Recombinant Protein L from Peptostreptococcus magnus binds immunoglobulins (Ig) primarily through kappa light chain interactions without interfering with the antigen binding site of Igs. Specifically it has been shown to bind strongly to human kappa light chain subclasses I, III, and IV and also to most kappa chains from other species such as rat and mouse. This recognition of certain kappa light chains means that rProtein L can bind to a wider range of Ig classes and subclasses from a variety of species than any other commercially available Ig binding protein.
A comprehensive list of the binding properties of protein L and other commercially available Ig-binding proteins is found in the folowing tables.

Product list:

• Larger sizes of Protein L and Protein L-agarose are available on request.

rProtein L™ (lyophilized)

Features:

• Containing four Ig-binding domains
• Binds to many classes of Ig via the kappa chain (IgG, IgM, IgA, IgE, IgD)
• Binds to the variable domain of kappa light chains, without interfering with antigen binding
• Can be coupled to gel matrices for affinity purification
• Can be conjugated to marker molecules for detection
• Does not bind to bovine Ig’s

Applications:

• Purification and detection of IgG, IgM, IgA, IgE, IgD containing kappa light chains
• Purification and detection of Fab and scFv fragments containing kappa light chains
• Purification and detection of monoclonal antibodies direct from media supplemented with FCS

Molecular weight: 34 174
Isoelectric point: 4.8
Purity: >95% (SDS-PAGE, IEF)
Binding affinity: 2-3 x 10⁹ M^-1 to human IgG
Storage/stability: Stable for at least 3 years in lyophilized form at 4°C

rProtein L™ - agarose

Immobilised rProtein L provides a convenient matrix for column purification, immunoprecipitation or batch absorption. It can be regenerated many times without lack of activity. The binding capacity is 5-20 mg IgG/ml gel.

Applications:

• Puriication of IgG, IgM, IgA, IgE, IgD containing kappa light chains
• Purification of Fab and scFv fragments containing kappa light chains
• Purification of monoclonal antibodies direct from media supplemented with FCS
• Purification of human or mouse antibodies directly from transgenic cow, goat or sheep

Binding molecule: rProtein L containing four Ig-binding domains
Matrix: Cross-linked 4% beaded agarose
Bead size range: 45–165 µm
Coupling chemistry: Cyanogen bromide
Appearance: 50% (v/v) slurry of agarose beads in buffer
Storage buffer: 20% Ethanol (v/v) in PBS
Binding capacity: >5 mg of human IgG per ml of gel
Binding affinity: 2-3 x 10⁹ M^-1 to human IgG (free protein)
Storage/stability: Stable for at least 12 months at 4°C

rProtein L™ - HRP (horseradish peroxidase)

rProtein L™ - HRP is useful as a secondary or primary detection agent in ELISA, dot blots and Westerns. Provided in glycerol for easy and economical use without multiple freeze-thaw cycles.

Applications:

• Detection of IgG, IgM, IgA, IgE, IgD containing kappa light chains
• Detection of Fab and scFv fragments containing kappa light chains
• ELISA, dot, slot and Western blots

Binding molecule: rProtein L containing four Ig-binding domains
Marker molecule: Horseradish peroxidase
Working dilution: 1:1000-1:5000
Storage buffer: 50% glycerol in PBS
Binding affinity: 2-3 x 10⁹ M^-1 to human IgG (free protein)
Storage/stability: Stable for at least 2 years at -20°C

rProtein L™ - biotin

rProtein L™ - biotin can be used for increased sensitivity and flexibility in the detection of Igs with a Streptavidin - HRP/AP conjugate or in bioseparation with streptavidin coated beads or plates.

Applications:

• Pre-screening of phage display libraries
• Detection and purification of IgG, IgM, IgA, IgE, IgD containing kappa light chains
• Detection and purification of Fab and scFv fragments containing kappa light chains
• Purification using streptavidin coated (magnetic) beads or plates
• Detection using streptavidin conjugates for increased ensitivity

Binding molecule: rProtein L containing four Ig-binding domains
Marker molecule: NHS-SS-biotin
Working dilution: 1:3000-1:10 000
Concentration: 1mg rProtein L - biotin per ml of buffer
Storage buffer: PBS
Binding affinity: 2-3 x 10⁹ M^-1 to human IgG (free protein)
Storage/stability: Stable for at least 2 years at 4°C