Rh(III)-Catalyzed One-Step Synthesis of ortho-Alkynylated Perylene Imide Dyes: Optical and Electrochemical Properties of New Derivatives

A one-step Rh-catalyzed site-selective ortho-C−H alkynylation of perylene as well as naphthalene mono- and diimides is reported. A single step regioselective access to ortho-C−H alkynylated derivatives of these ryleneimides not only increases the step economy of the ortho-functionalization on these dyes but also provides a quick access route towards highly functionalized dyes that have potential optoelectronic applications. Increased solubility of tetra(triisopropylsilyl)acetylenyl PDIs in organic solvents greatly enhances their utility for further derivatization.     

Coordination-based self-assembled capsules (SACs) for protein,CRISPR–Cas9, DNA and RNA delivery

Biologics, such as functional proteins and nucleic acids, have recently dominated the drug market and comprise seven out of the top 10 best-selling drugs. Biologics are usually polar, heat sensitive, membrane impermeable and subject to enzymatic degradation and thus require systemic routes of administration and delivery. Coordination-based delivery vehicles, which include nanosized extended metal–organic frameworks (nMOFs) and discrete coordination cages, have gained a lot of attention because of their remarkable biocompatibility, in vivo stability, on-demand biodegradability, high encapsulation efficiency, easy surface modification and moderate synthetic conditions. Consequently, these systems have been extensively utilized as carriers of biomacromolecules for biomedical applications. This review summarizes the recent applications of nMOFs and coordination cages for protein, CRISPR–Cas9, DNA and RNA delivery. We also highlight the progress and challenges of coordination-based platforms as a promising approach towards clinical biomacromolecule delivery and discuss integral future research directions and applications.

SACs can be efficiently used to load biologics such as proteins, CRISPR–Cas9, DNA and RNA and release them on-demand.     

Membrane oscillations involving electrokinetic phenomena

Semi theoretical models have been proposed to account for the mechanism of membrane oscillations involving, electrokinetic phenomena in systems where (i) concentration difference deltaC is finite and deltaP is varying but the current is fixed, and (ii) deltaC=0, pressure difference deltaP is fixed across the membrane and imposed current is fixed. The formalism leads to the van der Pol equation in both cases. Computer simulation has also been attempted, which indicates oscillations in the former case.     

Dynamic Hydrogen-Bonded Zinc Adeninate Framework (ZAF) for Immobilization of Catalytic DNA

Effective immobilization and delivery of genetic materials is at the forefront of biological and medical research directed toward tackling scientific challenges such as gene therapy and cancer treatment. Herein we present a biologically inspired hydrogen-bonded zinc adeninate framework (ZAF) consisting of zinc adeninate macrocycles that self-assemble into a 3D framework through adenine-adenine interactions. ZAF can efficiently immobilize DNAzyme with full protection against enzyme degradation and physiological conditions until it is successfully delivered into the nucleus. As compared to zeolitic imidazolate frameworks (ZIFs), ZAFs are twofold more biocompatible with a significant loading efficiency of 96 %. Overall, our design paves the way for expanding functional hydrogen-bonding-based systems as potential platforms for the loading and delivery of biologics.     

Catalytic action of Mn‐superoxide dismutase in scavenging superoxide radical anion by double hydrogen abstraction from dihydrolipoic acid: A theoretical study

The mechanism of scavenging superoxide radical anion ( ) by dihydrolipoic acid (diLA) in absence and presence of the enzyme Manganese‐superoxide dismutase (Mn‐SOD) has been investigated using density functional theory. Mn‐SOD was modelled by a complex of a manganese cation (Mn²⁺) bonded to three similar molecules having a histidine ring each and a water molecule. It has been shown that the scavenging mechanism involves double hydrogen abstraction by from different pairs of neighboring sites of diLA. It has been found that diLA alone cannot scavenge superoxide radical anions efficiently as the barrier energies involved in the reactions are very high. However, in presence of Mn‐SOD, owing to its catalytic action, the corresponding reactions become barrierless due to which superoxide radical anions would be scavenged highly efficiently. H₂O₂ formed from superoxide radical anion due to double hydrogen abstraction from diLA is scavenged by diLA alone barrierlessly without involving Mn‐SOD or any other catalyst.     

Differential content of secondary metabolites in diploid and tetraploid cytotypes of Siegesbeckia orientalis L.

Siegesbeckia orientalis L. is an annual herb widely distributed throughout the world and has many medicinal properties. In Chinese traditional system, it is popularly known as Xi-Xian and used for its anti-inflammatory properties. In the present study, two cytotypes (diploid and tetraploid) have been investigated for their secondary metabolites. The different plant parts have been explored in terms of total phenolics, total flavonoids, DPPH radical scavenging acitivity and total antioxidant capacity. Out of different plant parts, leaves have the maximum amount of secondary metabolites and antioxidant potential. HPTLC technique has been applied to quantify six marker compounds in the two cytotypes. Tetraploid cytotype has been compared with diploid cytotype, which shows that tetraploid has the maximum amount of studied secondary metabolites with high antioxidant potential.     

Quantitative Prediction of Rate Constants for Aqueous Racemization To Avoid Pointless Stereoselective Syntheses

Racemization has a large impact upon the biological properties of molecules but the chemical scope of compounds with known rate constants for racemization in aqueous conditions was hitherto limited. To address this remarkable blind spot, we have measured the kinetics for racemization of 28 compounds using circular dichroism and ¹H NMR spectroscopy. We show that rate constants for racemization (measured by ourselves and others) correlate well with deprotonation energies from quantum mechanical (QM) and group contribution calculations. Such calculations thus provide predictions of the second‐order rate constants for general‐base‐catalyzed racemization that are usefully accurate. When applied to recent publications describing the stereoselective synthesis of compounds of purported biological value, the calculations reveal that racemization would be sufficiently fast to render these expensive syntheses pointless.     

Nitrile Metabolizing Enzymes in Biocatalysis and Biotransformation

Nitrile metabolizing enzymes, i.e., aldoxime dehydratase, hydroxynitrile lyase, nitrilase, nitrile hydratase, and amidase, are the key catalysts in carbon nitrogen triple bond anabolism and catabolism. Over the past several years, these enzymes have drawn considerable attention as prominent biocatalysts in academia and industries because of their wide applications. Research on various aspects of these biocatalysts, i.e., sources, screening, function, purification, molecular cloning, structure, and mechanisms, has been conducted, and bioprocesses at various scales have been designed for the synthesis of myriads of useful compounds. This review is focused on the potential of nitrile metabolizing enzymes in the production of commercially important fine chemicals such as nitriles, carboxylic acids, and amides. A number of opportunities and challenges of nitrile metabolizing enzymes in bioprocess development for the production of bulk and fine chemicals are discussed.