Frequently Asked Questions

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Please store plasma/serum samples frozen at -70°C and avoid freeze-thaw cycles. We also recommend adding a protease inhibitor (e.g aprotinin) to help protect peptides in sample from enzymatic cleavage.
For best results, samples should be assayed or used as soon as possible upon collection. For plasma/serum samples, we do not recommend storage for longer than 6-8 months, even if kept frozen.

Peptide Extraction:

Peptide extraction from sample is strongly recommended when using most of our assay kits. This is because primary antibodies for short peptides often cross-react with large proteins commonly found in biological samples (e.g. albumins, clotting factors). This can result in high background noise. Extracting your samples helps remove these large proteins, thereby reducing interference with the assay.
The following materials are necessary to perform plasma extraction. C-18 SEP-Columns (Catalog No. RK-SEPCOL-1) Buffer A (Catalog No. RK-BA-1) Buffer B (Catalog No. RK-BB-1) Each box of SEP-columns comes with 50 individual columns. These columns can hold 3 ml of volume and cannot be reused. One bottle of Buffer A and Buffer B is enough to perform 20 sample extractions.


Yes! All of our antibodies are raised in-house, here in California (USA). This gives us maximum control over the quality of our antibodies and helps us track any antibody back to its exact original source.
First, we syntheisze 5 - 10 mg of the peptide antigen. This is then conjugated to a KLH carrier protein. All of our antibodies are raised in rabbit hosts.
Antibodies are dried before shipping in order to maximize their stability. Please keep antibodies in this lyophilized form at -20°C for up to 24 months. For optimal results, use the antibody immediately after reconstitution. After rehydrating the antibodies (typically in distilled water), the antibody is stable for up to three (3) days at 4°C. For longer-term storage up to three (3) months, prepare small aliquots of the reconstituted antibody and freeze at -20°C or -80°C. Repeated freeze-thaw cycles should be strictly avoided.
Our antibodies are unpurified antiserum collected from our rabbits. These antibodies are then purified by Protein A affinity to make our purified IgG. We typically recommend our unpurified antibodies for immunohistochemistry and tissue staining since they give a stronger signal. Our purified IgG antibodies are best for Western Blots or similar denatured conditions where specificity is more important than sensitivity.


Our standard packaging for I-125 tracers is 10 µCi.
We ship our I-125 tracers on dry ice. Upon receipt, please keep these stored at -20°C in its lyophilized form until it is ready to be used. Once rehydrated, please store at +4°C for up to one week. Due to its half-life, we recommend that the kit be used as soona s possible upon receipt.

Enzyme Immunoassay (EIA) Kits:

The terms EIA and ELISA can be used interchangeably. They are both enzyme immunoassays. For peptides, they are almost always competitive assays.
Any biological fluid with peptide levels in the detectable range can be used. For example, plasma, serum, tissue homogenate, CSF, and saliva have all been successfully assayed with our EIA/ELISA kits.
We ship all of our kits on blue ice packs to keep them chilled during transit. Upon receipt, please store the kit in the fridge at +4°C. Do not freeze the kit.
We recommend assaying all standards, controls, and samples in duplicate. One kit can assay up to 40 samples in duplicate.
Our EIA/ELISA kits require 50 uL of prepared sample per well. If you are not diluting or concentrating samples, this would mean 100 uL of sample if assayed in duplicate.
Our assay kits are valid for 4-6 months from the date you receive them.
Yes, all of our EIA/ELISA kits use a multiwell plate with 12 detachable strips (8 wells each). Any unused plate strips should be placed back in the included resealable foil pouch with the dessicant pack.


Lyophilized peptides should be stored at +4°C. Under these conditions, most peptides are stable for up to 6 months. After rehydration, aliquot the solution and freeze at -20°C to -80°C. Rehydrated, frozen peptides are typically stable for 3 months. Please avoid multiple freeze-thaw cycles.

Peptides containing Trp, Cys, and Met residues can be easily oxidized and are therefore less stable.
In addition to the 3400+ peptides we offer as part of our catalog, we can also synthesis a variety of custom peptides.
This signifies that the peptide is a fragment of a larger pro-hormone or protein. For example, (7-26) would mean that the peptide includes the amino acid residues 7 to 26 of the named protein, starting from the N-terminus.

Delivery Time:

We typically deliver peptides within 1-3 business days of the order.
We typically deliver antibodies within 1-3 business days of the order.
For non-radioactive labeled peptides, we typically deliver the product in 3-6 business days. Radioactive labeled peptides are made to order and typically take 1-2 weeks to deliver.
We typically deliver non-radioactive assay kits within 3 business days of the order.
Due to the short half-life, our radioimmunoasay (RIA) kits are made to order. Labeling of new kits occurs at the beginning of every week for delivery early the following week.