Spectroscopy, weak hydrogen bond detection

Presumably this is a reasonable model for a peptide bond, and formation of the dimer and higher polymers can be detected easily by examination of the N-H stretching frequency by ir spectroscopy. The degree of association of N-methylacetamide is affected by the solvent (Table II). In aqueous solutions die association is extremely weak, with positive values for the unitary free energy change associated with hydrogen bond formation. That is, monofunctional hydrogen bonds in aqueous solution do not appear to be stable (15). 

Leaver et al. [25] used Raman spectroscopy to determine the presence of a UV stabilizer, Tinuvin P (Ciba-Geigy), which is absorbed into the wool. Because wool is a weak scatterer, they were able to detect the additive with a good signal-to-noise ratio. They hoped to be able to determine the extent of hydrogen-bonding of the UV stabilizer to the polar side groups of wool. These hydrogen bonds are believed to reduce the effectiveness of the UV stabilizer. 

IR spectroscopy is a valuable complementary technique to Raman spectroscopy. Synchrotron based IR micro-spectroscopy is a new technique that shows promising perspectives for studies of skin and human cells (28). At the Max-Lab synchrotron beam line in Lund, Sweden an IR microscope is now being installed (29). This instrument will allow IR-spectra to be recorded with a bolometer detector down to 50 cm (around 1,5 THz). In the R(v)-representation of the low-wavenumber Raman spectrum it is very difficult to quantify the amount of free water because the water band at 180 cm is weak compared to the protein hydrogen bond band at 110-120 cm" Hopefully the water band is relatively more intense in the IR spectrum allowing a detection of the free water at low concentrations. 

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