Diamagnetic metal ion – nucleoside interactions in solution as studied by 15N nuclear magnetic resonance

1982 ◽  
Vol 60 (6) ◽  
pp. 787-791 ◽  
Author(s):  
G. W. Buchanan ◽  
J. B. Stothers
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Metal Ion ◽  
Chemical Shifts ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Physical Measurements ◽  
Highly Sensitive ◽  
Site Selective ◽  
Nuclear Magnetic

15N nuclear magnetic resonance chemical shifts are shown to be highly sensitive to site-selective diamagnetic metal ion binding for the nucleosides adenosine, cytidine, and guanosine. Conclusions regarding preferred complexation sites are compared with results derived from other physical measurements, and with expectations based on electron density calculations.

Carbon-13 nuclear magnetic resonance study of potassium and thallium ion binding to the Gramicidin A transmembrane channel

1985 ◽  
Vol 63 (7) ◽  
pp. 1976-1981 ◽  
Author(s):  
D. W. Urry ◽  
T. L. Trapane ◽  
C. M. Venkatachalam ◽  
K. U. Prasad
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Binding Constants ◽  
Potassium Ion ◽  
Gramicidin A ◽  
Ion Concentration ◽  
Ion Binding ◽  
Carbonyl Carbon ◽  
Nuclear Magnetic

By means of carbon-13 nuclear magnetic resonance, carbonyl carbon ion-induced chemical shifts of the Gramicidin A channel are determined at 70 °C and analyzed as a function of potassium ion concentration and as a function of thallium ion concentration. In both cases two binding processes are observed. The estimated binding constants for potassium ion binding are 28/M and 2.4/M for the tight (single ion occupancy) and weak (double ion occupancy) sites, respectively, and for thallium ion binding are of the order of 103/M for the tight site and approximately 70/M for the weak site. These studies, which utilize a 90% enriched carbonyl carbon within the binding site of the channel to monitor ion interaction, argue for the presence of two ions in the channel for conditions under which planar bilayer transport studies are commonly carried out.

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