Surface plasmon resonance for real-time study of lectin-carbohydrate interactions for the differentiation and identification of glycoproteins

A study of specific interactions between lectins and glycoproteins has been carried out using surface plasmon resonance (SPR) in a flow-injection mode. Lectins were covalently immobilised on the surfaces of the microfluidic sensor chip via amine coupling and serum glycoproteins were injected into the flow channels. Specific lectin-glycoprotein interactions caused the shift of refractive index proportional to the mass concentration accumulated on the channel surface. Lectins showed different affinity to the tested glycoproteins and each glycoprotein displayed its own lectin-binding pattern. It is possible to distinguish and identify even glycoproteins with similar sugar structures by simple and quick screening. The working conditions of the assay were optimised. The lectin-based SPR made it possible to carry out the label-free detection of glycoproteins within a broad concentration range with a good linearity. Regeneration conditions for the surface of the sensor chip were found and optimised. Combination of 10 mM HCl and 10 mM glycine-HCl (pH 2.5) removes the bound glycoproteins from the lectin surface without damaging it. The kinetic and affinity parameters of lectin-glycoprotein binding were evaluated. The proposed method was tested on human glycosylated serum. Combination of the lectin panel with SPR is suitable both for specific screening and for sensitive assay of serum glycoproteins.     

Photoacid generators (PAGs) based on N-acyl-N-phenylhydroxylamines for carboxylic and sulfonic acids

Simple and efficient photoacid generators (PAGs) for carboxylic and sulfonic acids based on N-acyl-N-phenylhydroxylamines have been demonstrated. Irradiation of o-carboxylates and thermally rearranged o-arenesulfonates of N-acyl-N-phenylhydroxylamines using UV light (≥254 nm) in aqueous methanolic solution resulted in efficient generation of carboxylic and sulfonic acids, respectively. The carboxylic acid generation ability of N-acyl-N-phenylhydroxylamines was found to be dependent on their N-acyl substituents. Further, polymer bearing o-arenesulfonates of N-acyl-N-phenylhydroxylamine was synthesized and demonstrated as PAG for sulfonic acids.     

Thermodynamic Study of Poly(ethylene glycol) in Water/1-Propanol Solutions by Viscometry

In this work, the intrinsic viscosities of poly(ethylene glycol) with a molar mass of 20 kg⋅mol⁻¹ were measured in water/1-propanol solutions from 283.1 to 313.1 K. The expansion factors of the polymer chains were calculated from the intrinsic viscosity data. The thermodynamic parameters entropy of dilution parameter, the heat of dilution parameter, theta temperature, polymer–solvent interaction parameter and second osmotic virial coefficient were derived from the temperature dependence of the polymer chain expansion factor. The thermodynamic parameters indicate that mixtures of water/1-propanol become weaker solvents for poly(ethylene glycol) with increasing temperature. Also, the thermodynamic parameters indicate that the solvent ability of mixed water/1-propanol for poly(ethylene glycol) is less than that of pure water.     

Synthesis, characterization and optical band gap of NiO nanoparticles derived from anthranilic acid precursors via a thermal decomposition route

This study focuses on the preparation and characterization of single phase NiO nano particles. Four nickel anthranilic acid complexes were synthesized by the semi-solid phase reaction method as precursors for the preparation of NiO nanoparticles via a solid-state decomposition procedure at 700 °C. Thermogravimetric analysis (TGA) was applied to determine the thermal behavior of the precursors and the temperature at which the precursors decompose leaving the oxide. The crystalline structures of the products were investigated by X-ray diffraction (XRD), the morphology of particles by SEM and TEM. The particles size was determined by STM, and the average particle size was found to be 8 nm. Electronic spectra were used to clarify qualitatively the change in absorption band positions on changing the particle size of NiO. The optical band gap of the NiO nanoparticles was calculated and indicated a direct transition. The values of the optical band gap of NiO nanoparticles increase as the particle size decreases.     

Synthesis and characterization of platinum(II) di-ynes and poly-ynes incorporating ethylenedioxythiophene (EDOT) spacers in the backbone

A series of trimethylsilyl-protected di-alkynes incorporating 3,4-ethylenedioxythiophene (EDOT) linker groups Me(3)Si-C≡C-R-C≡C-SiMe(3) (R = ethylenedioxythiophene-3,4-diyl 1a, 2,2'-bis-3,4-ethylenedioxythiophene-5,5'-diyl 2a, 2,2',5',2'-ter-3,4-ethylenedioxythiophene-5,5'-diyl 3a) and the corresponding terminal di-alkynes, H-C≡C-R-C≡C-H 1b-2b has been synthesized and characterized and the single crystal X-ray structure of 1a has been determined. CuI-catalyzed dehydrohalogenation reaction between trans-[(Ph)(Et(3)P)(2)PtCl] and the terminal di-alkynes 1b-2b in (i)Pr(2)NH/CH(2)Cl(2) (2:1 mole ratio) gives the Pt(II) di-ynes trans-[(Et(3)P)(2)(Ph)Pt-C≡C-R-C≡C-Pt(Ph)(Et(3)P)(2)] 1M-2M while the dehydrohalogenation polycondensation reaction between trans-[((n)Bu(3)P)(2)PtCl(2)] and 1b-2b (1:1 mole ratio) under similar reaction conditions affords the Pt(II) poly-ynes trans-[Pt(P(n)Bu(3))(2)-C≡C-R-C≡C-](n)1P-2P. The di-ynes and poly-ynes have been characterized spectroscopically and, for 1M and 2M, by single-crystal X-ray which confirms the "rigid rod" di-yne backbone. The materials possess excellent thermal stability, are soluble in common organic solvents and readily cast into thin films. Optical absorption spectroscopic measurements reveal that the EDOT spacers create stronger donor-acceptor interactions between the platinum(II) centres and conjugated ligands along the rigid backbone of the organometallic polymers compared to the related non-fused and fused oligothiophene spacers.     

Intramolecular excimer formation for covalently linked boron dipyrromethene dyes

Photophysical properties have been recorded for a small series of covalently linked, symmetrical dimers formed around boron dipyrromethene (Bodipy) dyes. Within the series, a control dimer is unable to adopt a cofacial arrangement because of steric factors, while a second dimer possesses sufficient internal flexibility to form the cofacial geometry but with little overlap of the Bodipy units. The other three members of the series take up a cofacial arrangement with varying bite angles between the planes of the two Bodipy units. Fluorescence quantum yields and excited-state lifetimes indicate differing extents of electronic interaction between the two Bodipy head-groups, but only the compound with the smallest bite angle exhibits excimer emission in solution under ambient conditions. Time-resolved fluorescence studies show dual-exponential decay kinetics in each case, while temperature-dependent emission studies reveal reversible coupling between monomer and lower-energy excimer states. The latter is weakly fluorescent, at best, and is seen clearly only for dimers having small bite angles. The application of high pressure to dilute solutions of these dimers promotes excimer formation in certain cases and leads to loss of monomer-like fluorescence. Under high pressure, excimer emission is more evident, and the overall results can be discussed in terms of subtle structural rearrangements that favor excimer formation.     

Flavonoid-DNA binding studies and thermodynamic parameters

Interactional studies of new flavonoid derivatives (Fl) with chicken blood ds.DNA were investigated spectrophotometrically in DMSO-H2O (9:1 v/v) at various temperatures. Spectral parameters suggest considerable binding between the flavonoid derivatives studied and ds.DNA. The binding constant values lie in the enhanced-binding range. Thermodynamic parameters obtained from UV studies also point to strong spontaneous binding of Fl with ds.DNA. Viscometric studies complimented the UV results where a small linear increase in relative viscosity of the DNA solution was observed with added optimal flavonoid concentration. An overall mixed mode of interaction (intercalative plus groove binding) is proposed between DNA and flavonoids. Conclusively, investigated flavonoid derivatives are found to be strong DNA binders and seem to be promising drug candidates like their natural analogues.     

Fibronectin conformation switch induced by coadsorption with human serum albumin

The dynamic adsorption of human serum albumin (HSA) and plasma fibronectin (Fn) onto hydrophobic poly(hydroxymethylsiloxane) (PHMS) and the structures of adsorbed protein layers from single and binary protein solutions were studied. Spectroscopic ellipsometry (SE) and quartz crystal microbalance with dissipation monitoring (QCM-D) together with atomic force microscopy (AFM) were used to measure the effective mass, thickness, viscoelastic properties, and morphology of the adsorbed protein films. Adsorbed HSA formed a rigid, tightly bound monolayer of deformed protein, and Fn adsorption yielded a thick, very viscoelastic layer that was firmly bound to the substrate. The mixed protein layers obtained from the coadsorption of binary equimolecular HSA-Fn solutions were found to be almost exclusively dominated by Fn molecules. Further sequential adsorption experiments showed little evidence of HSA adsorbed onto the predeposited Fn layer (denoted as Fn ? HSA), and Fn was not adsorbed onto predeposited HSA (HSA ? Fn). The conformational arrangement of the adsorbed Fn was analyzed in terms of the relative availability of two Fn domains. In particular, (4)F(1)·(5)F(1) binding domains in the Hep I fragment, close to the amino terminal of Fn, were targeted using a polyclonal antifibronectin antibody (anti-Fn), and the RGD sequence in the 10th segment, in the central region of the molecule, was tested by cell culture experiments. The results suggested that coadsorption with HSA induced the Fn switch from an open conformation, with the amino terminal subunit oriented toward the solution, to a close conformation, with the Fn central region oriented toward the solution.     

Design,synthesis and molecular docking of new [1,2,4] triazolo[4,3-a]quinoxaline derivatives as anticancer agents targeting VEGFR-2 kinase

Molecular Diversity - Vascular endothelial growth factor receptor-2 (VEGFR-2) is critically involved in cancer angiogenesis. Blocking of VEGFR-2 signaling pathway proved effective suppression of...