Dimitrov D
Mol Biol Rep. 1978 Feb 28;4(1):29-32. doi: 10.1007/BF00775177.
A low iodide concentration causes a positive difference band in the 250-260 mm UV range. The effect of Ca2+ changes the direction of difference spectra. The concentration dependence is explained by multistage interaction. The addition of EDTA the solution restores the positive band.