Carboxyl-rich alicyclic molecules

Hertkorn et al. (2006) analyzed DOM that was isolated by ultrafiltration from surface and deep waters. They used ll and 13C NMR spectra and FTICR mass spectra to resolve DOM into three normative components heteropolysaccharides, carboxyl-rich alicyclic molecules (CRAM), and peptides (accounting for all N).They reported that surface DOM contains 60.1% heteropolysacharides, 22.9% CRAM, and 23.6% peptides and that deep DOM contains 27.1% heteropolysaccharides, 50.9% CRAM, and 20.7% peptides. Unlike Sannigrahi et al. (2005), who gave empirical formulae of the endmembers of the three-component model that was used to analyze their 13C NMR data, Hertkorn et al. (2006) did not provide empirical formulae for heteropolysaccharides, CRAM, and peptides. It is unclear how to calculate average chemical formulae of surface and deep DOM from their results. 

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