Biological metal-stabilization factor identification
Abstract
Copper nanoparticlcs produced by physical and chemical methods, arc unstable in the presence of oxygen and tend to oxidize rapidly due to their extremely small size and lack of a protective agent. The proposed research seeks lo investigate the observed phenomenon that biologically produced nanoparticles made of elemental copper show significantly enhanced stability compared to copper nanoparticlcs produced by other means. It was hypothesized that a biological stabilizalion factor was produced by the bacterium Morganella psychrotolerans during the nanoparticlc synthesis that protected the nanoparticles from oxidation. We wish to identify the stabilization factor and will do so by running a series of experiments on the copper nanoparticles produced by M. psychrotolerans. We aim lo identify the stabilization factor present on the copper nanoparticlcs produced by M. psychrotolerans. One of four possibilities is expected to be the cause of stabilization of the nanoparticlcs: 1) Protein(s) around the nanoparticle that fonn a "protective shell inhibiting oxidation. 2) A lipid layer around the nanoparticle that keeps it stable from oxidation. 3) The presence of thiolate - copper bonds (lo proteins, peptides or small molecules) on the surface of the copper nanoparticlcs. 4) Stabilizing sugars on the surface of the nanoparticle preventing oxidation. The four possible scenarios will be investigated by the analysis ofnanoparticlc samples isolated from the bacteria through ultracentrifugation, Different techniques and treatments will be applied to the nanoparticles prior lo analysis by mass spectrometry (MS). 1) Direct MS analysis of the isolated nanoparticles using matrix-assisted laser desorption/ionization time of flight (MALDl-ToF) MS. 2) Any proteins will be removed from the nanoparticles through denaturalion, solvent extraction and/or enzymatic digestion and electrospray (ESI) or MALDI MS experiments used to detennine the intact mass of the protective protcinfpeptidc. Peptide mass fingerprinting, and bottom-up/top-down MS fragmentation experiments will dctennine the identity of a protective protein. 3) The presence of a lipid or sugar shell will be confirmed through staining. Further identification will use solvent extraction, MS and NMR. Lipids/carbohydrates will be characterized based on intact mass and structural infonnation sort using tandem MS/MS experiments. 4) Small molecule identification will use ESl-MS to determine the elemental formula of any small molecule present and inductively coupled plasma-MS (ICP-MS) to provide stoichiometric infonnation concerning the copper to ligand ratio. A more accurate measure of the delayed oxidation provided by the stabilization factor will also be performed. This will require regular analysis of a nanoparticlc sample by X-ray photoelectron spectrometry over the length of the project. An effective stabilization factor for copper nanoparticles is extremely important, as it will allow their use in many applications such as catalysts, antimicrobials and optics. The identification of the stabilization factor of biologically synthesized copper nanoparticles will lead to more effective and accurate methods of characterization and optimization. The use of such a protective compound may also be investigated on other metallic species of nanoparticles that currently also suffer from instability under aerobic conditions.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 12, 2017
- Source ID
- W911NF1510171
Entities
People
- Louise E Horsfall
Organizations
- Army Contracting Command
- United States Army
- University of Edinburgh