CLAUDIA CHILOM*, DOINA GĂZDARU*, MARIA IULIANA GRUIA**, IULIAN IONIŢĂ*** , CĂTĂLIN GEANTĂ*, AUREL POPESCU*
*Department of Electricity and Biophysics, Faculty of Physics, University of Bucharest
**“Alexandru Trestioreanu” Institute of Oncology, Bucharest
***Department of Optics, Plasma, and Lasers, Faculty of Physics, University of Bucharest
Abstract. The possible 3D alterations of proteins extracted from tumoral tissues are, ultimately, the consequence of the primary structure modifications, due to the alterations of some genes involved in synthesis of the tumor tissue proteins. The possible modifications of tumoral tissue proteins can be put in evidence by absorption and fluorescence spectroscopy methods, these modifications influencing the absorption and fluorescence behavior of the protein intrinsic fluorophores (i.e., aromatic amino acids). Absorption and fluorescence measurements were performed on biochemical samples obtained from mature Wistar rats bearing Walker tumours. Both tumour tissues as well as normal tissues from the hosts were harvested in order to extract the proteins. The absorption spectra were recorded in the ultraviolet and visible ranges, between 200 nm and 700 nm, while fluorescence excitation spectra were recorded in the spectral range 200 – 320 nm, at the Tryptophan (Trp) emission wavelength: λem = 348 nm. The fluorescence emission maxima, for all samples, are situated very close to that of the free molecules of Trp in water, this meaning that, the side chains of Trp are not shielded by the matrix of the proteins extracted from tumour tissues, this suggesting a slight denaturation of tumour proteins. The experimental data, judged by the absorption and fluorescence intensities, are confirming the findings that the tumor tissues have an increased metabolic activity as compared to the normal tissues. Therefore the protein synthesis occurring in tumoral tissues is more intense than in normal tissues. At the same time, the quality of tumoral tissue proteins seems to be different both in amino acid compositions and 3D protein folding as compared to proteins extracted from normal tissues.
Key words: absorption spectra, aromatic amino acids, fluorescence spectra, excitation spectra, tumor tissue proteins.