The document discusses a patent application for a mutein (mutated form) of Placental Growth Factor Type 1 called rhPlGF-1CG. The wild type rhPlGF-1 has a tendency to polymerize and precipitate out of solution. The mutein replaces free cysteine residues with glycines to increase stability in solution. Tests showed the mutein rhPlGF-1CG remained soluble and monomeric when stored in phosphate buffer saline at 4°C, unlike the wild type rhPlGF-1 which polymerized.