Platelet factor 4 (PF4) is a peptide monomer of 70 amino acids (MW 7800 Da). PF4 is released from activated platelet alpha granules in a tetrameric form complexed with platelet proteoglycan. On release, the half-life of PF4 is very short, less than 5 minutes, because it quickly binds to glycosaminoglycans in the endothelial cells where it is stored. PF4 possesses potent anti-heparin activity by binding to it, forming a stochiometric complex, where 1 mg of PF4 will inhibit 27 IU of heparin.
All proteins are accompanied by certificates of analysis which describe the appropriate storage conditions. In order for us to guarantee the stability of the product, it is imperative that the storage conditions are observed. Brief centrifugation of the zymogens in their original packaging will fully recover the sample at the bottom of the tube. Never allow protein solutions to stay at room temperature for excessive periods of time. High temperatures can increase the rate of protein degradation. Avoid storing or maintaining diluted protein samples for an extended period of time. In general, purified proteins are inherently more stable in concentrated form. Many proteins are "clingy" by nature. To avoid protein loss due to adsorption, extremely diluted protein samples should be prepared in buffers containing excipients such as bovine serum albumin, polyethylene glycol, Prionex or gelatin.
