An isotype control is an antibody that is the same IgG isotype as the primary antibody, but raised against an irrelevant antigen. An isotype control should produce negative staining results, thereby giving you confidence in the staining observed with the target-specific antibody. The Supplemental Products tab on the product page indicates appropriate isotype controls for that product. Here is an example: https://www.rndsystems.com/products/mouse-cd4-apc-conjugated-antibody-gk15_fab554a#supplemental-products
In a direct ELISA, a plate is coated with the analyte of interest and a labeled detection antibody is used to verify the presence of the analyte. The direct ELISA may use a colorimetric, chemiluminescent, or fluorescent reporter.
R&D Systems has established a policy of not limiting the useful life of a product by providing an expiration date or manufacture date for our protein and antibody products. Under proper storage conditions, proteins and antibodies tend to be stable for many years. These conditions include storing proteins as lyophilized powder, storing the product frozen (-20° C or -80° C) at protein concentrations of greater than 0.1 mg/mL, and limiting the number of freeze/thaw cycles. Please see individual product datasheets for specific instructions. Routine quality control testing by our company ensures that all products have acceptable biological activities at the time of sale. R&D Systems can not control storage conditions of a product upon receipt by the end user. In lieu of an expiration date, we choose to offer a warranty on our protein and antibody products. All products supplied by R&D Systems are warranted to meet or exceed our published specification when used under normal conditions in your laboratory.Typically, this warranty will extend 6-12 months from time of purchase. Please see individual datasheets for specific stability claims. If the product fails during the stated period, a replacement product or credit will be issued. For details regarding our warranty please see http://www.rndsystems.com/customer_service_legal.aspx.
It is possible that the presence of trehalose will interfere in the successful conjugation of a protein. This will depend on the method used, and the customer should investigate this potential prior to purchasing the product.
We have seen no adverse effect in our bioassays or other approved applications. However, customers are advised to run a control in their assay to determine if the concentration of trehalose in the protein or antibody formulation has any adverse effects.
Trehalose is a non-reducing sugar and does not react with amino acids or proteins as part of the Maillard reaction. It is found in nature in many plants and animals. Trehalose is an effective sugar for stabilizing proteins against damage caused by freezing. It can also make the protein more resistant to moisture when lyophilized, resulting in a product that is less likely to precipitate when reconstituted.
Trehalose is unlikely to have an effect in vivo. It has been approved as an excipient for use in human injectable drugs.The trehalose used by R&D Systems is derived from Saccharomyces cerevisiae and is determined to be at minimum 98.5% pure by HPAE.