Product Specifications Recombinant Human IGFBP-4: Human IGF-Binding protein 4 is produced in genetically engineered yeast, and purified by affinity chromatography and HPLC. Link to Sequence. Molecular Weight: 24,000 daltons Biological Activity: Binding activity of human IGF-BP 4 is determined by the inhibition activity of both IGF-I and IGF-II. Purity: The material has been judged to be >90% pure, as determined by SDS gel electrophoresis. Stability: Lyophilized human IGF-BP 4 is stable at 4 °C for at least one year. Storage: Upon receipt, the material should be stored at 4 °C. Reconstitution of lyophilized IGF-BP 4 is best in water or buffer near neutral pH. After reconstitution, storage in aliquots at minus 80 °C is recommended. Formulation: Lyophilized powder.