Directed evolution of artificial repeat proteins as habit modifiers for the morphosynthesis of (111)-terminated gold nanocrystals.

Natural biocomposites are shaped by proteins that have evolved to interact with inorganic materials. Protein directed evolution methods which mimic Darwinian evolution have proven highly successful to generate improved enzymes or therapeutic antibodies but have rarely been used to evolve protein-material interactions. Indeed, most reported studies have focused on short peptides and a wide range of oligopeptides with chemical binding affinity for inorganic materials have been uncovered by phage display methods.

Conformational Dynamics of a Single Protein Monitored for 24 h at Video Rate.

We use plasmon rulers to follow the conformational dynamics of a single protein for up to 24 h at a video rate. The plasmon ruler consists of two gold nanospheres connected by a single protein linker. In our experiment, we follow the dynamics of the molecular chaperone heat shock protein 90 (Hsp90), which is known to show "open" and "closed" conformations.

Plasmonic Nanosensors for the Determination of Drug Effectiveness on Membrane Receptors.

We demonstrate the potential of the NanoSPR (nanoscale surface plasmon resonance sensors) method as a simple and cheap tool for the quantitative study of membrane protein-protein interactions. We use NanoSPR to determine the effectiveness of two potential drug candidates that inhibit the protein complex formation between FtsA and ZipA at initial stages of bacterial division. As the NanoSPR method relies on individual gold nanorods as sensing elements, there is no need for fluorescent labels or organic cosolvents, and it provides intrinsically high statistics.

Plasmonic nanosensors for simultaneous quantification of multiple protein-protein binding affinities.

Most of current techniques used for the quantification of protein-protein interactions require the analysis of one pair of binding partners at a time. Herein we present a label-free, simple, fast, and cost-effective route to characterize binding affinities between multiple macromolecular partners simultaneously, using optical dark-field spectroscopy and individual protein-functionalized gold nanorods as sensing elements. Our NanoSPR method could easily become a simple and standard tool in biological, biochemical, and medical laboratories.

Multiplexed plasmon sensor for rapid label-free analyte detection.

Efficient and cost-effective multiplexed detection schemes for proteins in small liquid samples would bring drastic advances to fields like disease detection or water quality monitoring. We present a novel multiplexed sensor with randomly deposited aptamer functionalized gold nanorods. The spectral position of plasmon resonances of individual nanorods, monitored by dark-field spectroscopy, respond specifically to different proteins.

Single unlabeled protein detection on individual plasmonic nanoparticles.

The ultimate detection limit in analytic chemistry and biology is the single molecule. Commonly, fluorescent dye labels or enzymatic amplification are employed. This requires additional labeling of the analyte, which modifies the species under investigation and therefore influences biological processes.

Cholesterol biosensors based on oxygen sensing alginate-silica microspheres.

Cholesterol determination in body is important in diagnosis of diseases like coronary heart disease, arteriosclerosis, diabetes, and obstructive jaundice. This research aims at developing fluorimetric cholesterol biosensors based on self-assembled mesoporous alginate-silica (Algilica) microspheres. For preparing the biosensor, Pt-(II)-octaethylporphine (PtOEP; oxygen sensitive metalloporphyrin) dye has been loaded in the Algilica microspheres using the solvent-mediated precipitation method.