Light-Induced Formation of Thymine-Containing Mercury(II)-Mediated Base Pairs

Article abstract of DOI:10.1002/chem.201903789

By applying caged thymidine residues, DNA duplexes were created in which Hg^II-mediated base pair formation can be triggered by irradiation with light. When a bidentate ligand was used as the complementary nucleobase, an unprecedented stepwise formation of different metal-mediated base pairs was achieved.

Full text of DOI:10.1002/chem.201903789

A Journal of
Accepted Article
Title: Light-induced formation of thymine-containing mercury(II)-
mediated base pairs
Authors: Shuvankar Naskar and Jens Müller
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Chem. Eur. J. 10.1002/chem.201903789
Link to VoR: http://dx.doi.org/10.1002/chem.201903789
Supported by

10.1002/chem.201903789
Chemistry - A European Journal
COMMUNICATION
Light-induced formation of thymine-containing mercury(II)-
mediated base pairs
Shuvankar Naskar[a] and Jens Müller*[a]
Abstract: By applying caged thymidine residues, DNA duplexes were
created in which HgII-mediated base pair formation can be triggered
by irradiation with light. When a bidentate ligand was used as the
complementary nucleobase, an unprecedented stepwise formation of
different metal-mediated base pairs was achieved.
IV with unprotected thymine residues serves as a reference.
Similarly, duplexes V – VII contain one central T:P base pair. The
artificial phenanthroline-derived nucleoside analogue P has
previously been shown to form a stable HgII-mediated base pair
with thymine, but not with cytosine.[2k] While the central thymine
residue in duplex V bears a photo-cleavable protecting group,
duplexes VI and VII serve as references bearing an unprotected
thymidine (duplex VI) or a non-cleavable substituent (duplex VII).
Metal-mediated base pairs represent a prominent type of nucleic
acid functionalization. By using ligand-containing nucleosides,
hydrogen bonds within a base pair can formally be replaced by a
centrally located metal ion.[1] The T–HgII–T (Fig. 1a) and C–AgI–
C base pairs involving the canonical thymine (T) and cytosine (C)
residues are among the best investigated metal-mediated base
pairs.[1c] In addition, numerous artificial nucleobases have been
shown to be useful in the generation of metal-mediated base pairs
designed for particular functionalities.[2] In several cases, crystal
structures and solution structures have confirmed the proposed
base pairing patterns.[3] As a result of the additional metal-based
functionality, metal-mediated base pairs have been applied in a
variety of research areas, ranging from DNA charge transfer[4] and
oligonucleotide sensors[5] to the generation of DNA-templated
metal clusters[6] and switchable devices.[7] Whenever a switching
functionality has been introduced in the context of metal-mediated
base pairing, the switching process (mostly of DNA topology) was
triggered by the addition (or removal) of a suitable metal ion. In
this communication, we report for the first time the light-triggered
formation of a metal-mediated base pair. Several examples exist
for the use of light to regulate DNA function.[8] Many of these
involve the application of so-called caged nucleobases, i.e.
nucleobases carrying a photo-removable protecting group.[9]
Thymine has been one of the first nucleobases investigated in the
context of photo-caged nucleobases.[10]
As thymine is well-known to coordinate to HgII ions, we decided
to probe the light-triggered HgII-mediated base pair formation of
caged thymidine. Towards this end, a caged thymidine derivative
TNPP with well-established caging properties (Fig. 1b)[10] was
introduced into different oligonucleotide sequences (Table 1). The
duplex sequence applied in this study has previously been used
in many reports on metal-mediated base pairs, allowing a
comparison with other metal-mediated base pairs.[11] Duplexes I
– IV bear one central T:T mismatch, with the caged nucleobase
being located either in the pyrimidine-rich strand (duplex I), in the
purine-rich strand (duplex II) or in both strands (duplex III). Duplex
a)
O
N
O
O
N
O
II
Hg
O
N
N
O
O
O
O
O
T-Hg(II)-T
c)
b)
O2N
O
N
O
O
N
O
N
R
N
R
TNPP
TPP
Figure 1. Schematic representation of a) metal-mediated T–HgII–T base pair,
b) thymine residue TNPP bearing a photo-removable protecting group, c) thymine
residue TPP bearing a similar protecting group that is not removed upon
irradiation.
Table 1. DNA duplexes under investigation in the present study.[a]
Duplex
Sequence
I
ODN1
ODN2
5’-d(CTT TCT TNPPTC CCT C)
3‘-d(GAA AGA TAG GGA G)
II
ODN3
ODN4
5’-d(CTT TCT TTC CCT C)
3‘-d(GAA AGA TNPPAG GGA G)
III
IV
V
ODN1
ODN4
5’-d(CTT TCT TNPPTC CCT C)
3‘-d(GAA AGA TNPPAG GGA G)
ODN3
ODN2
5’-d(CTT TCT TTC CCT C)
3‘-d(GAA AGA TAG GGA G)
ODN1
ODN5
5’-d(CTT TCT TNPPTC CCT C)
3‘-d(GAA AGA PAG GGA G)
[a]
S. Naskar, J. Müller
Westfälische Wilhelms-Universität Münster
Institut für Anorganische und Analytische Chemie
Corrensstr. 30, 48149 Münster, Germany
E-mail: mueller.j@uni-muenster.de
VI
VII
ODN3
ODN5
5’-d(CTT TCT TTC CCT C)
3‘-d(GAA AGA PAG GGA G)
ODN6
ODN5
5’-d(CTT TCT TPPTC CCT C)
3‘-d(GAA AGA PAG GGA G)
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

10.1002/chem.201903789
Chemistry - A European Journal
COMMUNICATION
namely performing the irradiation at elevated temperature (ca.
50 °C) or investigating the duplex at pH 9.0 rather than pH 6.8
(Fig. S1b). The latter is nicely explained by previous mechanistic
[a] TNPP = thymidine bearing a (2-nitrophenyl)propoxy group, TPP = thymidine
bearing
a phenylpropoxy group, P = (S)-3-(1H-Imidazo[4,5-f][1,10]-
phenanthrolin-1-yl)propane-1,2-diol.
studies indicating
a
deprotonation step during photo-
deprotection.[13] The photo-deprotection of the oligonucleotides
was confirmed mass spectrometrically, as shown exemplarily for
ODN1 (Fig. S2). According to the mass spectrum, a minor amount
of ODN1 remains protected even under optimized conditions. It is
not clear whether this can be attributed to the absence of buffer
under the conditions of mass spectrometry. If it is also present in
buffer, then this amount is small enough not to be detected in the
DNA melting studies.
The formation of coordinate bonds in a metal-mediated base pair
is typically accompanied by an increase in the DNA duplex
melting temperature Tm.[12] Accordingly, metal-mediated base pair
formation was probed by temperature-dependent UV
spectroscopy. Towards this end, the melting temperature of each
duplex was determined in the absence of HgII, after the addition
of one equivalent of HgII prior to irradiation, in the presence of one
equivalent of HgII after irradiation, and in the presence of two
equivalents (i.e. excess) of HgII after irradiation. Table 2 lists the
melting temperatures as derived from the temperature-dependent
UV spectra. Fig. 2 exemplifies the melting curves of duplex I at
pH 6.8.
Table 2. Melting temperatures Tm of the DNA duplexes.[a]
Duplex
pH
Tm / °C
Tm / °C
Tm / °C
Tm / °C
0 HgII, no
light
1 HgII,
no light
1 HgII,
irradiated
upon
irradiation
I
6.8
9.0
6.8
9.0
6.8
9.0
6.8
9.0
6.8
6.8
6.8
29.4(2)
29.5(5)
32.1(4)
30.6(4)
32.8(6)
29.9(6)
35.5(2)
32.4(2)
34.1(5)
31.7(3)
35.5(3)
29.3(3)
28.8(5)
31.6(4)
28.6(6)
32.5(5)
28.7(5)
45.7(2)
42.0(2)
42.0(6)
48.2(4)
40.8(8)
46.2(4)
43.4(3)
45.7(8)
42.0(6)
43.8(6)
39.6(8)
45.8(3)
41.9(2)
49.6(9)
48.1(3)
40(2)
+16.9(5)
+14.6(6)
+14.1(9)
+13.4(8)
+11.3(8)[b]
+10.9(9)
n.a.[c]
I
II
II
Figure 2. Melting curves of duplex I at pH 6.8 in the absence of HgII (black), in
the presence of one equivalent of HgII prior to irradiation (red), in the presence
of one equivalent of HgII after irradiation (blue) and in the presence of two
III
III
IV
IV
V
equivalents of HgII after irradiation (green). Experimental conditions: 1 
duplex, 150 m NaClO4, 2.5 m Mg(ClO4)2, 5 m MOPS buffer (pH 6.8).
M
M
M
M
n.a.[c]
Essentially the same behavior is found for duplex II (Fig. S3),
where the TNPP:T pair is formally replaced by a T:TNPP pair. This
indicates that the relative position of the caged nucleobase does
not significantly influence the outcome of the HgII-mediated base
pair formation. Interestingly, in duplex III bearing a TNPP:TNPP pair,
the photo-deprotection is incomplete even when heating the
sample (Fig. S4a) or when irradiating for an extended time,
indicating the relevance of steric factors during deprotection, too.
This is confirmed by a mass spectrometric study (Fig. S5), which
shows a reduced efficiency of photo-deprotection of ODN1 when
present in duplex III.[14] Nonetheless, a complete T–HgII–T
formation in duplex III is achieved at pH 9.0 (Fig. S4b). An
investigation of reference duplex IV bearing a central T:T mispair
shows the anticipated T–HgII–T base pair formation immediately
after the addition of one equivalent of HgII (Fig. S6). Here, an
irradiation of the solution is not required. In fact, irradiation does
not significantly influence Tm any further. For duplexes I – IV, the
formation of the T–HgII–T pair is accompanied by a decrease in
molar ellipticity [] at 280 nm (Fig. S7). In all four cases, the drop
in [] occurs under those conditions that evoke an increase in Tm,
confirming a simultaneous deprotection and base pair formation.
As can be seen from Table 2, Tm of duplexes I – III in the absence
of HgII are decreased by 3 – 6 °C with respect to that of duplex IV,
+8(1)
VI
VII
n.a.[c]
±0(2)
[a] Given in parenthesis is the standard error (3) obtained upon fitting the
derivative of the melting curve with a Gauss function (Tm) or using error
propagation (Tm). [b] Data for higher melting point of biphasic transition due
to incomplete formation of the HgII-mediated base pair. [c] not applicable.
As can be seen, the addition of HgII does not lead to any change
in Tm prior to irradiation of the sample. After 1 min of irradiation of
a heated sample, a significant increase in Tm of 17 °C is
observed. Initial experiments with irradiation at room temperature
had resulted in a biphasic melting behavior (Fig. S1a), with the
first melting transition coinciding with the Tm of the HgII-free duplex,
suggesting an incomplete photo-deprotection and hence an
incomplete formation of the T–HgII–T pair. Several subsequent
attempts to achieve a complete formation of the metal-mediated
base pair failed, including an extended irradiation time, the use of
a different buffer, and the addition of HgII after the irradiation
rather than prior to it (data not shown). Finally, two conditions
were established that lead to a complete T–HgII–T formation,
This article is protected by copyright. All rights reserved.

10.1002/chem.201903789
Chemistry - A European Journal
COMMUNICATION
indicating a destabilizing effect of the bulky protecting group. After
formation of the T–HgII–T pair, the melting temperatures of
duplexes I and II are, within standard error, identical to that of
duplex IV. The melting temperature of duplex III is marginally
lower, which may indicate the presence of a minor fraction of still
protected oligonucleotide even under the optimized photo-
deprotection conditions in this case.
In a T–HgII–T pair, the HgII ion binds both nucleobases in a
monodentate fashion (Fig. 1a). Hence, the Hg–N bond involving
the first thymine residue must be formed prior to the formation of
the N–Hg bond to the other thymine.[15] A different scenario is
anticipated for the T–HgII–P pair (Fig. 3).[2k] It contains the
phenanthroline-derived nucleoside analogue P that had been
applied in a series of studies, including the concomitant site-
specific incorporation of AgI and HgII into the same duplex and the
first enantiospecific formation of a metal-mediated base pair.[2k, 16]
As P is a bidentate ligand, it is expected to be metalated first
during the formation of a metal-mediated base pair,[5b] irrespective
of the identity of the complementary nucleobase. If the
complementary nucleobase is a thymine residue, then a T–HgII–
P base pair is formed.[2k] The question arises what will happen if
the protected TNPP acts as complementary nucleobase. Here, two
scenarios are feasible. The steric clash of the metalated P residue
and the bulky thymine derivative may result in an extrusion of one
base from the duplex,[5b] so that a destabilization of the duplex
would be expected. Alternatively, the formation of a HgII-mediated
base pair involving the TNPP ligand may occur, which should be
accompanied by a minor duplex stabilization. To evaluate these
possibilities, duplex V with a central TNPP:P pair was investigated.
Figure 4. Melting curves of duplex V at pH 6.8 in the absence of HgII (black), in
the presence of one equivalent of HgII prior to irradiation (red), in the presence
of one equivalent of HgII after irradiation (blue) and in the presence of two
equivalents of HgII after irradiation (green). Experimental conditions: 1 
duplex, 150 m NaClO4, 2.5 m Mg(ClO4)2, 5 m MOPS buffer (pH 6.8).
M
M
M
M
To confirm this assumption, duplexes VI and VII bearing a T:P or
a TPP:P pair, respectively, were investigated. Duplex VI is
stabilized by 16.5 ± 0.5 °C upon formation of the T–HgII–P pair
(Fig. S8a). This stabilization is identical to the one observed for
duplex V upon metal binding and photo-deprotection (16 ± 1 °C).
The TPP nucleobase in duplex VII bears a substituent of similar
size as TNPP. However, this substituent cannot be removed by
irradiation. For duplex VII, Tm increases by 5.3 ± 0.9 °C upon the
addition of HgII (Fig. S8b). Even though this increase is a bit
smaller than that observed for duplex V (7.9 ± 0.8 °C), the
O
N
N
N
N
II
Hg
experiment clearly confirms the applicability of
a caged
N
O
nucleobase in HgII-mediated base pairing. As anticipated,
subsequent irradiation does not lead to a change in Tm. Again, the
formation of the metal-mediated base pair can be confirmed CD-
spectroscopically. The binding of HgII to form a TNPP–HgII–P pair
in duplex V evokes an increase in [] at 275 nm (Fig. S9a). The
same observation is made for reference duplex VII upon the
formation of the TPP–HgII–P pair (Fig. S9c). Generation of the final
N
O
O
O
O
O
Figure 3. Proposed structure of the metal-mediated T–HgII–P base pair.
T–HgII–P pair in duplex
V
upon photo-deprotection is
accompanied by a blue-shift of the positive Cotton effect and a
decrease in [] at 245 nm (Fig. S9a). Again, the same effects are
observed upon the formation of the T–HgII–P pair in reference
duplex VI (Fig. S9b). Taken together, these data prove that caged
nucleobases can be involved in metal-mediated base pairing,
provided that the complementary nucleobase is a bidentate ligand.
It is interesting to note that the O4-protected thymine residue does
not require deprotonation at its N3 position to engage in metal-
mediated base pairing, due to its enol tautomeric form (Fig. 1b).
In this respect, it appears to resemble cytosine, a nucleobase that
is known not to form HgII-mediated base pairs. The formation of a
stable T(N)PP–HgII–P pair thus indicates that a simple protonation /
deprotonation event cannot explain the preferential binding of HgII
to thymine rather than cytosine and that additional (e.g. electronic)
factors must exist, too.
Again, temperature-dependent UV spectroscopy was applied to
probe metal-mediated base pair formation. Fig. 4 shows the
melting curves obtained for duplex V. An increase in Tm of 7.9 ±
0.8 °C is observed after the addition of one HgII per duplex prior
to photo-deprotection, suggesting that a TNPP–HgII–P base pair is
indeed formed with the caged nucleobase. Subsequent irradiation
at room temperature leads to a further increase in Tm of 8 ± 1 °C,
indicating photo-deprotection and formation of a T–HgII–P pair.
Hence, the chelating phenanthroline-derived ligand P binds the
HgII ion irrespective of the identity of the complementary
nucleobase. Even though the thymine residue bears a bulky
protecting group, it is forced to engage in metal-mediated base
pairing. Metal-mediated base pair formation may additionally be
facilitated by the more flexible acyclic backbone of P. Finally,
photo-deprotection relieves the steric strain, accompanied by a
further increase in the melting temperature.
To conclude, we have shown for the first time the light-triggered
formation of a metal-mediated base pair, achieved by applying a
This article is protected by copyright. All rights reserved.

10.1002/chem.201903789
Chemistry - A European Journal
COMMUNICATION
[2]
a) Y. Takezawa, K. Nishiyama, T. Mashima, M. Katahira, M. Shionoya,
Chem. Eur. J. 2015, 21, 14713-14716; b) K. Tanaka, A. Tengeiji, T. Kato,
N. Toyama, M. Shionoya, Science 2003, 299, 1212-1213; c) M. Su, M.
Tomás-Gamasa, T. Carell, Chem. Sci. 2015, 6, 632-638; d) X. Guo, P.
Leonard, S. A. Ingale, J. Liu, H. Mei, M. Sieg, F. Seela, Chem. Eur. J.
2018, 24, 8883-8892; e) S. K. Jana, X. Guo, H. Mei, F. Seela, Chem.
Commun. 2015, 51, 17301-17304; f) J. M. Méndez-Arriaga, C. R.
Maldonado, J. A. Dobado, M. A. Galindo, Chem. Eur. J. 2018, 24, 4583-
4589; g) N. Santamaría-Díaz, J. M. Méndez-Arriaga, J. M. Salas, M. A.
Galindo, Angew. Chem. Int. Ed. 2016, 55, 6170-6174; h) S. K. Maity, T.
Lönnberg, Chem. Eur. J. 2018, 24, 1274-1277; i) D. U. Ukale, T.
Lönnberg, Angew. Chem. Int. Ed. 2018, 57, 16171-16175; j) B. Jash, J.
Müller, Angew. Chem. Int. Ed. 2018, 57, 9524-9527; k) B. Jash, J. Müller,
Chem. Eur. J. 2018, 24, 10636-10640; l) S. Mandal, A. Hepp, J. Müller,
Dalton Trans. 2015, 44, 3540-3543; m) L. L. G. Al-Mahamad, O. El-Zubir,
D. G. Smith, B. R. Horrocks, A. Houlton, Nat. Commun. 2017, 8, 720; n)
O. P. Schmidt, G. Mata, N. W. Luedtke, J. Am. Chem. Soc. 2016, 138,
14733-14739; o) A. Fujii, O. Nakagawa, Y. Kishimoto, T. Okuda, Y.
Nakatsuji, N. Nozaki, Y. Kasahara, S. Obika, Chem. Eur. J. 2019, 25,
7443-7448; p) I. Schönrath, V. B. Tsvetkov, T. S. Zatsepin, A. V. Aralov,
J. Müller, J. Biol. Inorg. Chem. 2019, 24, 693-702; q) N. Sandmann, J.
Bachmann, A. Hepp, N. L. Doltsinis, J. Müller, Dalton Trans. 2019, 48,
10505-10515; r) N. Sandmann, D. Defayay, A. Hepp, J. Müller, J. Inorg.
Biochem. 2019, 191, 85-93.
caged thymidine residue. When using a bidentate ligand as the
complementary nucleobase, an unprecedented stepwise duplex
stabilization was accomplished. Here, the addition of HgII leads to
the formation of a stabilizing metal-mediated base pair involving
the caged nucleobase. Subsequent photo-deprotection results in
an additional increase in stability. The possibility of using light as
an external trigger for metal-mediated base pair formation and the
ability to use two orthogonal triggers for the stepwise formation of
metal-mediated base pairs of different stability significantly
expands the scope of metal-modified nucleic acids. In
combination with DNA that switches its topology upon metal-
mediated base pair formation, interesting applications are
anticipated.
Experimental Section
The phosphoramidites of TNPP and P were prepared according to published
[10b]
procedures.[10b, 17] The TPP nucleoside was prepared in analogy to TNPP
.
Details are given in the Supporting Information. All other phosphoramidites
were purchased (Glen Research). The oligonucleotides were synthesized
and purified as described previously.[17] The desalted oligonucleotides
were characterized by MALDI-TOF mass spectrometry (ODN1: calcd. for
[M+H]+: 3966 Da, found: 3967 Da; ODN2: calcd. for [M+H]+: 4097 Da,
found: 4096 Da; ODN3: calcd. for [M+H]+: 3803 Da, found: 3803 Da;
ODN4: calcd. for [M+H]+: 4260 Da, found: 4262 Da; ODN5: calcd. for
[M+H]+: 4149 Da, found: 4150 Da; ODN6: calcd. for [M+H]+: 3921 Da,
found: 3920 Da). During oligonucleotide quantification, the following molar
[3]
[4]
a) J. Müller, Coord. Chem. Rev. 2019, 393, 37-47; b) J. Kondo, Y. Tada,
T. Dairaku, Y. Hattori, H. Saneyoshi, A. Ono, Y. Tanaka, Nat. Chem.
2017, 9, 956-960; c) J. Kondo, T. Sugawara, H. Saneyoshi, A. Ono,
Chem. Commun. 2017, 53, 11747-11750.
a) S. Liu, G. H. Clever, Y. Takezawa, M. Kaneko, K. Tanaka, X. Guo, M.
Shionoya, Angew. Chem. Int. Ed. 2011, 50, 8886-8890; b) J. C. Léon, Z.
She, A. Kamal, M. H. Shamsi, J. Müller, H.-B. Kraatz, Angew. Chem. Int.
Ed. 2017, 56, 6098-6102; c) E. Beall, A. Sargun, S. Ulku, Y. Bae, E.
Wierzbinski, C. Clever, D. H. Waldeck, C. Achim, J. Phys. Chem. C 2018,
122, 7533-7540.
extinction coefficients were used: TNPP, 260 = 7.5 cm2 mol–1 [10b]
= 4.2 cm2 mol–1; P, 260 = 10.0 cm2 mol–1 [5b]
;
TPP, 260
.
The UV melting experiments were carried out on a UV spectrometer CARY
100 Bio (Agilent) in a 1 cm quartz cuvette. The UV melting profiles were
[5]
a) S. Taherpour, O. Golubev, T. Lönnberg, Inorg. Chim. Acta 2016, 452,
43-49; b) B. Jash, P. Scharf, N. Sandmann, C. Fonseca Guerra, D. A.
Megger, J. Müller, Chem. Sci. 2017, 8, 1337-1343.
measured in buffer (1 
M DNA duplex, 150 mM NaClO4, 2.5 mM Mg(ClO4)2,
5 m buffer (pH 6.8: MOPS, pH 9.0: borate) either with or without
M
[6]
[7]
J. C. Léon, G. González-Abradelo, C. A. Strassert, J. Müller, Chem. Eur.
J. 2018, 24, 8320-8324.
Hg(ClO4)2 at a scan rate of 1 °C min–1 with detection at 260 nm. CD spectra
were measured using a J-815 spectropolarimeter (JASCO) at 10 °C in the
same solution. Each irradiation experiment was performed for 1 min (at ca.
50 °C for duplexes I – III at pH 6.8 or at room temperature in all other
cases) using a 500 W Hg/Xe arc lamp (Newport) equipped with a 1.5 inch
water filter and a 335 nm longpass filter (Schott). NMR spectra were
recorded on Bruker Avance(I) 400 and Avance(III) 400 instruments. NMR
spectra were referenced to residual solvent peaks (CD3OD, CD2Cl2) or to
tetramethylsilane (CDCl3).
a) Y. Takezawa, S. Yoneda, J.-L. H. A. Duprey, T. Nakama, M. Shionoya,
Chem. Sci. 2016, 7, 3006-3010; b) D. M. Engelhard, J. Nowack, G. H.
Clever, Angew. Chem. Int. Ed. 2017, 56, 11640-11644.
[8]
a) L. Anhäuser, F. Muttach, A. Rentmeister, Chem. Commun. 2018, 54,
449-451; b) V. Adam, D. K. Prusty, M. Centola, M. Škugor, J. S. Hannam,
J. Valero, B. Klöckner, M. Famulok, Chem. Eur. J. 2018, 24, 1062-1066;
c) S. Boháčová, Z. Vaníková, L. Poštová Slavětínská, M. Hocek, Org.
Biomol. Chem. 2018, 16, 5427-5432; d) S. Wang, L. Yue, Z.-Y. Li, J.
Zhang, H. Tian, I. Willner, Angew. Chem. Int. Ed. 2018, 57, 8105-8109.
a) Q. Liu, A. Deiters, Acc. Chem. Res. 2014, 47, 45-55; b) C. Brieke, F.
Rohrbach, A. Gottschalk, G. Mayer, A. Heckel, Angew. Chem. Int. Ed.
2012, 51, 8446-8476.
[9]
Acknowledgements
[10] a) A. Heckel, G. Mayer, J. Am. Chem. Soc. 2005, 127, 822-823; b) L.
Kröck, A. Heckel, Angew. Chem. Int. Ed. 2005, 44, 471-473.
[11] S. Litau, J. Müller, Z. Anorg. Allg. Chem. 2015, 641, 2169-2173.
[12] B. Jash, J. Müller, Chem. Eur. J. 2017, 23, 17166-17178.
[13] S. Walbert, W. Pfleiderer, U. E. Steiner, Helv. Chim. Acta 2001, 84, 1601-
1611.
We gratefully acknowledge funding by the Westfälische Wilhelms-
Universität Münster (fellowship to S.N.) and thank Dr. Matthias C.
Letzel for the mass spectrometric experiments.
Keywords: bioinorganic chemistry • nucleic acid • metal-
[14] An additional influence could be different kinetics of hybridisation of
duplexes I – III that lead to a decreased rate of photo-deprotection of the
TNPP:TNPP pair in duplex III.
mediated base pair • caged nucleoside
[1]
a) S. Naskar, R. Guha, J. Müller, Angew. Chem. Int. Ed. 2019, doi:
10.1002/anie.201905913; b) Y. Takezawa, J. Müller, M. Shionoya, Chem.
Lett. 2017, 46, 622-633; c) Y. Tanaka, J. Kondo, V. Sychrovský, J.
Šebera, T. Dairaku, H. Saneyoshi, H. Urata, H. Torigoe, A. Ono, Chem.
Commun. 2015, 51, 17343-17360; d) G. H. Clever, C. Kaul, T. Carell,
Angew. Chem. Int. Ed. 2007, 46, 6226-6236.
[15] J. Šebera, J. Burda, M. Straka, A. Ono, C. Kojima, Y. Tanaka, V.
Sychrovský, Chem. Eur. J. 2013, 19, 9884-9894.
[16] B. Jash, J. Neugebauer, J. Müller, Inorg. Chim. Acta 2016, 452, 181-187.
[17] P. Scharf, B. Jash, J. A. Kuriappan, M. P. Waller, J. Müller, Chem. Eur.
J. 2016, 22, 295-301.
This article is protected by copyright. All rights reserved.

10.1002/chem.201903789
Chemistry - A European Journal
COMMUNICATION
Entry for the Table of Contents
COMMUNICATION
The light-triggered formation of two
types of HgII-mediated base pairs is
reported.
S. Naskar, J. Müller*
Page No. – Page No.
Light-induced formation of thymine-
containing mercury(II)-mediated base
pairs
This article is protected by copyright. All rights reserved.