Proton relaxation of malignant and embryonic mouse cells

The 90 MHz proton relaxation of malignant and embryonic mouse cells was investigated in 0.8% heavy-water solutions of NaCl. Two relaxation times appear in both cases. One of them, which is considerably longer (T₁=T₂=3 sec), is close to relaxation times in pure water. It is probably due to protons from a sphere of action around the cell. This relaxation time depends on the nature and constitution of surrounding medium and hence cannot be determined quite exactly. The second relaxation time has all the characteristics of bound water with a limited diffusion and is probably due to the cell itself. The typical inequality T₁>T₂ has also been observed with T₁ about 300 ms and T₂=0.3 ms. In the temperature range 4-37°C both relaxation times are almost temperature independent. The coefficient of self-diffusion (determined by the pulse gradient method) is lower by one order of magnitude than that in free water. The relaxation mechanism is characterized by the secondary spin-spin scalar interaction and a wide distribution of correlation times, which is typical of water in channels of both organic and inorganic natures. In the temperature range 4-37°C malignant cells show a T₁ value higher by about 30% than that for normal cells, which can be used for their identification.