Raman spectroscopy and multivariate analysis of serum samples from breast cancer patients.

Serum samples were studied using Raman spectroscopy and analyzed through the multivariate statistical methods of principal component analysis (PCA) and linear discriminant analysis (LDA). The blood samples were obtained from 11 patients who were clinically diagnosed with breast cancer and 12 healthy volunteer controls. The PCA allowed us to define the wavelength differences between the spectral bands of the control and patient groups. However, since the differences in the involved molecules were in their tertiary or quaternary structure, it was not possible to determine what molecule caused the observed differences in the spectra. The ratio of the corresponding band intensities were analyzed by calculating the p values and it was found that only seven of these band ratios were significant and corresponded to proteins, phospholipids, and polysaccharides. These specific bands might be helpful during screening for breast cancer using Raman Spectroscopy of serum samples. It is also shown that serum samples from patients with breast cancer and from the control group can be discriminated when the LDA is applied to their Raman spectra.

CdTe surface roughness by Raman spectroscopy using the 830 nm wavelength.

A Raman spectroscopic study was performed to detect the surface roughness of a cadmium telluride (CdTe) wafer sample, using the 514.5, 632.8 and 830.0 nm excitations wavelengths. To verify the relation between the roughness and the structure of Raman spectra, in certain zones of the sample, we measured their roughness with an atomic force microscopy. It was found that, using the 830 nm wavelength there is a direct correspondence between the spectrum structure and the surface roughness. For the others wavelengths it was found, however, that there is not a clearly correspondence between them. Our results suggest that, using the excitation wavelength of 830 nm the Raman spectroscopy can be used as an on-line roughness monitor on the CdTe growth.

Qualitative study of ethanol content in tequilas by Raman spectroscopy and principal component analysis.

Using Raman spectroscopy, with an excitation radiation source of 514.5 nm, and principal component analysis (PCA) was elaborated a method to study qualitatively the ethanol content in tequila samples. This method is based in the OH region profile (water) of the Raman spectra. Also, this method, using the fluorescence background of the Raman spectra, can be used to distinguish silver tequila from aged tequilas. The first three PCs of the Raman spectra, that provide the 99% of the total variance of the data set, were used for the samples classification. The PCA1 and PCA2 are related with the water (or ethanol) content of the sample, whereas the PCA3 is related with the fluorescence background of the Raman spectra.

The application of NIR Raman spectroscopy in the assessment of serum thyroid-stimulating hormone in rats.

Serum blood samples of euthyroid and thyroidectomized rats treated with thyrotropin-releasing hormone (TRH) were analyzed on aluminum substrates using the near-infrared Raman spectroscopy (830 nm). Spectra of thyroid-stimulating hormone (TSH), TRH and prolactin standards were obtained. Differences between Raman spectra profiles of control and Tx + TRH samples groups were found. These differences were confirmed by the linear discriminant analysis (LDA), which presents a good classification between groups. It is supposed that these differences are produced by the increment of TSH in the thyroidectomized rats.

Amino acid contents along the visual and equatorial axes of a pig lens by Raman spectroscopy.

Using near infrared Raman microspectroscopy with laser light of 830 nm, the distribution of amino acids along the visual and equatorial axes of a normal pig lens was studied. The classification of pig lens Raman spectra in these axes was performed using principal component analysis and linear discriminant analysis. The analysis of the scattered light selectively collected from point to point, along the visual axis, indicated that the tyrosine and tryptophan increases and then, at approximately 4 mm position, decreases. Moreover, in the equatorial plane, the nuclear part has the highest concentration of these amino acids. However, the phenylalanine content increases from anterior to posterior cortex of the lens as long as in the equatorial axis it slightly increases and then at approximately 2-2.3 mm position, decreases. The changes in amino acid conformation along the visual axis, similarly to the changes in protein conformation, may explain the refractive gradient of the lens.

Study of the protein distribution in the pig lens cross section by Raman spectroscopy.

The distribution of proteins in the cross section of a normal pig lens was studied by near-infrared Raman spectroscopy. The Raman spectra were measured in the visual and equatorial axes of this cross section and the protein peak intensities were determined. It was found that along each axis the protein intensities fluctuate. They have a considerable increment along the visual axis with the exception of the C-N bond peak intensities at 1087.2 cm(-1), which decrease, and along the equatorial axis the increment is slight. This increment in protein distribution along the visual axis is related with the refractive gradient of the lens. The classification of pig lens spectra in these axes was performed using principal component analysis (PCA) and linear discriminant analysis (LDA). Cross-validation shows an excellent group separation.