Composition and conformation of Cryptosporidium parvum oocyst wall surface macromolecules and their effect on adhesion kinetics of oocysts on quartz surface.

We characterized the composition and conformation of Cryptosporidium parvum ( C. parvum ) oocyst wall surface macromolecules and studied their effect on interactions between C. parvum oocyst and quartz surface. Proteinase K and mixed glycosidases were used to modify C. parvum oocyst surface macromolecules. The peptides released by proteinase K and carbohydrates hydrolyzed by mixed glycosidases were respectively analyzed with liquid chromatography/nanoelectrospray ionization tandem mass spectrometry (LC-MS/MS) and phenol-sulfuric acid assay to determine the composition of C. parvum oocyst wall surface macromolecules. Surface potential and polarity of the untreated and proteinase treated C. parvum oocysts revealed information about the conformation of oocyst wall surface macromolecules. The results illustrated that C. parvum oocyst wall is covered by a fluffy layer of glycoproteins. Adhesion kinetics of untreated and proteinase K treated C. parvum oocysts on quartz surface were studied in a radial stagnation point flow cell over a wide range of ionic strength to investigate the effect of C. parvum oocyst wall surface macromolecules on oocysts-quartz interactions. The adhesion rate coefficient of proteinase K treated C. parvum oocysts significantly decreased compared to that of untreated oocysts. This observation indicated that the fluffy layer on C. parvum oocysts wall leads to weaker van der Waals interaction and stronger steric repulsion.