The Fab-TACS® technology offers

• Highly specific and reproducible isolations with minimal contamination in a source-independent manner
• Quick and simple protocol, without magnetic beads or ultracentrifugation, no extra device needed
• Label-free exosomes with intact biological functions due to reversible reagents

Exosomes have an endosomal origin and are released by many different cell types, participating in different physiological and/or pathological processes. They range between 30 and 150 nanometers in diameter and belong to the smallest extracellular vesicles. Exosomes possess surface proteins that partly originate from plasma membranes during endocytosis. The tetraspanins CD9, CD63 and CD81 are specially enriched in the membrane of these vesicles and are often used as biomarkers.

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In the field of exosome research it is essential to achieve highly pure and functional exosome populations. However, common exosome isolation problems include complex and time-consuming protocols, impure vesicle populations or non-reversible binding of vesicles to the selection reagents. Therefore the application of different exosome isolation methods, such as differential centrifugation, size exclusion chromatography, filtration or exosome isolation by PEG (polyethylene glycol (PEG)ylation), is limited.

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In contrast, the Fab-TACS® exosome isolation technology allows a quick isolation of pure and unlabeled exosomes in a source independent manner. Our Fab-TACS® technology offers a magnet-free, positive selection exosome isolation technique with reversible binding of reagents to the target.
The Fab-based technology represents an affinity chromatography system for non-magnetic isolation of exosomes. It is based on Twin-Strep-tagged surface protein-specific Fab fragments, which reversibly capture and release the exosomes. The technology delivers label-free exosomes with intact biological functions in a standardized manner. It is possible to perform exosome isolation from cell culture media, serum or plasma.

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Minimal contamination by other EVs
The particle size is a critical factor in evaluating the quality of isolated exosomes. 99% of particles isolated from cell culture supernatants of mesenchymal stem cells (MSCs) fell within the range of 30 – 150 nm (A). This indicates strong exosome enrichment. In comparison, only 32% exosome-sized particles were detected after purification with a commercially available PEGylation kit (B), implying contamination by larger extracellular vesicles.

High content of exosome proteins
Since other same-sized non-exosome contaminants may contribute to the pool of isolated particles, we tested for the presence of marker proteins CD63 and Alix after exosome isolation from MSC supernatant using our Fab-TACS® technology. Both proteins were clearly present within the purified particles (C), confirming their exosome phenotype.

Reproducible results
Depending on MSC donor, cell culture supernatant compositions may vary. Purified exosomes of three independent isolations from different MSC donors were very comparable in their size ranging from 86 nm to 90 nm average diameter. All isolations yielded around 94% of particles between 30 and 150 nm in size (D). Besides high purity, this demonstrates a high reproducibility of our Fab-TACS® exosome isolation technology. It also shows a comparable exosome isolation yield throughout different experiments.

Source-independent application
Important exosome sources also include a variety of human bodily fluids such as blood and urine. Similar to isolations from cell culture supernatants, 96% of particles retrieved by exosome isolation from serum of humans exhibited the typical exosome size of 30 to 150 nm (E). This shows that with our Fab-TACS® isolation technology only one exosome isolation kit is needed for different vesicle sources.

Quick and simple
Due to the surface protein specificity of the Fab-TACS® isolation technology, time-consuming centrifugation steps or extensive sample preparations are not necessary. The exosome isolation protocol is easy and straightforward, permitting efficient and high quality results also for newcomers in the field of exosome research. Additionally, the short processing time minimizes the stress of cargo contained within the exosomes.

Fab-TACS® – Traceless Affinity Cell Selection – technology represents an affinity chromatography system for non-magnetic isolation of immune cells. It is based on Twin-Strep-tagged Fab fragments, which reversibly capture and release the target cells. The Fab-TACS® technology delivers label-free, non-activated cells suitable for immunological or cell biological assays.

Fab-TACS® technology perfectly combines the benefits of positive and negative cell separation and therefore allows the purification of:

• Highly viable cells
• Highly pure cells directly from whole blood
• Label-free cells due to low affinity Fabs

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A standard problem in cell preparations is limited purity and recovery, which causes variability in quality and potency of cell products. Highly pure populations can be obtained best using positive separation techniques. However, the latter are often based on high affinity antibodies whose usage causes unfavorable effects like strong and almost irreversible binding to cells, cell stimulation as well as receptor blockade. IBA’s Strep-tag®/Strep-Tactin® system is the platform for the novel traceless affinity cell selection (Fab-TACS®) of cells. Fab-TACS® enables cell separation without the need for high affinity antibodies and ferromagnetic beads. In contrast, Fab-TACS® uses an immune-affinity chromatography based on Strep-tagged Fab-fragments (Fab-Streps) for reversible capture and release of target cells.

In more detail, a Strep-Tactin® coated matrix made of cell-grade agarose specifically binds low affinity Fab fragments. However, multiple Fab-Streps on IBA’s unique agarose bind target cells with high avidity. Hence, if a single-cell suspension passes through the agarose matrix target cells adhere to the matrix based on the exclusive binding of the Fab-Strep to the target cell. Non-target cells are efficiently washed away. In a final step, the addition of biotin causes the elution of the target cells and the Fab-Streps spontaneously self-dissociate from the cell surfaces due to their reduced affinity.
Thus, the innovative Fab-TACS® procedure delivers label-free, non-activated target cells in a standardized manner of highly reproducible quality from a variety of single cell suspensions, e.g. whole blood or buffy coat allowing a multitude of downstream applications.

Watch this YouTube video to get further insights into the Fab-TACS^® technology:

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Columns for either Fab-TACS® Gravity or FABian® are filled with a Strep-Tactin® coated matrix made of cell-grade agarose. Strep-tagged Fab fragments (Fab-Streps) specifically bind to the matrix. Subsequently, whole blood or samples from other sources, e.g. mouse spleen cells pass through the column. Target cells adhere to the matrix based on the exclusive binding of the Fab-Strep to the target cell. Non-target cells are efficiently washed away. In a final step, the addition of biotin causes the elution of the target cells and the Fab-Streps. After elution, the Fab-Streps self-dissociate from the cell surfaces. The label-free authentic target cells are now ready for further downstream applications.

Streptamer®: fully reversible reagents for the selection of uncompromised, authentic cells

In order to study cell-cell interactions, it is essential to gain unmanipulated cells from cell isolation. The Streptamer® technology covers different stages in cell research from cell isolation to cell expansion and cell staining. With this method the cells preserve authentic properties, full effector function as well as viability and serial positive selections of even rare cell subsets is possible. By adding low concentrations of biotin, the isolation reagents dissociate rapidly from the cell surface, leaving authentic cells ready for further experiments.

Receptor-specific T cell isolation:
Fab Streptamers®

Antigen-specific CD8+ T cell isolation:
MHC I Streptamers®

• No stimulation of cells after cell separation
• Optimal preservation of cell effector function
• Improved viability of cells
• High reproducibility

Example of T cell isolation with magnetic Fab Streptamers®:

Full reversibility in detail
Low affinity Strep-tagged Fab fragments or MHC molecules are employed to convey the specificity to the target cell population. In order to achieve a high binding affinity for proper cell isolation, the Strep-tag® fragments bind to a multimerized Strep-Tactin®, a streptavidin derivative. Due to this a high binding avidity of the fragment is achieved. Upon addition of low concentrations of biotin, isolation reagents dissociate rapidly from the cell surface. This reversibility enables sequential positive cell selections with magnetic beads.

A modular system for cell selection AND staining
Fab-Streps or MHC-Streps can be combined with bead-labeled Strep-Tactin® for magnetic isolation. Biotin is offered as stock solution with the Streptamer® Solution Set which is used for removing the cell isolation reagents. This modular system enables the combination of multiple receptor- or antigen-specific staining and isolation products, making your experiments more convenient and economic. All reagents can be purchased as single products or assembled in ready-to-use staining or isolation kits.

The in vitro generation of a large number of functional T cells is important for basic research as well as for therapeutic approaches. Commonly used stimulatory reagents for resting T cells are magnetic beads carrying αCD3 and αCD28 monoclonal antibodies.

Choose the Streptamer® CD3/CD28 Kit for T cell expansion. If you need a flexible CD3:CD28 ratio. cat.no. 6-8900-000

• This Kit comes with the three reagents as single, not pre-mixed reagents.
• Your advantage: you can modify the CD3 : CD28 Fab-Strep ratio according to your needs, or you simply follow our recommendations.

Choose the Streptamer® CD3/CD28 Premix for T cell expansion if want to benefit from ready-to-use reagents and pre-mixed components. cat.no. 6-8901-000

Capacity: 1.6×107 cells total

• This reagent is ready-to-use, i.e. all three components are already pre-mixed.
• Your advantage: you can benefit from a quick protocol with the ready-to-use reagent.

Our peptides are synthesized as single peptides as presented by the MHC class I allele.

• peptides of 9-10 amino acids
• purity > 80 %
• endotoxin free

Choose between following categories:

• virus and tumor specific antigens
• Listeria specific antigens
• human and murine alleles

NOW AVAILABLE: SARS-CoV-2 peptides for T cell stimulation
The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a virus that currently needs detailed research to understand underlying immune responses and to provide possible treatment options. In addition, the development of an efficient vaccine is essential to prevent future outbreaks. Studying CD8+ cytotoxic T cell activation and proliferation in response to different virus-derived peptides can help to identify the parts of a virus that elicit a strong immune response. This information is required for efficient vaccine design and contributes to the understanding of the infection biology. We provide different SARS-CoV-2-derived peptides for T cell stimulation to support the ongoing research regarding the new coronavirus.

Streptamer®: fully reversible reagents for uncompromised staining intensity and accuracy
Fluorescent cell staining provides a multitude of information, which is important for the analysis of cell functions. In order to achieve reliable and reproducible results, the cells have to be unmanipulated. The Streptamer® technology offers excellent staining intensities for cell staining and can be completely removed from the cells with no reagents remaining on the cells. This completely reversible cell staining technology preserves the functional status of the cells after staining.

Receptor-specific T cell staining:
Fab Streptamers®

Antigen-specific CD8+ T cell staining:
MHC I Streptamers®

• high specificity
• high sensitivity
• high reproducibility
• no leftover of staining reagents on the cells after FACS sorting
• optimal preservation of cell effector function
• improved viability of cells

The Streptamer® principle: full reversibility
Low affinity Strep-tagged Fab fragments or MHC molecules are multimerized with Strep-Tactin®, a streptavidin derivative, to generate multimers with high binding avidity. Strep-Tactin® is conjugated with the fluorochromes APC or PE for cell staining. By adding low concentrations of biotin, which competes with high affinity for the binding of Strep-tag® to Strep-Tactin®, the staining reagents can be completely removed from the cell surface. This reversibility enables multiple cell stainings with different Strep-Tactin® fluorochromes from the same sample.

The Streptamer® reagents: a modular system
Fab-Streps or MHC-Streps are combined with fluorescence-labeled Strep-Tactin® for cell staining. Biotin is offered as stock solution with the Streptamer® Solution Set which is used for removal of cell staining reagents. This modular reagent system enables the economic generation of multiple receptor- or antigen-specific staining and isolation reagents. All reagents can be purchased as single products or assembled in ready-to-use staining and isolation kits.

Vectors for Recombinant Protein Expression
Expression vectors for IBA’s proprietary affinity tags Strep-tag® and Twin-Strep-tag® are available for a multitude of expression hosts. IBA provides in addition vectors for other common affinity tags:

Additional available features:

• Secretion signals (ompA, BM40) and
• Different resistances for E. coli (Ampicillin and Chloramphenicol)

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• Cloning of GOI into selected pDSG-IBA vector
• Transfection of MEXi 293E cells in MEXi-TM transfection medium
• Transient expression in MEXi-TM and later on in MEXi-CM culture medium
• Purification of GOI (e.g. on immobilized Strep-Tactin®XT binding a Twin-Strep-tag® fusion protein)

• It comprises a perfectly matched HEK293E cell line, cell culture media and expression vectors to provide high protein yields without further optimization
• Transient expression for time and cost efficient protein production
• Efficient nuclear import and extrachromosomal replication due to vector encoded EBV origin of replication (oriP) and EBNA-1 provided by MEXi-293E cells
• Multiple expression vectors with different features
• Optimized for Twin-Strep-tag®/Strep-Tactin® system for highly pure proteins
• IP free system with attractive prices

Obtained protein yield of SEAP after purification: 143 mg/l.
Secreted alkaline phosphatase (SEAP) was fused with a C-terminal Twin-Strep-tag® (TST) and the BM40 secretion signal via cloning into pDSG-IBA102. MEXi 293E cells were transfected in MEXi-TM transfection medium with 25 kDa PEI (polyethylenimine) in 17 ml culture volume. Afterwards the cells were first incubated for 4 hours at 37°C before MEXi-CM culture medium was added. The cells were kept at 37°C for 7 days in order to obtain high protein yields. For purification, the cells were pelleted and the supernatant, containing the SEAP protein, was harvested. SEAP protein was finally purified using a Gravity flow Strep-Tactin® Superflow® high capacity column.

The obtained protein yield of the rat antibody was 96 mg/l represented by heavy (HC) and light chain (LC). 
A rat monoclonal antibody (mAb) was cloned into the pDSG-IBA102 vector in order to fuse the heavy chain (HC) C-terminally with the Twin-Strep-tag® and the BM40 secretion signal. The transfection of MEXi 293E cells was performed in MEXi-TM transfection medium with 25 kDa PEI in a 250 ml culture volume. Afterwards the cells were incubated for 4 hours at 37°C and then 250ml MEXi-CM culture medium was added. When the cells reach a cell density of 3×106 cells/ml. At this concentration the culture was shifted to 32°C and incubated until day 10.
In order to divide the cells from the supernatant the cell suspension was centrifuged according to the MEXi manual. The supernatant was used for protein purification via a Gravity flow Strep-Tactin® Superflow® high capacity column. WET FRED was used to facilitate loading of the large supernatant volume onto the column.

Obtained protein yield of POI after purification: 318 mg/l.
The protein of interest (POI) comprises a C-terminal Twin-Strep-tag® and the BM40 secretion signal. It was cloned into pDSG-IBA102. 1050 ml of MEXi-TM medium was inoculated with MEXi 293E cells. Subsequently, plasmid DNA was added followed by addition of 25 kDa linear PEI. The cells were incubated for 4 hours in MEXi-TM medium at 37°C and 5 % CO2 in an orbital shaking incubator. Cells were diluted to 7.5 x 105 cells/ml by the addition of one volume MEXi-CM culture medium and kept at 37°C for 7 days. Afterwards, they were pelleted and the supernatant, containing POI, was harvested. POI was finally purified using Strep-Tactin® Superflow® XT. The figure shows the elution fractions (E1-E3). A dilution of 1:10 was prepared for E1 and E2 before application to SDS-PAGE.

Comparison of IBA’s mammalian expression system MEXi with a competitor system:

*costs implement Medium, Cells, DNA and working time

Applicable for direct StarGate cloning and combinatorial two-step StarGate cloning

pDSG Expression Vector List
pDSG expression vectors are perfectly matched with our MEXi system for optimal expression results.

Purification of expressed recombinant proteins is one of the main applications in biochemistry. It is commonly performed with affinity chromatography by use of different protein peptide tags. Besides His-tag, IBA’s unique Strep-tag® system is a powerful tool for purification of highly pure recombinant proteins. The Strep-tag® system is based on the strongest non-covalent interaction known in nature, which is the interaction of biotin with streptavidin. Two versions of the Strep-tag® are available: Strep-tag®II and Twin-Strep-tag®. The Strep-tag®II consists of eight amino acids (Trp-Ser-His-Pro-Gln-Phe-Glu-Lys) whereas the Twin-Strep-tag® includes this motif two times in series connected with a linker and therefore is composed of 28 amino acids. This peptide tags exhibit high affinities to the resins Strep-Tactin® and Strep-Tactin®XT which are engineered streptavidins.
IBA is the original manufacturer of the Strep-tag® system and provides a complete portfolio around protein purification using this affinity system:

• 1 ml Strep-Tactin®XT 4Flow® gravity flow column
• 1x Buffer W (Strep-Tactin®/Strep-Tactin®XT Wash Buffer)
• 1x Buffer BXT (Strep-Tactin®XT Elution Buffer with Biotin)
• 1x Buffer XT-R (Strep-Tactin®XT Regeneration Buffer)
• Strep-Tactin® conjugated with HRP (for Western Blot Detection)
• Short Protocol

Key benefits:

• Higher affinity and protein yield even for large proteins
• Higher capacity for large proteins
• Broad pH stability (pH 4-10)
• Higher pressure stability compared to Strep-Tactin® Sepharose
• Cost efficient

Comparison of the yield of a large human glycoprotein (129 kDa) purified with Strep-Tactin®XT Superflow® high capacity or Strep-Tactin®XT 4Flow® high capacity. With Strep-Tactin®XT 4Flow® high capacity, a 5-fold higher yield can be achieved.

Technology
Magnetic Strep-tag® purification at its best! – A superior tool for small scale batch purification with high demands on protein purity.
Magnetic beads are a common tool to isolate proteins or complexes via a pull-down, immunoprecipitation (IP) or co-immunoprecipitation (Co-IP). The advantage of a magnetic beads based pull-down/IP is the simple and reproducible handling of the product. Due to the magnetic core of the beads no centrifugation step is required any more, the beads can be easily separated with a magnetic separator and the risk of disturbing the pellet or loss of beads within the wash step is close to zero.

MagStrep “type3” XT beads are Strep-Tactin®XT coated magnetic beads with the following characteristics:

• high binding capacity (up to 0.85 nmol/μl beads, corresponding to 30 μg of a 30 kDa protein)
• very low non-specific protein binding due to an improved coating
• flexible elution conditions (under denaturing conditions by boiling in SDS gel loading buffer or under native conditions with biotin)
• high affinity for Twin-Strep-tag® – due to new Strep-Tactin®XT

These characteristics lead to very good purification results. MagStrep “type3” XT magnetic beads are therefore a convenient tool for small-scale purifications with high demands on binding specificity as required in pull-down assays and high-throughput screenings.

References

See where to use MagStrep “type 3” XT beads!

• Protein purification

Essuman K, Summers DW, Sasaki Y, Mao X, Yim AKY, DiAntonio A, Milbrandt J. (2018) TIR Domain Proteins Are an Ancient Family of NAD⁺ -Consuming Enzymes. Curr Biol. 28(3): 421-430 [Link]

Zhang Y, Ptacin JL, Fischer EC, Aerni HR, Caffaro CE, San Jose K, Feldman AW, Turner CR, Romesberg FE. (2017) A semi-synthetic organism that stores and retrieves increased genetic information. Nature. 551(7682): 644-647. [Link]

• Pull-down assay

González M, Brito N, González C. (2017) The Botrytis cinerea elicitor protein BcIEB1 interacts with the tobacco PR5-family protein osmotin and protects the fungus against its antifungal activity. New Phytol. 215(1): 397-410. [Link]

Jeong, S. J., Park, S., Nguyen, L. T., Hwang, J., Lee, E. Y., Giong, H. K., … & Kim, H. K. (2019). A threonyl-tRNA synthetase-mediated translation initiation machinery. Nature Communications, 10(1), 1357.[Link]

Maidorn, M., Olichon, A., Rizzoli, S. O., & Opazo, F. (2019). Nanobodies reveal an extra-synaptic population of SNAP-25 and Syntaxin 1A in hippocampal neurons. In MAbs (Vol. 11, No. 2, pp. 305-321). Taylor & Francis. [Link]

• RNA co-immunoprecipitation

Chen Z, Mashburn-Warren L, Merritt J, Federle MJ, Kreth J. (2017) Interference of a speB 5′ untranslated region partial deletion with mRNA degradation in Streptococcus pyogenes. Mol Oral Microbiol. 32(5): 390-403. [Link]

Choose the right resin according to your application:

When to use which resin?

Application	Strep-Tactin®		Strep-Tactin®XT
	Strep-tag®	Twin-Strep- tag®	Strep-tag®	Twin-Strep- tag®
purification
batch
gravity flow
Äkta purification
denaturing conditions
low-abundant proteins
membrane proteins
detection
assay

 

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The Streptavidin:Biotin binding is the strongest non-covalent biological interaction known. With IBA’s newly developed Strep-Tactin®XT in combination with Twin-Strep-tag®, this near covalent binding affinity can be used for e.g. protein purification, protein interaction analysis or assays (e.g. BIAcore). Since Biotin is still binding strongly to Strep-Tactin®XT it can be used for elution of Twin-Strep-tag® fusion proteins.

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• Elution from Strep-Tactin®XT needs to be performed with biotin
• Regeneration of Strep-Tactin®XT resin will be achieved with 3 M MgCl2 or fresh NaOH

Technical comparison of Strep-Tactin® and Strep-Tactin®XT

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Strep-Tactin®XT allows higher protein yields
Strep-Tactin®XT allows the purification of higher protein yields compared to Strep-Tactin®. This was determined by purification of different target protein on either Strep-Tactin® or Strep-Tactin®XT. The obtained protein yields were determined and compared in the graph below. Here, we found that Strep-Tactin®XT allows in average the purification of a 2-fold higher protein yield compared to Strep-Tactin®.

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Strep-Tactin®XT allows intensive washing without loss in yield
An advantage of the new Strep-tag® system III is that it allows intensive washing without the loss in protein yield. This figure shows the purification of mCherry-Twin-Strep-tag® fusion protein via 1 ml Strep-Tactin® Superflow® resin and 1 ml Strep-Tactin®XT Superflow® resin. E. coli supernatants were prepared and applied onto the column. Then the columns were washed with 8 CV Buffer W in order to reach a constant absorption at A260/A280 nm. Then the target protein was eluted with 50 mM biotin. Samples of the last wash fraction and the elution fraction were analysed on SDS-PAGE showing that some of the target protein was washed down from Strep-Tactin® Superflow® resin, whereas no protein was eluted from Strep-Tactin®XT Superflow® resin.
The elution fractions were further analysed in Western Blot, showing that the remaining bands are degradation products of mCherry.

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Efficient immobilization of Strep-tag® fusion proteins via Strep-Tactin®XT
The following assay shows the comparison of the immobilization efficiency of bacterial alkaline phosphatase (BAP-Strep-tag®II) on Strep-Tactin®XT and Strep-Tactin®. Here, different amounts of BAP were subjected to the coated microplates. After washing, the relative maximum amount of immobilized BAP was determined. The relative signal intensity reflects the amount of bound BAP.

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Two different resins
Strep-Tactin® and Strep-Tactin®XT are engineered Streptavidin variants exhibiting different binding affinities towards Strep-tag® and Twin-Strep-tag®.

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Two different affinity tags
The Strep-tag® system is based on one of the strongest non-covalent interactions in nature, which is the interaction of biotin to streptavidin. It allows the purification, detection and immobilization of highly pure and bioactive recombinant proteins. The system includes two affinity tags: Strep-tag®II is a synthetic peptide consisting of eight amino acids and Twin-Strep-tag® consists of two Strep-tag®II sequences in series combined by a GS-linker. This peptide sequences exhibit intrinsic affinity towards Strep-Tactin® and Strep-Tactin®XT, two specifically engineered streptavidin variants.

• High NaOH stability (CIP 0.5 M NaOH 100 Cycles)
• ≥70 mg/ml dynamic binding capacity (DBC 10%)
• Cost effective products

Dynamic binding capacity (DBC 10%) of IBA Protein A determined with a  monoclonal antibody.

DBC of Protein A remains stable after treatment with 0.5 M NaOH over~100 cycles. 1 cycle = 15 min.

Data

*Dynamic binding capacity (DBC 10%) was determined with 1 mg/ml monoclonal hu IgG1 using a 1 mL column at 1, 2.4 and 6 minutes residence time.

Protein A does not bind to all IgG’s equivalently and binding varies among species. Even within a species, Protein A interacts with some subclasses of IgG and not others.

Selector resins are based on high-affinity single-domain antibodies (sdAb) which are covalently immobilized on 4% cross-linked agarose beads. The oriented and selective attachment via a flexible linker guarantees a high accessibility of the sdAbs and largely eliminates batch-to-batch variations. Due to the single-chain nature of sdAbs and their covalent attachment, no “leakage” of light and heavy chains from IgGs is observed during elution with SDS sample buffer.

Choose from our Selector Portfolio:

RFP Selector features high affinity and superior capacity for immunoprecipitation experiments of RFP fusion proteins while showing negligible non-specific background. RFP Selector immobilizes a wide range of RFP derivatives including mCherry. For details see our product specifications below.
RFP Selector is compatible with physiological buffers and with high stringency buffers. RFP Selector provides great freedom to adjust the binding and washing conditions to the experimental needs.

RFP Selector Specifications
Specificity: Recognizes most common red fluorescent proteins like mRFP, mCherry, dsRed, tdTomato and mScarlet. Does not cross-react with GFP or mTagBFP/mTagRFP derivatives. For more detailed information see data sheet (click on product).
Support: 4% cross-linked agarose beads
Capacity: > 4 µg RFP per µl of packed beads (= 2µl of slurry)
Formulation: 50% slurry in 20% ethanol / PBS
Recommended for: Immunoprecipitation, Mass Spectrometry

A, Pull-down of mCherry from a mixture of GFP, mCherry and mTagBFP
B, Immunoprecipitation of mCherry (•) from HeLa lysate
In/Ft: 1/1000 of input and non-bound material
E: Eluate from 1 µl of beads
* Specific maturation band from RFP family members
(see e.g. Gross et al. PNAS (2000) 11990-11995)
C, Control experiment using functionalized beads lacking sdAbs

MBP Selector features high affinity and superior capacity for immunoprecipitation experiments of MBP fusion proteins while showing negligible non-specific background.
MBP Selector is compatible with physiological buffers and high stringency buffers. MBP Selector provides great freedom to adjust the binding and washing conditions to the experimental needs.

MBP Selector Specifications
Specificity: Recognizes E.coli maltose-binding protein (MBP)
Support: 4% cross-linked agarose beads
Capacity: > 2.5 µg MBP per µl of packed beads (i.e. 2 µl of slurry)
Formulation: 50% slurry in 20% ethanol / PBS
Recommended for: Immunoprecipitation, Mass Spectrometry

Immunoprecipitation of MBP (•) from HeLa lysate.
In/Ft: 1/1000 of input and non-bound material.
E: Eluate from 1 µl of beads
Right panel: Control experiment using functionalized beads lacking sdAbs.

GFP Selector features high affinity and superior capacity for immunoprecipitation experiments of GFP fusion proteins while showing negligible non-specific background. GFP Selector immobilizes a wide range of GFP derivatives. For details see our Product Specificity Chart below.

GFP Selector is compatible with physiological buffers and with high stringency buffers (see Product Data Sheet). GFP Selector provides great freedom to adjust the binding and washing conditions to the experimental needs.

GFP Selector Specifications
Specificity: Recognizes GFP, mEGFP, superfolder GFP, Emerald GFP and most common CFP and YFP variants. It does not cross-react with mCherry, mRFP, dsRed, mTagBFP or their most common derivatives. For more detailed information see data sheet (click on product).
Capacity: > 4 µg GFP per µl of packed beads (i.e. 2 µl of slurry)
Support: 4% cross-linked agarose beads
Formulation: 50% slurry in 20% ethanol / PBS
Recommended for: Immunoprecipitation, Mass Spectrometry

A, Pull-down of GFP from a mixture of GFP, mCherry and mTagBFP
B, Immunoprecipitation of GFP (•) from HeLa lysate.
In/Ft: 1/1000 of input and non-bound material.
E: Eluate from 1 µl of beads
* Specific maturation band from GFP family members
C, Control experiment using functionalized beads lacking sdAbs.

TagFP Selector features high affinity and superior capacity for immunoprecipitation experiments of TagFP fusion proteins while showing negligible non-specific background.
TagFP Selector is compatible with physiological buffers and high stringency buffers. TagFP Selector provides great freedom to adjust the binding and washing conditions to the experimental needs.

TagFP Selector Specifications
Specificity: Recognizes mTagBFP, mTagRFP, mTagRFP657 and mKate. Reactivity against other TagRFP derivatives not analyzed. Does not cross-react with common GFP- or dsRed/RFP derivatives including EBFP. For more detailed information see data sheet (click on product).
Support: 4% cross-linked agarose beads
Capacity: > 4 µg BFP per µl of packed beads (= 2µl of slurry)
Formulation: 50% slurry in 20% ethanol / PBS
Recommended for: Immunoprecipitation, Mass Spectrometry

A, Pull-down of mTagBFP from a mixture of GFP, mCherry and mTagBFP
B, Immunoprecipitation of mTagBFP (•) from HeLa lysate.
In/Ft: 1/1000 of input and non-bound material.
E: Eluate from 1 µl of beads
* Specific maturation band from BFP family members
C, Control experiment using functionalized beads lacking sdAbs.

GST Selector features high affinity and superior capacity for immunoprecipitation experiments of GST fusion proteins while showing negligible non-specific background.
GST Selector is compatible with physiological buffers and high stringency buffers. GST Selector provides great freedom to adjust the binding and washing conditions to the experimental needs.

GST Selector Specifications
Specificity: Recognizes Schistosoma japonicum Glutathione S-transferase (GST)
Support: 4% cross-linked agarose beads
Capacity: > 4 µg GST per µl of packed beads (i.e. 2 µl of slurry)
Formulation: 50% slurry in 20% ethanol / PBS
Recommended for: Immunoprecipitation, Mass Spectrometry

Immunoprecipitation of GST (•) from HeLa lysate.
In/Ft: 1/1000 of input and non-bound material.
E: Eluate from 1 µl of beads
Right panel: Control experiment using functionalized beads lacking sdAbs

Specifications
Selector Control
Selector Control is based on the identical 4% cross-linked agarose beads as our other Selector resin products. The beads are functionalized using the very same chemistry, but are lacking the sdAb. They are the perfect control for your pull-down experiments.
Support: 4% cross-linked agarose beads
Formulation: 50% slurry in 20% ethanol / PBS
Recommended for: Immunoprecipitation, Mass Spectrometry

MiniSpin columns
The MiniSpin columns are the ideal solution to treat small volumes. They do fit in every mini-centrifuge are compatible with all standard 1.5 mL or 2.0 mL tubes.

Two different detection systems are provided:

1. detection via Strep-Tactin® conjugates (for Strep-/Twin-Strep-tag® proteins)
2. detection via monoclonal antibodies against Strep-/Twin-Strep-tag®

Read which detection system is suitable for your applications:

Western blot
For direct detection of Strep-tag® fusion proteins in Western blots use:

• via chromogenic and/or chemiluminescence reaction (no secondary antibody needed!) use
  – Strep-Tactin® HRP conjugate (HRP, horseradish peroxidase)
  – StrepMAB-Classic HRP conjugate
• via chromogenic reaction
  – Strep-Tactin® AP conjugate (AP, alkaline phosphatase)

ELISA
For protein detection in ELISA use

• StrepMAB-Classic, unconjugated
• Strep-Tactin® HRP conjugate

Immunocytochemistry/Immunohistochemistry
Visualize your Strep-tag® protein Strep-Tactin®XT, StrepMAB-Classic, or StrepMAB-Immo fluorescent conjugates. They are available with:

FACS
For staining (Twin-) Strep-tagged proteins in FACS we recommend to use our Strep-Tactin® or Strep-Tactin®XT conjugates:

• Strep-Tactin® PE
• Strep-Tactin® APC
• Strep-Tactin®XT DY-488 conjugate
• Strep-Tactin®XT DY-549 conjugate
• Strep-Tactin®XT DY-649 conjugate

Applications

Benefits of Strep-tag® based immobilization

• Oriented immobilization of recombinant proteins with N-terminal, C-terminal or internal Strep-tag®II/Twin-Strep-tag®
• Effective screening procedures
• Minimal non-specific binding
• High and constant activity
• Minimal coefficients of variation (cv)

Immobilization tools provided by IBA

• Strep-Tactin®XT
• Strep-Tactin®
• StrepMAB-Immo Antibody
• Streptavidin

Twin-Strep-tag Capture Kit (SPR)

The Twin-Strep-tag Capture Kit enables the highly stable immobilization of the ligand based on IBA´s unique Strep-Tactin®XT:Twin-Strep-tag® system, due to the pM affinity of Twin-Strep-tag® to Strep-Tactin®XT. In the Twin-Strep-tag® Capture Kit you get all necessary reagents and a protocol for the generation of Strep-Tactin®XT (capture molecule) coated sensor chips to immobilize Twin-Strep-tag® fusion proteins (ligand) efficiently.

Key benefits of Strep-Tactin®XT and Twin-Strep-tag® for SPR experiments

• High affinity enables long term measurements (high affinity in low pM range; T1/2 = 13 h)
• Chip can be easily regenerated

Strep-Tactin®XT coated microplates

Strep-Tactin®XT: Xtra Tight (pM affinity) immobilization of Twin-Strep-tag® fusion proteins
Ready-to-use microplates (12 x 8-well strips) for diagnostic/assay applications, coated with Strep-Tactin®XT, a further developed Strep-Tactin® variant with higher affinity for Strep-tag®II fusion proteins (binding affinity in nM range) and especially Twin-Strep-tag® fusion proteins (binding affinity in pM range). They are selectively captured from complex mixtures and the biomolecules of interest are presented to interaction partners in a uniform manner which results in reliable and reproducible assays. The solid-phase, multi-well format for convenient assays and high throughput screenings is compatible with standard multichannel pipettes and automated plate washers and plate readers.
Note that the bound fusion protein can still be eluted from the microplate.

Strep-Tactin® coated microplates

Ready-to-use Strep-Tactin® coated 8-well strips provide the power of our Strep-tag® system in a solid-phase, multi-well format for convenient assays and high throughput screenings of biomolecules tagged with Strep-tag®II. The strips are supplied framed in sets of 12, resulting in a 96-well configuration compatible with standard multichannel pipettes and automated plate washers and plate readers. The biomolecules are presented to interacting partners in a uniform manner, which results in reliable and reproducible assay formats.

StrepMAB-Immo (Ab) 
High-affinity Strep-tag®II/Twin-Strep-tag® specific monoclonal antibody for capturing Strep-tag® fusion proteins on solid phases
• optimal for capturing Strep-tag® fusion proteins on solid phases (e.g. Biacore chips1)
• high affinity both with C- and N-terminal Strep-tag® fusion, provided the Strep-tag® is N-terminally extended by a SerAla-linker

StrepMAB-Immo is a murine, high-affinity Strep-tag®II specific monoclonal antibody which is especially suited for stable, mild and oriented capturing of Strep-tag®II fusion proteins on solid phases. To realize this, the antibody can be immobilized on e.g. microplates, Biacore CM5 sensor chips or other biochips. The nearly irreversible binding is achieved both for fusion proteins carrying a C- or N- terminal Strep-tag®. The Strep-tag® must be N-terminally extended by a SerAla linker (recombinant protein – SA-WSHPQFEK or SA-WSHPQFEK – recombinant protein).

Streptavidin
One of the most widely employed immobilization partners is avidin (66–69 kDa tetrameric glycoprotein) and biotin (water-soluble vitamin B). Avidin (Streptavidin) binds to biotin via an exceptionally strong non-covalent interaction. The binding interaction is rapid and nearly insensitive to pH, temperature, proteolysis, and denaturing agents. Biotin is a small molecule and conjugation to proteins does not significantly affect protein functionality or conformation.
Natural avidin or engineered avidin (e.g., streptavidin, neutravidin, and nitrividin) can be physisorbed or covalently linked to a surface for subsequent immobilization of biotinylated proteins.

Immobilization with Strep-Tactin®XT:Twin-Strep-tag®

Due to the extra tight binding affinity of Strep-Tactin®XT to Twin-Strep-tag®, the system is highly suitable for efficient immobilization of Twin-Strep-tag® (and Strep-tag®II) fusion proteins.
The binding affinity is in the range of antibody based immobilization systems, but more economic and straight-forward to use.

Key benefits of Strep-Tactin®XT and Twin-Strep-tag® for immobilization experiments

• High affinity in pM range (T1/2 = 13 h)
• Reversibility due to addition of Biotin
• Minimal non-specific binding

Protein Immobilization Applications for the Strep-tag® assay system

• Antibody or serum screening
• Diagnostic assays
• Expression cloning
• Protein interaction studies
• Screening of engineered enzymes
• Drug screening

Strep-Tactin® assay system

Strep-Tactin® coated microplates

allow the selective capture of Strep-tag®II or Twin-Strep-tag® fusion proteins from complex mixtures of molecules. The biomolecules are presented to interaction partners in a uniform manner which results in reliable and reproducible assay formats.

StrepMAB-Immo Immobilization Products

StrepMAB-Immo (ab) – Product Specifications

**pASK-/pEXPR-vectors with N-term Twin-/Strep-tag®II do NOT have “SerAla”-Linker but the
StarGate® vectors (carrying Strep-tag®II and Twin-Strep-tag®) are equipped with the SA-Linker.

Streptavidin – Immobilization of biotin or biotinylated proteins
Streptavidin, lyophilized
The streptavidin:biotin system is widely used for immobilization and detection of biotinylated molecules, like proteins and nucleic acids. IBA provides bulk amounts of lyophilized streptavidin with competitive prices in reliable high quality to generate
•    streptavidin coated surfaces (microplates, SPR-chips or beads)
•    detection reagents conjugated with e.g. fluorescent dyes

Streptavidin Specifications

Streptavidin is a tetrameric protein composed of identic subunits. Each subunit binds one biotin molecule with a KD of ~1×10-15 M. The preparation contains an N- and C-terminal shortened variant (core streptavidin) with improved properties concerning homogeneity, solubility, resistance towards proteolytic degradation and accessibility of the biotin binding pocket, as compared to native streptavidin.