Rapid cyclopeptide analysis by microwave enhanced Akabori reaction

The application of microwave assisted modification of the Akabori hydrazinolysis reaction has been found to cleave cyclic oligopeptides in a selective fashion to produce mainly the hydrazide of a specific linear peptide. This ring cleavage requires a few minutes of reaction in a domestic microwave oven. The linear peptide hydrazide can be analyzed by ESI-MS/MS, FAB-MS, and FAB-MS/MS methods for the determination of the amino acid sequence.     

Reactivity Differences between Carbon Nano Onions (CNOs) Prepared by Different Methods

The carbon nanoparticles obtained from either arcing of graphite under water or thermal annealing of nanodiamonds are commonly called carbon nano onions (CNOs), or spherical graphite, as they are made of concentric fullerene cages separated by the same distance as the shells of graphite. A more careful analysis reveals some dramatic differences between the particles obtained by these two synthetic methods. Physicochemical methods indicate that the CNOs obtained from nanodiamonds (N‐CNOs) are smaller and contain more defects than the CNOs obtained from arcing (A‐CNOs). These properties explain the enhanced reactivity of the N‐CNOs in cycloaddition and oxidation reactions, as well as in reactions involving radicals. Given the easier functionalization of the N‐CNOs, they are the most obvious choice for studying the potential applications of these multi‐shelled fullerenes.     

Synergistic Substrate and Oxygen Activation in Salicylate Dioxygenase Revealed by QM/MM Simulations

Salicylate 1,2‐dioxygenase (SDO) is the first enzyme to be discovered to catalyze the oxidative cleavage of a monohydroxylated aromatic compound, namely salicylate, instead of the well‐known electron‐rich substrates. We have investigated the mechanism of dioxygen activation in SDO by QM/MM calculations. Our study reveals that the non‐heme Fe^II center in SDO activates salicylate and O₂ synergistically through a strong covalent interaction to facilitate the reductive cleavage of O₂. A covalent salicylate–Fe^II–O₂ complex is the reactive oxygen species in this case, and its electronic structure is best described as being between the two limiting cases, Fe^II?O₂ and Fe^II?O₂^.?, with partial electron transfer from the activated salicylate to O₂ via the Fe center. Thus SDO employs a synergistic strategy of substrate and oxygen activation to carry out the catalytic reaction, which is unprecedented in the family of iron dioxygenases. Moreover, O₂ activation in SDO happens without the assistance of a proton source. Our study essentially shows a new mechanistic possibility for O₂ activation.     

Carbon Dots Derived from Waste Psidium Guajava Leaves for Electrocatalytic Sensing of Chlorpyrifos

Carbon dots (CDs) modified GCE was used for the electrochemical sensing of Chlorpyrifos (CHL). The hydrothermal synthesis (200 °C for 10 h) produced CDs of 3.7 nm using Psidium guajava leaves. Square wave voltammetry was employed for the determination of CHL and the electrokinetic parameters. The reduction of CHL involved an irreversible two-electron process with heterogeneous reaction rate (k°) and formal potential (E°) of 1.21 s⁻¹ and −1.34 V respectively. The modified GCEs exhibited good repeatability (RSD 4.7 %), reproducibility (RSD 1.17 %), and sensitivity (1.30 mA μM⁻¹ cm⁻²). The detection limit and linear ranges were 1.5 nM and 0.01–1 μM, respectively. Electrochemical sensing of CHL was comparable with the HPLC (∼5 % variation).     

Cover Feature: Low-Cost and Scalable Ni-Prussian Blue Analogue//Functionalized Carbon Based Na-Ion Systems for all Climate Operations (ChemPhysChem 4/2023)

Herein, we have developed a sodium ion based aqueous energy storage device with nickel prussian-blue-analogue (Ni-PBA) positive and functionalized carbon-black negative electrodes in 1 M Na₂SO₄ electrolyte solution. The components required to develop the device, i. e., stainless steel (SS) current-collectors, absorbent-glass-mat separator, electrolyte, carbon-black, and precursors of Ni-PBA, are all environmentally benign and inexpensive. To minimize the corrosion of pristine-SS, polyaniline coating on the SS surface is applied by in situ electrodeposition method. The full cell exhibits a specific capacity of 28 mAh g⁻¹ with 90 % Coulomb efficiency (@0.2C), an energy density of 34 Wh kg⁻¹ (@20 W kg⁻¹), a power density of 100 W kg⁻¹ (@18 Wh kg⁻¹) and a good life cycle (70 % capacity-retention over 500 cycles @1.0C rate) within the 0–1.2 V window. The cell performance is further tested under variable temperatures, and 0–50 °C range is reported to be the working window for this cell.     

Synthesis,crystal structures and spectroscopic properties of two Zn(II) Schiff’s base complexes of pyridoxal

Two mononuclear zinc(II) complexes, [ZnL¹H₂Cl]Cl·2H₂O (1·Cl·2H₂O) and [ZnL²HCl]·H₂O (2·H₂O) (L¹H₂ and L²H₂ are N,N′-bis(pyridoxylidene)ethylenediamine and N,N′-bis(pyridoxylidene)1,3-propanediamine, respectively) have been synthesized and characterized by elemental analysis, FT-IR, fluorescence spectroscopy, TG–DTA and single crystal X-ray diffraction studies. The Zn(II) ion in complex 1 have a square pyramidal geometry with appreciable distortion towards trigonal bipyramid, whereas in 2 it has a geometry which is near the midpoint of square pyramid and trigonal bipyramid. The zinc atom is coordinated by two imine nitrogens, two phenolic oxygens and one chloride ion. The Zn(II) complexes show emission at 462 nm when excited at their lowest energy absorption at 372 nm.     

Aggregation-Induced Emission-Based Sensing Platform for Selective Detection of Zn2+: Experimental and Theoretical Investigations

Fluorescent chemosensors with aggregation induced emission enhancement (AIEE) emerge as promising tools in the field of sensing materials. Herein, we report the design, synthesis and applicability of a Schiff base chemosensor 1-(benzo[1,3]dioxol-4-ylmethylene-hydrazonomethyl)-naphthalen-2-ol ( Hbdhn ) of AIE characteristics that exhibits highly effective and selective response towards Zn²⁺. The sensing effect of Hbdhn was evaluated by means of absorption/emission spectra and corresponding underlying photophysical mechanisms were proposed based on extensive quantum-chemical (TD)DFT calculations. The aggregated states in different DMSO/H₂O ratios and in a presence of Zn²⁺ were examined by fluorescence lifetime measurements, dynamic light scattering and scanning electron microscopy studies. The bioimaging abilities of Hbdhn were evaluated for Zn²⁺ in HepG2 cancer cells. The results demonstrate instant, stable in time and reproducible, colorimetric turn-on response with superb selectivity and sensitivity of Hbdhn towards Zn²⁺, based on chelation enhanced fluorescence mechanism. AIEE improves further Hbdhn properties, leading to strong, long-lived fluorescence, with appearance of rod-like particles, in 90 % of water in DMSO and only 10 % of water in DMSO in the presence of Zn²⁺. All these features combined with successful biomaging studies make Hbdhn one of the most promising candidate for practical applications among recently proposed related systems.     

A Reusable Efficient Green Catalyst of 2D Cu-MOF for the Click and Knoevenagel Reaction

[Cu(CPA)(BDC)]_n (CPA = 4-(Chloro-phenyl)-pyridin-4-ylmethylene-amine; BDC = 1,4-benzenedicarboxylate) has been synthesized and structurally characterized by single crystal X-Ray diffraction measurement. The structural studies establish the copper (II) containing 2D sheet with (4,4) square grid structure. The square grid lengths are 10.775 and 10.769 Å. Thermal stability is assessed by TGA, and subsequent PXRD data establish the crystallinity. The surface morphology is evaluated by FE-SEM. The N₂ adsorption−desorption analysis demonstrates the mesoporous feature (∼6.95 nm) of the Cu-MOF. This porous grid serves as heterogeneous green catalyst with superficial recyclability and thermal stability and facilitates organic transformations efficiently such as, Click and Knoevenagel reactions in the aqueous methanolic medium.     

Separation of NCA 88Zr from proton irradiated natY target: a novel approach using low cost bio-sorbent potato peel charcoal

Separation of no-carrier-added (NCA) ⁸⁸Zr from natural yttrium target irradiated with proton beam has been studied using nature-resourced material, potato peel, which is a commonly available domestic waste. Here, an attempt has been undertaken to exploit natural resource as separating agent. Good separation of NCA ⁸⁸Zr from bulk Yttrium target could be achieved at 0.01 M HCl concentration, when extraction was carried out using 20 mg potato peel charcoal—a natural bio-sorbent. ⁸⁸Zr was extracted in the solid phase leaving behind bulk Y in the aqueous phase.