X-ray Crystal Structure Determination Research Articles

Complexation of drug amifampridine with Cu(II), Zn(II) and Cd(II) ions, and its dimerization with the magic of Mn(II) salts. Potential anti-COVID-19 and anticancer activities.

The different behaviors of the drug amifampridine (AMP) against Mn(II), Cu(II), Zn(II) and Cd(II) metal ions, in the presence and absence of tris(2-aminoethyl)amine (tren) was studied. The results showed that AMP successfully coordinates with Cu(II), Zn(II) and Cd(II) metal ions, but interestingly it undergoes an unexpected dimerization through a C-H activation in the presence of different Mn(II) salts. A four-coordinate complex of zinc(II), [Zn(AMP)2Cl2] (1), a binuclear complex of cadmium(II), [Cd2(AMP)2Cl4] (2), three five-coordinate tren-based metal complexes, [Cu(tren)(AMP)](ClO4)2 (8), [Zn(tren)(AMP)]Cl2 (9) and [Cd(tren)(AMP)](ClO4)2 (10), three pyridinium salts, [AmpDimer]X (X = Cl-, NO3-, ClO4-; (3, 4 & 5)), and also two four-coordinate metal complexes with this pyridinium cation, [Zn(AmpDimer)Cl3] (6) and [Cd(AmpDimer)Cl3] (7), were synthesized. All new compounds were characterized by elemental analysis and IR spectroscopy, and by 1H- and 13C-NMR spectroscopy (for 1, 2, 3, 6, 7, 9 & 10) and by X-ray crystal structure determinations (for 1, 3, 4, 5, 7, 8 & 10). Theoretical studies showed that the [M(tren)(AMP)]2+ cations act as pH-sensitive drug carriers of AMP and release it upon protonation. The molecular docking studies on the interaction of AMP and the above complexes/salts with DNA and the proteins of SARS-CoV-2 showed that the synthesized complexes/salts have greater anticancer and anti-covid-19 activities than AMP alone.

Selenosalicylate; a little-studied heavy-element analogue of the versatile thiosalicylate ligand.

Selenosalicylic acid (ortho-HSeC6H4CO2H), the heavy element congener of the widely studied thiosalicylic acid, was prepared by reaction of 2-carboxybenzenediazonium chloride (HO2CC6H4N2+Cl-) with Na2Se2, followed by reduction of the resulting diselenide (SeC6H4CO2H)2 with zinc and acetic acid. The coordination chemistry of the selenosalicylate ligand towards a variety of platinum(ii), palladium(ii), nickel(ii), gold(iii), gold(i), rhodium(iii), iridium(iii) and ruthenium(ii) centres was explored. X-ray crystal structure determinations were carried out on the complexes [Pt(SeC6H4CO2)(PPh3)2], [{(p-cym)Ru(SeC6H4CO2)}2] (p-cym = η6-p-cymene, CH3C6H4CH(CH3)2), [{Cp*Rh(SeC6H4CO2)}2] (Cp* = η5-C5Me5) and [Cp*Ir(SeC6H4CO2)(PPh3)], and comparisons are made with corresponding thiosalicylate complexes. The complexes were characterised by NMR spectroscopy as well as ESI mass spectrometry, which indicated a greater propensity for fragmentation including by selenium loss, compared to the thiosalicylate analogues. Hirshfeld surface analysis to visualise and quantify intermolecular interactions revealed the dominance of H⋯H contacts in [{(p-cym)Ru(SeC6H4CO2)}2] and [Cp*Ir(SeC6H4CO2)(PPh3)].

Light-induced spin-state switching in Fe(II) spin-crossover complexes with thiazole-based chelating ligands.

Homoleptic complexes [Fe(4bt)3](ClO4)2 (1), [Fe(2bt)3](ClO4)2 (2), and [Fe(3tpH)3](ClO4)2 (3) were obtained by a reaction between the Fe(II) precursor salt and the corresponding thiazole-based bidentate ligand (L = 4bt = 4,4'-bithiazole, 2bt = 2,2'-bithiazole, 3tpH = 3-(thiazol-2-yl)pyrazole). X-ray crystal structure determination revealed crystallization of solvent-free complex 1, a solvate 2·MeOH, and a co-crystal 3·2(3tpH). The crystal packing of all these complexes is dominated by one-dimensional interactions between the [Fe(L)3]2+ cations. These interactions are stronger in 2·MeOH and 3·2(3tpH), leading to cooperative and slightly hysteretic transitions between the high-spin and low-spin electronic configurations at ∼235 K and 159 K, respectively. In contrast, weaker intermolecular interactions in 1 result in a gradual spin crossover above 300 K, with the maximum fraction of the HS state ∼25% achieved at 400 K. Complexes 2 and 3·2(3tpH) exhibit light-induced excited spin state trapping (LIESST) under irradiation with white light or a 532 nm laser at 5 K. After the photoexcitation, the trapped metastable HS state relaxes to the ground LS state with the average relaxation temperature of 81 K and 68 K, respectively. Examination of the relaxation dynamics by optical absorption spectroscopy on a single crystal of 3·2(3tpH) revealed the sigmoidal shape of the relaxation curves at lower temperatures, attributed to cooperative effects, as well as a plateau at ∼10% of the HS fraction at intermediate temperatures, hinting at a more complex mechanism for the relaxation of the LIESST phase in this material.

Discovery of novel cGAS inhibitors based on natural flavonoids

Cyclic GMP-AMP synthase (cGAS) plays an important role in the inflammatory response. It has been reported that aberrant activation of cGAS is associated with a variety of immune-mediated inflammatory disorders. The development of small molecule inhibitors of cGAS has been considered as a promising therapeutic strategy for the diseases. Flavonoids, a typical class of natural products, are known for their anti-inflammatory activities. Although cGAS is closely associated with inflammation, the potential effects of natural flavonoid compounds on cGAS have been rarely studied. Therefore, we screened an in-house natural flavonoid library by pyrophosphatase (PPiase) coupling assay and identified novel cGAS inhibitors baicalein and baicalin. Subsequently, crystal structures of the two natural flavonoids in complex with human cGAS were determined, which provide mechanistic insight into the anti-inflammatory activities of baicalein and baicalin at the molecular level. After that, a virtual screening based on the crystal structures of baicalein and baicalin in complex with human cGAS was performed. As a result, compound C20 was identified to inhibit both human and mouse cGAS with IC50 values of 2.28 and 1.44 μM, respectively, and its detailed interactions with human cGAS were further revealed by the X-ray crystal structure determination. These results demonstrate the potential of natural products used as hits in drug discovery and provide valuable hints for further development of cGAS inhibitors.

Cu1.5SeyTe1-y (y = 0.2-0.7): A Series of Narrow Band Gap Semiconductors with Low Thermal Conductivity at Ambient Temperature.

Coinage metal chalcogenides offer ideal prerequisites for high thermoelectric performance and sensor applications, with their usually low lattice thermal and high electrical conductivity, as well as small band gaps. In the solid solution Cu1.5SeyTe1-y we synthesized phase pure materials with y = 0.2-0.7 and characterized them concerning selected physical properties. X-ray crystal structure determination was performed for two representatives of the solid solution, Cu1.5Se0.3Te0.7 and Cu1.5Se0.5Te0.5. The entire series crystallizes cubically, in space group Pm3̅n. No structural changes are observed between room temperature and the synthesis temperature of 723 K. The conductivity measurements and Seebeck coefficients of Cu1.5Se0.3Te0.7 and Cu1.5Se0.5Te0.5 indicate that the two representatives are narrow band gap semiconductors (Eg 0.06-0.08 eV). Both compounds show positive Seebeck coefficients and reasonably low thermal conductivities at moderate temperatures. Cu1.5Se0.5Te0.5 is characterized by a bulk modulus of 40.9 GPa.

Supramolecular architectures of dimethyltin(IV) isothiocyanate compounds containing diimine ligands: Structural phase transition and thermal properties

Three diorganotin (IV) compounds with the general formula [SnMe2(NCS)2(NN)] have been synthesized and characterized using elemental analysis, IR, 1H, 13C, 119Sn , HH COSY, HSQC, and DEPT-135° NMR spectroscopy, and X-ray crystal structure determination. The complexes [SnMe2(NCS)2(Me2bpy)] (1), [SnMe2(NCS)2(phendione)] (2), and [SnMe2(NCS)2(4,4′-bpy)] (3) were synthesized by the reaction of SnMe2(NCS)2 with corresponding diimine ligands of 5,5ꞌ-dimethyl-2,2ꞌ-bipyridine (Me2bpy), 1,10-phenanthroline-5,6‑dione (phendione), and 4,4′-bipyridine (4,4′-bpy), respectively. NMR data reveals that 1–3 persists as the hexa-coordinated dimethyltin(IV) complexes in solution. The X-ray single crystal investigation of [SnMe2(NCS)2(Me2bpy)] (1) exhibits structural phase transition during the cooling from RT (295 K) to LT (100 K). This transition is associated with a doubling of the asymmetric unit in the low-temperature phase (1-LT) relative to the room-temperature phase (1-RT), which results in the change of the space group (P21/m in RT and P21/c in LT). The 3D Hirshfeld surface analysis and 2D fingerprint maps were used for quantitative mapping and visualization of the small differences in the intermolecular interactions between both crystallographic phases. Our results show that the reaction of SnMe2(NCS)2 with 4,4′-bipyridine is not dependent upon the mole ratio and reaction time and the resulting tin(IV) cations adopt the octahedral geometry which is linked by 4,4′-bipyridine into the coordination polymer while the pairs of μ-1,3-bridging thiocyanate anions further interconnected the tin atoms to form a 2D supramolecular chains. Thermal properties of the complexes reveal that they are thermally stable up to 173 °C for 1, 183 °C for 2, and 178 °C for 3.

Synthesis, characterization, biological and theoretical studies of a new Pd(II) complex of drug carvedilol: Strong anticancer activity against several cell lines

In this study, a new Pd(II) complex of the drug carvedilol (CAR), [Pd(CAR)2Cl2] (PdCAR), was synthesized and characterized using X-ray crystal structure determination, CHN elemental analysis, and FT-IR, 1H NMR and UV–Vis spectroscopies. The crystal structure of the above complex shows that the Pd atom lies on a center of symmetry and is coordinated by two ligands (CAR) and by two chloride anions in a square planar arrangement. It means that each carvedilol ligand is coordinating to the Pd atom in a monodentate fashion, via the aliphatic nitrogen atom. Theoretical studies showed that the nature of the bond between PdCl2 and two carvedilol ligands, similar to that between PdCl2 and two dimethylamine (DMA) ligands, is mainly electrostatic. Interestingly, the CAR−PdCl2 bond is stronger than the DMA−PdCl2 bond. The UV–Vis and NMR studies indicate that the PdCAR complex is stable in solution. The DNA interaction studies were performed using the molecular docking simulation. The results indicated that the binding affinity of the PdCAR for B-DNA is higher than that of the CAR. Furthermore, the cytotoxicity effects of CAR, PdCAR and cisplatin (CIS) against MCF-7, HepG2, SW-480, CT-26 and HEK-293 cell lines were also evaluated and compared by MTT assay. The results showed that the cytotoxicity of both CAR and PdCAR on the above cell lines in all cases, except MCF-7, is higher than that of CIS.

Rapid and efficient ambient temperature X-ray crystal structure determination at Turkish Light Source

High-resolution biomacromolecular structure determination is essential to better understand protein function and dynamics. Serial crystallography is an emerging structural biology technique which has fundamental limitations due to either sample volume requirements or immediate access to the competitive X-ray beamtime. Obtaining a high volume of well-diffracting, sufficient-size crystals while mitigating radiation damage remains a critical bottleneck of serial crystallography. As an alternative, we introduce the plate-reader module adapted for using a 72-well Terasaki plate for biomacromolecule structure determination at a convenience of a home X-ray source. We also present the first ambient temperature lysozyme structure determined at the Turkish light source (Turkish DeLight). The complete dataset was collected in 18.5 min with resolution extending to 2.39 Å and 100% completeness. Combined with our previous cryogenic structure (PDB ID: 7Y6A), the ambient temperature structure provides invaluable information about the structural dynamics of the lysozyme. Turkish DeLight provides robust and rapid ambient temperature biomacromolecular structure determination with limited radiation damage.

New Dinuclear Macrocyclic Copper(II) Complexes as Potentially Fluorescent and Magnetic Materials.

Two dinuclear copper(II) complexes with macrocyclic Schiff bases K1 and K2 were prepared by the template reaction of (R)-(+)-1,1'-binaphthalene-2,2'-diamine and 2-hydroxy-5-methyl-1,3-benzenedicarboxaldehyde K1, or 4-tert-butyl-2,6-diformylphenol K2 with copper(II) chloride dihydrate. The compounds were characterized by spectroscopic methods. X-ray crystal structure determination and DFT calculations confirmed their geometry in solution and in the solid phase. Moreover, intermolecular interactions in the crystal structure of K2 were analyzed using 3D Hirshfeld surfaces and the related 2D fingerprint plots. The magnetic study revealed very strong antiferromagnetic CuII-CuII exchange interactions, which were supported by magneto-structural correlation and DFT calculations conducted within a broken symmetry (BS) framework. Complexes K1 and K2 exhibited luminescent properties that may be of great importance in the search for new OLEDs. Both K1 and K2 complexes showed emissions in the range of 392-424 nm in solutions at various polarities. Thin materials of the studied compounds were deposited on Si(111) by the spin-coating method or by thermal vapor deposition and studied by scanning electron microscopy (SEM/EDS), atomic force microscopy (AFM), and fluorescence spectroscopy. The thermally deposited K1 and K2 materials showed high fluorescence intensity in the range of 318-531 nm for K1/Si and 326-472 nm for the K2/Si material, indicating that they could be used in optical devices.

Tris chelated meridional isomers of Co(III) complexes: Synthesis, crystal structure, protein binding, cytotoxicity studies and DFT/TDDFT calculation

Two mononuclear Co(III) complexes, [Co(L1)3] (1) and [Co(L2)3] (2) (HL1, 2-[(2-methoxy-ethylimino)-methyl]-phenol; HL2, 1-[(2-methoxy-ethylimino)-methyl]-naphthalen-2-ol) have been synthesized and characterized by X-ray crystal structure determination, IR and mass spectroscopic techniques. Both the complexes are mononuclear with distorted octahedral geometries and the Co(III) center are coordinated with three bidentate (O, N) Schiff base ligands. Complexes 1 and 2 form 1D and 3D supramolecular structures, respectively, with weak CH…π interactions. Experimental UV–vis absorption spectra have been compared with the results obtained from DFT / TD-DFT calculation using B3LYP functional and LanL2DZ basis set. The interaction of the complexes with bovine serum albumin (BSA) and human serum albumin (HSA) were studied using electronic absorption and fluorescence spectroscopic methods and the results show that complexes potentially quench the fluorescence of BSA/HSA through ground state association mechanism. Cytotoxicity studies of these complexes have been performed against breast cancer cell lines and found that they have moderate anticancer activity.

Spectroscopy, molecular structure, and electropolymerization of Ni(II) and Cu(II) complexes containing a thiophene-appending fluorinated Schiff base ligand.

In this contribution, we describe the preparation, characterization, and electrochemical behavior of a series of four new mononuclear M(II) complexes featuring a symmetric substituted N2O2-tetradentate Schiff base ligand, bearing either trifluoromethyl and p-bromophenyl (M = Ni, 3; Cu, 4) or trifluoromethyl and the π-extended p-(2-thienyl)phenylene (M = Ni, 5; Cu, 6) substituents. Complexes 3 and 4 were readily synthesized by reacting the diprotic fluorinated Schiff base proligand 2 with the appropriate hydrated metal(II) acetates, whereas 5 and 6 were obtained upon Stille cross-coupling reaction of 3 and 4 with 2-(tributylstannyl)-thiophene, respectively. Compounds 3-6 were isolated as neutral, air, and thermally stable-coloured solids, with yields ranging from 60 to 80%. The four complexes, the diimine precursor 1 and its trifluoroacetylated derivative 2, were identified using analytical (EA, ESI-MS), spectroscopic (IR, 1H, 13C, and 19F NMR), and X-ray crystallographic methods. X-ray crystal structure determination of complexes 3-5 revealed that both four-coordinate Ni(II) and Cu(II) metal ions adopt a square planar geometry. The magnetic properties of powdered samples of the Cu(II) derivatives 4 and 6 have been investigated (2-300 K) and found consistent in both cases with a single isolated copper(II) ion (s = 1/2). DFT calculations were used to examine the optimal geometries of complexes 5 and 6, allowing for a consistent perspective of their structure and characteristics. The primary aspects of the UV-vis spectra were interpreted using TD-DFT computations. Finally, electrochemical data indicate that complexes 5 and 6 polymerize at high anodic potentials in acetonitrile (greater than 2.0 V vs. Ag/AgCl). Cyclic voltammetry, scanning electron microscopy, and energy-dispersive X-ray spectroscopy (SEM-EDS) analyses were used to characterize the obtained films poly-5 and poly-6.

Energetic [1,2,5]oxadiazolo [2,3-a]pyrimidin-8-ium Perchlorates: Synthesis and Characterization

A convenient method to access the above perchlorates has been developed, based on the cyclocondensation of 3-aminofurazans with 1,3-diketones in the presence of HClO4. All compounds were fully characterized by multinuclear NMR spectroscopy and X-ray crystal structure determinations. Initial safety testing (impact and friction sensitivity) and thermal stability measurements (DSC/DTA) were also carried out. Energetic performance was calculated by using the PILEM code based on calculated enthalpies of formation and experimental densities at r.t. These salts exhibit excellent burn rates and combustion behavior and are promising ingredients for energetic materials.

Experimental and Theoretical Studies of the Optical Properties of the Schiff Bases and Their Materials Obtained from o-Phenylenediamine.

Two macrocyclic Schiff bases derived from o-phenylenediamine and 2-hydroxy-5-methylisophthalaldehyde L1 or 2-hydroxy-5-tert-butyl-1,3-benzenedicarboxaldehyde L2, respectively, were obtained and characterized by X-ray crystallography and spectroscopy (UV-vis, fluorescence and IR). X-ray crystal structure determination and DFT calculations for compounds confirmed their geometry in solution and in the solid phase. Moreover, intermolecular interactions in the crystal structure of L1 and L2 were analyzed using 3D Hirshfeld surfaces and the related 2D fingerprint plots. The 3D Hirschfeld analyses show that the most numerous interactions were found between hydrogen atoms. A considerable number of such interactions are justified by the presence of bulk tert-butyl groups in L2. The luminescence of L1 and L2 in various solvents and in the solid state was studied. In general, the quantum efficiency between 0.14 and 0.70 was noted. The increase in the quantum efficiency with the solvent polarity in the case of L1 was observed (λex = 350 nm). For L2, this trend is similar, except for the chloroform. In the solid state, emission was registered at 552 nm and 561 nm (λex = 350 nm) for L1 and L2, respectively. Thin layers of the studied compounds were deposited on Si(111) by the spin coating method or by thermal vapor deposition and studied by scanning electron microscopy (SEM/EDS), atomic force microscopy (AFM), spectroscopic ellipsometry and fluorescence spectroscopy. The ellipsometric analysis of thin materials obtained by thermal vapor deposition showed that the band-gap energy was 3.45 ± 0.02 eV (359 ± 2 nm) and 3.29 ± 0.02 eV (377 ± 2 nm) for L1/Si and L2/Si samples, respectively. Furthermore, the materials of the L1/Si and L2/Si exhibited broad emission. This feature can allow for using these compounds in LED diodes.

(±)-Polysiphenol and Other Analogues via Symmetrical Intermolecular Dimerizations: A Synthetic, Spectroscopic, Structural, and Computational Study.

We report an improved total synthesis of 4,5-dibromo-9,10-dihydrophenanthrene-2,3,6,7-tetraol, (±)-polysiphenol, via intermolecular McMurray dimerization of 5-bromovanillin and subsequent intramolecular oxidative coupling as the key steps. The synthetic route is applicable to 4,5-dichloro- and 4,5-difluoro-halologues (as well as a 4,5-dialkyl-analogue). Distinctive AA'BB' multiplets in their 1H NMR spectra for the dimethylene bridges of the dibromo and dichloro compounds reveal them to be room-temperature stable atropisomers, while for the difluoro compound they present as a singlet. X-ray crystal structure determinations of their tetramethylated synthetic precursors show atropisomeric twist angles of 48°, 46°, and 32°, respectively, with the former representing the largest yet observed in any 4,5-disubstituted-9,10-dihydrophenanthrene. DFT computational studies reveal an unprecedented two-stage atropisomeric interconversion process involving time-independent asynchronous rotations of the dimethylene bridge and the biaryl axis for halologues containing chlorine or bromine, but a more synchronous rotation for the difluoro analogue.

Penta-coordinated Cr(II) and Cu(II) complexes appended with 4′-(4-quinolyl)-2,2′:6′,2″-terpyridine: Crystal structure, Hirshfeld surface analysis, luminescence and thermal properties

Two new chromium and copper complexes containing 4′-(4-quinolyl)-2,2′:6′,2′'-terpyridine (qtpy) have been synthesized and characterized using elemental analysis, IR and X-ray crystal structure determination. The reaction of CrCl3.6H2O with qtpy in presence of granulated zinc as a reducing agent has been resulted in the formation of the new terpyridine chromium(II) complex [Cr(qtpy)Cl2] (1). Moreover, the reaction of CuBr2 with qtpy affords the new complex [Cu(qtpy)Br2] (2). Recrystallization of 1 from DMF and recrystallization of 2 from DMSO yield the respective solvates, [Cr(qtpy)Cl2].DMF (1.DMF) and [Cu(qtpy)Br2].2DMSO (2.2DMSO), confirmed by X-ray single crystal analysis. The crystal structures of isostructural complexes [Cr(qtpy)Cl2].DMF (1.DMF) and [Cu(qtpy)Br2].2DMSO (2.2DMSO) reveal that chromium(II) and copper(II) adopt the penta-coordinated square pyramidal geometry in which Cr and Cu are coordinated by three nitrogen atoms of qtpy and two Cl- for 1.DMF, and two Br- for 2.2DMSO. As well, the crystal packings of complex 1.DMF, and 2.2DMSO clearly show the formation of supramolecular structures through C-H…X (X = N, O, halide) hydrogen bond interactions. The 3D Hirshfeld surface analysis and 2D fingerprint maps were used for quantitative mapping out of the intermolecular interactions for 1.DMF, and 2.2DMSO. Luminescence properties of 1 and 2 displayed the ligand-based π–π* emission bands in solution. Thermal properties of 1 and 2 show that they undergo thermal decomposition and the corresponding metal oxide formed in each case.

Structural and optical properties of the p-alkylated 2,6-bis(benzimidazol)phenoles obtained from o-phenylenediamine and their sensitive behavior towards zinc(II) ions

Two compounds, 2-hydroxy-5-methylisophthalaldehyde (L1) and 2-hydroxy-5-tert-butyl-1,3-benzenedicarboxaldehyde (L2), were obtained in the reaction between o-phenylenediamine and aldehydes. The X-ray crystal structure determination and DFT calculations aimed at the confirmation of the geometry of L1 and L2 in a solution and in the solid state were performed. The intermolecular interactions in the crystal structure of L1·0.5 CH3COOC2H5, L2·MeOH and L2·0.25 n-hexane were analyzed using the 3D Hirshfeld surfaces and related 2D fingerprint plots. The x-ray and 3D Hirschfeld analyses show the importance of the presence of the solvent in the crystal lattice. In L2·0.25 n-hexane, the solvent is only weakly bound, and only a robust network of NH…N and CH…N hydrogen bonds that stabilise channels was noted. On the other hand, in the L2·MeOH, methanol forms a robust network of hydrogen bonds. The luminescence of L1 and L2 in various solvents and in the solid state was studied. In the solid state, emission was registered at 520 nm and 506 nm for L1 and L2, respectively. DFT calculations of the fluorescence spectra indicate green luminescence of the keto form of the compounds. Thin layers of the obtained compounds were deposited on Si(111) by the spin coating method and examined with scanning electron microscopy (SEM/EDS), atomic force microscopy (AFM) and fluorescence spectroscopy. The fluorescence sensing abilities of the compounds towards Zn2+ ions were evaluated. The experimental results showed that L1 and L2 could sensitively and efficiently detect Zn2+ ions (increase or decrease in the emission band at 443 nm for L1 or 434 nm for L2 (λex = 290) was observed).

New cyclopeptide alkaloid of Condalia buxifolia and the absolute stereochemistry of Condaline A

During the course of a study of Condalia buxifolia (Rhamnaceae), one new cyclopeptide alkaloid condaline B (1), together with six known cyclopeptide alkaloids, condaline A (2), and the scutianines B (3), − D (4) and -E (5), frangulanine (6), and 3,4,28-tris-epi-scutianene N (7), were isolated from the rind bark of Condalia buxifolia. Their structures have been confirmed through spectroscopic analyses such as 1D and 2D NMR experiments. The absolute stereochemistry of condaline A (2), was elucidated by X-ray crystal structure determination of its HI salt. In addition, condaline B (1) was obtained synthetically through a structural transformation of condaline A. Meanwhile, the crude methanol extract, the basic ether fraction, and alkaloids 1–7 were tested against various strains of Gram-positive and Gram-negative bacteria and fungus, showing promising antimicrobial activity

Novel 7-Aryliden-3,3a,4,5,6,7-(hexahydro-5-(2-ethoxyethyl)-2-phenyl-3-aryl-2H-pyrazolo[4,3-c]pyridine Hydrochloride: Synthesis and Structure

A Claisen-Schmidt type reaction of 1-(2-ethoxyethyl)piperidin-4-one with differ¬ent aromatic aldehydes led to corresponding dienones with a yield of 65‒71%. 7-Arylidene-3,3a,4,5,6,7-(hexahydro-5-(2-ethoxyethyl)-2-phenyl-3-aryl-2H-pyrazolo[4,3-c]pyridines were synthesized by heterocyclization of 3,5-dia¬rylidene-piperidin-4-ones with phenylhydrazine hydrochloride in methanol at 70 °C over 4‒6 h. The X-ray crystal structure determination of 7-(p-methoxy¬benzyliden)-3,3a,4,5,6,7-(hexahydro-5-(2-ethoxyethyl)-2-phenyl-3-(p-methoxy¬phenyl)-2H-pyrazolo[4,3-c]pyridine hydrochloride (the deposition number is CCDC 862410) was completed. The piperidine and pyrazoline rings are close to a chair and envelope conformations, respectively.

Antibody-dependent enhancement (ADE) of SARS-CoV-2 pseudoviral infection requires Fc\u03b3RIIB and virus-antibody complex with bivalent interaction

Understanding the underlying molecular mechanisms behind ADE of SARS-CoV-2 is critical for development of safe and effective therapies. Here, we report that two neutralizing mAbs, MW01 and MW05, could enhance the infection of SARS-CoV-2 pseudovirus on FcγRIIB-expressing B cells. X-ray crystal structure determination and S trimer-binding modeling showed that MW01 and MW05 could bind to RBDs in S trimer with both “up” and “down” states. While, the neutralizing mAb MW07, which has no ADE activity only binds to RBD in S trimer with “up” state. Monovalent MW01 and MW05 completely diminished the ADE activity compared with their bivalent counterparts. Moreover, both macropinocytosis and endocytosis are confirmed involving in ADE of SARS-CoV-2 pseudoviral infection. Blocking endosome transportation and lysosome acidification could inhibit the ADE activity mediated by MW05. Together, our results identified a novel ADE mechanism of SARS-CoV-2 pseudovirus in vitro, FcγRIIB-mediated uptake of SARS-CoV-2/mAb complex with bivalent interaction.

Selective cyanide sensing using a Fe(III) complex of pyridoxal-beta alanine Schiff base

Fluorogenic chemosensors using pyridoxal derivatized ligands as fluorophore is a rapidly growing field of research. Here we report a new Fe(III) complex, [Fe(HBala-pydx)(Bala-pydx)] (H2Bala-pydx is the Schiff base of pyridoxal with beta-alanine), which can serve as a sensitive and selective turn-on fluorescent sensor for the detection of cyanide(CN−) in micromolar concentrations (L.O.D. is 1.134 µM), via the ligand displacement approach, in aqueous-acetonitrile medium. The Fe(III) complex is adequately characterized by analytical and spectroscopic methods along with X-ray crystal structure determination.