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At least 613 records · Page 34Linked to original sources

PubMed2003

Structure of human alpha1-acid glycoprotein and its high-affinity binding site.

Secondary and tertiary structures of human blood alpha(1)-acid glycoprotein, a member of the lipocalin family, have been studied for the first time by infrared and Raman spectroscopies. Vibrational spectroscopy confirmed details of the secondary structure and the structure content predicted by homology modeling of the protein moiety, i.e., 15% alpha-helices, 41% beta-sheets, 12% beta-turns, 8% bands, and 24% unordered structure at pH 7.4. Our model shows that the protein folds as a highly symmetrical all-beta protein dominated by a single eight-stranded antiparallel beta-sheet. Thermal dynamics in the range 20-70 degrees C followed by Raman spectroscopy and analyzed by principle component analysis revealed full reversibility of the protein motion upon heating dominated by decreasing of beta-sheets. Raman difference spectroscopy confirmed the proximity of Trp(122) to progesterone binding.

Amino Acid Sequence↗

PubMed2003

Raman spectroscopy as a tool for measuring mutual-diffusion coefficients in hydrogels.

Raman spectroscopy has been exploited to characterize the diffusion properties of solutes in hydrogels. Raman active vibrations were used as intrinsic probes of the solute concentration along gel cylinders. The resulting one-dimensional solute distribution, characterized as a function of both time and space, could be analyzed with a model based on Fick's diffusion law, and the mutual-diffusion coefficient (Dm) was then determined. To illustrate the potential of this approach, we measured the Dm of two polyethylene glycols (PEG) in Ca-alginate gels. In this case, the intensity of the CH stretching band was used to obtain the concentration profiles of PEGs, whereas the OH stretching band of water was used as an internal intensity standard. In addition to providing a straightforward approach to measuring diffusion coefficients, the Raman profile analysis provides information relative to the accessibility of gels to large molecules. As an example, it was found that the PEG penetration in Ca-alginate gels was restricted, a phenomenon that was dependent on PEG size. The Raman technique presented here effectively characterizes transport properties of solutes in gels, and such characterization is required for developing several technical applications of gels, such as their use as materials for controlled release of drugs.

Diffusion↗

PubMed2002

Discriminating vital tumor from necrotic tissue in human glioblastoma tissue samples by Raman spectroscopy.

Vital and necrotic glioblastoma tissues were studied by Raman microspectroscopy to identify possibilities for the development of an in vivo Raman method for real-time intraoperative brain biopsy guidance. The histologic malignancy grade of gliomas depends on the presence of parameters such as endothelial proliferation and necrosis, which are often not evenly distributed within the tumor. Because tissue samples obtained by stereotactic surgery are relatively small, sampling errors may easily occur by missing these crucial features. Although necrosis is important for grading, specimens containing only necrosis are diagnostically useless. Raman microspectroscopic mapping experiments were performed on unfixed cryosections of glioblastoma, obtained from 20 patients. After spectral acquisition, a clustering analysis was performed, resulting in groups of similar spectra. Each cluster was assigned a color, and pseudo-color Raman maps of the tissue sections were constructed. After the Raman experiments, the tissue sections were stained for histopathologic analysis, enabling identification of the histologic origin of the Raman spectra and assignment of the Raman spectral clusters to either vital or necrotic tissue. A classification model for discrimination between vital and necrotic tumor tissue based on linear discriminant analysis was developed. The classification model was evaluated using independent Raman data obtained from nine other tissue sections and yielded 100% accuracy. Information about the biochemical differences between necrosis and vital tumor was obtained by the analysis of difference spectra. Necrotic tissue was found to consistently contain higher levels of cholesterol (-esters). This in vitro result indicates that Raman spectra contain the information to distinguish vital glioblastoma from necrosis and makes Raman spectroscopy a powerful candidate for guidance of stereotactic brain biopsy.

Brain↗

PubMed2004

[The analysis for Raman spectra of Nd:YVO4].

The factor group symmetry analysis method was used to analyse the Raman spectra of neodymium-doped yttrium orthoanadate Nd:YVO4 which were measured at room temperature with different geometrical configurations. All the Raman peaks were assigned on the basis of the group theory and lattice dynamics thoery. According to the peak numbers of the Raman spectra, we concluded that the primitive cell of Nd:YVO4 contains four formula units.

Neodymium↗

PubMed1978