tokens: The evidence in support of this was derived from the fact that the affinity or interaction between the two subunits was impaired as indicated by the first order rate constant of hCG alpha 1 beta ( km = 4 . 1 x 10 ( - 2 ) min - 1 ) at pH 3 . 0 at 23 degrees C which is one order of magnitude greater relative to rehCG ( kw = 4 . 6 x 10 ( - 3 ) min - 1 ) .