3 research outputs found
<sup>19</sup>F NMR-Guided Design of Glycomimetic Langerin Ligands
C-type lectin receptors
(CLRs) play a pivotal role in pathogen
defense and immune homeostasis. Langerin, a CLR predominantly expressed
on Langerhans cells, represents a potential target receptor for the
development of anti-infectives or immunomodulatory therapies. As mammalian
carbohydrate binding sites typically display high solvent exposure
and hydrophilicity, the recognition of natural monosaccharide ligands
is characterized by low affinities. Consequently, glycomimetic ligand
design poses challenges that extend to the development of suitable
assays. Here, we report the first application of <sup>19</sup>F R<sub>2</sub>-filtered NMR to address these challenges for a CLR, i.e.,
Langerin. The homogeneous, monovalent assay was essential to evaluating
the <i>in silico</i> design of 2-deoxy-2-carboxamido-α-mannoside
analogs and enabled the implementation of a fragment screening against
the carbohydrate binding site. With the identification of both potent
monosaccharide analogs and fragment hits, this study represents an
important advancement toward the design of glycomimetic Langerin ligands
and highlights the importance of assay development for other CLRs
Epitope Recognition of Antibodies against a <i>Yersinia pestis</i> Lipopolysaccharide Trisaccharide Component
Today, the process of selecting carbohydrate
antigens as a basis
for active vaccination and the generation of antibodies for therapeutic
and diagnostic purposes is based on intuition combined with trial
and error experiments. In efforts to establish a rational process
for glycan epitope selection, we employed glycan array screening,
surface plasmon resonance, and saturation transfer difference (STD)-NMR
to elucidate the interactions between antibodies and glycans representing
the <i>Yersinia pestis</i> lipopolysaccharide (LPS). A trisaccharide
epitope of the LPS inner core glycan and different LPS-derived oligosaccharides
from various Gram-negative bacteria were analyzed using this combination
of techniques. The antibody-glycan interaction with a heptose substructure
was determined at atomic-level detail. Antibodies specifically recognize
the <i>Y. pestis</i> trisaccharide and some substructures
with high affinity and specificity. No significant binding to LPS
glycans from other bacteria was observed, which suggests that the
epitopes for just one particular bacterial species can be identified.
On the basis of these results we are beginning to understand the rules
for structure-based design and selection of carbohydrate antigens
Carbohydrate-Lectin Recognition of Sequence-Defined Heteromultivalent Glycooligomers
Multivalency as a key principle in
nature has been successfully
adopted for the design and synthesis of artificial glycoligands by
attaching multiple copies of monosaccharides to a synthetic scaffold.
Besides their potential in various applied areas, e.g. as antiviral
drugs, for the vaccine development and as novel biosensors, such glycomimetics
also allow for a deeper understanding of the fundamental aspects of
multivalent binding of both artificial and natural ligands. However,
most glycomimetics so far neglect the purposeful arranged heterogeneity
of their natural counterparts, thus limiting more detailed insights
into the design and synthesis of novel glycomimetics. Therefore, this
work presents the synthesis of monodisperse glycooligomers carrying
different sugar ligands at well-defined positions along the backbone
using for the first time sequential click chemistry and stepwise assembly
of functional building blocks on solid support. This approach allows
for straightforward access to sequence-defined, multivalent glycooligomers
with full control over number, spacing, position, and type of sugar
ligand. We demonstrate the synthesis of a set of heteromultivalent
oligomers presenting mannose, galactose, and glucose residues. All
heteromultivalent structures show surprisingly high affinities toward
Concanavalin A lectin receptor in comparison to their homomultivalent
analogues presenting the same number of binding ligands. Detailed
studies of the ligand/receptor interaction using STD-NMR and 2fFCS
indeed indicate a change in binding mechanism for trivalent glycooligomers
presenting mannose or combinations of mannose and galactose residues.
We find that galactose residues do not participate in the binding
to the receptor, but they promote steric shielding of the heteromultivalent
glycoligands and thus result in an overall increase in affinity. Furthermore,
the introduction of nonbinding ligands seems to suppress receptor
clustering of multivalent ligands. Overall these results support the
importance of heteromultivalency specifically for the design of novel
glycoligands and help to promote a fundamental understanding of multivalent
binding modes