Q: Does R&D Systems have reagents for dispensing?

A: There are no dispensing reagents. R&D Systems does not distribute or authorize any company to distribute. At present, the so-called "RD Packing Reagent" on the market is 3 products without quality assurance, and R&D Systems does not undertake any after-sales service of "RD Packing Reagent". Here, it is recommended that customers and distributors order from the regular distributors published on the R&D Systems Chinese website.

antibody

Q: The names of antibodies in the catalogue are AB, AF, BAF, and MAB . What is the difference between them?

A: The antibody with AB is purified with G protein and has IgG component; the antibody with AF is purified by G protein and purified by antigen affinity chromatography. Therefore, the AF antibody is an antigen-specific IgG, and the AB antibody contains an IgG that is not specific to the analyte of interest. BAF is a biotinylated AF antibody; MAB is a monoclonal antibody.

Q: What is the molecular weight of IgG ?

A: The molecular weight of IgG is 150kDa. It consists of two 50kDa heavy chains and two 25kDa light chains.

Q: What is the epitope recognized by a monoclonal antibody?

A: R&D Systems does not locate antigenic epitopes. Antibodies are directed against the entire immunogen (listed in the data sheet).

Q: What is the epitope recognized by a polyclonal antibody?

A: Polyclonal antibodies have multiple epitope recognition sites. Antibodies are directed against the entire immunogen (listed in the data sheet).

Q: What is Thehalose ? Why is it on this antibody?

A: Thehalose is a non-reducing sugar (molecular weight 342.1) that does not interact with amino acids and proteins in the Maillard reaction. It is found in many plants and animals. It has been reported that Thehalose is the most effective antifreeze for stabilizing proteins against freezing, which increases the protein's ability to withstand moisture and makes it less prone to deposits when reconstituted.

Q: What is the reason for using Trehalose to stabilize the protein?

A: Trehalose is mainly used to protect proteins during freezing and dehydration. It is a non-reducing sugar that is amorphous when dry powdered.

Apoptosis

Q: Why are there two different sets of TUNEL kits?

A: Because there are two different TUNEL methods to detect apoptosis. The first method uses a TdT enzyme (terminal deoxynucleotidyl transferase) to add biotinylated nucleotides to the 3'-hydroxyl end of the DNA fragment in the tissue. The addition of a positive ion makes this label more efficient, and the biotinylated nucleotide can be detected using a streptavidin-HRP conjugate and a substrate.

The second method still uses the TdT enzyme (terminal deoxynucleotidyl transferase) to add nucleotides to the 3'-hydroxyl end of the DNA fragment in the sample, but with 5-bromodeoxyuridine (BrdU) label instead of organism The protein was further detected by biotinylated anti-5-bromodeoxyuridine (BrdU) antibody. The apoptosis detection kit using this method includes: TA100 TACS-XL basic in situ apoptosis kit; TA200 TACS-XL DAB in situ apoptosis kit; TA300 TACS-XL blue labeled in situ cell wither Death kit; TA400 TACS-XL supplementation apoptosis kit;

Q: How is the Caspase activity test used?

A: The Caspase activity test provides a simple and convenient means of detecting protease activity in cell lysates. When the polypeptide substrate of the specific Caspase is cleaved, the released indicator molecule can be quantitatively determined by a general reading instrument or a fluorescence plate reader. Comparing the signal obtained from the apoptotic sample with the uninduced control sample, the fold increase in Caspase activity can be determined, and the Caspase activity is directly proportional to the detected signal.

Q: Is the Caspase activity test available for quantitative testing?

A: R&D Systems' Caspase Activity Assay Kit is available as a semi-quantitative test. The test results are preferably used to measure the increase in the fold fold of Caspase activity in apoptotic cells and in uninduced cells. In the experiment, it is best to use a background control (no cell lysate or substrate-free reaction). If the background control also has a certain reading, this reading should be subtracted from the test data before the calculation factor is increased.

Q: What is the difference between Caspase activity assay and Caspase ELISA kit?

A: Caspase activity assay was used to determine the activity of proteases of different Caspase, expressed as a fold increase over uninduced samples. The Caspase ELISA kit is used to determine the content of different caspase in the sample and is expressed quantitatively in pg / mL.

Q: Is the caspase X activity test specific to caspase X ?

A: Most caspase cleaves all substrates. They prefer a substrate rather than another substrate based on Michaelis-Menton kinetics, but none of the substrates are specific to a certain Caspase. For example, both Caspase 3 and Caspase 7 can cleave DEVD substrates; Caspase 9, 4, and 5 can cleave LEHD. R&D Systems chose the substrate for each Caspase. If the reaction takes too long, some Caspase will activate other Caspase.

Q: Is the cell lysate in the Caspase Activity Assay Kit the same as in the other kits?

A: All cell lysates in the Caspase Activity Assay Kit are the same. Therefore, it can be used to lyse cells and to test a variety of Caspase activities.

Q: Is R&D Systems ' Caspase inhibitor reversible?

A: All R&D Systems Caspase inhibitors have a benzomethoxy-based (Z-) and FMK functional group at the N-terminus, which can perforate cells and are irreversible.

Q: Does R&D Systems provide a positive control for Caspase activity testing?

A: R&D Systems offers a variety of recombinant Caspase enzymes, which are ideal positive controls. If the tester wants to establish a positive control, many methods have been published for positive controls that can produce apoptosis. If cells are incubated with 2 mM staurosporin for 2 hours, most cell types can be induced to enter apoptosis. R&D Systems has literature listings on how to generate positive controls for Caspase, which can be obtained from our technical services.

ELISA

Enzyme-linked immunosorbent assay

Q: Is there a relevant control for the human Quantikine ELISA kit?

A: R&D Systems offers a triple control for the human Quantikine ELISA kit. Please contact us to determine the catalog number of the product.

Q: I want to use the recombinant protein in your catalog as a control for my ELISA , but I found that there are differences in quality. Why is that?

A: The first thing to consider is that the quality of the recombinant protein will be several times higher than the testable range of the kit. The recombinant protein must be diluted several times to obtain the test range of the kit. Generally, it is diluted from mg/ml to pg/ml, and in this intermediate light, the error of the pipette reaches a measurable level.

The second consideration is that the protein levels measured by R&D Systems' immunoassay are measured with an antibody and measured with a second antibody that was calibrated with the standard protein at the time of kit development. These measured early standard proteins became the basic calibrators, and subsequent standards were corrected for it. Such immunoassay kits of different production batch numbers will be identical. The method for measuring the amount of protein in these basic calibrators may differ from the method for determining the amount of protein in your reagent tube.

Q: What is a competitive ELISA?

A: The competition ELISA is based on a competitive binding technique in which the molecule to be tested in the sample is simultaneously labeled with a fixed amount of the same molecule (we generally use alkaline phosphatase as a marker) simultaneously with the same binding site of the antibody immobilized on the well plate. Competition, with reference to the standard curve, the test data values ​​are quantitative.

Q: What is a sandwich ELISA ?

A: The sandwich ELISA uses an antibody specific for the analyte in the sample as the immobilized capture antibody, and then the second labeled antibody is used for detection. The detection antibody is also specific to the analyte. When referring to the standard curve, the test data values ​​are quantitative.

Q: What is a direct ELISA ?

A: Direct ELISA is to directly coat the analyte to the surface of the microplate, and then use the test antibody to confirm the presence of the analyte. The test data values ​​are semi-quantitative when referenced to recombinant protein (standard curve).

Q: How many samples can I make for the R&D Systems Parameter brand ELISA kit?

A: The R&D Systems Parameter brand ELISA kit can be used to make a standard curve of 6 points, a control and 41 samples (two copies for each sample).

Q: How many samples can R&D Systems ' Quantikine brand ELISA kits do?

A: Most of R&D Systems' Quantikine brand ELISA kits can be used for standard curves, controls, and 40 samples (two copies per sample).

Q: How many samples can I make for the Quantikine brand of mouse, rat and pig ELISA kits from R&D Systems ?

A: Each microplate in a Quantikine brand mouse or rat ELISA kit can be used as a standard curve, control, and 39 samples (each sample is doubled). Some Quantikine brand mouse or rat ELISA kits have two microplates and some have only one microplate.

Q: What ELISA microplates does R&D Systems recommend for DuoSets and antibody pairing experiments?

A: At the R&D Systems headquarters, we use Costar's microplate (catalog #2592). Costar's phone number is (800) 492-1110.

Q: What purity of BSA does R&D Systems use for ELISA ?

A: For ELISA, we used BSA of Serological Proteins (catalog #82-045). The phone for Serological Proteins is (815) 937-8270.

Q: What is included in the Quantikine ELISA kit?

A: R&D Systems' Quantikine ELISA kit is a complete kit. It contains a plated microplate, enzyme-labeled antibody, standard protein, diluent, substrate, terminator, lotion and microplate sealing membrane. All kits are fully validated for the samples listed in the protocol instructions to ensure high quality.

Q: What is DuoSet ?

A: The DuoSet ELISA development system provides enough capture antibodies, test antibodies, standard proteins and Streptavidin-HRP to perform experiments on approximately fifteen 96-well microplates. We also provide a sample test procedure and reagents for this system. The DuoSet ELISA development system is designed primarily for high-throughput screening of cell culture supernatants, but experimenters familiar with ELISA development have successfully extended their use to serum and plasma samples.

Q: What is the antibody pairing of R&D Systems ?

A: R&D Systems' antibody pairing is a do-it-yourself product. R&D Systems recommends that users of this product be well versed in the development of immunoassays. The user must rely on experience to determine the optimal concentration of capture and test antibodies. R&D Systems' recombinant cytokines are not calibrated by ELISA, so mass calibration must be performed by ELISA before use. More information on ELISA development can be found in our ELISA Development Guide (website: http://).

Q: What is the difference between Quantikine and QuantiGlo ELISA kits?

A: R&D Systems' Quantikine brand ELISA kit is a colorimetric assay that requires a standard reader to be equipped with suitable filters for reading and optical wavelength correction. The QuantiGlo ELISA kit uses a fluorogenic substrate that counts in lumens or relative light units (RLU). Therefore, the QuantiGlo ELISA kit requires a fluorescence reader. This fluorescent reading instrument needs to be set at: 1.0 minute lag time; 1.0 sec/hole reading time; cumulative state; automatic acquisition on. R&D Systems uses Dynex Technologies' Fluorescence Readers.

Q: What is the difference between a normal Quantikine ELISA kit and a highly sensitive Quantikine ELISA kit?

A: The highly sensitive Quantikine ELISA kit is typically used for the detection of very low levels of cytokines, such as serum and plasma in normal subjects (in healthy conditions). Highly sensitive Quantikine can be selected when the normal Quantikine kit generally does not detect (or almost does not detect) cytokines in normal human serum and plasma. We recommend that the experimenter first consult the literature to determine the test range of the test to select the type of kit required.

Q: Is R&D Systems ' Quantikine kit available for tissue homogenate (or other untested) samples?

A: Unfortunately, R&D Systems has not used tissue homogenate as a sample to validate the Quantikine range of kits. If you want to decide whether the kit can be used for untested samples, the experimenter should first do a "pre-test for incorporation and recovery." To put it simply, the experimenter divides the sample into two parts: one is mixed with a certain amount of reagent standard, then one dilution series (generally diluted to 1:16), and the incorporated one is not incorporated. Compared to one. The recovery rate (%) was calculated using the following formula: test value (pg / ml) / expected value (pg / ml) x 100% = % recovery. In general, a recovery of 80-120% is considered acceptable. However, the acceptable range should be determined by each laboratory. This method can be used to characterize any sample that has not been certified by R&D Systems. We also have more detailed experimental procedures for “incorporation and recycling” that can be obtained from our Technical Services Department. We can also look up the literature to see if other testers have used our products to make different samples or different genera.

Q: Will adding the diluent further dilute the sample?

A: Because the diluent is added to all wells, both the standard and the sample being tested are diluted equally, so the sample concentration can be read from the standard curve without dilution adjustment.

Q: Can I extend both ends of the standard curve?

A: Under no circumstances do we support experimental results beyond the scope of the determination. In the range of tests we have determined, we guarantee the repeatability of the experimental results.

Q: Why not extend the test range to the stated sensitivity?

A: Sensitivity is the lowest measurable value in the statistics that is greater than zero. It is calculated from the variability of the background signal and the test. Sensitivity is the conversion of the median of 20 zero replicates plus two standard deviations from the standard curve to the concentration of the analyte. The minimum standard is the lowest point we can rest assured that can still be linearly related to the standard curve and is therefore quantifiable.

Q: Are the reagents in the Quantikine kit interchangeable?

A: If the diluents in the kits (RD1-, RD5-, RD6-) have the same component number and lot number, they are interchangeable. R&D Systems does "quality control of the entire kit", which means that we do not support alternatives between batches. In any case, the microplate and conjugate are not interchangeable.

Q: Are the lotions in the Quantikine kit interchangeable?

A: If the component numbers are the same, the lotion is interchangeable between the same type of kit (between the normal kits or between the high sensitivity kits). However, the wash solution in the normal Quantikine kit cannot be used in high-sensitivity kits. The wash solution in the normal Quantikine kit contains phosphoric acid, which interferes with the amplification of NADPH-driven signals in the highly sensitive Quantikine kit.

Q: Why do I have to use polypropylene (polypropylene) tube as the standard dilution in some experiments?

A: Some cell molecules stick to glass or polystyrene, but not sticky polypropylene.

Q: I don't have enough RD5 calibrators in the Quantkine kit to dilute my cell supernatant. What should I do?

A: You can use the cell culture medium for the initial dilution. The final 1:10 dilution of the direct pipetting to the microplate can be diluted with the calibrator.

Q: The RD1 test thinner in my Quantikine kit looks like a precipitate. Can it be used?

A: Some RD1 test diluents do have different levels of sediment. In this case, we have made a record in the experimental step manual.

Q: Why is the standard curve using a 4-pl fit?

A: R&D Systems uses a 4-phase parameter curve fit (also known as 4-pl or sigmoidal curve fit) when developing and controlling most of our Quantikine ELISA kits. In general, it has a better curve fit than log-log and line. If data analysis is not available 4-pl, log-log is the next best option.

Q: In the test step , I said that I would use 500 rpm and my shaker could not reach it. Is this speed correct?

A: The 500 rpm uses a 0.12 inch oscillating track. If your oscillator uses a larger oscillating track, the 500 rpm is indeed too fast. In this case, you should re-adjust the oscillating speed according to the recommendations of R&D Systems. You can take an extra 96-well microplate and add the lotion. The amount of the lotion is the same as the amount of solution in the well. After the plate is closed, adjust the speed of the shaker until the liquid rotates sharply on the upper part of the hole. Splash on the seal or create foam.

Q: I have a problem with a large coefficient of variation ( CV ). What is going on?

A: The biggest but not the only two reasons may be pipetting errors and cleaning methods. You can refer to our How to Successfully Operate ELISA Guidance at http://

Q: Why do Quantikine ELISA reagents need to be diluted?

A: There are two main reasons: First, the cytokine content is very high in most samples. If it is not diluted, the reading will be higher than the standard curve. Second, the most common reason is that we recommend dilution. The interference or matrix effect in the sample is diluted.

Q: Can I stop the Quantikine test, extend the incubation time, or increase the temperature of the incubation at any overnight step?

A: The R&D System does not recommend extending the incubation time for any Quantikine ELISA. Moreover, when the experimental procedure changed, we were unable to guarantee the results of the Quantikine ELISA. R&D System does "quality control of the entire kit", which means that we can't support the changed experimental steps because they are not quality controlled. Extending the incubation time, or increasing the incubation temperature to shorten the incubation time will increase the background of the experiment (aka blank or zero standard). As a result, low levels of cytokines in the sample and standard will not be detected because the increased background signal will be subtracted from the values ​​in all wells.

Q: I used the DuoSet ELISA development system, but almost no color is produced. Which steps may have gone wrong?

A: Many aspects will affect the color. such as:

1) Interference from BSA. It is important to choose an ELISA-grade BSA that does not contain fatty acids, which can reduce the interference of the globulin on the experiment. R&D Systems recommends the use of BSA for Serological Proteins (catalog #82-045).

2) Reagents that are not at room temperature will suppress the signal when used; if the room temperature is too low, the signal will be suppressed.

3) If a microplate that is not indicated as a "high binding ELISA" is used, the binding of the capture antibody to the microplate is not strong, resulting in a low color of the test.

4) This problem will occur with any reagents that are misconfigured, improperly stored, or have expired.

5) The wavelength used when reading the board does not match the wavelength of the low object.

Q: Can I use your antibodies in ELISA pairing, but with another company as the standard protein?

A: The problem with using one company's antibodies while using another company's standards is that they have different immunological activities (or different antibodies binding to recombinant proteins). This phenomenon occurs because the recombinant protein as a standard differs from the recombinant protein as an antibody immunogen in protein sequence or folding. If the protein sequence or folding occurs at the antibody binding site, it will cause antibody recombination. Protein standards are not recognized or poorly identified.

ELISpot

Enzyme-linked immunospot

Q: What is ELISpot ?

A: R&D Systems' ELISpot test uses ELISA technology. The monoclonal antibody specific for a certain cytokine is first immobilized on the PVDF membrane of the microplate, and the cells induced by the appropriate stimulation are pipetted into the microwell, and then the whole microplate is placed in the moisturizing 370CCO _{2 .} Incubate in the incubator for a specific period of time; during the incubation period, the immobilized antibodies bind to the cell molecules secreted by the surrounding secretory cells; wash away the cells and unbound molecules, and add specificity to the cytokine Biotinylated polyclonal antibody; remove unbound biotinylated antibody, add streptavidin-conjugated alkaline phosphatase; wash unbound enzyme from the reaction, then add substrate solution (BCIP/NBT) A blue-black precipitate (spot) is formed at the location of cytokine production, and each spot represents a cell that secretes a specific cytokine. These spots can be read by an automatic plate reading system (unlike a normal reading instrument); alternatively, these spots can be read manually by a stereo microscope.

Q: What is the difference between ELISpot and ELISA ?

A: The ELISA test measures the total amount of a certain cytokine in the sample (generally expressed as pg or ng /mL); the ELISpot experiment does not determine the amount of a certain cytokine in the sample, but determines how many cells are secreting a certain a cytokine.

Q: What is the difference between ELISpot and components?

A: R&D Systems' ELISpot kit contains: a monoclonal antibody specific for a cytokine (this antibody has been pre-immobilized on a PVDF membrane in a microplate), a biotinylated detection antibody, and a Streptavidin conjugate. Alkaline phosphatase, BCIP/NBT chromophore, and recombinant cytokine positive control. The kit is stocked with all the supplies needed for the test and the tester does not need to be optimized.

R&D Systems' ELISpot development reagents are divided into two essential components, and development kits specific to cytokines and ELISpot blue components must be purchased separately. The cytokine-specific development kit includes cytokine-specific capture and detection antibodies; the ELISpot blue component (catalog #SE002) is applicable to all R&D Systems cytokine-specific development kits, which include Streptavidin-alkaline Phosphatase and BCIP/NBT chromophores.

Q: Can I use only some of the microplates in the ELISpot kit?

A: Because the microplate with PVDF membrane is very sensitive, we can't make the microplate into a strip form. If the incubation is repeated many times, we will not be able to guarantee the experimental results obtained using the microplate; since the microplate is no longer sterile, the unused micropores may be contaminated. We are not worried about contamination during the first use, as most cell culture fluids contain antibiotics and the incubation time is relatively short. We chose PVDF microplates because they provide better experimental results than standard ELISA grade polystyrene microplates.

Q: How many cells do I need?

A: This question is more difficult to answer and varies according to the experimental requirements. How many cells are used have many variables: such as the size of the cells, the type of cells, the number of cells that secrete cytokines, the method of inducing cells, and the like. In the beginning, some cell dilutions (eg, dilution of 10,000,000 cells per well to 100,000 or even 10,000 cells) are needed to determine the optimal number of cells that can form distinct spots. For example, if the cells in the microwells have reached a monolayer fusion and most of the cells secrete the cytokines to be tested, the formed spots are difficult to separate, thus making it difficult to quantitatively detect the number of cells secreting the measured cytokines; In this case, a series of titrations should be done to reduce the number of cells. If only a few cells in the same monolayer fused cell secrete the cytokine to be tested, the resulting spots will be obvious and can be easily quantified; in this case, the number of cells is appropriate. Therefore, the optimal number of cells to be added to each well must be determined for different cell types and induction methods.

Q: How many samples can I make on a microplate?

A: This is based on a 96-well microplate test. With the exception of the positive control, the negative control, the background (blank), and the test antibody control, there are 88 wells left, and 44 samples can be made (each sample is doubled).

General FAQ

Q: What are the deadlines for proteins and antibodies?

A: R&D Systems has a policy of not providing production dates or product deadlines for our protein and antibody products, thereby limiting the life of the product. Proteins and antibodies tend to be stable for many years under appropriate storage conditions. These storage conditions include storage of the protein as a dry powder, or freezing (-20 ° C or -80 ° C) storage of the protein at a protein concentration above 0.1 mg/ml and reducing the number of freeze/thaw cycles. Please refer to the instructions in each product insert. Our company's regular quality control ensures that each product is biologically active at the time of sale. After the experimenter received the product, we were unable to control the storage of the product. We are willing to replace the product term with a product warranty. Under normal laboratory conditions, we guarantee that all R&D Systems products will meet or exceed our published standards.

Q: Is the X product available for X use but not included in the fact sheet?

A: If a particular use is not included in our data sheet, there is no more data within R&D Systems. Our technical services can be found in our literature library to see if other experimenters have published such uses, sample types, and/or species for this product.

Q: What does the product listed on your website have /CF ?

A: CF stands for no carry-on. In general, 50 mg of BSA (carrier protein) is added per 1 mg of cytokine to stabilize cytokines. The form without the carrier does not contain any BSA. In general, cytokines with BSA can be stored at lower concentrations and have longer shelf life than cytokines without carriers. If the cytokine is a standard for addition to cell/tissue culture or as an ELISA, a cell molecule with BSA can be used. When the cytokine is used for in situ application, labeling cytokines, or BSA can cause interference, a carrier-free cytokine should be used.

Q: rhEPO is listed in units. How to convert to quality ?

A: R&D Systems' recombinant human EPO (ultra-pure) catalog #286-EP-250, and our recombinant human EPO (tissue culture grade) catalog #287-TC-500, all have the same unit-to-quality conversion. One unit of rhEPO is approximately 10 ng.

Q: What level of BSA does R&D Systems use to reconstitute cytokine solutions?

A: R&D Systems uses the Serological Proteins fraction V BSA (catalog #81-068) to reconstitute the protein solution. The phone for Serological Proteins is (815) 937-8270.

Q: Why do some R&D Systems recombinant proteins have Fc fusion?

A: Fc can stabilize molecules. R&D Systems uses the Fc portion to have a tendency to become dimers, creating biologically active dimeric molecules. Taking the receptor/Fc chimera as an example, this fusion assists us in creating a receptor that produces higher affinity with its ligand than its soluble receptor. R&D Systems provided the same Fc portion as a control. The table of contents is: 110-HG, human recombinant IgG/Fc.

Q: Why do some of R&D Systems ' products need to be reconstituted with acidic solvents?

A: It is critical to use acidic solvents to reconstitute certain cytokines. Because some cytokines have very high isoelectric points, they are extremely hydrophobic. Without the use of this acidic re-dispensing agent, it is difficult for these cytokines to be completely dissolved in the solution. For the same reason, we also recommend using the same acidic reconstituting agent to store the aliquots of these cytokines. The pH of these reconstituted agents is usually between 4.5 and 5. These protein-packed samples that are already in solution can be further diluted to the working concentration with cell culture fluid (or other suitable buffer). In this way, a small amount of acid in the solvent can be buffered and safely used for living cells.

Q: Why do you want to reconstitute a cytokine with PBS/BSA if it is dry powdered from the same solution?

A: Additional BSA in the reconstituted agent can help with the recovery of cytokines and also increase stability. The volume of PSA used by R&D Systems in dry powdering solutions is minimal, so the PBS/BSA reconstituting agent does not give a 2X salt concentration. If it is not reconstituted as described in the data sheet, R&D Systems will not be able to guarantee the results of the product, as we are here to quality control our products.

Q: How do I convert kilodaltons ( kDa ) to grams per mole?

A: R&D Systems lists the molecular weight of our proteins on the data sheet in kilodaltons (kDa). The approximate conversion rate is: 1 Dalton = 1 g / mol (that is, a protein of 8 kD is equivalent to 8,000 g / mol).

Q: How do you convert your products into international units?

A: For cytokines, there is no uniform standard unit in the industry. To avoid confusion, R&D Systems consciously uses our protein in quality. A generally accepted definition is that a unit is equivalent to the ED50 value of an experiment. Obviously, the ED ₅₀ values ​​will vary under different conditions. If you follow the unit of a certain experimental result, or compare the products of different suppliers by unit, you must first determine how this unit of the product source is defined. When using a new batch of new products or new sources for the first time, R&D Systems strongly recommends that the experimenter first use the sample for a series of dilutions. It is recommended to use the midpoint of our ED50 range as the midpoint of the dilution, increasing and decreasing by 5, 10 , 20 or even 50 times. If the source of the tester or product is compared to the WHO standard unit by their "unit", we have a "WHO Conversion Table" in both the directory and the website (http:// .asp?bodyId=235), the experimenter can query to determine the settings of the experiment.

Q: In order to be biologically active, this protein requires me to use a cross-linked antibody - MAB050 . What kind of antibody is this? Do I have to do this?

A: This antibody is directed against 6x histone overhangs. We recommend using a protein with a cross-linking binder that contains a 6x histone tag. R&D Systems uses this antibody to cross-link binding to histone tags, allowing proteins with histone tags to be more biologically active. R & D Systems quality control test these antibody-binding protein cross-linked, to ensure consistent ED ₅₀ ED ₅₀ thereof in conjunction with the non-crosslinked protein. Therefore, without using such cross-linked antibodies, proteins among different batches will have a very significant difference in ED _50.