Abstract
The effect of protamine on the solubility and deamidation of human growth hormone (hGH) was investigated. Protamine is an extremely basic peptide. It is isolated from sperm cells of salmon where it can build a complex with DNA due to electrostatic interactions. We hypothesize a similar electrostatic effect between negatively charged hGH and positively charged protamine residues. Arising cationic complexes are stabilized by electrostatic repulsion. This stabilizing complexation allows solubilization of hGH down to a pH of 5.4 (pI 5.3) at concentrations of 3.4mg/ml. The minimal solubilizing molar ratio between hGH and protamine was found to be at least 1:23 (hGH:protamine) by turbidity and dynamic light scattering (DLS) measurements. Complexation was characterized by small-angle X-ray scattering (SAXS) and isothermal titration calorimetry (ITC). Electrostatic binding of protamine to hGH was also observed by a reversal in surface charge, as shown by zeta potential measurements. The presence of protamine did not alter the conformational structure of hGH which was determined by circular dichroism (CD) spectroscopy. A pH of 5.4 is known to slow deamidation of hGH and consequently retardation of hGH deamidation could be detected after 3 months storing by reversed-phase high-performance liquid chromatography (RP-HPLC).
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
