title: Adsorption of fluorescein by protein crystals.
abstract: Adsorption characteristics of native and cross-linked lysozyme crystals were examined using fluorescein as model adsorbate. The adsorption isotherms exhibited Langmuir or linear behavior. The affinity constant (b1) and the adsorption capacity (Qsat) for fluorescein were found to depend on the type and concentration of co-solute present in the solution. The dynamics of adsorption isotherm transition from Langmuir to linear showed that affinity of lysozyme for solutes increases in the order 2-(cyclohexylamino)ethanesulphonic acid (CHES), 4-morpholinepropanesulphonic acid (MOPS), acetate, fluorescein. Furthermore, the crystal morphology, the degree of cross-linking of the crystals, and, in particular, solution pH were identified as factors determining fluorescein adsorption by the lysozyme crystals. These factors seem to affect crystal capacity for the solute more than affinity for the solute. Adsorption of fluorescein by cross-linked tetragonal lysozyme crystals was exponentially dependent on the lysozyme net charge calculated from the final solution pH. The 3-5-fold increase in the fluorescein adsorption as a result of cross-linking is presumably due to the increasing hydrophobicity of the lysozyme crystal.
authors.affiliation: Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Cvetkovic
authors.forename: M
authors.initials: M
authors.lastname: Zomerdijk
authors.forename: A J J
authors.initials: AJ
authors.lastname: Straathof
authors.forename: R
authors.initials: R
authors.lastname: Krishna
authors.forename: L A M
authors.initials: LA
authors.lastname: van der Wielen
mesh_terms: D000327:Adsorption; D000818:Animals; D002645:Chickens; D003460:Crystallization; D005374:Filtration; D019793:Fluorescein / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D016014:Linear Models; D009025:Morpholines / Q000737:chemistry; D009113:Muramidase / Q000737:chemistry*
chemical_list: D009025:Morpholines; C008550:morpholinopropane sulfonic acid; D009113:Muramidase; D019793:Fluorescein