Garcinolic Acid Distinguishes Between GACKIX Domains and Modulates Interaction Networks

Posted on by
Garcinolic Acid Distinguishes Between GACKIX Domains and Modulates Interaction Networks

Garcinolic acid is a topologically complex natural product derived from Garcinia hanburyi. It engages the KIX domain in the master coactivator CBP/p300 selectively over other closely related motifs and in doing so disrupts CBP/p300 KIX protein-protein interactions. In the cellular context this enables downregulation of transcriptional circuits essential for cMyb-dependent leukemias.


Abstract

Natural products are often uniquely suited to modulate protein-protein interactions (PPIs) due to their architectural and functional group complexity relative to synthetic molecules. Here we demonstrate that the natural product garcinolic acid allosterically blocks the CBP/p300 KIX PPI network and displays excellent selectivity over related GACKIX motifs. It does so via a strong interaction (K D 1 μM) with a non-canonical binding site containing a structurally dynamic loop in CBP/p300 KIX. Garcinolic acid engages full-length CBP in the context of the proteome and in doing so effectively inhibits KIX-dependent transcription in a leukemia model. As the most potent small-molecule KIX inhibitor yet reported, garcinolic acid represents an important step forward in the therapeutic targeting of CBP/p300.

Caulobacter segnis Dioxygenase CsO2: A Practical Biocatalyst for Stilbenoid Ozonolysis

Posted on by
Caulobacter segnis Dioxygenase CsO2: A Practical Biocatalyst for Stilbenoid Ozonolysis

The Caulobacter segnis dioxygenase has been employed for the enzymatic alkene cleavage of several stilbenoids, thus generating the corresponding aldehydes. CsO2-mediated ozonolysis represents a greener, safer, and more selective process with respect to conventional chemistry. To further assess the CsO2 usability as a preparative biocatalyst, a 50–mL scale biotransformation of resveratrol has been carried out obtaining the corresponding aldehydes with excellent yields (98 %), rapid reaction times (1.5 h) and unprecedented substrate-to-catalyst ratio (5 103).


Abstract

Ozonolysis is a useful as well as dangerous reaction for performing alkene cleavage. On the other hand, enzymes are considered a more sustainable and safer alternative. Among them, Caulobacter segnis dioxygenase (CsO2) known so far for its ability to catalyze the coenzyme-free oxidation of vinylguaiacol into vanillin, was selected and its substrate scope evaluated towards diverse natural and synthetic stilbenoids. Under optimized conditions, CsO2 catalyzed the oxidative cleavage of the C=C double bonds of various trans-stilbenes, providing that a hydroxyl moiety was necessary in para-position of the phenyl group (e. g., resveratrol and its derivatives) for the reaction to take place, which was confirmed by modelling studies. The reactions occurred rapidly (0.5–3 h) with high conversions (95–99 %) and without formation of by-products. The resveratrol biotransformation was carried out on 50–mL scale thus confirming the feasibility of the biocatalytic system as a preparative method.

Synergistic Effect Enhancing Baeyer‐Villiger Oxidation Performance of Resin‐Derived‐Carbon Supported FeCe Bimetallic Catalyst

Posted on by
Synergistic Effect Enhancing Baeyer-Villiger Oxidation Performance of Resin-Derived-Carbon Supported FeCe Bimetallic Catalyst

Benefiting from the synergistic effect of supported bimetallic CeFe which induces higher metal dispersion and higher content of reactive oxygen, and the buffering effect of resin-derived-carbon on free radicals, the aerobic oxidation of cyclohexanone to ϵ-caprolactone (ϵ-CL) is performed over CeFe@RDC-x, and the catalytic efficiency is significantly improved. Especially, when solvent-free and green solvents (such as ethyl acetate) are used, excellent catalytic conversion effects are achieved.


Abstract

Upgrading cyclohexanone to ϵ-caprolactone (ϵ-CL) is of great importance to the synthesis of high value-added downstream chemicals and the reduction of foam plastic. The catalytic synthesis of ϵ-CL from cyclohexanone through O2/aldehyde method is an environmentally benign one-pot tandem reaction without using peroxy acid, balancing the requirements of safety and efficiency. However, due to lack of elaborate design and collaboration of multiple active sites for catalysts, the catalytic efficiency of O2/aldehyde method still remains to be improved. Herein, a pitaya-like catalyst (CeFe@RDC-3) with Ce and Fe highly dispersed on resin-derived-carbon is synthesized through high temperature self-assembly. On this bimetallic catalyst, high yield (97 %) of ϵ-CL is achieved through aerobic oxidation of cyclohexanone with only 1.5 equivalent benzaldehyde. Moreover, considerable yields of ϵ-CL, 88.3 % and 74.7 %, respectively, are also obtained over CeFe@RDC-3 with green solvent (EtOAc) or even without solvent. No loss of activity is observed after five successive cycles, demonstrating high stability of CeFe@RDC-3. The mechanism study reveals that the high performance of CeFe@RDC-3 is ascribed to the Ce−Fe bimetallic synergy, uniform metal dispersion, abundant active oxygen and stabilizing effect of resin-derived-carbon to free radicals. This work provides prospect for a green, safe and low-cost strategy for Baeyer-Villiger process.

Engineering an O‐methyltransferase for the Regioselective Biosynthesis of Hesperetin Dihydrochalcone

Posted on by
Engineering an O-methyltransferase for the Regioselective Biosynthesis of Hesperetin Dihydrochalcone

Engineering enhanced regioselectivity: Directed evolution of an O-methyltransferase resulted in variants with increased regioselectivity for the para-methylation of dihydrochalcones and related catecholic compounds (regioisomeric ratio up to 99 : 1). This allows now the biocatalytic production of the taste active hesperetin dihydrochalcone.


Abstract

Directed evolution of the O-methyltransferase ZgOMT from Zooshikella ganghwensis focusing on active site residues resulted in highly regioselective biocatalysts (regioisomeric ratios up to 99 : 1) for the preparation of the taste active hesperetin dihydrochalcone and related compounds. These newly constructed enzyme variants provide an attractive synthesis route for para-methylation of catechol scaffolds, which is challenging to perform with high regioselectivity utilizing wild-type O-methyltransferases.

Optimization of Biodiesel Production from Waste Cooking Oil Using Nano Calcium Oxide Catalyst

Posted on by
Optimization of Biodiesel Production from Waste Cooking Oil Using Nano Calcium Oxide Catalyst

Biodiesel is an alternative to fossil diesel fuel derived from sustainable biological resources. Biodiesel production from waste cooking oil and methanol in the presence of a nanosized CaO catalyst was studied. Transesterification was performed at different times, temperatures, and methanol/oil ratios, and response surface methodology was used to predict optimum parameters for biodiesel production.


Abstract

The use of nano calcium oxide as a catalyst in biodiesel production has gained attention due to its high catalytic activity, low cost, and environmental friendliness. It efficiently converts triglycerides to fatty acids and methyl esters. In the present study, nano CaO was prepared by precipitation and characterized by various techniques. The results showed that the nano CaO has high purity, nanoscale crystal size, good thermal stability, and high specific surface area. Biodiesel was produced by transesterification from waste cooking oil, methanol, and the nano catalyst. Response surface methodology was applied to predict the optimum parameters for the production of the biodiesel based on its yield. The produced biodiesel was characterized by FTIR spectroscopy and GC-MS and evaluated according to ASTM D6571.

Theoretical Analysis of Metals Supported on Tungsten Oxide Nanowires (W18O49) for Water Dissociation Reaction

Posted on by
Theoretical Analysis of Metals Supported on Tungsten Oxide Nanowires (W18O49) for Water Dissociation Reaction

Applying the density functional theory method, W18O49 was developed for catalyst support on Pt, Pd, Ni, Ir, Ag, and Rh metal atoms for the oxygen evolution reaction. Various adsorbates that are intermediate products in this reaction were tested for adsorption on metal catalysts. Gibbs free energy diagrams were also developed to analyze the potential of the catalyst and W18O49.


Abstract

Pt is the cause of the high total cost of fuel cells and electrolyzers, leading to difficult commercialization. Here, various types of metal atoms, i.e., Pt, Pd, Ni, Ir, Ag, and Rh, suitable for catalysts are used and supported by W18O49 nanowires for oxygen evolution reaction (OER) by the density functional theory (DFT) method. Four adsorbate molecules involved in OER were tested on adsorption energy: OH, O, OOH, and OO. Although the adsorption energy of these adsorbate molecules indicates that W18O49 has low adsorption energy, the Gibbs free energy diagram demonstrates that W18O49 has high OER reaction energy. Pt, Pd, Ni, and Rh have the lowest Gibbs energy to initiate the reaction and reasonable Gibbs free energy for other OER reactions. Bimetallic or trimetallic active sites can be developed along with selecting other metals with Pt, Pd, Rh, and Ni to reduce the Gibbs free energy difference for the decomposition of OH to O and OOH to H2O. Ag metal can also be applied as a second or third metal because Ag exhibits a relatively low Gibbs free energy difference in the O to OOH step. A selectivity study of each step on bimetallic and trimetallic active sites needs to be performed.

Structural Description of Chiral E‐Tiling DNA Nanotubes with the Chiral Indices (n,m) and Handedness Defined by Microscopic Imaging

Posted on by
Structural Description of Chiral E-Tiling DNA Nanotubes with the Chiral Indices (n,m) and Handedness Defined by Microscopic Imaging

The chiral index theory, widely used in carbon nanotubes, has been introduced to describe the chiral structures of E-tiling DNA nanotubes precisely. In particular, we define a general equation of tube curvature with a clear physical picture by modifying its mathematical definition. Furthermore, we summarize the recent progress on defining the left- or right-handedness of E-tiling DNA nanotubes through differentiating their inside and outside surfaces by fluorescence or electron or atomic force microscopic imaging.


Abstract

In structural DNA nanotechnology, E-tiling DNA nanotubes are evidenced to be homogeneous in diameter and thus have great potential in biomedical applications such as cellular transport and communication, transmembrane ion/molecule channeling, and drug delivery. However, a precise structural description of chiral DNA nanotubes with chiral parameters was lacking, thus greatly hindering their application breadth and depth, until we recently raised and partly solved this problem. In this perspective, we summarize recent progress in defining the chiral indices and handedness of E-tiling DNA nanotubes by microscopic imaging, especially atomic force microscopy (AFM) imaging. Such a detailed understanding of the chiral structures of E-tiling DNA nanotubes will be very helpful in the future, on the one hand for engineering DNA nanostructures precisely, and, on the other, for realizing specific physicochemical properties and biological functions successfully.