for an understanding of the cation selectivity and general binding characteristics of macrotetralide antibiotic nonactin ( na ) with ions of different sizes and charges , the nature of binding of divalent caption , ca2+ , to na and conformation of the na-ca2+ complex have been studied by use of 270-mhz proton nuclear magnetic resonance ( 1h nmr ) and carbon-13 nuclear magnetic resonance ( 13c nmr ) .
C0007447
cation
C0022023
ions