Reactivity of a heterobinuclear heme-peroxo-Cu complex with -substituted catechols shows a p -dependent change in mechanism.

In biological systems, heme-copper oxidase (HCO) enzymes play a crucial role in the oxygen reduction reaction (ORR), where the pivotal O-O bond cleavage of the (heme)Fe-peroxo-Cu intermediate is facilitated by active-site (peroxo core) hydrogen bonding followed by proton-coupled electron transfer (PCET) from a nearby (phenolic) tyrosine residue. A useful approach to comprehend the fundamental relationships among H-bonding/proton/H-atom donors and their abilities to induce O-O bond homolysis involves the investigation of synthetic, bioinspired model systems where the exogenous substrate properties (such as p and bond dissociation energy (BDE)) can be systematically altered. This report details the reactivity of a heme-peroxo-copper HCO model complex (LS-4DCHIm) toward a series of substituted catechol substrates that span a range of p and O-H bond BDE values, exhibiting different reaction mechanisms.

Dioxygenase Chemistry in Nucleophilic Aldehyde Deformylations Utilizing Dicopper O-Derived Peroxide Complexes.

The chemistry of copper-dioxygen complexes is relevant to copper enzymes in biology as well as in (ligand)Cu-O (or Cu-O) species utilized in oxidative transformations. For overall energy considerations, as applicable in chemical synthesis, it is beneficial to have an appropriate atom economy; both O-atoms of O are transferred to the product(s). However, examples of such dioxygenase-type chemistry are extremely rare or not well documented.

Functionality of Reactive Oxygen Species (ROS) in Plants: Toxicity and Control in Crops Exposed to Abiotic Stress.

Agriculture and changing environmental conditions are closely related, as weather changes could adversely affect living organisms or regions of crop cultivation. Changing environmental conditions trigger different abiotic stresses, which ultimately cause the accumulation of reactive oxygen species (ROS) in plants. Common ROS production sites are the chloroplast, endoplasmic reticulum, plasma membrane, mitochondria, peroxisomes, etc.

Sequential Oxygenation of Bis(β-diketiminate) on a Selective Diruthenium Platform.

This article demonstrated the redox-noninnocent phenylene-linked bis(β-diketiminate) (L)-bridged first example of isomeric diruthenium(III)-acac species (acac = acetylacetonate) and its ability to activate dioxygen. The coordination of deprotonated L to the {Ru(acac)} in bis(bidentate) mode led to isomeric {(acac)Ru}(μ-L) ( = 1, -/- ). displayed Ru(III)-based anisotropic EPR in CHCN but without the resolution of the forbidden (Δ = 2) signal at 77 K.

Intramolecular Phenolic H-Atom Abstraction by a NArOH Ligand-Supported (μ-η:η-Peroxo)dicopper(II) Species Relevant to the Active Site Function of oxy-Tyrosinase.

Synthetic side-on peroxide-bound dicopper(II) () complexes are important for understanding the active site structure/function of many copper-containing enzymes. This work highlights the formation of new {Cu(μ-η:η-O)Cu} complexes (with electronic absorption and resonance Raman (rR) spectroscopic characterization) using tripodal NArOH ligands at -135 °C, which spontaneously participate in intramolecular phenolic H-atom abstraction (HAA). This results in the generation of bis(phenoxyl radical)bis(μ-OH)dicopper(II) intermediates, substantiated by their EPR/UV-vis/rR spectroscopic signatures and crystal structural determination of a diphenoquinone dicopper(I) complex derived from ligand -C═C coupling.

Transcriptional networks revealed late embryogenesis abundant genes regulating drought mitigation in aromatic Keteki Joha rice.

Climate change has become increasingly intertwined with the occurrence and severity of droughts. As global temperatures rise due to greenhouse gas emissions, weather patterns are altered, leading to shifts in precipitation levels and distribution. These exacerbate the risk of drought in many regions, with potentially devastating consequences.

Superior electrocatalytic hydrogen evolution activity of a triply bridged diruthenium(II) complex on a carbon cloth support.

This article describes the structural authentication of a unique triply bridged [1](ClO) and monomeric [2]ClO/[3]ClO. Electrochemical HER on a carbon cloth support demonstrated the superior performance of [1](ClO) with high TON (>10) and its long-term stability. The primary kinetic isotope effect of [1](ClO) revealed the involvement of PCET in the rate-determining step.

Coordination Variations within Binuclear Copper Dioxygen-Derived (Hydro)Peroxo and Superoxo Species; Influences upon Thermodynamic and Electronic Properties.

Copper ion is a versatile and ubiquitous facilitator of redox chemical and biochemical processes. These include the binding of molecular oxygen to copper(I) complexes where it undergoes stepwise reduction-protonation. A detailed understanding of thermodynamic relationships between such reduced/protonated states is key to elucidate the fundamentals of the chemical/biochemical processes involved.

Metal-ligand synergy driven functionalisation of alkylene linked bis(aldimine) on a diruthenium(II) platform. Cyclisation oxygenation.

This article addresses the impact of metal-ligand redox cooperativity on the functionalisation of coordinated ligands. It demonstrates the structure-reactivity correlation of bis(aldimine) derived bis-bidentate L (Py-CHN-(CH)-NCH-Py, with = 2 (L1), 3 (L2), 4 (L3)) as a function of the conformation (/) of its alkylene linker as well as the overall structural form (/) of (acac)Ru(μ-L)Ru(acac) complex moieties (1-5) possessing an electron-rich acetylacetonate (acac) co-ligand. A systematic variation of the bridging alkylene unit of L in Ru/Ru-derived 1-5 led to the following reactivity/redox events, which were validated through structural, spectroscopic, electrochemical and theoretical evaluations: (i) Cyclisation of the ethylene linked ( conformation) bis-aldimine unit of L1 C-C coupling yielded pyrazine bridged (acac)Ru(μ-L1')Ru(acac), 1a, while the corresponding -form (ethylene linker) of the metal-bound L1 in 2 ((acac)Ru(μ-L1)Ru(acac)) led to oxygenation at the ligand backbone (bis-aldimine (L) → bis(carboxamido) (L'')) O activation to generate RuRu-derived (acac)Ru(μ-L1'')Ru(acac) (2a).

Heme-copper and Heme O-derived synthetic (bioinorganic) chemistry toward an understanding of cytochrome c oxidase dioxygen chemistry.

Cytochrome c oxidase (CcO), also widely known as mitochondrial electron-transport-chain complex IV, is a multi-subunit transmembrane protein responsible for catalyzing the last step of the electron transport chain, dioxygen reduction to water, which is essential to the establishment and maintenance of the membrane proton gradient that drives ATP synthesis. Although many intermediates in the CcO catalytic cycle have been spectroscopically and/or computationally authenticated, the specifics regarding the I intermediate, hypothesized to be a heme-Cu (hydro)peroxo species whose O-O bond homolysis is supported by a hydrogen-bonding network of water molecules, are largely obscured by the fast kinetics of the A (Fe-O/Cu/Tyr) → P (Fe=O/Cu-OH/Tyr) step. In this review, we have focused on the recent advancements in the design, development, and characterization of synthetic heme-peroxo‑copper model complexes, which can circumvent the abovementioned limitation, for the investigation of the formation of I and its O-O cleavage chemistry.

Genome-wide identification and expression analysis of the Pisum sativum (L.) APETALA2/ethylene-responsive factor (AP2/ERF) gene family reveals functions in drought and cold stresses.

AP2/ERF (APETALA2/Ethylene Response Factor) is a family of transcription factors that play essential roles in regulating gene expression in response to various environmental stimuli, including biotic and abiotic stresses, hormone signaling, and developmental processes. Pisum sativum (L.), commonly known as garden pea, is a winter crop sensitive to high temperatures and can also be affected by extreme cold and drought conditions.

Unique Metal-Ligand Interplay in Directing Discrete and Polymeric Derivatives of Isomeric Azole-Carboxylate. Varying Electronic Form, C-C Coupling, and Receptor Feature.

This article dealt with the ruthenium and osmium derivatives of isomeric 1-indazole-3-carboxylic acid/2-indazole-3-carboxylic acid (HL1) and 1-benzimidazole-2-carboxylic acid (HL2) along with the π-acidic bpy (bpy = 2,2'-bipyridine) and pap (pap = 2-phenylazopyridine) co-ligands. It thus extended structurally authenticated monomeric ([(bpy)Ru(HL1)]ClO []ClO, (pap)Ru(L1) , (bpy)Os(L1) , (pap)Os(L1) , (bpy)Ru(L2) , (bpy)Os(L2) , and (pap)Os(L2) ) and dimeric ([(bpy)Ru(μ-L2)Ru(bpy)](ClO) [](ClO)) complexes. It also described modified L2' (L2' = 2,2'-bisbenzimidazolate)-bridged [(pap)Ru(μ-L2')Ru(pap)](ClO) [](ClO), where L2' was developed selectively with the {Ru(pap)} metal fragment via in situ intermolecular C-C coupling of the two units of decarboxylated benzimidazolate.

Role of long non coding RNA in plants under abiotic and biotic stresses.

Evolutionary processes have evolved plants to cope with several different natural stresses. Basic physiological activities of crop plants are significantly harmed by these stresses, reducing productivity and eventually leading to death. The recent advancements in high-throughput sequencing of transcriptome and expression profiling with NGS techniques lead to the innovation of various RNAs which do not code for proteins, more specifically long non-coding RNAs (lncRNAs), undergirding regulate growth, development, and the plant defence mechanism transcriptionally under stress situations.

On the Question of S-S Bond Cleavage of 2,2'-Dithiodipyridine on Selective Ru and Os Platforms. MLCT or Hydride or Solvent Mediated Event.

This article deals with the S-S bond scission of the model substrate 2,2'-dithiodipyridine (DTDP) in the presence of a selective set of metal precursors: Ru(acac), [RuCl(PPh)], [RuHCl(CO)(PPh)], [Ru(H)(CO)(PPh)], [Ru(bpy)Cl], [Ru(pap)Cl], [Os(bpy)Cl], and [Os(pap)Cl] (acac, acetylacetonate; bpy, 2,2'-bipyridine; pap, 2-phenylazopyridine). This led to the eventual formation of the corresponding mononuclear complexes containing the cleaved pyridine-2-thiolate unit in -/[]ClO-[]ClO. The formation of the complexes was ascertained by their single-crystal X-ray structures, which also established sterically constrained four-membered chelate (average N1-M-S1 angle of 67.

Substrate-Rhodium Cooperativity in Photoinduced ortho-Alkynylation of Arenes.

In the realm of metallaphotocatalytic C-H activation strategy, the direct excitation of the transition metal which plays the dual role of light energy harnessing alongside performing the bond breaking and forming is a rare phenomenon. In this context we have developed the first photo-induced Rh-catalyzed ortho-alkynylation under ambient conditions without the requirement of silver salt, photocatalyst (PC) or any engineered substrate or catalyst. The transformation functions by the specific cooperative effect of a six-membered rhodacycle which is the photo-responsive species.

Dioxygen Activation by Redox-Active Bis(aldimine) Ligand Bridged Diruthenium Complex Possessing Singlet Ground State.

The unexplored 'actor' behavior of redox-active bis(aldimine) congener, p-phenylene-bis(picoline)aldimine (L1), towards dioxygen activation and subsequent functionalization of its backbone was demonstrated on coordination with {Ru(acac) } (acac= acetylacetonate). Reaction under aerobic condition led to the one-pot generation of dinuclear complexes with unperturbed L1, imino-carboxamido (L2 ), and bis(carboxamido) (L3 )-bridged isovalent {Ru (μ-L1)Ru }, 1/ {Ru (μ-L3 )Ru }, 3 and mixed-valent {Ru (μ-L2 )Ru }, 2. Authentication of the complexes along with the redox non-innocence behavior of their bridge have been validated through structure, spectroelectrochemistry and DFT calculations.

Quantitative Analysis of Redox Pool (NAD , NADH Content) in Plant Samples Under Aluminum Stress.

Nicotinamide adenine dinucleotide (NAD) is an essential cofactor of numerous enzymatic reactions found in all living cells. Pyridine nucleotides (NAD and NADH) are also key players in signaling through reactive oxygen species (ROS), being crucial in the regulation of both ROS-producing and ROS-consuming systems in plants. NAD content is a powerful modulator of metabolic integration, protein de-acetylation, and DNA repair.

Redox-Induced Intramolecular C-C Coupling of Acyclic Bis(2-pyridylmethylene)ethylenediamine on a Ru(acac) Platform.

The paper documents redox-triggered C-C coupling of acyclic ,'-bis(2-pyridylmethylene)ethylenediamine (BPE) to yield 2,3-bis(2-pyridyl)pyrazine (DPP) upon coordination to an electron-rich {Ru(acac)} (acac = acetylacetonate) unit. This led to DPP-bridged [{Ru(acac)}(DPP)] ( and []ClO) along with the unperturbed BPE-bridged [{Ru(acac)}(BPE)] (). On the contrary, electron-poor {Ru(Cl)(H)(CO)(PPh)} yielded BPE-bridged [](ClO) as an exclusive product.

Safety Evaluation of Oleoresin-Based Turmeric Formulation: Assessment of Genotoxicity and Acute and Subchronic Oral Toxicity.

Turmeric rhizome (Curcuma longa L.) has been used without concern for safety as a culinary spice and traditional medicine under the ancient Ayurvedic medicinal system of India dating back nearly 4000 years. This preclinical safety evaluation was done to determine the safety of an oleoresin-based turmeric extract (CURCUGEN®).

Transcriptomic Analysis Revealed Reactive Oxygen Species Scavenging Mechanisms Associated With Ferrous Iron Toxicity in Aromatic Keteki Joha Rice.

Lowland acidic soils with water-logged regions are often affected by ferrous iron (Fe) toxicity, a major yield-limiting factor of rice production. Under severe Fe toxicity, reactive oxygen species (ROS) are crucial, although molecular mechanisms and associated ROS homeostasis genes are still unknown. In this study, a comparative RNA-Seq based transcriptome analysis was conducted to understand the Fe toxicity tolerance mechanism in aromatic Keteki Joha.

Inner-sphere electron transfer at the ruthenium-azo interface.

Metal complexes exhibiting multiple reversible redox states have drawn continuing research interest due to their electron reservoir features. In this context, the present article describes ruthenium-acac complexes (acac = acetylacetonate) incorporating redox-active azo-derived abim (azobis(1-methylbenzimidazole)) in mononuclear [Ru(acac)(abim)] (1) and dinuclear [{Ru(acac)}(μ-abim)] (2)/[{Ru(acac)}(μ-abim˙)]ClO ([2]ClO) frameworks. Structural, spectroscopic, electrochemical, and theoretical analysis of the complexes revealed the varying redox states of the azo functionality of abim, , [-NN-], [-NN-]˙, and [-N-N-] in 1, [2]ClO, and 2, respectively.

Photoinduced Regioselective Olefination of Arenes at Proximal and Distal Sites.

The Fujiwara-Moritani reaction has had a profound contribution in the emergence of contemporary C-H activation protocols. Despite the applicability of the traditional approach in different fields, the associated reactivity and regioselectivity issues had rendered it redundant. The revival of this exemplary reaction requires the development of a mechanistic paradigm that would have simultaneous control on both the reactivity and regioselectivity.