AnaSpec Introduces Line of Membrane Potential Fluorescent Probes
Product News May 19, 2009
AnaSpec has introduced a wide selection of membrane potential fluorescent probes.
The plasma membrane of a cell typically has a transmembrane potential of approximately -70 mV (negative inside) as a consequence of K+, Na+ and Cl– concentration gradients that are maintained by active transport processes.
Increases and decreases in membrane potential (referred to as membrane hyperpolarization and depolarization, respectively) play a central role in many physiological processes, including nerve-impulse propagation, muscle contraction, cell signaling, and ion-channel gating.
Potentiometric optical probes enable researchers to perform membrane potential measurements in organelles and in cells that are too small to allow the use of microelectrodes such as the patch clamp technique. Moreover, in conjunction with imaging techniques, these probes can be employed to map variations in membrane potential across excitable cells and perfused organs with spatial resolution and sampling frequency that are difficult to achieve using microelectrodes.
Potentiometric probes are important tools for studying these processes, as well as for visualizing mitochondria (which exhibit transmembrane potentials of approximately -150 mV, negative inside matrix), cell-viability assessment, and high-throughput screening for new drug candidates. Potentiometric probes include: the cationic or zwitterionic styryl dyes, the cationic carbocyanines and rhodamines, the anionic oxonols and hybrid oxonols, and merocyanine 540.
Fluorescent indicators of membrane potential have been broadly classified as either slow (redistribution, or nernstian) or fast (electrochromic) dyes. There is a fundamental difference between these two distinct families of dyes with regard to the mechanism of their response to membrane potential, speed of the response, and the range of cellular characteristics.
A widely used fluorescent dye for measuring transmembrane potential, DiSBAC2(3), has a limitation of poor dynamic range in an assay environment in the absence of serum. AnaSpec has developed a novel membrane potential-sensitive fluorescent dye, HLB021-152, and successfully used it for homogeneous live-cell cAMP assay in both serum-containing and serum-free environment. Upon stimulating the endogenous or heterogenous GPCRs on CNG-channel-cloned HEK 293 cells with agonists, the fluorescent signal of HLB021-152 increased rapidly and had greater dynamic range than DiSBAC2(3). This new membrane potential-sensitive dye can be formulated for high throughput screening of GPCR modulators in both with serum and without serum environments.