Raman spectra of single cells of <i>Euglena</i> and <i>Chlamydomonas</i> have been examined with 514.5 nm excitation at various points within the cells. At every point, two strong bands, which are assignable to carotenoid, appeared at 1530 and 1159 cm<sup>-1</sup>. By the use of a Raman mapping system, the Raman intensity at 1530 cm<sup>-1</sup> has been plotted against the (x,y) coordinate representing a location within the cell. It has been shown that, for both algae examined, the eyespot has a prominently high carotenoid content, and a small amount of carotenoid is uniformly distributed among the chloroplast. The spatial resolution of the mapping system has been shown to be higher than 1 μm, and the Chlamydomonas eyespot has an elongated shape of 1 μm × 2 μm. By use of a polarizer, the carotenoid chains in the <i>Chlamydomonas</i> eyespot have been found to be aligned along its long axis, which is parallel to the body axis.
Yoshiko Kubo, Teruki Ikeda, Shi-Yuan Yang, and Masamichi Tsuboi, "Orientation of Carotenoid Molecules in the Eyespot of Alga: In Situ Polarized Resonance Raman Spectroscopy," Appl. Spectrosc. 54, 1114-1119 (2000)