NiFe MOF modified BiVO4 photoanode with strong π-π conjugation enhances built-in electric field for boasting photoelectrochemical water oxidation

The photoelectrochemical (PEC) performance ofBiVO4 is limited by sluggish kinetics and poor stability. In this work, a novel high-performance BiVO4/NiFe MOF(BPDC) photoanode is constructed by loading NiFe MOF with biphenyl-4,4'-dicarboxylic acid (BPDC) as an organic ligand on BiVO4 by a simple one-step hydrothermal method. The XPS, OCP, UPS, and KPFM show that the enhanced π-π conjugation effect causes more electrons transfer from the BiVO4 to the MOFs and affects the magnitude of the work function, leading to a strong built-in electric field to drive carrier separation and migration. Therefore, the BiVO4/NiFe MOF(BPDC) has a strong hole extraction and carrier separation capability to enhance photoelectrochemical water oxidation and improve photostability. The BiVO4/NiFe MOF(BPDC) photoanode has an enhanced photocurrent density of 4.16 mA cm-2 at 1.23 VRHE, which is 4.33 times higher than that of the pure BiVO4 (0.96 mA cm-2) photoanode with a negative shift of 376 mV in the onset potential plot, exhibiting excellent photostability of 7 h at 1.23 VRHE. This work demonstrates that the composite photoanodes constructed by BiVO4 and the MOFs with strong π-π conjugation are promising, which provides an effective strategy for the preparation of efficient and stable photoanodes.

Phenylalanine 314 is essential for the activity of maltogenic amylase from Corallococcus sp. EGB

Maltogenic amylase CoMA from Corallococcus sp. strain EGB catalyzes the hydrolysis and transglycosylation of maltooligosaccharides and soluble starch into maltose, the sole hydrolysate. This process yields pure maltose with potentially wide applications. Here, we identified and evaluated the role of phenylalanine 314 (F314), a key amino acid located near the active center, in the catalytic activities of the CoMA. Site-directed mutagenesis analysis showed that the activity of a F314L mutant on potato starch substrate decreased to 26% of that of wild-type protein. Compared with the wild-type, F314L exhibited similar substrate specificity, hydrolysis pattern, pH, and temperature requirements. Circular dichroism spectrum data showed that the F314L mutation did not affect the structure of the folded protein. In addition, kinetic analysis demonstrated that F314L exhibited an increased K_m value with lower substrate affinity. Homology modeling showed that the benzene ring structure of F314L was involved in π-π conjugation, which might potentially affect the affinity of CoMA toward starch. Taken together, these data demonstrated that F314 is essential for the hydrolytic activity of the CoMA from Corallococcus sp. strain EGB.

A π-π conjugation-containing soft and conductive injectable polymer hydrogel highly efficiently rebuilds cardiac function after myocardial infarction

Previous studies suggested that a stiffer hydrogel system exhibited a better performance to promote heart function after myocardial infarction (MI). However, the nature of myocardium, a tissue that alternately contracts and relaxes with electrical impulses, leads us to hypothesize that a soft and conductive hydrogel may be in favor of mechanical and electrical signals transmission to enhance heart function after MI. In this work, π-π conjugation interaction was first employed to produce a soft injectable hydrogel with conductive property. Melamine with π-π conjugation ring was used as a core to synthesize a multi-armed crosslinker PEGDA700-Melamine (PEG-MEL), which could crosslink with thiol-modified hyaluronic acid (HA-SH) to form an injectable hydrogel rapidly. By incorporating graphene oxide (GO), the injectable PEG-MEL/HA-SH/GO hydrogel exhibited a soft (G' = 25 Pa) and anti-fatigue mechanical property and conductive property (G = 2.84 × 10^-4 S/cm). The hydrogel encapsulating adipose tissue-derived stromal cells (ADSCs) was injected into MI area of rats. The significant increase in α-Smooth Muscle Actin (α-SMA) and Connexin 43 (Cx43) expression confirmed that the gel efficiently promoted the transmission of mechanical and electrical signals. Meanwhile, a significant improvement of heart functions, such as distinct increase of ejection fraction (EF), smaller infarction size, less fibrosis area, and higher vessel density, was achieved.