The Precipitation of Proteinfrom Parotid Fluid

¹ Dental Sciences Division, USAF School of Aerospace Medicine, Brooks Air Force Base, Texas

The effectiveness of 11 protein precipitation methods on parotid fluid was investigated by measuring total nitrogen concentration and total protein concentration on the protein-free filtrates. Nitrogen measurements were performed by a semimicro-Kjeldahl procedure, and the proteins were measured by the Lowry method. Three of the methods were found to remove all the protein, but none appeared to be ideally suited for nonprotein nitrogen determinations. An additional method was reported to remove all the protein without affecting the nonprotein nitrogen concentration. This method, a modification of the Folin-Wu procedure, was recommended for nonprotein nitrogen determinations. The three most effective methods were evaluated on 10 individual samples. No individual sample peculiarities were observed.