Abstract #1853

Lowe M, Caravan P, Eldredge H, Zech S

The relaxivity of the gadolinium blood pool contrast agent MS-325 is found to be significantly higher when bound to human serum albumin (HSA) as compared to albumins from rabbit, rat or mouse. Various biophysical methods (NMR, relaxometry, luminescence) are employed with MS-325 surrogates where lanthanide ions Eu, Yb, or Dy have replaced the Gd. Exploiting the unique properties of the other lanthanides, molecular parameters influencing relaxivity are independently determined. While the molecular tumbling time and water hydration number do not change, water exchange is significantly slower when MS-325 is bound to rabbit albumin compared to HSA, resulting in decreased relaxivity.