Channelrhodopsin C1C2: Photocycle kinetics and interactions near the central gate.

Channelrhodopsins (ChR) are light-sensitive cation channels used in optogenetics, a technique that applies light to control cells (e.g., neurons) that have been modified genetically to express those channels.

Characterizing Channelrhodopsin Channel Properties Via Two-Electrode Voltage Clamp and Kinetic Modeling.

Two-electrode voltage clamp (TEVC) is a preferred electrophysiological technique used to study gating kinetics and ion selectivity of light-activated channelrhodopsins (ChRs). The method uses two intracellular microelectrodes to hold, or clamp, the membrane potential at a specific value and measure the flow of ions across the plasma membrane. Here, we describe the use of TEVC and a simple solution exchange protocol to measure cation selectivity and analyze gating kinetics of the C1C2 chimera expressed in Xenopus laevis oocytes.

An optimized and automated approach to quantifying channelrhodopsin photocurrent kinetics.

Channelrhodopsins are light-activated ion channels that enable targetable activation or inhibition of excitable cells with light. Ion conductance can generally be described by a four step photocycle, which includes two open and two closed states. While a complete understanding of channelrhodopsin function cannot be understood in the absence of kinetic modeling, model fitting requires manual fitting, which is laborious and technically complicated for non-experts.

Efficient Fluorescence Detection of Aromatic Toxicants and Toxicant Metabolites in Human Breast Milk.

Once chemical contaminants are released into the environment, there are a number of concerns that arise regarding the environmental persistence of the contaminants, their known and suspected toxicities, and their potential disruption to the ecosystem. One class of contaminants that is of continuing concern is polycyclic aromatic hydrocarbons (PAHs), persistent organic pollutants that are significant components of oil spills. PAHs have been found in the breast milk of nursing mothers living in oil spill affected regions, and can harm the nursing children.

Detection of Medium-Sized Polycyclic Aromatic Hydrocarbons via Fluorescence Energy Transfer.

Reported herein is the use of proximity-induced non-covalent energy transfer for the detection of medium-sized polycyclic aromatic hydrocarbons (PAHs). This energy transfer occurs within the cavity of -cyclodextrin in various aqueous environments, including human plasma and coconut water. Highly efficient energy transfer was observed, and the efficiency of the energy transfer is independent of the concentration of -cyclodextrin used, demonstrating the importance of hydrophobic binding in facilitating such energy transfer.

Cyclodextrin-promoted energy transfer for broadly applicable small-molecule detection.

Reported herein is the development of non-covalent, proximity-induced energy transfer from small-molecule toxicants to organic fluorophores bound in the cavity of γ-cyclodextrin. This energy transfer occurs with exceptional efficiency for a broad range of toxicants in complex biological media, and is largely independent of the spectral overlap between the donor and acceptor. This generally applicable phenomenon has significant potential in the development of new turn-on detection schemes.

Cyclodextrin-enhanced extraction and energy transfer of carcinogens in complex oil environments.

Reported herein is the use of γ-cyclodextrin for two tandem functions: (a) the extraction of carcinogenic polycyclic aromatic hydrocarbons (PAHs) from oil samples into aqueous solution and (b) the promotion of highly efficient energy transfer from the newly extracted PAHs to a high-quantum-yield fluorophore. The extraction proceeded in moderate to good efficiencies, and the resulting cyclodextrin-promoted energy transfer led to a new, brightly fluorescent signal in aqueous solution. The resulting dual-function system (extraction followed by energy transfer) has significant relevance in the environmental detection and cleanup of oil-spill-related carcinogens.