Phosphodiester Stretching Bands in the Infrared Spectra of Human Tissues and Cultured Cells

Abstract

Methodology has been developed recently in our Ottawa laboratory to obtain infrared spectra of intact biological tissues and whole cells with extremely high signal-to-noise ratio. This development has allowed us to evaluate the structural properties of biomolecules in tissue sections and exfoliated cells of human neoplasms by monitoring their infrared spectra (Refs. 2 and 3 and research submitted for publication). During this work we found that several changes in the infrared spectra of malignant tissues and cells are common to all cancers which we studied, including those of the colon, stomach, esophagus, skin, liver, cervix, and vagina (Refs. 2 and 3 and research submitted for publication). It is important to know the structural origin of these spectral changes, since they may reflect a step of a shared pathway in carcinogenesis. The most striking changes in the spectra that are common to various malignant tissues and cells are observed in the symmetric (νsPO2−) and asymmetric (νasPO2−) stretching bands of phosphodiester groups. These results suggest that in all cancerous tissues and cells studied to date most PO2− groups become hydrogen bonded and that the intermolecular packing among neighboring PO2− groups becomes closer. (Refs. 2 and 3 and research submitted for publication). Indirect evidence, discussed later, pointed to nucleic acids as the molecules mainly responsible for the observed changes in the νsPO2− and νasPO2− bands. Since any information concerning structural changes in nucleic acids associated with malignancy is potentially significant for our understanding of cancer, we sought to confirm the molecular origin of the phosphodiester stretching modes in the infrared spectra of tissues and whole cells. We therefore investigated the infrared spectra of human malignant colon tissues, cultured human colon adenocarcinoma cells, and the nuclei, DNA, RNA, and lipids isolated from the cultured adenocarcinoma cells. Moreover, the correlation of the intensities of the νas,PO2− and ,νsPO2− bands in the infrared spectra of human thymus and muscle tissues with their relative concentrations of nucleic acids in the cells has been studied.