Interaction of a novel peptoid enhancer--arginine oligomer with bovine submaxillary mucin.
OBJECTIVE
To determine the thermodynamics of binding reaction of arginine oligomer (R8) to bovine submaxillary mucin (BSM) in order to provide the foundation for understanding the influence of mucin on transport of macromolecules through mucosa mediated by arginine oligomer.


METHODS
Ultracentrifugation sedimentation was employed to investigate the interaction of BSM-R8. The mixtures of R8 with variable concentration and constant volume of BSM were placed on a shaker under oscillation at 25 degrees C to achieve equilibriums of binding reaction, and then centrifuged. The fluorescence intensity of the supernatant was measured by spectrofluorometer. The data were described by two types of binding sites model, the binding parameters of BSM-R8 were obtained by Scatchard plots.


RESULTS
At the low pH values < or = 4.5 and ionic strength > or = 0.2 mol x L(-1), the BSM-R8 interaction was principally electrostatic interaction, the five primary binding sites (n1) predominantly were supplied by sulfate groups, the secondary binding sites apparently depended on pH, in that percent ionization of sialic acid residues (n2) in BSM. At the low ionic strength < or = 0.2 mol x L(-1) and pH 7.0, the BSM-R8 interaction was exceedingly complex, hydrogen bonds, hydrophobic interaction and electrostatic forces were involved in the interaction between R8 and BSM, the binding sites of BSM bound R8 were markedly increased.


CONCLUSIONS
There existed evidence that R8 interacted with BSM. The pH and the ionic strength of the binding solution strongly affected the interaction of BSM with R8. The results suggested that the enhancing efficacy of the arginine oligomer for the transport of macromolecules through different site mucosa in body might be variable.
Liang
Wei
W
National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China. weixx@sun5.ibp.ac.cn
Davalian
Dariush
D
Torchilin
Vladimir P
VP
D001120:Arginine / Q000737:chemistry*; D001665:Binding Sites; D006863:Hydrogen-Ion Concentration; D009077:Mucins / Q000737:chemistry*; D009994:Osmolar Concentration; D011485:Protein Binding; D013816:Thermodynamics
C115439:BSM1 protein, Bos taurus; D009077:Mucins; D001120:Arginine