Low-temperature study of photoinduced energy transfer from tryptophan residues of Escherichia coli alkaline phosphatase to bound terbium

Low-temperature phosphorescence (LTP) and zero-field-splitting (zfs) parameters of the lowest triplet state in zero magnetic field and triplet sublevel dynamics of tryptophan (Trp) residues in alkaline phosphatase (AP), metal-depleted AP (apoAP), and terbium-substituted AP (TbAP) are reported. The results are evaluated to find a plausible mechanism of energy transfer (ET) and TbAP at low temperature.