Tritium labelling and degradation studies of Dmt1‐endomorphin 2

Two tritiated derivatives of Dmt¹‐endomorphin 2 (Dmt¹‐EM2) were prepared by the catalytic tritiodehalogenation of 3′,5′‐diiodo‐Dmt¹‐EM2 and the saturation of ^3,4ΔPro²‐Dmt¹‐EM2, resulting in 3′,5′‐³H₂]Dmt¹‐EM2 and ³H₂]Pro²‐Dmt¹‐EM2 with specific activities of 2.88 TBq/mmol (77.8 Ci/mmol) and 1.95 TBq/mmol (52.8 Ci/mmol), respectively. 3′,5′‐Diiodo‐Dmt¹‐EM2 was synthesized by the chloramine T method from Dmt¹‐EM2. ^3,4ΔPro²‐Dmt¹‐EM2 was synthesized by using the Merrifield solid‐phase method. The distributions of the tritium in the labelled peptides were investigated by reversed‐phase high‐performance liquid chromatography after acidic hydrolysis. The stability of Dmt¹‐EM2 in a rat brain membrane homogenate was also determined. Copyright © 2007 John Wiley & Sons, Ltd.