Applications of Raman and Surface-Enhanced Raman Scattering to the Analysis of Eukaryotic Samples - Emerging Raman Applications and Techniques in Biomedical and Pharmaceutical Fields - page 74

Fig. 4.1. Raman spectra of pollen. The Raman spectra were excited with a wave-
length of 785 nm, laser power 18 mW (irradiance 1 . 8 × 10 6 W / cm 2 ), accumulation
time was 10 s. The spectra are averages from 5 to 10 individual pollen grains from
different samples (compare also Fig. 4.3)

Boston, USA). For the plots of the intensities as a function of spatial coor-
dinate, after baseline correction, the areas under the respective bands were
calculated. Figure 4.2 shows results of four examples of mapping experiments.
The plots of the intensities of selected characteristic bands as a function of
lateral position (so-called chemical maps) provide information on the amount
of the respective molecules or molecular groups in the different morphological
structures (Fig. 4.2). The band at 784 cm − 1 can be assigned to out-of-plane
deformation vibrational modes of the nucleobases cytosine, thymine and uracil
and serves as an indicator for the presence of nucleic acids. At 483 cm − 1 ,a
C-C-C deformation of carbohydrate polymers such as starch or pectin is
present in some of the spectra. To study the distribution of protein com-
pounds, we analysed characteristic signals of the amino acid phenylalanine

(1002 cm − 1 ring breathe) as well as of the protein amide I band 1651 cm − 1
that is brought about by vibrations of the protein backbones. The maximum
of the phenylalanine signal co-localizes with a maximum in protein content