The thermal polymerization of orosomucoid

1. Orosomucoid was prepared from the urine of a nephrotic patient and polymerized by heating it in a range of salt concentrations at pH4·1. 2. Heating at low ionic strengths produced a `chain' polymer of indefinite length but having the same width as the diameter of the monomer (5·0nm.). Similar treatment in high ionic strengths also produced a spherical (`ball') polymer of limited diameter (14·8nm.). 3. The size and shape of both polymers were determined from ultra-centrifuge, gel-filtration and electron-microscope results. The results suggest that eight monomer units condense to form the ball polymer. 4. Heating orosomucoid at pH1·8 hydrolysed the N-acetylneuraminic acid off the molecule; only chains could then be formed, even in high ionic strengths. 5. Both polymers were stable under normal conditions but could be depolymerized in 3m-guanidine hydrochloride. The monomer could be repolymerized on heating: the `chain monomer' only formed chains at all ionic strengths, but the `ball monomer' was indistinguishable from the original monomer in its immunological properties and polymerization reaction.