부산대학교 도서관

We studied the efficacy of the tris-glycinatocobaltate(II) complex ([Co(gly)[sub 3]][sup -]) as a shift reagent (SR) for chloride by [sup 35]CI NMR spectroscopy and compared to that of Co[sup 2+, sub (aq)]. Due to the relatively low thermodynamic stability of [Co(gly)[sub 3]][sup -], a 1:3 Co(II)/gly stoichiometric solution at physiological pH is approximately a 2:1 mixture of [Co(gly)[sub 2](H[sub 2]O)[sub 2]] and [Co(gly)(H[sub 2]O)[sub 4]][sup +]. This SR was found to be stable up to higher pH values than Co[sup 2+, sub (aq)], better preventing Co(OH)[sub 2] formation at alkaline pH. No significant differences in the [sup 35]Cl[sup -] NMR chemical shift induced by Co(II)/gly or Co[sup 2+, sub (aq)] were observed in the presence of physiological concentrations of either Ca[sup 2+] or Mg[sup 2+]' or of either Na[sup +] or K[sup +]. Although Co[sup 2+, sub (aq)] was almost twice as effective as Co(II)/gly in shifting the [sup 35]Cl[sup -] NMR resonance at the same high ρ ([SR]/[Cl[sup -]]) value and low ionic strength, Co[sup 2+, sub (aq)] showed a significant decrease (p < 0.05) in the [sup 35]Cl[sup -] chemical shift at higher ionic strength. Line widths at half-height were significantly (p < 0.05) less for Co(II)/gly than for Co[sup 2+, sub (aq)] at ρ values in the range 0.066-0.40. Intracellular chloride was clearly detectable by [sup 35]Cl NMR spectroscopy in human skin fibroblast cells suspended in medium containing 40 mM Co(II)/gly SR. We determined that, although Co[sup 2+, sub (aq)] provides a larger shift than Co(II)/gly at the same ρ value there are significant advantages for using Co(II)/gly, such as pH stability, ionic strength independent chemical shifts, narrow [sup 35]Cl[sup -] NMR resonances, and reduced cellular toxicity, as a SR in biological systems. [ABSTRACT FROM AUTHOR]