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Biomedical subjects

J Grandjean

Publications and source records attributed to J Grandjean.

31 records · Page 2Linked to original sources
PubMed1980

Sodium-23 nuclear magnetic resonance as an indicator of sodium binding to troponin C and tryptic fragments, in relation to calcium content and attendant conformational changes.

The relaxation rate enhancements of the 23Na nuclei for NaHCO3 solutions of troponin C and its tryptic peptides TR-1 and TR-2 indicate true binding of Na+ ions to these biomolecules. The low-affinity sites I and II of TR-1 and troponin C are the sites of competitive Na+/Ca2+ binding, below one calcium ion per molecule, with log KNa approximately 2. At low calcium content Na+ ions bind to TR-2 and to troponin C non-competitively with Ca2+ ions; binding of Ca2+ ions to the high-affinity sites III and IV allosterically affects the binding of the Na+ ions: even when sites I and II, located on TR-1 or sites I, II, III, IV of troponin C, are saturated with Ca2+ ions, Na+ ions continue to bind weakly at secondary binding sites.

Animals↗
PubMed1980

Sodium-23 nuclear magnetic resonance as an indicator of sodium binding to calmodulin and tryptic fragments, in relation to calcium content.

The relaxation rate enhancements of the 23Na nuclei for NaHCO3 solutions of calmodulin and its tryptic peptides TR-1 and TR-2 indicate true binding of Na+ ions to these biomolecules. With both TR-1 and TR-2, Na+ binding occurs in competition with Ca2+ and Mg2+ binding: log KNa approximately equal to 2, log KMg apoproximately equal to 4, log KCa approximately equal to 6 for TR-1; and log KNa approximately equal to 2, log KMg approximately equal to 3, log KCa approximately equal to 5 for TR-2. All the binding constants are systemically greater for binding to TR-1, as compared to TR-2. There is also an increase in KNa for TR-1 of calmodulin as compared to the homologous tryptic fragment of troponin C. The increased binding is identified tentatively with site I of calmodulin. The binding constants KNa, KCa and KMg of calmodulin appear to be finely tuned to the intracellular concentrations of these cations.

Animals↗