What can molecular dynamics simulations reveal about the stability of proteinaceous soil organic matter on mineral surfaces?

Abstract:

With the increased attention on climate change and the role of increasing atmospheric CO₂ levels in global warming, the need for an accurate depiction of the carbon cycling processes involved in the Earth’s three major carbon pools, i.e., atmosphere, terrestrial systems, and oceans has never been greater. Within the terrestrial system, soil organic matter (SOM) represents an important carbon sub-pool. Complexation of SOM with mineral interfaces and particles is believed to protect SOM from possible biotic and abiotic transformation and mineralization to carbon dioxide. However, obtaining a molecular scale picture of the interactions of the various types of SOM with a variety of soil minerals is a challenging endeavor, especially for experimental techniques. Molecular scale simulations techniques can be applied to study the atomistic, molecular, and nanoscale aspects of SOM-mineral associations, and, therefore, and aid in filling current knowledge gaps in the potential fate and stability of SOM in soil systems. Here, we will discuss our recent results from large-scale molecular dynamics simulation of protein, GB1, and its interaction with clay and oxide/hydroxide minerals (i.e., kaolinite, Na⁺-MMT, Ca²⁺-MMT, goethite, and birnessite) including a comparison of structural changes of the protein by, protein orientation with respect to, degree of protein binding to, and mobility on the mineral surfaces. Our molecular simulations indicate that these mineral surfaces, with the exception of birnessite, potentially preserve the physical properties of the GB1 protein.