title: The role of colloid particles in the albumin-lanthanides interaction: The study of aggregation mechanisms.
abstract: We studied the interaction between bovine serum albumin (BSA) and lanthanide ions in aqueous solution in the 4.0÷9.5pH range. A strong increase of the solution turbidity was observed at pH values exceeding 6, which corresponds to the formation of Ln(OH)3 nanoparticles, while no changes were observed near the isoelectric point of BSA (pH 4.7). The results of the dynamic light scattering and protein adsorption measurements clearly demonstrated that the observed turbidity enhancement was caused by albumin sorption on the surface of Ln(OH)3 and colloid particles bridging via adsorbed protein molecules. Upon pH increase from 4.5 to 6.5, albumin adsorption on lanthanide colloids was observed, while the following increase of pH from 6.5 to 9.5 led to protein desorption. The predominant role of the electrostatic interactions in the adsorption and desorption processes were revealed in the zeta-potential measurements. No reversibility was observed upon decreasing pH from 9.5 to 4.5 that was suggested to be due to the other interaction mechanisms present in the system. It was shown that while for all lanthanide ions the interaction mechanism with BSA was similar, its manifestation in the optical properties of the system was significantly different. This was interpreted as a consequence of the differences in lanthanides hydrolysis constants.
authors.affiliation: International Laser Center, Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia. Electronic address: tikhonova@physics.msu.ru.
authors.forename: Tatiana N
authors.initials: TN
authors.lastname: Tikhonova
authors.affiliation: Department of Physics, Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia. Electronic address: shirshin@lid.phys.msu.ru.
authors.forename: Evgeny A
authors.initials: EA
authors.lastname: Shirshin
authors.affiliation: Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia.
authors.forename: Anna Yu
authors.initials: AY
authors.lastname: Romanchuk
authors.affiliation: Department of Physics, Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia.
authors.forename: Victor V
authors.initials: VV
authors.lastname: Fadeev
mesh_terms: D000327:Adsorption; D000818:Animals; D002417:Cattle; D003102:Colloids / Q000737:chemistry* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D028581:Lanthanoid Series Elements / Q000737:chemistry* / Q000378:metabolism; D053758:Nanoparticles / Q000737:chemistry* / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000737:chemistry* / Q000378:metabolism; D055672:Static Electricity; D013499:Surface Properties
chemical_list: D003102:Colloids; D028581:Lanthanoid Series Elements; D012710:Serum Albumin, Bovine
keywords: Adsorption; Aggregation; Bovine serum albumin; Colloidal particles; Dynamic light scattering; Lanthanides