High-wavenumber region

Fig. 6.10. In vivo multiplex CARS microspectroscopy of a NIH 3T3-L1 fibroblast cell in the high-wavenumber region where C-H stretch vibrations reside. A CARS image revealing the intracellular distribution of constituents with high densities of lipids, such as the membrane envelope of the nucleus and intracellular lipid droplet (LD) organelles. Typical MEM-reconstructed Raman spectra taken for (B) a single LD organelle that is indicated by the arrow in A, (C) the nucleus, and (D) the cytoplasm. The spectrum exposure time was 0.3 s...

Absorptions for bonds to hydrogen always occur on the left side of the spectrum (the high wavenumber region). H has so little mass that H-Z bonds (where Z = C, O, and N) vibrate at high frequencies. 

Because of the reliability of the high-wavenumber region, we always begin the interpretation of a spectrum at this end. 

Water in skin samples can be characterized by NIR-FT-Raman spectroscopy. The high wavenumber region from 2500 to 3500 cm measures the total amount of water. A broad band with a maximum at about 180 cm gives an estimate of the presence of water not bound to biomolecules, free water with a bulk-like liquid water structure. In the low-wavenumber region... 

Figure 12.4. Spectrum of an undeformed 300-pm PET film in the high-wavenumber region and the dichroic difference spectra recorded with a PEM at the end of the deformation and after 30 and 300 s of relaxation. (Reproduced from [3], by permission of the Society for Applied Spectroscopy copyright 2002.)...

The development of VCD as a peptide conformational probe proceeded in a manner similar to the one followed earlier by researchers in CD spectroscopy [38], Homo-polyamino acids, such as poly-L-Tyr or poly-L-Lys, for which the secondary structure is well known and can be varied as a function of solvent acidity, were studied via VCD, and distinct results for the established conformations were observed. These results are summarized in Figures 4 and 5. In poly-L-Tyr [41], for example, the a-heli-cal conformation exhibits a distinct, sharp and near-conservative positive / negative couplet in the amide I region. In the context of this discussion, "conservative couplet" implies equal positive and negative VCD intensities, and a description of positive / negative couplet always implies low to high wavenumber. The a-helical conformation is assumed by poly-L-Tyr in acidified DMSO solution (80% 20% by volume of DMSO... 

Intramolecular effects can be detected in the near infrared or high-frequency region (P-1000 cm ). Intermolecular effects are seen in the far infrared or low-frequency region (P down to 100 cm ). Early measurements showed that ions can cause new peaks to arise that are at distinctly higher wavenumbers than those in pure water. The explanation proposed is that some of the hydrogen bonds present in pure... 

Modes at lower wavenumbers give more intense bands than modes in the high-frequency region. This makes INS useful for identifying vibrations in the energy range below 600 cm which is often difficult to obtain by optical spectroscopies. 

Higher wavenumber regions of difference RR spectrum (low minus high irradiance conditions) of D1/D2 particles (T 15 K)... 

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