| Popis: |
Three paramagnetic Co(II) macrocyclic complexes containing 2-hydroxypropyl pendant groups, 1,1’,1”,1”’-(1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetrayl)tetrakis(propan-2-ol) ([Co(L1)](2+), 1,1’-(4,11-dibenzyl-1,4,8,11-tetraazacyclotetradecane-1,8-diyl)bis(propan-2-ol) ([Co(L2)](2+)(, and 1,1’-(4,11-dibenzyl-1,4,8,11-tetraazacyclotetradecane-1,8-diyl)bis(octadecan-2-ol) ([Co(L3)](2+)( were synthesized to prepare transition metal liposomal chemical exchange saturation transfer (lipoCEST) agents. In solution, )[Co(L1)](2+)( forms two isomers as shown by (1)H NMR spectroscopy. X-ray crystallographic studies show one isomer with 1,8-pendants in cis-configuration and a second isomer with 1,4-pendants in trans-configuration. The [Co(L2)](2+) complex has 1,8-pendants in a cis-configuration. Remarkably, the paramagnetic induced shift of water (1)H NMR resonances in the presence of the [Co(L1)](2+) complex is as large as that observed for one of the most effective Ln(III) water proton shift agents. Incorporation of [Co(L1)](2+) into the liposome aqueous core, followed by dialysis against a solution of 300 mOsm/L produces a CEST peak at 3.5 ppm. Incorporation of the amphiphilic [Co(L3)](2+) complex into the liposome bilayer produces a more highly shifted CEST peak at −13 ppm. Taken together, these data demonstrate the feasibility of preparing Co(II) lipoCEST agents. |
