title: Abiotic Protein Fragmentation by Manganese Oxide: Implications for a Mechanism to Supply Soil Biota with Oligopeptides.
abstract: The ability of plants and microorganisms to take up organic nitrogen in the form of free amino acids and oligopeptides has received increasing attention over the last two decades, yet the mechanisms for the formation of such compounds in soil environments remain poorly understood. We used Nuclear Magnetic Resonance (NMR) and Electron Paramagnetic Resonance (EPR) spectroscopies to distinguish the reaction of a model protein with a pedogenic oxide (Birnessite, MnO2) from its response to a phyllosilicate (Kaolinite). Our data demonstrate that birnessite fragments the model protein while kaolinite does not, resulting in soluble peptides that would be available to soil biota and confirming the existence of an abiotic pathway for the formation of organic nitrogen compounds for direct uptake by plants and microorganisms. The absence of reduced Mn(II) in the solution suggests that birnessite acts as a catalyst rather than an oxidant in this reaction. NMR and EPR spectroscopies are shown to be valuable tools to observe these reactions and capture the extent of protein transformation together with the extent of mineral response.
authors.affiliation: Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
authors.forename: Patrick N
authors.initials: PN
authors.lastname: Reardon
authors.affiliation: Department of Crop and Soil Science, Oregon State University , Corvallis, Oregon 97331, United States.
authors.forename: Stephany S
authors.initials: SS
authors.lastname: Chacon
authors.affiliation: Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
authors.forename: Eric D
authors.initials: ED
authors.lastname: Walter
authors.affiliation: Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Bowden
authors.affiliation: Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
authors.forename: Nancy M
authors.initials: NM
authors.lastname: Washton
authors.affiliation: Department of Crop and Soil Science, Oregon State University , Corvallis, Oregon 97331, United States.|Institut für Bodenlandschaftsforschung, Leibniz Zentrum für Agrarlandschaftsforschung (ZALF) , Eberswalder Straße 84, 15374 Müncheberg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Kleber
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D058448:Biota; D004578:Electron Spin Resonance Spectroscopy; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D017895:Manganese Compounds / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry; D009842:Oligopeptides / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D000072417:Protein Domains; D059748:Proteolysis; D012987:Soil
chemical_list: D001426:Bacterial Proteins; D017895:Manganese Compounds; D008903:Minerals; D009842:Oligopeptides; D010087:Oxides; D012987:Soil; C505018:birnessite; C027424:manganese oxide