Ion association dynamics in aqueous solutions of sulfate salts as studied by Raman band shape analysis

A new perspective is shown on the interaction between the sulfate ion and its counter cation in aqueous solutions. We propose the dynamic exchange model of ion association instead of the conventional static equilibrium model. The concentration dependence of the Raman band shape of the totally symmetric (a(1)) SO stretch mode of the sulfate ion is investigated systematically for four sulfate ions, MgSO(4), (NH(4))(2)SO(4), K(2)SO(4), and Li(2)SO(4). The concentration dependence of the a(1) Raman band shape in the MgSO(4) system is successfully reproduced by the analysis based on the dynamic exchange model. As a result, quantitative information about the extremely dynamic nature of the ion association has been obtained: the mean time between associations is a few picoseconds and the mean lifetime of association is several hundred femtoseconds.

Molecular-Level Investigation of the Structure, Transformation, and Bioactivity of Single Living Fission Yeast Cells by Time- and Space-Resolved Raman Spectroscopy

The structure, transformation, and bioactivity of single living Schizosaccharomyces pombe cells at the molecular level have been studied in vivo by time- and space-resolved Raman spectroscopy. A time resolution of 100 s and a space resolution of 250 nm have been achieved with the use of a confocal Raman microspectrometer. The space-resolved Raman spectra of living S. pombe cells at different cell cycle stages were recorded in an effort to elucidate the molecular compositions of organelles, including nuclei, cytoplasm, mitochondria, and septa. The time- and space-resolved measurement of the central part of a dividing yeast cell showed continuous spectral evolution from that of the nucleus to those of the cytoplasm and mitochondria and finally to that of the septum, in accordance with the transformation during the cell cycle. A strong Raman band was observed at 1602 cm(-)(1) only when cells were under good nutrient conditions. The effect of a respiration inhibitor, KCN, on a living yeast cell was studied by measuring the Raman spectra of its mitochondria. A sudden disappearance of the 1602 cm(-)(1) band followed by the change in the shape and intensity of the phospholipid bands was observed, indicating a strong relationship between the cell activity and the intensity of this band. We therefore call this band "the Raman spectroscopic signature of life". The Raman mapping of a living yeast cell was also carried out. Not only the distributions of molecular species but also those of active mitochondria in the cell were successfully visualized in vivo.

Characterization of a supercontinuum generated from a photonic crystal fiber and its application to coherent Raman spectroscopy

The temporal and spectral profiles of supercontinuum radiation generated from a photonic crystal fiber are evaluated with a polarization-gate frequency-resolved optical gating technique. The supercontinuum is then applied to coherent inverse Raman spectroscopy. A stimulated Raman signal of cyclohexane is observed as an induced absorption signal with an instantaneous response. The Raman signal has a peak at a slight negative delay time, which is explained by perturbed Raman-induced coherence.

The diagnosis of lung cancer using 1064-nm excited near-infrared multichannel Raman spectroscopy

PURPOSE

Raman spectroscopy is based on Raman scattering of light from molecules. Because the wavelength of Raman scattered light depends on molecular composition, Raman spectra provide highly useful information about molecular composition. It has already been shown that Raman spectroscopy is potentially useful for the clinical diagnosis of malignant tumors. However, this technique had never been applied to the diagnosis of lung cancers, primarily because of interference from the strong fluorescence emitted from lung tissues. Our purpose was to examine the effectiveness of near-infrared Raman spectroscopy for the diagnosis of lung cancers.

METHODS

We constructed a new near-infrared multichannel Raman system that is capable of measuring high signal-to-noise ratio, fluorescence-free Raman spectra of lung tissues within a measurement time of 1 second. Using this system, we collected a total of 210 Raman spectra from cancerous and non-cancerous lung tissues and analyzed these spectra by a least-squares fitting procedure for cancer diagnosis.

RESULTS

The resultant sensitivity of cancer prediction was as high as 91%, with 97% specificity and an error margin of p<0.0001 according to Fisher's exact test.

CONCLUSIONS

A method of diagnosing lung cancer efficiently and objectively using Raman spectroscopy has thus been established.