Plasma Membrane

The plasma membrane is a thin semi-permeable membrane that separates the interior of all cells from their extracellular environment. It is comprised of a phospholipid bilayer that is embedded throughout with proteins, such as ion channels, carrier proteins and receptor proteins, that are responsible for carrying out specific membrane. It provides structural support and protection for all cells, is responsible for maintaining ionic homeostasis, and is an integral component in cell adhesion, cell-cell communication, ion conductivity and cell signaling pathways.

Live Cell Plasma Membrane Staining

AAT Bioquest Cell Navigator™ Plasma Membrane Staining kits are designed to rapidly and uniformly label the plasma membrane in living cells without the cell-type differences exhibited by lectins. These kits, which employ our novel Cellpaint™ plasma membrane stains, may be used as a segmentation tool for high-content screening (HCS) or to stain cellular plasma membranes for standard fluorescence microscopy. The fluorescence staining in cell membranes is well-preserved after fixation with formaldehyde, enabling multiplexing with other fluorescent conjugates or proteins.

Key Features of Cell Navigator™ Plasma Membrane Staining Kits

• Bright fluorescence with high signal-to-noise ratios
• High photostability for stable signal generation
• Suitable for staining plasma membranes in suspended or attached live cells
• Uniform staining of plasma membrane across a broad range of mammalian cell types
• Staining well-retained in plasma membrane after fixation
• Available in green, orange and red fluorescence to facilitate multicolor staining

Cellpaint™ Orange	Cellpaint™ Green	Cellpaint™ Red
Live HeLa cells were stained with Cellpaint™ Orange, then fixed in 4% formaldehyde and costained with Nuclear Green™ DCS1.	Live HL-60 cells were stained with Cellpaint™ Green.	Live HeLa cells were stained with Cellpaint™ Red.

Fluorescent WGA for Live and Fixed Cells

Wheat germ agglutinin (WGA) is a ∼36 kDa lectin used extensivly in cell biology. Its high affinity for N-acetyl-D-glucosamine and sialic acid residues on glycoconjugates is routinely exploited for labeling the cell membranes of mammalian cells, gram-positive bacteria and yeast bud scars, as well as, skeletal and cardiac sacrolemma and fibrotic scar tissue. When conjugated to AAT Bioquest iFluor™ dyes, fluorescent WGA conjugates exhibit superior brightness, photostability and water-solubility, outperforming Alexa Fluor® WGA conjugates and other spectrally similar conjugates. iFluor™ dye-labeled WGA are suitable for immunoassays, IHC, ELISA and Western Blot.

Key Features of iFluor™ WGA Conjugates

• Bright fluorescence with high signal-to-noise ratios and resistance to photobleaching and pH change
• Conjugates useful in live and fixed cells that have not been permeabilized
• Withstands fixations and permeabilization
• Can serve as a anterograde or retrograde neuronal tracer for neuronal mapping studies
• Available in a range of colors to support multiplex and colocalization studies with other fluorescent conjugates or proteins

iFluor™ 488 WGA Conjugate		iFluor™ 647 WGA Conjugate
Live HeLa cells were stained with iFluor™ 488 WGA conjugate (green) and Hoechst 33342 (blue).		Live HeLa cells were stained with iFluor™ 647 WGA conjugate (red) and Hoechst 33342 (blue).

Alexa Fluor® wheat germ agglutinin conjugates for live and fixed cells.

Lipophilic Tracers – DiO, DiI, DiA, DiD, DiR and DiS

DiA, DiI, DiO, DiD and DiR are a family of dialkylcarbocyanines dyes used extensivly for labeling hydrophobic structures such as cell membranes, and as an anterograde or retrograde neuronal tracer in living and fixed cells and tissues. Once applied to cells, these dyes diffuse rapidly and laterally within the plasma membranes resulting in detailed uniform staining of the entire cell surface. Staining is specific as these dyes do not transfer via gap junctions or to unlabeled cells, unless the membrane of the labeled cell is disturbed. In addition to membrane staining and neuronal tracing, lipophilic carbocyanines have been successfully used in cytotoxicity assays, labeling lipoproteins, cell adhesion studies, tracing cell migration and fluorescence recovery after photobleaching (FRAP) assays.

Spectroscopic properties of dialkylcarbocyanines:

• Extremely high extinction coefficients
• Polarity-dependent fluorescence
• Short excited-state lifetimes
• DiO, DiI, DiD and DiR exhibit distinct green, orange, red and infrared fluorescence, respectively, to support multicolor imaging and flow cytometric analysis of live cells

Table 3. Lipophilic tracers for labeling cell membranes in live and fixed cells and tissues.

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