Recent developments of the techniques for measurements of X-ray diffraction and X-ray absorption spectroscopy in very high magnetic fields are reviewed. Miniature pulsed magnets allow us to conduct various kinds of high-field X-ray experiments rather easily; the magnets can be readily installed on a conventional apparatus such as a diffractometer and a cryostat because of its smallness. The results of some experiments on the field-induced phase transition of a rare-earth intermetallic compound (YbInCu4) are also presented.
We have tried to realize an X-ray imaging spectrometer based on the superconducting transition edge sensor (TES) with high energy resolution, a large pixel array, a relatively high absorption efficiency and a high count rate. Our single pixel of Ir/Au TES achieved an excellent energy resolution of 9.4 eV for 5.9 keV X-rays. We have also proposed a pixellated array of Ir-TES where we slightly modify the bias point of each pixel and identify the pixel from the response function of each pixel. Our 10-pixel device, where all pixels are parallel biased, obtained 13 eV (FWHM) at 3 keV energy resolution and 80 µm position resolution. So far, we could successfully operate a 20-pixels device. Further, we are now trying to improve the count rate and the absorption efficiency of TESes, by developing our original new TES geometry which having a radiation absorber that self-adjusts the operating temperature.
Lifetime-broadening-suppressed (LBS) state-selective XAFS spectra can be deduced by analyzing resonant inelastic x-ray scattering (RIXS) in terms of formulae derived from the Kramers-Heisenberg equation. By a combination of third-generation synchrotron sources and spectrometers equipped with a large acceptance as well as high-resolution analyzers, high-quality RIXS data to extract LBS selective XAFS can be collected. In this review, basic aspects of this novel technique are described, and its potentiality as an analytical tool to determine the local electronic and magnetic structures of metal atoms is demonstrated with several recent examples.
Recently, a hybrid mesoporous membrane composed of surfactant-templated mesoporous silica inside a porous anodic alumina membrane has been developed. Since this membrane allows the use of columnar silica-mesopores (silica-nanochannels) as nanofluidic channels, separation of molecules can be realized by mass transport through the silica-nanochannel with molecular dimensions. Here, we review the methods to fabricate the hybrid mesoporous membranes, their structural features, and the analytical applications of hybrid mesoporous membranes.
The development of highly potent chiral discrimination methods that solve the problems of the diastereomer method is described. Explaining the significant results of separations of diastereomers having chiral centers separated by 13 - 27 bonds with reversed-phase HPLC was hitherto impossible. To attract more scientific interest toward the mechanism of the separation, the author proposes a hypothesis, Induced Chiral Fields, that the achiral reversed phases can provide chiral fields depending on the structures of the substrates.
Determining the relative orientation of domains within a protein is an important problem in structural biology, which has been difficult to address by either X-ray crystallography or NMR. The structure of a multidomain protein in a crystal lattice can be altered by crystal packing forces, resulting in different domain arrangements from those in solution. On the other hand, conventional NMR primarily provides short-range structural information, including proton-proton distances derived from nuclear Overhauser effects (NOEs) and torsion angles through vicinal spin couplings. Thus, NMR cannot always determine the precise interdomain arrangements due to the sparsely observed spin interactions between domains. However, the weak alignment of proteins in solution has enabled a new NMR technique to determine the domain arrangement based on the different structural information, which defines the orientation of a structural unit in protein against the magnetic field. This technique relies on the anisotropic nuclear spin interactions that only occur for a molecule in a weakly aligned state. In this review, the basics of the new NMR approach are described with focusing on its application to domain orientation analysis. We also describe our recently established NMR approach using the same spin interactions, which expands the domain arrangement analysis to higher-molecular weight proteins over 100 kDa.
Selective and sensitive tumor imaging in vivo is one of the most requested methodologies in medical sciences. Although several imaging modalities have been developed including positron emission tomography (PET) and magnetic resonance (MR) imaging for the detection of tumors, none of these modalities can activate the signals upon being accumulated or uptaken to tumor sites. Among these modalities, only optical fluorescence imaging has a marked advantage, that is, their signals can be dramatically increased upon detecting some biological features. In this short review, I will introduce some recent strategies for activatable optical fluorescence imaging of tumors, and discuss their advantages over other modalities.
A cellular analyzing system including a “real-time cellular imaging system” and a “comprehensive analyzing system for cellular responses” was developed. A “real-time cellular imaging system” is a system used to measure real-time imaging of multiple phenomena of a single cell with high special and temporal resolutions for the purpose to understand the pathology and physiology in a single cell and realize to single cell level diagnosis. A “real-time cellular imaging system” includes multi-probe imaging with AFM (atomic force microscopy), optical and SECM (scanning electrochemical microscopy) modes, which provides us with topological information and biochemical reactions at the local area of the interior and exterior of a cell. Scanning electrochemical/optical microscopy was applied to image PC12 cells. On the other hand, cells respond to their specific substances via their ligands. Therefore, the comprehensive analysis of protein-protein interaction is the important issue to determine the functions of cells. For this purpose, a “comprehensive analysis system for cellular responses” was developed. This system is based on SPR (surface plasmon resonance) and MS (mass spectrometry) using a nano-fabricated substrate. The interaction between IL-1β and anti-IL-1β antibodies was detected.
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.
A production method for a positron microprobe using a β+-decay radioisotope (22Na) source has been investigated. When a magnetically guided positron beam was extracted from the magnetic field, the combination of an extraction coil and a magnetic lens enabled us to focus the positron beam by a factor of 10 and to achieve a high transport efficiency (71%). A 150-nm-thick Ni(100) thin film was mounted at the focal point of the magnetic lens and was used as a remoderator for brightness enhancement in a transmission geometry. The remoderated positrons were accelerated by an electrostatic lens and focused on the target by an objective magnetic lens. As a result, a 4-mm-diameter positron beam could be transformed into a microprobe of 60 µm or less with 4.2% total efficiency. The S parameter profile obtained by a single-line scan of a test specimen coincided well with the defect distribution. This technique for a positron microprobe is available to an accelerator-based high-intensity positron source and allows 3-dimensional vacancy-type defect analysis and a positron source for a transmission positron microscope.
Spin-polarized ion scattering spectroscopy using an electron-spin-polarized 4He+ ion beam was developed as a novel analytical method of the element selective spin state at outermost surfaces. Spin-polarized He+ ions were generated from the Penning ionization of metastable He 23S1 atoms (He*), which were spin-polarized by optical pumping (OP). The spin polarization of He* (PHe*) was observed to be the highest with an OP radiation density of about 0.05 W cm-2, and a further increase of the OP radiation density reduced PHe*. This decrease of PHe* is attributed to imperfect polarization of the OP radiation, hence optimization of the OP radiation density is essential to obtain He+ ions with high spin polarization. As a result of this optimization, we successfully observed the spin dependence of the scattered He+ ion yield on an Fe(100) surface exposed to an oxygen atmosphere.
We have developed a miniature electron ion coincidence (EICO) analyzer mounted on a conflat flange with an outer diameter of 114 mm. It consists of a cylindrical mirror analyzer (CMA), a time-of-flight ion mass spectrometer (TOF-MS), a commercially available linear motion feedthrough, and a tilt adjustment mechanism. Each sample surface was irradiated by synchrotron radiation, and the energies of emitted electrons were analyzed and detected by the CMA, while desorbed ions were collected by the TOF-MS in coincidence with the electrons. The performance of the EICO analyzer was tested by measuring the Auger-electron H+ photoion coincidence spectrum of condensed water at 4a1 ← O 1s resonance.
Terrestrial carbonate deposits with a banded layer structure can be good tools for the extraction of past environmental information on global and local scales using trace element concentrations and stable isotope ratios. The absolute age dating is most important for the reconstruction of an environmental chronicle. The measurements of fluorescent annual bandings in stalagmites using a microscopic spectrofluorometer with an XY-stage can be a convenient dating method and are especially effective for young samples whose absolute age is very difficult to be determined by other methods. The number of annual bandings was objectively counted using a personal computer. The optimal conditions for the measurements are discussed. The annual banding in stalagmites is caused by the seasonal differences in the fulvic acid concentrations in the dripping water which forms speleothems.
Solid/liquid interfaces are important locations for various chemical reactions, such as electrode chemical reactions and metal corrosions. Conventional surface analytical methods, such as XPS and SEM-EDS, have been applied to solid materials after being removed from the liquid phase. These methods do not involve direct observation, although useful information is available. It is important to directly observe surface reactions on solid materials in the liquid phase in order to understand the details of these reactions. One feasible method of doing this is 3D micro-XRF analysis. The confocal 3D micro XRF method enables nondestructive x-ray elemental analysis of localized microspace. We have applied a confocal 3D micro-XRF instrument for solid/liquid interface analysis. This technique was applied for direct observation of the chemical deposition of Cu on an Fe plate and the dissolution of Fe in a CuSO4 solution.
Optimized experimental conditions of infrared p-polarized multiple-angle incidence resolution spectrometry (p-MAIRS) for the analysis of ultrathin films on glass have been explored. When the original MAIRS technique is employed for thin-film analysis on a substrate of germanium or silicon, which exhibits a high refractive index, an established experimental condition without optimization can be adapted for the measurements. On the other hand, the p-MAIRS technique that has been developed for analysis on a low-refractive-index material requires, however, optimization of the experimental parameters for a ‘uantitative’ molecular orientation analysis. The optimization cannot be performed by considering only for optics in the spectrometer, but for optics concerning the substrate should also be considered. In the present study, an optimized condition for infrared p-MAIRS analysis on glass has been revealed, which can be used for quantitative molecular orientation analysis in ultrathin films on glass.
Enhancement of the Raman scattering and IR absorption activities due to the electron-attachment was investigated for water systems by DFT calculations. DFT calculation of a 6-ring water cluster system that included the diffusive nature of electrons well reproduced the Raman enhancement effects and Raman shifts of the OH stretching modes observed in experiments. Based on the same model and calculations, enhancement of the IR absorption activity was also studied and was found to also be improved. Furthermore, the same calculation revealed that the enhancement can be also expected not only in the OH stretching but also in the lower wavenumber region. The enhancement factors for the various vibrational modes of the OH groups range from 102 - 105 thanks to the electron addition. Based on the coincidence between the theoretical model and the experimental results for the Raman signals and theoretical prediction for IR absorption, new enhancement techniques based on an electron-attachment in both Raman scattering and IR absorption, denoted as “electron-enhanced vibrational spectroscopy (EEVS)”, is proposed, where molecular polarizability itself is modulated by the strong electrostatic field induced by neighboring electrons.
An efficient and highly sensitive chemiluminescence (CL) technique is proposed in the current study for detection of low levels of human serum albumin (HSA). Chemiluminescence (CL) produced during interaction between fluoresceinyl cypridina luciferin analog (FCLA)-1O2 can be modified with the presence of HSA. The conventional CL technique uses a quenching effect of HSA for its quantitative measurement. We are reporting here that the CL intensity can be enhanced, rather than quenched, by the addition of HSA. The CL signal can be linearly correlated with the HSA concentration over a clinically interesting range of 5 × 10-9 - 8 × 10-8 mol L-1, with a detection limit of 2.5 × 10-9 mol L-1. The determination result was consistent with that obtained from conventional methods. One possible mechanism of HSA detection technique using CL enhancement approach is discussed. Intermolecular energy transfer in chemiluminescence systems and changes of microenvironment are likely to be contributors of the CL enhancement with HSA.
This study presents a new microscopic method for the measurements of the deformation of liquid surfaces induced by a localized direct current (dc) electric field in a noncontact manner. Since the dielectric constant of aqueous and organic liquids is larger than that of air, the liquids tend to occupy a space with a stronger electric field. The horizontal level of transparent surfaces was measured with a constructed microscopic system that possessed a resolution of about 2 µm. When a rod electrode (2.0 mm in radius) was brought near to a liquid surface vertically within 150 - 200 µm and a dc voltage (50 - 75 V) was applied, the surface just under the electrode rose by 4 - 19 µm. The deformation of the liquid surfaces was quantitatively analyzed by using a dielectric force, surface tension, and hydrostatic pressure.
The experimental conditions of the sample delivery inside the reagent-release capillary-based capillary-assembled microchip (RRC-based CAs-CHIP) were optimized and the reagent release procedure in the RRC is discussed. Recently, our group introduced the basic concept of the “drop-and-sip” fluid handling technique (Anal. Chem., 2007, 79, 908). A microliter volume of sample solution is dropped on the inlet hole and is sipped into another hole, producing a sample plug flow in the main poly(dimethyl siloxane) (PDMS) channel, concurrently filling each sensing capillary that faces the main PDMS channel. However, the detailed evaluation of the successful sample delivery condition and the reagent release behavior in the RRC has not been fully discussed. Under our experimental conditions, ca. 0.6 - 2.4 s of sample plug-RRC contact time allowed the successful sample introduction into the RRC by capillary force without any reagent leakage or disturbance of the sample plug flow. On the other hand, reagent release behavior inside the RRC is governed by both convective and diffusive mass transport, which leads to a faster mixing time of the sample with reagents immobilized inside the RRC compared to that expected from the simple diffusion alone.
Magnetophoretic velocimetry is a novel technique to measure the magnetic susceptibility of a single microparticle. This techinique could be applied to study the interfacial adsorption equilibria of a paramagnetic dysprosium(III) ion with capric, lauric or stearic acid for a single 2-fluorotoluene microdroplet. The observed magnetic susceptibility of the micro-organic droplets was reciprocally proportional to its radius in each case. From the proportional constant, the interfacial concentration of Dy(III) was determined. Furthermore, the dependences of the interfacial concentration on the initial Dy(III) concentration and pH were examined in order to analyze the adsorption equilibrium. Finally, the saturated interfacial concentration and the interfacial adsorption constant at the infinite dilution of Dy(III)-laurate complex were evaluated as 4.8 × 10-10 mol cm-2 and 3.4 × 10-2 dm, respectively.
The development of retention prediction models for the seven ginsenosides (Rf, Rg1, Rd, Re, Rc, Rb2 and Rb1) on a polyvinyl alcohol (PVA)-bonded stationary phase at subambient temperatures is presented. The models were derived using multiple linear regression (MLR) and artificial neural network (ANN) using the logarithm of the retention factor (log k) as the dependent variable. Using stepwise MLR, the retention of the analytes under all temperature conditions was satisfactorily described by a three-predictor model; the predictors being the percentage of acetonitrile (%MeCN) in the mobile phase, the number of hydrogen bond donors (HBD) and the ovality (Ov) of the compounds. These predictors account for the contribution of the solute-related variables (HBD and Ov) and the influence of the mobile phase composition (%MeCN) on the retention behavior of the ginsenosides. The MLR models produced adequate fits, as proven by the high calibration R2 values of the predicted versus the observed log k (> 0.95) and good predictive properties, as indicated by the high cross-validated q2 (> 0.93) and high R2 (> 0.95) values obtained from the test set. ANN modeling was also conducted using the predictors that were derived from MLR as inputs and log k as the output. A comparison of the models derived from both MLR and ANN revealed that the trained ANNs showed better predictive abilities than the MLR models in all temperature conditions as demonstrated by their higher R2 values for both training and test sets and lower average percentage deviation of the predicted log k from the observed log k of the test compounds. The ANN models also showed excellent performance when applied to the prediction of the seven ginsenosides in different sample matrices.
This report describes the development of novel wired chip devices for μ-HPLC analyses. The monolithic capillary column to be wired was prepared using a tri-functional epoxy monomer, tris(2,3-epoxypropyl)isocyanurate with a diamine, 4-[(4-aminocyclohexyl)methyl]cyclohexylamine. The prepared column was evaluated by SEM observation of the sectional structure of column and μ-HPLC. In addition, the reproducibility in the preparation of long capillary columns having nearly 1 m length was extensively examined for applications of novel wired chip devices. The authors demonstrated that the monolithic structure of the prepared long capillary could be finely controlled under the strictly maintained operational conditions and thus the relative standard deviation (RSD) of the column properties such as the number of theoretical plates, retention factor, and permeability could be well controlled to become less than 10%. Furthermore, the wired chip device column showed that its high performance was kept even after chip preparation.
In this study, micelles prepared from distearoylphosphatidylethanolamine with covalently attached poly(ethylene) glycol) (PEG) of molecular weight 2000 (DSPE-PEG-2000) were employed in micellar electrokinetic chromatography (MEKC) as pseudostationary phases. Since DSPE-PEG-2000 contains long hydrophobic alkyl chains, an anionic phosphate group, and hydrophilic PEG chains, the prepared micelles are expected to provide a characteristic retention behavior for both neutral and ionic compounds. As a typical example, a baseline separation of phenol and 2-naphthol was successfully achieved by using the DSPE-PEG-2000 micelles as a background electrolyte for MEKC; such success clearly shows that the micelles can retain electrically neutral compounds. The MEKC separations of anionic and cationic compounds with a DSPE-PEG-2000 micellar solution and the enantioseparation of binaphthyl compounds with mixed micelles containing bile salt are also discussed.
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.
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.
The techniques of chemical ligation have attracted great attention as an alternative to enzymatic joining of DNA ends. Here we introduce the photoligation of anthracene-modified ODN conjugates through anthracene cyclodimer formation. The effect of the positions and the kinds of single base mismatch on the template was evaluated using eight templates with one-base displacements. We found out that the yield of the ligation was affected by mispairing in a position-dependent manner. Such results would be attributed to the disruption of the local structure at the ligation site.