Biological chemicals in rock coatings
- 出版日期：2004.
- 页数：1 v. :
- 第一责任说明：Randall Stewart Perry.
- 分类号：a273 ; a356
- ISBN：0496784617(ebk.) :
MARC全文
02h0029356 20120611135553.0 cr un||||||||| 120611s2004 xx ||||f|||d||||||||eng | 3131217 0496784617(ebk.) : CNY371.35 NGL NGL NGL a273 ; a356 Perry, Randall Stewart. Biological chemicals in rock coatings [electronic resource] / Randall Stewart Perry. 2004. 1 v. : digital, PDF file. Adviser: Gillespie, Alan R., Staley, James T. Thesis (Ph.D.)-- University of Washington, 2004. Stable and unstable amino acids, DNA, nitrogen, carbon, and several polyfunctional chemicals were found along with amorphous hydrated silica (opal) in microstromatilitic desert varnish rock coatings from deserts, primarily in the US southwest. The presence of labile organic compounds, especially in deserts, requires a mechanism for their preservation. In this study the discovery of silica in desert varnish suggests that preservation may be facilitated by silicic acid (Si(OH)4) or (di)silicic ((HO)3Si-O-Si(OH) 3) through the formation of a variety of complexes with ions and organic molecules, including mucopolysaccharides, glycoproteins that are enriched in hydroxyl amino acids (serine and threonine), glycine, aspartic and glutamic acids. Although organo-silica complexes were not directly observed, previous work has shown that amorphous hydrated silica forms both Si-O-C and Si-O-metal complexes. Organic candidates include amino acids, some sugars, unsaturated polyhydroxy compounds, catechols (1, 2-diphenols), and other compounds with rigid structures, as well as some flexible sugar-related substances, polyols and sugar acids. It is suggested here that prokaryotic DNA cloned from coatings and amino acids may be sequestered in silica, clay minerals, or by complexation with divalent and trivalent ions, as it is known that Fe ions interact with phosphate groups and Mn interacts with nitrogen bases of DNA. The addition of Fe ions to a DNA-Mn complex may lead to stability and Mn binding may occur irrespective of Fe-DNA interlinking. This might provide a mechanism for preserving DNA found in silica-rich rock coatings. Not only organic substances then, but metals also might participate in polymerizing, crosslinking and hardening, as small quantities of silicic acids condense and fuse by gelling. Desert varnish contains chemical and mineral components from the local environment. Polymerization of silicic acid may be the underlying process of formation of silica glazes and desert varnish and, if organos-ilica processes are important in the formation of rock coatings, they also may be relevant to studies of Earth's oldest paleoenvironments, fossils (＞3,400 my), and possible biotic chemicals on other planetary bodies, especially Mars. Rocks ; Coatings. ; Silicic acid. Surfaces. Electronic dissertations. aeBook. aCN bNGL http://pqdt.bjzhongke.com.cn/Detail.aspx?pid=bSsDVj77KbU%3d NGL Bs1460 rCNY371.35 ; h1 bs1204