Perdeuterated all-trans beta-carotene imbedded in activated Cu-MCM-41 was examined by electron paramagnetic resonance (EPR) and electron spin-echo envelope modulation (ESEEM) spectroscopies. The EPR study showed that complexation and electron transfer between Cu2+ and deuterated beta-carotene occurs. The interaction was confirmed by detecting the spin-echo modulation of deuterium in the ESEEM spectra of Cull. Ratio analysis of ESEEM was used to determine the number of deuterons which interact with Cull and the distance between deuteron(s) and Cu2+. The bonding site of beta-carotene determined by ESEEM and pulse electron nuclear double resonance is the C15=C15 ' double bond.