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The Influence of the Interfacial Energy of Organic Solvents on the Photochemical Dimerization of Thymidylyl-(35)-thymidine.

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B
A
KO
(2) 26% m e s o
OH
16) 79%
wavelength and found that for equal radiation doses, the
yield of TDis greatest in water as solvent. When othersolvents
are used, the yields of T, decrease in the series glycerol>
formarnide>ethylene glycol> n-butanol>methanol>ethano1 >t-butanol.
Sinnnuglu and Abdulnur [4] recently showed that the interfacial energy of the solvent is of decisive importance, in
addition to van der W a d s forces, for the formation of doublestranded DNA. If the percentage of T, formed (determined
by measuring the decrease in extinction at 267 mp) in the
various solvents is plotted against the change in free energy
1Fo of the TpT molecule IS] during its conversion from a
form with mobile thymine bases into a form with stationary
adjacent bases (which is suitable for dimerization) in each
solvent, a linear relationship results [6].
~
AF('
Ikcal/molel
Solvent
Formation
of TD I %I
I
(3) 19% rac.
(7) 80%
The formation of acetone and p-methylcrotonaldehyde can
be explained by cleavage of 1,2-peroxo-linked structures (B)
[7]. Since the amount of acetone formed is 5 %, it can be
concluded that the ratio of C ~ H 1 4 0 2units in ( I ) with a 1,4peroxo structure (A) t o units with a 1,2-peroxo link (B) is
about 7: 1.
t-Butanol
Ethanol
Methanol
n-Butanol
Ethylene glycol
Formamide
Glycerol
Water
- 2.9
- 4.2
- 45
-
47
-11.3
-16.3
-16.5
-22.3
~5
5.5
6
7.5
19
21
33
35
This observation also explains the diminished thymine
dimerization in single-stranded DNA with ethylene glycol
as solvent [21. Moreover, it can be concluded that the double
helix of D N A is held together t o a large extent by van der
Waals forces (electrostatic and dispersion forces) and by
solvation forces and only to a lesser extent by hydrogen
bonds between the purine and pyrimidine bases 141.
Received: December 7th, 1964
[Z 8771705 IE]
German version: Angew. Chem. 77, 133 (1965)
Received: December loth, 1964 IZ 878/699 IE]
German version: Angew. Cbem. 77, 133 (1965)
[ I ] K . Griesbaum, A . A . Oswald, and W. Naegele, J. org. Chemistry 29, 1887 (1964).
[2] S. H. Harper, H. W. B. Reed, and R . A. Thompson, J. Sci.
Food. Agric. 2, 94 (1951).
131 Compound (3) is identical with a diepoxide prepared by
J. Salkind and S. Sabojew, Ber. dtsch. chem. Ges. 62,2169 (1929).
[4] The infrared spectra were taken on a Perkin-Elmer 421
spectrophotometer; CCI4 was used as solvent for the range
4000-650 cm-1 and CS2 for the range 850-650 cm-1.
[S] J. Bornstein, Analytic. Chem. 30, 544 (1958), where further
references are given.
161 0. Heuberger and N . L . Owen, J. chem. SOC.(London) 19.52,
910.
[7] W. Kern and J. Stallmann, Makromolekulare Chem. 7, 199
(1951); W . Kern and A . R. Heinz, ibid. 16, 81 (1955); C.T. Handy
and A. S. Rothrock, J. Amer. chem. SOC.80, 5306 (1958).
[ I ] A. Wacker, H. Dellweg, and D. Jacherts, J. molec. Biol. 4,
410 (1962).
[2] H . Dellweg and A. Wacker, Z. Naturforsch. 176, 821 (1962);
ibid., in the press.
[3] Prepared according to the procedure of P . T. Gilham and H. G.
Khorana, J. Amer. chem. SOC.80, 6212 (1958).
[4] 0. Sinanoglu and S. Abdulnur, Photochem. and Photobiol.,
in the press.
(51 0. Sinanoglu and S . Abdulnur, Feder. Proc., Supplement o n
Conference on CryobioIogy, in the press. We wish to thank Prof.
0. Sinanoglu and Dr. S . Abdulnur for making available their
experimental values prior to publication and for valuable
discussions.
(61 A grating monochromator of Messrs. Bausch and Lomb,
Rochester, was used for the irradiation experiments. Grating:
1200 linesimm. Light source: Osram HBO 200 W. Wavelength:
280 mp. Ultraviolet dose: lo5 erg/mm2. Concentration of TpT:
25 pg/mt. Room temperature.
The Influence of the Interfacial Energy of Organic
Solvents on the Photochemical Dimerization of
Thymidylyl-(3'- 5')-thymidine
By Prof. Dr. A Wacker and Dr. E. L.odemann
Institut fur therapeutische Biochemie
der Universitlt Frankfurt/Main (Germany)
Irradiation of single-stranded deoxyribonucleic acid (DNA)
with light of 254 m p wavelength in a q u e o u s soIution produces m o r e thymine dimer (T,) than analogous irradiation
of native double-stranded D N A [I]. However, when the
irradiation is carried out in 96-100"/, ethylene g l y c o l ,
single-stranded D N A gives l e s s T, than double-stranded
DNA does in aqueous solution [2].
We have irradiated the model compound thymidyiyl-(3' --f S')thymidine (TpT) [3] in various solvents with light of 280 m!*
I50
The Crystal Structure of a Phosphacyanine
By Dr. R. Allmann
Mineralogisches I nstit ut
der Universitlt MarburgILahn (Germany)
X-Ray analysis of N-ethyl-2-[(N-ethylbenzothiazolin-2-ylidene)phosphino]benzothiazolium perchlorate ( I ) , which was
recently prepared by Dimroth and Hoflnlnnn [I], gave results
that are in complete agreement with the constitution assumed.
Angew. Chenl. infernat. Edit. / Vol. 4 (1965) / No. 2
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thymidine, thymidylyl, interfacial, dimerization, organiz, solvents, energy, influence, photochemical
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