ibly ▁bind ▁two ▁ ions ▁of ▁iron , ▁z inc , ▁co pper ▁or ▁other ▁met als . ▁The ▁binding ▁sites ▁are ▁local ized ▁in ▁each ▁of ▁the ▁two ▁protein ▁glob ules . ▁There , ▁each ▁ion ▁is ▁bond ed ▁with ▁six ▁lig ands : ▁four ▁from ▁the ▁pol ype pt ide ▁chain ▁( two ▁ty ros ine ▁resid ues , ▁one ▁hist id ine ▁resid ue ▁and ▁one ▁as part ic ▁acid ▁resid ue ) ▁and ▁two ▁from ▁carbon ate ▁or ▁b ic ar bon ate ▁ ions . ▁ ▁L act o fer rin ▁forms ▁re dd ish ▁complex ▁with ▁iron ; ▁its ▁aff inity ▁for ▁iron ▁is ▁ 3 0 0 ▁times ▁higher ▁than ▁that ▁of ▁transfer rin . ▁The ▁aff inity ▁increases ▁in ▁weak ly ▁acid ic ▁medium . ▁This ▁facil it ates ▁the ▁transfer ▁of ▁iron ▁from ▁transfer rin ▁to ▁la ct o fer rin ▁during ▁infl amm ations , ▁when ▁the ▁p H ▁of ▁t issues ▁decre ases ▁due ▁to ▁accum ulation ▁of ▁la ctic ▁and ▁other ▁ac ids . ▁The ▁s atur ated ▁iron ▁concentration ▁in ▁la ct o fer rin ▁in ▁human ▁milk ▁is ▁estimated ▁as ▁ 1 0 ▁to ▁ 3 0 % ▁( 1 0 0 % ▁corresponds ▁to ▁all ▁ ▁la ct o fer rin ▁mole cules ▁containing ▁ 2 ▁iron ▁atoms ). ▁It ▁is ▁demonstrated ▁that ▁la ct o fer rin ▁is ▁involved ▁not ▁only ▁in ▁the ▁transport ▁of ▁iron , ▁z inc ▁and ▁co pper , ▁but ▁also ▁in ▁the