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Vincent M Rotello

Publications and source records attributed to Vincent M Rotello.

At least 37 records · Page 2Linked to original sources
PubMed2005

Contrasting effects of exterior and interior hydrophobic moieties in the complexation of amino acid functionalized gold clusters with alpha-chymotrypsin.

[chemical structure: see text]. A series of L-amino acid functionalized gold nanoparticles with oligo(ethylene glycol) (OEG) tethers of varying length are prepared. These studies show that the hydrophobic side chains of amino acids facilitate the structural retention of alpha-chymotrypsin (ChT) but the interior alkyl chains promote its denaturation. An 80-fold range of denaturation rate constants were obtained for ChT in the presence of various nanoparticles. Thus, the tunable denaturation of protein could be achieved by rational combination of amino acid side chains and OEG tethers.

Amino Acids↗
PubMed2005

Molecular recognition in structured matrixes: control of guest localization in block copolymer films.

We demonstrate the use of molecular recognition to control the spatial distribution of guest molecules within block copolymer films. Block copolymers bearing recognition units were combined with complementary and noncomplementary molecules, and the extent of segregation of these molecules into the different domain types within microphase-separated thin films was quantitatively analyzed using dynamic secondary ion mass spectrometry (SIMS). Complementarity between the guest molecules and the polymer functionalities proved to be a key factor and an efficient tool for directing the segregation preference of the molecules to the different domain types. The effect of segregation preference on the glass transition temperature was studied using differential scanning calorimetry (DSC), and the results corroborate the SIMS findings. In a complementary study, guests with tunable sizes (via dendron substituents) were used to control block copolymer morphology. Morphological characterization using transmission electron microscopy (TEM) and X-ray diffraction reveal that selectivity differences can be directly translated into the ability to obtain different morphologies from recognition unit-functionalized block copolymer scaffolds.

Journal Article↗
PubMed2005

Recognition-induced polymersomes: structure and mechanism of formation.

Random polystyrene copolymers grafted with complementary recognition elements were combined in chloroform producing vesicular aggregates, that is, recognition-induced polymersomes (RIPs). Reflection interference contrast microscopy (RICM) in solution, coupled with optical microscopy (OM) and atomic force microscopy (AFM) on solid substrates, were used to determine the wall thickness of the RIPs. Rather than a conventional mono- or bilayer structure (approximately 10 or approximately 20 nm, respectively) the RIP membrane was 43+/-7 nm thick. Structural arrangement of the polymer chains on the RIP wall were characterized by using angle-resolved X-ray photoelectron spectroscopy (AR-XPS). The interior portion of the vesicle membrane was found to be more polar, containing more recognition units, than the exterior part. This gradient suggests that a rapid self-sorting of polymers takes place during the formation of RIPs, providing the likely mechanism for vesicle self-assembly.

Journal Article↗
PubMed2005

Monolayer-protected nanoparticle-protein interactions.

Monolayer-protected nanoparticles provide an appealing artificial receptor scaffold for targeting proteins and related biomacromolecules. During the past two years, multiple efforts have focused on the engineering and application of nanoparticle-protein interactions. These investigations include the molecular recognition of proteins with nanoparticles in aqueous media, self-assembly of proteins and nanoparticles either in solution or on surface, and construction of nanoparticle-based protein sensors.

Models, Biological↗
PubMed2005

Tunable inhibition and denaturation of alpha-chymotrypsin with amino acid-functionalized gold nanoparticles.

Water-soluble gold nanoparticles bearing diverse l-amino acid terminals have been fabricated to probe the effect of receptor surface on protein surface binding. The interaction of these nanoparticles with alpha-chymotrypsin (ChT) was investigated by activity assay, gel electrophoresis, zeta-potential, circular dichroism, and fluorescence spectroscopy. The results show that both electrostatic and hydrophobic interactions between the hydrophobic patches of receptors and the protein contribute to the stability of the complex. The microscopic binding constants for these receptor-protein systems are 10(6)-10(7) M(-1), with the capacity of the nanoparticle receptors to bind proteins determined by both their surface area and their surface charge density. Furthermore, it is found that the hydrophilic side chains destabilize the ChT structure through either competitive hydrogen bonding or breakage of salt bridges, whereas denaturation was much slower with hydrophobic amino acid side chains. Significantly, correlation between the hydrophobicity index of amino acid side chains and the binding affinity and denaturation rates was observed.

Amino Acids↗
PubMed2005

Noncovalent modification of chymotrypsin surface using an amphiphilic polymer scaffold: implications in modulating protein function.

We report here on a new amphiphilic homopolymer that binds noncovalently to proteins. This polymer not only binds to the target protein chymotrypsin with submicromolar affinity but also stabilizes the native structure of the protein. Since the polymer-protein binding process is based on electrostatic interaction, the bound protein can be released from the polymer surface and reactivated either by increasing the ionic strength or by adding complementary cationic surfactants. The electrostatic binding of polymer to the protein results in a marked change in the substrate specificity of chymotrypsin.

Animals↗
PubMed2005

Direct control of the magnetic interaction between iron oxide nanoparticles through dendrimer-mediated self-assembly.

Cationic superparamagnetic iron oxide nanoparticles were assembled using a series of anionic polyamidoamine dendrimers. The resulting assemblies featured systematically increasing average interparticle spacing over a 2.4 nm range with increasing dendrimer generation. This increase in spacing modulated the collective magnetic behavior by effective lowering of the dipolar coupling between particles. The results obtained in these studies deviate from the predicted dependence of collective behavior on interparticle spacing, suggesting that a dense assembly of magnetically "free" particles can exist with a surprisingly small space between particles.

Journal Article↗
PubMed2005

Model systems for flavoenzyme activity: site-isolated redox behavior in flavin-functionalized random polystyrene copolymers.

[reaction: see text] A model system has been developed to study the redox behaviors of flavin derivatives appended onto random polystyrene copolymers through "click" chemistry strategies. The results demonstrate that flavin units attached onto polymers exhibit site-isolated redox behaviors, yielding new materials with electrochemically tunable associations (K(a)(ox) = 450 M(-)(1), K(a)(red) = 18,200 M(-)(1)) to complementary diamidopyridine (DAP) functionality.

Electrochemistry↗
PubMed2005

Duplex strand formation using alternating copolymers.

The regular arrangement of complementary diaminopyridine-thymine (DAP-THY) on alternating copolymers permits cooperative binding events and the effective formation of well-controlled micrometre-scale aggregates.

Aminopyridines↗
PubMed2005

Reversible regulation of chymotrypsin activity using negatively charged gold nanoparticles featuring malonic acid termini.

Negatively charged gold nanoparticles featuring 2-(10-mercapto-decyl)-malonic acid were synthesized using the Murray place-displacement reaction. These water-soluble malonate gold mixed monolayer protected clusters (MMPCs) effectively bind and inhibit chymotrypsin based on complementary electrostatic surface recognition. The effect of increasing ionic strength on inhibition was also studied. It was observed that addition of high ionic strength solutions to protein-nanoparticle complexes show almost complete restoration of protein activity. The conformational change of chymotrypsin upon binding to the MMPC was investigated using fluorescence spectrometry and circular dichroism, thus correlating structural changes with enzyme activity.

Animals↗
PubMed2004

Molecular recognition in a uradinyl-functionalized stable radical.

Stable radical 2-(6-uradinyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl (1) binds to hydrogen-bonding complement 2,6-di(propylamido)pyridine (DAP) in chloroform with Ka=220 M(-1) at 33 degrees C; ESI-MS shows not only 1:DAP complementary dyad formation, but also 1:(DAP)2 formation at higher concentrations of DAP.

Journal Article↗
PubMed2004

Surfactant layering on mixed monolayer-protected gold clusters.

Positively-charged monolayer protected gold clusters (MMPCs) were mixed with sodium dodecyl sulfate (SDS). At lower SDS concentration, the initially water-soluble particles became organic-soluble while remaining discrete. Upon further addition of SDS, the particles aggregate and become water-soluble. NaCN decomposition, TEM, and DLS characterization reveal the morphology and properties of these encapsulated assemblies.

Gold Colloid↗
PubMed2004

Surface recognition of biomacromolecules using nanoparticle receptors.

Nanoparticles present a versatile scaffold to target biomacromolecule surfaces via complementary interactions. This review highlights some unique features of nanoparticles that make them particularly attractive resources for biomacromolecular recognition, and displays their use in modulation of structure and function of biomacromolecules.

DNA↗
PubMed2004

Recognition-induced transformation of microspheres into vesicles: morphology and size control.

Polystyrene functionalized with diamidopyridine (DAP) recognition units self-assembles in nonpolar media to form thermally reversible micrometer-scale spherical aggregates. The size and the thermal stability of these microspheres can be controlled by the molecular weight of the polymer. The addition of thymine-functionalized polymer to these self-assembled microspheres converted them into vesicular aggregates with a controlled size. The morphology change was reversible: the addition of DAP-functionalized polymer converted the vesicles back to microspheres.

Biosensing Techniques↗