Interferon-.beta. protein analogs in which the asparagine at position 25, numbered in accordance with native interferon-.beta., is deamidated exhibit a biological activity of native human interferon-.beta. at an increased level and do not require HA for protein stabilization. The deamidated product is suitable for large scale manufacturing for incorporation in HA-containing or HA-free therapeutics for treatment of diseases including multiple sclerosis. An endoproteinase-C peptide map technique that produces a fingerprint profile for proteins using an enzymatic digest followed by RP-HPLC is also useful in quality control as an ID and/or quantitative test for the deamidated products.