Photodissociation of nitric oxide from designed ruthenium nitrosyl complex: Studies on wound healing and antibacterial activity.

A photoactivable NO releasing complex [Ru(L1-2)(PPh3)(NO)Cl2](PF6)(1a) have been synthesized by complex [RuL1-2(PPh3)2Cl2](1). Newly designed bidentate ligands, i.e., 4-methoxy-N'-phenyl-N'-(pyridin-2-ylmethyl)benzohydrazide(L1) and 4-nitro-N'-phenyl-N'-(pyridin-2-ylmethyl)benzohydrazide (L2) were utilized to synthesize complex (1). Complex (1) was characterized by ESI-MS, and the solid structure of the complex [1a](PF6) was acquired by X-ray crystallography. Different spectroscopic techniques were employed for the identification of ligands (L1 and L2) and complexes (1 and [1a](PF6)). Calculations employing DFT and TD-DFT were made better to understand the electronic properties of the complex [1a](PF6). The photo liberation experiments were screened in the presence of visible light lamp. Griess assay experiment was used to quantify the photo released amount to NO. The photo liberated NO was successfully transferred to reduced myoglobin (Mb). The complex [1a](PF6) at 50 µg/mL concentration was used for wound healing and antimicrobial activity on B16F1 mouse skin cells and Escherichia coli bacteria, respectively. In results, we observed a considerable wound healing activity of [1a](PF6) complex after 36 h of incubation in the light-treated cells compared to the control medium, and also it shows more than 99% inhibition of bacterial cells after 1.5 h of treatment in the presence of light. These study suggested that this complex 1a](PF6) could be utilized for topical delivery of NO for combating several dermatological infections.

Metabolic engineering and synthetic biology for isoprenoid production in Escherichia coli and Saccharomyces cerevisiae.

Isoprenoids, often called terpenoids, are the most abundant and highly diverse family of natural organic compounds. In plants, they play a distinct role in the form of photosynthetic pigments, hormones, electron carrier, structural components of membrane, and defence. Many isoprenoids have useful applications in the pharmaceutical, nutraceutical, and chemical industries. They are synthesized by various isoprenoid synthase enzymes by several consecutive steps. Recent advancement in metabolic engineering and synthetic biology has enabled the production of these isoprenoids in the heterologous host systems like Escherichia coli and Saccharomyces cerevisiae. Both heterologous systems have been engineered for large-scale production of value-added isoprenoids. This review article will provide the detailed description of various approaches used for engineering of methyl-D-erythritol-4-phosphate (MEP) and mevalonate (MVA) pathway for synthesizing isoprene units (C5) and ultimate production of diverse isoprenoids. The review particularly highlighted the efforts taken for the production of C5-C20 isoprenoids by metabolic engineering techniques in E. coli and S. cerevisiae over a decade. The challenges and strategies are also discussed in detail for scale-up and engineering of isoprenoids in the heterologous host systems.Key points• Isoprenoids are beneficial and valuable natural products.• E. coli and S. cerevisiae are the promising host for isoprenoid biosynthesis.• Emerging techniques in synthetic biology enabled the improved production.• Need to expand the catalogue and scale-up of un-engineered isoprenoids. Metabolic engineering and synthetic biology for isoprenoid production in Escherichia coli and Saccharomyces cerevisiae.

Poly-gamma-glutamic acid biopolymer: a sleeping giant with diverse applications and unique opportunities for commercialization.

Poly-gamma-glutamic acid (γ-PGA) is a biodegradable, non-toxic, ecofriendly, and non-immunogenic biopolymer. Its phenomenal properties have gained immense attention in the field of regenerative medicine, the food industry, wastewater treatment, and even in 3D printing bio-ink. The γ-PGA has the potential to replace synthetic non-degradable counterparts, but the main obstacle is the high production cost and lower productivity. Extensive research has been carried out to reduce the production cost by using different waste; however, it is unable to match the commercialization needs. This review focuses on the biosynthetic mechanism of γ-PGA, its production using the synthetic medium as well as different wastes by L-glutamic acid-dependent and independent microbial strains. Furthermore, various metabolic engineering strategies and the recovery processes for γ-PGA and their possible applications are discussed. Finally, highlights on the challenges and unique approaches to reduce the production cost and to increase the productivity for commercialization of γ-PGA are also summarized.

Effect of cycloastragenol and punicalagin on Prp(106-126) and Aß(25-35) oligomerization and fibrillizaton.

Numerous neurological disorders, including prion, Parkinson's, and Alzheimer's disease (AD), are identified as being caused by alterations in protein conformation, aggregation, and metal ion dyshomeostasis. Recent years have seen a significant increase in the exploration and study of natural products (NPs) from plant and microbial sources for their therapeutic potential against several diseases, including cancer, diabetes, cardiovascular disease, and neurodegenerative diseases. In this study, we have examined the effect of two NPs, cycloastragenol (CAG) and punicalagin (PCG), on the metal-induced oligomerization and aggregation of Aß25-35 and PrP106-126 peptides. The peptide aggregation and inhibitory properties of both NPs were examined by the thioflavin-T (ThT) assay, MALDI-TOF, circular dichroism (CD) spectroscopy, and transmission electron microscopy (TEM). Among the two NPs, PCG significantly binds to the peptides, chelates metal ions (Cu2+ and Zn2+), inhibits peptide aggregation, substantially reduces oxidative stress, and controls the production of reactive oxygen species (ROS). Both NPs exhibited low cytotoxicity and prominently mitigated peptide-mediated cell cytotoxicity in hippocampal neuronal HT-22 cells by covalent bonding and hydrophobic interactions.

Inhibition of amyloid ß1-42 peptide aggregation by newly designed cyclometallated palladium complexes.

Uncontrolled amyloid aggregation is a frequent cause of neurodegenerative disorders such as prions and Alzheimer's disease (AD). As a result, many drug development approaches focus on evaluating novel molecules that can alter self-recognition pathways. Herein, we designed and synthesized the cyclometallated pyrene (Pd-1 and Pd-3) and anthracene (Pd-2) based palladium complexes ([Pd((L1)Cl] Pd-1, [Pd(L2)Cl](Pd-2), and [Pd(L3)Cl] (Pd-3)). This study explores the effect of these complexes on the aggregation, fibrillation, and amyloid formation of bovine serum albumin (BSA) and Aß1-42 peptide. Several spectroscopic methods were used to characterize all the Pd-complexes, and the molecular structure of Pd-3 was determined by X-ray crystallography. The secondary structures were studied using circular dichroism (CD) and transmission electron microscopy (TEM), while amyloid aggregation and inhibitory activities were investigated using the Thioflavin-T (ThT) fluorescence assay. Molecular docking of the Pd-complex (Pd-3) was done using fibril (PDB: 2BEG) and monomeric (PDB: 1IYT) peptides using Auto-dock Vina. As a result, the hydrogen bonding and hydrophobic interaction between the aromatic rings of the Pd-complexes and the amino acids of amyloid-ß peptides significantly reduced the production of ordered ß-sheets of amyloid fibrils and protein aggregation in the presence of Pd-2 and Pd-3 complexes.

Design and synthesis of piano-stool ruthenium(II) complexes and their studies on the inhibition of amyloid ß (1-42) peptide aggregation.

Misfolding and protein aggregation have been linked to numerous human neurodegenerative disorders such as Alzheimer's, prion, and Parkinson's diseases. Ruthenium (Ru) complexes have received considerable attention in studying protein aggregation due to their interesting photophysical and photo properties. In this study, we have synthesized the novel Ru complexes ([Ru(p-cymene)Cl(L-1)][PF6](Ru-1), and [Ru(p-cymene)Cl(L-2)][PF6](Ru-2)) and investigated their inhibitory activity against the bovine serum albumin (BSA) aggregation and the Aß1-42 peptides amyloid formation. Several spectroscopic methods were used to characterize these complexes, and the molecular structure of the complex was determined by X-ray crystallography. Amyloid aggregation and inhibition activities were examined using the Thioflavin-T (ThT) assay, and the secondary structures of the protein were analyzed by circular dichroism (CD) spectroscopy and transmission electron microscopy (TEM). The cell viability assay was carried out on the neuroblastoma cell line, revealing that the complex Ru-2 showed better protective effects against Aß1-42 peptide toxicity on neuro-2a cells than the complex Ru-1. Molecular docking studies elucidate the binding sites and interactions between the Ru-complexes and Aß1-42 peptides. The experimental studies revealed that these complexes significantly inhibited the BSA aggregation and Aß1-42 amyloid fibril formation at 1:3 and 1:1 molar concentrations, respectively. Antioxidant assays demonstrated that these complexes act as antioxidants, protecting from amyloid-induced oxidative stress. Molecular docking studies with the monomeric Aß1-42 (PDB: 1IYT) show hydrophobic interaction, and both complexes bind preferably in the central region of the peptide and coordinate with two binding sites of the peptide. Hence, we suggest that the Ru-based complexes could be applied as a potential agent in metallopharmaceutical research against Alzheimer's disease.

Biosensors: frontiers in rapid detection of COVID-19.

The rapid community-spread of novel human coronavirus 2019 (nCOVID19 or SARS-Cov2) and morbidity statistics has put forth an unprecedented urge for rapid diagnostics for quick and sensitive detection followed by contact tracing and containment strategies, especially when no vaccine or therapeutics are known. Currently, quantitative real-time polymerase chain reaction (qRT-PCR) is being used widely to detect COVID-19 from various types of biological specimens, which is time-consuming, labor-intensive and may not be rapidly deployable in remote or resource-limited settings. This might lead to hindrance in acquiring realistic data of infectivity and community spread of SARS-CoV-2 in the population. This review summarizes the existing status of current diagnostic methods, their possible limitations, and the advantages of biosensor-based diagnostics over the conventional ones for the detection of SARS-Cov-2. Novel biosensors used to detect RNA-viruses include CRISPR-Cas9 based paper strip, nucleic-acid based, aptamer-based, antigen-Au/Ag nanoparticles-based electrochemical biosensor, optical biosensor, and Surface Plasmon Resonance. These could be effective tools for rapid, authentic, portable, and more promising diagnosis in the current pandemic that has affected the world economies and humanity. Present challenges and future perspectives of developing robust biosensors devices for rapid, scalable, and sensitive detection and management of COVID-19 are presented in light of the test-test-test theme of the World Health Organization (WHO).

Retraction: Synthesis of deuterated isopentyl pyrophosphates for chemo-enzymatic labelling methods: GC-EI-MS based 1,2-hydride shift in epicedrol biosynthesis.

[This retracts the article DOI: 10.1039/C9RA00163H.].

Effect of tert-alcohol functional imidazolium salts on oligomerization and fibrillization of amyloid ß (1-42) peptide.

Imidazolium based IL's has gained vast interest in developing biological applications. Oligomerization and fibrillization of amyloid ß (1-42) peptide are mainly responsible for the extra-neuronal deposition of amyloid fibrils in neurodegenerative disorders like Alzheimer's disease (AD). Here, we report an effect of tert-BuOH-functional imidazolium ILs on oligomerization and fibrillization of amyloid ß (1-42) Peptide in vitro. In this study, a series of these [alkyl-tOHim][OMs] ILs with methyl sulphonate counter anion by varying alkyl chains were used. Among the seven protic ILs, four showed strong binding and inhibition activity for the formation of amyloid ß (1-42) aggregation by using Thioflavin T fluorescence binding assay. The secondary structural analysis of the peptide, pre-incubated with active ILs shows the loss of ordered ß-sheet amyloid structure. The longer alkyl chain ILs showed that an increased in amyloid binding and hence an inhibition effect on amyloid aggregation was enhanced. Thus, we propose that ILs could be presented as potential candidates for therapeutic intervention against Alzheimer's disease (AD).

Retracted Article: Synthesis of deuterated isopentyl pyrophosphates for chemo-enzymatic labelling methods: GC-EI-MS based 1,2-hydride shift in epicedrol biosynthesis.

A sesquiterpene epicedrol cyclase mechanism was elucidated based on the gas chromatography coupled to electron impact mass spectrometry fragmentation data of deuterated (2H) epicedrol analogues. The chemo-enzymatic method was applied for the specific synthesis of 8-position labelled farnesyl pyrophosphate and epicedrol. EI-MS fragmentation ions compared with non-labelled and isotopic mass shift fragments suggest that the 2H of C6 migrates to the C7 position during the cyclization mechanism.

Enhancing epi-cedrol production in Escherichia coli by fusion expression of farnesyl pyrophosphate synthase and epi-cedrol synthase.

Terpene synthase catalyses acyclic diphosphate farnesyl diphosphate into desired sesquiterpenes. In this study, a fusion enzyme was constructed by linking Santalum album farnesyl pyrophosphate synthase (SaFPPS) individually with terpene synthase and Artemisia annua Epi-cedrol synthase (AaECS). The stop codon at the N-terminus of SaFPPS was removed and replaced by a short peptide (GSGGS) to introduce a linker between the two open reading frames. This fusion clone was expressed in Escherichia coli Rosseta DE3 cells. The fusion enzyme FPPS-ECS produced sesquiterpene 8-epi-cedrol from substrates isopentenyl pyrophosphate and dimethylallyl pyrophosphate through sequential reactions. The K m values for FPPS-ECS for isopentyl diphosphate was 4.71 µM. The fusion enzyme carried out the efficient conversion of IPP to epi-cedrol, in comparison to single enzymes SaFPPS and AaECS when combined together in enzyme assay over time. Further, the recombinant E. coli BL21 strain harbouring fusion plasmid successfully produced epi-cedrol in fermentation medium. The strain having fusion plasmid (pET32a-FPPS-ECS) produced 1.084 ± 0.09 mg/L epi-cedrol, while the strain harbouring mixed plasmid (pRSETB-FPPS and pET28a-ECS) showed 1.002 ± 0.07 mg/L titre in fermentation medium by overexpression and MEP pathway utilization. Structural analysis was done by I-TASSER server and docking was done by AutoDock Vina software, which suggested that secondary structure of the N- C terminal domain and their relative positions to functional domains of the fusion enzyme was greatly significant to the catalytic properties of the fusion enzymatic complex than individual enzymes.