Glycodynamers: Dynamic polymers bearing oligosaccharides residues - Generation, structure, physicochemical, component exchange, and lectin binding properties

Article abstract of DOI:10.1021/ja9082733

Dynamic glycopolymers have been generated by polycondensation through acylhydrazone formation between components bearing lateral bioactive oligosaccharide chains. They have been characterized as bottlebrush type by cryo-TEM and SANS studies. They present remarkable fluorescence properties whose emission wavelengths depend on the constitution of the polymer and are tunable by constitutional modification through exchange/Incorporation of components, thus also demonstrating their dynamic character. Constitution-dependent binding of these glycodynamers to a lectin, peanut agglutinin, has been demonstrated.

Full text of DOI:10.1021/ja9082733

Published on Web 02/05/2010
Glycodynamers: Dynamic Polymers Bearing Oligosaccharides
Residues - Generation, Structure, Physicochemical,
Component Exchange, and Lectin Binding Properties
Yves Ruff,† Eric Buhler,‡ Sauveur-Jean Candau,† Ellina Kesselman,§
Yeshayahu Talmon,§ and Jean-Marie Lehn*,†
Laboratoire de Chimie Supramole´culaire, ISIS, UniVersite´ de Strasbourg, Alle´e Gaspard Monge,
67000 Strasbourg, France, Laboratoire Matie`re et Syste`mes Complexes (MSC), UMR CNRS
7057, Baˆtiment Condorcet, UniVersite´ Paris Diderot-Paris 7, 75205 Paris cedex 13, France, and
Department of Chemical Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel
Received October 7, 2009; E-mail: lehn@isis.u-strasbg.fr
Abstract: Dynamic glycopolymers have been generated by polycondensation through acylhydrazone
formation between components bearing lateral bioactive oligosaccharide chains. They have been
characterized as bottlebrush type by cryo-TEM and SANS studies. They present remarkable fluorescence
properties whose emission wavelengths depend on the constitution of the polymer and are tunable by
constitutional modification through exchange/incorporation of components, thus also demonstrating their
dynamic character. Constitution-dependent binding of these glycodynamers to a lectin, peanut agglutinin,
has been demonstrated.
Constitutional dynamic chemistry (CDC)1 rests on the
implementation of reversible chemical connections of either
covalent or noncovalent nature linking the components of a
molecular or supramolecular entity. As a consequence, consti-
tutionally dynamic entities are able to continuously modify their
constitution by assembly disassembly of their building blocks,
thus generating a mixture of interconvertible species, a dynamic
set of constituents, a constitutional dynamic library1 (CDL).
A CDL is also combinatorial, as all possible combinations
of the initial building blocks may form in proportions specific
to the thermodynamic equilibrium of the system.2-4 Disruption
of this equilibrium by physical or chemical factors may lead to
adaptation through amplification of one or more constituents
of the library by rearrangement of its components. This approach
was used successfully, for example, for the discovery of
biologically active substances selected by the biological target
itself under the pressure of recognition.5
after polymerization. These modifications can be triggered by
physical stimuli or chemical effectors like temperature,8 or
addition of protons9 or of metal cations.10-12 Dynamers are thus
smart, adaptive materials. Moreover, changes in the molecular
constitution of the polymer can induce a modification of the
properties (such as mechanical13 or optical10,12,14) of the
material.
Dynamers based on components of biological nature may
generate dynamic analogues of natural polymers, biodynamers,
that offer the possibility to combine the functional properties
(recognition, catalysis) of naturally occurring polymers with the
adaptive behavior of constitutional dynamic systems. Therefore,
in view of the prospects offered, the incorporation of biologically
relevant moieties into dynamic polymers deserves close
scrutiny.15-18
In addition to proteins and nucleic acids, polysaccharides
represent a third class of biopolymers. Oligo- and polysaccha-
rides are involved in a wide range of biological or pathological
events like immune response, inflammation, cancer, cell adhe-
The implementation of CDC in material science, in particular
in polymer chemistry, led to the introduction of the notion of
dynamic polymers, dynamers that result from the reversible
connection of monomers via either covalent or noncovalent
linkages.6-8 Such equilibrium polymers present the ability to
undergo changes in their constitution, length, and sequence even
(8) Yamaguchi, G.; Higaki, Y.; Otsuka, H.; Takahara, A. Macromolecules
2005, 38, 6316–6320.
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11449.
† Universite´ de Strasbourg.
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(12) Giuseppone, N.; Fuks, G.; Lehn, J.-M. Chem.-Eur. J. 2006, 12, 1723–
1735.
‡ Universite´ Paris Diderot-Paris 7.
§ Technion-Israel Institute of Technology.
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A R T I C L E S
Ruff et al.
sion, or cell-cell recognition.19-21 These recognition processes
involve in particular carbohydrate-protein interactions. As the
interaction of a single saccharide with its receptor is generally
weak, biology uses multivalency to enhance the binding
efficiency.22 The oligosaccharides involved in recognition
processes are generally clustered, displayed in a multivalent
fashion, at the surface of cells or bacteria.23 It is therefore of
much interest to design synthetic analogues of these natural
multivalent assemblies to mimic, or even improve over, their
native properties.24
One possible approach consists of conjugating carbohydrate
residues to a polymerizable scaffold.25 Glycoclusters have been
obtained by appending saccharide residues to branched26 or
hyperbranched polymers,27 ꢀ-cyclodextrin,28,29 and calixarene
cores.30 Other approaches involve, for instance, combinatorial
glycosamino acids31 and oligosaccharide32 derivatives, dynamic
monolayers,33 a polyrotaxane,34,35 and self-assembling glyco-
dendrimers.36
Extending our work on dynamers6,7 to the biopolymer
area,16-18 we were interested in designing dynamic analogues
of glycopolymers, glycodynamers. Such dynamic or equilibrium
polymers could provide, in addition to potential biorecognition
properties, an adaptive character that would enable them to
reorganize their sequence or constitution so as to select the
preferential/optimal sequence, nature, and proportion of the
bioactive monomeric subunits, in response to external physical
stimuli or chemical effectors (temperature, pH, etc.) or to the
presence of a (bio)chemical target template.
Figure 1. Molecular structures of the bis-hydrazides 1a,b and of the
dialdehydes 2a,b and 3.
the preparation of dynamic analogues of oligoarabinofura-
noses,17 multiple saccharide presentation,37-39 and in glycob-
lotting.40
Polymers incorporating carbohydrate-based monomers have
been obtained by poly(acylhydrazone)41,42 and polyoxime43
formation. Ditopic saccharide monomers yield reversible poly-
mers with a bis-boronic acid,15 and a dynamic library of cyclic
sugar oligomers has been generated via acylhydrazone forma-
tion.44
Such biodynamers may be of three types: (1) main chain,
resulting from polycondensation of saccharide residues through
reversible reactions; (2) side chain, where the saccharide residues
are either (a) appended on a dynamic main chain or (b)
reversibly grafted on a nondynamic main chain; and (3) “doubly
dynamic”, incorporating both main-chain and side-chain dynamics.
We present here our results on the generation of glycody-
namers of type (2)(a) (vide supra), that is, a nonglycosydic
dynamic main chain bearing lateral carbohydrate residues. We
also report their remarkable physical and optical properties, the
dynamic modulation of the latter, as well as their constitution-
dependent binding to a lectin.
Of special interest, as reversible condensation reaction, is the
formation of an imine-type double bond from an amino group
and a carbonyl group. Thus, oxime formation has been used in
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Molecular Design of the Monomers
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The monomers 1-3 were chosen so as to contain structurally
diverse aromatic cores to ensure a wide range of properties for
the different monomer combinations, allowing one to follow
the polymer compositions by various spectroscopic methods
such as NMR, UV, or fluorescence spectroscopy.
The starting monomers consist of aromatic bis-hydrazide 1a,
1b, and dialdehyde 2a, 2b, decorated by oligosaccharide groups
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Glycodynamers: Polymers Bearing Oligosaccharides Residues
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Figure 2. Synthesis of monomer 1a: (a) 1,3 propanediol, PPh3, DIAD, THF, 67%; (b) (i) I2, Ac2O, (ii) HClO4, Ac2O, quant.; (c) piperidine, THF, 70%; (d)
trichloroacetonitrile, DBU cat., CH2Cl2, 64%; (e) 5, BF3OEt2, CH2Cl2, -20 °C, 39.5%; (f) KCN, MeOH, 67%; (g) NH2NH2 monohydrate, MeOH, 68%.
deprotection of the anomeric hydroxyl group of 6 giving 7 and
activation of the resulting free alcohol to yield the glycosyl donor
8. 8 is then subjected to a glycosylation using Schmidt’s method
with the alcohol 5, which was itself obtained by a Mitsunobu
reaction between 4 and 1,3-propandiol. Deprotection of 9 followed
by reaction with hydrazine gave 1a (Figure 2).
The synthesis of dialdehyde 2b involved the BF3 ·OEt2-catalyzed
glycosylation of the protected lactose derivative 11 with the known
alcohol 12.55 12 was then deprotected to yield 2b (Figure 3).
The preparation of monomers 1b and 2a was achieved by
alkylation of the aromatic units 1656 and 1757 using the iodide 15
obtained from the bromide 1458 by a Finkelstein halide exchange
reaction. This iodide was then used to introduce a protected lactosyl
unit in a single step (Figure 3).
(Figure 1). Monomer 1a bears the maltohexaose moiety, derived
from R-cyclodextrin, chosen to confer a well-defined secondary
structure to the resulting polymer. Such a long hydrophilic side
chain conjugated to an hydrophobic aromatic main chain could
be expected to result in the formation of a bottlebrush-like
species,45 similar to a cylindrical micelle that would be stabilized
via reversible covalent bonds.
Monomers 1b, 2a, and 2b present the lactose moiety that is
one of the natural ligands for galectins. These carbohydrate-
binding proteins are involved in cell adhesion, inflammation,
and cancer.46,47 Therefore, tools for profiling or binding this
type of lectins are needed to understand their biological
functions. Furthermore, lactosyl and galactosyl glycopolymers
have applications for Shiga toxin 1 binding,48 and cell-specific
gene49-51 or drug delivery,52,53 due to their ability to use lectin
binding to enhance endocytosis.
The monomer 3 was prepared starting from 2,5-anhydromannitol.
After a selective protection-deprotection sequence, the known diol
Materials and Methods
Materials Synthesis. The synthesis54 of 1a starts with the
acetolytic cleavage of R-cyclodextrin, followed by a selective
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285–293.
(54) The synthesis and characterization of every new compound is detailed
in the Supporting Information.
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2001, 11, 1507–1509.
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K. A.; Tidwell, R. R. Eur. J. Med. Chem. 1997, 32, 781–793.
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2007, 67, 260–264.
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Ruff et al.
Figure 3. Synthesis of monomers 1b, 2a, 2b: (a) BF3OEt2, CH2Cl2, reflux, the product was used directly for the next step; (b) NEt3/MeOH/H2O 8/58/24,
13% over two steps; (c) NaI, acetone, reflux; (d) K2CO3, 18-Crown-6, DMF, 40 °C, 48H, 79%; (e) KCN cat., MeOH, 77%; (f) NH2NH2 monohydrate,
MeOH, 74%; (g) K2CO3, 18-Crown-6, DMF, 45 °C, 20H, 60%; (h) NEt3/MeOH/H2O 8/58/24, 76%; (i) (i) TrCl, pyridine, (ii) BzCl, pyridine, (iii) AcOH,
H2O; (j) (i) TEMPO, trichloroisocyanuric acid, (ii) CH(OMe)3, MeOH, p-toluene sulfonic acid, 53% over two steps; (k) NaOMe, MeOH, 80%; (l) pD < 1,
DCl, 50 °C, 24 h, D2O, quant.
2259 was oxidized, and the resulting aldehyde was protected as the
dimethylacetal 23. Removal of the benzoyl protecting groups yields
24. The aliphatic dialdehyde 3 was obtained after hydrolysis of 24
(Figure 3).
4.23 × 10-2 e q e 4.35 × 10-1 Å-1, 1.7 × 10-2 e q e 1.79 ×
10-1 Å-1, and 3.2 × 10-3 e q e 3.4 × 10-2 Å-1. Measured
intensities were calibrated to absolute values (cm-1) using normal-
ization by the attenuated direct beam classical method. Standard
procedures to correct the data for the transmission, detector
efficiency, and backgrounds (solvent, empty cell, electronic, and
neutronic background) were carried out. The scattered wavevector,
q, is defined by eq 1, where θ is the scattering angle.
NMR Spectroscopy. 1H and 13C NMR measurements were
conducted on a Bruker Advance 400 MHz spectrometer. Chemical
shifts are referenced with residual solvent signal (7.26 ppm, 77.16
t
ppm) in CDCl3, BuOH (1.24 ppm, 70.36 ppm, 30.29 ppm), or
MeOH (3.34 ppm, 49.5 ppm) in D2O.
4π
λ
θ
2
Fluorescence Spectroscopy. Fluorescence measurements were
done on a Jobin-Yvon Horiba Fluorolog 3.22 spectrometer.
Small-Angle Neutron Scattering (SANS). SANS experiments
were carried out on the PACE spectrometer in the Le´on Brillouin
Laboratory at Saclay (LLB, France). The chosen incident wave-
length, λ, depends on the set of experiments, as follows. For a given
wavelength, the range of the amplitude of the transfer wave vector,
q, was selected by changing the detector distance, D. Three sets of
sample-to-detector distances and wavelengths were chosen (λ )
4.5 Å, D ) 1 m; λ ) 6 Å, D ) 1.85 m; and λ ) 13 Å, D )
4.67 m) so that the following q-ranges were respectively available:
q )
sin
(1)
The usual equation for absolute neutron scattering combines the
intraparticle scattering S1(q) ) VchainφvolP(q) form factor with the
interparticle scattering S2(q) factor:
1 dσ
V dΩ
I(q)(cm-1) )
) (∆F)2(S1(q) + S2(q))
(2)
) (∆F)2(VchainφvolP(q) + S2(q))
where (∆F)2 ) (Fmonomer - Fsolvent)2 is the contrast per unit volume
between the polymer and the solvent, which was determined from
the known chemical composition. F ) ∑nibi/(∑nimiV × 1.66 ×
(59) Kuszmann, J.; Medgyes, G.; Boros, S. Carbohydr. Res. 2005, 340,
1739–1749.
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Glycodynamers: Polymers Bearing Oligosaccharides Residues
A R T I C L E S
10-24) represents the scattering length per unit volume; bi is the
neutron scattering length of the species i, mi is the mass of species
i, and V is the specific volume of the monomer (which has been
measured on a helium pycnometer for 1a (0.629 cm3/g) and 2b
(0.7 cm3/g)) or the solvent (i.e., 0.9026 cm3/g for D2O). P(q) is the
form factor, Vchain ) NVm × 1.66 × 10-24 is the volume of N
monomers (of mass m) in a chain, and φvol is the volume fraction
of monomer. In the high q-range, the scattering is assumed to arise
from isolated chains, that is, S2(q) ) 0, and thus I(q) ∝ P(q).
GPC Measurements. GPC was performed on an Agilent 1100
Series GPC-SEC Analysis System equipped with three serial
Shodex OH-pak (30 cm) columns (1803HQ, 1804HQ, 1806HQ)
and a guard column. Detection was performed by a differential
refractometer OPTILAB rEX (Wyatt Techn.) and a multi-angle light
scattering detector DAWN HELEOS (Wyatt Techn). The injected
volume was 100 mL. The flow rate was 0.5 mL/min, and the eluent
was high-purity Millipore quality water containing 0.1 M NaNO3
and NaN3.
Cryo-TEM Analysis. Vitrified specimens for cryogenic-tem-
perature transmission electron microscopy (Cryo-TEM) were
prepared in a controlled environment vitrification system (CEVS)
at 25 °C and 100% relative solvent saturation, as previously
described.60,61 In brief, a drop of the solution to be imaged was
applied onto a perforated carbon film, supported on an electron
microscopy copper grid, held by the CEVS tweezers. The sample
was blotted by filter paper and immediately plunged into liquid
nitrogen (-196 °C). The vitrified samples were then stored under
liquid nitrogen, transferred to a Gatan 626 cooling holder via its
“workstation”, and kept in a FEI T12 G2 microscope at about -180
°C. Images were recorded at 120 kV acceleration voltage, in the
low-dose mode, to minimize electron-beam radiation-damage. We
used a Gatan UltraScan 1000 high-resolution cooled-CCD camera,
with the Digital Micrograph software package, to acquire the
images. Images were recorded at nominal underfocus of about 1-2
µm to enhance phase contrast.
SPR Measurements. Surface plasmon resonance experiments
were performed on a BIAcore 2000 (Biacore technology, Biacore
AB, Uppsala, Sweden). The peanut agglutinin lectin was im-
mobilized on the carboxylated sensor surface by a standard EDC
(N-ethyl-N′-(3-dimethylaminopropyl)carbodiimide hydrochloride)/
N-hydroxysuccinimide protocol. 10 and 20 µL of a PNA solution
(100 µg mL-1, 50 mM phosphate buffer pH ) 6, 154 mM NaCl)
were injected trough two of the chip channels, resulting in the
immobilization of, respectively, 1408 and 3000 refractive unit (RU)
of the protein on the surface. After immobilization, the remaining
reactive activated carboxylic acids were capped with an ethanol-
amine solution.
1
1
Figure 4. (A) H NMR (D2O, 400 MHz, 298 K) of monomer 1a. (B) H
1
NMR (D2O, 400 MHz, 298 K) of monomer 2b. (C) H NMR (D2O, 400
MHz, 298 K) of polymer 1a2b with an initial monomer concentration of
10 mM, at pD ) 4. (D) 1H NMR (DMSO-d6/D2O 5/1) obtained after dilution
of 100 µL of the above polymer 1a2b solution in 500 µL of DMSO-d6.
The proton numbering for signal attribution is shown in Figure 5.
visibility, whereas those of the flexible saccharide side chains
are still observable. This feature clearly indicated that the
polycondensation and the expected micellar folding took place,
but precluded the direct observation of imines signals that are
generally well-defined individual singlets. Destabilization of
hydrophobic forces should prevent the collapse of the hydro-
phobic main chain, which consequently should gain mobility,
and therefore allow circumventing this problem. To achieve this
“denaturation”, we chose to use DMSO, an aprotic polar solvent,
which, in principle, is able to dissolve both the lateral oligosac-
charides chains and the aromatic core residues. Indeed, addition
of d6-DMSO to an aqueous solution of polymer 1a2b allowed
us to assign62 and integrate all signals attributed to the aromatic
main chain of the polymer. In the 1H NMR spectrum (DMSO-
d6/D2O 4/1) of the polymer 1a2b, the signals corresponding to
the imine (8.34 ppm), aromatic dialdehyde (7.71 and 7.04 ppm),
and dihydrazide monomer (7.95 and 7.58 ppm) could be clearly
assigned. No free monomer was detected (Figures 4 and 5). A
similar behavior was observed for the polymers 1b2b and 1a3,
suggesting for both of them a reversible micellar folding of the
polymer backbone that can be circumvented by addition of
DMSO.63
Results and Discussion
Characterization of Glycopolymers 1a2a, 1a2b, 1b2a,
1b2b, and 1a3. A. NMR Characterization of the Glycopolymers.
The five possible glycodynamers 1a2a, 1a2b, 1b2a, 1b2b, and
1a3 were obtained by polycondensation of a diluted solution
of dialdehyde 2a,b or 3 and dihydrazide 1a,b monomers in D2O
(10 mM) under mild acidic conditions, typically pD ) 4-6.
As the chemical shifts of imines proton signals are sensitive
to small structural variations, it was hoped that each polymer
1
would have a specific H NMR signature in the imine region.
Yet in all cases polymerization was associated with a dramatic
broadening of the aromatic main chain signals, which may be
interpreted in terms of a reduction of the mobility of these
molecular segments in the polymeric structure (Figure 4). The
proton NMR signals of the main chain are broadened beyond
B. Cryo-TEM. Evidence in favor of a cylindrical micelle-
like conformation was provided by cryo-TEM images of
polymer 1a2b (Figure 6, left). This picture clearly shows thread-
(60) Talmon, Y. In Modern Characterization Methods of Surfactant
Systems; Binks, B. P., Ed.; Dekker: New York: 1999; p 147.
(61) Bellare, J. R.; Davis, H. T.; Scriven, L. E.; Talmon, Y. J. Electron
Microsc. Technique 1988, 10, 87–111.
(62) Complete assignation required 2D NMR experiments (COSY) and is
given in the Supporting Information.
(63) The effect of addition of DMSO on the NMR spectrum of these
polymers can be found in the Supporting Information.
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A R T I C L E S
Ruff et al.
Figure 5. Preparation of the dynamic glycopolymer 1a2b by polycondensation of monomers 1a and 2b. The corresponding proton NMR signals are shown
in Figure 4.
Figure 6. Left: Cryo-TEM image of a sample of polymer 1a2b prepared
in D2O with an initial monomers concentration of 5 mM in the presence of
a catalytic amount of d-TFA (5 mol %); 1, typical individual polymeric
filaments; 2, spherical aggregates. Right: Cryo-TEM image of a sample of
polymer 1a3 prepared in D2O, with an initial monomers concentration of
Figure 7. SANS scattered intensity as a function of q for polymer solutions
10 mM at pD ) 5; 3, typical 1a3 ellipsoidal structures. The scale bars
1a2b and 1a3 at pD ) 4 and 34 °C with an initial concentration of
correspond to 50 nm.
monomers of 5 mM.
The average diameter of the spherical aggregates is between
like polymeric structures, in addition to small spheroidal entities
40 and 50 Å. As monomers 1a and 2b are amphiphilic
molecules, this size could be consistent with the formation of
that could correspond to either free monomers aggregated into
small micelles or small cyclic oligomers. Some of these black
micelles composed of residual monomers or small cyclic
dots are in fact polymer filaments with their longitudinal axis
oligomers that would be present as traces in the polymerization
oriented perpendicular to the surface of the sample. Because of
mixture (these species were not detected by GPC,65 confirming
the thickness of the vitrified specimen, the length of the polymers
that their proportion is not significant). It is interesting to note
is not accessible using this technique; it nevertheless provides
that this bimodal distribution is unusual for equilibrium
a good approximation of the section of the polymer. The width
polymers.
of the filaments lies between 40 and 50 Å. As the length of the
For polymer 1a3 (Figure 6, right), the wormlike structures
oligosaccharide residues in an extended conformation should
observed in the case of 1a2b are absent, and only small
be 2.8 nm for 1a, and 1 nm for 2b,64 these dimensions are
ellipsoidal structures are observed. The average length of their
consistent with a honeycomb shape with the hydrophobic
longitudinal axis was measured to be 39 ( 5 Å, which is similar
polymer main chain bristling with lateral oligosaccharide chains.
to that of 1a2b, suggesting that, not unexpectedly, 1a dominates
In addition, these dimensions are in agreement with the expected
the section of 1a3.
diameter of a single polymer chain as reported for single
C. Small-Angle Neutron Scattering. To characterize in more
detail the conformation and length of the present type of
dynamic glycopolymers, we performed small-angle neutron
polystyrene chains decorated with similar oligosaccharides side
chains.45
(64) Values were determined using the commercial software Chem3D after
energy minimization using the MM2 computation model.
(65) The GPC profiles can be found in the Supporting Information.
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2578 J. AM. CHEM. SOC. VOL. 132, NO. 8, 2010

Glycodynamers: Polymers Bearing Oligosaccharides Residues
A R T I C L E S
scattering (SANS)66 on polymer 1a2b and 1a3 equilibrated for
72 h. Figure 7 displays the scattering pattern obtained for these
polymers. For 1a2b, the scattering curve exhibits an overall
behavior, characterized by the following sequence: a Guinier
regime in the low-q range, associated with the finite size of the
polymers, an intermediate regime in which the q-dependence
of the scattered intensity can be described by a power law with
an exponent equal to -1, followed by another Guinier regime
associated with the cross-section of the supramolecular poly-
mers. For polymers 1a3, one observes only one Guinier regime
associated with the mass and size of the system.
For polymer 1a2b, the absence of q-2-dependence of the
scattered intensity I(q), which would be characteristic of flexible
wormlike chains, and the q-1-dependence of I(q) just after the
Guinier regime indicate that this polymer may be considered a
rigid rod. The low-q 1a2b data corresponding to large spatial
scales can be fitted by the following Guinier expression, giving
the radius of gyration, Rg, of the polymer chains:
π
qL
2
P(q) )
+
(5)
3q2LpL
The fit shown in Figure 9 gives the following value for the linear
density, ML ) 744 g/mol/Å. From values of Mw and ML, one
obtains the contour length of polymers 1a2b: L ) Mw/ML ) 69
nm, a value in excellent agreement with that of 65 nm obtained
using the Benoit-Doty expression above.
For polymer 1a2b, similar results were obtained for all
temperatures and pD values investigated (Figure 8). As no
temperature or time dependence of the molecular weight was
observed by SANS experiments, the polymer 1a2b can be
considered as nondynamic at the time scale of these experiments
(24 h). However, over a period of 4 months, the molecular
weight of 1a2b was found to evolve slowly toward higher
masses by elongation of the individual polymer chains (see GPC
data below).
Finally, the high-q data can be fitted by a Guinier expression
for the form factor of the dynamic polymer section:
q2R2g
q2R2c
1
I(q)
1
I(0)
πS
q
)
1 +
(3)
(
)
VchainP(q) )
exp(-
)
(6)
3
2
From the best linear fit (see inset of Figure 9) to the data, one
obtains Rg ) 187 Å. The measurement of the radius of gyration,
Rg, can be expressed as a function of Lp, using the Benoit-Doty
expression derived for a wormlike chain of contour length, L,
without excluded volume interactions.67
where Rc is the radius of gyration of the cross-section. By fitting
the above equation to the experimental data, one can determine
the cross-section, S, and the radius of gyration of the cross-
section. From the fit of Figure 9, we obtain S ) 1300 Å2 and
Rc ) 17.3 Å for polymer 1a2b. As polymer 1a2b may be
considered a solid cylinder, d )ꢀ8Rc, which gives a section
diameter of 48.9 Å, in agreement with the cryo-TEM observations.
Similar SANS analyses were conducted on polymer 1a3,
yielding a radius of gyration, Rg, between 32 and 34 Å, with
small variations with temperature and pH, whereas polymer
1a2b showed no temperature dependence at all. It is thus much
shorter than the 187 Å Rg measured for 1a2b. In view of the
cryo-TEM data, 1a may be assumed to contribute mainly to
the cross-section of the polymers 1a2b and 1a3, which should
have similar cross-sections, so that an ellipsoidal model could
be used to calculate the longitudinal length of 1a3.
LLp
2L3p
2L4p
L2
-L
Lp
〈R2g〉 )
- L2p +
-
1 - exp
(4)
(
(
))
3
L
For rodlike particles with large aspect ratio, the average contour
length of the rod L , Lp, as shown by the cryo-TEM pictures
and the intermediate q-1 regime. Expression (4) simplifies then
to Rg ) L2/12, giving L. In the case of polymer 1a2b, one
2
obtains L ) 65 nm.
Neglecting the excluded volume interactions, the extrapolation
to zero-q of the scattered intensity, I(q2 ) 0), provides a measure
of the weight-average molecular weigth of the polymers, Mw
) [I(q ) 0) × NA]/[(∆F)2 × φvol × V], where (∆F)2 is the
contrast per unit volume between the polymer and the solvent,
which was determined from the known chemical composition.
NA is Avogadro’s number, φvol is the volume fraction of
monomers, and V is the specific volume of the monomer, which
has been measured to 0.66 cm3/g after determination of the
density for monomers 1a (d ) 1.59) and 2b (d ) 1.43) on a
helium pycnometer. The weight average molecular weight
measured for the sample 1a2b presented in Figure 9 is 511 000
g mol-1 corresponding to about 275 monomeric units with an
initial monomer concentration of 5 mM at pD ) 4, after 72 h
of equilibration.
The radius of gyration, Rg, for an ellipsoid, with radii a, b,
and c, and b ) c (ellipsoid of revolution), can be written:68 R2
g
) (b2/5) × (2 + a2/b2). Assuming that b ) d/2 ) 24.5 Å is
identical for both polymers 1a3 and 1a2b, we found a ) 61.9
Å, that is, an axial ratio of ∼2.5 for 1a3, explaining the absence
of the q-1 regime.
Similar Guinier analysis and I(q ) 0) extrapolation gave an
average molecular weight of 39 000 g mol-1 for 1a3, at pD )
5, with an initial concentration of monomers of 5 mM,
corresponding to 28 monomeric units.
D. Fluorescence Spectroscopy. In addition to SANS and cryo-
TEM data, other results support the bottle-brush secondary
structure of the polymers. Whereas among the monomers only
2a was significantly fluorescent, all four polymers displayed
remarkable fluorescence with a wide range of emission maxima
In the intermediate regime, I(q) is controlled by smaller
distances than Lp over which polymers 1a2b are rodlike, and
we observe a q-1-dependence for the form factor P(q), which
is typical for locally rod structures. In this regime, where I(q)
∝ P(q), the data can be fitted by the des Cloizeaux expression:
from blue for 1a2b (λmax ) 457 nm) to green for 1a2a (λmax
495 nm), 1b2b (λmax ) 499 nm), and to red for 1b2a (λmax
567 nm) (Figure 10, Table 1).
These fluorescence properties are likely to result from the
tightly packed structure of the polymer, where aromatic chro-
mophores are isolated in the hydrophobic core and rigidly held,
)
)
(66) Buhler, E.; Candau, S. J.; Schmidt, J.; Talmon, Y.; Kolomiets, E.;
Lehn, J.-M. J. Polym. Sci., Part B: Polym. Phys. 2007, 45, 103–115.
(67) Benoit, H.; Doty, P. J. Phys. Chem. 1953, 57, 958–963.
(68) Guinier, A.; Fournet, G. Small-Angle Scattering of X-rays; John Wiley
and Sons: New York, 1955.
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A R T I C L E S
Ruff et al.
Figure 10. (A) Photography of samples of the polymers 1a2b, 1a2a, 1b2b,
and 1b2a under UV irradiation (365 nm) in D2O at pD ) 4 with an initial
monomer concentration of 5 mM; (B) emission spectrum of the same
polymer samples (for polymer 1b2a, a slit width of 3 nm was used instead
of 1 nm for the others) irradiated at their respective maximum for excitation.
The excitation maxima are given in Table 1, and the excitation spectra are
shown in the Supporting Information.
Figure 8. Effect of the temperature on the small-angle neutron scattering
patterns for polymers 1a2b at a monomer concentration of 5 mM and pD
) 4.
Table 1. Optimal Wavelength for the Excitation (λmax ex) and
Emission (λmax em) of Glycopolymers 1a2a, 1a2b, 1b2a, and 1b2ba
1a2a
1a2b
1b2b
1b2a
λ
λ
max ex (nm)
max em (nm)
433
495
389
457
427
499
467
567
a Samples were prepared in D2O at pD ) 4 with an initial monomer
concentration of 5 mM.
unit found in monomer 1a. For polymer 1a2b, the fluorescence
intensity decreases markedly upon addition of DMSO to the
polymer solution, presumably due to the destabilization of
the highly packed structure (Figure 11), further supporting the
influence of intramolecular motions and presumably stacking
interactions in the fluorescence properties of our polyhydra-
zones.74 The decrease in fluorescence intensity upon heating
also suggests an increase in molecular motion of the conjugated
aromatic core of the polymer. This phenomenon is well-known
for fluorophores and usually results in a loss of fluorescence of
1% when the temperature increases by 1 °C.75 However, in our
case, the nonlinear dependence between the fluorescence
intensity and the temperature suggests that an additional
phenomenon such as a denaturation or change in conformation
occurs.
E. GPC Measurements. GPC measurements were conducted
using water as solvent. Table 2 is a compilation of results
obtained for 1a2a, 1a2b, 1b2a, and 1b2b for samples equili-
brated on different time scales.
Polymers 1a2a and 1a2b display very high molecular weights
(>500 000 g/mol), which is already an interesting property,
considering the facile preparation procedure of these water-
soluble glycopolymers. Their radius of gyration, Rg, was
measured by light scattering at the output of the GPC column
and plotted against the determined molecular weight. A perfectly
linear dependence was observed in both cases, confirming their
rodlike character as Rg ) L/ꢀ12 for rigid rodlike chains (Figure
12).
Figure 9. SANS spectra obtained for a 5 mM solution of 1a2b in D2O at
T ) 57 °C and pD ) 4. The black line represents the fit of the data in the
intermediate regime with eq 5, and the dashed red line represents the fit of
the high q data by a Guinier expression for the form factor of the section
(eq 6). The linear correlation between I(q)-1 and q2 is represented in the
inset.
preventing nonradiative decay processes. Therefore, the collapse
of the aromatic units of polymer backbone during the formation
of the cylindrical micellar structure resulted in a dramatic
increase in their fluorescence emission efficiency. Such ag-
gregation-induced emission enhancement (AIEE)69,70 phenom-
ena have already been reported for different aromatic systems
and have been attributed in particular to the restriction of
intramolecular rotations. In our case, we can therefore imagine
a similar scenario, where the reduction of the intramolecular
rotations of the conjugated aromatic hydrazones units of the
polymer backbone would result in an increase in fluorescence
emission of these fluorophores. The contribution of stacking
interactions (H- or J-type) could also be considered,71-73 as
reported for isophthalic acid bis-amide derivatives,73 a structural
(71) Zhou, T.; Li, F.; Fan, Y.; Song, W.; Mu, X.; Zhang, H.; Wang, Y.
Chem. Commun. 2009, 3199–3201.
(72) Rabinowitch, E.; Epstein, L. F. J. Am. Chem. Soc. 2002, 63, 69–78.
(73) Qian, Y.; Li, S.; Zhang, G.; Wang, Q.; Wang, S.; Xu, H.; Li, C.; Li,
Y.; Yang, G. J. Phys. Chem. B 2007, 111, 5861–5868.
(74) Shimojo, S.; Cho, C.-S.; Park, I.-K.; Kunou, M.; Goto, M.; Akaike,
T. Carbohydr. Res. 2003, 338, 2129–2133.
(69) Luo, J.; Xie, Z.; Lam, J. W. Y.; Cheng, L.; Chen, H.; Qiu, C.; Kwok,
H. S.; Zhan, X.; Liu, Y.; Zhu, D.; Tang, B. Z. Chem. Commun. 2001,
1740–1741.
(70) Hong, Y.; Lam, J. W. Y.; Tang, B. Z. Chem. Commun. 2009, 4332–
(75) Guilbault, G. G. Practical Fluorescence, 2nd ed.; Marcel Dekker Inc.:
New York, 1990; pp 28-29.
4353.
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Glycodynamers: Polymers Bearing Oligosaccharides Residues
A R T I C L E S
Figure 11. (A) Effect of temperature on the fluorescence intensity of a sample of 1a2b in D2O, at pD ) 4 with an initial monomer concentration of 5 mM.
(B) Effect of DMSO addition on the fluorescence intensity of a sample of 1a2b (1) in D2O, at pD ) 4 with an initial monomer concentration of 5 mM; (2)
after dilution of this solution (100 µL) in D2O (500 µL); and (3) after dilution of this solution (100 µL) in DMSO-d6 (500 µL).
Table 2. GPC Determination of the Molecular Weight of
linkage. The living character of the polycondensation could also
explain the low polydispersities observed for polymers 1b2a
Glycopolymers 1a2a, 1a2b, 1b2a, and 1b2ba
1a2a
1a2b
1b2b
1b2a
(1.07) and 1b2b (1.31). It has been shown that low polydis-
persity can be achieved by polycondensation if the polymeri-
zation has a living character and proceeds through a chain
growth mechanism.76 This approach was used to prepare
polymers having polydispersity lower than 1.1, when classical
step growth polycondensation yields polymers having polydis-
persities closer to 2,77 as observed in our case for polymers
1a2a and 1a2b. The difference in polydispersity between
polymers derived from 1a or 1b could then result from a
different polymerization mechanism. Such a difference could
result from a particular folding or conformation, possibly
helicoidal,78 of the main chain of polymers 1b2a and 1b2b,
which would induce a strong cooperative polymerization,
making the chain elongation faster and more favorable than the
initiation of the growth of new polymer chains by the condensa-
tion of monomers.78,79 This hypothesis is supported by the fact
that even the addition of DMSO was not able to unfold the
polymer main chain for 1b2a.80
Mw (g mol-1
)
1.38 × 106
6.45 × 105
2.15
1.76 × 106
5.93 × 105
2.96
4.93 × 104
3.74 × 104
1.31
3.32 × 104
3.10 × 104
1.07
Mn (g mol-1
Mw/Mn
)
a Samples were prepared in D2O at pD ) 4 with an initial monomer
concentration of 5 mM.
The difference between the Mw values determined for 1a2b
by GPC and SANS could be due to the fact that the analysis of
GPC results implied the use of a dn/dc value, which was not
measured but taken arbitrarily. SANS does not require this
approximation and is therefore believed to be more accurate in
the present case.
Figure 12. Linear relations between the molecular mass and the radius of
gyration of polymers 1a2a, equilibrated 4 months, and 1a2b for samples
equilibrated 4 months, 672 h, and 72 h, as determined by light scattering
analysis of the GPC fractions.
1H NMR Study of the Dynamic Character of Polymer
1a2b. Demonstration of the dynamic character of the present
glycopolymers was achieved by adding an equimolar amount
of the dihydrazide monomer 1b to the polymer 1a2b, and
monitoring its incorporation into the backbone of the polymeric
Another feature of these dynamic polymers is that their
“living” character drives the polymerization toward the forma-
tion of increasingly long polymers over time. Indeed, after 4
months of equilibration, polymer 1a2b reached a molecular
weight of 1.76 × 106, whereas after 72 and 672 h of
equilibration, the observed Mw was 8.45 × 105 and 1.28 × 106
g mol-1, respectively. Thus, the molecular weight, and therefore
the length of this polymer, is time dependent. Within the
experimental error bar, the overlap of the dependence between
Rg and Mw for these three samples confirms a linear growth
and rules out the possibility of lateral aggregation (Figure 12).
This can be explained by considering that under the conditions
of equilibration, the polycondensation reaction can still take
place, and even if free monomers are absent, the reactive chain-
end hydrazide or aldehyde is still able to form the hydrazone
1
structure using H NMR (Figures 13 and 14).
The proton signals corresponding to the aromatic region of
the polymer are extremely broad, but, as during exchange 1b
replace 1a in the polymer, the release of the latter in solution
was indicated by the appearance of sharp peaks for its aromatic
and anomeric protons (Figure 13).
(76) Yokozawa, T.; Yokoyama, A. Prog. Polym. Sci. 2007, 32, 147–172.
(77) Flory, P. J. J. Am. Chem. Soc. 1936, 58, 1877–1885.
(78) Folmer-Andersen, J. F.; Lehn, J.-M. Angew. Chem., Int. Ed. 2009,
48, 7664–7667.
(79) Zhao, D.; Moore, J. S. Org. Biomol. Chem. 2003, 1, 3471–3491.
(80) The effect of addition of DMSO on the NMR spectrum of this polymer
can be found in the Supporting Information.
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A R T I C L E S
Ruff et al.
1a2b and 1b by fluorescence spectroscopy. Figure 15 shows
the evolution of the fluorescence spectrum of polymer 1a2b
mixed with an equivalent of dihydrazide monomer 1b. The
emission maximum shifts from blue to green due to the
incorporation of the new dihydrazide 1b building block into
the polymer, transforming progressively the polymer constitution
from 1a2b into 1a1b2b, containing increasing amounts of 1b
at the expense of 1a (see also Figure 10 and text).
It is of interest to note that these component exchange features
together with the wide range of emission wavelengths (see
above) suggest the possibility to modulate and tune the
fluorescent properties of the system via the introduction of
various components into the dynamic main chain. One may
imagine a number of applications of such optodynamers14 as
adaptive fluorescent probes and effector responsive optical
materials.
Improvement of Covalent Exchange Kinetics. Implementation
of the adaptive character of these dynamic polymers for
biological applications would require finding milder conditions
for the covalent exchange reactions, with exchange half times
in the order of hours or less at room temperature. To achieve
this goal, we chose to decrease the formation efficiency of the
imine linkage by using the strongly hydrated dialdehyde
monomer 3.
Figure 13. Part of the 1H NMR spectra of a mixture of a solution of
polymer 1a2b in pD ) 4 buffered D2O, (A) before and (B) after addition
of 1 equiv of 1b and heating at 80 °C for 70 min. 1,2,3 designate the
aromatic (1,2) and anomeric (3) signals of 1a released from 1a2b due to
the incorporation of 1b.
The polymer 1a3 was prepared from equimolar amounts of
1a and 3 (5 mM each pD ) 4). It had a fluorescence profile
similar to that of 1a2b with λmax ) 444 nm for emission and
383 nm for excitation.
As for the 1a2b polymer, the reversible character of 1a3 was
demonstrated by adding 1 equiv of the dihydrazide 1b to its
equilibrated form in aqueous solution and following the covalent
1
exchange reaction by H NMR (Figure 16).
The release of free 1a was again observed and quantified by
integration of the signal corresponding to its two equivalent
aromatic protons in DMSO-d6/D2O 5/1 (Figure 16). The half-
life for exchange at pD ) 6 was 34 and 12 min at pD ) 5 at
room temperature with an initial concentration of monomers
of 10 mM, that is, about 125 times faster than in the case of
1a2b at pD ) 4.
The incorporation of 1b into the polymers 1a2b and 1a3
demonstrates their dynamic nature and results in a modification
of their constitution, which markedly affects their structural and
functional properties.
Figure 14. Part of the 1H NMR spectra of a mixture obtained by dilution
of 100 µL of a solution of polymer 1a2b with 500 µL of DMSO-d6, (A)
before and (B) after addition of 1 equiv of 1b. The signals 1-5 correspond
to the polymer 1a2b and 6-8 to 1a released after exchange. Signals 1 and
6 are due to the imines protons, respectively, before and after exchange.
Lectin Binding Properties of the Glycodynamers. Surface
plasmon resonance (SPR) is a valuable tool for the rapid
determination of kinetic and thermodynamic binding parameters
between molecules or macromolecules, especially between
carbohydrates and lectins.81 After immobilization of the protein
of interest on a surface, the potential ligand is allowed to interact
with the receptor as its solution flows over the surface. The
refractive index of the surface changes according to the mass
of molecules bound to the surface and the receptor and can
therefore be used to quantify the binding efficiency.
We used peanut agglutinin, PNA, as a model lectin for the
preliminary investigations of the biological properties of our
polymers, because of its specificity for ꢀ-galactose ligands, and
especially for lactosyl units present in monomers 1b, 2a, and
2b.82,83
To be able to assign and integrate the aromatic and imine
signals, the aqueous polymer solution was diluted 6 times in
DMSO-d6 before recording the 1H NMR spectrum (Figure 14).
Comparing the spectra of the polymer 1a2b in DMSO-d6/D2O
5/1 before and after exchange with 1 equiv of 1b allowed one
to observe and quantify by integration the release of the initial
dihydrazide 1a from the polymeric structure. The appearance
of two singlets corresponding to the signals of aromatic protons
of the free dihydrazide 1a (Figure 14, signals 7 and 8) and the
emergence of a new imine signal (Figure 14, signal 6) confirm
the incorporation of 1b in the polymer. The half-time for
exchange was 90 min and 25 h at 80 °C and room temperature,
respectively, at pD ) 4 with an initial monomer concentration
of 5 mM. At pD ) 7, no trace of exchange was detected even
after 3 weeks at room temperature.
This incorporation of 1b into polymer 1a2b results in a
modification of the polymer constitution.
Fluorescence Study of Chemical Exchange Reaction on
1a2b. It is also possible to follow the exchange reaction between
(81) Duverger, E.; Frison, N.; Roche, A.-C.; Monsigny, M. Biochimie 2003,
85, 167–179.
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2007, 13, 3–28.
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Glycodynamers: Polymers Bearing Oligosaccharides Residues
A R T I C L E S
Figure 15. Left and center: Evolution of the fluorescence of 1a2b after addition of 1b under excitation at 393 and 419 nm. Right: Photography of samples
of polymer 1a2b before (left fluorescence cell) and after chemical exchange with 1b (right fluorescence cell).
Figure 17. SPR sensograms resulting from interactions between PNA
immobilized on a carboxylated surface (3000 RU) and (A) a solution of 1b
at 400 µM; (B) a solution of 2a at 400 µM; (C) a solution of 2b at 400
µM; and (D) a solution of 1a at 400 µM. All samples were prepared in a
phosphate buffer (50 mM) at pH ) 6 containing NaCl (154 mM).
Figure 16. Part of the 1H NMR spectra of a mixture obtained by diluting
100 µL of a solution of polymer 1a3 with 500 µL of DMSO-d6, (A) before
and (B) after addition of 1 equiv of 1b. Signals 1-3 correspond to the
polymer 1a3, and signal 6 corresponds to the two equivalent aromatic
protons of released 1a. Signals 4 and 5 are due to the terminal monoimine
of 1a.
Thus, the maximum SPR response for 1a2a was 10 RU
(refractive unit), a value that has to be compared to the 517
RU measured for 1b2a under the same experimental conditions.
These results suggest that there is no significant affinity
improvement of 1a2a and 1a2b for PNA with respect to the
starting monomers. This behavior can be explained by the steric
hindrance caused by the long maltohexaose side chains, which
could prevent the lactosyl moieties present on monomers 2a
and 2b from interacting with the PNA. In a way, lactosyl
moieties are hidden by the long brushes that decorate the
polymer.
It was of particular interest to compare the SPR response of
the monomers and of the corresponding polymers, to see
whether the known glycocluster effect23 and an increase in
affinity would be observed.
The binding constants between PNA and monomers 1a, 1b,
2a, and 2b have been determined after SPR data fitting using
the standard BIA evaluation software.
Interestingly, the SPR response of polymers 1b2a and 1b2b
is, respectively, 3.8 and 7.8 times higher than that induced by
the starting monomers injected at the same concentration before
polymerization takes place (Figure 18). Indeed, polymerization
is slow in the experimental conditions used for SPR (pH ) 6).
Therefore, polymers 1a2a and 1b2b are markedly more effective
ligands for PNA than are the corresponding monomers. A
decrease of the dissociation rate, which is a common feature
for multivalent glycopolymers, was also observed, but was
difficult to quantify due to the multivalent nature of the
interactions studied and to the dynamic character of our polymer
that might dissociate to some extent upon dilution during the
experiment. A complete study of the affinity of these polymers
for lectins and of the effect of lectin binding on the molecular
weight of these polymers would be of interest.
As expected from the PNA specificity, only monomers 1b,
2a, and 2b induced significant response by SPR, giving
equilibrium association constants KA between 2 and 4 × 103
for 2b, KA ) 3.8 × 103 M-1). Interestingly, the bivalent
monomer 1b has an association constant for PNA, respectively,
7.7 and 5.2 times higher than the monovalent monomers 2a
and 2b. This could be explained by the cluster glycoside effect,
which is commonly observed for polyvalent carbohydrates
ligands when compared to their monovalent counterparts for
the same receptor.23,84
M-1 (for 1b, KA ) 2 × 104 M-1; for 2a, KA ) 2.6 × 103 M-1
;
Monomer 1a did not induce any significant response by SPR,
and therefore polymer 1a3 showed no affinity for PNA (Figures
17 and 18).
Among the polymers, only polymers 1b2a and 1b2b induced
a strong response by SPR, whereas polymers 1a2a, 1a2b, despite
their high molecular weight, did not show a response higher
than their corresponding monomers (Figure 18).
Conclusions
Dynamic analogues of glycopolymers have been generated
using reversible acylhydrazone formation. Their dynamic char-
acter was demonstrated by covalent exchange reaction of a
monomeric component by another, resulting in modification of
the glycodynamer fluorescence properties. The molecular weight
(83) Jimbo, A.; Matsumoto, I. J. Biochem. 1982, 91, 945–951.
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J. AM. CHEM. SOC. VOL. 132, NO. 8, 2010 2583

A R T I C L E S
Ruff et al.
Figure 18. SPR sensograms resulting from interactions between PNA immobilized on a carboxylated surface (3000 RU) and (A) polymer 1b2b solution
prepared by diluting a solution with an initial monomer concentration of 5 mM to 400 µM; (B) polymer 1b2a solution prepared by diluting a solution with
an initial monomer concentration of 5 mM to 400 µM; (C) a mixture of monomers 1b and 2a both at 400 µM; (D) a mixture of monomers 1b and 2b both
at 400 µM; (E) polymer 1a2a solution prepared by diluting a solution with an initial monomer concentration of 5 mM to 400 µM; and (F) a mixture of
monomers 1a and 2b both at 400 µM. All samples were prepared just before the analysis in a phosphate buffer (50 mM) at pH ) 6 containing NaCl (154 mM).
as well as the rate of exchange were tuned by modification of
the dialdehyde monomers. Dihydrazide monomers in combina-
tion with aromatic dialdehydes yield high molecular weight
glycopolymers showing reversibility under rather drastic condi-
tions, but stability under physiological conditions. This type of
dynamer may be of interest for applications where slow
decomposition is preferable, such as slow release of a drug.
The use of the aliphatic dialdehyde 3 confers reversibility under
milder conditions, yielding dynamers with a lower molecular
weight, more susceptible to be of use for adaptive purposes,
like multivalent templating with cell or bacteria receptors.
Furthermore, the present fluorescent dynamic glycopolymers
could have applications, in biotechnology for biosensing,85
lectin,86,87 bacteria,87-89 toxin,48 virus88 binding, or labeling,
in analytical chemistry for (adaptive) selective probes, for
instance for heavy metal detection,90 and in materials science
for the development of species, such as polymeric films,
presenting responsive optical properties.91
are more efficient ligands than the corresponding monomers.
These experiments also revealed the detrimental effect of 1a
on binding to PNA, as 1a2a and 1a2b are only weak ligands.
Therefore, not only the physicochemical properties, such as the
fluorescence, but also the affinity for a biological target are, in
principle, tunable by dynamic covalent exchange and modifica-
tion of the polymer constitution through component exchange.
Finally, the results obtained extend the application of
constitutional dynamic chemistry from materials science to
biopolymers and illustrate some aspects of the potential of such
biodynamers.
Acknowledgment. We wish to dedicate this work to the
memory of Henri Benoˆıt (deceased March 23rd, 2009). We thank
the Ministe`re de la Jeunesse, de l’Education nationale et de la
Recherche and the Colle`ge de France for predoctoral fellowships
to Y.R., as well as the Colle`ge de France, the CNRS (UMR 7006)
and the Universite´ de Strasbourg for financial support.
The preliminary investigations of the affinity of the present
glycodynamers for PNA suggest that polymers 1b2b and 1b2a
Supporting Information Available: Experimental details for
the synthesis and characterization of all new compounds and
intermediates. Experimental details for the preparation of
(85) Jelinek, R.; Kolusheva, S. Chem. ReV. 2004, 104, 5987–6016.
(86) Kim, I.-B.; Wilson, J. N.; Bunz, U. H. F. Chem. Commun. 2005, 1273–
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dynamic glycopolymers. Assignment of H NMR signals of
polymer 1a2b and exchange reaction mixture 1a2b+1b in
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Effect of the dilution with DMSO on the main-chain mobility
1
by H NMR. GPC traces for polymers 1a2a, 1a2b, 1b2a, and
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1b2b. Excitation and emission spectra for all polymers. This
material is available free of charge via the Internet at http://
pubs.acs.org.
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