20 research outputs found
NMR and Molecular Recognition of N‑Glycans: Remote Modifications of the Saccharide Chain Modulate Binding Features
Glycans
play a key role as recognition elements in the communication
of cells and other organisms. Thus, the analysis of carbohydrate–protein
interactions has gained significant importance. In particular, nuclear
magnetic resonance (NMR) techniques are considered powerful tools
to detect relevant features in the interaction between sugars and
their natural receptors. Here, we present the results obtained in
the study on the molecular recognition of different mannose-containing
glycans by <i>Pisum sativum</i> agglutinin. NMR experiments
supported by Corcema-ST analysis, isothermal titration calorimetry
(ITC) experiments, and molecular dynamics (MD) protocols have been
successfully applied to unmask important binding features and especially
to determine how a remote branching substituent significantly alters
the binding mode of the sugar entity. These results highlight the
key influence of common structural modifications in natural glycans
on molecular recognition processes and underscore their importance
for the development of biomedical applications
Polycationic Ligands in Gold Catalysis: Synthesis and Applications of Extremely π‑Acidic Catalysts
Very
often ligands are anionic or neutral species. Cationic ones
are rare, and, when used, the positively charged groups are normally
appended to the periphery of the ligand. Here, we describe a dicationic
phosphine with no spacer between the phosphorus atom and the two positively
charged groups. This structural feature makes its donor ability poorer
than that of phosphites and only comparable to extremely toxic or
pyrophoric compounds such as PF<sub>3</sub> or P(CF<sub>3</sub>)<sub>3</sub>. By exploiting these properties, a new Au catalyst has been
developed displaying a dramatically enhanced capacity to activate
π-systems. This has been used to synthesize very sterically
hindered and naturally occurring 4,5-disubstituted phenanthrenes.
The present approach is expected to be applicable to the development
and improvement of many other transition metal catalyzed transformations
that benefit from extremely strong π-acceptor ligands. The mechanism
of selected catalytic transformations has been explored by density
functional calculations
Polycationic Ligands in Gold Catalysis: Synthesis and Applications of Extremely π‑Acidic Catalysts
Very
often ligands are anionic or neutral species. Cationic ones
are rare, and, when used, the positively charged groups are normally
appended to the periphery of the ligand. Here, we describe a dicationic
phosphine with no spacer between the phosphorus atom and the two positively
charged groups. This structural feature makes its donor ability poorer
than that of phosphites and only comparable to extremely toxic or
pyrophoric compounds such as PF<sub>3</sub> or P(CF<sub>3</sub>)<sub>3</sub>. By exploiting these properties, a new Au catalyst has been
developed displaying a dramatically enhanced capacity to activate
π-systems. This has been used to synthesize very sterically
hindered and naturally occurring 4,5-disubstituted phenanthrenes.
The present approach is expected to be applicable to the development
and improvement of many other transition metal catalyzed transformations
that benefit from extremely strong π-acceptor ligands. The mechanism
of selected catalytic transformations has been explored by density
functional calculations
Polycationic Ligands in Gold Catalysis: Synthesis and Applications of Extremely π‑Acidic Catalysts
Very
often ligands are anionic or neutral species. Cationic ones
are rare, and, when used, the positively charged groups are normally
appended to the periphery of the ligand. Here, we describe a dicationic
phosphine with no spacer between the phosphorus atom and the two positively
charged groups. This structural feature makes its donor ability poorer
than that of phosphites and only comparable to extremely toxic or
pyrophoric compounds such as PF<sub>3</sub> or P(CF<sub>3</sub>)<sub>3</sub>. By exploiting these properties, a new Au catalyst has been
developed displaying a dramatically enhanced capacity to activate
π-systems. This has been used to synthesize very sterically
hindered and naturally occurring 4,5-disubstituted phenanthrenes.
The present approach is expected to be applicable to the development
and improvement of many other transition metal catalyzed transformations
that benefit from extremely strong π-acceptor ligands. The mechanism
of selected catalytic transformations has been explored by density
functional calculations
Polycationic Ligands in Gold Catalysis: Synthesis and Applications of Extremely π‑Acidic Catalysts
Very
often ligands are anionic or neutral species. Cationic ones
are rare, and, when used, the positively charged groups are normally
appended to the periphery of the ligand. Here, we describe a dicationic
phosphine with no spacer between the phosphorus atom and the two positively
charged groups. This structural feature makes its donor ability poorer
than that of phosphites and only comparable to extremely toxic or
pyrophoric compounds such as PF<sub>3</sub> or P(CF<sub>3</sub>)<sub>3</sub>. By exploiting these properties, a new Au catalyst has been
developed displaying a dramatically enhanced capacity to activate
π-systems. This has been used to synthesize very sterically
hindered and naturally occurring 4,5-disubstituted phenanthrenes.
The present approach is expected to be applicable to the development
and improvement of many other transition metal catalyzed transformations
that benefit from extremely strong π-acceptor ligands. The mechanism
of selected catalytic transformations has been explored by density
functional calculations
Polycationic Ligands in Gold Catalysis: Synthesis and Applications of Extremely π‑Acidic Catalysts
Very
often ligands are anionic or neutral species. Cationic ones
are rare, and, when used, the positively charged groups are normally
appended to the periphery of the ligand. Here, we describe a dicationic
phosphine with no spacer between the phosphorus atom and the two positively
charged groups. This structural feature makes its donor ability poorer
than that of phosphites and only comparable to extremely toxic or
pyrophoric compounds such as PF<sub>3</sub> or P(CF<sub>3</sub>)<sub>3</sub>. By exploiting these properties, a new Au catalyst has been
developed displaying a dramatically enhanced capacity to activate
π-systems. This has been used to synthesize very sterically
hindered and naturally occurring 4,5-disubstituted phenanthrenes.
The present approach is expected to be applicable to the development
and improvement of many other transition metal catalyzed transformations
that benefit from extremely strong π-acceptor ligands. The mechanism
of selected catalytic transformations has been explored by density
functional calculations
Polycationic Ligands in Gold Catalysis: Synthesis and Applications of Extremely π‑Acidic Catalysts
Very
often ligands are anionic or neutral species. Cationic ones
are rare, and, when used, the positively charged groups are normally
appended to the periphery of the ligand. Here, we describe a dicationic
phosphine with no spacer between the phosphorus atom and the two positively
charged groups. This structural feature makes its donor ability poorer
than that of phosphites and only comparable to extremely toxic or
pyrophoric compounds such as PF<sub>3</sub> or P(CF<sub>3</sub>)<sub>3</sub>. By exploiting these properties, a new Au catalyst has been
developed displaying a dramatically enhanced capacity to activate
π-systems. This has been used to synthesize very sterically
hindered and naturally occurring 4,5-disubstituted phenanthrenes.
The present approach is expected to be applicable to the development
and improvement of many other transition metal catalyzed transformations
that benefit from extremely strong π-acceptor ligands. The mechanism
of selected catalytic transformations has been explored by density
functional calculations
Kinetic parameters of DNM1L basal GTPase activities.
a<p>In all cases except for the cooperative model with the mutant S35A, k<sub>obs</sub> and K correspond to k<sub>cat</sub> and K<sub>m</sub> of the applied Michaelis-Menten model;</p>b<p>WT = 100; <sup>c</sup> k<sub>obs</sub> and K could not be determined in a reliable manner, since the substrate did not reach the range of saturating levels.</p
Superposition of the two DNM1L GG structures and dynamin-1 GG.
<p>(<b>A</b>) Overlay of the nucleotide-free DNM1L GG structure in white with the GMP-PNP-bound structure in green (shown without ligands). Side chains that were mutated in our study are shown as stick models with sequence number labels. (<b>B</b>) Overlay of dynamin-1 (PDB code 2X2F) in yellow with the structure of GMP-PNP-bound DNM1L in green. Mutated residues of DNM1L that are equivalent to those of dynamin (see Fig. 3A) are displayed as side chain stick models with dynamin sequence numbers (depicted without ligands).</p
Structure-function map of the modelled DNM1L active site dimer.
<p>All active site and dimerization residues that have been mutated to alanine are represented as stick models, as well as the GTP. The turnover numbers of the respective mutants as determined by the GTPase assay for basal activity are shown, whereby the WT was defined as 100%. Molecule A of the dimer is depicted in green, while the second molecule B is shown in orange, with the corresponding D190A*.</p