Showing papers in "Analytical Sciences in 2008"
TL;DR: The obtained rutile-form titania exhibited higher selectivity in phosphopeptide enrichment than commercial titania, even in the absence of a competitive chelating reagent for non-phosphopeptides.
Abstract: We have developed an on-line automated system for phosphoproteome analysis using titania-based phosphopeptide enrichment followed by nanoLC-MS/MS. Titania beads were prepared by calcination of commercial chromatographic titania beads at 800°C to convert the crystalline structure. The obtained rutile-form titania exhibited higher selectivity in phosphopeptide enrichment than commercial titania, even in the absence of a competitive chelating reagent for non-phosphopeptides. For phosphoproteome analysis of human cervical cancer HeLa cells, tryptic digests of the cell extracts were directly injected into this on-line system, and 696 non-redundant phosphopeptides with 671 unambiguously determined phosphorylation sites, derived from 512 phosphoproteins, were successfully identified. This is the first successful application of an on-line automated phosphoproteome analysis system to complex biological samples.
117 citations
TL;DR: This paper overviews cell patterning techniques based on chemically modified substrates with different degrees of cell adhesiveness, and introduces a dynamic substrate based on a caged compound, where a light-driven alteration of cellAdhesiveness and the analysis of a single cell's motility are accomplished.
Abstract: Cell micropatterning is an important technique for a wide range of applications, such as tissue engineering, cell-based drug screening, and fundamental cell biology studies. This paper overviews cell patterning techniques based on chemically modified substrates with different degrees of cell adhesiveness. In particular, the focus is on dynamic substrates that change their cell adhesiveness in response to external stimuli, such as heat, voltage, and light. Such substrates allow researchers to achieve an in situ alteration of patterns of cell adhesiveness, which is useful for co-culturing multiple cell types and analyzing dynamic cellular activities. As an example of dynamic substrates, we introduce a dynamic substrate based on a caged compound, where we accomplished a light-driven alteration of cell adhesiveness and the analysis of a single cell's motility.
112 citations
TL;DR: Thermal decomposition behaviors of a series of imidazolium-type ionic liquid samples were studied by pyrolysis-gas chromatography at 550 degrees C using various detectors, finding that no boron-containing products were found even from the samples with BF(4) anion, whereas minor but clear peaks of phosphorous- containing products were observed in the pyrograms of the sample with PF(6) anions.
Abstract: Thermal decomposition behaviors of a series of imidazolium-type ionic liquid samples were studied by pyrolysis-gas chromatography at 550°C using various detectors. As for the imidazolium halides, haloalkanes and 1-alkylimidazoles corresponding to the alkyl substituents were mainly formed through the nucleophilic attacks of halide ions to the alkyl groups followed by C-N bond cleavage, along with a minor amount of alkenes. Meanwhile, in the case of the ionic liquids with BF4, PF6 and CF3SO3 anions, corresponding alkenes were predominantly produced along with 1-alkylimidazoles rather than haloalkanes. No boron-containing products were found even from the samples with BF4 anion, whereas minor but clear peaks of phosphorous-containing products were observed in the pyrograms of the samples with PF6 anions. As for the samples with longer alkyl group, the pyrolyzates reflecting the C-C bond scissions in the alkyl groups were also formed to some extent. Meanwhile, imidazole rings did not decompose under the experimental conditions at around 550°C.
112 citations
TL;DR: This method has been successfully applied to estimating of creatinine and uric acid in human urine and provides a simple, rapid separation and sensitive detection for the species of interest in 10 min with UV detection at 205 nm.
Abstract: An environmentally friendly reversed-phase HPLC method for simultaneous determination of creatinine and uric acid in human urine samples has been developed. Human urine samples were pretreated by dilution, protein precipitation, centrifugation and filtration, followed by HPLC separations using a reversed-phase C(18) column with an aqueous mobile phase of phosphate buffer. The retention loss of a C(18) column when using the highly aqueous mobile phases was avoided by employing a gradient elution using a small volume (<0.23 mL) of acetonitrile and phosphate buffer at pH 4.75. This developed method provides a simple, rapid separation and sensitive detection for the species of interest in 10 min with UV detection at 205 nm. Quantitation was carried out by relating the peak areas of the identified compounds to that of hypoxanthine as an internal standard. The detection limits for creatinine and uric acid were 0.045 and 0.062 microg mL(-1), respectively. The recoveries of the standards added to urine samples were 87.3 - 102.2% for creatinine and 97.3 - 108.6% for uric acid, and the relative standard deviation for both analytes was less than 1.0%. This method has been successfully applied to estimating of creatinine and uric acid in human urine.
102 citations
TL;DR: Recent progress in analytical terahertz (THz) spectroscopy is reviewed with illustrative examples showing that it is an effective method for detecting and identifying intermolecular interactions in chemical compounds, such as hydrogen bonds.
Abstract: Recent progress in analytical terahertz (THz) spectroscopy is reviewed with illustrative examples showing that it is an effective method for detecting and identifying intermolecular interactions in chemical compounds, such as hydrogen bonds. The unique and characteristic properties of THz waves, their significance to both science and industry, and the bases of one of the successful fields of analytical THz spectroscopy, namely THz time-domain spectroscopy and THz imaging for chemical analysis, are described. Preliminary quantitative studies are presented to show the potential of THz spectroscopy for the detection and identification of intermolecular hydrogen bonds in unknown mixture samples. The selective detection of intramolecular hydrogen bonds and the detection of intramolecular interactions in ice are also introduced. Some brief remarks are provided on future developments, the main issues, and the prospects for analytical THz spectroscopy.
78 citations
TL;DR: Water-soluble near-infrared fluorescent labeling probes, named KSQ-3 and -4, which are based on a squaraine backbone, exhibited perfect water solubility and significant fluorescence emission at the NIR region in the presence of bovine serum albumin.
Abstract: Water-soluble near-infrared (NIR) fluorescent labeling probes, named KSQ-3 and -4, which are based on a squaraine backbone, were synthesized and applied to biological labeling. The presented results demonstrate that the large, planar and hydrophobic squaraine dye becomes fully soluble in aqueous solution by the introduction of several sulfo group terminated alkyl substituents. Especially KSQ-4, which is substituted with four sulfo groups, exhibited perfect water solubility and significant fluorescence emission at the NIR region (817 nm) in the presence of bovine serum albumin (BSA). BSA was covalently labeled with KSQ-4, and the conjugate showed a strong absorption peak at 787 nm, which indicates compatibility with commercially available NIR laser diodes used for exciting the fluorophore. Furthermore, strong fluorescence emission was observed at 812 nm (phi = 0.08).
75 citations
TL;DR: The results showed that metal(II) ions are all six-coordinated with three TFSA(-) ions, and it was concluded that the conformational equilibrium in the coordination sphere is strongly temperature-sensitive.
Abstract: Solvation structures of manganese(II), cobalt(II), nickel(II) and zinc(II) ions in 1-ethyl-3-methylimidazolium bis(trifluoro-methanesulfonyl) amide (EMI(+)TFSA(-)) have been studied by UV-Vis, FT-IR and FT-Raman spectra. The ionic liquid involves TFSA(-) conformers with C(1) (cis) and C(2) (trans) symmetries, and both conformers coexist in equilibrium in the liquid state. The results showed that these metal(II) ions are all six-coordinated with three TFSA(-) ions, i.e., TFSA(-) ligates as a bidentate O-donor in the ionic liquid. Although the metal ion strongly prefers the C(1) conformer in crystals, the metal ion coordinates both the C(1) and C(2) conformers in the liquid state, and the conformational equilibrium in the bulk only slightly shifts to the C(1) conformer in the coordination sphere. We concluded that the conformational equilibrium in the coordination sphere is strongly temperature-sensitive.
66 citations
TL;DR: The results of DPV using the 2,2'-[3,6-dioxa-1,8-octanediylbis(nitriloethylidyne)]-bis-hydroquinone-modified electrode were applied in a highly sensitive determination of AA in drug samples.
Abstract: Electrocatalytic oxidation of ascorbic acid (AA) at a carbon paste electrode, chemically modified 2,2′-[3,6-dioxa-1,8-octanediylbis(nitriloethylidyne)]-bis-hydroquinone, was thoroughly investigated. The results of cyclic voltammetry, double potential-step chronoamperometry, linear sweep voltammetry and differential pulse voltammetry (DPV) studies were used for the prediction of the mechanism of electrochemical oxidation of AA mediated with 2,2′-[3,6-dioxa-1,8-octanediylbis(nitriloethylidyne)]-bis-hydroquinone at the surface of the modified electrode. The diffusion coefficient (D = 2.45 × 10-5 cm2 s-1) and the kinetic parameters such as the electron transfer coefficient (α = 0.34) were also determined. The results of DPV using the 2,2′-[3,6-dioxa-1,8-octanediylbis(nitriloethylidyne)]-bis-hydroquinone-modified electrode were applied in a highly sensitive determination of AA in drug samples. A linear range of 3.0 × 10-6 - 1.2 × 10-4 M and the detection limit (3σ) 3.8 × 10-7 M were obtained for DPV determination of AA in buffered pH 7.00 solutions (0.1 M phosphate buffer).
63 citations
TL;DR: The direct molecular analysis of a live single cell viewed under a video-microscope has been developed and it is shown that this method is direct and quick to identify the molecules of a cell with simultaneous observation by a Video Microscope.
Abstract: The direct molecular analysis of a live single cell viewed under a video-microscope has been developed. The cell contents are sucked into a nano-electrospray tip, and hundreds of peaks of ionic compounds of low molecular weight are detected by nano-ESI Q-TOF mass spectrometry (MS). Cell-specific MS peaks in a single mouse-embryonic fibroblasts cell are extracted by a t-test, and one of the peaks is proceeded to MS/MS analysis for molecular identification. This method is direct and quick to identify the molecules of a cell with simultaneous observation by a video-microscope.
60 citations
TL;DR: The data obtained here clearly demonstrate that the fs-laser ablation system has the potential to become a significant tool for in-situ elemental and isotopic analysis of geochemical samples including heavy minerals and metallic materials.
Abstract: A laser ablation-inductively coupled plasma-mass spectrometric (LA-ICPMS) technique utilizing a titanium-sapphire (TiS) femtosecond laser (fs-laser) has been developed for elemental and isotopic analysis. The signal intensity profile, depth of the ablation pit and level of elemental fractionation were investigated in order to evaluate the analytical capability of the present fs-laser ablation-ICPMS technique. The signal intensity profile of 57Fe, obtained from iron sulfide (FeS2), demonstrated that the resulting signal intensity of 57Fe achieved by the fs-laser ablation was almost 4-times higher than that obtained by ArF excimer laser ablation under a similar energy fluence (5 J/cm2). In fs-laser ablation, there is no significant difference in a depth of the ablation pit between glass and zircon material, while in ArF laser ablation, the resulting crater depth on the zircon crystal was almost half the level than that obtained for glass material. Both the thermal-induced and particle size-related elemental fractionations, which have been thought to be main sources of analytical error in the LA-ICPMS analysis, were measured on a Harvard 91500 zircon crystal. The resulting fractionation indexes on the 206Pb/238U (fPb/U) and 238U/232Th (fU/Th) ratios obtained by the present fs-laser ablation system were significantly smaller than those obtained by a conventional ArF excimer laser ablation system, demonstrative of smaller elemental fractionation. Using the present fs-laser ablation technique, the time profile of the signal intensity of 56Fe and the isotopic ratios (57Fe/54Fe and 56Fe/54Fe) have been measured on a natural pyrite (FeS2) sample. Repeatability in signal intensity of 56Fe achieved by the fs-laser ablation system was significantly better than that obtained by ArF excimer laser ablation. Moreover, the resulting precision in 57Fe/54Fe and 56Fe/54Fe ratio measurements could be improved by the fs-laser ablation system. The data obtained here clearly demonstrate that, even with the fundamental wavelength (NIR operating at 780 nm), the fs-laser ablation system has the potential to become a significant tool for in-situ elemental and isotopic analysis of geochemical samples including heavy minerals and metallic materials.
59 citations
TL;DR: The proposed SIA-SWASV method was applied to the determination of Pb(II), Cd(II) and Zn( II) in water samples with satisfactory results.
Abstract: A sequential injection-square-wave anodic stripping voltammetry (SIA-SWASV) is proposed for the simultaneous determination of Pb(II), Cd(II) and Zn(II), employing an in situ plated bismuth film screen-printed carbon electrode (Bi-SPCE) as a working electrode and hydrochloric acid as a supporting electrolyte. Bi(III) and analyte metal ions were on-line deposited onto a SPCE at -1.4 V vs. Ag/AgCl for 180 s. At a stopped flow, a square-wave voltammogram was recorded from -1.3 to 0 V vs. Ag/AgCl. The experimental conditions were optimized. Under the optimum conditions, the linear ranges were 0 - 70 mu g L-1 for Pb(II) and Cd(II), and 75 - 200 mu g L-1 for Zn(II). The limits of detection (S/N = 3) were obtained at concentrations as low as 0.89 mu g L-1 for Pb(II) and 0.69 mu g L-1 for Cd(II) for a 180-s deposition time. The proposed method was applied to the determination of Pb(II), Cd(II) and Zn(II) in water samples with satisfactory results.
TL;DR: The results support that the Li(I) species in DEMETFSA solutions exist as [Li(TFSA)(2)](-) and the Li (I) oligomer species in the low and high concentration regions of LiTFSA, respectively.
Abstract: The solvation structure of the Li(I) species in N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethane-sulfonyl) amide (DEMETFSA) was studied by measuring the Raman and multinuclear NMR spectra of DEMETFSA solutions containing LiTFSA of various concentrations (0.12 - 1.92 mol kg-1, [TFSA-]/[Li(I)] = 20.0 - 2.22). It was found from Raman spectra that an intense band due to the free TFSA- anion at around 741 cm-1 becomes weak, and a new band appears at around 747 cm-1 with an increase in the concentrations of LiTFSA, and that the pseudoisosbestic point is observed at around 744 cm-1 in the range of [TFSA-]/[Li(I)] = 20.0 - 5.00. From analyses of these Raman bands, the number of TFSA- anions bound to the Li+ ion was evaluated to be 1.85 ± 0.08, and hence, the Li(I) in DEMETFSA solutions was proposed to exist as [Li(TFSA)2]- in the range of [TFSA-]/[Li(I)] = 20.0 - 5.00. Furthermore, in the range of [TFSA-]/[Li(I)] = 2.86 - 2.22, the band observed at around 747 cm-1 became more strong, and the pseudoisosbestic point disappeared. From these phenomena, it seems that the Li(I) oligomer species are formed in the higher concentration region of LiTFSA. The 19F NMR signal of the TFSA- anion observed at 42.31 ppm in neat DEMETFSA was found to shift to a higher field linearly with an increase in the concentrations of LiTFSA ([LiTFSA] = 0.00 - 0.99 mol kg-1, [TFSA-]/[Li+] = 20.0 - 3.33), while in a higher concentration range ([LiTFSA] ≥ 1.26 mol kg-1, [TFSA-]/[Li+] ≤ 2.86), a slight deviation from linearity was observed. On the other hand, the 7Li NMR signal did not show an appreciable shift with increasing LiTFSA concentrations. These results support that the Li(I) species in DEMETFSA solutions exist as [Li(TFSA)2]- and the Li(I) oligomer species in the low and high concentration regions of LiTFSA, respectively.
TL;DR: In the ionic liquid chelate extraction system, selection of a suitable ionic Liquid as extraction phase seems to be an important factor for enhancement of extraction selectivity.
Abstract: The extraction behavior of several divalent metal cations (M(2+)) in ionic liquid chelate extraction systems was investigated using several 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquids ([Rmim][Tf(2)N]) as extraction solvent and thenoyltrifluoroacetone (Htta) as extractant. The behavior was compared with that using less hydrophobic 1-alkyl-3-methylimidazolium hexafluorophosphates ([Rmim][PF(6)]). The extracted species in the [Rmim][Tf(2)N] systems were neutral M(tta)(2) for M = Cu and anionic M(tta)(3)(-) for M = Mn, Co, Ni, Zn and Cd. Conversion of ionic liquid anion from PF(6)(-) to more hydrophobic Tf(2)N(-) resulted in changing the species extracted for Ni(2+) from hydrated neutral complex to hydrophobic anionic one. Furthermore, the extractability for these metals was governed by the hydrophobicity of ionic liquid ions. Thus, in the ionic liquid chelate extraction system, selection of a suitable ionic liquid as extraction phase seems to be an important factor for enhancement of extraction selectivity.
TL;DR: It is shown that phosphonium-type ionic liquids (ILs) can be used for preparation of novel solid-phase extractants and the possibility of retaining ligands on the solid phases by means of ILs to prepare the complexing solid- phase extractants has been demonstrated.
Abstract: That phosphonium-type ionic liquids (ILs) can be used for preparation of novel solid-phase extractants has been shown. The conditions of IL immobilization on the different matrices (polyacrilonitrile, Amberlite XAD-7, hyper cross-linked polystyrene, and multi-walled carbon nanotubes) were determined. The solid-phase extraction of Pt(IV) from 1-2 M HCl and Pu(IV) from 3 M HNO(3) has been investigated. The possibility of retaining ligands on the solid phases by means of ILs to prepare the complexing solid-phase extractants has been demonstrated.
TL;DR: Three glutamic acid-binding aptamers from a modified DNA pool containing arginine residues using the method of systematic evolution of ligands by exponential enrichment showed affinity and specificity for the target by surface plasmon resonance (SPR) measurements.
Abstract: We have screened glutamic acid-binding aptamers from a modified DNA pool containing arginine residues using the method of systematic evolution of ligands by exponential enrichment (SELEX). Thirty-one modified DNA molecules were obtained from the enriched pool after the 17th round of selection, and their binding affinities for the target were evaluated by binding assays using affinity gels. Three modified DNA molecules having higher affinity were sequenced and we determined their affinity and specificity for the target by surface plasmon resonance (SPR) measurements. The SPR studies indicated that two of these three aptamers distinguished the dicarboxylic acid moiety of the D-isomer from that of the L-isomer; however, the third aptamer did not show enantioselectivity.
TL;DR: The apparent pK(s) value was determined in EAN-water mixtures of various solvent compositions, implying that H(3)O(+) is a stronger acid than HNO( 3) in an EAN solution, unlike water.
Abstract: Ethylammonium nitrate (EAN) is composed of C(2)H(5)NH(3)(+) and NO(3)(-) ions, which behave as an acid and a base, respectively. The ionic liquid thus involves small amounts of C(2)H(5)NH(2) and HNO(3) molecules owing to proton transfer from C(2)H(5)NH(3)(+) to NO(3)(-). The equilibrium constant K(s) (= [C(2)H(5)NH(2)][HNO(3)]), which corresponds to the autoprotolysis constant of water, was obtained to be ca. 10(-10) mol(2) dm(-6) by potentiometry using an ion-selective field-effect transistor and hydrogen electrodes at 298 K. The value indicates that C(2)H(5)NH(2) and HNO(3) molecules of ca. 10(-5) mol dm(-3) are involved in neat EAN. On the other hand, in an EAN-water mixture, a water molecule behaves as a base. The apparent pK(s) value was determined in EAN-water mixtures of various solvent compositions. Interestingly, the pK(s) value is remained at 10.5 in mixtures over the range of an EAN mole fraction of 0.05-0.9. The value is close to the pK(a) of C(2)H(5)NH(2), or the acid-dissociation constant of C(2)H(5)NH(3)(+), in aqueous solution. This implies that the reaction C(2)H(5)NH(3)(+) + H(2)O --> C(2)H(5)NH(2) + H(3)O(+) is responsible for the pK(s) over a wide range of solvent composition. The pK(s) value in neat EAN is thus slightly smaller than that in the mixtures, implying that H(3)O(+) is a stronger acid than HNO(3) in an EAN solution, unlike water.
TL;DR: Air samples collected from 45 to 20 degrees N in the Far East showed a slight decrease of the 3He/4He ratio with latitude, which may not preclude the possibility that the anthropogenic release of crustal 4He is significant in the high-latitude region of the northern hemisphere.
Abstract: We have developed an analytical system to measure atmospheric 3He/4He ratios precisely by using a static vacuum operation mass spectrometer and an ultrahigh-vacuum purification line. After purification of the sample, helium was introduced into the mass spectrometer. Ion beams of 3He and 4He were measured at the same time by a double collector system. A resolving power of about 700 at the 5% level of the peak height was attained for the complete separation of 3He ions from those of HD and H3. Repeated analysis of a sample calibrated against a standard showed a precision of about 0.2% error margin (2σ). This system has been applied to evaluating the 3He/4He ratio of He Standard of Japan (HESJ), and for the assessment of the atmospheric variation of latitude. The observed 3He/4He ratio of HESJ, 20.405 ± 0.040Rair (2σ) agrees well with the value of 20.408 ± 0.044Rair by Lupton and Evans, but is smaller than the recommended value of 20.63 ± 0.10Rair in a literature. Air samples collected from 45 to 20°N in the Far East showed a slight decrease of the 3He/4He ratio with latitude. Even though the variation is attributable to an experimental artifact, it may not preclude the possibility that the anthropogenic release of crustal 4He is significant in the high-latitude region of the northern hemisphere.
TL;DR: The behavior of oxidoreductases in the presence of ILs, the mechanisms involved in this association and the immobilization of oxidationases in composite materials with IL are discussed.
Abstract: Due to their unique characteristics ionic liquids (ILs) have been extensively used as solvents in enzymatic procedures, proving to be advantageous alternatives to conventional organic solvents. The studies of enzyme behavior in ILs have increased exponentially in the last years and oxidoreductases particularly have recently started to be studied. The association of oxidoreductases with IL is very promising due to the large field of application of these enzymes. The materials are very interesting not only from the analytical point of view but also in the biocatalytic perspective. In this review, we discuss the behavior of oxidoreductases in the presence of ILs, the mechanisms involved in this association and the immobilization of oxidoreductases in composite materials with IL. The performance of proteins with peroxidase activity in ILs is also reviewed. Future trends and perspectives related with the development of biocatalytic studies involving oxidoreductases and ILs are also considered.
TL;DR: The peak potentials shift in CV, hyperchromism in UV absorption titration, an increase in the viscosity of DNA and the results of the effect of ionic strength on the binding constant strongly support the intercalation of PF into the DNA double helix.
Abstract: The interaction of protonated ferrocene (PF) with chicken blood DNA (CB-DNA) has been investigated in vitro by cyclic voltammetry (CV) and UV-Vis spectroscopy as well as viscosity measurements under stomach pH and body temperature. The peak potentials shift in CV, hyperchromism in UV absorption titration, an increase in the viscosity of DNA and the results of the effect of ionic strength on the binding constant strongly support the intercalation of PF into the DNA double helix. The diffusion coefficients of PF in the presence and absence of DNA were 9.54 × 10-11 and 1.34 × 10-10 m2/s, respectively. The binding constant of the PF-DNA complex and the number of binding sites on a DNA molecule were calculated as being 3.07 × 102 M-1 and 2.96, with the help of the Scatchard equation. An expression by Carter et al. was used for determining the binding site size (0.17 bp). The binding constant was also determined by UV absorption titration.
TL;DR: In this article, a novel electrochemical DNA-based biosensor for the detection of deep DNA damage was designed employing the bionanocomposite layer of multiwalled carbon nanotubes (MWNT) in chitosan (CHIT) deposited on a screen printed carbon electrode (SPCE).
Abstract: A novel electrochemical DNA-based biosensor for the detection of deep DNA damage was designed employing the bionanocomposite layer of multiwalled carbon nanotubes (MWNT) in chitosan (CHIT) deposited on a screen printed carbon electrode (SPCE). The biocomponent represented by double-stranded (ds) herring sperm DNA was immobilized on this composite using layer-by-layer coverage to form a robust film. Individual and complex electrode modifiers are characterized by a differential pulse voltammetry (DPV) with the DNA redox marker [Co(phen)3]3+, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) with [Fe(CN)6]3- as a redox probe in a phosphate buffer solution (PBS). A good correlation between the CV and EIS parameters has been found, thus confirming a strong effect of MWNT on the enhancement of the electroconductivity of the electrode surface and that of CHIT on the MWNT distribution at the electrode surface. Differences between the CV and EIS signals of the electrodes without and with DNA are used to detect deep damage to DNA, advantageously using simple working procedures in the same experiment.
TL;DR: The data obtained here clearly demonstrate that the Ca isotopic ratio has a potential to become a new tool for evaluating changes in dietary consumption, or Ca metabolism of animals.
Abstract: The biological processing of Ca produces significant stable isotope fractionation. The level of isotopic fractionation can provide key information about the variation in dietary consumption or Ca metabolism. To investigate this, we measured the 43Ca/42Ca and 44Ca/42Ca ratios for bone and blood plasma samples collected from mice of various ages using multiple collector-ICP-mass spectrometry (MC-ICP-MS). The 44Ca/42Ca ratio in bones was significantly (0.44 - 0.84‰) lower than the corresponding ratios in the diet, suggesting that Ca was isotopically fractionated during Ca metabolism for bone formation. The resulting 44Ca/42Ca ratios for blood plasma showed almost identical, or slightly higher, values (0.03 -0.2‰) than found in a corresponding diet. This indicates that a significant amount of Ca in the blood plasma was from dietary sources. Unlike that discovered for Fe, there were no significant differences in the measured 44Ca/42Ca ratios between female and male specimens (for either bone or blood plasma samples). Similarity, the 44Ca/42Ca ratios suggests that there were no significant differences in Ca dietary consumption or Ca metabolism between female and male specimens. In contrast, the 44Ca/42Ca ratios of blood plasma from mother mice during the lactation period were significantly higher than those for all other adult specimens. This suggests that Ca supplied to infants through lactation was isotopically lighter, and the preferential supply of isotopically lighter Ca resulted in isotopically heavier Ca in blood plasma of mother mice during the lactation period. The data obtained here clearly demonstrate that the Ca isotopic ratio has a potential to become a new tool for evaluating changes in dietary consumption, or Ca metabolism of animals.
TL;DR: The present paper reports on the application of modified multiwalled carbon nanotubes (MMWCNTs) as a new, easily prepared and stable solid sorbent for the preconcentration of trace Co(II) in aqueous solution.
Abstract: The present paper reports on the application of modified multiwalled carbon nanotubes (MMWCNTs) as a new, easily prepared and stable solid sorbent for the preconcentration of trace Co(II) in aqueous solution. Multiwalled carbon nanotubes (MWCNTs) were oxidized with concentrated HNO(3) and modified with 1-(2-pyridylazo)-2-naphtol (PAN), and were then used as a solid phase for the preconcentration of Co(II). Factors influencing the sorption and desorption of Co(II) were investigated. Elution was carried out with 0.5 mol L(-1) HNO(3). The amount of eluted Co(II) was measured using flame atomic absorption spectrometry. The effects of the experimental parameters, including the sample pH, sample flow rate, eluent flow rate and eluent concentration, were investigated. The effect of coexisting ions showed no interference from most ions tested. The proposed method permitted a large enrichment factor (about 300). The precision of the method was 1.63% (for eight replicate determination of 0.5 microg mL(-1) of Co(II)) and the limit of detection was 0.55 ng mL(-1). The method was applied to the determination of Co(II) in water, biological and standard samples.
TL;DR: The electrochemical properties of chloramphenicol at a boron-doped diamond thin-film (BDD) electrode were studied using cyclic voltammetry and the method has been successfully applied to the determination of chlorampshenicol in sterile eye drops and milk sample by the standard addition method.
Abstract: The electrochemical properties of chloramphenicol at a boron-doped diamond thin-film (BDD) electrode were studied using cyclic voltammetry. The highest current response of chloramphenicol was obtained with phosphate buffer, pH 6 (0.1 M) in 1% ethanol. The relationship between the concentration of chloramphenicol and the current response was linear over the range of 0.1 - 10 mM (R-2 = 0.9990). The amount of chloramphenicol was analyzed by flow-injection analysis. A thin-layer flow cell equipped with a BDD electrode was used as an amperometric detector, and experiments were carried out at -0.7 V (vs. Ag/AgCl). The linear relationship between the current response and the concentration of chloramphenicol in the range of 0.1 - 50 mu M (R-2 = 0.9948) and the limit of detection of 0.03 mu M (S/N = 3) were obtained. This method has been successfully applied to the determination of chloramphenicol in sterile eye drops and milk sample by the standard addition method. The average recoveries of chloramphenicol in eye drops were 98.0%, and the average recoveries of chloramphenicol from spiked milk were 93.9 - 103%.
TL;DR: The solubility of an ionic liquid in water and the electrochemical properties at the interface between the two phases are intimately related with each other.
Abstract: Liquid-liquid two-phase systems formed by a hydrophobic ionic liquid and water find several useful ways of application in analytical chemistry. One of the most important properties of such two-phase systems is the mutual solubility of the IL and water. Recent advancements on this subject have been reviewed. The solubility of ionic liquids in water is related to the standard Gibbs energies of the transfer of ions constituting the ionic liquid from the ionic liquid phase to water. Although this single ionic property cannot be measured thermodynamically and also varies from one ionic liquid to another, the standard Gibbs energy of the ion transfer from a polar aprotic solvent, such as nitrobenzene and 1,2-dichloroethane, to water is a convenient measure for it. The solubility of an ionic liquid in water and the electrochemical properties at the interface between the two phases are intimately related with each other.
TL;DR: A sensitive spectroscopic assay based on surface-enhanced Raman spectroscopy (SERS) using gold nanoparticles as substrates was developed for the rapid detection protein-protein interactions and highly selective recognition of IgG down to 1 ng/ml in solution has been demonstrated.
Abstract: In the present work, a sensitive spectroscopic assay based on surface-enhanced Raman spectroscopy (SERS) using gold nanoparticles as substrates was developed for the rapid detection protein-protein interactions. Detection is achieved by specific binding biotin-modification antibodies with protein-stabilized 30 nm gold nanoparticles, followed by the attachment of avidin-modification Raman-active dyes. As a proof-of-principle experiment, a well-known biomolecular recognition system, IgG with protein A, was chosen to establish this new spectroscopic assay. Highly selective recognition of IgG down to 1 ng/ml in solution has been demonstrated.
TL;DR: The probe exhibited a higher fluorescence response to *OH over other reactive oxygen species, such as hydrogen peroxide, nitric oxide, peroxynitrite, alkylperoxyl radical, and hypochlorite.
Abstract: Coumarin-3-carboxylic acid (CCA) was purchased from Aldrich. 7-Hydroxycoumarin-3-carboxylic acid N-succinimidyl ester (7OH-SECCA) was purchased from Fluka. 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC), 1-hydroxy-2oxo-(N-methyl-3-aminopropyl)-3-methyl-1-triazene (NOC7) and peroxynitrite solution were purchased from Dojindo Laboratories. 7-Hydroxycoumarin-3-carboxylic acid (7-OHCCA), 1-hydroxyl-7-azabenzotriazole (HOAt), 2,2′-azobis(2amidinopropane)dihydrochoride, 1,2-dipalmitoylglycerophosphorylethanolamine (L-α-phosphatidylethanolamine, dipalmitoyl) (DPPE), and 1,2-dipalmitoyl-sn-glycerophosphorylcholine (L-α-phosphatidylcholine, dipalmitoyl) (DPPC) were purchased from Wako. Hydrogen peroxide and sodium hypochlorite solution were purchased from Kishida. Potassium superoxide (KO2) was purchased from Acros. Other reagents were of the highest grade available and used without further purification.
TL;DR: A novel synergistic extraction system was investigated for the possible selective separation of light lanthanoids using an ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, as an extraction solvent and 2-thenoyl Trifluoroacetone and 18-crown-6 as extractants.
Abstract: A novel synergistic extraction system was investigated for the possible selective separation of light lanthanoids using an ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, as an extraction solvent and 2-thenoyltrifluoroacetone and 18-crown-6 as extractants. Trivalent lanthanum was efficiently extracted as a cationic ternary complex by the cation-exchange process, whereas europium and lutetium showed relatively low extractability without forming respective ternary complexes. This result is thought to originate in a size-fitting effect of 18-crown-6 to lanthanum and the unique nature of the ionic liquid as a chelate extraction solvent.
TL;DR: The phase-boundary potential at the interface between an aqueous KCl solution (W) and a hydrophobic room-temperature ionic liquid (RTIL), trioctylmethylammonium bis(nonafluorobutylsulfonyl)imide ([TOMA(+)], containing dicyclohexano-18-crown-6 (DCH18C6), shows the nernstian response to K(+)
Abstract: The phase-boundary potential at the interface between an aqueous KCl solution (W) and a hydrophobic room-temperature ionic liquid (RTIL), trioctylmethylammonium bis(nonafluorobutylsulfonyl)imide ([TOMA+][C4C4N-]), containing dicyclohexano-18-crown-6 (DCH18C6), shows the nernstian response to K+ in W within a polarized potential window of 500 mV between [TOMA+][C4C4N-] and W, demonstrating that hydrophobic RTILs can be used as a nonvolatile ionic medium for liquid-membrane ion-selective electrodes. The complex formation constant of K+ with DCH18C6 in [TOMA+][C4C4N-] is estimated to be on the order of 109 from the upper detection limit using a partition equilibrium model in the presence of a neutral ionophore. The response time of the phase-boundary potential is ∼20 min. Gelled [TOMA+][C4C4N-] also shows the nernstian response to K+, although the upper limit is lower probably due to a change in the solvent properties from the non-gelled [TOMA+][C4C4N-]. The response time of the gelled [TOMA+][C4C4N-] is ∼5 min, shorter than that of the non-gelled [TOMA+][C4C4N-].
TL;DR: A direct and rapid metabolic analysis of a live single cell was performed by live single-cell video-mass spectrometry and revealed the molecular localization of each MS peak.
Abstract: A direct and rapid metabolic analysis of a live single cell was performed by live single-cell video-mass spectrometry. The contents of the cytoplasm and a granule were sucked into a nano-electrospray ionization (nano-ESI) tip, and were directly introduced into a Q-TOF mass spectrometer by nano-spray after the addition of an ionization solvent. The metabolic pathways and the locations of tryptophan and histidine metabolites were traced by this method for a cultured rat basophil leukemia cell line (RBL-2H3). The t-values of detected peaks by a t-test between the different location, e.g. cytoplasm and a granule, revealed the molecular localization of each MS peak. A direct and quick metabolomic analysis of a living cell under simultaneous video-microscopic observations was innovated.
TL;DR: A kind of novel nanocomposites, poly(3-methylthiophene) (P3MT)/gold nanoparticles (AuNPs), were successfully deposited onto the surface of a glassy carbon electrode and showed excellent electrocatalytic activity towards the oxidation of ascorbic acid, dopamine and uric acid.
Abstract: A kind of novel nanocomposites, poly(3-methylthiophene) (P3MT)/gold nanoparticles (AuNPs), were successfully deposited onto the surface of a glassy carbon electrode. A field emission scanning electron microscope (FE-SEM) and electrochemical techniques were used for characterizing this modified electrode. The results showed that the AuNPs were inserted into a P3MT layer uniformly, and formed a porous 3D structure. This modified electrode showed excellent electrocatalytic activity towards the oxidation of ascorbic acid (AA), dopamine (DA) and uric acid (UA); the overlapping anodic peaks of AA, DA and UA were completely divided into three well-defined voltammetric peaks. A further study showed that there existed a linear relationship between the peak current and the concentration of DA in the range of 1.0 x 10(-6) to 3.5 x 10(-5) mol L(-1), and UA in the range of 1.0 x 10(-6) to 3.2 x 10(-5) mol L(-1). The detection limits were 2.4 x 10(-7) mol L(-1) for DA and 1.7 x 10(-7) mol L(-1) for UA. This proposed method was applied to the detection of real samples, and the results were satisfactory.