title: Investigation on the interaction between colloidal gold and human complement factor 4 at different pH by spectral methods.
abstract: The interaction between colloidal gold and human complement factor 4 (human C4) at different pH was investigated by spectral methods, including absorption and resonance light-scattering spectrometry. According to the changes of color and absorption spectra of colloidal gold solution in presence of human C4, the interaction between colloidal gold and human C4 was quantitatively investigated using a semi-empirical "flocculation parameter". At the same time, the changes of resonance light-scattering spectra and transmission electron microscopy (TEM) images indicate that the aggregation of colloidal gold happens by electrostatic interaction in presence of human C4 in the pH range 5-6. However, the colloidal gold solution remains stable at pH >6 and pH <5 due to the repulsive electrostatic interaction between colloidal gold and human C4. The flocculation parameter is directly proportional to the concentration of human C4 in the range from 9.7 to 233.0 microgl(-1). In addition, the interactions between the colloidal gold and bovine serum albumin (BSA) as well as human serum albumin (HSA) were also investigated using the same methods. It was found that there was no aggregation of colloidal gold in presence of BSA and HSA in the pH range 5-6. However, when the pH of solution is 4, the aggregation of colloidal gold happens. Because BSA and HSA have different structure, the intensity of aggregation of colloidal gold in presence of BSA is greater than that in presence of HSA at pH 4.
authors.affiliation: College of Chemistry, Jilin University, Changchun 130012, China.
authors.forename: Dejiang
authors.initials: D
authors.lastname: Gao
authors.forename: Yuan
authors.initials: Y
authors.lastname: Tian
authors.forename: Fanghui
authors.initials: F
authors.lastname: Liang
authors.forename: Lan
authors.initials: L
authors.lastname: Ding
authors.forename: Shuyun
authors.initials: S
authors.lastname: Bi
authors.forename: Yanhua
authors.initials: Y
authors.lastname: Chen
authors.forename: Hanqi
authors.initials: H
authors.lastname: Zhang
authors.forename: Aimin
authors.initials: A
authors.lastname: Yu
mesh_terms: D000818:Animals; D002417:Cattle; D003181:Complement C4 / Q000737:chemistry / Q000378:metabolism*; D017979:Gold Colloid / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008027:Light; D012542:Scattering, Radiation; D012709:Serum Albumin / Q000737:chemistry / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000737:chemistry / Q000378:metabolism*
chemical_list: D003181:Complement C4; D017979:Gold Colloid; D012709:Serum Albumin; D012710:Serum Albumin, Bovine