C-F...π, F...H, and F...F intermolecular interactions and F-aggregation: Role in crystal engineering of fluoroorganic compounds

Systematization of the available literature data on C-F...π, F...H, and F...F interactions, namely, statistical studies of the geometry of the corresponding contacts were carried out using the Cambridge Structural Database (CSD) and theoretical quantum-chemical estimations of their energies. The most typical supramolecular motifs (finite or infinite) involving the F atom were revealed based on recent X-ray studies of a few dozens of fluoroarenes carried out at the Novosibirsk Institute of Organic Chemistry. Our recent data were summarized. To assess the role of the above interactions, we used topological analysis of electron density distribution in terms of Bader’s QTAIM theory. Our DFT/PBE/3z quantum-chemical calculations of the interaction energies of molecular pairs in diazafluorene crystals formed by C-F...π, C-F...H, and F...F nonvalent short contacts are presented.     

Mixed micellization between natural and synthetic block copolymers: β-casein and Lutrol F-127

Amphiphilic block copolymers and mixtures of amphiphiles find broad applications in numerous technologies, including pharma, food, cosmetic and detergency. Here we report on the interactions between a biological charged diblock copolymer, β-casein, and a synthetic uncharged triblock copolymer, Lutrol F-127 (EO(101)PO(56)EO(101)), on their mixed micellization characteristics and the micelles' structure and morphology. Isothermal titration calorimetry (ITC) experiments indicate that mixed micelles form when Lutrol is added to monomeric as well as to assembled β-casein. The main driving force for the mixed micellization is the hydrophobic interactions. Above β-casein CMC, strong perturbations caused by penetration of the hydrophobic oxypropylene sections of Lutrol into the protein micellar core lead to disintegration of the micelles and reformation of mixed Lutrol/β-casein micelles. The negative enthalpy of micelle formation (ΔH) and cooperativity increase with raising β-casein concentration in solution. ζ-potential measurements show that Lutrol interacts with the protein micelles to form mixed micelles even below its critical micellization temperature (CMT). They further indicate that Lutrol effectively masks the protein charges, probably by forming a coating layer of the ethyleneoxide rich chains. Small-angle X-ray scattering (SAXS) and cryogenic-transmission electron microscopy (cryo-TEM) indicate relatively small changes in the oblate micellar shape, but do show swelling along the small axis of β-casein micelles in the presence of Lutrol, thereby confirming the formation of mixed micelles.     

C–H...O and C–H...N interactions in RNA structures

Small molecule studies indicate that C–H...X interactions (X: O,N) constitute weak H-bonds. We have performed a comprehensive analysis of their occurrence and geometry in RNA structures. Here, we report on statistical properties of the total set of interactions identified and discuss selected motifs. The distance/angle distribution of all interactions exhibits an excluded region where the allowed C–H...X angle range increases with an increasing H...X distance. The preferred short C–H...X interactions in RNA are backbone-backbone contacts between neighbour nucleotides. Distance/angle distributions generated for various interaction types can be used for error recognition and modelling. The axial C2′(H)...O4′ and C5′(H)...O2′ interactions connect two backbone segments and form a seven-membered ring that is specific for RNA. An AA base pair with one standard H-bond and one C–H...N interaction has been identified in various structures. Despite the occurrence of short C–H...X contacts their free energy contribution to RNA stability remains to be assessed. Received: 17 May 1998 / Accepted: 4 August 1998 / Published online: 2 November 1998     

Are halide...halide contacts a feature of rock-salts only?

The electron density distribution function in the crystalline hydroxylammonium chloride obtained using the high-resolution X-ray diffraction technique was analyzed by means of Bader's "atoms in molecule" theory. The anion-anion interactions in the crystal of this ionic material were examined and the energy of the Cl-...Cl- contacts was estimated on the basis of the experimental data. The results obtained coincide well with the theoretical calculations and the X-ray diffraction data for the rock-salts. The existence of such type of interactions was shown to be not the unique feature of inorganic salts with point charge cations.     

Comparative studies on a mesophilic and a thermophilic α-amylase

A comparative study was performed on thermal stability of mesophilic and thermophilic α-amylases, and the effects of various denaturing agents, organic solvents, and stabilizers were investigated. As expected, the thermophilic enzyme showed higher resistance toward denaturation in water as its natural medium, but such a difference could not be detected in nonaqueous environments. Furthermore, stability of these molecules was improved by including various stabilizing agents. Of the compounds tested, sorbitol provided the highest degree of protection, which was found to be owing to its effect on increasing T _m and its ability in totally preventing deamidation of amino acid residues in the protein molecules.     

Gene Cloning and Characterization of a Novel Salt-Tolerant and Glucose-Enhanced β-Glucosidase from a Marine Streptomycete

The gene BglNH encoding a β-glucosidase was cloned from a marine streptomycete. Sequence analysis revealed that BglNH encoded a 456-aa peptide with a calculated mass of 51 kDa. The deduced amino acid sequence of BglNH showed the highest identities of 61 % with known β-glucosidases and contained a catalytic domain which belonged to the glycoside hydrolase family 1. The gene BglNH was expressed in Escherichia coli and the recombinant enzyme (r-BglNH) was purified. The optimum pH and temperature of r-BglNH were pH?6.0 and 45 °C, respectively. The r-BglNH displayed the typical salt-tolerant and glucose-enhanced characteristics. Its activity was remarkably enhanced in the presence of 0.5 M NaCl (rose more than 1.6-fold) and 0.1 M glucose (rose more than 1.4-fold). Moreover, r-BglNH displayed good pH stability and metal tolerance. It remained stable after incubating with buffers from pH?4.0 to 10.0, and most metal ions had no significant inhibition on its activity. These properties indicate that r-BglNH is an ideal candidate for further research and industrial applications.     

Physical and chemical properties of a durably efficacious ammonium bicarbonate as a fertilizer and its yield-increasing mechanism

A new fertilizer of cocrystal type,known as durably efficacious ammonium bicarbonate (DEAB),has been developed by adding a certain amount of dicyandiamide (DCD) as an ammonia-stabilizing agent to ammonium bearbenate(AB)during the process of its production.As compared with AB,DEAB was found to have a reduction of direct volatilization loss by 53%,a fertilizer availability period prolonged from 35-45 to 90-110 d,and an increase in the rate of nitrogen in fertilizer being utilized by 5.9%-10.2%,and a saving of the amount of fertilizer to be ap-phed by 20%-30% for the same level of yield,or an increase of the crop yield by over 10% for the same level of ni-tregen fertilization;in addition,it was found to show usually a function of promoting the crop to early mature.It can be apptied as basal dressing all in one time to soil and thus also used as a labour-saving and crop yield-increasing fertil-izer for is non-mtertillage,plastics film covering and water-saving agriculture     

The formation of a neutral manganese(III) complex containing a tetradentate Schiff base and a ketone – synthesis and characterization

2-Benzoylphenolato-(2,2′-((2,2-dimethylpropane-1,3-diyl)bis((nitrilo)(phenylmethylidyne)))-diphenolato-manganese(III) methanol solvate, [Mn(C₃₁H₂₈N₂O₂)(C₁₃H₉O₂)]·CH₃OH (1), was synthesized and characterized by FTIR, UV–vis, TG-FTIR, TG/DSC, molar conductivity, magnetic moment measurement, and quantum chemical calculations. During the synthesis, partial hydrolysis of ligand is observed. The compound was obtained as amorphous, dark-brown powder. The effects of organic solvents of various polarities on the UV–vis spectra of ligands and complex were investigated. In addition, the IR and UV–vis spectra were also calculated and compared with the experimental data. A single crystal for analysis was obtained by dissolving the amorphous complex in methanol, and slow evaporation of solvent at 4 °C. Single-crystal X-ray analysis indicated that the methanol molecules are not incorporated into the crystal lattice after the recrystallization process ([Mn(C₃₁H₂₈N₂O₂)(C₁₃H₉O₂)] (2)). In the structure Mn(III) is surrounded by two nitrogens and four oxygens of deprotonated Schiff base and α-hydroxy ketone ligands, and adopts a distorted octahedral geometry.     

Synthesis,Crystal Structure and Photophysical properties of a Novel Molecule Containing a Triarylamine and an Oxadiazole Units

2-{3-[2-（4-N,N-Di-p-tolylaminophenyl)ethenyl]phenyl}-5-(4-bromophenyl)-1,3,4-oxadiazole(1) containing triarylamine and 2,5-diaryl-1,3,4-oxadiazole units was prepared by hornerWitting reactions.The structure of the compound was confirmed by ^1H NMR,IR ,MS and elemental analyses.The crystal structure of 1 was determined by X-ray diffraction analysis.UV absorpiton spectra and photoluminescent spectra were measured.     

Total Syntheses of 16a’-Homoleurosidine and 16a’-Homovinblastine

Vinblastine has been used in clinic as an anti-cancer agent. Due to its high cytotoxity, generation of vinblastine congeners as safe anti-cancer agents is always the interesting topic in medicinal chemistry. In the previous synthesis of vinblastine, it has been found that a higher energy conformation of vinblastine lacking cytotoxity and inhibition against tubulin polymerization, can be converted to its lower energy natural conformation on heating to 110 oC. The high temperature (110 oC) othe…     

Synthesis and structure of a new polyoxometalate-based inorganic–organic hybrid and application as a chemically bulk-modified electrode

A new Keggin-type polyoxometalate-based inorganic–organic hybrid, [Cu(H₂O)₂(daphen)]₂[SiW₁₂O₄₀]·9H₂O (1) (daphen?=?5,6-diamino-1,10-phenanthroline), was hydrothermally synthesized, and characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy, fluorescence spectra, and thermal analysis. Single-crystal X-ray diffraction analysis reveals that in 1, [SiW₁₂O₄₀]^4? is a tetradentate ligand with its four terminal oxygens coordinating to four Cu(II)–daphen fragments to form a 2D sheet with (4,4) topology. On the basis of the insolubility of 1 in water and common organic solvent and its reversible multielectron redox processes, 1 was used to fabricate a bulk-modified carbon paste electrode (1-CPE) by direct mixing. Electrochemistry indicated that 1-CPE is stable over hundreds of cycles and possessed electrocatalytic activity toward the reduction reactions of nitrite.     

Crystallographic and theoretical studies of 1-(1-naphthyl)-2-thiourea with intermolecular N-H...S heteroatom interaction and N-H...π interaction

A single crystal X-ray diffraction study of 1-(1-naphthyl)-2-thiourea (1) C₁₁H₁₀N₂S indicates crystallization in the monoclinic space group C2/c, Z = 8, with unit cell parameters a = 15.3864(14) Å, b = 7.6090(7) Å, c = 17.0836(16) Å, β = 91.7420(30)°. In the crystal structure, two components of 1 are connected via intermolecular NH...S hydrogen bonds (the N...S distance of 3.371 Å). In 1 there is an NH...π interaction (with the N...π distance of 3.804 Å and a possible N-H...π distance of 3.196 Å). The calculations of 1 at the B3LYP/cc-pVTZ, RHF/cc-pVTZ, RIMP2/cc-pVDZ, and RIMP2/cc-pVTZ levels of theory can almost reproduce the X-ray geometry. In addition, the binding energies of a dimer of 1 calculated by RIMP2 using the cc-pVDZ and cc-pVTZ corrected BSSE basis sets are ?36.1 kJ/mol and ?41.7 kJ/mol. The results suggest that complex 1 is significantly important for the attractive intermolecular interaction in 1.     

Synthesis and characterization of a monomeric and a dihydroxo-bridged dimeric complexes of iron(III) with α-benzoinoxime

The reaction of α-benzoinoxime, H₂BNO with FeCl₃ in the presence of Et₃N as a base gives the mononuclear Fe(III) complex, Fe(HBNO)₃ (1). Treatment of 1 with a methanolic solution of KOH at room temperature leads to a dinuclear Fe(III)–Fe(III) complex, [Fe(HBNO)₂OH]₂ (2). The complexes were initially characterized on the basis of their elemental, mass and thermal analyses. The IR studies were useful in assigning the coordination mode of the benzoinoxime ligand to the iron metal. In addition, the presence of a hydroxo-bridge in the dimeric complex 2 is inferred from the IR spectral studies. Room-temperature Mössbauer studies indicated octahedral, high-spin iron(III). Variable-temperature magnetic susceptibility measurements supported the existence of the μ-dihydroxo-bridging structure core, Fe^III(μ-OH)₂Fe^III in the dinuclear complex 2. Theoretical modelling of the magnetic data indicated a weak antiferromagnetic spin exchange between the iron(III) centers (J = −8.35 cm⁻¹, g = 2.01, ρ = 0.02 and TIP = 1.7 × 10⁻⁴ cm³ mol⁻¹ for H = −2JS₁ · S₂). The electronic spectra of the complexes revealed two bands due to d–d transitions and one band assignable to an oxygen (p_π) → Fe(d_π∗) LMCT transition observed in each complex. An additional charge-transfer transition, assignable to μ-hydroxo(p_π) → Fe(d_π∗), was observed for the dimeric complex 2. The structural and vibrational behaviors of these complexes have been elucidated with quantum mechanical methods.     

Synthesis and Characterization of a Novel Galactosylated Cholesterol

Mammalian hepatocytes (parenchymal cells) exclusively possess large number ofasialoglycoprotein receptors (ASGPr), which can recognize terminal D-galactose orN-acetylgalactosamine residues. Lactobionic acid 1, bearing a galactosyl group, isusually used as…     

Synthesis and Properties of a Novel Photochromic Compound

A new photochromic compound containing pyrazolone-ring was synthesized, and its crystal structure was determined on X-ray singlecrystal diffraction, which belongs to monoclinic crystal system, space group P21/c. The UV spectrum of the compound is studied.     

Molecular Design and Immunogenicity of a Multiple-epitope FMDV Antigen and DNA Vaccination

This article reports the design and construction of a multiple-epitope foot and mouth disease virus （FMDV） antigen, designated as OAAT. This recombinant antigen consists of the structural protein VP1 genes from serotypes A and O FMDV, five major VP1 immunodominant epitopes from two genotypes of Asial serotype, and three Th2 epitopes originating from the nonstructural protein, three ABC gene and structural protein VP4 gene. Expressions of target gene from these plasmids in HeLa cells were verified by Western-blot. BALB/c mice were immunized intramuscularly with the DNA vaccines thrice every two weeks. We found that pA could induce simultaneously specific antibodies against serotypes A, Asial, and O FMDV. Compared to those of the controls, the spots of FMDV-specific IFN-7 and cytotoxic activity from mice immunized with pA were significantly increased, pA provided full protection in 2/4 guinea pigs from challenge with FMDV O/NY00 and Asial/YNBS/58, respectively. The results show that although pA did not give full protection in 100% immunized guinea pigs from challenge with type O and Asial FMDV, respectively, OAAT may be potential immunogen against FMDV and pA may be potential DNA vaccines against FMDV.     

Synthesis and structure of a boron cation supported by a β-diketiminate ligand

The salt [HC(CMe)₂(NAr)₂BPh][Al₂Cl₇] (3); Ar = 2,6-i-Pr₂C₆H₃) has been synthesized via the in situ preparation of [HC(CMe)₂(NAr)₂BClPh], followed by treatment with AlCl₃. X-ray analysis of 3 reveals that the BN₂C₃ ring of the boron cation is planar and DFT calculations indicate π-type interactions in the HOMO-6 and HOMO-7 orbitals.     

Synthesis and Structure of a Novel Disulfide-Containing Aniline

A novel disulfide-containing aniline, 8-dihydro-1H,4H-2,3,6,7-tetrathia-anthracen-9-ylamine (5) was synthesized.The single-crystal X-ray analysis of 4 indicates that the molecular has a non-planar structure, with its four sulfur atoms out of the plane of benzene ting. The designed molecular has the advantage of high theoretic specific capacity and reversibility,[1,2] when it is to be polymerized and used as the cathode material of the secondary lithium batteries.