Mechanistic Study and Application to the Photorepair of cis,syn-Cyclobutane Thymine Photodimer
Although it was not possible to quantify the Zn2+ concen-
trations in solution and living cells, we have discovered the
photorepair of TACHTUNGTRENNUNG[c,s]T 24 utilizing the photocleavage of 9,
25.0ꢁ0.18C. For fluorescence titrations, a sample solution in a 1.0 cm
quartz cuvette was excited at the isosbestic point determined by UV ti-
tration. The obtained data for the UV titrations (changes in e values at a
given wavelength) and fluorescence titrations (increases in fluorescence
emission intensity at a given wavelength) were analyzed for apparent
complexation constants, Kapp, using the Bind Works program (Calorime-
try Sciences Corp). Quantum yields were determined by comparison of
the integrated corrected emission spectrum of standard quinine sulfate,
whose quantum yield (F) in 0.1m H2SO4 was assumed to be 0.55 (excita-
tion at 366 nm).[45]
while the Zn2+ complex of N-(1-naphthylsulfonyl)cyclen 11
induced photoreversion only to a negligible extent, support-
ing the view that the mechanisms of photolysis of 9 and 11
are somewhat different. Very interestingly, the photolysis of
a catalytic amount of 9 (ZnL2) induced the nearly complete
photoreversion of T
19 functions as a catalyst in the cycloreversion of TAHCTUNGTRENNUNG
These results will promise to open new routes to the design
of photoreactions of metal complexes.
ACHTUNGTRENNUNG
Potentiometric pH titrations: The preparation of test solutions and the
method of calibrating the electrode system (Potentiometric Automatic Ti-
trator AT-400 and Auto Piston Buret APB-410, Kyoto Electronics Manu-
facturing (KEM), Co. Ltd. with KEM glass Electrode C-117) have been
described earlier.[15–18,22,32,33] All the test solutions (50 mL) were kept
under an argon (>99.999% purity) atmosphere. The potentiometric pH
titrations were performed with I=0.10 (NaNO3) at 25.0ꢁ0.18C, and at
least two independent titrations were performed (0.1m aq. NaOH was
used as a base). Deprotonation constants of Zn2+-bound water K’2 (=
[HOꢀ-bound species][H+]/[H2O-bound species]) were determined by
means of the BEST program.[23] All the sigma fit values defined in the
Experimental Section
General information: All reagents and solvents were purchased at the
highest commercial quality and were used without further purification.
ZnSO4·7H2O, 3CdSO4·8H2O, CuSO4·5H2O, FeSO4·7H2O, HgCl2, Mn-
ACHTUNGTRENNUNG
program were smaller than 0.1. The KW (=aH+·aOHꢀ), K’W (=[H+][OHꢀ])
and fH+ values used at 258C are 10ꢀ14.00, 10ꢀ13.79, and 0.825. The corre-
sponding mixed constants, K2 (=[HOꢀ-bound species]aH+/[H2O-bound
species]), were derived using [H+]=aH+/fH+. The species distribution
values (%) against pH (=ꢀlog[H+]+0.084) were obtained using the SPE
program.[23]
ACHTUNGTRENNUNG
G
ACHTUNGTRENNUNG
drich Chemical Co. Anhydrous acetonitrile (CH3CN) was obtained by
distillation from calcium hydride. All aqueous solutions were prepared
using deionized and distilled water. Buffer solutions (CAPS, pH 12.0,
11.5, 11.0, 10.5, and 10.0; CHES, pH 9.5 and 9.0; TAPS, pH 8.4 and 8.0;
HEPES, pH 7.8, 7.6, 7.4, and 7.0; MES, pH 6.5 and 6.0) were used and
the ionic strengths were adjusted with NaNO3. The Goodꢁs buffer re-
agents (Dojindo) were commercially available: MOPS (3-(N-morpholi-
no)propanesulfonic acid, pKa =7.2), HEPES (N-(2-hydroxyethyl)pipera-
zine-N’-2-ethanesulfonic acid, pKa =7.5), EPPS (3-(4-(2-hydroxyethyl)-1-
piperazinyl)propanesulfonic acid, pKa =8.0), TAPS (N-(tris(hydroxyme-
thyl)methylamino)-3-propanesulfonic acid, pKa =8.4), CHES (2-(cyclo-
hexylamino)ethanesulfonic acid, pKa =9.5), CAPS (3-(cyclohexylamino)-
propanesulfonic acid, pKa =10.4). Melting points were measured on a
Bꢄchi 510 Melting Point Apparatus and are uncorrected. UV spectra
were recorded on a Hitachi U-3500 spectrophotometer and JASCO UV/
VIS spectrophotometer V-550, and fluorescence (excitation and emis-
sion) spectra were recorded on a Hitachi F-4500 fluorescence spectro-
photometer and JASCO FP-6500 spectrofluorometer at 25ꢁ0.18C. IR
spectra were recorded on a Horiba FTIR-710 spectrophotometer at room
temperature. 1H (400 MHz) and 13C (100 MHz) NMR spectra at 35ꢁ
Photoreaction of 8–11): In a typical experiment, an aqueous solution (or
a D2O solution when photoreactions were followed by 1H NMR) of sub-
strate in a quartz cuvette with a soft rubber septum was purged with
argon gas for at least 10 min. Photoirradiation of the cuvettes was per-
formed at a given wavelength using a JASCO FP-6500 spectrofluorome-
ter equipped with a 150 W xenon lamp with a band pass of 20 nm and a
magnetic stirrer. The photolysis of 9 and 11 was followed by 1H NMR,
UV, fluorescent spectral measurements.
Photoreaction of TACHTNUTGRNEUNG[c,s]T (24): The preparation of 24 was carried out ac-
cording to the method of Murata et al.[46] In a typical experiment, an
aqueous solution (or a D2O solution when photoreactions were followed
by 1H NMR) of 24 in a quartz cuvette with a soft rubber septum was
purged with argon gas for at least 10 min.[43] The photoirradiation of the
cuvettes was performed at a given wavelength using a JASCO FP-6500
spectrofluorometer described in the text. The photoreversion of 23b was
1
followed by H NMR and analyzed by reversed-phase HPLC as we previ-
ously reported.[43]
0.18C were recorded on
a
JEOL Lambda 400 spectrometer. 1H
(300 MHz) and 13C (75 MHz) NMR spectra were recorded on a JEOL
Always 300 spectrometer. The chemical shifts (d values) in D2O were de-
termined by use of external reference of [2-D2,3-D2]3-(trimethylsilyl)pro-
pionic acid (TSP) sodium salt (0 ppm for 1H NMR) and 1,4-dioxane
(67.2 ppm for 13C NMR). The pD values in D2O were corrected for a
deuterium isotope effect using pD=(pH-meter reading)+0.40. Elemental
analyses were performed on a Perkin–Elmer CHN 2400 analyzer. Thin-
layer chromatography (TLC) and silica gel column chromatography were
performed using a Merck 5554 (silica gel) TLC plate and Fuji Silysia
Chemical FL-100D, respectively.
Acknowledgements
We are grateful to Prof. Atsushi Nishida of Faculty of the Pharmaceutical
Sciences, Chiba University for helpful discussions. This work was sup-
ported by grants-in-aid from the Ministry of Education, Culture, Sports,
Science and Technology (MEXT) of Japan (no. 18390009 and 19659026)
and High-Tech Research Center Project for Private Universities (match-
ing fund subsidy from MEXT). S.A. is grateful to grants from the Mitsu-
bishi Chemical Corporation Fund (Tokyo), the Terumo Life Science
Foundation (Kanagawa), the Mochida Memorial Foundation for Medical
and Pharmaceutical Research (Tokyo), the Novartis Foundation (Tokyo,
Japan), the Naito Foundation (Tokyo), and the Tokuyama Science Foun-
dation (Tokyo).
Crystallographic
study
of
9·Cl ·
G
(ZnL2·Cl ·
2 ACHTUNGTERNNU(G H2O)3):
C20H37Cl2N5O5SZn, Mr =585.89, yellow needle, crystal size 0.10 mmꢂ
0.08 mmꢂ0.02 mm, monoclinic, space group P21/c (No. 14), a=
22.773(5) ꢃ, b=6.919(1) ꢃ, c=16.601(4) ꢃ, b=97.124(9)8, V=
2595.7(9) ꢃ3, Z=4, 1calcd =1.525 gcmꢀ3, 31390 measured reflections, 7558
unique reflections (Rint =0.035), 2qmax =60.18, R1=0.026 (I>2.00s(I)),
R=0.038 (I>ꢀ3.00s(I)), wR2=0.059 (I/>ꢀ3.00s(I)). CCDC 708937
contains the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallograph-
[1] a) G. H. Whitham, Organosulfur Chemistry, Zeneca, Oxford, 1995;
b) W. M. Horspool in The Chemistry of Sulphonic Acids, Esters and
Their Derivatives (Eds.: S. Patai, Z. Rappoport), Wiley, Chichester,
1991.
[2] a) R. Vardanyan, V. Hruby, Synthesis of Essential Drugs, Elsevier,
Amsterdam, 2006; b) J.-Y. Winum, J.-M. Dognꢅ, An. Casini, X.
UV spectrophotometric and fluorescence titrations: UV spectra and fluo-
rescence emission spectra were recorded on a Hitachi U-3500 spectro-
photometer and JASCO fluorescence spectrophotometer, respectively, at
Chem. Asian J. 2009, 4, 561 – 573
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
571