Metadata population dynamics in artificial metapopulations

The file contains raw data used in the accompanied manuscript. One sheet contains all demographic data (population size, per stage) during the course of the experiment. A second sheet contains dispersal data (counts on quadrants

Detection of Heavy Metal Ions in Water by High-Resolution Surface Plasmon Resonance Spectroscopy Combined with Anodic Stripping Voltammetry

High-resolution differential surface plasmon resonance (SPR) with anodic stripping voltammetry (ASV) capability has been demonstrated for detecting heavy metal ions in water. Metal ions are electroplated onto the gold SPR sensing surface and are quantitatively detected by stripping voltammetry. Both the SPR angular shift and electrochemical current signal are recorded to identify the type and amount of the metal ions in water. The performance of the combined approach is further enhanced by a differential detection approach. The gold sensor surface is divided into a reference and a sensing area, and the difference in the SPR angles from the two areas is detected with a quadrant cell photodetector as a differential signal. Our system demonstrated quantitative detection of copper, lead, and mercury ions in water from part-per-million to sub-part-per-billion levels with good linearity

Plasmonic-Based Imaging of Local Square Wave Voltammetry

Square wave voltammetry (SWV) is widely used in electrochemical analysis and sensors because of its high sensitivity and efficient rejection of background current, but SWV by the conventional electrochemical detection method does not provide spatial resolution. We report here a plasmonic method to image local SWV, which opens the door for analyzing heterogeneous electrochemical reactions and for high-throughput detections of microarrays. We describe the basic principle, validate the principle by comparing the plasmonic-based SWV with those obtained with the conventional method, and demonstrate imaging capability for local electrochemical analysis

Plasmonic-Based Imaging of Local Square Wave Voltammetry

Square wave voltammetry (SWV) is widely used in electrochemical analysis and sensors because of its high sensitivity and efficient rejection of background current, but SWV by the conventional electrochemical detection method does not provide spatial resolution. We report here a plasmonic method to image local SWV, which opens the door for analyzing heterogeneous electrochemical reactions and for high-throughput detections of microarrays. We describe the basic principle, validate the principle by comparing the plasmonic-based SWV with those obtained with the conventional method, and demonstrate imaging capability for local electrochemical analysis

Label-Free Multimetric Measurement of Molecular Binding Kinetics by Electrical Modulation of a Flexible Nanobiolayer

Most label-free techniques rely on measuring refractive index or mass change on the sensor surface. Thus, it is challenging for them to measure small molecules or enzymatic processes that only induce a minor mass change on the analyte molecules. Here, we have developed a technique by combining Surface Plasmon Resonance sensing with an Oscillating Biomolecule Layer approach (SPR-OBL) to enhance the sensitivity of traditional SPR. In addition to the inherent mass sensitivity, SPR-OBL is also sensitive to the charge and conformational change of the analyte; hence it overcomes the mass limit and is able to detect small molecules. We show that the multimetric SPR-OBL measurement allows for sensing any changes regarding mass, charge, and conformation, which expands the detection capability of SPR

Label-Free Multimetric Measurement of Molecular Binding Kinetics by Electrical Modulation of a Flexible Nanobiolayer

Most label-free techniques rely on measuring refractive index or mass change on the sensor surface. Thus, it is challenging for them to measure small molecules or enzymatic processes that only induce a minor mass change on the analyte molecules. Here, we have developed a technique by combining Surface Plasmon Resonance sensing with an Oscillating Biomolecule Layer approach (SPR-OBL) to enhance the sensitivity of traditional SPR. In addition to the inherent mass sensitivity, SPR-OBL is also sensitive to the charge and conformational change of the analyte; hence it overcomes the mass limit and is able to detect small molecules. We show that the multimetric SPR-OBL measurement allows for sensing any changes regarding mass, charge, and conformation, which expands the detection capability of SPR

Quantifying Ligand–Protein Binding Kinetics with Self-Assembled Nano-oscillators

Measuring ligand–protein interactions is critical for unveiling molecular-scale biological processes in living systems and for screening drugs. Various detection technologies have been developed, but quantifying the binding kinetics of small molecules to the proteins remains challenging because the sensitivities of the mainstream technologies decrease with the size of the ligand. Here, we report a method to measure and quantify the binding kinetics of both large and small molecules with self-assembled nano-oscillators, each consisting of a nanoparticle tethered to a surface via long polymer molecules. By applying an oscillating electric field normal to the surface, the nanoparticle oscillates, and the oscillation amplitude is proportional to the number of charges on the nano-oscillator. Upon the binding of ligands onto the nano-oscillator, the oscillation amplitude will change. Using a plasmonic imaging approach, the oscillation amplitude is measured with subnanometer precision, allowing us to accurately quantify the binding kinetics of ligands, including small molecules, to their protein receptors. This work demonstrates the capability of nano-oscillators as an useful tool for measuring the binding kinetics of both large and small molecules

'Bibliotheca' drafts

We report the imaging of the cell–substrate adhesion of a single cell with subcellular spatial resolution. Osmotic pressure was introduced to provide a controllable mechanical stimulation to the cell attached to a substrate, and high-resolution surface plasmon resonance microscopy was used to map the response of the cell, from which local cell–substrate adhesion was determined. In addition to high spatial resolution, the approach is noninvasive and fast and allows for the continuous mapping of cell–substrate interactions and single-cell movements

Plasmonic Imaging of Surface Electrochemical Reactions of Single Gold Nanowires

Nanomaterials have been widely used in energy and sensing applications because of their unique chemical and physical properties, especially their surface reactions. Measuring the local reactions of individual nanomaterials, however, has been an experimental challenge. Here we report on plasmonic imaging of surface electrochemical reactions of individual gold nanowires (AuNWs). We coated a gold thin film (plasmonic sensing layer) with a dielectric layer (Cytop) with refractive index close to that of water, and then a graphene layer for electrical contact. This design removed the interference from the sensing layer while preserving sharp surface plasmon resonance, which allowed us to obtain cyclic voltammograms of surface electrochemistry of individual AuNWs for the first time. We also investigated the difference in the electrochemical reactions of AuNWs and Au surfaces, and local distribution of electrochemical activities within a single AuNW