Preservation of protein in marine systems: Hydrophobic and other noncovalent associations as major stabilizing forces

• Published in: Geochimica et cosmochimica acta 2001-05, Vol.65 (9), p.1467-1480
• Main Authors: Nguyen, Reno T, Harvey, H.Rodger
• Format: Article
• Language: English
• Subjects: Marine
• ISSN: 0016-7037; 1872-9533
• DOI: 10.1016/S0016-7037(00)00621-9

—The fate of proteins during early diagenesis was investigated in environments with low mineral content to assess preservation mechanisms other than mineral sorption. Preservation was examined in anoxic, organic-rich sediments of Mangrove Lake, a marine environment located in Bermuda, and for particulate material generated during oxic decay of diatoms. N-phenacylthiazolium bromide (PTB) treatment tested the hypothesis that proteins may undergo modification reactions with glucose to form advanced-glycation end products (AGEs). A small but significant release (additional 14%) of proteins was observed after PTB treatment in surficial sediments, indicating that some aggregations can proceed through an α-dicarbonyl intermediate of the AGE pathway. Size-exclusion high-pressure liquid chromatography with protein fluorescence, absorbance, and evaporative light-scattering detector measurements under native (phosphate or bicarbonate buffers) and denaturing (guanidine · HCl, urea, or acetonitrile) conditions point to the importance of hydrophobic and other noncovalent interactions in the stabilization of proteinaceous material in the environment. Soluble aggregates of substantial, relative molecular mass ( M r ≳ 10 6) appear to be formed early in the diagenetic sequence. The preferential preservation of very high M r, multisubunit phytoplankton proteins in sediments suggests that such aggregations confer resistance to degradation. Alternatively, some of the proteinaceous material may represent that fraction of organic matter that is highly prone to aggregations. Extended incubations (18 h; 37°C) with trypsin and proteinase-K showed that much of the aggregates that could be extracted are receptive to proteolytic cleavage. Buffer-, surfactant-, and NaOH-extractable aggregates comprised most of the acid-hydrolyzable proteinaceous material in detritus and surficial sediments but