Insight into the interaction of 5,6 epoxy-cholesterols with human serum albumin.

5,6-Epoxy-cholesterols has been recently revealed to control metabolic pathway in breast cancer, which makes investigating their binding interaction with human serum albumin (HSA) an attractive field of research. The main aim of this article is to examine the binding interaction of 5,6 α-epoxy-cholesterol (5,6 α EC) and 5,6 ß-epoxy-cholesterol (5,6 ß- EC) with HSA using different spectroscopic methods and molecular modeling. These compounds interact with HSA via hydrophobic interactions and hydrogen bonds with binding constants 6.3 × 105 M-1 for 5,6 α-epoxy-cholesterol and 6.9 × 105 M-1 for 5,6 ß-epoxy-cholesterol besides, the mechanism of the interaction can be attributed to static quenching. Circular dichroism data indicated that the α-helical content of HSA increased from 50.5 to 59.8 and 61.1 % after the addition of 5,6 α-ECs and 5,6 ß-EC, respectively, with a ratio of 1:2. Thermodynamic analysis revealed that binding between 5,6-epoxy-cholesterols and HSA is spontaneous and entropy-driven. The molecular docking and esterase-like activity experiments were performed to envision a link between the experimental and theoretical results. The optimal binding site of 5,6-epoxy-cholesterols with HSA was located in subdomain IIA. Moreover, theoretical calculations were performed using the B3LYP function with the 6-311++G (d,p) basis set, indicating the HOMO-LUMO energy gap of 7.874 eV for 5,6 α-epoxy-cholesterol and 7.873 eV for 5,6 ß-epoxy-cholesterol. The obtained findings are assumed to provide basic data for understanding the binding interactions of HSA with oxysterol compounds, which could help explore the pharmacokinetics and pharmacodynamics of oxysterol compounds.

A Bis(imidazole)-based cysteine labeling tool for metalloprotein assembly.

Precise metal-protein coordination by design remains a considerable challenge. Polydentate, high-metal-affinity protein modifications, both chemical and recombinant, can enable metal localization. However, these constructs are often bulky, conformationally and stereochemically ill-defined, or coordinately saturated. Here, we expand the biomolecular metal-coordination toolbox with the irreversible attachment to cysteine of bis(1-methylimidazol-2-yl)ethene ("BMIE"), which generates a compact imidazole-based metal-coordinating ligand. Conjugate additions of small-molecule thiols (thiocresol and N-Boc-Cys) with BMIE confirm general thiol reactivity. The BMIE adducts are shown to complex the divalent metal ions Cu++ and Zn++ in bidentate (N2) and tridentate (N2S*) coordination geometries. Cysteine-targeted BMIE modification (>90% yield at pH 8.0) of a model protein, the S203C variant of carboxypeptidase G2 (CPG2), measured with ESI-MS, confirms its utility as a site-selective bioconjugation method. ICP-MS analysis confirms mono-metallation of the BMIE-modified CPG2 protein with Zn++, Cu++, and Co++. EPR characterization of the BMIE-modified CPG2 protein reveals the structural details of the site selective 1:1 BMIE-Cu++ coordination and symmetric tetragonal geometry under physiological conditions and in the presence of various competing and exchangeable ligands (H2O/HO-, tris, and phenanthroline). An X-ray protein crystal structure of BMIE-modified CPG2-S203C demonstrates that the BMIE modification is minimally disruptive to the overall protein structure, including the carboxypeptidase active sites, although Zn++ metalation could not be conclusively discerned at the resolution obtained. The carboxypeptidase catalytic activity of BMIE-modified CPG2-S203C was also assayed and found to be minimally affected. These features, combined with ease of attachment, define the new BMIE-based ligation as a versatile metalloprotein design tool, and enable future catalytic and structural applications.

Crystal structure, Hirshfeld and electronic transition analysis of 2-[(1H-benzimidazol-1-yl)meth-yl]benzoic acid.

In the title compound, C15H12N2O2, the benzimidazole ring system is inclined to the benzene ring by 78.04 (10)°. The crystal structure features O-H⋯N and C-H⋯O hydrogen bonding and C-H⋯π and π-π inter-actions, which were investigated using Hirshfeld surface analysis.

Crystal structure and Hirshfeld surface analysis of [2-(1H-benzimidazol-2-yl-κN 3)aniline-κN]di-chlorido-zinc(II) N,N-di-methyl-formamide monosolvate.

The title compound, [ZnCl2(C13H11N3)]·C3H7NO, crystallized in the monoclinic crystal system in space group P21/n. The asymmetric unit contains one neutral complex mol-ecule, which consists of a zinc ion, a bidentate ligand, and two chlorido ligands with di-methyl-formamide monosolvate. The ligand has two moieties, a benzimidazole and an aniline group. The benzimidazole and aniline planes are not coplanar, subtending a dihedral angle of 18.24 (8)°. The Zn(II) ion shows distorted tetra-hedral geometry, being coordinated by an imidazole N atom, the aniline N atom, and two chlorido ligands. The packing features N-H⋯O, N-H⋯Cl, C-H⋯Cl hydrogen bonding.

Crystal structure, Hirshfeld surface analysis and DFT study of 1-ethyl-3-phenyl-1,2-di-hydro-quinoxalin-2-one.

In the title mol-ecule, C16H14N2O, the di-hydro-quinoxaline moiety is not planar as there is a dihedral angle of 4.51 (5)° between the constituent rings. In the crystal, C-H⋯O hydrogen bonds form helical chains about the crystallographic 21 screw axis in the b-axis direction. Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H⋯H (51.7%), H⋯C/C⋯H (26%) and H⋯O/O⋯H (8.5%) inter-actions. The optimized structure calculated using density functional theory (DFT) at the B3LYP/6-311 G(d,p) level is compared with the experimentally determined structure in the solid state. The calculated HOMO-LUMO energy gap is 3.8918 eV.

Crystal structure, Hirshfeld surface analysis and DFT studies of (E)-4-methyl-2-{[(2-methyl-3-nitro-phen-yl)imino]-meth-yl}phenol.

The title compound, C15H14N2O3, was prepared by condensation of 2-hy-droxy-5-methyl-benzaldehyde and 2-methyl-3-nitro-phenyl-amine in ethanol. The configuration of the C=N bond is E. An intra-molecular O-H⋯N hydrogen bond is present, forming an S(6) ring motif and inducing the phenol ring and the Schiff base to be nearly coplanar [C-C-N-C torsion angle of 178.53 (13)°]. In the crystal, mol-ecules are linked by C-H⋯O inter-actions, forming chains along the b-axis direction. The Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H⋯H (37.2%), C⋯H (30.7%) and O⋯H (24.9%) inter-actions. The gas phase density functional theory (DFT) optimized structure at the B3LYP/ 6-311 G(d,p) level is compared to the experimentally determined mol-ecular structure in the solid state. The HOMO-LUMO behaviour was elucidated to determine the energy gap.

Crystal structure, Hirshfeld surface analysis and DFT studies of 2-[(2-hy-droxy-5-methyl-benzyl-idene)amino]-benzo-nitrile.

The title compound, C15H12N2O, was synthesized by condensation reaction of 2-hy-droxy-5-methyl-benzaldehyde and 2-amino-benzo-nitrile, and crystallizes in the ortho-rhom-bic space group Pbca. The phenol ring is inclined to the benzo-nitrile ring by 25.65 (3)°. The configuration about the C=N bond is E, stabilized by a strong intra-molecular O-H⋯N hydrogen bond that forms an S(6) ring motif. In the crystal, C-H⋯O and C-H⋯N inter-actions lead to the formation of sheets perpendicular to the a axis. C-H⋯π inter-actions, forming polymeric chains along the a-axis direction, connect these sheets into a three-dimensional network. A Hirshfeld surface analysis indicates that the most important contributions for the packing arrangement are from H⋯H and C⋯H/H⋯C inter-actions. The density functional theory (DFT) optimized structure at the B3LYP/6-311 G(d,p) level is compared with the experimentally determined mol-ecular structure and the HOMO-LUMO energy gap is given.

Synthesis, crystal structure at 219†K and Hirshfeld surface analyses of 1,4,6-tri-methyl-quinoxaline-2,3(1H,4H)-dione monohydrate.

The asymmetric unit of the title compound, C11H12N2O2·H2O, contains a mol-ecule of 1,4,6-trimethyl-1,4-di-hydro-quinoxaline-2,3-dione and a solvent water mol-ecule. Four atoms of the benzene ring are disordered over two sets of sites in a 0.706 (7):0.294 (7) ratio while the N-bound methyl groups are rotationally disordered with occupancy ratios of 0.78 (4):0.22 (4) and 0.76 (5):0.24 (5). In the crystal, mol-ecules are linked by O-H⋯O and C-H⋯O hydrogen bonds into layers lying parallel to (10). The Hirshfeld surface analysis indicates that the most important contributions to the packing arrangement are due to H⋯H (51.3%) and O⋯H/H⋯O (28.6%) inter-actions. The mol-ecular structure calculated by density functional theory is compared with the experimentally determined mol-ecular structure, and the HOMO-LUMO energy gap has been calculated.

Crystal structure, Hirshfeld surface analysis and DFT studies of (E)-2-{[(3-chloro-4-methyl-phen-yl)imino]-meth-yl}-4-methyl-phenol.

The title compound, C15H14ClNO, was synthesized by condensation reaction of 2-hy-droxy-5-methyl-benzaldehyde and 3-chloro-4-methyl-aniline, and crystallizes in the monoclinic space group P21/c. The 3-chloro-benzene ring is inclined to the phenol ring by 9.38 (11)°. The configuration about the C=N bond is E and an intra-molecular O-H⋯N hydrogen bond forms an S(6) ring motif. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the packing arrangement are from H⋯H (43.8%) and C⋯H/H⋯C (26.7%) inter-actions. The density functional theory (DFT) optimized structure at the B3LYP/ 6-311 G(d,p) level is compared with the experimentally determined mol-ecular structure and the HOMO-LUMO energy gap is provided.

Crystal structure, Hirshfeld surface analysis and DFT studies of 4-methyl-2-({[4-(tri-fluoro-meth-yl)phen-yl]imino}-meth-yl)phenol.

The title compound, C15H12F3NO, crystallizes with one mol-ecule in the asymmetric unit. The configuration of the C=N bond is E and there is an intra-molecular O-H⋯N hydrogen bond present, forming an S(6) ring motif. The dihedral angle between the mean planes of the phenol and the 4-tri-fluoro-methyl-phenyl rings is 44.77 (3)°. In the crystal, mol-ecules are linked by C-H⋯O inter-actions, forming polymeric chains extending along the a-axis direction. The Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from C⋯H/H⋯C (29.2%), H⋯H (28.6%), F⋯H/H⋯F (25.6%), O⋯H/H⋯O (5.7%) and F⋯F (4.6%) inter-actions. The density functional theory (DFT) optimized structure at the B3LYP/6-311 G(d,p) level is compared with the experimentally determined mol-ecular structure in the solid state. The HOMO-LUMO behaviour was elucidated to determine the energy gap. The crystal studied was refined as an inversion twin.

Crystal structure, Hirshfeld surface analysis and DFT studies of (E)-4-methyl-2-{[(4-methyl-phen-yl)imino]-meth-yl}phenol.

In the title compound, C15H15NO, the configuration of the C=N bond of the Schiff base is E, and an intra-molecular O-H⋯N hydrogen bond is observed, forming an intra-molecular S(6) ring motif. The phenol ring is inclined by 45.73 (2)° from the plane of the aniline ring. In the crystal, mol-ecules are linked along the b axis by O-H⋯N and C-H⋯O hydrogen bonds, forming polymeric chains. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the packing arrangement are from H⋯H (56.9%) and H⋯C/C⋯H (31.2%) inter-actions. The density functional theory (DFT) optimized structure at the B3LYP/ 6-311 G(d,p) level is compared with the experimentally determined mol-ecular structure, and the HOMO-LUMO energy gap is provided. The crystal studied was refined as an inversion twin.

Crystal structure and Hirshfeld surface analysis of 2-{[(4-iodo-phen-yl)imino]-meth-yl}-4-nitro-phenol.

The title compound, C13H9IN2O3, was synthesized by a condensation reaction between 2-hy-droxy-5-nitro-benzaldehyde and 4-iodo-aniline, and crystallizes in the ortho-rhom-bic space group Pna21. The 4-iodo-benzene ring is inclined to the phenol ring by a dihedral angle of 39.1 (2)°. The configuration about the C=N double bond is E. The crystal structure features C-H⋯O hydrogen-bonding inter-actions. A Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the packing arrangement are O⋯H/H⋯O (26.9%) and H⋯H (22.0%) inter-actions.

DNA binding, artificial nuclease activity and cytotoxic studies of newly synthesized steroidal pyrimidines.

The new steroidal pyrimidine derivatives (4-6) were synthesized by the reaction of steroidal thiosemicarbazones with (2-methyl) diethyl malonate in absolute ethanol. After characterization by spectral and analytical data, the DNA interaction studies of compounds (4-6) were carried out by UV-vis, fluorescence spectroscopy, hydrodynamic measurements, molecular docking and gel electrophoresis. The compounds bind to DNA preferentially through electrostatic and hydrophobic interactions with Kb; 2.31×103M-1, 1.93×103M-1 and 2.05×103M-1, respectively indicating the higher binding affinity of compound 4 towards DNA. Gel electrophoresis demonstrated that compound 4 showed a strong interaction during the concentration dependent cleavage activity with pBR322 DNA. The molecular docking study suggested the intercalation of steroidal pyrimidine moiety in the minor groove of DNA. During in vitro cytotoxicity, compounds (4-6) revealed potential toxicity against the different human cancer cells (MTT assay). During DAPI staining, the nuclear fragmentations on cells occurred after treatment with compounds 4 and 5. Western blotting analysis clearly indicates that compound 4 causes apoptosis in MCF-7 cancer cells. The results revealed that compound 4 has better prospectus to act as a cancer chemotherapeutic candidate, which warrants further in vivo anticancer investigations.

Crystal structure of N (1)-phenyl-N (4)-[(quinolin-2-yl)methyl-idene]benzene-1,4-di-amine.

In the title compound, C22H17N3, the dihedral angles between the central benzene ring and the terminal phenyl ring and quinoline ring system (r.m.s. deviation = 0.027 Å) are 44.72 (7) and 9.02 (4)°, respectively, and the bond-angle sum at the amine N atom is 359.9°. In the crystal, the N-H group is not involved in hydrogen bonding and the mol-ecules are linked by weak C-H⋯π inter-actions, generating [010] chains.

N (1)-[(1H-Imidazol-2-yl)methyl-idene]-N (4)-phenyl-benzene-1,4-di-amine.

The title compound, C16H14N4, is non-planar with dihedral angles between the planes of the imidazole and phenyl-enedi-amine rings of 30.66 (4)° and between the planes of the phenyl-enedi-amine and N-phenyl rings of 56.63 (7)°. In the crystal, mol-ecules are connected by N-H⋯N hydrogen bonds, generating a chain extending along the b-axis direction. The crystal structure is also stabilized by C-H⋯π inter-actions between N-phenyl and imidazole rings and slipped π-π stacking inter-actions between imidazole rings [centroid-centroid distance = 3.516 (4) Å] giving an overall two-dimensional layered structure lying parallel to (010).

2,2,6,6-Tetra-bromo-3,4,4,5-tetra-meth-oxy-cyclo-hexa-none.

In the title compound, C10H14Br4O5, synthesized from the meth-oxy Schiff base N-(pyridin-2-ylmeth-yl)meth-oxy-aniline and mol-ecular bromine, the cyclo-hexa-none ring has a chair conformation with one of the four meth-oxy groups equatorially orientated with respect to the carbonyl group and the others axially orientated. The C-Br bond lengthsvary from 1.942 (4) to1.964 (4) Å. In the crystal, weak C-H⋯Ocarbon-yl hydrogen-bonding inter-actions generate chains extending along the b-axis direction. Also present in the structure are two short inter-molecular Br⋯Ometh-oxy inter-actions [3.020 (3) and 3.073 (4) Å].

Synthesis and anti-tumor evaluation of B-ring substituted steroidal pyrazoline derivatives.

The synthesis and anti-tumor activity screening of new steroidal derivatives (4-18) containing pharmacologically attractive pyrazoline moieties are performed. During in vitro anticancer evaluation, the newly synthesized compounds displayed moderate to good cytotoxicity on cervical and leukemia cancer cell lines. In addition these compounds were found to be nontoxic to normal cell (PBMCs) (IC50>50 µM). The structure-activity relationship is also discussed. The most effective anticancer compound 9 was found to be active with IC50 value of 10.6 µM. It demonstrated significant antiproliferative influence on Jurkat cell lines. The morphological changes and growth characteristics of HeLa cells treated with compound 4 were analyzed by means of SEM.

6-Hy-droxy-imino-5α-cholestane.

The title compound, C(27)H(47)NO, is a steroid derivative composed of a saturated carbon fused-ring framework with an alkyl side chain. Ring bond lengths have normal values with an average of 1.533 (2) Å, while the cholestane side chain shows an average bond length of 1.533 (2) Å. The three cyclohexane rings adopt chair conformations or close to chair conformations while the cyclopentane ring is twisted. The cholesterol side-chain is fully extended with a gauche-trans conformation of the terminal methyl groups. There are eight chiral centres in the molecule; the absolute configuration of these sites was determined from the structure presented. There are two molecules in the asymmetric unit; in one, the alkyl chain is disordered over two sets of sites [occupancy ratios of 0.50:0.50 and 0.67:0.33].