The non-chemical bond interaction between small molecule and macromolecule coming from the electrostatic attraction obeys the Langmuir assembly. The interaction of 1,5-di(2-hydroxyl-5-sulfophenyl-)-3-cyanoformazan (DSPCF) and three kinds of proteins: bovine serum albumin (BSA), alpha-globulins (Gb) and ovalbumin (OVA) at pH 1.83 has been investigated and then sodium dodecyl benzene sulfonate (SDBS) was added to replace the DSPCF binding in protein. The microsurface adsorption-spectral correction (MSASC) technique and the break point approach were both used to characterize the aggregates. Results showed that the products: SDBS(99)BSA, SDBS(50)OVA and SDBS(25)Gb at 30 degreesC and SDBS(90)BSA, SDBS(40)OVA and SDBS(20)Gb at 40 degreesC are formed. (C) 2003 Elsevier B.V. All rights reserved.