The Remarkable Effect of Halogen Substitution on the Membrane Transport of Fluorescent Molecules in Living Cells

Article abstract of DOI:10.1002/anie.201804128

Small-molecule-based fluorescent probes have become important tools in biology for sensing and imaging applications. However, the biological applications of many of the fluorescent molecules are hampered by low cellular uptake and high toxicity. In this paper, we show for the first time that the introduction of halogen atoms enhances the cellular uptake of fluorescent molecules and the nature of halogen atoms plays a crucial role in the plasma membrane transport in mammalian cells. The remarkably higher uptake of iodinated compounds compared to that of their chloro or bromo analogues suggests that the strong halogen bonding ability of iodine atoms may play an important role in the membrane transport. This study provides a novel strategy for the transport of fluorescent molecules across the plasma membrane in living cells.

Full text of DOI:10.1002/anie.201804128

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
International Edition Chemie
www.angewandte.org
Accepted Article
Title: Remarkable Effect of Halogen Substitution on the Membrane
Transport of Fluorescent Molecules in Living Cells
Authors: Harinarayana Ungati, Vijayakumar Govindaraj, and
Govindasamy Mugesh
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: Angew. Chem. Int. Ed. 10.1002/anie.201804128
Angew. Chem. 10.1002/ange.201804128
Link to VoR: http://dx.doi.org/10.1002/anie.201804128
http://dx.doi.org/10.1002/ange.201804128

Angewandte Chemie International Edition
10.1002/anie.201804128
COMMUNICATION
Remarkable Effect of Halogen Substitution on the Membrane
Transport of Fluorescent Molecules in Living Cells
Harinarayana Ungati, Vijayakumar Govindaraj and Govindasamy Mugesh*
Abstract: Small-molecule-based fluorescent probes have become
important tools in biology for sensing and imaging applications.
However, the biological applications of many of the fluorescent
molecules are hampered by low cellular uptake and high toxicity. In
this paper, we show for the first time that the introduction of halogen
atoms enhances the cellular uptake of fluorescent molecules and the
Localization
solubility
functionality
OR'
N
OR'
N
Cl
Cl
O
R
N
O
O
O
O
O
Fluorophore
ex ~420 nm
em ~520 nm
nature of halogen atoms plays
a crucial role in the plasma
membrane transport in mammalian cells. The remarkably higher
uptake of iodinated compounds as compared to that of their chloro
or bromo analogues suggests that the strong halogen bonding ability
of iodine atoms may play an important role in the membrane
transport. This study provides a novel strategy for the transport of
fluorescent molecules across the plasma membrane in living cells.
N
X
X
NR2
NR2
1
, R = H, R' = H
2, R = H, R' = Me
, R = R' = Me
4, R = H, R' = H
5, R = H, R' = Me
6, R = R' = Me
3
OR'
N
OR'
OR'
Br
Br
I
I
I
Fluorescence imaging has emerged as a powerful tool to study
the concentration, localization and functions of various
O
O
O
N
O
O
N
O
[
1]
biomolecules at the cellular level. Particularly, small-molecule-
based fluorescent probes have found diverse applications in the
areas of cell biology, drug discovery, chemical biology, and
NR2
NR2
NR2
[2]
7, R = H, R' = H
, R = H, R' = Me
9, R = R' = Me
10, R = H, R' = H
11, R = H, R' = Me
12, R = R' = Me
13, R = H, R' = H
14, R = H, R' = Me
15, R = R' = Me
clinical diagnosis. Although a large number of small-molecular
fluorescent probes have been developed for various cellular
8
[
3-5]
applications,
the mechanisms by which these molecules enter
Figure 1. Chemical structure of fluorescent molecules 1-15 synthesized in this
study based on 4-amino-1,8-naphthalimide moiety.
the cells are not well understood in many cases. Fluorescence
probes based on 4-amino-1,8-naphthalimide have attracted
significant attention as these compounds can be synthesized in
high yields from readily available starting materials and their
solubility and fluorescence property can be altered by
The naphthalimide-based compounds 1-15 (Figure 1)
required for this study were synthesized from 4-nitro-1,8-
naphthalic anhydride and 4-aminophenol or halogen-substituted
[6]
substitution at the amino and imide moieties (Figure 1). The
[7]
two-photon fluorescent probe for the detection of formaldehyde ,
the lysosome-targetable probe for monitoring the endogenous
4
-aminophenols as described in the Supporting Information. The
[8]
fluorescent properties of compounds 1-15 were studied in
phosphate-buffered saline (PBS) at room temperature. As these
compounds have low solubility in an aqueous medium, the
compounds were dissolved in DMSO and diluted with PBS
buffer by 1:100. The luminescent properties of compounds 1-15
strongly depend on the substituents at the naphthalimide and
nitric oxide (NO), the solvatochromic fluorophore for the
[9]
development of a protein-based pH sensor, the ratiometric
[10]
fluorescent probe for monitoring the mitochondrial NO level,
the pantetheine probe for the visualization of the chain-flipping
[11]
mechanism in fatty-acid biosynthesis represent a few selected
examples of fluorescent probes that have been employed
successfully for cellular applications. In this paper, we report for
the first time that a simple substitution of hydrogen atoms with
halogens remarkably enhances the cellular uptake of
naphthalimide-based fluorescent molecules in mammalian cells.
This study also suggests that halogen bonding may facilitate the
active transport of halogenated compounds, particularly
iodinated compounds, across the plasma membrane.
2
phenolic rings with the –NR and substituted phenyl group acting
as the electron donor and acceptor, respectively. As expected,
compound 1 exhibited a significant fluorescence by push-pull
mechanism (Figure 2A-D) and there was an enhancement in the
fluorescence when the strongly electron donating –OH group at
the phenyl ring was replaced by a less electron-donating
methoxy group (compound 2).
fluorescence intensity was observed when an –NMe
introduced at the 4-position of the naphthalimide moiety
compound 3). A similar trend was observed when halogen
A
further increase in the
2
group was
(
[
*]
H. Ungati, Dr. V. Govindaraj and Prof. Dr. G. Mugesh
Department of Inorganic and Physical Chemistry
Indian Institute of Science
Bangalore 560012, India
E-mail: mugesh@iisc.ac.in
atoms were introduced to the phenolic ring at 2,6-positions.
However, a gradual decrease in the fluorescence intensity was
observed upon introduction of chlorine, bromine and iodine
atoms (Figure 2D), which is in agreement with the heavy-atom
[
12]
effect observed for other related fluorescent systems.
To
Supporting information and the ORCID identification number(s) for
the author(s) of this article can be found under:
https://doi.org/10.1002/anie.2018xxxx.
understand the lipophilicity of compounds 1-15, the partition
coefficient (P) in octanol-water biphasic system was determined
This article is protected by copyright. All rights reserved.

Angewandte Chemie International Edition
10.1002/anie.201804128
COMMUNICATION
by using HPLC and compared the experimental log P values
with the corresponding theoretical values obtained using the
the amounts of compounds 10, 11 and 12 entered the cells were
determined to be 14%, 22% and 38%, respectively (Figure 3B).
Remarkably, a rapid cellular uptake was observed for the diiodo
compounds 13 (22%), 14 (41%) and 15 (98%), indicating that
the steric hindrance introduced by two iodine atoms does not
block the transport of these compounds across the plasma
membrane. A similar trend was observed when HEK293 and
HeLa cells were used for the experiments (Figure S52-53). To
understand whether the heavier halogen atoms can facilitate the
uptake in normal cells, we studied the uptake of compounds 1-
[
13]
ALOGPS program (Figure 2E).
These results indicate that
there is no major change in the lipophilicity upon introduction of
heavier halogen atoms.
15 in primary endothelial cells (HUVEC) isolated from human
umbilical vein. A facile uptake of compounds 12 and 15 was
observed in these cells as well (Figure 3A, S50).
As substitution of heavier halogen may lead to higher toxicity,
the cell viability was determined by using the standard MTT
assay. Interestingly, the toxicity of the bromo and iodo
compounds (7-15) was found to be almost identical to that of the
unsubstituted compounds 1-3 (Figure 3C), indicating that the
Figure 2. (A) The D--A interactions that are responsible for the fluorescence
bahaviour of compounds 1-15. (B) The normalized UV-Vis and fluorescence
spectra of compound 1 in water. (C) Excitation and emission wavelengths for
compounds 1-15. (D) The relative fluorescence intensity for compounds 1-15
in phosphate-buffered saline (PBS). (E) The lipophilicity of compounds 1-15
given in terms of their log P values.
The interesting fluorescent properties of compounds 1-15
prompted us to investigate their uptake in mammalian cells. We
studied the cellular uptake of the fluorescent molecules in
HepG2 (human liver carcinoma), HEK293 (human embryonic
kidney) cells by using laser scanning microscopy and
fluorescence microplate reader techniques. The HepG2 cells
treated with compounds 1-3 for 30 min at 10 M concentration
showed a very low fluorescence (Figure 3A and 3B), indicating
that these compounds are not taken up readily by the cells.
When the cell culture medium was analysed after 30 min of
treatment, it was observed that only small amounts of
compounds 1 (5%), 2 (6%) and 3 (8%) entered the cells (Figure
3B, S47-49). The cellular uptake was marginally improved for
compounds 4 (7%), 5 (10%) and 6 (15%), suggesting that the
introduction of chlorine atoms increases the cellular uptake.
Furthermore, the higher uptake of compound 9 (22%) having
Figure 3. (A) Confocal microscopy images of HepG2 cells treated with
compounds 1-15 (10 M) for 30 min. The last two images indicate the uptake
of the two iodo compounds 12 and 15 by human umbilical vein endothelial
cells (HUVEC, primary cells) under identical conditions. (B) The fluorescence
measured by a plate reader after 30 min of treatment of HepG2 cells with
compounds 1-15 (10 M) and the total uptake of compounds 1-15 by HepG2
cells. The % cellular uptake was calculated from the amount of compounds left
in the medium after 30 min treatment. (C) Cell viability of HepG2 cells
incubated with compounds 1-15 at various concentrations after 1, 12 and 24h.
2
two bromine atoms and an –NMe group indicates that the
introduction of heavier halogen may facilitate the cellular entry of
the 1,8-naphthalimide derivatives. Interestingly, the introduction
of an iodine atom significantly increased the cellular uptake as
This article is protected by copyright. All rights reserved.

Angewandte Chemie International Edition
10.1002/anie.201804128
COMMUNICATION
introduction of heavier halogen atoms does not alter the toxicity
of the compounds. While the compounds did not exhibit any
cytotoxicity up to 10 M concentration, they were found to be
toxic to the cells at 25 M and above concentrations. Recently,
silychristin (Figure 4D and S56), which indicates that
transporters other than MCT8 are probably not involved in the
transport and the introduction of heavier halogen may increase
the selectivity of transport through a biological membrane. The
inhibition of membrane transport of compound 15 by silychristin
was also observed in HeLa and HEK293 cells (Figure S57 and
S58). A similar transport is expected to occur in HUVEC as
MCT8 is the major transporter of T4 and T3 in all mammalian
cells.
Yang and co-workers reported
a biocompatible halogen-
containing fluorescent probe (HKOH-1r) based on fluorescein for
[4c]
the detection of endogenous hydroxyl radicals in living cells. In
this work, the authors demonstrated that the diiodophenol acts
as a quencher of fluorescein or 2,7-dichlorofluorescein and the
steric hindrance of the two iodine atoms blocks the oxidation by
strong oxidants such as HOCl or peroxynitrite. However, it is not
clear whether the iodine atoms play any role in the cellular
uptake of the fluorescent probes.
The remarkably higher uptake of the diiodo compound 15
(98% in HepG2 cells) as compared to other compounds
indicates that the iodo compounds may be transported across
the plasma membrane by specific transporters that have high
affinity for iodine atoms. It is known that the iodine-containing
thyroid hormone, thyroxine (T4, Figure 4A), crosses the plasma
membrane with the help of transport proteins. Although T4 and
its metabolites are hydrophobic in nature, they cannot simply
diffuse across the lipid bilayer membrane, probably due to the
larger size of iodine atoms and the charged nature of the amino
acid moiety. Visser and co-workers reported that the
monocarboxylate transporter 8 (MCT8) acts as a very active and
[14]
specific thyroid hormone transporter.
It is known that
mutations in the human MCT8 leads to a genetic disorder known
[15]
as Allan–Herndon–Dudley syndrome.
Therefore, it was
thought worthwhile to understand the mechanism of transport of
compound 15 in mammalian cells. Interestingly, when HepG2
cells were co-treated with compound 15 (10 M) and T4, it was
found that T4 inhibits the uptake of compound 15 in a dose-
dependent manner (Figure 4A and 4B). At 1 M concentration of
T4, an almost 70% inhibition of the cellular uptake of compound
15 was observed. To understand whether the number of iodine
atoms plays an important role, the cellular uptake of 15 was
studied in the presence of T3, 3,5-T2 and T1, having three, two
and one iodine atom(s), respectively. While T3 blocks the
cellular uptake of 15 as efficient as T4, a significantly decreased
inhibition was observed in the presence of T2. In contrast, T1
having one iodine atom was unable to block the uptake of 15
under identical conditions. Similarly, no inhibition was observed
for the fully deiodinated thyroxine derivative T0 even at 10 M
concentration (Figure 4A). These observations indicate that the
fluorescent molecules 1-15, particularly the halogenated
compounds, enter the cells through the thyroid hormone
transporter and the higher uptake of compound 15 is due to the
presence of two iodine atoms that appear to play a crucial role in
the membrane transport.
Figure 4. (A) The fluorescence measured by a plate reader after 30 min of
treatment of HepG2 cells with compound 15 (10 M) in the presence of
various concentrations (0.01 - 10.0 M) of thyroxine (T4) and its metabolites
T3, 3,5-T2, 3-T1 and T0. (B) Confocal microscopy images of HepG2 cells co-
treated with compound 15 (10 M) and various concentrations of T4 or T0 for
30 min. (C) Chemical structure of silychristin, a potent inhibitor of the thyroid
hormone transporter MCT8. (D) Inhibition of the cellular uptake of compound
15 by silychristin. The fluorescence was measured by a plate reader after
treating the HepG2 cells with various concentrations of silychristin for 20 min,
followed by treatment with compound 15 (10 M) for 20 min.
It has been shown by Johannes et al that silychristin, a
flavonolignan derived from the milk thistle, is a potent inhibitor of
[
16]
MCT8. When the cellular uptake of compound 15 was carried
out in HepG2 cells, silychristin strongly inhibited the uptake in a
dose-dependent manner with an IC50 value of 8.13 M,
confirming that MCT8 is involved in the transport of the halogen-
substituted fluorescent molecules. An almost complete inhibition
of cellular uptake was observed at higher concentrations of
For each series of compounds 4-6, 7-9, 10-12 and 13-15
(Figure 1), the cellular uptake increases with an increase in the
size of the halogen atom. For example, the cellular entry of
compounds 6, 9, 12 and 15, is higher than that of the
unsubstituted compound 3, and the uptake follows the order I >
Br > Cl. For the iodo compounds 10-15, the internalization of the
This article is protected by copyright. All rights reserved.

Angewandte Chemie International Edition
10.1002/anie.201804128
COMMUNICATION
diiodo compounds 13-15 is found to be higher than that of the
corresponding monoiodo compounds (10-12). It is known that
halogen atoms form halogen bonds with electron donors and
their halogen bonding ability increases from chlorine to bromine
by increasing the active transport across the plasma membrane
in
[
17]
to iodine.
Owing to the anisotropic distribution of charge on
halogen (X) atoms, a positively charged electrostatic region is
created along the C−X bonds. The region of positive
electrostatic potential, known as σ-hole, can interact attractively
[
18]
with the electron donors, forming halogen bonds.
Although
halogen bonds has attracted significant attention in drug
[
19]
discovery,
it remains unclear whether they play key roles
beyond their applications in improving drug−target interactions.
Matile and co-workers and others showed that halogen bonds
[
20]
can be used for ion transport in synthetic membrane systems.
Although the thyroid hormones, T4 and T3, are known to
form halogen bonds with their transport proteins transthyretin
[
21]
(TTR) and thyroxine-binding globulin (TBG),
it is not known
whether halogen bonding is responsible for the cellular uptake of
thyroid hormones by MCT8. The present study indicates that
halogen bonds may play crucial roles in cellular uptake of
organohalogen compounds. The density functional theory
[22]
(DFT)
calculations on the halogenated compounds 4-15
indicate that the halogen bonding ability of the iodo compounds
is greater than that of the corresponding bromo or chloro
compounds. A comparison of the positive electrostatic potential
[23]
(
σ-hole), calculated by natural bond orbital (NBO) analysis,
indicates that the σ-hole on the iodine atoms of compound 12 is
less positive than that of 15 (Figure 5A), indicating that the
removal of one iodine from 15 decreases the positive potential
on the other iodine atom. Similarly, a significant decrease in the
positive potential was observed for compounds 6 and 9, which
have chlorine and bromine atoms, respectively. Interestingly, the
cellular uptake of these compounds follows the same order, i.e.
Figure 5. (A) Charges obtained from natural bond orbital (NBO) analysis for
compounds 15, 12, 9 and 6. (B) Chemical structures of compounds 16-23. (C)
The relative fluorescence intensity for compounds 16-23 in phosphate-
buffered saline (PBS). (D) Confocal microscopy images of HepG2 cells treated
with compounds 16-23 (10 M) for 30 min.
15 > 12 > 9 > 6. As T4 and T3 having four and three iodine
atoms, respectively, can strongly bind to the receptor, these
compounds were able to compete with compound 15 for the
cellular entry at low concentrations. It should be noted that the
experimentally determined Log P coefficients for T4 (0.85) and
T3 (0.52) are much lower than that of 15 (2.61), suggesting that
the lipophilicity of the compounds does not play any major role in
the cellular uptake. To understand whether the introduction of
heavier halogen can be used as a general strategy for improving
the cellular uptake of fluorescent molecules, we synthesized
compounds 16-23 (Figure 5B) and studied their fluorescent
behaviour. Interestingly, the cellular uptake of the iodinated
compounds 22 and 23 was found to be much higher than that of
living cells. Several competitive experiments with thyroxine (T4)
and its metabolites and with a specific inhibitor, sylichristin,
indicate that the organohalogen compounds are transported into
the mammalian cells (HepG2, HeLa and HEK293) by the thyroid
hormone-specific monocarboxylate transporter
8
(MCT8).
Halogen bonding appears to pay crucial roles in the membrane
transport and the introduction of heavier halogens may provide a
novel strategy to improve the cellular uptake of organic
molecules for studying membrane activity, cellular functions, and
drug delivery. Further studies are in progress in our laboratory to
understand the interaction of MCT8 and related transporters with
thyroid hormones and their metabolites.
16-21 (Figure 5D), although compounds 22 and 23 are
intrinsically less fluorescent than the corresponding
unsubstituted compounds 16 and 17 (Figure 5C). It is worthwhile
to note that several halogenated compounds that are commonly
used in food packaging and as flame retardants are known to
disrupt the endocrine function, but the mechanism by which
[
24]
Acknowledgements
these compounds are transported into the cells is not clear.
In summary, we showed for the first time that the
introduction of iodine atom to a series of naphthalimide-based
fluorescent molecules remarkably enhances their cellular uptake
This study was supported by the Science and Engineering
Research Board (SERB, EMR/IISc-01/2016), Department of
Science and Technology (DST), New Delhi. H. U. and V. G.
acknowledge the Indian Institute of Science, Bangalore, and
This article is protected by copyright. All rights reserved.

Angewandte Chemie International Edition
10.1002/anie.201804128
COMMUNICATION
SERB, respectively, for a research fellowship. We thank Ms
Megha Narayanan, Mr Subhash Garhwal and Ms Chithra R. Nair
for their help with the synthesis of some of the compounds and
Mrs Mary Nirmala Sarkar for her help with the cell culture work.
G. M. thanks the SERB for the award of J. C. Bose National
fellowship (SB/S2/JCB-067/2015).
[9]
M. Yang, Y. Song, M. Zhang, S. Lin, Z. Hao, Y. Liang, D. Zhang, P. R.
Chen, Angew. Chem. Int. Ed. 2012, 51, 7674-7679.
[
10] X. Zhu, J. Q. Chen, C. Ma, X. Liu, X. P. Cao, H. Zhang, Analyst 2017,
42, 4623-4628.
11] J. Beld, H. Cang, M. D. Burkart, Angew. Chem. Int. Ed. 2014, 53,
4456-14461.
[12] V. Osipov, M. Usacheva, I. Dilung, Appl. Spectrosc. 1983, 39, 1181-
185.
1
[
1
1
[
13] a) I. V. Tetko, P. Bruneau, J. Pharm. Sci. 2004, 93, 3103-3110; b) I. V.
Tetko, J. Gasteiger, R. Todeschini, A. Mauri, D. Livingstone, P. Ertl, V.
A. Palyulin, E. V. Radchenko, N. S. Zefirov, A. S. Makarenko, J.
Comput. Aid. Mol. Des. 2005, 19, 453-463.
Keywords: cellular uptake • halogen • fluorescent molecules •
MCT8 transporter • thyroid hormones
[
[
1]
2]
a) M. T. Spence, I. D. Johnson, Molecular probes handbook: a guide to
fluorescent probes and labeling technologies, 11th ed., Life Tech.
Corp. , Carlsbad, CA, 2010; b) E. A. Specht, E. Braselmann, A. E.
Palmer, Annu. Rev. Physiol. 2017, 79, 93-117.
[
[
[
14] G. Hennemann, R. Docter, E. C. Friesema, M. de Jong, E. P. Krenning,
T. J. Visser, Endocr. Rev. 2001, 22, 451-476.
15] E. C. Friesema, S. Ganguly, A. Abdalla, J. E. M. Fox, A. P. Halestrap, T.
J. Visser, J. Biol. Chem. 2003, 278, 40128-40135.
a) M. Schäferling, Angew. Chem. Int. Ed. 2012, 51, 3532-3554; b) N.
Jiang, J. Fan, F. Xu, X. Peng, H. Mu, J. Wang, X. Xiong, Angew. Chem.
Int. Ed. 2015, 54, 2510-2514; c) M. A. Miller, R. Weissleder, Nat. Rev.
Cancer 2017, 17, 399-414; d) K. J. Bruemmer, T. F. Brewer, C. J.
Chang, Curr Opin Chem Biol. 2017, 39, 17-23.
16] J. Johannes, R. Jayarama-Naidu, F. Meyer, E. K. Wirth, U. Schweizer,
L. Schomburg, J. Köhrle, K. Renko, Endocrinology 2016, 157, 1694-
1701.
[
[
[
[
17] P. Metrangolo, F. Meyer, T. Pilati, G. Resnati, G. Terraneo, Angew.
Chem. Int. Ed. 2008, 47, 6114-6127.
[
3]
a) A. T. Aron, M. C. Heffern, Z. R. Lonergan, M. N. Vander Wal, B. R.
Blank, B. Spangler, Y. Zhang, H. M. Park, A. Stahl, A. R. Renslo, Proc.
Natl. Acad. Sci. U.S.A. 2017, 114, 12669-12674; b) A. Sargenti, G.
Farruggia, N. Zaccheroni, C. Marraccini, M. Sgarzi, C. Cappadone, E.
Malucelli, A. Procopio, L. Prodi, M. Lombardo, Nat. Protoc. 2017, 12,
18] P. Politzer, P. Lane, M. C. Concha, Y. Ma, J. S. Murray, J. Mol. Model.
2
007, 13, 305-311.
19] Y. Lu, Y. Liu, Z. Xu, H. Li, H. Liu, W. Zhu, Expert Opin. Drug Discov.
012, 7, 375-383.
20] a) A. V. Jentzsch, A. Hennig, J. Mareda, S. Matile, Acc. Chem. Res.
2
4
8
8
61-471; c) W. Zhou, R. Saran, J. Liu, Chem. Rev. 2017, 117, 8272-
325; d) Z. Hao, R. Zhu, P. R. Chen, Curr. Opin. Chem. Biol. 2018, 43,
7-96.
2
013, 46, 2791–2800; b) A. V. Jentzsch, S. Matile, Top. Curr. Chem.
015, 358, 205-239. c) C. Ren, X. Ding, A. Roy, J. Shen, S. Zhou, F.
2
Chen, S. F. Y. Li, H. Ren, Y. Y. Yang, H. Zeng, Chem. Sci. 2018, DOI:
0.1039/C8SC00602D.
[
4]
a) Q. Chen, C. Liang, X. Sun, J. Chen, Z. Yang, H. Zhao, L. Feng, Z.
Liu, Proc. Natl. Acad. Sci. U.S.A. 2017, 114, 5343-5348; b) D. Cheng, Y.
Pan, L. Wang, Z. Zeng, L. Yuan, X. Zhang, Y.-T. Chang, J. Am. Chem.
Soc. 2016, 139, 285-292; c) X. Bai, Y. Huang, M. Lu, D. Yang, Angew.
Chem. Int. Ed. 2017, 56, 12873-12877; d) J. J. Hu, N.-K. Wong, S. Ye,
X. Chen, M.-Y. Lu, A. Q. Zhao, Y. Guo, A. C.-H. Ma, A. Y.-H. Leung, J.
Shen, J. Am. Chem. Soc. 2015, 137, 6837-6843; e) L. Wu, I.-C. Wu, C.
C. DuFort, M. A. Carlson, X. Wu, L. Chen, C.-T. Kuo, Y. Qin, J. Yu, S.
R. Hingorani, J. Am. Chem. Soc. 2017, 139, 6911-6918.
1
[
[
21] a) T. Eneqvist, E. Lundberg, A. Karlsson, S. Huang, C. R. Santos, D. M.
Power, A. E. Sauer-Eriksson, J. Biol. Chem. 2004, 279, 26411-26416;
b) S. Mondal, K. Raja, U. Schweizer, G. Mugesh, Angew. Chem. Int. Ed.
2016, 55, 7606-7630.
22] a) C. Lee, W. Yang, R. G. Parr, Phys. Rev. B 1988, 37, 785; b) A. D.
Becke, J. Chem. Phys. 1993, 98, 5648-5652; c) M. J. Frisch, et. al.
Gaussian Inc., Wallingford CT, 2004; d) M. J. Frisch, et. al. Gaussian
Inc., Wallingford CT, 2009.
[
[
5]
6]
S. T. Manjare, Y. Kim, D. G. Churchill, Acc. Chem. Res. 2014, 47,
[
[
23] a) E. D Glendening, J. E. Reed, J. E. Carpenter, F. Weinhold, NBO
Program 3.1; Madison, WI, 1988; b) A. E. Reed, L. A. Curtiss, F.
Weinhold, Chem. Rev. 1988, 88, 899-926.
2985-2998 and references therein.
a) R. M. Duke, E. B. Veale, F. M. Pfeffer, P. E. Kruger, T.
Gunnlaugsson, Chem. Soc. Rev. 2010, 39, 3936-3953; b) K. G. Leslie,
D. Jacquemin, E. J. New, K. A. Jolliffe, Chem. Eur. J. 2018, 24, 1-6.
Y. Tang, X. Kong, A. Xu, B. Dong, W. Lin, Angew. Chem. Int. Ed. 2016,
24] E. Diamanti-Kandarakis, J.-P. Bourguignon, L. C. Giudice, R. Hauser,
G. S. Prins, A. M. Soto, R. T. Zoeller, A. C. Gore, Endocr. Rev. 2009,
[
[
7]
8]
30, 293-342.
55, 3356-3359.
H. Yu, Y. Xiao, L. Jin, J. Am. Chem. Soc. 2012, 134, 17486-17489.
This article is protected by copyright. All rights reserved.

Angewandte Chemie International Edition
10.1002/anie.201804128
COMMUNICATION
Entry for the Table of Contents
COMMUNICATION
The introduction of halogen
atoms enhances the cellular
uptake of fluorescent
molecules, providing a novel
strategy for the transport of
organic molecules across the
plasma membrane in living
cells.
Harinarayana Ungati,
Vijayakumar Govindaraj,
Govindasamy Mugesh*
Page No. – Page No.
Remarkable Effect of
Halogen Substitution on the
Membrane Transport of
Fluorescent Molecules in
Living Cells
This article is protected by copyright. All rights reserved.