cciit. each of the X i 1 and of t h e radioactivity \vas precipitated; the precipitate contained t h e appropriate amounts of pyridoxal and amino acid. T~ 4 of ice-cold 0.020 d l ~ ~ p ~ previuusll~ \ ' ~ lcr!'3, tallized, was added 0.33 ml. of 0.060 111 Cu"L.a12, both sdutioils a t pH 7 . 2 and t h e solution coticetitrated quickly in the
cold t o about 0.3 i111. .Sfter holtliug 5 inin. at (I", the suspension was centrifuged 4 rnin. at high speed, and t h e crystals washed twice with water. I n a representative test, :32.84, of the copper and 33.1"; of the radioactivity had precipitated'
-1l-s.XRBOK,
~~ICIHGAS
[ C O h T K I B U i . I O X F R O 3 1 T H E C H E M I C A L L A B O R A T O R Y OF ~ ~ O ~ l ' l I ~ ~ ~ L-SIVEKSITTJ E S T E K ~ ~
The Hydrogen Ion Equilibria of a Single Group Attached to Serum Albumin: Some Implications as to the Surface Characteristics of Protein Molecules
nr.
BY IRVISG KLOTZ AND JANET & ~ Y E R S RECEIVED ~IAKC 18, H 19ST
__ The ionization equilibria of the dimethylamino group of ( CH3j2X-=-S-S-
