1,721,060 research outputs found
The 46th EUCHEM conference on stereochemistry (Budie;rgenstock Conference 2011), brunnen, May 1-6, 2011
No full textCombinatorial chemistry: covalent versus dynamic approach
No full textA review on the concept of dynamic combinatorial chem. (DCC) and illustration in which areas of DCC has been applied and to which extend success has been achieved. In. Topics covered include chem. bond formation under thermodn. control, applications of DCC, DCC for detecting weak interactions, and systems chem
Catalytic self-assembled monolayers on gold nanoparticles
No full textThis review describes the attractiveness of catalytic self-assembled monolayers (SAMs) on gold
nanoparticles as catalytic systems. The hybrid inorganic–organic catalytic systems combine the
advantages of homogeneous and heterogeneous catalysis (higher activity and catalyst recycling,
respectively). The high fidelity process of SAM formation on gold nanoparticles, together with the
possibility of making mixed SAMs composed of different thiols, provides an unprecedented route
to stable, complex catalytic systems. Insertion of catalysts in a mixed monolayer can improve the
catalytic performances, due to catalyst orientation, changes in the local chemical environment, or
through the steering effect of neighbouring thiols. Alternatively, insertion of catalytic units in a
monolayer may be an essential prerequisite in the case when catalysis requires cooperation
between two catalytic units (for instance two metal ions). Finally, the multivalent nature of these
systems is an important feature especially in the case when the substrate contains multiple reactive
sites. Catalytic SAMs on gold nanoparticles also find applications beyond the field of catalysis,
for instance in diagnostics and nanotechnology
Dynamic Covalent Capture: A sensitive tool for detecting molecular interactions
No full textMolecular recognition is at the centre of many areas of chemistry. Examples are analytical chemistry (analyte-sensor), catalysis (transition state-catalyst), medicinal chemistry (drug-biotarget) and advanced materials chemistry (building block A-building block B). Methodology that allows the rapid and precise detection of molecular recognition events is essential in all these fields. Traditionally, molecular recognition has been studied based on a rational design approach involving many iterative optimisation loops, which makes it an energy- and time consuming process. Additionally, it requires detailed knowledge about the target and the recognition process itself, information which is not always available. Currently, combinatorial methods are increasingly being used for detecting molecular recognition events, allowing the simultaneous screening of a vast amount of chemical compounds enabling a much larger part of chemical space to be explored. Dynamic covalent capture extends on the combinatorial approach for detecting molecular recognition events, but at a higher sensitivity level compared to conventional methodologies and with the novelty of self-selection by the target. The essential point of dynamic covalent capture is that a molecular recognition event is followed by the formation of a reversible covalent bond between the two molecule
Controlling supramolecular complex formation on the surface of a monolayer-protected gold nanoparticle in water
Full text linkA combination of hydrophobic and electrostatic interactions
drives the self-assembly of a large number of small molecules on the surface of a monolayer-protected gold nanoparticle. The hydrophobic interactions originate
from the insertion of an aromatic unit in the hydrophobic part of the monolayer.This is evidenced by a shift in the emission wavelength of the fluorogenic probe upon binding. Up to around 35 small molecules can be simultaneously bound to the monolayer surface at micromolar concentrations in water. It is shown that an
understanding of the supramolecular interactions that drive complex formation on the monolayer surface provides unprecedented control over the supramolecular chemistry occurring on the surface. By taking advantage of the
different kinds of noncovalent interactions present in different probes, it is possibile to displace one type of surface-bound molecule from a heteromeric surface selectively. Finally, it is also possible to catch and release one type of surface-bound molecule selectively
Reversible Control over the Valency of a Nanoparticle-Based Supramolecular System
No full textThe reversible "catch-and-release" of small molecules from the surface of monolayer-protected gold nanoparticles is described. The valency of the system (i.e., the number of molecules bound to the surface) can be controlled through the addition and removal of metal ions from the monolayer. Both the change in valency and the release rate of the molecules are strongly pH-dependent. The release rate can be regulated by altering the ratio of metal ions in the monolayer
Dynamic nanoproteins: Self-assembled peptide surfaces on monolayer protected gold nanoparticles
No full textHere, we demonstrate the formation of dynamic peptide surfaces through the self-assembly of small peptides on the surface of monolayer protected gold nanoparticles. The complexity of the peptide surface can be simply tuned by changing the chemical nature of the added peptides and the ratio in which these are added. The dynamic nature of the surface permits adaptation to changes in the environment
Dynamic covalent capture of hydrazides by a phosphonate-target immobilized on resin
Full text linkA protocol is described that permits the self-selection of hydrazides from a small library by a phosphonate-target immobilized on resin. Hydrazides are captured by a neighbouring aldehyde group through reversible hydrazone bond formation. Stabilizing intramolecular interactions between the phosphonate-target and functional groups of the hydrazides drive the selection process. The phosphonate-target is introduced onto commercially available Tentagel resin through straightforward synthetic steps. The functionalized resin could be conveniently characterized by HR-MAS NMR spectroscopy using a recently developed transverse relaxation filter that eliminates the strong phase defects commonly observed with CPMG sequences. In addition, a protocol was developed to quantitatively remove the captured hydrazides from resin in order to analyse their composition by LC/MS. Kinetic experiments were used to study hydrazone formation and exchange on resin yielding similar results to those obtained previously in solution. Competition experiments showed that the system reaches thermodynamic equilibrium if multiple hydrazides are added to the resin. Finally, competition experiments showed that the immobilized phosphonate-target indeed amplifies the capture of those hydrazides able to develop stabilizing interactions with the target. Importantly, the obtained amplification profile was nearly identical to the ones obtained previously in solution studies. Notably, the observed amplification factors for the self-selected hydrazides were higher, which was attributed to steric effects imposed by the resin
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