What Is Wrong with Hyaluronic Acid Chemistry? A N/C Solid-State NMR Re-Evaluation of Its Dopamine Conjugates.

In this work, a systematic N/C solid-state NMR investigation is performed on three dopamine (DA) conjugates of hyaluronic acid, considered in both its native (HA) and NaIO-oxidized (HA) forms. Two of them, here named HA-DA and HA-DA, have been previously introduced as covalent conjugates involving DA amine nitrogen: the former by EDC-mediated amide bond formation, and the latter by reaction of the Schiff base with the aldehyde moieties presumed to exist in HA. The third conjugate, HA-DA, is reported here for the first time; it is obtained by simply mixing hyaluronan with DA∙HCl at pH 5.

Polydopamine conjugated SiO nanoparticles as potential drug carriers for melanoma treatment.

Silica nanoparticles (SiO) are increasingly investigated for biomedical applications. This study aimed to analyze the potential use of a SiO nanoparticles coated with biocompatible polydopamine (SiO@PDA) as a potential chemotherapeutic drug carrier. SiO morphology and PDA adhesion was analyzed by dynamic light scattering, electron microscopy and nuclear magnetic resonance.

Structural studies of various olmesartan solvates.

Seven solvates of the angiotensin II receptor blocker agent olmesartan (CHNO), namely, the methanol (CHNO·CHO), ethanol (CHNO·CHO), isopropanol (CHNO·CHO), isobutanol (CHNO·CHO), 2-ethoxyethanol (CHNO·CHO), chloroform (CHNO·CHCl) and acetonitrile (CHNO·CHN) solvates, were successfully obtained. The crystal structures were determined using the single-crystal X-ray diffraction technique and the structural features are described, each solvate containing one molecule of olmesartan and one of solvent in the asymmetric unit. The samples were also analyzed by powder X-ray diffraction.

Solid-State and Theoretical Investigations of Some Banister-Type Macrocycles with 2,2'-Aldoxime-1,1'-Biphenyl Units.

In the context of helical chirality, bridging of biphenyl units leads to banister-type compounds and the stability of the resulted atropisomers may increase dramatically if suitable changes are performed in the linker unit that coils around the biphenyl moiety. A rigorous density functional theory (DFT) study was conducted for macrocycles containing rigid oxime ether segments connected to the biphenyl backbone in order to determine how the rotation barriers are influenced by the presence of either a flexible oligoethyleneoxide or a more rigid -xylylene component in the macrocycle. The calculated values for the racemization barrier were in good agreement with those obtained experimentally and confirm the benefit of introducing a more rigid unit in the macrocycle on the stability of atropisomers.

Hydrogen-Mediated Noncovalent Interactions in Solids: What Can NMR Crystallography Tell About?

Hydrogen atoms play a crucial role in the aggregation of organic (bio)molecules through diverse number of noncovalent interactions that they mediate, such as electrostatic in proton transfer systems, hydrogen bonding, and CH-π interactions, to mention only the most prominent. To identify and adequately describe such low-energy interactions, increasingly sensitive methods have been developed over time, among which quantum chemical computations have witnessed impressive advances in recent years. For reaching the present state-of-the-art, computations had to rely on a pool of relevant experimental data, needed at least for validation, if not also for other purposes.

Ketoconazole--aminobenzoic Acid Cocrystal: Revival of an Old Drug by Crystal Engineering.

The 1:1 cocrystal of the antifungal agent ketoconazole with -aminobenzoic acid was successfully crystallized and systematically characterized by a physical and pharmacological point of view. Crystal structure determination confirmed the cocrystal identity, giving full insight in its crystal packing and degree of disorder. Powder dissolution measurements revealed a 10-fold aqueous solubility increase that induces a 6.

A three-armed cryptand with triazine and pyridine units: synthesis, structure and complexation with polycyclic aromatic compounds.

The aromatic nucleophilic substitution reaction based synthesis of a three-armed cryptand displaying 2,4,6-triphenyl-1,3,5-triazine units as caps and pyridine rings in the bridges, along with NMR, MS and molecular modelling-based structural analysis of this compound are reported. Appropriate NMR and molecular modelling investigations proved the formation of 1:1 host-guest assemblies between the investigated cryptand and some polynuclear aromatic hydrocarbons or their derivatives.

Novel Palladium(II) Complexes that Influence Prominin-1/CD133 Expression and Stem Cell Factor Release in Tumor Cells.

New Pd(II) complexes of 1,7-bis(2-methoxyphenyl)hepta-1,6-diene-3,5-dione were synthesized and structurally characterized. The complexes were tested in vitro on human colon and hepatic carcinoma cell lines, normal hepatic cells and hematopoietic progenitor cells. Biological tests proved that Pd(II) complexes and (containing a curcumin derivative) exhibit a strong in vitro antitumor effect against the cells derived from human colorectal carcinoma and the hepatic metastasis of a colorectal carcinoma.

Optimized multi-step NMR-crystallography approach for structural characterization of a stable quercetin solvate.

Herein we report the preparation and solid state structural investigation of the 1,4-dioxane-quercetin solvate. NMR crystallography methods were employed for crystal structure determination of the solvate from microcrystalline powder. The stability of the compound relative to other reported quercetin solvates is discussed and found to be in perfect agreement with the hydrogen bonding networks/supra-molecular architectures formed in each case.

Silver(I) 2,2'-(1,2-Phenylenedisulfanediyl)diacetic Acid as a Molecular Building Block for a Silver(I)-Cadmium(II) Coordination Polymer.

Starting from heterotopic multidentate ligand 2,2'-(1,2-phenylenedisulfanediyl)diacetic acid, (RS,RS,RS,RS/SS,SS,SS,SS)-[Ag{1,2-C6H4(SCH2COOH)2-κ2S,S'}2]BF4 (1) was prepared and further used as a building block for the synthesis of heterobimetallic Ag-Cd coordination polymer [Ag2Cd2{1,2-(OOCCH2S)2C6H4}3 (H2O)3·5H2O]n (2). Both complexes were characterized by X-ray structure analysis and conventional spectroscopic techniques.

N-Butyl-4-butyl-imino-2-methyl-pentan-2-aminium (E)-quercetinate.

The title salt, C(14)H(31)N(2) (+)·C(15)H(9)O(7) (-), was obtained in the reaction of quercetin with n-butyl-amine in a mixture of acetone and hexane. The crystal structure determination shows that the quercetin donates one of its phenol H atoms to the N-butyl-4-butyl-imino-2-methyl-pentan-2-amine mol-ecule. The crystal structure of the salt is stabilized by intramolecular (N-H⋯N for the cation and O-H⋯O for the anion) and intermolecular hydrogen bonding (N-H⋯O between cation-anion pairs and O-H⋯O between anions).