Use of plasma induced modification of biomolecules (PLIMB) to evaluate hemin dissociation from fish and bovine methemoglobins.

Hemin dissociation occurs much faster from fish methemoglobin (metHb) compared to mammalian metHb yet the mechanism remains poorly understood. This may involve enhanced solvent access to His(E7) of fish metHbs by a protonation mechanism. Plasma induced modification of biomolecules (PLIMB) produces free radicals that covalently modify solvent accessible residues of proteins, and so can provide insight regarding accessibility of hydronium ions to protonate His(E7). PLIMB-induced modifications to heme crevice sites of trout IV and bovine metHb were determined using tandem mass spectrometry after generating peptides with Trypsin/Lys-C. αHis(CE3) was more modified in trout attributable to the more dynamic nature of bovine αHis(CE3) from available crystal structures. Although His(E7) was not found to be more modified in trout, aspects of trout peptides containing His(E7) hampered modification determinations. An existing computational structure-based approach was also used to estimate protonation tendencies, suggesting His(E7) of metHbs with low hemin affinity are more protonatable.

Memristive Behavior Enabled by Amorphous-Crystalline 2D Oxide Heterostructure.

The emergence of memristive behavior in amorphous-crystalline 2D oxide heterostructures, which are synthesized by atomic layer deposition (ALD) of a few-nanometer amorphous Al2 O3 layers onto atomically thin single-crystalline ZnO nanosheets, is demonstrated. The conduction mechanism is identified based on classic oxygen vacancy conductive channels. ZnO nanosheets provide a 2D host for oxygen vacancies, while the amorphous Al2 O3 facilitates the generation and stabilization of the oxygen vacancies. The conduction mechanism in the high-resistance state follows Poole-Frenkel emission, and in the the low-resistance state is fitted by the Mott-Gurney law. From the slope of the fitting curve, the mobility in the low-resistance state is estimated to be ≈2400 cm2 V-1 s-1 , which is the highest value reported in semiconductor oxides. When annealed at high temperature to eliminate oxygen vacancies, Al is doped into the ZnO nanosheet, and the memristive behavior disappears, further confirming the oxygen vacancies as being responsible for the memristive behavior. The 2D heterointerface offers opportunities for new design of high-performance memristor devices.

Plasma-Generated OH Radical Production for Analyzing Three-Dimensional Structure in Protein Therapeutics.

Protein three-dimensional structure dynamically changes in solution depending on the presence of ligands and interacting proteins. Methods for detecting these changes in protein conformation include 'protein footprinting,' using mass spectrometry. We describe herein a new technique, PLIMB (Plasma Induced Modification of Biomolecules), that generates µs bursts of hydroxyl radicals from water, to measure changes in protein structure via altered solvent accessibility of amino acid side chains. PLIMB was first benchmarked with model compounds, and then applied to a biological problem, i.e., ligand (EGF) induced changes in the conformation of the external (ecto) domain of Epidermal Growth Factor Receptor (EGFR). Regions in which oxidation decreased upon adding EGF fall along the dimerization interface, consistent with models derived from crystal structures. These results demonstrate that plasma-generated hydroxyl radicals from water can be used to map protein conformational changes, and provide a readily accessible means of studying protein structure in solution.