Effects of the Hydrophobicity of Key Residues on the Characteristics and Stability of Glucose Oxidase on a Graphene Surface

Glucose oxidase (GOx) is one of the most widely investigated enzymes in the field of bioelectrochemistry. It is mainly used for the detection of glucose in solutions and enzyme-based biofuel cells. On the basis of the combination of GOx with graphene, novel nanodevices exceeding conventional limits can be developed. To develop a hybrid enzyme-graphene nanodevice with a good performance, it is important that GOx is deposited well on the graphene surface while maintaining its structure and not impeding the oxidation activity of the GOx. In this study, we propose a method to improve the stability of GOx and secure its immobility on the graphene sheet and its glucose-binding affinity by single-point mutation of GOx using molecular dynamics simulations. We confirm that the structural stability, immobility, and substrate binding affinity of GOx can be modified by changing the hydrophobicity of a key residue. We demonstrate that biosensors or biofuel cells can be redesigned and their properties can be improved by using molecular dynamics simulation.

Mechanical and vibrational characterization of amyloid-like HET-s nanosheets based on the skewed plate theory

Pathological amyloidogenic prion proteins have a toxic effect on functional cells in the human cerebrum because of poor degradability and the tendency to accumulate in an uncontrolled manner under physiological conditions. HET-s, a fungal prion protein, is known to undergo conformational variations from fibrillar to nanosheet structures during a change from low to high pH conditions. It has been said that this conformational change can lead to self-propagation by nucleating on the lateral surface of singlet fibrils. Efforts have been made toward the mechanical characterization of fibrillar amyloids, but a global understanding of amyloid-like HET-s nanosheet structures is lacking. In this study, we analyzed the mechanical and vibrational characteristics of the skewed HET-s nanosheet structures that developed under neutral pH conditions by performing various molecular dynamics simulations. By applying the skewed plate theory to HET-s nanosheets for various length scales with numerous pores inside the structures, we found that the skewed HET-s nanosheet structure has mechanical properties comparable to those of previously reported biological film materials and nanomaterials. Considering the inherent characteristics of structural stability, our observation provides valuable and detailed structural information on skewed amyloid-like HET-s nanosheets.