Full resolution (JPEG) - On this page / på denna sida - II. The Protein Substances - II. Compound Proteins - B. Nucleoproteins - Cleavage Products of the Nucleoproteins - 3. Pyrimidine Bases
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
THYMINE. 195
varies with the dilution. This reaction which, as remarked above, is also
given by cytosine, depends upon the fact that dibromoxyhydrouraeil
us first formed, and from this, by the action of the barium hydroxide,
first isodialuric and then dialuric acid is produced, both of which give
the coloration. In regard to the preparation of uracil see Kossel and
Steudel.1
HN—CO
I I
Thymine, C5HGX2O2. = OC C.CH3 (5-methyluracil). This body,
HN—CH
which is identical with nucleosin obtained by Schmiedeberg from sal-
mo-nucleic acid, was first prepared by Kossel and Neumann from
thymus-nucleic acid, and then by other investigators, especially Levene
and Mandel, from other animal nucleic acids. Fischer and Roeder and
later Gerngross 2
have prepared it synthetically.
Thymine crystallizes in small leaves grouped in stellar or dendriform
clusters or, rarely, in short needles (Gulewitsch 3
). It deflagrates at
318° C. and melts at about 321° and sublimes. It is soluble with diffi-
culty in cold water, mere soluble in hot water, and insoluble in alcohol.
It behaves like uracil toward ammonia or baryta-water and silver nitrate.
Thymine is precipitated by phosphotungstic acid, especially when impure.
Bromine-water is decolorized by thymine, producing bromthymine.
For its detection we make use of the sublimation, the behavior toward
silver nitrate, and its elementary analysis.
Meters * has prepared compounds of pyrimidine bases with several metals
such as K, Na, Pb, Hg and he considers it incorrect to call the pyrimidine bodies
bases.
In regard to the methods of preparation see Kossel and Neumann
and W. Jones.
The purine and pyrimidine bodies stand in close chemical and phys-
iological relation to each other and for this reason the question has
been repeatedly raised whether the pyrimidine bases might not be formed,
at least in part, from the purine bases by the action of acids. Thus
far no conclusive investigations have been made supporting this view,
while on the contrary the investigations of Steudel 6
seem to contradict
such a view.
1
Zeitschr. f. physiol. Chem., 37.
:
Schmiedeberg, Arch. f. exp. Path. u. Pharm., 37; Kossel and Neumann, Ber.
d. d. chem. Gesellsch., 26 and 2"; Mandel and Levene, Zeitschr. f. physiol. Chem., 46
47, 49. 50; E. Fischer and Roeder, ibid., 34; Gerngross, ibid., 38.
3
Zeitsch:. f. physiol. Chem., 27.
4
Journ. of biol. Chem., 7.
6
Kossel and Neumann, 1. c, and W. Jones, Zeitschr. f. physiol. Chem., 29, 461.
6
Zeitschr. f. physiol. Chem., 51 and 53 (against Burian).
<< prev. page << föreg. sida << >> nästa sida >> next page >>
