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Designed Y³⁺ Surface Segregation Increases Stability of Nanocrystalline Zinc Aluminate.

ABSTRACT: The thermal stability of zinc aluminate nanoparticles is critical for their use as catalyst supports. In this study, we experimentally show that doping with 0.5 mol % Y₂O₃ improves the stability of zinc aluminate nanoparticles. The dopant spontaneously segregates to the nanoparticle surfaces in a phenomenon correlated with excess energy reduction and the hindering of coarsening. Y³⁺ was selected based on atomistic simulations on a 4 nm zinc aluminate nanoparticle singularly doped with elements of different ionic radii: Sc³⁺, In³⁺, Y³⁺, and Nd³⁺. The segregation energies were generally proportional to ionic radii, with Y³⁺ showing the highest potential for surface segregation. Direct measurements of surface thermodynamics confirmed the decreasing trend in surface energy from 0.99 for undoped to 0.85 J/m² for Y-doped nanoparticles. Diffusion coefficients calculated from coarsening curves for undoped and doped compositions at 850 °C were 4.8 × 10^-12 cm²/s and 2.5 × 10^-12 cm²/s, respectively, indicating the coarsening inhibition induced by Y³⁺ results from a combination of a reduced driving force (surface energy) and decreased atomic mobility.

SUBMITTER: Sotelo Martin LE

PROVIDER: S-EPMC9986873 | biostudies-literature | 2023 Mar

REPOSITORIES: biostudies-literature

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Designed Y3+ Surface Segregation Increases Stability of Nanocrystalline Zinc Aluminate.

Sotelo Martin Luis E LE O'Shea Nicole M NM Mason Jeremy K JK Castro Ricardo H R RHR

The journal of physical chemistry. C, Nanomaterials and interfaces 20230202 8

The thermal stability of zinc aluminate nanoparticles is critical for their use as catalyst supports. In this study, we experimentally show that doping with 0.5 mol % Y2O3 improves the stability of zinc aluminate nanoparticles. The dopant spontaneously segregates to the nanoparticle surfaces in a phenomenon correlated with excess energy reduction and the hindering of coarsening. Y3+ was selected based on atomistic simulations on a 4 nm zinc aluminate nanoparticle ...[more]

PMID: 36895659

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Project description:To understand the evolution of Verona integron-encoded metallo-β-lactamase (VIM) genes (blaVIM) and their clinical impact, microbiological, biochemical, and structural studies were conducted. Forty-five clinically derived VIM variants engineered in a uniform background and expressed in Escherichia coli afforded increased resistance toward all tested antibiotics; the variants belonging to the VIM-1-like and VIM-4-like families exhibited higher MICs toward five out of six antibiotics than did variants belonging to the widely distributed and clinically important VIM-2-like family. Generally, maximal MIC increases were observed when cephalothin and imipenem were tested. Additionally, MIC determinations under conditions with low zinc availability suggested that some VIM variants are also evolving to overcome zinc deprivation. The most profound increase in resistance was observed in VIM-2-like variants (e.g., VIM-20 H229R) at low zinc availability. Biochemical analyses reveal that VIM-2 and VIM-20 exhibited similar metal binding properties and steady-state kinetic parameters under the conditions tested. Crystal structures of VIM-20 in the reduced and oxidized forms at 1.25 Å and 1.37 Å resolution, respectively, show that Arg229 forms an additional salt bridge with Glu171. Differential scanning fluorimetry of purified proteins and immunoblots of periplasmic extracts revealed that this difference increases thermostability and resistance to proteolytic degradation when zinc availability is low. Therefore, zinc scarcity appears to be a selective pressure driving the evolution of multiple metallo-β-lactamase families, although compensating mutations use different mechanisms to enhance resistance.IMPORTANCE Antibiotic resistance is a growing clinical threat. One of the most serious areas of concern is the ability of some bacteria to degrade carbapenems, drugs that are often reserved as last-resort antibiotics. Resistance to carbapenems can be conferred by a large group of related enzymes called metallo-β-lactamases that rely on zinc ions for function and for overall stability. Here, we studied an extensive panel of 45 different metallo-β-lactamases from a subfamily called VIM to discover what changes are emerging as resistance evolves in clinical settings. Enhanced resistance to some antibiotics was observed. We also found that at least one VIM variant developed a new ability to remain more stable under conditions where zinc availability is limited, and we determined the origin of this stability in atomic detail. These results suggest that zinc scarcity helps drive the evolution of this resistance determinant.

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Designed Y³⁺ Surface Segregation Increases Stability of Nanocrystalline Zinc Aluminate.

Publications

Designed Y<sup>3+</sup> Surface Segregation Increases Stability of Nanocrystalline Zinc Aluminate.

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