Replacement surgery with unnatural amino acids in the lock-and-key joint of glutathione transferase subunits

Proteins contain amino acid residues essential to structure and function. Ribosomal protein synthesis is typically limited to the 20 amino acids of the genetic code, but posttranslational chemical modifications can greatly expand the diversity of side chain functionalities. In this investigation, a natural aromatic residue in the lock-and-key joint at the subunit interface of the dimeric glutathione transferase P1-1 was replaced by an S-alkylcysteine residue to give a functional enzyme. Introduction of Cys in the key position inactivates the enzyme, but subsequent alkylation of this residue enhances the catalytic efficiency up to 27,000-fold. Combinatorial modification of Cys by a mixture of reagents facilitated identification of an n-butyl group as the most efficient activator. Alkylation also enhanced binding affinity for active-site ligands and stabilized the enzyme against chemical denaturation and thermal inactivation.     

A simple elemental continuity based model application to study the anaerobic microbial activity for the treatment of dairy manure

A simple anaerobic digestion (AD) model was formulated with emphasis on understanding the microbial activity during AD. The model was formulated according to two main rules that regulate the microbial growth. The first rule was maintaining the elemental continuity of macronutrients C, H, N, O, P, and S. The second rule satisfied the thermodynamics of the main AD catabolic reactions: acidogenesis and both acetotrophic and hydrogenotrophic methanogenesis. Accordingly, the stoichiometric parameters were evaluated as functions of the bacterial yield. The model also considered the enzymatic hydrolysis of solid waste. For a known solid waste composition, experimental data was utilized to estimate microbial initial concentrations, yields and kinetics, i.e., to achieve better understanding of the main AD microbial activity. The model was applied to three sets of batch experiments focusing on anaerobic dairy manure degradation. The model predicted the degradation dynamics, estimated the bacterial concentration in different inoculums, and evaluated the effect of inoculum ratios in speeding up the degradation. Elemental continuity based formulation of the model evaluated additional components that are necessary for future studies of macronutrients recovery, limitation/toxic effects, and chemical equilibrium.     

Synthesis of 1,2,4-triazolopyridazines,isoxazolofuropyridazines, and tetrazolopyridazines as antimicrobial agents

Through current and previous researches, it was found that the derivatives of pyridazine, isoxazole, tetrazole, quinazoline, hydrazinyl, and 1,2,4-triazole have many pharmacological activities. Thus, a series of novel furopyridazinones ( 7 ), isoxazolopyridazine ( 8 ), sub-benzylidene-furopyridazinones ( 9a-c ), isoxazolofuropyridazines ( 10a-c ), 3-chloro-(pyridin-4-ylmethylene)-dihydropyridazines ( 11 ), tetrazolopyridazines ( 12 ), pyridazinoquinazolinones ( 13 ), piperazinyl/morpholino-pyridazines ( 14a,b ), hydrazinyl-pyridazines ( 15 ), and 1,2,4-triazolo-pyridazines ( 16a,b ) in good yields (72%-90%) were synthesized from substituted ethyl 4-oxo-4-phenylbutanoate ( 2 ), 6-phenyl-4,5-dihydropyridazinone ( 3 ), and 6-phenyl-4-(pyridin-4-ylmethylene)-4,5-dihydropyridazinone ( 4 ) as beginning materials. All the chemical structures of the new compounds have been demonstrated by different spectroscopy analyses such as infrared, NMR, mass spectrum, and elemental analysis. Also, the activities of the newly prepared compounds were tested against many types of bacteria and fungi in vitro. Hence, 1,2,4-triazolopyridazines ( 16a,b ), isoxazolofuropyridazines ( 10a-c ), tetrazolopyridazines ( 12 ), Piperazinyl/morpholinyl-pyridazines ( 14a,b ) displayed the most efficient antimicrobial activities compared with the cefotaxime sodium and nystatin as standard drugs.     

Computational and spectral investigation of 5,12-dihydro-5,12-ethanonaphthacene-13-carbaldehyde

A conformational search of 5,12-dihydro-5,12-ethanonaphthacene-13-carbaldehyde predicted the presence of twelve conformations. The geometry of the twelve conformations established at the B3LYP/6-31G* level showed only six unique ones. Vibrational frequencies were calculated at the B3LYP/6-31G* level. The calculated vibrational frequencies enabled us to interpret the appearance of two bands corresponding to the C=O stretching mode of 5,12-dihydro-5,12-ethanonaphthacene-13-carbaldehyde. The first band corresponded to the 5,12-dihydro-5,12-ethanonaphthacene-13-carbaldehyde structure where the aldehyde group O atom was above the benzene or naphthalene ring. The other band was due to the O atom of the aldehyde group pointing out of the benzene or naphthalene ring.     

Targeting 3CLpro and SARS-CoV-2 RdRp by Amphimedon sp. Metabolites: A Computational Study

Since December 2019, novel coronavirus disease 2019 (COVID-19) pandemic has caused tremendous economic loss and serious health problems worldwide. In this study, we investigated 14 natural compounds isolated from Amphimedon sp. via a molecular docking study, to examine their ability to act as anti-COVID-19 agents. Moreover, the pharmacokinetic properties of the most promising compounds were studied. The docking study showed that virtually screened compounds were effective against the new coronavirus via dual inhibition of SARS-CoV-2 RdRp and the 3CL main protease. In particular, nakinadine B (1), 20-hepacosenoic acid (11) and amphimedoside C (12) were the most promising compounds, as they demonstrated good interactions with the pockets of both enzymes. Based on the analysis of the molecular docking results, compounds 1 and 12 were selected for molecular dynamics simulation studies. Our results showed Amphimedon sp. to be a rich source for anti-COVID-19 metabolites.     

In vivo MRI reveals the dynamics of pathological changes in the brains of cathepsin D-deficient mice and correlates changes in manganese-enhanced MRI with microglial activation

Cathepsin D (CTSD; EC 3.4.23.5) is essential for normal development and/or maintenance of neurons in the central nervous system: its deficiency causes a devastating neurological disorder with severely shortened life span in man, sheep and mouse. Neuropathologically, the CTSD deficiencies are characterized by selective neuronal degeneration, gliosis and accumulation of autofluorescent proteinaceous storage material in neurons. Our aim was to study the dynamics behind the pathological alterations occurring in the brains of CTSD-deficient (CTSD-/-) mice by using in vivo magnetic resonance imaging (MRI) and histology. In order to do this, we measured T(2) signal intensity (SI), apparent diffusion coefficient, area and volume of multiple brain structures from MR images acquired using T(2)-, T(1)- and diffusion-weighted sequences at three time points during disease progression. MRI revealed no differences in the brains between CTSD-/- and control mice at postnatal day 15+/-1 (P15+/-1), representing an initial stage of the disease. In the intermediate stage of the disease, P19(+/-1), SI alterations in the thalami of the affected mice became evident in both T(1)- and T(2)-weighted images. The terminal stage of the disease, P25, was characterized by marked alterations in the T(2) SI, apparent diffusion coefficient and volume of multiple brain structures in CTSD-/- mice. In addition, manganese enhanced high-resolution T(1)-weighted 3D sequences (MEMRI) and histological stainings revealed that the hyperintense signal areas in MEMRI matched perfectly with areas of microglial activation in the brains of CTSD-/- mice at the terminal disease stage. In conclusion, the SI alterations in the thalami of CTSD-/- mice preceded other changes, and the degenerative process was greatly enhanced at the age P19(+/-1), leading to severely reduced brain volume in just 6 days.     

Synthesis, thermal and spectral studies of first-row transition metal complexes with Girard P reagent-based ligand

A new series of first-row transition metal complexes with 1-acetylpyridinium chloride-4-benzoyl thiosemicarbazide (H2GPBzIT) have been prepared and characterized by elemental analysis, spectroscopic and magnetic measurements. The proton-ligand ionization constants were determined potentiometrically using Irving-Rossotti technique. The stability constants of complexes were also calculated and were found in agreement with the sequence of stability constants of Irving and Williams. Thermal stability and degradation kinetics have been measured using thermogravimetric analyzer. Kinetic parameters were obtained for each stage of thermal degradation of complexes using Coats-Redfern method.     

Antioxidant activity of brocchlin carboxylic acid and its methyl ester from Chrozophora brocchiana

The analogue of brevifolin carboxylic acid and its methyl ester were isolated and identified from the aqueous ethanolic extract of the leaves of Chrzophora brocchiana in addition to eight known compounds identified as gallic acid, methyl and ethyl gallate, ellagic acid, monomethoxy and methylenedioxy ellagic acid, apigenin 7-O-glucoside and luteolin 7-O-glucoside. The structures were determined primarily by ESI-MS and NMR spectroscopy. The assignment of NMR signals was preformed by means of 1H-H COSY, HMQC and HMBC experiments. The antioxidant activity of the new compounds was determined by checking the scavenging activity against DPPH free radical.     

New Halogenated Compounds from Halimeda macroloba Seaweed with Potential Inhibitory Activity against Malaria

Malaria is one of the most important infectious diseases worldwide. The causative of the most severe forms of malaria, Plasmodium falciparum, has developed resistances against all the available antimalarial drugs. In the present study, the phytochemical investigation of the green seaweed Halimeda macroloba has afforded two new compounds 1–2, along with 4 known ones 3–6. The structures of the compounds had been confirmed using 1& 2D-NMR and HRESIMS analyses. Extensive machine-learning-supported virtual-screening suggested cytochrome-C enzyme as a potential target for compound 2. Docking, absolute-binding-free-energy (ΔG_binding) and molecular-dynamics-simulation (MDS) of compound 2 revealed the strong binding interaction of this compound with cytochrome-C. In vitro testing for crude extract and isolated compounds revealed the potential in vitro inhibitory activity of both extract and compound 2 against P. falciparum. The crude extract was able to inhibit the parasite growth with an IC₅₀ value of 1.8 ± 0.35 µg/mL. Compound 2 also showed good inhibitory activity with an IC₅₀ value of 3.2 ± 0.23 µg/mL. Meanwhile, compound 6 showed moderate inhibitory activity with an IC₅₀ value of 19.3 ± 0.51 µg/mL. Accordingly, the scaffold of compound 2 can be considered as a good lead compound for the future development of new antimalarial agents.