| STRUCTURE |
Ocean's organic nitrogen charted Amide-containing biopolymers that help control the ocean's nitrogen budget--and, consequently, its denizens' ability to sequester atmospheric CO2--have been chemically characterized (Science 2005, 308, 1007). These and other nitrogen-containing biopolymers (known as dissolved organic nitrogen or DON) are abundant in many parts of the ocean, even where the availability of inorganic nitrogen limits the productivity of marine organisms. A team led by Lihini I. Aluwihare of Scripps Institution of Oceanography collected high-molecular-weight DON (HMWDON) from both the surface and the deep ocean. They then subjected the samples' amide linkages to mild acid hydrolysis to differentiate proteins (bottom) from N-acetyl amino polysaccharides such as chitin (top). Such treatment yields amino acids in the case of proteins, and acetic acid in the case of chitin and related polymers. They find that N-acetyl amino polysaccharides account for half of the surface HMWDON. The remaining surface HMWDON and nearly all deep-sea DON, however, resist both chemical hydrolysis and biological degradation. |
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