Thermodynamics of adsorption of alcohol dehydrogenase on the gold nanoparticle surface: a model based analysis versus direct measurement

Highly elastic, fatigue-resistant, antibacterial, conductive, and nanocellulose-enhanced hydrogels with selenium nanoparticles loading as strain sensors

The fabrication of highly elastic, fatigue-resistant and conductive hydrogels with antibacterial properties is highly desirable in the field of wearable devices. However, it remains challenging to simultaneously realize the above properties within one hydrogel without compromising excellent sensing ability. Herein, we fabricated a highly elastic, fatigue-resistant, conductive, antibacterial and cellulose nanocrystal (CNC) enhanced hydrogel as a sensitive strain sensor by the synergistic effect of biosynthesized selenium nanoparticles (BioSeNPs), MXene and nanocellulose. The structure and potential mechanism to generate biologically synthesized SeNPs (BioSeNPs) were systematically investigated, and the role of protease A (PrA) in enhancing the adsorption between proteins and SeNPs was demonstrated. Additionally, owing to the incorporation of BioSeNPs, CNC and MXene, the synthesized hydrogels showed high elasticity, excellent fatigue resistance and antibacterial properties. More importantly, the sensitivity of hydrogels determined by the gauge factor was as high as 6.24 when a high strain was applied (400-700 %). This study provides a new horizon to synthesize high-performance antibacterial and conductive hydrogels for soft electronics applications.

Superoxide Dismutase Catalyzed Size-Adjustable Selenium Nanoparticles in Saccharomyces boulardii

Selenium nanoparticles (SeNPs) are important and safe food and feed additives that can be used for dietary supplementation. In this study, a mutagenic strain of Saccharomyces boulardii was employed to obtain biologically synthesized SeNPs (BioSeNPs) with the desired particle size by controlling the dosage and duration of sodium selenite addition, and the average particle size achieved was 55.8 nm with protease A encapsulation. Transcriptomic analysis revealed that increased expression of superoxide dismutase 1 (SOD1) in the mutant strain effectively promoted the synthesis of BioSeNPs and the formation of smaller nanoparticles. Under sodium selenite stress, the mutant strain exhibited significantly increased expression of glutathione peroxidase 2 (GPx2), which was significantly greater in the mutant strain than in the wild type, facilitating the synthesis of glutathione selenol and providing abundant substrates for the production of BioSeNPs. Furthermore, based on the experimental results and transcriptomic analysis of relevant genes such as sod1, gpx2, the thioredoxin reductase 1 gene (trr1) and the thioredoxin reductase 2 gene (trr2), a yeast model for the size-controlled synthesis of BioSeNPs was constructed. This study provides an important theoretical and practical foundation for the green synthesis of controllable-sized BioSeNPs or other metal nanoparticles with potential applications in the fields of food, feed, and biomedicine.

Lysozyme adsorption on carbonaceous nanoparticles probed by second harmonic light scattering

The first hyperpolarizability (β) of two different sizes (15 and 35 nm) of carbonaceous nanoparticle (CNP) is reported for the first time using second harmonic light scattering (SHLS). The β values of the CNPs were found to be larger than those of organic molecules like pNA but lower than those of plasmonic nanoparticles like gold and silver. SHLS was further used to investigate the adsorption of a model protein Lysozyme (Lyz) on these CNPs, which is crucial for the design of safe and effective CNP-based therapeutics. The change in SH intensity from the CNPs on the addition of Lyz was recorded and fitted to the modified Langmuir adsorption model (MLM). The binding constant, free energy changes and surface coverage values show that Lyz is physisorbed on the CNPs forming less than a monolayer. The temperature dependent SH intensity measurements enabled direct determination of enthalpy and entropy changes for Lyz adsorption. The enthalpy and entropy changes reveal that Lyz adsorption is endothermic and entropically driven.

Exploring Enzymatic Conformational Dynamics at Surfaces through μ-FTIR Spectromicroscopy

Immobilization of proteins onto solid supports has critical industrial, technological, and medical applications, and is a daily task in chemical research. Significant conformational rearrangements often occur due to enzyme-surface interactions, and it is of broad interest to develop methods to probe and better understand these molecular-level changes that contribute to the enzyme's catalytic activity and stability. While circular dichroism is a common method for solution-phase conformational study, the application to surface-supported proteins is not trivial and spatial mapping is not viable. On the other hand, a nonlinear laser spectroscopy technique used to analyze surfaces and interfaces is not often found in most laboratories, therefore requiring an alternative and reliable method. Here, we employed high-dimensional data spectromicroscopy analysis in the infrared region (μ-FTIR) to investigate the enzyme's conformational change when adsorbed onto solid matrices, across a ca. 20 mm2 area. Alcohol dehydrogenase (ADH) enzyme was adopted as a model enzyme to interact with CaF2, Au, and Au-thiol model substrates, strategically chosen for mapping the enzyme dynamics on solid surfaces with different polarity/hydrophobicity properties and extendable to other materials. Two-dimensional chemical maps indicate that the enzyme adsorbs with different patterns in which secondary structures dynamically adjust to optimize interprotein and enzyme-surface interactions. The results suggest an experimental approach to identify and map enzyme conformational dynamics onto different solid surfaces across space and provide insights into immobilized protein structure investigations for areas such as biosensing and bioenergy.

Thermodynamics of Multilayer Protein Adsorption on Gold Nanoparticle Surface

We report the thermodynamics of protein adsorption on negatively charged colloidal gold nanoparticles (GNPs) of 16 nm to 69 nm at pH 7.0. Three biologically important proteins of varying size,...