Synthesis of Au-CdS@CdSe Hybrid Nanoparticles with a Highly Reactive Gold Domain.
We propose a novel route to synthesize semiconductor–gold hybrid nanoparticles directly in water, resulting in much larger gold domains than previous protocols (up to 50 nm) with very reactive surfaces which allow further functionalization. This method advances the possibility of self-assembly into complex structures with catalytic activity toward the reduction of nitro compounds by hydrides. The large size of these gold domains in hybrid particles supports efficient light scattering at the plasmon resonance frequency, making such structures attractive for single-particle studies.
Plasmonic nanosensors reveal a height dependence of MinDE protein oscillations on membrane features
6 p.-4 fig.
CTAB Stabilizes Silver on Gold Nanorods
We present a study that allows us to explain the chemical changes behind the often observed but so far ununderstood drift of the plasmon resonance of chemically prepared gold nanorods in microfluid...
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. NanoSPR could become a powerful tool in drug development, drug delivery, and membrane studies.
Single Out-of-Resonance Dielectric Nanoparticles as Molecular Sensors.
Light scattering from single nanoparticles and nanostructures is a commonly used readout method for nanosensors. Increasing the spectral sensitivity of resonant nanosensors to changes in their local surrounding has been the focus of many studies. Switching from spectral to intensity monitoring allows one to investigate nonresonant or out-of-resonance dielectric nanoparticles. Here, we systematically compared such dielectric silica nanoparticles with plasmonic gold nanorods by deriving analytical expressions and by performing experiments. The experiments show a similar sensitivity for the detection of an adsorbate layer for both particle types, which is in good agreement with theory. The fla…
Plasmonic Nanosensors for the Label-Free Imaging of Dynamic Protein Patterns.
We introduce a new approach to monitor the dynamics and spatial patterns of biological molecular assemblies. Our molecular imaging method relies on plasmonic gold nanoparticles as point-like detectors and requires no labeling of the molecules. We show spatial resolution of up to 5 μm and 30 ms temporal resolution, which is comparable to wide-field fluorescence microscopy, while requiring only readily available gold nanoparticles and a dark-field optical microscope. We demonstrate the method on MinDE proteins attaching to and detaching from lipid membranes of different composition for 24 h. We foresee our new imaging method as an indispensable tool in advanced molecular biology and biophysic…
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.
Potassium Triggers a Reversible Specific Stiffness Transition of Polyethylene Glycol
We use plasmon rulers made from two connected gold nanoparticles to monitor the conformation and stiffness of single PEG molecules and their response to cations. By observing equilibrium fluctuations of the interparticle distance, we obtain the spring constants or stiffness of the connecting single-molecule tether with pico-Newton sensitivity. We observe a transition of the PEG molecules’ extension and stiffness above about 1.2 mM K+ ion concentration which is specific to potassium ions. Molecular dynamics simulations reveal the formation of crown-like structures as the most likely molecular mechanism responsible for this specific effect.
Narrowing the Plasmonic Sensitivity Distribution by Considering the Individual Size of Gold Nanorods
The plasmonic nanoparticle sensitivity, sensing volume, and the signal-to-noise ratio are strongly dependent on the nanoparticle dimensions. It is difficult to chemically produce or purify nanoparticles with a size variation of less than 10%. This size variation induces a systematic error in sensing experiments that can be reduced when the exact size of each individual nanoparticle is known. In this work, we show how the size of gold nanorods can be estimated directly from the optical spectra of single nanoparticles by using the increase of radiation damping with the nanoparticle size. We verify our approach by comparing these spectrally estimated sizes with the precise sizes of exactly the…
Conformational dynamics of a single protein monitored for 24 hours 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. Our measurements confirm the previously known conformational dynamics with transition times in the second to minute time scale and reveals new dynamics on the time scale of minutes to hours. Plasmon rulers thus extend the observation bandwidth 3–4 orders of magnitude with respect to single-molecule fluorescence resonance energy transfer a…