration.