the calculated electron distributions are tested by comparison of the predicted hyperfine fields at proton sites with experimental data in both the ions and most important , by their ability to explain the observed trend in the hyperfine fields in going from the cation bacteriopheophytin+ alpha to the anion , a trend that is similar in many respects to the corresponding observed trend for the bacteriochlorophyll alpha cation and anion .
C0022023
ions
C0003075
anion