Nucleic acids absorbance in Mid IR and its effect on diagnostic variates during cell division: a case study with lymphoblastic cells.

The differences in the absorbance in the mid infrared region (Mid IR) between normal and abnormal tissues have been shown to be a possible criterion for the detection of different forms of cancer. The present work aimed to study the effects of cell growth and DNA synthesis on the RNA/DNA ratio, which is a promising parameter for cancer diagnosis by inducing synthesis of DNA. Lymphoblastic cell lines were synchronized by methotrexate and harvested for Fourier transform infrared microscopy (FTIR-MSP) at 30-min interval after thymidine addition. The distribution of DNA in the cells/nuclei and variation of nuclear size was studied using the fluorescent dye propidium iodide (PI) and the nuclear volume was calculated from microscopy. We analyzed the ratio of RNA and DNA to quantify the relative amounts during the process by taking the ratios I(1121)/I(1020) (symmetric) and the I(1244)/I(1230) (antisymmetric) phosphate vibrations. The pattern of changes in the ratios overtime obtained in the symmetric and antisymmetric vibrations were similar though the magnitudes were different. Only a minor effect on the RNA/DNA ratio (due to nuclear volume changes) was observed. The effect due to the unfolding of DNA is greatly masked due to RNA absorbance. The effectiveness of this ratio may lie in the increased transcriptional levels in carcinogenic tissues rather than changes occurring due to unfolding and folding of DNA.