As used herein, a paramagnetic metal ion is selected from a group consisting of Gd, Mn, {HEAD ~ Mn}, Fe, Cr, Cu, Co, Ni, Dy, Tb, Ho, Er, Eu, and {TAIL ~ Nd} 
As used herein , a paramagnetic metal ion is selected from a group consisting of Gd , Mn , { HEAD ~ Mn } , Fe , Cr , Cu , Co , Ni , Dy , Tb , Ho , Er , Eu , and { TAIL ~ Nd }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL