title: Combined QCMD and AFM studies of lysozyme and poly-L-lysine-poly-galacturonic acid multilayers.
abstract: A quartz crystal microbalance with dissipation monitoring (QCMD) has been used to monitor the adsorption and structure of lysozyme monolayers and multilayers, and poly-L-lysine (PLL)-polygalacturonic acid (PGalA) multilayers at a solid-liquid interface using freshly-cleaved mica as a substrate. QCMD measurements were complemented with atomic force microscopy (AFM). AFM images revealed that lysozyme formed incomplete monolayers and provided a basis for calculation of the thickness of the protein film. Comparative studies of adsorption onto standard and mica-coated quartz crystals showed higher areal mass adsorption and a longer-time adsorption process for mica-coated quartz crystals. Simultaneous AFM images and QCMD data were obtained for lysozyme, linear PLL-PGalA and 7 nm PLL dendrimer-PGalA multilayers. The layer-by-layer deposited multilayer films exhibited viscoelastic properties and their growth followed a non-linear regime, associated with the PLL diffusion in and out of the film formation for linear PLL-PGalA films. For the PLL 7 nm dendrimer-PGalA films the AFM images revealed marked changes in surface roughness during layer by layer deposition: these changes influence the interpretation of the QCMD data and provide additional information on the growth and structure of the multilayers.
authors.affiliation: Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK.
authors.forename: Marta
authors.initials: M
authors.lastname: Westwood
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Kirby
authors.forename: Roger
authors.initials: R
authors.lastname: Parker
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Morris
mesh_terms: D000818:Animals; D002645:Chickens; D018625:Microscopy, Atomic Force; D009113:Muramidase / Q000737:chemistry* / Q000648:ultrastructure; D010368:Pectins / Q000737:chemistry* / Q000648:ultrastructure; D011107:Polylysine / Q000737:chemistry*; D058525:Quartz Crystal Microbalance Techniques
chemical_list: D011107:Polylysine; D010368:Pectins; D009113:Muramidase; C003181:polygalacturonic acid