Tuning substrate selectivity of a cationic enzyme using cationic polymers

Noncovalent interactions between an artificial molecular scaffold and a protein are interesting due to the possibility of reversible modulation of the activity of the protein. alpha-Chymotrypsin is a positively charged protein that has been shown to interact with negatively charged polymers. Here we show that positively charged polymers are also capable of electrostatically binding to this protein. The resulting experiments show that the ability of a polymer to bind a protein does not depend only on the pI of the protein. We also realized that the variations in charge density in the polymer backbone afford different selectivities of the enzyme toward charged substrates.     

Self-assembly of facially amphiphilic dendrimers on surfaces

Facially amphiphilic dendrimers have been shown to provide significant difference in surface behavior due to subtle changes in structure. The monodendrons are capable of providing hydrophobic surfaces, while the didendrons provide superhydrophobic surfaces. This provides an example of how a molecular level change could result in significant changes in surface behavior. This difference is attributed to the conformational differences exhibited by these dendrimers on surfaces.     

Supramolecular displacement-mediated activation of a silent fluorescence probe for label-free ligand screening

We report a new approach for the rapid screening of analyte binding affinities for a target protein. We demonstrate that a molecular probe, with a pro-fluorophore substrate and ligand moieties, can be hindered from enzymatic access when bound to the target protein. When analytes displace the probe from the protein's binding pocket, a fluorescence profile is generated. This profile is used to discriminate analytes based on their relative binding affinities.     

Controlled polymerization of N‐isopropylacrylamide with an activated methacrylic ester

A copolymer of N‐isopropylacrylamide with the N‐hydroxysuccinimide ester of methacrylic acid has found use in a variety of applications. Here we report our efforts to gain control over the molecular weight distribution of this copolymer with controlled radical polymerization methods, such as atom transfer radical polymerization, reversible addition–fragmentation transfer (RAFT), and nitroxide‐mediated polymerization. We have found that RAFT is capable of affording these copolymers with a polydispersity index of 1.1–1.2. Our results for all three polymerizations are reported. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6340–6345, 2004     

Effect of guest molecule flexibility in access to dendritic interiors

[structure: see text] Dendrimers are attractive scaffolds for catalysis, since catalytic sites can be isolated and the catalysts are recoverable and reusable. Herein, we show that conformationally constrained molecules have better access to dendritic cores compared to the more flexible counterparts. The results reported here should have implications in utilizing dendrimers as scaffolds for artificial selectivity in catalysis.     

Dendrimers based on a three-dimensionally disposed AB4 monomer

[reaction: see text] Design and synthesis of a novel class of dendrons based on an AB(4) monomer are described. These dendrons have been evaluated by using dendritic encapsulation of a redox active core. The electrochemical properties of symmetric ferrocene-cored dendrimers show that significant alterations in redox potential and heterogeneous electron-transfer rate constants could be achieved even at lower generations.     

Toward globular macromolecules with functionalized interiors: design and synthesis of dendrons with an interesting twist

[see reaction]. Design and synthesis of a novel class of monodendrons, in which the functional units can potentially be directed toward the concave interiors of dendrimers, are described. The key feature of the design is the placement of the amphiphilic and the AB2 functional groups in orthogonal planes.     

Selective sensing of metalloproteins from nonselective binding using a fluorogenic amphiphilic polymer

Nonconjugated fluorogenic amphiphilic polymers containing an anthracene chromophore exhibit fluorescence quenching in the presence of metalloproteins, although the binding of the polymer to proteins is not selective. The reason for this difference is that the possible conformational changes that protein binding could bring about on a polymer do not affect the fluorescence properties of a pendent chromophore in nonconjugated polymers. This is in contrast to the nonspecific binding and response found with conjugated polymers to proteins.