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Zymosan A S. cerevisiae BioParticles™, fluorescein conjugate (Invitrogen™)

The Molecular Probes® BioParticles® product line consists of a series of fluorescently labeled, heat- or chemically killed bacteria and yeast in a variety of sizes, shapes, and natural antigenicities. These fluorescent BioParticles® products have been employed to study phagocytosis by fluorescence microscopy, quantitative spectrofluorometry, and flow cytometry.

We offer E. coli (K-12 strain), S. aureus (Wood strain, without protein A) and zymosan (S. cerevisiae) BioParticles® conjugates covalently labeled with a variety of different fluorophores (special care has been taken to remove free dye after conjugation). Unlike the fluorescence of fluorescein-labeled BioParticles® conjugates, which is partially quenched in acidic environments, the fluorescence of the Alexa Fluor®, BODIPY® FL, tetramethylrhodamine and Texas Red® dye conjugates is uniformly intense over the pH range from 3 to 10.

BioParticles Specifications:
• Label (Ex/Em): Fluorescein (~494/518 nm)
• Particle: Zymosan (S. cerevisiae)
Opsonizing reagent available


Using BioParticles Products
BioParticles® conjugates are provided as lyophilized powders. There are approximately 3 x 108 E. coli or S. aureus particles per mg solid and approximately 2 x 107 zymosan particles per mg solid. BioParticles® conjugates can be reconstituted in the buffer of your choice for use in phagocytosis assays. The fluorescence of BioParticles® conjugates that are bound to the surface of the cell (but not internalized) can be quenched by ethidium bromide, trypan blue, or other quenchers. In addition to cellular applications, fluorescent BioParticles® conjugates may be effective as flow cytometry calibration references when sorting bacteria and yeast mutants. These small particles may also be useful references for light scattering studies because their sizes and shapes differ in characteristic ways.

Find More BioParticles® Products
We offer a large range of dye-labeled and unlabeled E. coli (K-12 strain), S. aureus (Wood strain, without protein A), and zymosan (S. cerevisiae) BioParticles® products. Find out about these products and their applications by reviewing Probes for Following Receptor Binding and Phagocytosis—Section 16.1 in the Molecular Probes® Handbook.

For pH-sensitive endocytosis assays, see our pHrodo™ BioParticles® conjugates.

For Research Use Only. Not for human or animal therapeutic or diagnostic use.

Arcturus™ Paradise™ PLUS 2 Round Kit, amino allyl, no solvents (Applied Biosystems™)

The ARCTURUS® Paradise® PLUS Reagent System permits unprecedented gene expression analysis of millions of previously inaccessible samples. It is an integrated solution for gene expression studies from formalin-fixed, paraffin-embedded (FFPE) tissues, including reagents for tissue staining, RNA isolation and RNA amplification. Amplify RNA from as little as 5 ng of fixed RNA using methods that have been specially optimized to overcome the challenges of cross-linked templates.

This kit provides reagents for 2-round in-vitro transcription, and aminoallyl aRNA labeling.

Key product features:
• Accelerated discovery process – unlock the tissue archives to access previously inaccessible samples
• Simplified procedure – achieve unprecedented results in six steps
• Streamlined application – integrate seamlessly into current workflow
• Efficient workflow – secure downstream success with the Paradise® QC Kit
• Comprehensive system – benefit from the only complete system for formalin-fixed samples

Unlock the Tissue Archives
Currently, tens of millions of tissue samples with known outcomes are available in tissue archives. The Paradise® PLUS Reagent System enables microarray and qRT-PCR analysis of these previously inaccessible samples, allowing retrospective studies to accelerate discoveries.

Achieve Unprecedented Results in Six Steps
Only six steps are required to take you from sample to results (See Figure 1).

Integrate Seamlessly into Current Workflow
The Paradise® PLUS Reagent System is compatible with all major microarray platforms. Robust and reproducible results are achieved using tools and techniques commonly employed in today’s research laboratories (See Figures 2, 3, 4, and 5).

Secure Downstream Success with the Paradise® QC Kit
Not all FFPE samples contain high quality RNA. Identify the best samples for your studies using a simple, real-time PCR research technique, and then proceed with confidence using these pre-qualified samples (See Figure 6).

Benefit from the Only Complete System for Formalin-fixed Samples
The Paradise® PLUS Reagent System is the only available solution that provides all the components necessary to prepare RNA from formalin-fixed, paraffin-embedded tissue samples for gene expression analysis. To ensure successful microarray results, the system includes reagents optimized for exceptional recovery of RNA and superior RNA amplification.

Integrated Systems for Microgenomics
The Paradise® PLUS Reagent System is a validated as part of the ARCTURUS® Complete System for Microgenomics®, an integrated solution for utilizing small quantities of RNA for gene expression analysis. This system features the ARCTURUSXT™ Laser Capture Microdissection (LCM) Instrument to procure pure cell populations. Arcturus Systems for Microgenomics enable accurate and sensitive microarray assays that reveal molecular signatures otherwise obscured in whole tissue samples or cell mixtures.

For Research Use Only. Not for use in diagnostics procedures.

Click-iT™ Plus TUNEL Assay for In Situ Apoptosis Detection, Alexa Fluor™ 647 dye (Invitrogen™)

The Click-iT® Plus TUNEL assay detects apoptotic cells in tissue and cultured cell samples through the use of a small, highly specific labeling moiety and a bright fluorescent dye. After incorporation of the labeling moiety into DNA fragments, detection is achieved through a catalyzed “click” reaction using conditions mild enough to preserve the fluorescent signal from GFP or RFP.

More tools for apoptosis detection and measurement >

• Optimized for the detection of apoptotic cells in either tissue or cell samples
• Multiplex enabled—optimized to work with fluorescent dyes or proteins such as GFP and RFP
• Improved TUNEL assay—better label incorporation due to small reactive moiety
• Bright apoptotic signal—uses Alexa Fluor® dyes, resulting in a stable, non-photobleaching fluorescent signal
• Flexibility—the assay can be configured to test from 1 to 50 samples at a time

Fragmentation of cellular DNA is a hallmark of apoptosis. The TUNEL assay is the most widely used method to detect fragmented DNA in apoptotic cells in tissue samples. The TUNEL assay begins with incorporation of modified dUTP at the 3’-OH end of the fragmented DNA. The dUTP modification is often the addition of a fluorophore. And due to the size of the fluorophore, the modified dUTP can display lower than expected incorporation rates. These lower incorporation rates can affect the sensitivity of the TUNEL assay. Additionally, the fluorophores used in currently available TUNEL assays suffer from photobleaching and fluorescent spectral overlap issues, both of which reduce sensitivity and ability to multiplex the assay.

The Click-iT® Plus TUNEL assay was developed to address these issues. The assay uses dUTP modified with an alkyne group (a small bio-orthogonal functional group) that allows the nucleotide to be more readily incorporated. After incorporation, a highly specific click reaction between the alkyne group and an Alexa Fluor® picolyl azide fluorescent dye, and subsequent detection of that dye, results in a sensitive and specific assay for the detection of apoptotic cells. Because of the gentle reaction conditions, the Click-iT® Plus TUNEL assay enables multiplexing with fluorescent proteins or dyes.

The Click-iT® Plus TUNEL assay has been validated with several different formalin-fixed paraffin-embedded tissue types. In all cases the ability to multiplex with fluorescent proteins and dyes was preserved. Additionally, the ability to stain actin using fluorescent-labeled phalloidin was also preserved.

The Click-iT® Plus TUNEL assay contains all of the reagents needed to detect apoptotic cells from either tissue or cell samples. The reagents supplied in this kit can be used to test 50 samples and can be configured to test from 1 to 50 samples at a time.

CellTrace™ Blue Cell Proliferation Kit, for flow cytometry (Invitrogen™)

The CellTrace Blue Cell Proliferation Kit is used for in vitro and in vivo labeling of cells to trace multiple generations using dye dilution by flow cytometry. The CellTrace Blue reagent is specifically designed for excitation by a UV laser (at 355 nm or 375 nm), and it can be easily multiplexed with reagents and antibodies excited by other commonly used lasers.

• Superior performance—bright, single-peak staining enables visualization of multiple generations
• Long-term signal stability—well-retained in cells for several days post stain
• Versatile—multiple colors available to easily combine with antibodies or markers of cell function, such as GFP
• Simple, robust staining protocol

View a selection guide for all CellTrace Cell Proliferation Kits for flow cytometry.

Superior fluorescent staining
Successful proliferation analysis by dye dilution (see figure below) requires an extremely bright dye to distinguish fluorescently labeled cells from auto-fluorescence after several cell divisions. The intense fluorescent staining provided by CellTrace Blue dye enables the visualization of five or more generations of proliferating cells before the signal is overwhelmed by intrinsic cellular auto-fluorescence. Consistent, homogeneous staining results in very little fluorescence variation between cells in a population, so distinct generations can be seen without any requirement for complex modeling software.The recommended working concentration for peripheral blood mononuclear cells is 5–10 µM. However, as with all reagents used in flow cytometry, to achieve optimal signal, reagent titration is highly recommended.

Long-term signal retention
Unlike stains that label the lipid membrane of cells, CellTrace Blue stain easily crosses the plasma membrane and covalently binds inside cells where the stable, well-retained fluorescent dye provides a consistent signal, even after several days in a cell culture environment. CellTrace Blue dye binds covalently to all free amines on the surface and inside of cells and shows little cytotoxicity, with minimal observed effect on the proliferative ability or biology of cells.

Easy multiplexing with other fluorophores
The UV excitation and narrow emission of CellTrace Blue dye make it ideal for multiplexing as it lies outside the spectral emission profiles of most other dyes and fluorescent proteins.

Simple, robust staining protocol
The CellTrace Blue Cell Proliferation Kit contains convenient single-use vials of dry dye to permit small-scale experiments without preparing excess quantities of dye. A stock solution is prepared by dissolving the contents of a vial in anhydrous DMSO prior to use. To stain 1 mL of cells in protein-free medium, 1 µL of this stock solution is typically used. Cells should be stained for 20 minutes at room temperature with gentle agitation. A brief wash with complete medium will then quench any dye remaining in solution.

eBioscience™ Essential Human Th1/Th17 Phenotyping Kit (Invitrogen™)

The Invitrogen eBioscience Essential Human Th1/Th17 Phenotyping Kit is designed for flow cytometry-based identity testing of Type 1 and Type 17 T–helper cells (Th1/Th17). It leverages high quality eBioscience antibodies, isotype controls, cell stimulation reagents (induces cytokine production), and fixation/permeabilization reagents (for intracellular markers IfN-g and IL-17) and includes a ready-to-use protocol for experimental setup, gating strategy, and analysis.

Benefits include:
Proven performance―antibodies and supporting reagents designed for flow cytometry
Highly referenced antibodies―includes one of the most referenced clones for IL-17
Turnkey kit and protocol―contains reagents and standardized gating recommendations needed to perform flow cytometry characterization

pHrodo™ Red S. aureus Bioparticles™ Conjugate for Phagocytosis (Invitrogen™)

New pH-sensitive pHrodo® Red dye conjugates give faster and more accurate results than any other phagocytosis assay pHrodo® Red dye conjugates are non-fluorescent outside the cell, but fluoresce brightly red in phagosomes.

Get faster staining and more accurate results without the need for wash steps or quencher dye
• Specific detection of phagocytosis and endocytosis
• Reduced signal variability and improved timing in sensitive experiments
• Multiplex with green dyes such as GFP, Fluo-4, or calcein

The fluorescence of the novel pHrodo® Red dye dramatically increases as pH decreases from neutral to the acidic, making it an ideal tool to study phagocytosis and its regulation by drugs and/or environmental factors. The lack of fluorescence outside the cell eliminates the need for wash steps and quencher dyes. Use the ready-made pHrodo® Red S. aureus BioParticles® conjugates in imaging or flow applications, or pHrodo® Red SE, the activated succinimidyl ester, for labeling microorganisms or proteins of your choice.

Staphylococcus aureus BioParticles™ Opsonizing Reagent (Invitrogen™)

The Staphylococcus aureus (Wood strain without protein A) BioParticles® opsonizing agent is derived from highly purified rabbit polyclonal IgG antibodies and specifically designed to enhance the uptake of the S. aureus BioParticles® conjugates.

Dead Cell Apoptosis Kit with Annexin V APC and SYTOX™ Green, for flow cytometry (Invitrogen™)

This flow cytometry product detects the externalization of phosphatidylserine in apoptotic cells using recombinant annexin V conjugated to red laser-excited allophycocyanin, and dead cells using SYTOX™ Green nucleic acid stain. Apoptotic cells are detected by annexin V binding to externalized phosphatidylserine, and late apoptotic and necrotic cells have compromised membranes that permit SYTOX™ Green stain access to cellular nucleic acids. After exposing a cell population to APC annexin V and SYTOX™ Green stain, live cells show little or no fluorescence, apoptotic cells show red fluorescence and very little green fluorescence, and late apoptotic cells show a higher level of red and orange fluorescence. These populations can easily be distinguished using a flow cytometer that has both 488 nm and 633 nm excitation sources (an argon-ion laser and a HeNe laser).

View a selection guide for all apoptosis assays for flow cytometry.

BacLight™ RedoxSensor™ CTC Vitality Kit (Invitrogen™)

The BacLight™ RedoxSensor™ CTC Vitality Kit provides effective reagents for evaluating bacterial cell health and vitality that can withstand fixation procedures. Briefly, healthy cells respiring via the electron transport chain will absorb and reduce CTC into an insoluble, red fluorescent formazan product. Cells not respiring or respiring at slower rates will reduce less CTC and consequently produce less fluorescent product, giving a semi-quantitative estimate of healthy vs. unhealthy bacteria. Green- and blue-fluorescent nucleic acid stains are included as counterstains to assist differentiation of cells from debris and calculating total cell numbers.

View additional information about all microbiology assays for flow cytometry.

Arcturus™ Paradise™ Plus stain, slide jars & slides (Applied Biosystems™)

The ARCTURUS® Paradise® PLUS FFPE LCM Staining Kit offers a simple solution developed to stain formalin-fixed paraffin-embedded (FFPE) tissues before proceeding with laser capture microdissection (LCM) and downstream molecular analysis. FFPE samples introduce unique challenges for gene expression profiling, including chemical modification and fragmentation of RNA molecules. Archival of FFPE samples adds to these challenges through increased RNA degradation over time.

Key product features:
• Provide Superior Staining while Preserving RNA
• Secure Downstream Success with the Paradise® QC Kit
• Benefit from the Only Complete System for Formalin-fixed Samples

Provide Superior Staining while Preserving RNA
The Paradise® PLUS FFPE LCM Staining Kit offers a simple solution developed to stain FFPE tissues before proceeding with laser microdissection and downstream molecular analysis. It is a fast penetrating stain that provides good contrast by differential staining of nuclei (purple) and cytoplasm (light pink). By minimizing the exposure of tissues to water where nucleases may be activated, the Paradise® PLUS FFPE LCM Staining Kit helps to preserve RNA integrity that may be otherwise compromised when using longer staining protocols.

Secure Downstream Success with the Paradise® QC Kit
Identify the best samples for your studies using the Paradise® PLUS Sample Quality Assessment Kit (QC Kit). The QC Kit uses a simple, real-time PCR technique to check the quality of RNA in your FFPE sample before staining and LCM. Proceed with confidence knowing your FFPE samples have high quality RNA.

Benefit from the Only Complete System for Formalin-fixed Samples
The Paradise® PLUS Reagent System is the only available solution that provides all the components necessary to prepare RNA from FFPE tissue samples for gene expression analysis. To ensure successful microarray results, the system includes reagents optimized for exceptional recovery of RNA and superior RNA amplification.

Integrated Systems for Microgenomics
The Paradise® PLUS Reagent System is validated as part of the ARCTURUS® System for Microgenomics, an integrated solution for utilizing small quantities of RNA for gene expression analysis. ARCTURUS® Systems for Microgenomics enable accurate and sensitive microarray assays that reveal molecular details otherwise obscured in whole tissue samples or cell mixtures.

For Research Use Only. Not for use in diagnostics procedures.

eBioscience™ Essential Human T-Cell Phenotyping Panel (Invitrogen™)

The Invitrogen eBioscience Essential Human T-Cell Phenotyping Panel is designed for flow cytometry-based identity testing of T-cells. It leverages high quality eBioscience antibodies and a ready-to-use protocol for experimental setup, gating strategy, and analysis.

Benefits include:
Proven performance―antibodies designed for flow cytometry
Highly referenced antibodies―eBioscience portfolio contains trusted fluorochrome-conjugated antibodies for immunology and oncology research
Turnkey kit and protocol―contains standardized gating recommendations needed to perform flow cytometry characterization

Click-iT™ EdU Alexa Fluor™ 647 HCS Assay (Invitrogen™)

The Click-iT® EdU Alexa Fluor® 647 HCS Assay is a superior alternative to traditional proliferation assays that is optimized for high-content imaging applications. In this assay the modified thymidine analogue EdU is efficiently incorporated into newly synthesized DNA and fluorescently labeled with a bright, photostable Alexa Fluor® dye in a fast, highly-specific click reaction. This fluorescent labeling of proliferating cells is accurate and compatible with antibody methods due to the mild click protocol.

• Simple—works the first time, every time, in less time
• Efficient—no denaturation steps or harsh treatment required
• Content-rich results—better preservation of cell morphology, antigen structure, and DNA integrity
• Consistent—not dependent on variable antibody lots for detection

The most accurate proliferation-detection methods are based on the incorporation and measurement of nucleoside analogues in newly synthesized DNA, with bromodeoxyuridine (BrdU) a commonly used analogue. BrdU-labeled DNA is quantitated using anti-BrdU antibodies following DNA denaturation by harsh methods (HCl, heat, or enzymes) to expose the BrdU molecules. This step is time consuming and difficult to perform consistently. The harsh treatment can also adversely effect sample integrity and quality, which makes co-staining with other antibodies challenging.

Superior Proliferation Methodology
The Click-iT® EdU Alexa Fluor® 647 HCS Assay provides a superior alternative to BrdU assays for measuring cell proliferation. EdU (5-ethynyl-2'-deoxyuridine) is a nucleoside analog of thymidine and is incorporated into DNA during active DNA synthesis. With Click-iT® EdU, mild fixation and detergent permeabilization is sufficient for the small molecule-based Click-iT® EdU detection reagent to gain access to the DNA. As a consequence, the Click-iT® EdU HCS assay is not only easy to use, but more accurate and compatible with cell cycle analysis and other intracellular or extracellular targets for truly content-rich results.

The kit is optimized for high-content imaging applications; visit the Click-iT® technology area of our website for kits designed for fluorescence microscopy, microplate, or flow cytometry platforms.

Learn more about Click-iT® technology

Notes:
The Click-iT® assay can be used on cells in culture or in vivo following administration of EdU by feeding or injection methods.
The Click-iT® assay can be used with BrdU in dual pulse experiments by using the ant-BrdU (clone MoBu-1) antibody, which does not cross react with EdU.
The Click-iT® technology is compatible with immunohistochemical, immunocytochemical, and fluorescent dyes that are fixation tolerant or designed for fixed-cell labeling.

Click-iT™ EdU Alexa Fluor™ 647 Flow Cytometry Assay Kit (Invitrogen™)

The Click-iT® EdU Alexa Fluor® 647 Flow Cytometry Assay Kit provides a simplified, more robust assay for analyzing DNA replication in proliferating cells as compared to traditional BrdU methods. Newly synthesized DNA is analyzed using the 633/5 nm laser of the flow cytometer.

Accurate--Superior Results compared to BrdU Assays
Fast--Results in as little as 90 minutes
Economical--More assays per kit

View selection guide for all Click-iT™ EdU and Click-iT™ Plus EdU assays for flow cytometry.

An Advanced Method Giving You Results Superior to BrdU
The most accurate method of proliferation analysis is direct measurement of DNA synthesis. Originally, this was performed through incorporation of radioactive nucleosides, i.e., 3H-thymidine. This method was replaced by antibody-based detection of the nucleoside analog bromodeoxyuridine (BrdU). The Click-iT® EdU Flow Cytometry Assay Kits are novel alternatives to the BrdU assay. EdU (5-ethynyl-2´-deoxyuridine) is a thymidine analog which is incorporated into DNA during active DNA synthesis. Detection is based on click chemistry: a copper catalyzed covalent reaction between an azide and an alkyne. In this application, the alkyne is found in the ethynyl moiety of EdU, while the azide is coupled to Alexa Fluor ® 488, Alexa Fluor® 647, or Pacific BlueTM dyes. Standard flow cytometry methods are used for determining the percentage of S-phase cells in the population (Fig 1).

Mild Conditions Allow Use with Cell Cycle Dyes and Antibodies
The advantages of Click-iT® EdU labeling are readily evident while performing the assay (Fig 2). The small size of the dye azide allows for efficient detection of the incorporated EdU using mild conditions, while standard aldehyde-based fixation and detergent permeabilization are sufficient for the Click-iT® detection reagent to gain access to the DNA. This is in contrast to BrdU assays that require DNA denaturation (using HCl, heat, or digestion with DNase) to expose the BrdU so that it may be detected with an anti-BrdU antibody. Sample processing for the BrdU assay can result in signal alteration of the cell cycle distribution as well as destruction of antigen recognition sites when using the HCl method. In contrast, the easy-to-use EdU cell proliferation kit is compatible with cell cycle dyes. This EdU assay kit can also be multiplexed with antibodies against surface and intracellular markers.

Quick and Simple Protocol
The Click-iT® EdU protocol is based on the aldehyde fixation and detergent permeabilization steps for immunohistochemical antibody labeling, but EdU is compatible with other
fixation/permeabilization agents including saponin and methanol. In just five steps you’ll be ready to analyze your cell proliferation data:

• Treat cells with EdUM
• Fix and permeabilize cells
• Detect S-phase cells with Click-iT® detection cocktail for 30 min
• Wash once
• Analyze

Get Accurate Results Economically
By increasing the number of assays per kit, the Click-IT® EdU Alexa Fluor® 647 Flow Cytometry Assay Kit is less expensive than the traditional BrdU assays making them ideal for large experiments.

For research use only. Not intended for any human or animal therapeutic of diagnostic use.

Click-iT™ EdU Cell Proliferation Kit for Imaging, Alexa Fluor™ 488 dye (Invitrogen™)

The Click-iT EdU Cell Proliferation Kit for Imaging is a superior alternative to traditional proliferation assays that is optimized for fluorescence microscopy applications. In this assay the modified thymidine analogue EdU is efficiently incorporated into newly synthesized DNA and fluorescently labeled with a bright, photostable Alexa Fluor® dye in a fast, highly-specific click reaction. This fluorescent labeling of proliferating cells is accurate and compatible with antibody methods due to the mild click protocol.

• Simple—works the first time, every time, in less time
• Efficient—no denaturation steps or harsh treatment required
• Content-rich results—better preservation of cell morphology, antigen structure, and DNA integrity
• Consistent—not dependent on variable antibody lots for detection

The most accurate proliferation-detection methods are based on the incorporation and measurement of nucleoside analogues in newly synthesized DNA, with bromodeoxyuridine (BrdU) a commonly used analogue. BrdU-labeled DNA is quantitated using anti-BrdU antibodies following DNA denaturation by harsh methods (HCl, heat, or enzymes) to expose the BrdU molecules. This step is time consuming and difficult to perform consistently. The harsh treatment can also adversely effect sample integrity and quality, which makes co-staining with other antibodies challenging.

Superior Proliferation Methodology
The Click-iT EdU Cell Proliferation Kit for Imaging provides a superior alternative to BrdU assays for measuring cell proliferation. EdU (5-ethynyl-2'-deoxyuridine) is a nucleoside analog of thymidine and is incorporated into DNA during active DNA synthesis. With Click-iT® EdU, mild fixation and detergent permeabilization is sufficient for the small molecule-based Click-iT® EdU detection reagent to gain access to the DNA. As a consequence, the Click-iT® EdU imaging kit is not only easy to use, but more accurate and compatible with cell cycle analysis and other intracellular or extracellular targets for truly content-rich results.

This kit is optimized for fluorescence microscopy applications; visit the Click-iT® technology area of our website for kits designed for high-content imaging, fluorescence microplate, or flow cytometry platforms.

Learn more about Click-iT technology >
Find more tools for image-based detection of proliferating cells >

Notes:
The Click-iT® assay can be used on cells in culture or in vivo following EdU administration by feeding or injection methods.
The Click-iT® assay can be used with BrdU in dual pulse experiments by using the anti-BrdU (clone MoBu-1) antibody, which does not cross react with EdU.
The Click-iT® technology is compatible with immunohistochemical, immunocytochemical, and fluorescent dyes that are fixation tolerant or designed for fixed cell labeling.

Ultra-Sensitive ABC Peroxidase Rabbit IgG Staining Kit (Thermo Scientific™)

Thermo Scientific Pierce ABC Staining Kits include reagents for the avidin-biotin complex (ABC) technique, a highly sensitive method for immunohistochemical detection with biotinylated secondary antibodies.

Pierce ABC Staining Kits are highly sensitive, produce very low background staining and have rapid avidin-biotin interactions. Standard Kits contain only the two essential reagents (avidin and biotinylated HRP) can be used with nearly any species of biotinylated secondary antibody. The Ultra-Sensitive ABC Peroxidase Staining Kits are approximately five times more sensitive than the regular-senstivity kit, enabling more dilute primary antibodies to be used while producing equal staining intensity. Ultra-Sensitive Kits are offered as a Standard Kit and as Complete Kits, which contain biotinylated secondary antibodies and appropriate block serum for use with mouse or rabbit antibodies, respectively.

Related Products
ABC Peroxidase Standard Staining Kit
Ultra-Sensitive ABC Peroxidase Standard Staining Kit
Ultra-Sensitive ABC Peroxidase Mouse IgG Staining Kit

eBioscience™ Annexin V-Biotin Apoptosis Detection Kit (Invitrogen™)

Annexins are a family of calcium-dependent phospholipid-binding proteins, which bind to phosphatidylserine (PS) to identify apoptotic cells. In healthy cells, PS is predominantly located along the cytosolic side of the plasma membrane. Upon initiation of apoptosis, PS loses its asymmetric distribution in the phospholipid bilayer and translocates to the extracellular membrane, which is detectable with fluorescently labeled Annexin V. In early stages of apoptosis, the plasma membrane excludes viability dyes such as propidium iodide (PI) and 7-AAD, therefore cells which display only Annexin V staining (PI/7-AAD negative) are in early stages of apoptosis. During late-stage apoptosis, loss of cell membrane integrity allows Annexin V binding to cytosolic PS, as well as cell uptake of PI and 7-AAD. Annexin V staining, paired with 7-AAD or PI is widely used to identify apoptotic stages by flow cytometry.

Host
E.coli

Conjugate
Biotin

Purity
> 98% pure

Molecular Mass
35.8 kDa

Reported Application
Flow Cytometric Analysis

Histogene™ Refill Kit, includes dehydration chemicals & stain only (Applied Biosystems™)

This kit contains only the dehydration chemicals and stain used with the ARCTURUS® HistoGene® LCM Frozen Section Staining Kit. Designed as a fast-penetrating stain, this kit provides excellent contrast while preserving nucleic acid integrity and retaining low-abundance mRNAs.

Key product features:
• Optimized process—provide superior staining while preserving RNA
• Comprehensive kit—simplify tissue staining and dehydration
• High-quality RNA yield—retain low-abundance mRNA and maintain RNA integrity
• Versatile application—obtain high-quality RNA from many tissue types
• Modular design—use with other ARCTURUS® products to produce superior microarray data

Provide Superior Staining while Preserving Nucleic Acids
HistoGene® Staining Solution has been developed by ARCTURUS® to stain tissues for LCM subsequently used as sources of nucleic acids. It is a fast-penetrating stain that provides good contrast by differential staining of nuclei (purple) and cytoplasm (light pink). By minimizing the exposure of tissues to water where nucleases may be activated, HistoGene® stain helps to preserve nucleic integrity that may be otherwise compromised when using longer staining protocols.

Retain Low-abundance mRNA
RT-PCR analysis of specific genes from cells captured from tissues processed using the HistoGene® LCM Frozen Section Staining Kit shows retention of both low-abundance mRNA and higher-abundance species. The mRNA profile of HistoGene® samples appears free of degradation.

Maintain RNA Integrity
Tissues prepared for LCM using HistoGene® LCM Frozen Section Staining Kit reagents, supplies and instructions yield high quality RNA.

Obtain High-quality RNA from Many Tissue Types
ARCTURUS® has validated the HistoGene® Kit by examining RNA integrity on many tissue types. All tissues tested to date using the HistoGene® Kit have yielded quality RNA. Validated tissue types include (Table 1):

Part of the Arcturus® System for Microgenomics
The HistoGene® LCM Frozen Section Staining Kit is part of the ARCTURUS® Complete System of Microgenomics and is designed to seamlessly work together to produce high quality expression microarrays. With the PicoPure® RNA Isolation Kit, you can recover a high yield of RNA from as few as 10 cells in a minimal volume. The RiboAmp® RNA Amplification Kit can amplify picograms of your RNA sample into micrograms of amplified RNA (aRNA) that is ready for labeling and hybridization to microarrays. ARCTURUS® instruments and kits increase the reliability and reproducibility of gene expression studies.

For Research Use Only. Not for use in diagnostics procedures.

eBioscience™ Mouse Regulatory T Cell Staining Kit #1 (Invitrogen™)

The FJK-16s antibody reacts with mouse/rat Foxp3 also known as FORKHEAD BOX P3, SCURFIN, and JM2; cross reactivity of this antibody to other proteins has not been determined. Foxp3 a 49-55 kDa protein, is a member of the forkhead/winged-helix family of transcriptional regulators, and was identified as the gene defective in ‘scurfy’ (sf) mice. Constitutive high expression of Foxp3 mRNA has been shown in CD4+CD25+ regulatory T cells (Treg cells), and ectopic expression of Foxp3 in CD4+CD25- cells imparts a Treg phenotype in these cells.

Immunoblotting with FJK-16s antibody has mapped the epitope to amino acids 75-125 of the mouse Foxp3 protein. In the human, this region has been shown to be alternatively spliced at the mRNA level. Both the alternatively-spliced and non-spliced isoforms are present in the CD4+CD25+ subset of lymphocytes. Preliminary RT-PCR experiments have not revealed this alternatively-spliced isoform in mouse splenocytes, suggesting different gene regulation in the mouse and human.

Intracellular staining of mouse splenocytes with FJK-16s using the mouse Foxp3 staining sets and protocol reveals approximately 2% of total splenocytes in the C57Bl/6 strain and approximately 3-5% in the BALB/c mouse strain. Multicolor flow cytometric analysis demonstrates approximately 90% of the CD4+CD25+ cells and 4% of the CD4+CD25- cells staining with FJK-16s. B220+, CD11b+, CD11c+, and Ly6G/Gr-1+ cells do not show significant co-staining with FJK-16s. These data are consistent with a recent report which follows expression of Foxp3 using a GFP knock-in (Fontenot et al, 2005).

FJK-16s cross-reacts with rat Foxp3 This has been demonstrated by intracellular staining of Foxp3 and flow cytometry of rat splenocytes using the same method and reagents as used for mouse tissue. Please note that the CD4 and CD25 antibodies included in this kit only recognize the mouse antigens. For staining rat tissue, please use (CD4 FITC cat. 11-0040 and CD25 APC cat. 17-0390)

The anti-mouse Foxp3 Staining Set has been formulated and optimized for the staining of mouse splenocytes with the FJK-16s monoclonal antibody

Not included:
Isotype controls for anti-CD4 (rat IgG2a, cat. 11-4321) and anti-CD25 (rat IgG1, cat. 17-4301)

Host
Rat

Isotype
IgG2a

Reactivity/Species
Mouse

Reported Application
Intracellular Staining Followed by Flow Cytometric Analysis

eBioscience™ BrdU Staining Kit for Flow Cytometry APC (Invitrogen™)

The eBioscience BrdU Staining Kit for Flow Cytometry contains the necessary reagents and buffers for identifying and examining proliferating cells of mammalian species by flow cytometric analysis. Cycling cells are incubated with 5-bromo-2’-deoxyuridine (BrdU), a synthetic analog of thymidine which incorporates into newly synthesized genomic DNA during the S-phase of mitosis. Following DNA denaturation, the cells are stained for BrdU incorporation along with any other cell surface and/or intracellular targets of interest.

This kit is optimized to achieve brighter staining compared to traditional protocols.

Reactivity/Species
Bovine, Canine, Cow, Human, Monkey, Mouse, Non-human primate, Rat, Rhesus

Conjugate
APC

Laser
Red Laser

Emit
660 nm

Excite
633 - 647 nm

Reported Application
Intracellular Staining Followed by Flow Cytometric Analysis

LIVE/DEAD™ Fixable Red Dead Cell Stain Kit, for 488 nm excitation (Invitrogen™)

The LIVE/DEAD™ Fixable Red Dead Cell Stain Kit is used to determine the viability of cells prior to the fixation and permeabilization required for intracellular antibody staining or prior to elimination of biohazardous materials using formaldehyde fixation. This kit has been optimized and validated for use with a blue laser flow cytometer.

• Stable—dyes are freeze dried in separate vials to maintain stability

• Robust—staining pattern is the same before and after fixation

• Bright signal—allows for easy distinction between live/dead cells in single channel

View a selection guide for all fixable viability dyes for flow cytometry.

Stable
Unlike products that are sold in solution, the LIVE/DEAD™ Fixable Red Stain has been conveniently packaged in 40-test vials to help ensure the stability and performance of the dye over time. Amine reactive dyes in solution will lose their effectiveness over a short period of time, therefore it is recommended to completely use the vial once rehydrated. If this is not possible, aliquot the vials in small volumes and store at -80°C, avoiding freeze-thaw cycles.

Robust
Dead cell discriminator stains can lose sensitivity after treatment with fixatives such as formaldehyde or ethanol-based fixation methods required for intracellular phosphorylation studies. The LIVE/DEAD™ Fixable Red Stain is an amine reactive dye that binds covalently to intracellular and extracellular amines, and the staining pattern is preserved following formaldehyde fixation.

Optimal brightness
The LIVE/DEAD™ Fixable Red stain was selected based on its fluorescent properties to provide a bright signal when excited with a yellow, green, or blue 488 nm laser. The red-fluorescent reactive dye has an excitation maximum of ~595 nm, making it ideal for use with the yellow laser, and an emission of ~615 nm, allowing collection in the 610 or 630 BP filter. LIVE/DEAD™ Fixable Red Dead Cell stain is also excited well with the blue 488 nm laser. Since live and dead cells can be discriminated using a single dye and a single channel of a flow cytometer, it is an ideal choice for multi-color experiments.

How it works
In cells with compromised membranes, the dye reacts with free amines both in the cell interior and on the cell surface, yielding intense fluorescent staining. In viable cells, the dye's reactivity is restricted to the cell-surface amines, resulting in less intense fluorescence. The difference in intensity is typically greater than 50-fold between live and dead cells, allowing for easy discrimination.

Colors available
LIVE/DEAD™ Fixable Dead Cell Stains are available in a wide variety of colors to meet your multi-color panel needs.

Metal Enhanced DAB Substrate Kit (Thermo Scientific™)

Thermo Scientific Pierce Metal-Enhanced DAB Substrate Kit uses cobalt and nickel chloride in a special formulation of diaminobenzidine peroxidase substrate that yields intense color for immunohistochemical staining.

Features of the Metal-Enhanced DAB Substrate Kit :

Incredible sensitivity—fifty times more sensitive than the traditional DAB method and thiry times more sensitive than other metal-intensified versions of DAB
Low background, high intensity—get a crisp dark brown-black precipitate that is more intense than the dull brown precipitate when using DAB without enhancement. And, even with the increased intensity, background is almost nonexistent
Only two components—simply mix the two liquid components and your working solution is ready to use
Six-hour stability—the innovative working solution is stable for more than six hours at room temperature, while other DAB substrates must be used immediately

To prepare the product, the 10X Metal Enhanced Substrate Solution is diluted with the Pierce Stable Peroxide Buffer prior to use, and the special formulation allows the 1X substrate to be stable for at least 6 hours at room temperature. The background color of the substrate does not increase and, unlike typical metal enhanced DAB methods, the reactivity is unchanged (1,2). The resulting precipate is a dark brown-black that is more intense than the brown color from DAB alone. The intensity not only increases, but the background is also reduced, which increases the signal-to-noise ratio and makes screening tissue or membrane antigens easier.

Arcturus™ Paradise™ PLUS 2 Round Kit, Cy3 labeling, no solvents (Applied Biosystems™)

The ARCTURUS® Paradise® PLUS Reagent System with Microarray Labeling permits unprecedented gene expression analysis of millions of previously inaccessible samples. The Paradise® PLUS Reagent System is an integrated solution for gene expression studies from formalin-fixed, paraffin-embedded (FFPE) tissues, including reagents for tissue staining, RNA isolation and RNA amplification. Amplify RNA from as little as 5 ng of fixed RNA using methods that have been specially optimized to overcome the challenges of cross-linked templates.

Key product features:
• Microarray Labeling, Gene Expression Profiling
• Flexibility in Assay Format
• Integrated Systems for Microgenomics

Microarray Labeling, Gene Expression Profiling
The Paradise® PLUS RNA Amplification Kit may be configured to include Turbo Labeling™ for use in microarray experiments. Turbo Labeling™ Kits offer a proprietary, non-enzymatic technology optimized for the labeling of unmodified, amplified RNA (aRNA) for gene expression profiling. The unmodified aRNA is labeled post-amplification, thereby avoiding the need to incorporate modified nucleotides during RNA amplification. The use of unmodified nucleotides in the amplification process results in unmodified aRNA with higher yields and longer aRNA fragments, thus providing better representation of the mRNA transcript for downstream analysis.

Flexibility in Assay Format
Turbo Labeling™ Kits include reagents to support labeling of 12 samples using either Cy™3⁄Cy™5 dyes or Biotin for hybridization to cDNA or oligonucleotide arrays.

Integrated Systems for Microgenomics
The Paradise® PLUS Reagent System is validated as part of the ARCTURUS® Complete System for Microgenomics®, an integrated solution for utilizing small quantities of RNA for gene expression analysis, and features the ARCTURUSXT™ Laser Capture Microdissection (LCM) Instrument to procure pure cell populations. ARCTURUS®' Systems for Microgenomics enable accurate and sensitive microarray assays that reveal molecular otherwise obscured in whole tissue samples or cell mixtures.

For Research Use Only. Not for use in diagnostics procedures.

MDR1 Vesicular Transport Assay Reagent Set (Gibco™)

The MDR1 Vesicular Transport Assay Reagent Set is a ready-to-use kit containing all reagents needed for vesicular transport assay except for the vesicles themselves. The reagent set can be used for vesicular transport assay using radioisotope-labeled or non-labeled compound. This kit has enough material to perform 100 vesicular transport assays.

Use The MDR1 Vesicular Transport Assay Reagent Set to:

• Investigate the transporter interactions of your drug candidates
• Assess potential for transporter-mediated drug-drug interactions
• Obtain high quality results with a large signal to noise ratios

Concept Behind ABC Transporter Vesicles
ABC transporter vesicles are easy-to-use, efficient reagents for early assessment of a drug candidate’s substrate and drug interaction potential. While ABC transporters typically mediate the export of substrates out of cells, transporters expressed on these inside-out vesicles import substrates into the vesicles. It is therefore possible to quantitatively evaluate transport activity for your compound by determining the amount incorporated into the vesicles.

Clear and Reliable Results
Prepared from Sf9 cells which have been engineered to over-express specific ABC transporters, these "inside-out" vesicles provide high levels of transporter activity with low background, giving you a clear signal if your compound is a substrate or inhibitor of a specific efflux transporter.

Kit Compatibility
Our MDR1 Vesicular Transport Assay Reagent Set is designed for use with MDR1 Vesicles. The 100 vesicular transport assays that can be performed with this kit will require two MDR1 Vesicle products.

For Research Use Only. Not intended for animal or human therapeutic or diagnostic use.

Escherichia coli (K-12 strain) BioParticles™, BODIPY™ FL conjugate (Invitrogen™)

The Molecular Probes® BioParticles® product line consists of a series of fluorescently labeled, heat- or chemically killed bacteria and yeast in a variety of sizes, shapes, and natural antigenicities. These fluorescent BioParticles® products have been employed to study phagocytosis by fluorescence microscopy, quantitative spectrofluorometry, and flow cytometry.

We offer E. coli (K-12 strain), S. aureus (Wood strain, without protein A) and zymosan (S. cerevisiae) BioParticles® conjugates covalently labeled with a variety of different fluorophores (special care has been taken to remove free dye after conjugation). Unlike the fluorescence of fluorescein-labeled BioParticles® conjugates, which is partially quenched in acidic environments, the fluorescence of the Alexa Fluor®, BODIPY® FL, tetramethylrhodamine and Texas Red® dye conjugates is uniformly intense over the pH range from 3 to 10.

BioParticles Specifications:
• Label (Ex/Em): BODIPY® FL (~505/513 nm)
• Particle: E. coli (K-12 strain)
Opsonizing reagent available


Using BioParticles Products
BioParticles® conjugates are provided as lyophilized powders. There are approximately 3 x 108 E. coli or S. aureus particles per mg solid and approximately 2 x 107 zymosan particles per mg solid. BioParticles® conjugates can be reconstituted in the buffer of your choice for use in phagocytosis assays. The fluorescence of BioParticles® conjugates that are bound to the surface of the cell (but not internalized) can be quenched by ethidium bromide, trypan blue, or other quenchers. In addition to cellular applications, fluorescent BioParticles® conjugates may be effective as flow cytometry calibration references when sorting bacteria and yeast mutants. These small particles may also be useful references for light scattering studies because their sizes and shapes differ in characteristic ways.

Find More BioParticles® Products
We offer a large range of dye-labeled and unlabeled E. coli (K-12 strain), S. aureus (Wood strain, without protein A), and zymosan (S. cerevisiae) BioParticles® products. Find out about these products and their applications by reviewing Probes for Following Receptor Binding and Phagocytosis—Section 16.1 in the Molecular Probes® Handbook.

For pH-sensitive endocytosis assays, see our pHrodo™ BioParticles® conjugates.

For Research Use Only. Not for human or animal therapeutic or diagnostic use.

Hypoxia Green Reagent for Flow Cytometry

Hypoxia Green Reagent for Flow Cytometry is an antibody-independent reagent used to detect low levels of oxygen levels in live cells. The membrane-permeant probe releases rhodamine as oxygen levels decrease, resulting in a fluorogenic response. Hypoxia is a characteristic of many diseases, including cardiovascular disease and tumor-mediated immunosuppression and is critical to tumor survival and growth.

• Sensitive, fixed, end-point assay
• Detects decreases in oxygen in live cells
• Fluorogenic, non-antibody based probe

Premo™ Autophagy Sensor LC3B-GFP (BacMam 2.0) (Invitrogen™)

Premo™ Autophagy Sensor combines the selectivity of a LC3B-green fluorescent protein (GFP) chimera with the transduction efficiency of BacMam technology, enabling unambiguous visualization of this protein. BacMam reagents (insect Baculovirus with a Mammalian promoter) are non-replicating in mammalian cells and thus safe to handle. They are also non-cytotoxic and ready-to-use. Unlike expression vectors, BacMam reagents enable titratable and reproducible expression and offer high co-transduction efficiency, therefore multiple BacMam reagents can readily be used in the same cell. Recent improvements made to the BacMam system enable efficient transduction in a wider variety of cells including neurons and neural stem cells (NSCs) with an easy, one-step protocol. Now, to visualize autophagy, simply add the BacMam LC3B-GFP to the cells and incubate overnight for protein expression. Each Premo™ Autophagy Sensor Kit includes the BacMam LC3B-FP, a control BacMam LC3B (G120A)-FP (mutation on the control BacMam LC3B prevents cleavage and subsequent lipidation during normal autophagy, thus protein localization should remain cytosolic and diffuse) and chloroquine diphosphate to artificially induce autophagosome accumulation.

Vybrant™ Apoptosis Assay Kit #4, YO-PRO™-1/Propidium Iodide (Invitrogen™)

The Vybrant Apoptosis Assay Kit #4 detects apoptosis on the basis of changes that occur in the permeability of cell membranes. This kit contains ready-to-use solutions of both YO-PRO-1 and propidium iodide nucleic acid stains. YO-PRO-1 stain selectively passes through the plasma membranes of apoptotic cells and labels them with moderate green fluorescence. Necrotic cells are stained red-fluorescent with propidium iodide.

View a selection guide for all apoptosis assays for flow cytometry.

CyQUANT™ Direct Cell Proliferation Assay (Invitrogen™)

Experience a more convenient workflow for your high-throughput cytotoxicity and proliferation screening projects with the CyQUANT® Direct Cell Proliferation Assay–no washes, cell lysis, temperature equilibrations, or radioactivity required. DNA-based assays have been shown to be among the most sensitive cell health indicators and data concordance with metabolically based assays is excellent. The CyQUANT® Direct assay is a highly sensitive and robust method to assess cell growth, viability, or compound toxicity in a range of applications, from high throughput screening to bioproduction.

Features of the CyQUANT® Direct Cell Proliferation Assay include:

• More convenient workflow for high-throughput screening–no washes, cell lysis, temperature equilibrations, or radioactivity required
• Rapid protocol, high sensitivity and dynamic range
• Measures independent of metabolic state of cells on standard fluorescent plate readers
• Multiplex assays using a spectrally distinct fluorescent or a luminescent readout

Rapid and convenient, with a large dynamic range
The CyQUANT® Direct assay is a fluorescence-based proliferation and cytotoxicity assay for microplate readers with a linear detection range from less than 100 to 20,000 cells per well in most cell types. The no-wash, homogenous format and fast add-mix-read protocol makes the CyQUANT® Direct assay ideal for HTS applications. The assay can be completed in one hour, with no washes, no cell lysis, or temperature equilibrations required. The signal is stable for several hours, affording additional work flow convenience.

How it works
The CyQUANT® Direct assay is based on a cell-permeant DNA-binding dye in combination with a masking dye reagent. Cellular DNA is highly regulated and estimates of cell numbers based on DNA are very accurate. The masking dye blocks staining of dead cells or cells with compromised cell membranes resulting in only healthy cells being stained. The CyQUANT® Direct assay, therefore, measures proliferation as well as membrane integrity, another measure of cell health. Users of metabolically based cell health assays can readily compare historical data with results from the CyQUANT® Direct assay, as concordance assays based on metabolism or energy (ATP) has been shown to be excellent. Furthermore, it is possible to multiplex with spectrally distinct fluorescent probes or luminescence assay kits because cells are not lysed. Furthermore, the fluorescent signal allows the user to switch between HTS and HCS plate readers if multiplex assays require different platforms.

Angiogenesis Starter Kit (Gibco™)

The Gibco® Angiogenesis Starter Kit contains the reagents and protocols necessary to perform various angiogenesis assays. Designed to address the needs of both the occasional user as well as the most experienced researcher, this combination of high quality products is easy to use and cost effective. Detailed protocols for the tube formation assay and cell migration are available below.

What’s Included:

• Gibco® Large Vessel Endothelial Supplement (LVES), 50X, 11 ml, ready to use
• Gibco® Medium 200 basal media, 500 ml
• Gibco® Human Umbilical Vein Endothelial Cells (HUVEC), 1 vial, 5 x 105 cells
• Geltrex® LDEV-Free Reduced Growth Factor Basement Membrane Matrix, 5 ml

Large Vessel Endothelial Supplement and Medium 200
Gibco® LVES is a 50X, complete, ready-to-use media supplement optimized for use with Gibco® Medium 200. This blended supplement has been designed to deliver optimal cell growth and to enable superior cell performance for angiogenesis applications such as cell migration and tube formation. LVES contains fetal bovine serum, hydrocortisone, human epidermal growth factor, basic fibroblast growth factor, heparin, and ascorbic acid.

Human Umbilical Vein Endothelial Cells
Gibco® Human Umbilical Vein Endothelial Cells are cryopreserved at the end of the primary culture. Upon thawing, they are guaranteed to be >70% viable and capable of a minimum of 16 population doublings. Cells are derived from tissue obtained from accredited institutions with IRB-approved donor programs. Quality control of these cells includes testing for mycoplasma, sterility, endotoxin, hepatitis B and C, and HIV. Additionally, the cells are positive for von Willebrand factor (vWf), positive for CD31, negative for a-actin, and positive for dil-Ac-LDL uptake.

Geltrex® LDEV-Free Matrix
Geltrex® LDEV-Free Reduced Growth Factor Basement Membrane Matrix is a soluble, reduced growth factor, lactate dehydrogenase-elevating virus-free basement membrane extract used in a wide variety of cell culture applications for promotion and maintenance of many cell types, including primary epithelial cells, endothelial cells, and stem cells. It can be diluted for use as a coating matrix for culture vessels or used undiluted as a thick gel preparation to create a more physiologically relevant environment for angiogenesis assays.

LIVE/DEAD™ FungaLight™ Yeast Viability Kit, for flow cytometry (Invitrogen™)

The LIVE/DEAD® FungaLight™ Yeast Viability Kit enables researchers to easily, reliably and quantitatively distinguish live and dead yeast in minutes by flow cytometry. The kit contains solutions of the SYTO® 9 green-fluorescent nucleic acid stain and the red-fluorescent nucleic acid stain, propidium iodide. These stains differ both in their spectral characteristics and in their ability to penetrate healthy yeast cells. When used alone, the SYTO® 9 stain generally labels all yeast in a population - those with intact membranes and those with damaged membranes. In contrast, propidium iodide penetrates only yeast with damaged membranes, causing a reduction in the SYTO® 9 stain fluorescence by fluorescence resonance energy transfer (FRET) when both dyes are present. As a result, yeast with intact membranes stain fluorescent green, whereas yeast with damaged membranes stain fluorescent red.