Biomedical subjects

Yukihiro Ozaki

Publications and source records attributed to Yukihiro Ozaki.

At least 19 recordsLinked to original sources

PubMed2006

Comparison of performance of partial least squares regression, secured principal component regression, and modified secured principal component regression for determination of human serum albumin, gamma-globulin and glucose in buffer solutions and in vivo blood glucose quantification by near-infrared spectroscopy.

The performances of three multivariate analysis methods--partial least squares (PLS) regression, secured principal component regression (sPCR) and modified secured principal component regression (msPCR)--are compared and tested for the determination of human serum albumin (HSA), gamma-globulin, and glucose in phosphate buffer solutions and blood glucose quantification by near-infrared (NIR) spectroscopy. Results from the application of PLS, sPCR and msPCR are presented, showing that the three methods can determine the concentrations of HSA, gamma-globulin and glucose in phosphate buffer solutions almost equally well provided that the prediction samples contain the same spectral information as the calibration samples. On the other hand, when some potential spectral features appear in new measurements, sPCR and msPCR outperform PLS significantly. The reason for this is that such spectral features are not included during calibration, which leads to a degradation in PLS prediction performance, while sPCR and msPCR can improve their predictions for the concentrations of the analytes by removing the uncalibrated features from the original spectra. This point is demonstrated by successfully applying sPCR and msPCR to in vivo blood glucose measurements. This work therefore shows that sPCR and msPCR may provide possible alternatives to PLS in cases where some uncalibrated spectral features are present in measurements used for concentration prediction.

Blood Glucose↗

PubMed2006

Crystallization behaviors of poly(3-hydroxybutyrate) and poly(l-lactic acid) in their immiscible and miscible blends.

By adjusting the molecular weight of the poly(l-lactic acid) (PLLA) component in poly(3-hydroxybutyrate) (PHB)/PLLA blends, we investigated the crystallization behaviors of the two components in their immiscible and miscible 50:50 blends by real time infrared (IR) spectroscopy. In the immiscible PHB/PLLA blend, the stepwise crystallization of PHB and PLLA was realized at different crystallization temperatures. PLLA crystallizes first at a higher temperature (120 degrees C). Its crystallization mechanism from the immiscible PHB/PLLA melt is not affected by the presence of the PHB component, while its crystallization rate is substantially depressed. Subsequently, in the presence of crystallized PLLA, the isothermal melt-crystallization of PHB takes place at a lower temperature (90 degrees C). It is interesting to find that there are two growth stages for PHB. At the early stage of the growth period, the Avrami exponent is 5.0, which is unusually high, while in the late stage, it is 2.5, which is very close to the reported value (n approximately 2.5) for the neat PHB system. In contrast to the stepwise crystallization of PHB and PLLA in the immiscible blends, the almost simultaneous crystallization of PHB and PLLA in the miscible 50:50 blend was observed at the same crystallization temperature (110 degrees C). Detailed dynamic analysis by IR spectroscopy has disclosed that, even in such apparently simultaneous crystallization, the crystallization of PLLA actually occurs faster than that of PHB. It has been found that, both in the immiscible and miscible blends, the crystallization dynamics of PHB are heavily affected by the presence of crystallized PLLA.

Crystallization↗

PubMed2006

Oriented attachment-based assembly of dendritic silver nanostructures at room temperature.

How particles aggregate into an interesting dendritic structure has been the object of research for many years because of its importance in understanding physical processes involved and in designing novel materials. In this work, we for the first time describe an oriented attachment-based assembly mechanism for formation of different types of dendritic silver nanostructures at room temperature. It is found that the concentration of both AgNO(3) and p-aminoazobenzene (PA) molecules has a significant effect on the formation and growth of these novel nanostructures. Characterization by transmission electron microscopy (TEM) clearly shows that the dendritic silver nanostructures can be obtained through the preferential oriented growth along a crystallographically special direction. Interestingly, we observe that the oriented attachment at room temperature can also take place between relatively large single-crystalline silver particles with a diameter range from 20 to 60 nm, which may provide a new possibility for the design of novel metal nanostructures by using large metal nanoparticles as building blocks at room temperature. Moreover, a surface-enhanced Raman scattering (SERS) technique is used to investigate the role of PA molecules during the growth of the dendritic silver nanostructures.

Journal Article↗

PubMed2006

Variations in steady-state and time-resolved background luminescence from surface-enhanced resonance Raman scattering-active single Ag nanoaggregates.

We observed a background luminescence emission that was associated with surface-enhanced resonance Raman scattering (SERRS) of rhodamine 6G (R6G) molecules adsorbed on single Ag nanoaggregates and investigated the origin of the background luminescence. Thanks to the observation of single nanoaggregates, we clearly identified nanoaggregate-by-nanoaggregate variations in the steady-state and time-resolved background luminescence spectra of each nanoaggregate. From the variations in the steady-state spectra, two kinds of key properties were revealed. First, the background luminescence spectra were divided into four components: one fluorescence band corresponding to the monomers of R6G and three Lorentzian bands whose maxima were red-shifted from the fluorescence maximum of the monomer by several tens of nanometers. On the basis of the red-shifted luminescence maxima, and experimental and theoretical studies of background luminescence, we attributed the three background luminescences to fluorescence from aggregates (dimer and two kinds of higher-order aggregates) of R6G molecules on an Ag surface. Second, a positive correlation was observed between wavelengths of background luminescence maxima and wavelengths of plasmon resonance maxima. This positive correlation invoked the idea that the dipoles of both the background luminescence and the plasmon radiation are coupled with each other. From the key observations in the steady-state background luminescence spectra, we propose that two factors contribute to the variations in the steady-state background luminescence spectra; one is the aggregation (monomer, dimer, and two kinds of higher-order aggregates) of R6G molecules on an Ag surface, and the other is plasmon resonance maxima of single Ag nanoaggregates. Considering these two factors, we propose that the variations in the time-resolved background luminescence spectra are associated with deaggregation of R6G molecules (higher- to lower-order aggregates) and temporal shifts in the plasmon resonance maxima of single Ag nanoaggregates.

Image Processing, Computer-Assisted↗

PubMed2006

Noise perturbation in functional principal component analysis filtering for two-dimensional correlation spectroscopy: its theory and application to infrared spectra of a poly(3-hydroxybutyrate) thin film.

A method based on noise perturbation in functional principal component analysis (NPFPCA) is for the first time introduced to overcome the noise interference problem in two-dimensional correlation spectroscopy (2D-COS). By the systematic addition of synthetic noise to the dynamic multivariate spectral data, the functional principal component analysis (FPCA) described in this report is able to accurately determine which eigenvectors are representing significant signals instead of noise in the original data. This feature is especially useful for the data reconstruction and noise filtering. Reconstructed data resulted from the smooth eigenvectors can produce much more reliable 2D correlation spectra by removing the correlation artifacts from noise, which in turn enable more accurate interpretation of the spectral variations. The usefulness of this method is demonstrated with a theoretical framework and applications to the 2D correlation analyses of both simulated data and temperature-dependent reflection-absorption infrared spectra of a poly(3-hydroxybutyrate) (PHB) thin film.

Absorption↗

PubMed2006

Characterization of chloramphenicol palmitate drug polymorphs by Raman mapping with multivariate image segmentation using a spatial directed agglomeration clustering method.

Chemical imaging analysis holds great potential in probing the chemical heterogeneity of samples with high spatial resolution and molecular specificity. This paper demonstrates the implementation of Raman mapping for microscopic characterization of tablets containing chloramphenicol palmitate polymorphs with the aid of a new multivariate image segmentation approach based on spatial directed agglomeration clustering. This approach performs the agglomeration clustering by stepwise merging the pixels possessing both spatial closeness and spectral similarity into clusters that define the image segmentation. The incorporation of spatial closeness into the clustering process enables the approach to improve the robustness and avoid poorly defined image segmentation arising from clusters with highly separated pixels. Additionally, the stepwise merging of clusters offers an F-statistic-based procedure to automatically ascertain the number of image segments. Raman mapping analysis of tablets containing two polymorphs of chloramphenicol palmitate followed by multivariate image segmentation reveals that the proposed technique offers the identification of each polymorph and a quantitative visualization of the spatial distribution of the polymorphs identified. This technique holds promise in rapid, noninvasive, and quantitative polymorph analysis for pharmaceutical production processes.

Chloramphenicol↗

PubMed2006

Comparative evaluation of bioactivity change of crystalline trypsin during compression by chemoinformatics and 2-D Fourier-transform infrared spectroscopy.

The purpose of this study is to develop a method of evaluating the enzymatic activity of trypsin in a solid-state based on Fourier transform infrared (FT-IR) spectra using chemoinformatics and two-dimensional (2-D) correlation spectroscopy. Crystalline trypsin powders are compressed at 0-4000 kg cm-2 by a compression/tension tester. The enzymatic activity of trypsin is assayed by the kinetic degradation method. Spectra of 10 calibration sample sets are recorded 3 times with a FT-IR spectrometer. The maximum intensity of FT-IR spectra and enzymatic activity of trypsin decrease as the compression pressure increases. The FT-IR spectra of trypsin samples are subjected to a principal component regression (PCR). A plot of the calibration data obtained is made between the actual and predicted trypsin activity based on a two-component model with gamma2=0.909 (n=30). The regression vector is almost the same as the loading vector for PC1. On the other hand, a generalized two-dimensional (2-D) correlation spectroscopic method is applied to FT-IR spectra of compressed trypsin. The result is consistent with that of the chemoinformatics method. The FT-IR chemoinformatics method allows for solid-state quantitative analysis of the bioactivity of the bulk powder of a polypeptide drug.

Animals↗

PubMed2006

Elucidation of interaction between metal-free tetraphenylporphine and surface Ag atoms through temporal fluctuation of surface-enhanced resonance Raman scattering and background-light emission.

We have observed simultaneously temporal fluctuation of surface-enhanced resonance Raman scattering (SERRS) and its background-light emission from single Ag nanoaggregates that were adsorbed with metal-free tetraphenylporphine (H(2)TPP) molecules. We found that temporally stable SERRS spectra showed clearly a SERRS band that is attributed to a stretching mode of a chemical bond between a carbon atom and a non-hydrogenated nitrogen atom (C(alpha)-N). This stretching mode was not observed in regular resonance Raman spectra which are free from surface enhancement. On the other hand, we also found that temporally unstable SERRS spectra did not clearly show a C(alpha)-N stretching mode in SERRS bands. Furthermore, temporally stable SERRS spectra were accompanied by temporally stable background-light emission. Kobayashi et al. [J. Phys. Chem. 1985, 89, 5174] reported that formation of an Ag-N bond between surface Ag atoms and non-hydrogenated N atoms in a pyrrole ring enhances the intensity of a C(alpha)-N stretching mode. Thus, the observed relationship between clear appearance of a C(alpha)-N stretching mode and temporal stability of SERRS plus background-light emission strongly suggests that formation of a stable Ag-N bond suppresses fluctuation of both SERRS and background-light emission. Furthermore, the observed relationship implies that chemical contribution to SERRS is stabilization of H(2)TPP molecules that are adsorbed on SERRS-active sites by formation of Ag-N bonds. Additionally, we attributed background-light emission to luminescence of complexes between H(2)TPP molecules and surface Ag atoms considering possible formation of Ag-N bonds, synchronized SERRS intensity with background-light emission intensity, blue-shifted background-light emission maxima from normal fluorescence maxima, and previous reports related to electronic structures of H(2)TPP molecules on Ag surfaces.

Journal Article↗

PubMed2006

Investigation into pH-responsive self-assembled monolayers of acylated anthranilate-terminated alkanethiol on a gold surface.

This article describes the preparation of pH-responsive self-assembled monolayers (SAMs) of acylated anthranilate-terminated alkanethiol. These monolayers are formed by chemisorption of the alkanethiol molecules onto a gold surface, resulting in different wetting properties of the surfaces depending upon the pH. By using various characterization techniques (e.g., infrared spectroscopy, cyclic voltammetry, contact angle measurements, and surface energy analysis), we have found that the changes in the wetting properties originate from the different surface structures of the monolayers in different pH environments. From surface energy analysis, we found that the disperse components of the surface energy on such SAMs predominate after treatment with pH 1 water, whereas the polar components of the surface energy on such SAMs predominate after treatment with pH 13 water. It is greatly anticipated that this line of research will provide new insight into the mechanism behind pH-responsive properties, facilitating the design and synthesis of new surface-active molecules for the fabrication of pH-responsive functional surfaces.

Journal Article↗

PubMed2006

Surface-enhanced resonance Raman scattering and background light emission coupled with plasmon of single Ag nanoaggregates.

We investigated the optical properties of isolated single aggregates of Ag nanoparticles (Ag nanoaggregates) on which rhodamine 6G molecules were adsorbed to reveal experimentally a correlation among plasmon resonance Rayleigh scattering, surface-enhanced resonance Raman scattering (SERRS), and its background light emission. From the lack of excitation-laser energy dependence of background emission maxima we concluded that the background emission is luminescence, not Raman scattering. The polarization dependence of both SERRS and background emission was the same as that of the lowest-energy plasmon resonance maxima, which is associated with a longitudinal plasmon. From the common polarization dependence, we identified that the lowest-energy plasmon is coupled with both SERRS and background emission. In addition, we revealed that the lowest-energy plasmon with a higher quality factor (Q factor) yields larger SERRS and background emission intensity. Also, we identified that the Q factor dependence of the SERRS intensity was similar to that of the background emission intensity. This similarity directly supported us to demonstrate an enhancement of both SERRS and background emission by coupling with a common plasmon radiative mode.

Journal Article↗

PubMed2006

Designed fabrication of ordered porous au/ag nanostructured films for surface-enhanced Raman scattering substrates.

This article reports the designed preparation of two different kinds of novel porous metal nanostructured films, namely, an ordered macroporous Au/Ag nanostructured film and an ordered hollow Au/Ag nanostructured film. Different from previous reports, the presently proposed method can be conveniently used to control film structures by simply varying the experimental conditions. The morphology of these films has been characterized by scanning electron microscopy (SEM), and their performance as surface-enhanced Raman scattering (SERS) substrates has been evaluated by using rhodamine 6G (R6G) as a probe molecule. We show that such porous nanostructured films consisting of larger interconnected aggregates are highly desirable as SERS substrates in terms of high Raman intensity enhancement, excellent stability, and reproducibility. The interconnected nanostructured aggregate, long-range ordering porosity, and nanoscale roughness are important factors responsible for this large SERS enhancement ability.

Journal Article↗

PubMed2006

Two-dimensional fluorescence correlation spectroscopy IV: resolution of fluorescence of tryptophan residues in alcohol dehydrogenase and lysozyme.

Generalized two-dimensional (2D) fluorescence correlation spectroscopy has been used to resolve the fluorescence spectra of two tryptophan (Trp) residues in alcohol dehydrogenase and lysozyme. In each protein, one Trp residue is buried in a hydrophobic domain of the protein matrix and the other Trp residue is located at a hydrophilic domain close to the protein-water interface. Fluorescence quenching by iodide ion, a hydrophilic quencher, was employed as a perturbation to induce the intensity change in the spectra. The Trp residue which is located at the hydrophilic domain is effectively quenched by the quencher, while the Trp residue located at the hydrophobic domain is protected from the quenching. Therefore, the fluorescence of these two Trp residues have a different sensitivity to the quenching, showing a different response to the concentration of the quencher. Fluorescence spectra of the two Trp residues in alcohol dehydrogenase, which are heavily overlapped in conventional one-dimensional spectra, have been successfully resolved by the 2D correlation technique. From the asynchronous correlation map, it was revealed that the quenching of Trp located at the hydrophobic part was brought about after that of Trp located at the hydrophilic part. In contrast, the fluorescence spectra of the two Trp residues could not be resolved after the alcohol dehydrogenase was denatured with guanidine hydrochloride. These results are consistent with the well-known structure of alcohol dehydrogenase. Furthermore, it was elucidated that the present 2D analysis is not interfered by Raman bands of the solvent, which sometimes bring difficulty into the conventional fluorescence analysis. Fluorescence spectra of the Trp residues in lysozyme could not be resolved by the 2D correlation technique. The differences between the two proteins are attributed to the fact that the Trp residue in the hydrophobic site of lysozyme is not sufficiently protected from the quenching.

Alcohol Dehydrogenase↗

PubMed2006

Moving window cross validation: a new cross validation method for the selection of a rational number of components in a partial least squares calibration model.

A new cross validation method called moving window cross validation (MWCV) is proposed in this study, as a novel method for selecting the rational number of components for building an efficient calibration model in analytical chemistry. This method works with an innovative pattern to split a validation set by a number of given windows that move synchronously along proper subsets of all the samples. Calculations for the mean value of all mean squares error in cross validations (MSECVs) for all splitting forms are made for different numbers of components, and then the optimal number of components for the model can be selected. Performance of MWCV is compared with that of two cross validation methods, leave-one-out cross validation (LOOCV) and Monte Carlo cross validation (MCCV), for partial least squares (PLS) models developed on one simulated data set and two real near-infrared (NIR) spectral data sets. The results reveal that MWCV can avoid a tendency to over-fit the data. Selection of the optimal number of components can be easily made by MWCV because it yields a global minimum in root MSECV at the optimal number of components. Changes in the window size and window number of MWCV do not greatly influence the selection of the number of components. MWCV is demonstrated to be an effective, simple and accurate cross validation method.

Journal Article↗

PubMed2006

Characterization of Langmuir-Blodgett films of a ferroelectric liquid crystal.

Molecular orientation, structure, and phase transition behaviors in Langmuir-Blodgett (LB) and cast films of a ferroelectric liquid crystal of sec-butyl 6-(4-(nonyloxy)benzoyloxy)-2-naphthoate (FLC-1) are determined by ultraviolet (UV) spectroscopy, X-ray diffraction, and infrared (IR) spectroscopy. It is found that the orientation angle of chromophores theta in LB films is 41 degrees from the surface normal. The tilt angle of the chromophore changes at 56, 70, and 88 degrees C, respectively, which denotes the presence of phase transitions. Two kinds of layered or isomeric crystal structures of the LB films with layer spacings of 3 and 3.5 nm at room temperature have been found while the latter disappears above 45 degrees C, as confirmed by measurement of temperature-dependent IR spectra.

Journal Article↗

PubMed2006

Modified secured principal component regression for detection of unexpected chromatographic features in herbal fingerprints.

Secured principal component regression is modified for the qualitative analysis of chromatographic fingerprint data sets of herbal samples with residual concentrations. After chromatographic shift-correction and autoscaling are performed on the data, this modified secured principal component regression (msPCR) can detect unexpected chromatographic features in various herbal fingerprints. The successful application of msPCR to two real herbal medicines of Erigeron breviscapus from different geographical origins and Ginkgo biloba from various sources or vendors demonstrates that the proposed method can detect reasonably unexpected features differing from the regulars or not being modeled. From a chemical point of view, the causes have also been explained to corroborate the results. Moreover, it presents a viable approach for the qualitative evaluation of diverse herbal objects with a regular class of chromatographic fingerprints.

Journal Article↗

PubMed2006

Epitaxial crystallization of isotactic poly(methyl methacrylate) on highly oriented polyethylene.

The annealing behavior of amorphous i-PMMA thin films on highly oriented HDPE substrates was studied by transmission infrared spectroscopy and electron diffraction. The i-PMMA thin film on highly oriented HDPE exhibits a much faster crystallization rate than usual, providing not only a good method for the preparation of crystalline i-PMMA thin and ultrathin film, but also the convenience to observe the crystallization process by infrared spectroscopy in situ. The overall crystallization kinetics of the i-PMMA thin film on the highly oriented HDPE layer was also explored in this work, and an Avrami exponent of about 2 was obtained. The accelerated crystallization behavior indicates a special interaction between HDPE and i-PMMA, which favors the nucleation and crystallization of i-PMMA. This special interaction leads also to an oriented alignment of i-PMMA on the HDPE substrate with both polymer chains parallel, i.e., the occurrence of heteroepitaxy, which could be verified by the polarized infrared spectra and electron diffraction pattern. Electron diffraction analysis further demonstrated that the contact planes of this epitaxial system are (100) lattice planes of both polymers. This can be explained in terms of a two-dimensional lattice matching.

Journal Article↗

PubMed2006

Molecular weight dependence of the poly(L-lactide)/poly(D-lactide) Stereocomplex at the air-water interface.

The molecular weight dependence of poly(L-lactide)/poly(D-lactide) (PLLA/PDLA) stereocomplex behavior at the air-water interface was studied by surface pressure-area (pi-A) isotherms and atomic force microscopy (AFM). It was found that the compression-induced sterecomplexation of a PDLA/PLLA equimolar blend with high molecular weight (M(w) = 1 x 10(6) and 9.8 x 10(5), respectively) could occur at the air-water interface. This result is in marked contrast with the stereocomplexation of PDLA/PLLA blends in the bulk from the melt or in solutions, where the homocrystallites of either PLLA or PDLA rather than stereocomplex crystallites will be formed preferentially when the molecular weights of both polymers are higher than 1 x 10(5). Unexpectedly, the Langmuir-Blodgett behavior of the PDLA/PLLA blend with lower molecular weight (M(w) = 4 x 10(3) and 3.2 x 10(3), respectively), which should be favored in the stereocomplex, was distinct from that of other higher molecular weight blends. AFM images clearly disclosed for the first time the morphological changes of the equimolar blends of PLLA and PDLA at the air-water interface induced by increasing the surface pressure of the monolayer. Of particular note, the bilayer mechanism for the plateau in the isotherm was directly verified by the AFM height images.

Air↗

PubMed2006

Study on temperature-dependent changes in hydrogen bonds in cellulose Ibeta by infrared spectroscopy with perturbation-correlation moving-window two-dimensional correlation spectroscopy.

Infrared (IR) spectra were measured for cellulose Ibeta prepared from the mantle of Halocynthia roretzi over a temperature range of 30-260 degrees C to explore the temperature-dependent changes in hydrogen bonds (H-bonds) in the crystal. Structural changes at the phase transition temperature of 220 degrees C are elucidated at the functional group level by perturbation-correlation moving-window two-dimensional (PCMW2D) correlation spectroscopy. The PCMW2D correlation spectra show that the intensities of bands arising from O3-H3...O5 and O2-H2...O6 intrachain H-bonds dramatically decrease at 220 degrees C, whereas the intensity changes of bands due to interchain H-bonds are not observed adequately. These results suggest that the phase transition is induced by the dissociation of the O3-H3...O5 and O2-H2...O6 intrachain H-bonds. However, the interchain H-bonds are not so much responsible for the transition directly.

Carbohydrate Conformation↗