Laser-Raman spectroscopy of living cells

Investigations into the laser—Raman shift spectra of bacterial and mammalian cells have revealed that many Raman lines observed at 4–6 K, do not appear in the spectra of cells held at 300 K. At 300 K, Raman activity, at set frequencies, is observed only when the cells are metabolically active; however, the actual live cell spectrum, between 0 and 3400 cm^?1, has been found to alter in a specific way with time as the cells' progress through their life cycles. Lines above 300 cm^?1, from in vivo Raman active states, appear to shift to higher wave numbers whereas those below 300 cm^?1 seem to shift to lower ones. The transient nature of many shift lines observed and the intensity of them when present in the spectrum indicates that, in vivo, a metabolically induced condensation of closely related states occurs at a set time in the life of a living cell. In addition, the calculated ratio between the intensities of Stokes and anti-Stokes lines observed suggests that the metabolically induced “collective” Raman active states are produced, in vivo, by non thermal means. It appears, therefore, that the energetics of the well established cell “time clock” may be studied by laser—Raman spectroscopy; moreover, Raman spectroscopy may yield a new type of information regarding the physics of such biological phenomena as nutrition, virus infection and oncogenesis.