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Biomedical subjects

Vincent M Rotello

Publications and source records attributed to Vincent M Rotello.

At least 19 recordsLinked to original sources
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↗
PubMed2004

Nanoparticles: scaffolds for molecular recognition.

Monolayer and mixed-monolayer protected clusters (MPCs and MMPCs) have great potential to combine molecular functionality with the intrinsic properties of nanometer-sized scaffolds. This synergy can be used to create complex functional devices, including redox-active, electronic, or magnetic storage devices, solution-based sensors, and highly efficient catalysts. This review outlines some of the recent developments in nanoscale receptors based on synthetic and nonbiological recognition elements. In these nanoparticle systems, molecular recognition is achieved by covalent attachment of receptors on the nanoparticles coupled with noncovalent interactions to target substrates. Synthetic host-guest systems, hydrogen bonding, change in redox states, pi-pi stacking, rotaxane formation, and ion recognition are the main topics covered in this review.

Journal Article↗
PubMed2004

Tunable reactivation of nanoparticle-inhibited beta-galactosidase by glutathione at intracellular concentrations.

Positively charged trimethylammonium-functionalized mixed monolayer protected clusters (MMPCs) of different chain lengths (C(8) and C(11)) have been used to bind beta-galactosidase through complementary electrostatic interactions, resulting in complete enzyme inhibition. This inhibition can be reversed in vitro by intracellular concentrations of glutathione (GSH), the main thiol component of the cell. The restoration of activity depends on the chain length of the monolayer. The activity of enzyme bound to particles with C(8) monolayer was completely restored by intracellular concentrations (1-10 mM) of GSH; however, little or no release was observed at extracellular GSH concentrations. In contrast, no restoration was observed for enzyme bound to the C(11) particles at any of the concentrations studied. Taken together, these studies demonstrate that the GSH-mediated release of enzymes bound to MMPCs can be tuned through the structure of the monolayer, a significant tool for protein and drug delivery applications.

Electrophoresis, Agar Gel↗
PubMed2004

Monolayer-controlled substrate selectivity using noncovalent enzyme-nanoparticle conjugates.

Electrostatic interactions were used to noncovalently conjugate chymotrypsin to gold nanoparticles featuring hybrid tetraethylene(glycol)alkanethiol monolayers terminated with carboxylate groups. This conjugation process greatly alters the substrate selectivity of the adsorbed chymotrypsin, inhibiting the hydrolysis of anionic subtrates without affecting the hydrolysis rate of cationic analogues.

Acetates↗
PubMed2004

Recognition and stabilization of peptide alpha-helices using templatable nanoparticle receptors.

alpha-Helices are important structural elements in proteins. To provide a scaffold for the facial recognition of peptides, we have explored the interaction of cationic mixed monolayer protected clusters (MMPCs) with a tetra-aspartate peptide in water. In these studies, substantial enhancement of peptide helicity was observed upon addition of the MMPC. Significantly, this stabilization increased with time, demonstrating templation of the monolayer to the peptide helix.

Gold↗
PubMed2004

Model systems for flavoenzyme activity: interplay of hydrogen bonding and aromatic stacking in cofactor redox modulation.

[structure: see text] A model system has been developed to study the synergy between aromatic stacking and hydrogen bonding in the binding of a flavin derivative. The results show that the identity of both the hydrogen bonding and pi-stacking units strongly determine the overall receptor affinity for flavin in both the oxidized and radical anion forms.

Flavin Mononucleotide↗
PubMed2004

Control of protein structure and function through surface recognition by tailored nanoparticle scaffolds.

Thioalkyl and thioalkylated oligo(ethylene glycol) (OEG) ligands with chain-end functionality were used to fabricate water-soluble CdSe nanoparticle scaffolds. Surface recognition of chymotrypsin (ChT) was achieved using these functionalized nanoparticle scaffolds, with three levels of interaction demonstrated: no interaction (OEG terminated with hydroxyl group), inhibition with denaturation (carboxylate-terminated thioalkyl ligands), and inhibition with retention of structure (carboxylate-terminated OEG). The latter process was reversible upon an increase in ionic strength, with essentially complete restoration of enzymatic activity.

Cadmium Compounds↗
PubMed2003

Model systems for flavoenzyme activity: relationships between cofactor structure, binding and redox properties.

A series of flavins were synthesized bearing electron-withdrawing and -donating substituents. The electrochemical properties of these flavins in a nonpolar solvent were determined. The recognition of these flavins by a diamidopyridine (DAP) receptor and the effect this receptor has on flavin redox potential was also quantified. It was found that the DAP-flavin binding affinity and the reduction potentials (E(1/2)) for both the DAP-bound and unbound flavins correlated well with functions derived from linear free energy relationships (LFERs). These results provide insight and predictive capability for the interplay of electronics and redox state-specific interactions for both abiotic and enzymatic systems.

Electrochemistry↗
PubMed2003

Reversible "irreversible" inhibition of chymotrypsin using nanoparticle receptors.

Anionically functionalized amphiphilic nanoparticles efficiently inhibit chymotrypsin through electrostatic binding followed by protein denaturation. We demonstrate the ability to disrupt this "irreversible" inhibition of chymotrypsin through modification of the nanoparticle surface using cationic surfactants. Up to 50% of original chymotrypsin activity is rescued upon long-chain surfactant addition. Dynamic light-scattering studies demonstrate that chymotrypsin is released from the nanoparticle surface. The conformation of the rescued chymotrypsin was characterized by fluorescence and fluorescence anisotropy, indicating that chymotrypsin regains a high degree of native structure upon surfactant addition.

Carboxylic Acids↗
PubMed2003

Redox modulation of benzene triimides and diimides via noncovalent interactions.

[reaction: see text] Mellitic triimides undergo three sequential one-electron reduction processes whose potentials are significantly lowered in the presence of alkyl thioureas. The two sequential reductions of benzene diimides are similarly stabilized. Calculation of the relative free energy change between the different electronic states of the imide acceptors and their corresponding alkyl thiourea complexes indicates dramatic increases in hydrogen bond strength with increasing acceptor charge density.

Journal Article↗
PubMed2003

Hydrogen bonding in redox-modulated molecular recognition. An experimental and theoretical investigation.

Two receptors, a diaminotriazine derivative (DAT) and diamidopyridine (DAP), are complementary to the electroactive naphthalimide (N) through three-point hydrogen bonding. The association constants of the two receptors were evaluated for both the fully oxidized and the radical anion forms of N. In the oxidized state, the two receptors displayed identical binding constants. Diamidopyridine, however, lowers the reduction potential of naphthalimide to a far greater extent than does diaminotriazine, indicating a greater affinity for diamidopyridine by naphthalimide in the radical anion form. This behavior was mirrored by EPR experiments that showed small deviations from the hyperfine coupling pattern of N(red) in the presence of DAT, with greater effects seen for the N(red).DAP complex. Computational simulations using the UB3LYP/6-311+G(d,p)//UHF/6-31G(d) hybrid gave theoretical hyperfine constants in good quantitative agreement with the experimental results. Using this correlation, we determined that electrostatics and hydrogen bond polarizability play key roles in controlling redox-modulated molecular recognition.

Hydrogen Bonding↗