LINK<\/strong><\/a><\/p>\n\n\n\n“Strecker synthesis creates \u03b1\u2013amino acids from prebiotically plausible substrates (cyanide, ammonia, and aldehydes) and is widely hypothesized to be a key mechanism in the chemistry that led to life on Earth and on other planets. To better constrain the synthetic environments and precursors of abiotic \u03b1\u2013amino acids, and to determine unique signatures of abiogenic amino acids, we measured the molecular-averaged and site-specific carbon and nitrogen isotope effects for the Strecker synthesis of alanine. The reaction steps of the Strecker synthesis can be divided into two groups: an initial series of reversible amination and nitrile-addition reactions (\u2018equilibration\u2019) and a second series of irreversible hydrolysis reactions (\u2018hydrolysis\u2019). The equilibration of cyanide, acetaldehyde, and ammonia with the intermediate, \u03b1\u2013aminopropionitrile (\u03b1-APN), has a measured 55.1 \u2030 equilibrium nitrogen isotope effect between the 15N\u2013rich amine nitrogen in \u03b1-aminopropionitrile and the 15N\u2013poor ammonia and a 20.0 \u2030 equilibrium carbon isotope effect between the 13C-poor C\u20132 site in \u03b1\u2013aminopropionitrile and the 13C\u2013rich carbonyl carbon in acetaldehyde. The first irreversible hydrolysis step is inferred to have an up to 10 \u2030 normal carbon fractionation (i.e., faster for 12C, slower for 13C) for the whole molecule, but it also has one or more side reactions that deplete the reactive \u03b1-APN reservoir by up to 15 \u2030. The second hydrolysis step has a 15.4 \u2030 normal kinetic isotope effect on the amide (C\u20131) site of alaninamide, which becomes the carboxyl site of alanine. Other \u03b1\u2013amino acids will likely experience similar nitrogen isotope fractionations between ammonia and their amine sites, and similar carbon isotope fractionations between the carbonyl carbon in reactant aldehydes or ketones and the intermediate \u03b1\u2013aminonitrile, and between cyanide and the carboxyl site. Therefore, these isotope effects allow us to predict the carbon and nitrogen isotopic contents and intramolecular structures of \u03b1-amino acids formed by Strecker synthesis based on their substrates\u2019 isotopic compositions, or to infer the isotopic compositions of substrates from which amino acids formed, for example in the case of the amino-acid-rich carbonaceous chondrites. The site-specific C and N isotopic compositions of amino acids formed by Strecker chemistry contrast with those typical of terrestrial biosynthetic amino acids, so these data also provide a means of discriminating between biogenic and abiogenic \u03b1\u2013amino acids.”<\/p>\n","protected":false},"excerpt":{"rendered":"
L. Chimiak, J. Eiler, A. Sessions, C. Blumenfeld, M. Klatte, B.M. Stoltz Geochimica et Cosmochimica ActaAvailable online 20 January 2022 LINK “Strecker synthesis creates \u03b1\u2013amino acids from prebiotically plausible substrates (cyanide, ammonia, and aldehydes) and…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[152,9,576],"tags":[1865,250,3273,1135,2346,331],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/29980"}],"collection":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=29980"}],"version-history":[{"count":2,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/29980\/revisions"}],"predecessor-version":[{"id":29982,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/29980\/revisions\/29982"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=29980"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=29980"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=29980"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}