If an antibody isn’t available in your preferred fluorophore, conjugation kits can provide a simple solution. Bio-Rad offers a wide range of conjungation kits that require minimal hands-on time. Learn more about these kits and how to use them.
Conjugation of proteins or antibodies of interest with various molecular labels is often necessary in biological research to facilitate detection or quantification of the labeled protein, its binding partners, or antigens in the case of labeled antibodies. Molecular labels such as fluorophores or biotin are covalently conjugated to proteins or antibodies through reactions with thiol or amine groups.
With the LYNX Rapid and Rapid Plus Conjugation Kits and ReadiLink Antibody Conjugation Kits, Bio-Rad offers two complementary, fast, and easy to use antibody conjugations systems that cover a wide variety of labels including the common fluorophores as well as enzymes and biotin conjugations. Save valuable time by quickly conjugating your label of choice using these kits with minimal hands-on time.
LYNX Rapid and Rapid Plus Conjugation Kits are available in a wide range of options including common fluorophores, enzymes, and biotin/streptavidin conjugations, suitable for use in flow cytometry, ELISA, western blotting, immunohistochemistry, and immunofluorescence. Identical protocols for small and large scale (up to milligram quantities of antibody) conjugations allow for fast one-step conjugation of proteins and antibodies using a method that is superior to traditional kits and techniques. In contrast to conventional conjugation, LYNX Conjugation Kits offer consistent results with no post-conjugation clean-up process required; therefore, the antibodies are ready to use immediately.
Conjugate your antibodies in 3 easy steps with only 30 seconds hands-on time and no purification required. The total conjugation time is fifteen minutes with the LYNX Rapid Plus Conjugation Kits or 3 hours with the LYNX Rapid Conjugation Kits, however the reaction may run overnight without any adverse effects.
ReadiLink Antibody Conjugation Kits offer ten unique fluorescence conjugation options for small volumes. Quickly label your antibody of interest in two easy steps in just over an hour with the unique chemistry of ReadiLink Dyes. The excitation wavelengths and narrow emissions spectra of the fluorophores ranging from violet to far red are ideal for multicolor flow cytometry. The infrared excitable conjugations are suitable for westerns, ELISA, and in vivo imaging.
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Direct immuno-fluorescence staining of cells and blood for flow cytometry
Applicable where the fluorophore is directly linked to the primary antibody e.g. RPE, FITC and Alexa Fluor® conjugates. RPE conjugates should always be handled in the dark.
This method provides a general procedure for use with the majority of Bio-Rad reagents. In some cases specific recommendations are provided on product datasheets, and these methods should always be used in conjunction with the product and batch specific information provided with each vial. A certain level of technical skill and immunological knowledge is required for the successful design and implementation of these techniques; these are guidelines only and may need to be adjusted for particular applications. Specific methodology for blood appears in [ ] brackets.
Flow cytometry generally requires bright fluorophores that are excitable by one laser with a narrow emission wavelength to allow multicolor panel building. Below is a handy guide to the range of fluorophores Bio-Rad offers, including our new StarBright™ Dyes, that are suitable for flow cytometry, grouped by the laser used to excite them.
Additional fluorophore information can be found on specific webpages organized by the laser that excites them. This includes the maximal emission wavelength, relative brightness, ZE5 Cell Analyzer filter used for detection, similar or incompatible fluorophores, and our antibodies available conjugated to them, helping you select the right fluorophore for your experiment.
Tutorials for building multicolor flow cytometry panels always highlight the importance of antigen density — but why is it so important?
The number of antigens, or target molecules that a cell carries directly correlates to the intensity of the positive population and will determine the optimal fluorophore you should use for each marker. As a general rule you should pair bright fluorophores (e.g. PE) with low expressing markers and dimmer fluorophores (e.g. Pacific Blue) with highly expressed markers. Careful choice of fluorophores will help with the resolution of your cell populations. It is possible for bright fluorophores to be paired with highly expressed antigens, but better to avoid pairing dim fluorophores with low abundance antigens.
The guide provides advice on how to measure antigen density and lists the antigen density of some common markers.
To optimize staining in flow cytometry antibody titration is recommended. While antibodies will bind to high affinity targets on a cell, if they are present in excess they will also bind to low affinity targets. This results in an increase in background fluorescence and consequently a reduction in your ability to resolve populations, especially if there are subtle differences. Furthermore, if the antibody concentration is too high, it may result in a false negative prozone effect.
It is therefore important to use the antibodies at the right concentration. Although antibodies are sold with a recommended dilution and it is a good starting point, it may not be optimal for your cell type or protocol, therefore titration is an essential step to optimize your staining.
Before you build your panels it is critically important to have as clear an idea as possible of what is required to identify your population of interest. For example, are you looking at one cell type or is it a subset, are you looking at an activation marker or a change in cell frequency, are the markers co-expressed or do you even know the expression pattern?
Ideally, when building multicolor panels, it is best to separate fluorophore excitation across lasers, and where possible, the emission across the detectors. This will minimize the amount of spillover and therefore compensation you will need to do. It will also reduce the effect that fluorescence spread will have on your data. However, as you increase the number of fluorophores in your panel, this will not always be possible. Therefore other considerations need to be included in your design.
Multicolor flow cytometry is the analysis of multiple fluorescent parameters in one sample. Building large flow cytometry panels can be daunting because each additional fluorophore you add to your panel has the potential to influence another fluorophore.
Join our 45 minute webinar to learn which fluorophores are compatible with each other, how they interact and can affect your staining and how to obtain optimal resolution of signal. Furthermore, we will show you how dump channels, fluorophore brightness, antigen density, marker expression patterns and instrument configuration can all contribute to improving your panel design.
This webinar is recommended for both novices and researchers with some experience of flow cytometry.
Sebastian obtained his degree from the Institute of Technology, Linköping University, Sweden, followed by an MSc in Medical Biology from the same institute. He then moved to Freiburg, Germany where he obtained his PhD in Immunology and Molecular Biology at the Max Planck Institute of Immunobiology and Epigenetics.
The focus of his thesis was the role of microRNA in innate immunity and immunopathology. He then left academia and started work as a dedicated flow cytometry specialist, before joining Bio-Rad in 2016 as the flow cytometry specialist for Scandinavia, Eastern Europe, Israel, and South Africa.
The ability to select antigen density and fluorophores based on brightness, combined with automatic exclusion of incompatible fluorophores, will help you build larger panels with confidence.
Find the right fluorophore for your application using our new interactive, fluorescence spectraviewer with hundreds of fluorophores to choose from.
Bio-Rad’s new spectraviewer is the only spectraviewer to allow a multi-laser view and support three applications in a single tool.
The ability to view in a multi-laser format allows you to check fluorophore compatibility, including potential issues due to cross-laser excitation, and predict compensation.
Bio-Rad has over 4,000 antibodies validated for flow cytometry as well as helpful resources to guide you through your flow cytometry experiments. These resources as well as listings of antibodies, kits, and controls can be accessed from our dedicated flow cytometry page.