Knowledge Bank

The infrared absorption spectrum of individual living muscle cells has been measured. In some regions of the spectrum the interfering absorption of intracellular $H2O$ was eliminated by measuring a percent transmission of the cells relative to an equal thickness of Ringer's solution. Some success has also been achieved in substituting $D2O$ for the intracellular water for recording of absorption bands obscured by $H2O$. The spectra of cells with substituted $D2O$ show differences evidently due to substitution of deuterium for hydrogen. Eight bands in the normal spectrum are sharply defined in the region between $6.5\mu$ and $10\mu$. Although most of these bands are alike in all cells studied, one band at $9.7\mu$ is variable. This band appears in the spectra of many muscles of an individual of the species studied, but is weak or missing in the spectra of other muscles of the same individual, or of the same muscles of different species. The variation is not explained. The muscle spectra are similar to that of myosin. It was found that glycogen or adenosine triphosphate were not contributing to the spectrum and that the spectrum of fresh tissue is not the same as that of dehydrated tissue.