Raman anemometry, a method for component-selective velocity measurements of particles in a flow

An anemometer for the measurement of the velocity of particles of different substances in a flow, separate and apart from that of the flow itself, is described. The substances are distinguished by Raman scattering. The velocity is obtained by relating the autocorrelated scattering signal to the known laser beam profile

A Raman spectroscopic study of the interaction between nucleotides and the DNA binding protein gp32 of bacteriophage T4

Raman spectra of the bacteriophage T4 denaturing protein gp32, its complex with the polynucleotides poly(rA), poly(dA), poly(dT), poly(rU), and poly(rC), and with the oligonucleotides (dA)8 and (dA)2, were recorded and interpreted. According to an analysis of the gp32 spectra with the reference intensity profiles of Alix and co-workers [M. Berjot, L. Marx, and A.J.P. Alix (1985) J. Ramanspectrosc., submitted; A.J.P. Alix, M. Berjot, and J. Marx (1985) in Spectroscopy of Biological Molecules, A. J. P. Alix, L. Bernard, and M. Manfait, Eds., pp. 149-154], 1 gp32 contains ≈ 45% helix, ≈ 40% β-sheet, and 15% undefined structure. Aggregation of gp32 at concentrations higher than 40 mg/mL leads to a coordination of the phenolic OH groups of 4-6 tyrosines and of all the sulfhydryl (SH) groups present in the protein with the COO- groups of protein. The latter coordination persists even at concentrations as low as 1 mg/mL. In polynucleotide-protein complexes the nucleotide shields the 4-6 tyrosine residues from coordination by the COO- groups even at high protein concentration. The presence of the nucleotide causes no shielding of the SH groups. With Raman difference spectroscopy it is shown that binding of the protein to a single-stranded nucleotide involves both tyrosine and trytophan residues. A change in the secondary structure of the protein upon binding is observed. In the complex, gp32 contains more -sheet structure than when uncomplexed. A comparison of the spectra of complexed poly(rA) and poly(dA) with the spectra of their solution conformations at 15°C reveals that in both polynucleotides the phosphodiester vibration changes upon complex formation in the same way as upon a transition from a regular to a more disordered conformation. Distortion of the phosphate-sugar-base conformation occurs upon complex formation, so that the spectra of poly(rA) and poly(dA) are more alike in the complex than they are in the free polynucleotides. The decrease in intensity of the Raman bands at 1304 cm-1 in poly(rA), at 1230 cm-1 in poly(rU), and at 1240 and 1378 cm-1 of poly(dT) may be indicative of increased stacking interactions in the complex. No influence of the nucleotide chain length upon the Raman spectrum of gp322 in the complex was detected. Both the nucleotide lines and the protein lines in the spectrum of a complex are identical in poly(dA) and (dA)8

Age-related changes in local water and protein content of human eye lenses measured by Raman microspectroscopy

The Raman microspectroscopic method was used to determine the local water and protein content in human lenses. In 18 lenses of varying age position-defined water/protein content measurements were carried out along the visual and the equatorial axis.\ud \ud A main characteristic of the human lens is its constant and relatively low protein content. In addition this constant nuclear value is reached within a short distance from the capsular surface. For statistical analysis of age-related changes the data points in individual lenses were piecewise linearized. (1) The mean nuclear water content was calculated from the data points in the inner 80% of the visual axis. (2) The steep drop in water content was linearized using a least-squares linear regression approach. The distance between lenticular surface and the intersection of the regression line with the line representing the nuclear mean was denominated as surface layer width.\ud \ud It proved that: (i) the mean nuclear water content significantly increased with age, (ii) the width of the surface layer was age independent in the anterior and posterior poles of the visual axis, and (iii) in the equatorial axis the surface layer width significantly decreased with age.\ud \ud Seven human lenses with small opaque spots were also investigated. The opaque spots proved to have a normal-for-site water content and some of them were flanked at their capsular side by a zone with a high-for-site water content.\ud \ud The correlation between protein content and refractive index and the observed decrease in nuclear protein content in aging human lenses can be taken as strong evidence that upon aging the refractive index of a major part of the human lens is reduced. The implications of this decrease is discussed with the respect to the problem known as the lens Paradox, i.e. the discrepancy between the theoretically expected age-related loss of far vision due to changes in lens curvature and axial position in the eye and the actually observed loss in near vision upon age

Possibilities and limitations of off-resonance polarization sensitive cars of short chain proteins

Polarization sensitive CARS in the absence of resonance enhancement is applied to a short chain protein. The minimum concentration to record polarization sensitive CARS spectra of protein solutions is estimated to be 10 mg/ml. The effects limiting the protein concentration are discussed and regarded from an experimental point of view. Signal strength and line parameters of polarization sensitive CARS spectra of the short chain protein Lysyl-Tryptophyl-Lysine are compared with those of a normal Raman spectrum

Horizons of hermeneutics: Intercultural hermeneutics in a globalizing world

Starting from the often-used metaphor of the "horizon of experience" this article discusses three different types of intercultural hermeneutics, which respectively conceive hermeneutic interpretation as a widening of horizons, a fusion of horizons, and a dissemination of horizons. It is argued that these subsequent stages in the history of hermeneutics have their origin in-but are not fully restricted to-respectively premodern, modern and postmodern stages of globalization. Taking some striking moments of the encounter between Western and Chinese language and philosophy as example, the particular merits and flaws of these three types of hermeneutics are being discussed. The claim defended is that although these different types of hermeneutics are mutually exclusive from a theoretical point of view, as interpreting beings in the current era we depend on each of these distinct hermeneutic practices and cannot avoid living them simultaneously

The MCGA (multiple cubic gradient approximation) method for the analysis of Raman spectra

An easily accessible interactive method for the analysis of Raman spectra consisting of many overlapping peaks is presented. A combination of a three- or four-dimensional grid and gradient searching is applied. The method can handle spectra with up to about 50 lines, based on a broad background. Analytical and user-defined or tabulated basic functions can be included. The merits of the method are discussed with both artificial and real spectra

Surface-enhanced Raman spectroscopy of DNA bases

A Raman microprobe has been used to measure the surface-enhanced Raman spectra of adenine, guanine, cytosine and thymine. Comparison of the SERS spectrum with solution spectra shows that some line positions are not influenced by the adsorption process while others show large shifts. In the SERS spectrum new lines, not visible in the solution spectrum, appear while some lines visible in the solution spectrum are not enhanced to a detectable level and are therefore not seen in SERS. The relative intensities are changed owing to an apparently vibration-dependent enhancement factor. A line-broadening effect occurs for most lines except carbonyl stretching vibrations in cytosine and thymine. All SERS spectra show increased contributions of bending vibrations and side-chain groups. In particular, amino group vibrations in adenine and cytosine are clearly visible. Comparison of the shape and intensity of the carbonyl stretching vibrations in cytosine, thymine and guanine show important differences. It is hypothesized that these differences indicate differences in the orientation of these groups with respect to the surface

Non-resonant background suppression in preresonance CARS spectra of flavin adenine dinucleotide: Demonstration of a background suppression technique using phase mismatching and comparison with the polarization-sensitive CARS technique

Polarization-sensitive CARS spectra of a 5.7 × 10-3 mol dm-3 flavin adenine dinucleotide (FAD) solution were recorded under preresonance conditions at a pump wavelength of 532 nm. The depolarization ratios of the vibrations are shown to be close to the depolarization ratio of the non-resonant background. This results in a severe reduction of the vibration resonant signal (a factor of 700-900) in the polarization CARS spectrum, and a poor improvement in the ratio of the resonant signal and the non-resonant background (<10). \ud In this context, a non-resonant background suppression technique is discussed and demonstrated for 5.7 × 10-3 and 1.4 × 10-3 mol dm-3 FAD solutions excited at 532 nm; the non-resonant susceptibility of the walls of the cuvette, which contains the FAD solution, is used to compensate the non-resonant signal contribution of the solution. An improvement in the signal-to-noise ratio of ca. 50 is achieved at the cost of a factor of 30 in the resonant signal strength. Lorentzian-shaped spectral bands are obtained, facilitating the determination of band position, width and intensity. Line shape parameters and depolarization ratios for FAD are extracted from the presented spectra by curve fitting. The signal strength and background suppression achieved with these techniques and the resonance CARS technique (at a pump wavelength of 480 nm) are compared and discussed

Two small-volume electrochemical cells for the measurement of surface enhanced Raman scattering

Two electrochemical cells, for performing surface enhanced Raman scattering (SERS), with submillilitre volumes are presented. One of the cells is especially developed for use in a Raman microspectrometer. The smallest cell uses only 80 mu l of sample. SER measurements are performed on 2*10-3 M adenine

Description and performance of a highly sensitive confocal Raman microspectrometer

A confocal Raman microspectrometer was developed for the study of small biological objects such as single living cells and metaphase and polytene chromosomes. It employs a confocal detection scheme, well known from confocal fluorescence microscopes, in order to avoid signal contributions from the environment of the samples. The resolution is 0.45 ± 0.05 m in the lateral direction and 1.3 ± 0.1 m in the axial direction. The laser excitation wavelength is 660 nm. At this wavelength biological samples do not degrade in the laser radiation as was the case when laser radiation of 514.5 nm was used. The signal throughput from the sample position to the detector was optimized to the extent that in the spectral region around a 1000 cm-1 Raman shift 15% of the Raman scattered light collected by the microscope objective is detected. For signal detection a liquid nitrogen-cooled slow-scan CCD camera is used. Laser powers of 5-10 mW suffice to obtain high-quality Raman spectra, with signal integration times of the order of minutes. As an example, spectra obtained from the nucleus and the cytoplasm of an intact human lymphocyte are shown