Journal of labelled compounds & radiopharmaceuticals vol:44 issue:4 pages:257-264
Ethylene bis-L-beta -homocysteine (L,L-EH) differs from ethylene bis-L-cysteine (L,L-EC) in having an extra methylene group between each pair of amine and carboxyl groups. The objective of this study was to determine the effect of the extra methylene groups on the characteristics of the complex of these compounds with technetium-99m during analysis by reversed phase HPLC and by electrophoresis at various pH values. Up to pH 5.5, Tc-99m-L,L-EH exhibits a substantially longer retention time during reversed phase HPLC than Tc-99m-L,L-EC, suggesting a more lipophilic character for Tc-99m-L,L-EH under these conditions. On the other hand, Tc-99m-L,L-EH clearly possesses a higher negative charge in the pH range 3-6.5 as shown by the markedly greater migration towards the anode in electrophoresis experiments. A rational explanation for these seemingly opposing observations can not yet be offered.