USE OF HIGH-RESOLUTION C-13 NMR TO EXAMINE THE ENZYMATIC COVALENT BINDING OF C-13-LABELED 2,4-DICHLOROPHENOL TO HUMIC SUBSTANCES

A novel application of a standard NMR technique has been employed to characterize the enzymatic coupling of a pollutant (2,4-dichlorophenol, 2,4-DCP) to humic material. The application involves the use of 2,4-DCP labeled with C-13 at specific molecular sites in combination with broad-band decoupled C-13 NMR to determine the nature of bonding interactions with Minnesota peat humic acid. Any alteration in the chemical structure of the 2,4-DCP due to coupling with the humic acid results in changes in the 13C chemical shifts of the labeled carbons which are indicative of the site and type of bonding interaction. These data provide direct evidence for the formation of covalent bonds between the pollutant and a humic acid via enzymatic coupling. The success of this approach indicates that we now have a method for examining the binding of pollutants and soil organic matter.