Reduction of the concentration difference of proteins in biological liquids using a library of combinatorial ligands

The discovery of polypeptides and proteins with relevance to a particular biological state is complicated by their vast number and concentration range in most biological mixtures. Depletion methodologies are frequently used to remove the most abundant species; however, this removal not only fails significantly to enrich trace proteins, it may also nonspecifically deplete them due to their interactions with the removed high-abundance proteins. Here we report a simple-to-use methodology that reduces the protein concentration range of a complex mixture like whole serum through the simultaneous dilution of high-abundance proteins and the concentration of low-abundance proteins. This methodology utilizes solid-phase ligand libraries of immense diversity, generated by "split, couple, recombine" combinatorial chemistry, that are used for affinity-based binding to the proteins of a given mixture. With a controlled sample-to-ligand ratio it is possible to modulate the relative concentration of proteins such that many peptides or proteins that are undetectable by classical analytical methods become easily accessible. The reduction in the dynamic range of unfractionated serum is specifically described along with treatment of other proteomes such as extracts from Escherichia coli, chicken egg white and cell culture supernatant. Mono- and bi-dimensional electrophoresis (1-DE and 2-DE respectively) and surface-enhanced laser desorption/ionization-mass spectrometry (SELDI-TOF-MS) technology demonstrate the reduction in protein concentration range. Combining this approach with additional fractionation methods further increased the number of detectable species.     

Spectroscopic and theoretical studies of derivatives of 1,6- and 1,7-naphthyridines

The solvatochromism in 8-hydroxy-1,6-naphthyridin-5(6H)-one-7-carboxylic acid methyl ester (1), 5-hydroxy-1,7-naphthyridin-8(7H)-one-6-carboxylic acid methyl ester (2), and 4-hydroxy-2-methyl-1(2H)-isoquinolone-3-carboxylic acid methyl ester (3), has been studied in solvents of different polarity and hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) ability. The relative stabilities of isomers for these naphthyridine derivatives and their interaction with the solvent are reported. Two intramolecular hydrogen-bonded structures contribute to the ground state of compound 1. Temperature effects on the absorption bands were recorded to analyse the possible equilibrium between covalent and zwitterionic forms. The formation of zwitterionic species was observed only in HBD solvents, from which is inferred the solvent assistance in the proton transference. AM1 and PM3 semi-empirical calculations were used in support of the proposed interpretations.     

A comparison of 3,4,6a,7,10,10a‐hexahydro‐7,10‐epoxypyrimido[2,1‐a]isoindol‐6(2H)‐one and 2‐(2‐aminoethyl)‐3a,4,7,7a‐tetrahydro‐1H‐4,7‐epoxyisoindole‐1,3(2H)‐dione: structural and reactivity differences of two homologous tricyclic imides

The crystal structures of 3,4,6a,7,10,10a‐hexahydro‐7,10‐epoxypyrimido[2,1‐a]isoindol‐6(2H)‐one, C₁₁H₁₂N₂O₂, and 2‐(2‐aminoethyl)‐3a,4,7,7a‐tetrahydro‐1H‐4,7‐epoxyisoindole‐1,3(2H)‐dione, C₁₀H₁₂N₂O₃, two tricyclic imides, show one and two molecules in the asymmetric unit, respectively. Intermolecular hydrogen‐bonding interactions are observed in both compounds.     

A new calcium 2,5-dihydroxybenzoate: Synthesis,characterization and antioxidant studies and stress mediated cytotoxity in MCF-7 cells

The structure and composition of the calcium 2,5-dihydroxybenzoate (calcium gentisate) were studied by single-crystal and powder X-ray diffraction. Single-crystal X-ray analysis revealed that the compound crystallizes in the orthorhombic space group Pbcn. The Ca(II) cation is coordinated in a monodentate fashion by two symmetry-related gentisate anions and five water molecules. The metal ion and one of the water molecules are located on a 2-fold rotation axis. The adjacent monomeric units are assembled into a 3-D supramolecular framework via O–H…O hydrogen bonds. Comparison of the experimental powder pattern with that simulated from single-crystal X-ray data confirmed the purity and homogeneity of the sample. The FT-IR, UV/VIS, ¹H and ¹³C NMR spectra of the calcium 2,5-dihydroxybenzoic acid were registered and analysed. Moreover the effect of calcium complex and 2,5-dihydroxybenzoic acid on basic oxidative stress parameters, such as thiol group content and lipid peroxidation in the human breast cancer cells MCF-7 was studied. The antiradical and ferric reducing power of these compounds was measured by DPPH, CUPRAC and FRAP methods. The chemical reactivity parameters (e.g. HOMO and LUMO orbitals, ionization potential, electron affinity) for Ca 2,5-dHB and 2,5-dHB were calculated at B3LYP/6-311++G7 level of theory and discussed in relation to their antioxidant properties.     

Selective Formation of Methyl α-Methylsulfanyl Dimethylphosphonothioacetate and Thiopropanoate by Phase Transfer Catalysis

The sulfanylation of methyl dimethylphosphonothioacetate was investigated by a phase transfer catalysis procedure which was shown to be superior to the noncatalytic method. The possibility of electrophilic substitution of the α-sulfanylated phosphonothioacetate to give a quaternary α-carbon atom is shown by the reaction with methyl iodide.

     

Diaqua­bis[4‐(4H‐1,2,4‐triazol‐4‐yl)­benzoato‐κ2O,O′]cobalt(II), and the cadmium(II) and copper(II) analogues: new self‐complementary hydrogen‐bond donor/acceptor modules for designing hydrogen‐bonded frameworks

In the isostructural title complexes, [M(C₉H₆N₃O₂)₂(H₂O)₂] [M = Co^II, (I), Cd^II, (II), and Cu^II, (III); the metal centres reside on a twofold axis in the space group C2/c for (I) and (II)], the metal centres are surrounded by four O atoms from two O,O′‐bidentate carboxyl­ate groups and by two trans‐coordinated aqua ligands, forming a distorted octa­hedral environment. The mol­ecules possess four hydrogen‐bond donor (two aqua ligands) and four hydrogen‐bond acceptor sites (two triazole groups), and aggregate by self‐association, forming two‐dimensional hydrogen‐bonded frameworks [via O—H⋯N inter­actions; O⋯N = 2.749 (3)–2.872 (3) Å]. The layers are parallel and are tightly packed with short inter­layer distances of 4.93, 4.95 and 5.01 Å for (I), (II) and (III), respectively.     

Immersion enthalpy and the constants of Langmuir model in the 3-chloro phenol adsorption on activated carbon

The adsorption process of 3-chloro phenol from aqueous solution on a activated carbon prepared from African palm stone and which presents a specific surface area of 685 m² g⁻¹, a greater quantity of total acid groups and a pH_PZC of 6.8 is studied. The adsorption isotherms are determined at pH values of 3, 5, 7, 9 and 11. The adsorption isotherms are fitted to the Langmuir model and the values of the maximum quantity adsorbed that are between 96.2 and 46.4 mg g⁻¹ are obtained along with the constant K_L with values between 0.422 and 0.965 L mg⁻¹. The maximum quantity adsorbed diminishes with the pH and the maximum value for this is a pH of 5. The immersion enthalpies of the activated carbon in a 3-chloro phenol solution of constant concentration, of 100 mg L⁻¹, are determined for the different pH levels, with results between 37.6 and 21.2 J g⁻¹. Immersion enthalpies of the activated carbon in function of 3-chloro phenol solution concentration are determined to pH 5, of maximum adsorption, with values between 28.3 and 38.4 J g⁻¹, and by means of linearization, the maximum immersion enthalpy is calculated, with a value of 41.67 J g⁻¹. With the results of the immersion enthalpy, maximum quantity adsorbed and the constant K_L, establish relations that describe the adsorption process of 3-chloro phenol from aqueous solution on activated carbon.     

Immersion enthalpy of carbonaceous samples in aqueous solutions of monohydroxilated phenols

The immersion enthalpies of modified activated carbons were determined, with commercial Carbochem^TM–PS230 (CAG) as the initial activated carbon, which was modified by: chemical treatment with HNO₃ 7 mol L⁻¹ (CAO) and thermal treatment under flow of H₂ (CAR) in function of the adsorbed quantity of monohydroxilated phenols, catechol, resorcinol and hydroquinone at a pH of 7 in aqueous dissolutions in order to characterize the solid–solution interaction and evaluate the influence of the chemical characteristics of the activated carbon in the phenol adsorption. The results show a variation in the immersion enthalpy in function of the adsorbed quantity of phenol and the initial dissolution concentration; which shows that the intensity of the interaction changes in function of the composition of the liquid phase. The immersion enthalpies present the following arrangement: catechol > resorcinol > hydroquinone, with a −ΔH_inm of 35.7; 30.8 and 24.6 Jg⁻¹, respectively, at a pH of 7 for a 100 mg L⁻¹ phenol monohydroxilated solution.     

Oil-loaded monolinolein-based particles with confined inverse discontinuous cubic structure (Fd3m)

In our recent work, we reported on the effect of varying temperature and solubilizing tetradecane (TC) on the structural transitions observed in dispersed particles based on the monolinolein (MLO)-water-TC system. At a given temperature, the addition of TC induces a transition of the internal structure from the bicontinuous cubic phase, Pn3m, to the reversed hexagonal, H2, and to the isotropic liquid phase (water-in-oil (W/O) microemulsions). Our present study focuses on the discovery of a Fd3m phase (reversed discontinuous micellar cubic), which is formed in the MLO-water-TC system at a specific TC/MLO weight ratio. It is situated between the H2 and the isotropic liquid phase (W/O microemulsion). Remarkably, it is not found in the absence of TC by increasing the temperature. The Fd3m structure was investigated in detail by means of small-angle X-ray scattering (SAXS), and cryogenic transmission electron microscopy (cryo-TEM). The present work proves that the structural transformation in the dispersed particles from H2 (hexosomes) to the W/O microemulsion system (emulsified microemulsion (EME)) is indirect and it occurs gradually via an emulsified intermediate phase. Specifically, in addition to the nanostructured aqueous dispersions described above, we present new TC-loaded aqueous dispersions with a confined intermediate phase, which is a discontinuous micellar cubic phase of the symmetry Fd3m. We denoted this type of emulsified particles as "micellar cubosomes".