Hematin and CuII control generations of hydroperoxyl and superoxide radicals to activate galactose oxidase for 5-hydroxymethylfurfural conversion.

We present a significant finding that Cu(II) ions can activate hematin (Hem) to generate more HOO⋅ and O2⋅- radicals from the decomposition of H2O2. Galactose oxidase (GO) and hematin have been simultaneously immobilized by coordinating to Cu(II) ions (GO&Hem@Cu(II)). The radicals HOO⋅ and O2⋅- and dioxygen O2 can be in situ generated from the byproduct H2O2 by the Cu(II)-activated hematin. Ample experimental evidence supports the discovery that the immobilized GO is reactivated by the in situ generated HOO⋅ and O2⋅-. For the conversion of 100 mM 5-hydroxymethylfurfural (HMF) in water, GO&Hem@Cu(II) (0.8 mg/mL GO encapsulated) has achieved a 99.5% conversion within 180 min. In contrast, 0.8 mg/mL free GO M3-5 variant (ACS Catalysis 2018, 8, 4025) has achieved an HMF conversion of 17.3%. For the conversion of HMF (1,000 mM) by GO&Hem@Cu(II) (4 mg/mL GO encapsulated), the HMF conversion is 98.8% after 8 h reaction.

Cobalt Doped in Zn-MOF-5 Nanoparticles to Regulate Tumor Microenvironment for Tumor Chemo/Chemodynamic Therapy.

Metal-organic frameworks are often used as a chemotherapeutic drug carrier due to their diverse metal sites and good acid degradation ability. Herein Co-doped Zn-MOF-5 nanoparticles with a high Co doping rate of 60% were synthesized for chemo-chemodynamic synergistic therapy of tumor. Co ions can mediate chemodynamic therapy through Fenton-like reaction and regulate the tumor microenvironment by consuming the reduced glutathione. The CoZn-MOF-5 shows high drug loading capacity with doxorubicin loading rate of 72.8%. The CoZn-MOF-5@PEG@DOX nanodrugs has a strong killing effect on 4T1 cancer cells, suggesting the chemo-chemodynamic synergistic effect on tumor therapy.

Effects of BMI1 Gene on Regulating Apoptosis, Invasion, and Migration of HEC-1B Cells Induced by Ionizing Radiation.

The aim of this study was to examine the role of B lymphoma Moloney murine leukemia virus insertion region 1 (BMI1) gene in regulating the apoptosis, invasion, and migration of human endometrial adenocarcinoma cell line (HEC-1B) cells induced by ionizing radiation. The expression of BMI1 mRNA was detected by quantitative real-time polymerase chain reaction (qRT-PCR), and the positive expression of BMI1 was detected by immunohistochemistry (IHC) staining. HEC-1 B cells were randomly divided into three groups: control group, BMI1 overexpression group, and BMI1 inhibitor group. Cell proliferation was detected by cell counting kit-8 (CCK-8); cell migration and invasion were detected by Transwell test; cell apoptosis was detected by flow cytometry; and the expression of MMP2, MMP7, MMP9, Rock1, RhoA, P53, P21, and Bax protein was detected by the western blot. The results suggested that the expression of BMI1 mRNA and tissue positive in endometrial cancer tissues was increased significantly. After ionizing radiation, compared with the control group, the proliferation, cell migration, and invasion of HEC-1B cells were increased significantly in the BMI1 overexpression group, while the proliferation, cell migration, and invasion of HEC-1B cells were decreased significantly in BMI1 inhibitor group. The apoptosis rate of BMI1 overexpression group was decreased significantly, while the BMI1 inhibitor group was increased significantly. The levels of MMP2, MMP7, MMP9, Rock1, RhoA and p53, p21, Bax protein in BMI1 overexpression group were significantly increased, while the levels of MMP2, MMP7, MMP9, Rock1, RhoA and p53, p21, Bax protein in BMI1 inhibitor group were significantly decreased. BMI1 is highly expressed in endometrial cancer tissues, and inhibiting BMI1 expression can reduce the proliferation, migration, and invasion of HEC-1B cells after ionizing radiation and promote apoptosis, which offers new insights into the clinical radiotherapy of tumors.

Fabrication of a Fibrous Metal-Organic Framework and Simultaneous Immobilization of Enzymes.

A nanorod-like lanthanum metal-organic framework (LaMOF) was synthesized in aqueous solution by coordinating La(III) to the ligand 1,3,5-benzenetricarboxylic acid. The fibrous LaMOF was fabricated by splitting the nanorod-like LaMOF in a solution of d-amino acid oxidase, and the enzyme was immobilized simultaneously. Based on SEM and TEM images, STEM mapping, and spectra of XPS and FTIR, the mechanism of formation of the fibrous LaMOF and the distinct interfacial phenomena have been elucidated. The fabrication of the fibrous LaMOF and simultaneous immobilization of the enzyme were carried out in aqueous solutions at room temperature, without using any organic solvent. It is a clean and time- and energy-effective process. This work presents a distinct and clean methodology for the fabrication of the fibrous MOF. Potentially, the environmentally benign methodology can be extended to immobilize other enzymes.

Heparin Immobilized on Multiwalled Carbon Nanotubes for Catalytic Conversion of Fructose in Water with High Yield and Selectivity.

Being a member of the glycosaminoglycan family of carbohydrates, native heparin is a highly sulfated polysaccharide. Herein, heparin was grafted onto polydopamine (PDA)- and poly(ethylene imine) (PEI)-coated multiwalled carbon nanotubes (MWCNTs) (heparin-PEI@PDA@MWCNT). The immobilized heparin consists of a sulfated repeating disaccharide unit, conferring a unique microenvironment when catalyzing fructose dehydration into 5-hydroxymethylfurfural (HMF). The hydrogen bonding interactions naturally occur between the disaccharide unit of heparin and the monosaccharide fructose, and the adjacent sulfonic acid groups catalyze the fructose dehydration. The reactions were performed in water, and heparin-PEI@PDA@MWCNT achieved an HMF yield of 46.2% and an HMF selectivity of 82.2%. For the dehydration of fructose in water, heparin-PEI@PDA@MWCNT exhibits advantages over published heterogeneous catalysts on the basis of HMF yield and HMF selectivity. Three aspects contribute to the environmentally benign processing: (1) the catalyst heparin is a natural sulfated polysaccharide; (2) the catalysis is carried out in water and not in organic solvents; and (3) fructose can be produced from a biomass resource.

Immobilization of R-ω-transaminase on MnO2 nanorods for catalyzing the conversion of (R)-1-phenylethylamine.

R-É·-transaminases transfer an amino group from an amino donor (e.g. (R)-1-phenylethylamine) onto an amino acceptor (e.g. pyruvate), resulting a co-product (e.g. d-alanine). This work intends to immobilize R-É·-Transaminase on MnO2 nanorods to achieve multienzyme catalysis. R-É·-Transaminase (RTA) and d-amino acid oxidase (DAAO) have been fused to an elastin-like polypeptide (ELP) separately through genetic engineering of the enzymes. ELP-RTA and ELP-DAAO have been separately immobilized on polydopamine-coated MnO2 nanorods. When the two immobilized enzymes were used together in one pot, the transformation of (R)-1-phenylethylamine was catalyzed by the immobilized ELP-RTA, and the co-product d-alanine was converted back to pyruvate under the catalysis of the immobilized ELP-DAAO, achieving the recycling of pyruvate in situ. Thus pyruvate was maintained at a low concentration in order to reduce its negative effect. On the other hand, the generated H2O2 of ELP-DAAO was decomposed by the MnO2 nanorods, and the evolved oxygen oxidized the reduced cofactors of ELP-DAAO. Forming the circles of hydrogen peroxide→oxygen→hydrogen peroxide accelerated the deamination reaction. The highly efficient conversion of the co-product d-alanine back to pyruvate accelerated the forming of the pyruvate→d-alanine→pyruvate cycle between the two immobilized enzymes. The coordination of the pyruvate→d-alanine→pyruvate and hydrogen peroxide→oxygen→hydrogen peroxide cycles accelerated the transformation of (R)-1-phenylethylamine. As a result, As a result, the immobilized enzymes achieved a conversion of 98±1.8% in comparison to 69.6±1.2% by free enzymes.

A two-enzyme immobilization approach using carbon nanotubes/silica as support.

Multiple enzyme mixtures are attractive for the production of many compounds at an industrial level. We report a practical and novel approach for coimmobilization of two enzymes. The system consists of a silica microsphere core coated with two layers of individually immobilized enzymes. The model enzymes α-amylase (AA) and glucoamylase (GluA) were individually immobilized on carbon nanotubes (CNTs). A CNT-GluA layer was formed by adsorbing CNT-GluA onto silica microsphere. A sol-gel layer with entrapped CNT-AA was then formed outside the CNT-GluA/silica microsphere conjugate. The coimmobilized α-amylase and glucoamylase exhibited 95.1% of the activity of the mixture of free α-amylase and glucoamylase. The consecutive use exhibited a good stability of the coimmobilized enzymes. The developed approach demonstrates advantages, including controlling the ratio of coimmobilized enzymes in an easy way, facilitating diffusion of small molecules in and out of the matrix, and preventing the leaching of enzymes.

Sodium hexadecyl sulfate as an interfacial substance adjusting the adsorption of a protein on carbon nanotubes.

Carbon nanotubes (CNTs) were functionalized with sodium hexadecyl sulfate (SHS). The lysozyme adsorbed on the SHS-CNTs exhibited a higher activity than that immobilized on the nonfunctionalized CNTs. To explain the experimental results and explore the mechanism of lysozyme adsorption, large-scale molecular dynamics simulations have been performed for a four-component system, including lysozyme, SHS, CNTs in explicit water. It has been found that the assembled SHS molecules form a soft layer on the surface of CNTs. The interactions between lysozyme and SHS induce the rearrangement of SHS molecules, forming a saddle-like structure on the CNT surface. The saddle-like structure fits the shape of the lysozyme, and the active-site cleft of the lysozyme is exposed to the water phase. Whereas, for the lysozyme adsorbed on the nonfunctionalized CNT, due to the hydrophobic interactions, the active-site cleft of the enzyme tends to face the wall of the CNT. The results of this work demonstrate that the SHS molecules as the interfacial substance have a function of adjusting the lysozyme with an appropriate orientation, which is favorable for the lysozyme having a higher activity.

Molecular mechanism of the interactions between inhibitory tripeptides and angiotensin-converting enzyme.

Angiotensin I-converting enzyme (ACE) is a key therapeutic target for combating hypertension and related cardiovascular diseases. ACE inhibitory peptides offer the prospect of enhanced potency, high specificity, and no or low side effect. The ACE inhibitory tripeptides LKP and IKP differ from each other by one amino acid but their inhibitory potencies for ACE differ significantly. To uncover the molecular mechanism underlying this phenomenon, we have investigated the tripeptide/ACE complexes through molecular dynamics simulations coupled with quantum mechanical simulations. Comparative structural analysis has identified a hydrophobic subsite in the active site of cACE comprising hydrophobic residues Val379, Val380, Phe457, Phe527, and Ala418. The interactions of the side chains of Leu and Ile with the hydrophobic residues determine the binding positions of N-terminal residues of the tripeptides, that influence the interaction of the residues of tripeptides with the active site of cACE. This work presents the molecular mechanism of the interactions between the inhibitory tripeptides and ACE, and deciphers the structural basis for the high affinity LKP inhibition of ACE.

Synthesis of bioethanol from biomass-derived syngas over carbon nanotube/silica supported catalyst.

Multi-walled carbon nanotubes (MWNTs) were functionalized with pyrogallol and used in a composite with silica as a support for a Cu-Co based catalyst. The catalysts were characterized using X-ray diffraction, transmission electron microscopy, and H(2) temperature programmed reduction. The effects of pyrogallol and the weight ratio of silica to MWNTs on the performance of the catalyst were studied in a fixed bed reactor. The increase of the amount of MWNTs in the catalyst support was found to favor decreased methanol production and increased production of C2+ alcohols. Using pyrogallol in catalyst preparation was also found to increase the production of C2+ alcohols. It was concluded that pyrogallol improves the distribution and uniformity of metal particles on the support, decreases the size of metal particles and increasing the rate of catalytic reduction.

Lipase immobilized on magnetic multi-walled carbon nanotubes.

Magnetic iron oxide nanoparticles were loaded onto the surfaces of multiwalled carbon nanotubes (MWNTs) by the impregnation method. The obtained magnetic nanotubes were characterized with high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Yarrowia lipolytica lipase was covalently immobilized on the magnetic MWNTs (M-MWNTs). M-MWNT-lipase was characterized with XPS spectra and XRD patterns. The structural change of the immobilized lipase was analyzed through circular dichroism spectroscopy. M-MWNT-lipase was utilized for the resolution of (R, S)-1-phenyl ethanol in the organic solvent of heptane. Compared to the native lipase, the lipase immobilized on M-MWNTs has significantly improved its enzymatic activity for the resolution of (R, S)-1-phenyl ethanol in heptane. M-MWNT-lipase can be easily recovered after catalysis. In addition, the effect of sonication time on the catalytic activity was also investigated. It is found that, up to 30min sonication, the catalysis by M-MWNT-lipase is almost not affected. While, the catalytic activity of the native lipase is decreased with sonication time.

Enzymes immobilized on carbon nanotubes.

Enzyme immobilizations on carbon nanotubes for fabrication of biosensors and biofuel cells and for preparation of biocatalysts are rapidly emerging as new research areas. Various immobilization methods have been developed, and in particular, specific attachment of enzymes on carbon nanotubes has been an important focus of attention. The method of immobilization has an effect on the preservation of the enzyme structure and retention of the native biological function of the enzyme. In this review, we focus on recent advances in methodology for enzyme immobilization on carbon nanotubes.