Synthesis of anionic core-shell poly(styrene-<Emphasis Type="Italic">co-N</Emphasis>-isopropylacrylamide) colloids by a two-step surfactant-free emulsion polymerization

The aim of the performed work is to produce anionic core-shell poly(styrene-co-N-isopropylacrylamide) colloids with an N-isopropylacrylamide (NIPAM) content in the range from 5 to 30 mol %. Different batches of poly(styrene-co-NIPAM) colloids (poly(ST-co-NIPAM) colloids) are produced with varying NIPAM mol %, and the produced poly(ST-co-NIPAM) colloids are characterized by dynamic light scattering and scanning electron microscopy. Results show that the produced colloids have a core-shell morphology with a poly(styrene) core and a poly(NIPAM) shell. The swelling ratio of the produced poly(ST-co-NIPAM) colloids is similar to the swelling ratio found for similar poly(ST-co-NIPAM) colloids produced by the two-step seeded polymerization process. The text was submitted by the author in English.     

Triazole-linked-thiophene conjugate of calix[4]arene: its selective recognition of Zn2+ and as biomimetic model in supporting the events of the metal detoxification and oxidative stress involving metallothionein

Supramolecular calix[4]arene conjugate (L) has been developed as a sensitive and selective sensor for Zn(2+) in HEPES buffer among the 12 metal ion by using fluorescence, absorption and ESI MS and also by visual fluorescent color. The structural, electronic, and emission properties of the calix[4]arene conjugates L and its zinc complex, [ZnL], have been demonstrated using ab initio density functional theory (DFT) combined with time-dependent density functional theory (TDDFT) calculations. The TDDFT calculations reveal the switch on fluorescence behavior of L is mainly due to the utilization of the lone pair of electrons on imine moiety by the Zn(2+). The resultant fluorescent complex, [ZnL], has been used as a secondary sensing chemo-ensemble for the detection of -SH containing molecules by removing Zn(2+) from [ZnL] and forming {Cys/DTT·Zn} adducts as equivalent to those present in metallothioneins. The displacement followed by the release of the coordinated zinc from its Cys/DTT complex by heavy metal ion (viz. Cd(2+) and Hg(2+)), as in the metal detoxification process or by ROS (such as H(2)O(2)) as in the oxidative stress, has been well demonstrated using the conjugate L through the fluorescence intensity retrieval wherein the fluorescence intensity is the same as that observed with [ZnL], which in turn mimics the zinc sensing element (MTF) in biology.     

A fluorescent di-zinc(II) complex of bis-calix[4]arene conjugate as chemosensing-ensemble for the selective recognition of ATP

A triethylene glycol di-imine locked triazole linked bis-calix[4]arene conjugate L has been synthesised and characterised. Conjugate L exhibits high fluorescence enhancement towards Zn²⁺ among the 13 metal ions studied down to a lower detection limit of ～12 ppb. The absorption and visual colour change experiments differentiated the Zn²⁺ from the other metal ions studied. The isolated zinc complex, [Zn₂L] has been used as a chemo-sensing ensemble for the recognition of anions based on their binding affinities towards Zn²⁺. [Zn₂L] was found to be sensitive and selective towards phosphate-bearing species and in particular to adenosine triphosphate (ATP^2 ? ) among the other 20 anions studied as observed based on the changes occurred in the fluorescence intensity. The selectivity of the ATP^2 ?  has been shown on the basis of the changes observed in the emission and absorption spectral studies. The lowest detectable concentration for ATP^2 ?  with the chemo-sensing ensemble [Zn₂L] is 348 ppb in methanol. The fluorescence quenching by the phosphate-based anions has been modelled by molecular mechanics studies and found that the anions possessing two or more phosphate moieties can only bridge between the two zinc centres, and hence those possessing only one phosphate moiety (H₂PO₄^?  and AMP^2 ? ) are ineffective.     

Redox grafting of diazotated anthraquinone as a means of forming thick conducting organic films

Thick conductive layers containing anthraquinone moieties are covalently immobilized on gold using redox grafting of the diazonium salt of anthraquinone (i.e., 9,10-dioxo-9,10-dihydroanthracene-1-diazonium tetrafluoroborate). This grafting procedure is based on using consecutive voltammetric sweeping and through this exploiting fast electron transfer reactions that are mediated by the anthraquinone redox moieties in the film. The fast film growth, which is followed by infrared reflection absorption spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, ellipsometry, and coverage calculation, results in a mushroom-like structure. In addition to varying the number of sweeps, layer thickness control can easily be exerted through appropriate choice of the switching potential and sweep rate. It is shown that the grafting of the diazonium salt is essentially a diffusion-controlled process but also that desorption of physisorbed material during the sweeping process is essentially for avoiding blocking of the film due to clogging of the electrolyte channels in the film. In general, sweep rates higher than 0.5 V s(-1) are required if thick, porous, and conducting films should be formed.     

Imino-phenolic-pyridyl conjugates of calix[4]arene (L1 and L2) as primary fluorescence switch-on sensors for Zn2+ in solution and in HeLa cells and the recognition of pyrophosphate and ATP by [ZnL2

Pyridyl-based triazole-linked calix[4]arene conjugates, viz. L(1) and L(2), were synthesized and characterized. These two conjugates were shown to be selective and sensitive for Zn(2+) among the 12 metal ions studied in HEPES buffer medium by fluorescence, absorption, and visual color change with the detection limit of ~31 and ~112 ppb, respectively, by L(1) and L(2). Moreover, the utility of the conjugates L(1) and L(2) in showing the zinc recognition in live cells has also been demonstrated using HeLa cells as monitored by fluorescence imaging. The zinc complexes of L(1) and L(2) were isolated, and the structure of [ZnL(1)] has been established by single-crystal XRD and that of [ZnL(2)] by DFT calculations. TDDFT calculations were performed in order to demonstrate the electronic properties of receptors and their zinc complexes. The isolated zinc complexes, viz. [ZnL(1)] and [ZnL(2)], have been used as molecular tools for the recognition of anions on the basis of their binding affinities toward Zn(2+). [ZnL(2)] was found to be sensitive and selective toward phosphate-bearing ions and molecules and in particular to pyrophosphate (PPi) and ATP among the other 18 anions studied; however, [ZnL(1)] was not sensitive toward any of the anions studied. The selectivity has been shown on the basis of the changes observed in the emission and absorption spectral studies through the removal of Zn(2+) from [ZnL(2)] by PPi. Thus, [ZnL(2)] has been shown to detect PPi up to 278 ± 10 ppb at pH 7.4 in aqueous methanolic (1/2 v/v) HEPES buffer.     

Lower rim 1,3-di{4-antipyrine}amide conjugate of calix[4]arene: synthesis, characterization, and selective recognition of Hg2+ and its sensitivity toward pyrimidine bases

The structurally characterized lower rim 1,3-di{4-antipyrine}amide conjugate of calix[4]arene (L) exhibits high selectivity toward Hg(2+) among other biologically important metal ions, viz., Na(+), K(+), Ca(2+), Mg(2+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), and Ag(+) as studied by fluorescence, absorption, and ESI MS. L acts as a sensor for Hg(2+) by switch-off fluorescence and exhibits a lowest detectable concentration of 1.87 ± 0.1 ppm. The complex formed between L and Hg(2+) is found to be 1:1 on the basis of absorption and fluorescence titrations and was confirmed by ESI MS. The coordination features of the mercury complex of L were derived on the basis of DFT computations and found that the Hg(2+) is bound through an N(2)O(2) extending from both the arms to result in a distorted octahedral geometry with two vacant sites. The nanostructural features such as shape and size obtained using AFM and TEM distinguishes L from its Hg(2+) complex and were different from those of the simple mercuric perchlorate. L is also suited to sense pyrimidine bases by fluorescence quenching with a minimum detection limit of 1.15 ± 0.1 ppm in the case of cytosine. The nature of interaction of pyrimidine bases with L has been further studied by DFT computational calculations and found to have interactions through a hydrogen bonding and NH-π interaction between the host and the guest.     

Energy dependence of multiplicity in proton-nucleus collisions and models of multiparticle production

This is a continuation of our earlier investigation (Gurtuet al 1974Phys. Lett. 50 B 391) on multiparticle production in proton-nucleus collisions based on an exposure of emulsion stack to 200 GeV/c beam at the NAL. It is found that the ratioR _em = 〈n _s〉/〈n _ch〉, where 〈n _ch〉 is the charged particle multiplicity in pp-collisions, increases slowly from about 1 at 10 GeV/c to 1·6 at 68 GeV/c and attains a constant value of 1·71 ± 0·04 in the region 200 to 8000 GeV/c. Furthermore,R _em = 1·71 implies an effectiveA-dependence ofR _A =A ^0.18,i.e., a very weak dependence. Predictions ofR _em on various models are discussed and compared with the emulsion data. Data seem to favour models of hadron-nucleon collisions in which production of particles takes place through adouble step mechanism,e.g., diffractive excitation, hydrodynamical and energy flux cascade as opposed to models which envisage instantaneous production.     

Optimization of solid phase extraction clean up and validation of quantitative determination of corticosteroids in urine by liquid chromatography-tandem mass spectrometry

A solid phase extraction (SPE) method for extraction and clean up of 9 synthetic corticosteroids was optimized for quantification by reversed-phase high-performance liquid chromatography/negative electrospray ionisation mass spectrometry. Clean up was accomplished using a mixed mode polymeric strong anion exchange SPE column. The final method was validated according to EU regulations for determination of residues of veterinarian drugs in products of animal origin. Initial results showed a large difference in ion suppression between samples of porcine and bovine urine. The aim of optimisation was to design a procedure that minimised this difference while using a single SPE procedure and a fast HPLC method that enabled sufficient separation of the epimers beta- and dexamethasone. To include conjugated corticosteroids in the analysis, the sample was hydrolysed with Helix Pomatia beta-glucuronidase/aryl sulfatase. For the final method, which included fluocinolone acetonid, triamcinolone acetonid, beclomethasone, flumethasone, dexamethasone, betamethasone, 6alpha-methylprednisolone, prednisone and prednisolone, a quantification based on spiked samples carried through the entire analytical procedure was used. For quantification of triamcinolone acetonid an internal standard (triamcinolone acetonid-D6) was used. Relative average recoveries from 96 to 103% were found, except for beclomethasone (113%). Absolute average recoveries were 81-99%. Quantification limits (decision limits, CCalpha) were demonstrated to be not higher than 1 microg L(-1) (3 microg L(-1) for prednisone and prednisolone). The internal reproducibility, determined by triplicates from spiking at three different levels in six analytical series was 7-19% (at 2-4 microg L(-1)) except for prednisone and prednisolone (26-27% at 3-6 microg L(-1)).     

Radial oscillations of neutron stars in strong magnetic fields

The eigen frequencies of radial pulsations of neutron stars are calculated in a strong magnetic field. At low densities we use the magnetic BPS equation of state (EOS) similar to that obtained by Lai and Shapiro while at high densities the EOS obtained from the relativistic nuclear mean field theory is taken and extended to include strong magnetic field. It is found that magnetized neutron stars support higher maximum mass whereas the effect of magnetic field on radial stability for observed neutron star masses is minimal.