Nanosensing of ATP by fluorescence recovery after surface energy transfer between rhodamine B and curcubit[7]uril-capped gold nanoparticles

The authors describe a method for functionalization of gold nanoparticles (AuNPs) with the supramolecular host molecule, curcubit[7]uril (CB[7]) which can bind rhodamine B (RhB). The fluorescence of RhB is quenched by the AuNPs via surface energy transfer. On addition of ATP, a dimeric RhB-ATP complex is formed and RhB is pushed out of CB[7]. Hence, fluorescence increases by a factor of 8. This fluorescence recovery effect has been utilized to develop a new detection scheme for ATP. The assay, measured at fluorescence excitation and emission wavelengths of 500 nm and 574 nm respectively, works in the 0.5–10 μM concentration range and has a 100 nM detection limit. The method is not interfered by UTP, GTP, CTP, TTP, ascorbic acid and glutathione.

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Graphical abstract Schematic of a method for determination of ATP in the 500 nM to 10 μM concentration range by using fluorescence recovery after surface energy transfer (SET) between rhodamine B (RhB) and gold nanoparticles capped with curcubit[7]uril (CB[7]).

     

Biomimetic oxidation of catechol employing complexes formed in situ with heterocyclic ligands and different copper(II) salts

In the present work, catecholase activity is presented. The complexes were prepared by condensation of the organic ligand pyrazolyl L ₁ –L ₄ and copper(II) ion in situ. The pyrazolyl compounds L ₁ –L ₄ used in this study are: L ₁ is (3,5-dimethyl-pyrazol-1-ylmethyl)-(4-methyl-pyridin-2-yl)-pyrazol-1-ylmethyl-amine; L ₂ is 1-{4-[(3,5-dimethyl-pyrazol-1-ylmethyl)-pyrazol-1-ylmethyl-amino]-phenyl}-ethanone; L ₃ is 1-{4-[(3,5-dimethyl-pyrazol-1-ylmethyl)-[1,2,4]triazol-1-ylmethyl-amino]-phenyl}-ethanone, and L ₄ is 2-[(3,5-dimethyl-pyrazol-1-ylmethyl)-[1,2,4]triazol-1-ylmethyl-amino]-6-methyl-pyrimidin-4-ol, and copper ions salts Cu(II) are (Cu(CH₃COO)₂, CuCl₂, Cu(NO₃)₂ and CuSO₄). In order to determine factors influencing the catecholase activity of these complexes, the effect of ligand nature, ligand concentration, nature of solvent and nature of counter anion has been studied. The best activity of catechol oxidation is given by the combination formed by one equivalent of ligand L ₂ and one equivalent of Cu(CH₃COO)₂ in methanol solvent which is equal to 9.09 µmol L^?1 min^?1. The Michaelis–Menten model is applied for the best combination, to obtain the kinetic parameters, and we proposed the mechanism for oxidation reaction of catecholase.     

Analysis of the Glass-Forming Ability of Fe–Er Alloys,Based on Thermodynamic Modeling

The Fe–Er phase diagram and thermodynamic properties of all its phases are assessed by means of self-consistent analysis. To refine the data on phase equilibria in the Fe–Er system, an investigation is performed in the 10–40 at % range of Er concentrations. The temperature–concentration dependences of the thermodynamic properties of a melt are presented using the model of ideal associated solutions. Thermodynamic parameters of each phase are obtained, and the calculated results are in agreement with available experimental data. The correlation between the thermodynamic properties of liquid Fe–Er alloys and their tendency toward amorphization are studied. It is shown that compositions of amorphous alloys prepared by melt quenching coincide with the ranges of concentration with the predominance of Fe₃Er and FeEr₂ associative groups that have large negative entropies of formation.     

Characterization of different ice habits according to nucleation processes in the electrolyte LiCl · RH2O (6 < R < 9)

The ability to observe different ice nucleation processes in LiCl · RH₂O electrolytes is demonstrated by light scattering experiments. The homogeneous ice nucleation mechanism is analyzed on the basis of Turnbull's theory. This nucleation operates in supercooled water, as deduced from the volumic dependence of the samples on R(5 < R < 9), and is compatible with the definition of the electrolyte as a heterogeneous submicroscopic LiCl·6H₂O medium composed of H₂O and LiCl·6H₂O.     

Generalizations of Pełczyński’s decomposition method for Banach spaces containing a complemented copy of their squares

Suppose that X and Y are Banach spaces isomorphic to complemented subspaces of each other. In 1996, W. T. Gowers solved the Schroeder-Bernstein Problem for Banach spaces by showing that X is not necessarily isomorphic to Y. However, if X ² is complemented in X with supplement A and Y ² is complemented in Y with supplement B, that is,

Electrodeposition of Ge, Si and Si x Ge 1-x from an air- and water-stable ionic liquid

The electrodeposition of Ge, Si and, for the first time, of Si(x)Ge(1-x) from the air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py(1,4)]Tf(2)N) containing GeCl(4) and/or SiCl(4) as precursors is investigated by cyclic voltammetry and high-resolution scanning electron microscopy. GeCl(2) in [Py(1,4)]Tf(2)N is electrochemically prepared in a two-compartment cell to be used as Ge precursor instead of GeCl(4) in order to avoid the chemical attack of Ge(iv) on deposited Ge. Silicon, germanium and Si(x)Ge(1-x) can be deposited reproducibly and easily in this ionic liquid. Interestingly, the Si(x)Ge(1-x) deposit showed a strong colour change (from red to blue) at room temperature during electrodeposition, which is likely to be due to a quantum size effect. The observed colours are indicative of band gaps between at least 1.5 and 3.2 eV. The potential of ionic liquids in Si(x)Ge(1-x) electrodeposition is demonstrated.     

Solvation in pure liquids: what can be learned from the use of pairs of indicators?

The solvation of six solvatochromic probes in a large number of solvents (33-68) was examined at 25 degrees C. The probes employed were the following: 2,6-diphenyl-4-(2,4,6-triphenylpyridinium-1-yl) phenolate (RB); 4-[(E)2-(1-methylpyridinium-4-yl)ethenyl] phenolate, MePM; 1-methylquinolinium-8-olate, QB; 2-bromo-4-[(E)-2-(1-methylpyridinium-4-yl)ethenyl] phenolate, MePMBr, 2,6-dichloro-4-(2,4,6-triphenyl pyridinium-1-yl) phenolate (WB); and 2,6-dibromo-4-[(E)-2-(1-methylpyridinium-4-yl)ethenyl] phenolate, MePMBr(2), respectively. Of these, MePMBr is a novel compound. They can be grouped in three pairs, each with similar pK(a) in water but with different molecular properties, for example, lipophilicity and dipole moment. These pairs are formed by RB and MePM; QB and MePMBr; WB and MePMBr(2), respectively. Theoretical calculations were carried out in order to calculate their physicochemical properties including bond lengths, dihedral angles, dipole moments, and wavelength of absorption of the intramolecular charge-transfer band in four solvents, water, methanol, acetone, and DMSO, respectively. The data calculated were in excellent agreement with available experimental data, for example, bond length and dihedral angles. This gives credence to the use of the calculated properties in explaining the solvatochromic behaviors observed. The dependence of an empirical solvent polarity scale E(T)(probe) in kcal/mol on the physicochemical properties of the solvent (acidity, basicity, and dipolarity/polarizability) and those of the probes (pK(a), and dipole moment) was analyzed by using known multiparameter solvation equations. For each pair of probes, values of E(T)(probe) (for example, E(T)(MePM) versus E(T)(RB)) were found to be linearly correlated with correlation coefficients, r, between 0.9548 and 0.9860. For the mercyanine series, the values of E(T)(probe) also correlated linearly, with (r) of 0.9772 (MePMBr versus MePM) and 0.9919 (MePMBr(2) versus MePM). The response of each pair of probes (of similar pK(a)) to solvent acidity is the same, provided that solute-solvent hydrogen-bonding is not seriously affected by steric crowding (as in case of RB). We show, for the first time, that the response to solvent dipolarity/polarizability is linearly correlated to the dipole moment of the probes. The successive introduction of bromine atoms in MePM (to give MePMBr, then MePMBr(2)) leads to the following linear decrease: pK(a) in water, length of the phenolate oxygen-carbon bond, length of the central ethylenic bond, susceptibility to solvent acidity, and susceptibility to solvent dipolarity/polarizability. Thus studying the solvation of probes whose molecular structures are varied systematically produces a wealth of information on the effect of solute structure on its solvation. The results of solvation of the present probes were employed in order to test the goodness of fit of two independent sets of solvent solvatochromic parameters.     

A new thermal study of the reaction of 6‐azidopyridones with different amines and hydrazines

Reacting of 6‐azidopyridone derivatives 1 with o‐phenylenediamine ( 2a ) in chloroform at room temperature afforded the new azidopyridones 3 . However, its fusion with 2a,b at 100–110°C gave the interesting pyrido[2,3‐b][1,5]diazepines 4a,b . Alternatively, compound 4a could also be obtained by heating azidopyridones 3 at 100–110°C. When compound 1 was allowed to react with hydrazines 7a‐d at room temperature it gave the corresponding azido compounds 8a‐d . Fusion of 1 with phenylhydrazine ( 7d ) at 140–160°C afforded the new aminopyridones 10 . The 6‐azidopyridones 1 could also be converted to the corresponding 6‐alkylaminopyridones 15a‐d by reaction with an excess of alkylamines at room temperature.     

Regioselectivity of the reactions of 4,5‐diphenylimidazole‐2‐thione with 1‐chloro‐2,3‐epoxy‐propane and 1‐bromo‐propene,efficient precursors for imidazo[2,1‐b]thiazine and thiazole. Effect of microwave and solid support

A solid support under microwave (MW) irradiation without solvent allowed the synthesis of the 2,3‐epoxy‐propyl‐thioimidazole 4 , regioselectively, and prohibited its cyclization to give the imidazo[2,1‐b]thiazine 3 from the reaction of 4,5‐diphenylimidazole‐2‐thione ( 1 ) with 1‐chloro‐2,3‐epoxy‐propane ( 2 ). The formation of the latter required basic conditions whereby it became the sole product; the change of the basic catalyst changed the ratio of the two products under both conventional and microwave (MW) conditions. A regioselective allylation of 1 with allyl bromide in presence of triethylamine gave the S‐allyl 8 , while in presence of potassium carbonate led to the S,N‐bis(allylated) derivative 9 . The intramolecular ring closure of 8 in presence of sulfuric acid afforded the imidazothiazole 16 . Protection of the sulfur in 1 and subsequent reaction with allyl bromide gave the N‐allylated derivative and with 2 gave N‐3‐chloro‐prop‐1‐yl derivative that shed light on the preferred route for the formation of 3 and 4 . The reactivity encountered during the alkylation of 1 with 2 has been theoretically investigated by using the AM1 method.     

A pyrazole-based orthogonal ferromagnetically coupled [2 × 2] homoleptic square Cu4 grid: Magnetostructural correlations

The synthesis and structure of a pyrazole-based orthogonal ferromagnetically coupled tetracopper(II) 2 × 2 homoleptic grid complex [Cu₄(PzOAPyz)₄(ClO₄)₂](ClO₄)₂ · 6H₂O (1), formed by the reaction between the ditopic ligand PzOAPyz and Cu(ClO₄)₂ · 6H₂O, are described. The ligand contains terminal pyrazole and pyrazine residues bound to a central flexible diazine subunit (N–N) as well as one potentially bridging alkoxo group. The two adjacent metal centers are linked by an alkoxo oxygen forming essentially a square Cu₄(μ-O₄) cluster. In the Cu₄(μ-O₄) core, out of the four copper centers, two copper centers are penta-coordinated and the remaining two are hexa-coordinated. In each case of hexa-coordination, the sixth position is occupied by one of the oxygen atoms of a coordinated perchlorate ion. Complex 1 has been characterized structurally and magnetically. Although the large Cu–O–Cu bridge angles (137–138°) and short Cu–Cu distances (3.964–3.970 Å) are suitable for the transmission of the expected antiferromagnetic coupling, the square-based Cu₄(μ-O₄) cluster exhibits an intramolecular ferromagnetic exchange (J = 7.47 cm⁻¹) between the metal centers with an S = 2 magnetic ground state associated with the quasi orthogonal arrangement of the magnetic orbitals (d_x2-y2${\text{d}}_{x^2-y^2}$). The exchange pathway parameters have been evaluated from density functional calculations.