Some EPR signals in tumour tissue.

Area of Science:

• Biophysics
• Biochemistry
• Cancer Research

Background:

• Electron paramagnetic resonance (EPR) is a technique used to study paramagnetic species.
• Nitric oxide (NO)-haemoprotein complexes and ascorbyl free radicals are biologically relevant paramagnetic species.

Purpose of the Study:

• To investigate the presence and origin of paramagnetic species in normal and tumor tissues using EPR.
• To characterize EPR signals detected in rat and human samples.

Main Methods:

• Electron paramagnetic resonance (EPR) spectroscopy was applied to normal and tumor tissues from rats, and blood from normal and tumor-bearing rats, as well as normal human blood.
• Samples were analyzed at both low and room temperatures.

Main Results:

• A triplet EPR signal, attributed to a NO-haemoprotein complex, was observed in some tumor samples and decaying normal liver at low temperatures.
• A doublet EPR signal, assigned to the ascorbyl free radical (g ≈ 2.0054, splitting ≈ 1.80 G), was detected in all tumor samples and blood at room temperature, but not in other normal tissues.
• Model experiments indicated that ascorbyl radical appearance is associated with disturbances in the ascorbic acid/dehydroascorbic acid redox system, potentially involving autolysis rather than cell division.

Conclusions:

• EPR can detect distinct paramagnetic species in tumor tissues and blood.
• The ascorbyl free radical is a potential biomarker in tumors, linked to redox imbalance.
• Further research is warranted to explore the relationship between ascorbyl radicals and other paramagnetic species in cancer.