Covalent Immobilization of Proteins on 3D Poly(acrylic acid) Brushes: Mechanism Study and a More Effective and Controllable Process

Polymeric brushes have emerged as a novel 3D material platform that provides great amounts of binding sites for biomolecules. This paper investigates the covalent immobilization mechanism of protein by spherical poly­(acrylic acid) brushes (SPAABs) in the widely adopted <i>N</i>-hydroxysuccinimide/<i>N</i>-(3-dimethyl-aminopropyl)-<i>N</i>′-ethylcarbodiimide hydrochloride (NHS/EDC) process. It was discovered that electrostatic interaction plays a crucial role in the covalent immobilization of protein. Due to the existence of 3D architecture and “Donnan effect”, SPAABs exhibit quite different immobilization kinetics in comparison with conventional 2D materials. Under conditions favorable to electrostatic interaction, the effect of “electrostatic interaction induced covalent binding” was observed as a result of competitive immobilization by physical adsorption and chemical binding. On the basis of the mechanism study, a new “chemical conjugation after electrostatic entrapment” (CCEE) method was developed which set the chemical and physical immobilization process apart. A more effective and well-defined covalent immobilization was achieved. And the binding capacity can be tuned in a wide range (0–4.2 mg protein/mg SPAABs) with a high level of control

Optoelectronic Properties of &alpha;-MoO3 Tuned by H Dopant in Different Concentration

The optoelectronic properties of layered &alpha;-MoO3 are greatly limited due to its wide band gap and low carrier concentration. The insertion of hydrogen (H) can effectively tune the band structure and carrier concentration of MoO3. Herein, first-principles calculations were performed to unravel the physical mechanism of a H-doped &alpha;-MoO3 system. We found that the modulation of the electronic structure of H-doped MoO3 depends on the doping concentration and position of the H atoms. It was found that the band gap decreases at 8% doping concentration due to the strong coupling between Mo-4d and O-2p orbits when H atoms are inserted into the interlayer. More interestingly, the band gap decreases to an extreme due to the Mo-4d orbit when all the H atoms are inserted into the intralayer only, which has a remarkable effect on light absorption. Our research provides a comprehensive theoretical discussion on the mechanism of H-doped &alpha;-MoO3 from the doping positions and doping concentrations, and offers useful strategies on doping modulation of the photoelectric properties of layered transition metal oxides