Reaction principle of turbidity generation of serum albumin by aromatic organic acid salt

There are the dye-binding method, the biuret method, and the turbidimetric method for determining urine protein. Of the turbidimetric methods, a SSA method that is highly sensitive and reliable is used not only to determine the urine protein concentration but also to confirm a false-positive in a test strip and to screen the Bence-Jones proteins from the discrepancy between the test strip and SSA method. The discrimination of the sample with examination data such as a test strip (-) and the SSA method (+) is very important for diagnosis. The reaction principle of the SSA method is explained by the fact that the SSA anion binds to the positivelycharged protein electrostatically, and the formed protein/organic anion complex generates turbidity by the coherence of the complexes. The author previously investigated whether its theory is proper or not by an experiment and a calculation based on the chemical equilibrium. This investigation revealed that the experimental result agrees with the calculated one on the assumption that only the no-charged protein/organic anion complex generated from the SSA anion and the positively-charged protein condenses into turbidity. If its reaction principle is valid, it is estimated that the aromatic organic acid except the SSA also generates turbidity. The understanding of the reaction principle is very important to avoid measurement error and the appropriate evaluaInt J Anal Bio-Sci Vol. 1, No 1 (2013)