Palmitoylated acyl protein thioesterase APT2 deforms membranes to extract substrate acyl chains.

Many biochemical reactions require controlled recruitment of proteins to membranes. This is largely regulated by posttranslational modifications. A frequent one is S-acylation, which consists of the addition of acyl chains and can be reversed by poorly understood acyl protein thioesterases (APTs). Using a panel of computational and experimental approaches, we dissect the mode of action of the major cellular thioesterase APT2 (LYPLA2). We show that soluble APT2 is vulnerable to proteasomal degradation, from which membrane binding protects it. Interaction with membranes requires three consecutive steps: electrostatic attraction, insertion of a hydrophobic loop and S-acylation by the palmitoyltransferases ZDHHC3 or ZDHHC7. Once bound, APT2 is predicted to deform the lipid bilayer to extract the acyl chain bound to its substrate and capture it in a hydrophobic pocket to allow hydrolysis. This molecular understanding of APT2 paves the way to understand the dynamics of APT2-mediated deacylation of substrates throughout the endomembrane system.

Preparation of pyridopyrazines through tandem Pd-catalyzed C-N/C-C coupling reactions of Ugi adducts.

A Pd-catalyzed selective tandem cyclization of the Ugi adduct via Buchwald-Hartwig/C-H bond functionalization reactions has been reported. This sequence offers an interesting approach for synthesizing a wide range of pyrido[1,2-a]pyrazine-3,6-dione scaffolds under mild reaction conditions in moderate to excellent yields. The scope and limitations of the protocol are discussed.

Therapeutic potential of N4-substituted thiosemicarbazones as new urease inhibitors: Biochemical and in silico approach.

Urease enzyme plays a key role in pathogenesis of gastritis and peptic ulcers. Its inhibition averts our bodies from many disorders including formation of urinary calculi. In agriculture, the high urease content causes severe environmental and hence economic problems. Due to deficiency of effective and safer drugs to tackle the aforementioned disorders, the quest for new scaffolds becomes mandatory in the field of medicinal chemistry. In this regard, we herein report a new series of N4-substituted thiosemicarbazones 3a-v as potential candidates for urease inhibition. These new N4-substituted thiosemicarbazones 3a-v of distant chemical scaffolds were characterized by advanced spectroscopic techniques, such as FTIR, 1HNMR, 13CNMR, ESI-MS and in the case of compound 3g by single crystal X-ray analysis. The compounds were evaluated for their urease inhibitory potential. All newly synthesized compounds showed significant urease inhibitions with IC50 values in range of 2.7 ± 0.320-109.2 ± 3.217 µM. Molecular docking studies were used for interactions pattern and structure-activity relationship for all compounds, which demonstrated excellent binding interactions with the active site residues, such as hydrogen bonding, π-π interactions, π-H and nickel atom coordination.

Synthesis of Spiro-ß-lactam-pyrroloquinolines as Fused Heterocyclic Scaffolds through Post-transformation Reactions.

A sequential post-transformation of Ugi four-component reaction/nucleophilic substitution was developed for the synthesis of spiro-ß-lactam-pyrroloquinolines. This method involves the Ugi-4CR of 2-chloro-3-formyl quinolines 1a-h, amines 2a-d, 2-chloroacetic acid 3, and isocyanides 4a, 4b for the synthesis of versatile precursors 5a-v. The Ugi adducts were intramolecularly cyclized under basic conditions through the sequential nucleophilic aromatic substitution (SNAr)/second-order nucleophilic substitution (SN2) reaction to give spiro-ß-lactam-pyrroloquinoline scaffolds 6a-t. This approach is an efficient method for the synthesis of fused bioactive heterocyclic backbones containing quinoline, pyrrolidone, and ß-lactam with high bond-forming efficiency.

Synthesis, characterization and molecular docking of some novel hydrazonothiazolines as urease inhibitors.

A series of new hydrazonothiazolines (3a-v) was obtained in good to excellent yields (79-96%) via cyclization of the appropriate thiosemicarbazones with phenacyl bromide. The targeted compounds were characterized by advanced spectroscopic techniques, such as FTIR, 1HNMR, 13CNMR and ESI-MS. The structure of compounds 3n and 3v was unambiguously confirmed by single crystal X-ray analysis. All compounds displayed enhanced inhibitory activity against urease enzyme with IC50 values in range of 1.73 ±â€¯1.57-27.3 ±â€¯0.655 µM when compared to standard thiourea (IC50 = 20.8 ±â€¯0.75 µM). The structure-activity relationship studies demonstrated that the activity of this series is due the central thiazole ring that interacts with nickel atoms in the active site of urease enzyme. Moreover, molecular docking studies were carried out to investigate the binding mode of all active compounds and an inactive (3u) with the active site of the urease enzyme. The docking results are in complete agreement with the experimental finding.

Regio- and chemo-selective cyclization of allenic-Ugi products for the synthesis of 3-pyrroline skeletons.

A highly efficient and stable novel class of allenic-Ugi products through a Crabbé homologation reaction is successfully demonstrated. Then, a regio- and chemo-selective cyclization of allenic-Ugi derivatives in a 5-exo-dig fashion to access 3-pyrroline skeletons is developed. Also, computational studies were performed and explained to provide insights into the reaction mechanism. This approach displays high bond-forming efficiency and atom economy with high yields.

Synthesis of novel (R)-4-fluorophenyl-1H-1,2,3-triazoles: A new class of α-glucosidase inhibitors.

Diabetes is a non-communicable disease, which occurs either due to the lack of insulin or the inability of the human body to recognize it. The recent data indicates an increase in the trend of people diagnosed with Type 2 diabetes mellitus (T2DM). α-Glucosidase inhibitors are known to reduce the impact of carbohydrates on blood glucose level and prevent the digestion of carbohydrates. α-glucosidase inhibitors hold great potential for the treatment of T2DM. In search of better α-glucosidase inhibitors, a series of novel (R)-4-fluorophenyl-1H-1,2,3-triazole derivatives were synthesized (6 and 8a-n) and evaluated for their α-glucosidase inhibitory activity in vitro. All new compounds were characterized by 1H NMR, 13C NMR, 19F NMR, ESI-MS, and where applicable by single crystal X-ray diffraction (8 m). A preliminary structure-activity relationship suggested that the presence of 1H-1,2,3-triazole ring in (R)-4-fluorophenyl-1H-1,2,3-triazole derivatives has remarkable contribution in the overall activity. Molecular docking studies were carried out to investigate the binding mode of compounds within the active site of the α-glucosidase enzyme. Docking results are in complete agreement with the experimental finding. This study unravelled a new class of triazole derivatives with α-glucosidase inhibitory activity.

Synthesis of 1H-1,2,3-triazole derivatives as new α-glucosidase inhibitors and their molecular docking studies.

Inhibition of α-glucosidase is an effective strategy for controlling the post-prandial hyperglycemia in diabetic patients. For the identification of new inhibitors of this enzyme, a series of new (R)-1-(2-(4-bromo-2-methoxyphenoxy) propyl)-4-(4-(trifluoromethyl) phenyl)-1H-1,2,3-triazole derivatives were synthesized (8a-d and 10a-e). The structures were confirmed by NMR, mass spectrometry and, in case of compound 8a, by single crystal X-ray crystallography. The α-glucosidase inhibitory activities were investigated in vitro. Most derivatives exhibited significant inhibitory activity against α-glucosidase enzyme. Their structure-activity relationship and molecular docking studies were performed to elucidate the active pharmacophore against this enzyme. Compound 10b was the most active analogue with IC50 value of 14.2 µM, while compound 6 was found to be the least active having 218.1 µM. A preliminary structure-activity relationship suggested that the presence of 1H-1,2,3-triazole ring in 1H-1,2,3-triazole derivatives is responsible for this activity and can be used as anti-diabetic drugs. The molecular docking studies of all active compounds were performed, in order to understand the mode of binding interaction and the energy of this class of compounds.

Oligonuclear Fe complexes (Fe, Fe4, Fe6, Fe9) derived from tritopic pyridine bis-hydrazone ligands-structural, magnetic, and Mössbauer studies.

Tri-topic pyridine bis-hydrazone ligands produce polynuclear complexes with Fe(II) and Fe(III) salts with varying nuclearity and metal ion oxidation states. Mononuclear, tetranuclear, hexanuclear, and nonanuclear examples are discussed using structural, magnetic and Mössbauer data. In one case, although X-ray data suggest a [3 × 3] Fe9 grid (space group P42/n), careful examination of the structure, in conjunction with magnetic and Mössbauer data, indicates an unusual situation where the corner and center sites are present at unit occupancy, whereas side site occupancy is ∼0.6.

Self-assembled Ln(III)4 (Ln = Eu, Gd, Dy, Ho, Yb) [2 × 2] square grids: a new class of lanthanide cluster.

Self-assembly of the Ln(III) ions (Ln = Eu, Gd, Dy, Ho, Yb) into square [2 × 2] grid-like arrays has been readily effected using simple, symmetric ditopic ligands based on a carbohydrazone core. The metal ions are connected via single atom bridges (e.g., µ2-O(hydrazone), µ2-OH, µ2-OMe, µ2-1,1-N3(-), µ4-O), depending on reaction conditions. The Gd(III)4 examples exhibit intramolecular antiferromagnetic exchange (-J < 0.11 cm(-1)), and in one Dy(III)4 example, with a combination of µ2-1,1-N3(-), and µ4-O bridges linking adjacent metal ions, SMM behavior is observed. One thermally driven relaxation process is observed in the temperature range 10-25 K (τ0 = 6.5(1) × 10(-7) s, U(eff) = 110(1) K) in the presence of an 1800 Oe external field, employed to suppress a second quantum based relaxation process. The extended group of Ln(III) ions which submit to this controlled self-assembly, typical of the transition metal ions, indicates the general applicability of this approach to the lanthanides. This occurs despite the anticipated limitations based on larger ionic radii and coordination numbers, and is an encouraging sign for extension to larger grids with appropriately chosen polytopic ligands.

Refining S-acylation: Structure, regulation, dynamics, and therapeutic implications.

With a limited number of genes, cells achieve remarkable diversity. This is to a large extent achieved by chemical posttranslational modifications of proteins. Amongst these are the lipid modifications that have the unique ability to confer hydrophobicity. The last decade has revealed that lipid modifications of proteins are extremely frequent and affect a great variety of cellular pathways and physiological processes. This is particularly true for S-acylation, the only reversible lipid modification. The enzymes involved in S-acylation and deacylation are only starting to be understood, and the list of proteins that undergo this modification is ever-increasing. We will describe the state of knowledge on the enzymes that regulate S-acylation, from their structure to their regulation, how S-acylation influences target proteins, and finally will offer a perspective on how alterations in the balance between S-acylation and deacylation may contribute to disease.

Meldrum-Based-1H-1,2,3-Triazoles as Antidiabetic Agents: Synthesis, In Vitro α-Glucosidase Inhibition Activity, Molecular Docking Studies, and In Silico Approach.

A series of novel alkyl derivatives (2-5a,b) and 1H-1,2,3-triazole analogues (7a-k) of Meldrum's acid were synthesized in a highly effective way by using "click" chemistry and screened for in vitro α-glucosidase inhibitory activity to examine their antidiabetic potential. 1H NMR, 13C-NMR, and high-resolution electrospray ionization mass spectra (HR-ESI-MS) were used to analyze each of the newly synthesized compounds. Interestingly, these compounds demonstrated high to moderate α-glucosidase inhibitory potency having an IC50 range of 4.63-80.21 µM. Among these derivatives, compound 7i showed extraordinary inhibitory activity and was discovered to be several times more potent than the parent compound Meldrum (1) and the standard drug acarbose. Later, molecular docking was performed to understand the binding mode and the binding strength of all the compounds with the target enzyme, which revealed that all compounds are well fitted in the active site of α-glucosidase. To further ascertain the structure of compounds, suitable X-ray single crystals of compounds 5a, 7a, and 7h were developed and studied. The current investigation has shown that combining 1H-1,2,3-triazole with the Meldrum moiety is beneficial. Furthermore, this is the first time that the aforementioned activity of these compounds has been reported.

Selective anti-cancer activity against melanoma cells using 3-O-acetyl-ß-boswellic acid-loaded 3D-Printed scaffold.

This study aimed to develop a local 3 D-printed bioactive graft using poly-caprolacton (PCL) as a drug carrier and 3-O-acetyl-ß-boswellic acid (ß-ABA) as an anticancer compound. ß-ABA-loaded 3 D-printed scaffold was fabricated and physically characterized. The results indicated more desirable mechanical and physical properties of the ß-ABA-loaded PCL mat in comparison with the PCL scaffold. Following sustained release of ß-ABA, the ß-ABA-loaded PCL scaffold revealed selective cytotoxic activity against melanoma cells, while the PCL + ABA with the bolus delivery of ß-ABA was toxic against fibroblast cells. Followed by the induction of apoptosis in melanoma cells at the gene level, the result of the western blot showed that the ß-ABA-loaded scaffold significantly up-regulated P53 and down-regulated BCL2, with an increment in the ratio of Bax/BCL2. The selective anti-cancer properties of ß-ABA-loaded 3 D printed scaffold against melanoma cells indicated that this scaffold could be potentially used as a bioactive graft to improve the melanoma treatment.

Discovery of New Boswellic Acid Hybrid 1H-1,2,3-Triazoles for Diabetic Management: In Vitro and In Silico Studies.

A series of 24 new 1H-1,2,3-triazole hybrids of 3-O-acetyl-11-keto-ß-boswellic acid (ß-AKBA (1)) and 11-keto-ß-boswellic acid (ß-KBA (2)) was designed and synthesized by employing "click" chemistry in a highly efficient manner. The 1,3-dipolar cycloaddition reaction between ß-AKBA-propargyl ester intermediate 3 or ß-KBA-propargyl ester intermediate 4 with substituted aromatic azides 5a-5k in the presence of copper iodide (CuI) and Hünig's base furnished the desired products-1H-1,2,3-triazole hybrids of ß-AKBA (6a-6k) and ß-KBA (7a-7k)-in high yields. All new synthesized compounds were characterized by 1H-, 13C-NMR spectroscopy, and HR-ESI-MS spectrometry. Furthermore, their α-glucosidase-inhibitory activity was evaluated in vitro. Interestingly, the results obtained from the α-glucosidase-inhibitory assay revealed that all the synthesized derivatives are highly potent inhibitors, with IC50 values ranging from 0.22 to 5.32 µM. Among all the compounds, 6f, 7h, 6j, 6h, 6g, 6c, 6k, 7g, and 7k exhibited exceptional inhibitory potency and were found to be several times more potent than the parent compounds 1 and 2, as well as standard acarbose. Kinetic studies of compounds 6g and 7h exhibited competitive and mixed types of inhibition, with ki values of 0.84 ± 0.007 and 1.18 ± 0.0012 µM, respectively. Molecular docking was carried out to investigate the binding modes of these compounds with α-glucosidase. The molecular docking interactions indicated that that all compounds are well fitted in the active site of α-glucosidase, where His280, Gln279, Asp215, His351, Arg442, and Arg315 mainly stabilize the binding of these compounds. The current study demonstrates the usefulness of incorporating a 1H-1,2,3-triazole moiety into the medicinally fascinating boswellic acids skeleton.

Lanthanide complexes of tritopic bis(hydrazone) ligands: single-molecule magnet behavior in a linear Dy(III)3 complex.

Tritopic pyridinebis(hydrazone)-based ligands typically produce square M(9) [3 × 3] grid complexes with first-row transition-metal ions (e.g., M = Mn, Fe, Co, Cu, Zn), but with larger lanthanide ions, such coordination motifs are not produced, and instead linear trinuclear complexes appear to be a preferred option. The reaction of 2pomp [derived from pyridine-2,6-bis(hydrazone) and 2-acetylpyridine] with La(III), Gd(III), and Dy(III) salts produces helical linear trinuclear [Ln(3)(2pomp)(2)]-based complexes, where each metal ion occupies one of the three tridentate ligand pockets. Two ligands encompass the three metal ions, and internal connections between metal ions occur through µ-O(hydrazone) bridges. Coligands include benzoate, nitrate, and N,N-dimethylformamide. The linear Dy(III)(3) complex exhibits single-molecule magnet behavior, demonstrated through alternating-current susceptibility measurements. Slow thermal magnetic relaxation was detected in an external field of 1800 Oe, where quantum-tunneling effects were suppressed (U(eff) = 14 K).

µ-O bridged Mn10 assemblies with open O6 sites for binding extra guests: structural, magnetic, and surface studies.

High nuclearity [Mn(10)M(2)] clusters have been achieved through a self-assembly approach where multiple coordinating functional groups are incorporated into one ligand. When the hydrazone group appended with an oxime function as a reactive intermediate is used, the attachment of a vanillin subunit creates a ligand (L4) with three coordinating groups, which in their own right lead to cluster assemblies. The trifunctional ligand L4 produces a series of self-assembled, mixed oxidation state (Mn(II)/Mn(III)) Mn(10)M(2) based clusters with an overall linear structure comprising two connected pentanuclear Mn(5) halves, which bind alkali metal cations (M = Li, Na, K, Rb, Cs) and H(3)O(+) in the vanillin (O(6)) end pockets, created by the assembly of three ligands around each Mn(5) subunit. Antiferromagnetic exchange dominates the spin coupling in the Mn(10) complexes, and surface studies on highly oriented pyrolytic graphite (HOPG) clearly show the arrangement of metal ions (Mn, Cs) in the Mn(10)Cs(2) linear cluster assembly.

Heterogeneous Pd/C-catalyzed, ligand free Suzuki-Miyaura coupling reaction furnishes new p-terphenyl derivatives.

A series of new para-terphenyls derivatives have been efficiently synthesized by a ligand-free heterogeneous Pd/C-catalyzed two-fold Suzuki-Miyaura coupling reaction. Methyl 5-bromo-2-iodobenzoate was selected to react with a variety of different aryl boronic acids (2a-i). Nine new p-terphenyl derivatives (3a-i) were prepared and the structures were confirmed by several analytical techniques including infrared, spectroscopy, 1H and 13C NMR spectroscopy, mass spectrometry, and in the case of compound 3 b, by X-ray diffraction method. The new derivatives were obtained in very good yields (78-91%). This synthetic facile route is envisioned to improve the preparation of p-terphenyl-based natural products.

Phenoxy pendant isatins as potent α-glucosidase inhibitors: reciprocal carbonyl⋯carbonyl interactions, antiparallel π⋯π stacking driven solid state self-assembly and biological evaluation.

Carbonyl-carbonyl (CO⋯CO) interactions are recently explored noncovalent interactions of significant interest owing to their role in the stability of biomacromolecules. Currently, substantial efforts are being made to understand the nature of these interactions. In this study, twelve phenoxy pendant isatins 1-12 have been evaluated for their α-glucosidase inhibitory potential in addition to the analysis of X-ray single crystals of 4 and 9. Both compounds 4 and 9 showed intriguing and unique self-assembled structures. The CO⋯CO and antiparallel displaced π⋯π stacking interactions are mainly involved in the formation of 1D-stair like supramolecular chains of 4 whereas antiparallel π⋯π stacking interactions drive the formation of 1D-columnar stacks of 9. These compounds not only highlight the potential of the isatin moiety in forming strong CO⋯CO and antiparallel π⋯π stacking interactions but also are interesting models to provide considerable insight into the nature of these interactions. The in vitro biological studies revealed that all twelve phenoxy pendant isatins 1-12 are highly potent inhibitors of α-glucosidase enzyme with IC50 values ranging from 5.32 ± 0.17 to 150.13 ± 0.62 µM, showing many fold more potent activity than the standard drug, acarbose (IC50 = 873.34 ± 1.67). Easy access and high α-glucosidase inhibition potential of these phenoxy pendant isatins 1-12 provide an attractive platform for finding more effective medication for controlling postprandial hyperglycemia.

ER-Golgi-localized proteins TMED2 and TMED10 control the formation of plasma membrane lipid nanodomains.

To promote infections, pathogens exploit host cell machineries such as structural elements of the plasma membrane. Studying these interactions and identifying molecular players are ideal for gaining insights into the fundamental biology of the host cell. Here, we used the anthrax toxin to screen a library of 1,500 regulatory, cell-surface, and membrane trafficking genes for their involvement in the intoxication process. We found that endoplasmic reticulum (ER)-Golgi-localized proteins TMED2 and TMED10 are required for toxin oligomerization at the plasma membrane of human cells, an essential step dependent on localization to cholesterol-rich lipid nanodomains. Biochemical, morphological, and mechanistic analyses showed that TMED2 and TMED10 are essential components of a supercomplex that operates the exchange of both cholesterol and ceramides at ER-Golgi membrane contact sites. Overall, this study of anthrax intoxication led to the discovery that lipid compositional remodeling at ER-Golgi interfaces fully controls the formation of functional membrane nanodomains at the cell surface.

Polynuclear Fe(n) complexes (n = 1, 2, 4, 5) of polytopic hydrazone ligands with Fe(II), Fe(III) and mixed oxidation state combinations.

The iron coordination chemistry of some polytopic hydrazone based ligands is examined. The complexes derive from a general self-assembly strategy, where ligand design can be used to devise specific polymetallic [n × n] grid architectures. However, as part of any complex equilibrium process, oligomeric entities can also occur, particularly when ligand tautomeric flexibility is considered, and examples of mononuclear, dinuclear, tetranuclear, and pentanuclear complexes have been observed within a related class of ligands. In addition, ligand site donor composition can lead to coordination spheres that stabilize both high spin Fe(II) and Fe(III) sites, with evidence for Fe(II) spin crossover. Structural and magnetic properties are examined, which reveal the presence of antiferromagnetic exchange in the polynuclear systems.