Cubic phases of binary systems of 4′-n-tetradecyloxy-3′-nitrobiphenyl-4-carboxylic acid (ANBC-14)-n-alkane

The phase behaviour of the binary systems 4′- ⁿ -tetradecyloxy-3′-nitrobiphenyl-4-carboxylic acid (ANBC-14)- ⁿ -alkane ( ⁿ -tetradecane or ⁿ -hexadecane) was investigated by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. The phase behaviour was a function of temperature ( ^T ) and the effective carbon number of the system ( ^n*), where ^n* involves carbon atoms both from the alkoxy group of ANBC-14 and from the ⁿ -alkane added. ANBC-14 shows no cubic phase, but the addition of ⁿ -alkane induced cubic phases when ^n*≧c. 15. An interesting point is that the type of cubic phase is ^Ia 3 ^d for 15^≦n*≦17, while an ^Im 3 ^m type is formed for 18^≦n*≦20. Furthermore, for ^n* = 22, two types of cubic phase, one with ^Im 3 ^m symmetry in the low temperature region and the other with ^Ia 3 ^d in the high temperature region, were observed both on heating and cooling. The phase diagram with respect to ^T and ^n* is very similar to that of pure one-component ANBC- ⁿ , which is a function of ^T and the number of carbon atoms in the alkoxy group ⁿ .     

Cubic phases of 4′-n-alkoxy-3′-nitrobiphenyl-4-carboxylic acids (ANBC-n)

The structure of the thermotropic cubic phases of 4′- ⁿ -alkoxy-3′-nitrobiphenyl-4-carboxylic acids (ANBC- ⁿ , where ⁿ indicates the number of carbon atoms in the alkoxy group) was studied by X-ray diffraction. For the homologues with ⁿ = 15, 16, 17, and 18, the cubic phase was of an ^Ia 3 ^d type, whereas the homologues with ⁿ = 19, 20, and 21 exhibited an ^Im 3 ^m cubic structure; for these seven homologues the same type of cubic structure was observed both on heating and cooling. Further lengthening of the alkoxy chain to ⁿ = 22 and 26, however, gave two types of cubic structure in the cubic phase region on heating, one with ^Im 3 ^m symmetry in the low temperature region and the other with ^Ia 3 ^d symmetry in the high temperature region. On cooling, the two homologues exhibited the ^Ia 3 ^d cubic structure only. This is the first example in the cubic phase region of a series of homologues containing two types of structure, dependent on temperature and ⁿ . Such a complicated phase diagram in the cubic region is clearly understood qualitatively in terms of Gibbs free energy-temperature diagrams. The dependence of structural parameters such as the cubic lattice constant on the alkoxy chain length ⁿ are also presented and discussed.     

Resolution and determination of the absolute configuration of 3,3′4,4′-tetramethyl-1,1′-diphosphaferrocene-2-carboxylic acid

(±)-3,3′4,4′-Tetramethyl-1,1′-diphosphaferrocene-2-carboxylic acid 1 was resolved via diastereomeric salts with brucine. The (R)-absolute configuration of (+)-1 was determined by X-ray crystallography.     

The rate of cyclization of 2′- and 4′-substituted diphenylamine-2-carboxylic acids in sulfuric acid as a function of the electronic properties of substituents

The kinetic regularities of cyclization of 2′- and 4′-substituted diphenylamine-2-carboxylic acids in sulfuric acid were determined. The rate of cyclization of diphenylamine-2-carboxylic acids is linearly dependent on the nature of substituents in the meta-position relative to the reaction site in accordance with the two-parameter Hammett equation.     

An improved phosphoramidite approach for the chemical synthesis of 3′,5′-cyclic diguanylic acid

3′,5′-Cyclic diguanylic acid (c-di-GMP) plays important roles as a signaling and effector molecule in prokaryotes as well as inducing innate and adaptive immune responses in mammalian cells through activation of cell death pathways. An improved phosphoramidite method for the synthesis of c-di-GMP is reported herein. The method is based on the use of an unprecedented 5′-O-formyl ester, which can efficiently and chemoselectively be cleaved from a dinucleotide phosphoramidite intermediate to permit a 1H-tetrazole-mediated cyclocondensation reaction leading to a fully protected c-di-GMP product in a yield of 78%. The native c-di-GMP is isolated in an overall yield of 36% based on the commercial ribonucleoside used as starting material.     

In situ introduction of dispersed metallic Ag nanoparticles into the channels of mesoporous carbon CMK-3

An in situ reduction method has been developed to fabricate metallic Ag nanoparticles inside the channels of mesoporous carbon CMK-3.This approach combines function of the CMK-3 surface by oxidation using HNO_3 with the subsequent absorption of Ag~ . The resultant nanocomposite materials were characterized by nitrogen adsorption,X-ray diffraction,Auger electron spectroscopy and transmission electron microscopy.Compared with the conventional impregnation method,our approach shows that Ag nanoparticles of 2-4 nm can be uniformly incorporated into CMK-3.     

In situ construction of ligand nano-network to integrin αvβ3 for angiogenesis inhibition

Angiogenesis occurs during the process of tumor growth, invasion and metastasis, and is essential for the survival of solid tumors. As an integrin significantly overexpressed in human tumor vascular endothelial cells, α_vβ₃ is a suitable targeting site for anti-angiogenesis of tumor. We designed and prepared a self-assembling peptide (SAP) with the ability to targeting α_vβ₃ and self-assembly. SAP formed nanoparticles in solution and transformed into nanofibrous network once specifically binding to integrin α_vβ₃ on the surface of human umbilical vein endothelial cells (HUVECs). The SAP network stably anchored on HUVECs over 24 h, which consequently resulted in high-efficient inhibition of vascularization. In vitro anti-angiogenesis experiment displayed that the inhibition rate of tube-formation reached 94.9%. In vivo anti-angiogenesis array based on chick chorioallantoic membrane (CAM) model exhibited that the SAP had an inhibition rate up to 63.1%. These results indicated the outstanding anti-angiogenic ability of SAP, potentially for tumor therapy.     

Three-component condensation of 2-aminothiophene-3-carboxylic acid derivatives with aldehydes and Meldrum’s acid

New approach to the synthesis of 4,7-dihydro-5H-thieno[2,3-b]pyridin-6-ones using 2-aminothiophenes unsubstituted at position 3 of the thiophene ring has been developed. Labile 2-aminothiophenes have been obtained by the in situ decarboxylation of unstable 2-amino-3-thiophenecarboxylic acids. The three-component condensation of 2-aminothiophenes with aromatic aldehydes and the Meldrum’s acid is the key step of the process.     

In situ synthesis and structure of FeCl4(4,4′-diethyl-4,4′-bipyh) (bipy = bipyridine)

A novel viologen(4,4′-bipyridinium)-based compound FeCl₄(4,4′-diethyl-4,4′-bipyH) (1) (bipy = bipyridine), in which 4,4′-diethyl-4,4′-bipyH (MQ ⁺) was generated in situ, is synthesized via the hydrothermal reaction and structurally characterized by single crystal X-ray diffraction. The crystal structure analysis reveals that the title compound features an isolated structure based on 4,4′-diethyl-4,4′-bipyH moieties and an iron atom terminally bound by four chlorine atoms. The 4,4′-diethyl-4,4′-bipyH moieties and (FeCl₄)^? anions are interconnected by hydrogen bonds to form a 3D supramolecular framework.     

Three-component condensation of 3-aminothiophene-2-carboxylic acid derivatives with aldehydes and Meldrum’s acid

A convenient method was developed for the synthesis of the previously unknown substituted 6,7-dihydro-4H-thieno[3,2-b]pyridin-5-ones based on the three-component condensation of 3-aminothiophenes, Meldrum’s acid, and aromatic aldehydes. 3-Aminothiophenes are easily formed in situ by decarboxylation of 3-aminothiophene-2-carboxylic acids in an acidic medium. Sodium salts of the latter acids were prepared by alkaline hydrolysis of the corresponding available esters.     

Amino acid derivatives of 2-R-7-hydroxy-3′,4′-ethylenedioxyisoflavones

A number of 7-O-aminoacyl derivatives of isoflavones have been obtained by the interaction of 2-R-7-hydroxy-3,4-ethylenedioxyisoflavones with the symmetrical anhydrides of N-protected amino acids.Kiev Tara Shevshenko University, Ukraine, 252033, Kiev, Ul. Vladimirskaya, 64, tel./fax 225-12-73. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 334–338, May–June, 1999.     

Application of a novel 1,1′-dimethylferricinimum dye for the determination of uric acid in urine

Water-soluble 2-hydroxypropyl-β-cyclodextrin (Hp-β-CyD), a cyclic and nonreducing oligosaccharide was used to enclose a hydrophobic guest molecule 1,1′-dimethylferrocene (DMF) to form a water-soluble yellow complex. At high concentrations (300 mM), Hp-β-CyD enclosed up to 100 mM DMF. The yellow complex was electrochemically oxidized (platinum vs Ag/AgCl poised at +450 mV) to form a blue dye, 1,1′-dimethylferricinium (DMF⁺). This is a one-electron transfer process and the ferricinium cation formed exhibited an absorption peak at 650 nm. The concentrated DMF⁺ was stable for at least 4 mo at 4°C and insensitive to a wide pH variation (pH 2–11). Application of the novel DMF⁺ complex as a colorimetric dye for the determination of uric acid in urine was successfully demonstrated. The reaction between the dye and uric acid is almost instantaneous and decrease in absorbance caused by the reduction of 1,1′-dimethylferricinium to 1,1′-dimethylferrocene can be followed at 650 nm. The results obtained agreed well with those of the reference reversed-phase HPLC method.     

In situ formation of porous mineral–polymer scaffold for tissue engineering

A principle of three-dimensional printing of composite materials with structure and properties close to natural human tissues was implemented. It was found that the inorganic component, dicalcium phosphate dihydrate, crystallizes in the bulk of alginate matrix. The subsequent chemical treatment of experimental samples in buffered solutions promoted the formation of octacalcium phosphate on the surface of pore space of the printed material.     

Molecular and crystal structure of 2,3-dimethyl-5-(2′-methylprop-1′-enyl)-6-(morpholyl-4′-carbonyl)-cyclohex-3-en-1-carboxylic acid

An X-ray structural examination is carried out for 2,3-dimethyl-5-(2′-methylprop-1′-enyl)-6-(morpholyl-4′-carbonyl)-cyclohex-3-en-1-carboxlic acid that is one of the products of the Diels-Alder reaction of an acyclic monoterpene alloocimene with maleic and citraconic anhydrides followed by the ring opening of adducts with morpholine to corresponding amides. The crystals are triclinic; a = 10.619(1) ?, b = 12.784(2) ?, c = 14.328(2) ?; α = 65.752(1)°, β = 87.932(1)°, γ = 78.120(1)°; V = 1733.0(3) ?³, P-1 space group, Z = 4 (two independent molecules). In both molecules, the anti-conformation of the carboxylic group is observed, the conformation being stabilized by an intramolecular hydrogen bond involving the carboxylic hydrogen atom and ketonic oxygen.     

Amperometric Immunosensor for the Determination of 2′,3′-dideoxyinosine

Abstract

An amperometric immunosensor, based on carbon paste impregnated with solubilized antidideoxyinosine (from rabbit lyophilized powder, whole antiserum) has been constructed for the assay of anti-HIV agent dideoxyinosine (didanosine, DDI). The amperometric immunosensor was reliably used for dideoxyinosine assay in the 900 pmol/L to 9 nmol/L concentration range, with a detection limit of 180 pmol/L, at E = +1.04 V vs. Ag/AgCl. The construction of the immunosensor is reproducible. Its surface can be easily renewed by simple polishing on an aluminium paper. The new amperometric immunosensor is reliable for the assay of 2′,3′-dideoxyinosine in raw material as well as in its pharmaceutical formulation (Videx tablets).     

Three-component condensation of 3-aminothiophene derivatives with isatines and Meldrum’s acid. Synthesis of 2,5′-dioxo-3′-phenyl-5′,6′-dihydro-4′H-spiro[indoline-3,7′-thieno[3,2-b]pyridine]-2′-carboxylic acids

A method for the synthesis of 2,5′-dioxo-3′-phenyl-5′,6′-dihydro-4′H-spiro[indoline-3,7′-thieno[3,2-b]pyridine]-2′-carboxylic acids was elaborated based on the three-component condensation of 3-aminothiophenes, Meldrum’s acid, and isatines.     

In situ electrochemical contact angle study of hemoglobin and hemoglobin–Fe3O4 nanocomposites

The electrochemical redox-induced contact angle changes of hemoglobin droplets in the absence and presence of tetraheptylammonium-capped Fe₃O₄ nanoparticles have been explored by using in situ electrochemical contact angle measurements. The results indicate that the electrochemical redox process may lead to some structure changes of hemoglobin (Hb), which could further induce the hydrophobic-to-hydrophilic changes of the relative droplets. Our observations demonstrate that hemoglobin could self-assemble on the surface of the functionalized Fe₃O₄ nanoparticles as Hb–Fe₃O₄ nanocomposites, which may contribute to much more significant change of the electrochemical redox-induced contact angle values than that with free nano-Fe₃O₄. These results suggest that in situ electrochemical contact angle measurements could be readily applied as a new and convenient method to detect some specific biological process. Figure Schematic drawing of the possible process and contact angle changes for the self-assembly of hemoglobin on the tetraheptylammonium-capped Fe₃O₄ nanoparticles Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.