The article “Infrared detectors reach new lengths” by Gunapala and colleagues (December p35) presents an account of large area detectors based on novel sophisticated quantum processes. To an infrared spectroscopist there are surprising aspects. According to the text above the headline, “radiation can be detected at very long infrared wavelengths in a variety of applications not possible with existing detectors”. However, the longest wavelength mentioned is below 20μm. In the 1930s “very long infrared wavelengths” meant beyond 50μm. In the meantime continuous scanning has overlapped with the microwave region (~1000 μm or 1 mm).

1. The mouse Gardner lymphoma 6C3HED was grown in ascites fluid in a form sensitive to the action of L-asparaginase (line 1), in another form which was resistant to L-asparaginase (line 2) and in a third form with partial sensitivity to L-asparaginase (line 3). 2. The L-asparaginyl-tRNA synthetase activities of extracts of the tumour cells, cultured both in the mouse and in vitro, were determined. Two of the lines, 1 and 3, in early passage numbers, showed a derepression mechanism involving L-asparagine. Mutation occurred with these lines resulting in the L-asparaginyl-tRNA synthetase activity of all the tumour cell lines being the same. 3. Cells of line 1 had low L-asparagine synthetase activity, which was unchanged by altering the supply of L-asparagine in vitro. Cells of lines 2 and 3 exhibited L-asparagine synthetase activities, which changed with the supply of L-asparagine. 4. It is not certain that L-asparagine synthetase activity of L-asparaginase-sensitive cells is controlled by L-asparaginyl-tRNA acting as a corepressor.

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