Improved enzyme immobilization on an ionic-complementary peptide-modified electrode for biomolecular sensing

Supramolecular assembly of protein building blocks: from folding to function

Several phenomena occurring throughout the life of living things start and end with proteins. Various proteins form one complex structure to control detailed reactions. In contrast, one protein forms various structures and implements other biological phenomena depending on the situation. The basic principle that forms these hierarchical structures is protein self-assembly. A single building block is sufficient to create homogeneous structures with complex shapes, such as rings, filaments, or containers. These assemblies are widely used in biology as they enable multivalent binding, ultra-sensitive regulation, and compartmentalization. Moreover, with advances in the computational design of protein folding and protein-protein interfaces, considerable progress has recently been made in the de novo design of protein assemblies. Our review presents a description of the components of supramolecular protein assembly and their application in understanding biological phenomena to therapeutics.

Molecular-Level Insights into Orientation-Dependent Changes in the Thermal Stability of Enzymes Covalently Immobilized on Surfaces

Surface-immobilized enzymes are important for a wide range of technological applications, including industrial catalysis, drug delivery, medical diagnosis, and biosensors; however, our understanding of how enzymes and proteins interact with abiological surfaces on the molecular level remains extremely limited. We have compared the structure, activity, and thermal stability of two variants of a β-galactosidase attached to a chemically well-defined maleimide-terminated self-assembled monolayer surface through a unique cysteinyl residue. In one case the enzyme is attached through an α helix and in the other case through an adjacent loop. Both enzymes exhibit similar specific activities and adopt similar orientations with respect to the surface normal, as determined by sum-frequency generation and attenuated total reflectance FT-IR spectroscopies. Surprisingly, however, the loop-tethered enzyme exhibits a thermal stability 10 °C lower than the helix-tethered enzyme and 13 °C lower than the enzyme in free solution. Using coarse-grain models, molecular dynamics simulations of the thermal unfolding of the surface-tethered enzymes were able to reproduce these differences in stability. Thus, revealing that tethering through the more flexible loop position provides more opportunity for surface residues on the protein to interact with the surface and undergo surface-induced unfolding. These observations point to the importance of the location of the attachment point in determining the performance of surface-supported biocatalysts and suggest strategies for optimizing their activity and thermal stability through molecular simulations.

Proteins and peptides as biological nanowires: towards biosensing devices

The current landscape of nanotechnology is such that attention is being given to those materials that self-assemble, as a mode of "bottom-up" fabrication of nanomaterials. The field of nanotubes and nanowires has long been dominated by carbon nanotubes and inorganic materials. However in more recent years, the search for materials with desirable properties, such as self-assembly, has unsurprisingly led to the biological world, where functional nanoscale biomolecular assemblies are in abundance.Potential has been seen for a number of these assemblies to be translated into functional nanomaterials. The early days of bionanotechnology saw a lot of attention given to DNA molecules as nanowires, and proteins and peptides have now also been seen to have promise in this area. With most of the biological structures investigated having low conductivity in the native state, the use of biomolecules as templates for the formation of metallic and semiconductor nanowires has been the direction taken.This chapter will discuss the use of various biomolecules and biomolecular assemblies as nanowires, with a particular emphasis on proteins, beginning with an introduction into the field of nanotubes and nanowires. Many applications are now recognized for nanowires, but for brevity, this chapter will focus solely on their use as biosensors, using glucose sensors as a case study.

Room temperature synthesis of hydrophilic Ln(3+)-doped KGdF4 (Ln = Ce, Eu, Tb, Dy) nanoparticles with controllable size: energy transfer, size-dependent and color-tunable luminescence properties

In this paper, we demonstrate a simple, template-free, reproducible and one-step synthesis of hydrophilic KGdF(4): Ln(3+) (Ln = Ce, Eu, Tb and Dy) nanoparticles (NPs) via a solution-based route at room temperature. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) and cathodoluminescence (CL) spectra are used to characterize the samples. The results indicate that the use of water-diethyleneglycol (DEG) solvent mixture as the reaction medium not only allows facile particle size control but also endows the as-prepared samples with good water-solubility. In particular, the mean size of NPs is monotonously reduced with the increase of DEG content, from 215 to 40 nm. The luminescence intensity and absolute quantum yields for KGdF(4): Ce(3+), Tb(3+) NPs increase remarkably with particle sizes ranging from 40 to 215 nm. Additionally, we systematically investigate the magnetic and luminescence properties of KGdF(4): Ln(3+) (Ln = Ce, Eu, Tb and Dy) NPs. They display paramagnetic and superparamagnetic properties with mass magnetic susceptibility values of 1.03 × 10(-4) emu g(-1)·Oe and 3.09 × 10(-3) emu g(-1)·Oe at 300 K and 2 K, respectively, and multicolor emissions due to the energy transfer (ET) process Ce(3+)→ Gd(3+)→ (Gd(3+))(n)→ Ln(3+), in which Gd(3+) ions play an intermediate role in this process. Representatively, it is shown that the energy transfer from Ce(3+) to Tb(3+) occurs mainly via the dipole-quadrupole interaction by comparison of the theoretical calculation and experimental results. This kind of magnetic/luminescent dual-function materials may have promising applications in multiple biolabels and MR imaging.