Based on the spin-densities, differences between the electronic changes during reaction II are also minor between the two LPMOs: the spin densities (Table ) decrease significantly on oxygen in the OH group of the [CuOH] + moiety in 3, compared to O ox in [CuO] + (1), while the spin density increases on His1. The main increase occurs on the de-protonated C ϵ1 , suggesting that 3 is indeed a histidyl radical, coupled to a [CuOH] + moiety. .