1742
C‘UMMUNICATION TO THE EDITOR
Selenium Tetracysteine To an aqueous solution of 0.01 mole of cysteine hydrochloride an aqueous solution of 0.0025 mole of sodium selenite was added. On cooling, a white granular material separated, It was removed by filtration, washed with water, and recrystallized from hot water. The yield was 8045% of the theoretical amount. Under the microscope, the crystals had the form of clusters of small rods. The iubstance began t o darken a t l i i 4 - l t i 5 O and decomposed a t 195-196’. The analysis of the substance indicated that i t was apparently identical with selenium tetracystrine.
Found Calcd. for Se(SC3OnNHa)a
C H 25.41 4 38
9.87
14.00
2 5 . 3 4.29
li).Ol
14.1G
K
Sc
S:Sr 4:l
VOl. 64
I t readily decomposes in cold diiute alkali yielding elementary selenium. An aqueous solution of selenium tetracysteine gives a negative test for free SH- with nitroprusside and ammonia. On treatment with sodium cyanide, the nitroprusside test becomes positive. The ready reactivity of the selenite toward cysteine is analogous to that of arsenious acid toward cysteine t o give arsenious tricysteine. The latter compound was prepared by Johnson and Voegtlinl using arsenious trichloride. We found in unpublished studies that arsenious acid also reacts with cysteine to give the tricvstrine in yields. The cysteine derivatives of selenium and arsenic are of interest in connection with the selenium poisoning in animals, and the well-known inactivation of certain enzymes by arsenious acid and the selenite. _ I _ _
Selenium tetracysteine is moderately soluble in cold water, readily soluble in hot water. I t is soluble in dilute mineral acids, but decomposes on heating the acid solution to yield what appears to be elementary selenium (brick-red i n color, characteristic odor, gives intense codeine test‘’
SOME X-RAY DIFRRACTION MEASUREMENTS ON BIOTIN
(1) J. M, Johnson and C . Voegtlin, J . Biol. Chem., 89, 27 (1930).
VANDERBILTUNIVERSITY SCHOOL O F MEDICINE DEPARTMENT OF BIOCHEMISTRY ?;ASIIVILLE, TENNESSEE JAKOB A . STEKOI. RECEIVED M A Y 4, 1942
axes were made as well as “a” axis Weissenberg films of the equator, first and second layers. The Sir : only systematic absences found were the extincAbout one milligram of free biotin, C I ~ H I G O ~ N ~tions S , of the odd orders of the (hOO), (OkO), and was made available to the writer throagh the (000 reflections I‘he space group is therefore courtesy of Dr. Vincent du Vigneaud, of the Cor- P21212,. ‘l‘his space group has four general posine11 Medical School. Repeated micro-recrystal- tions. I’he lengths of the ( 1 , b arid 1‘ axes were found to lizations produced a few crystals largc enough for be .i.?.i, It).;
