title: On the surface interactions of proteins with lignin.
abstract: Lignins are used often in formulations involving proteins but little is known about the surface interactions between these important biomacromolecules. In this work, we investigate the interactions at the solid-liquid interface of lignin with the two main proteins in soy, glycinin (11S) and β-conglycinin (7S). The extent of adsorption of 11S and 7S onto lignin films and the degree of hydration of the interfacial layers is quantified via Quartz crystal microgravimetry (QCM) and surface plasmon resonance (SPR). Solution ionic strength and protein denaturation (2-mercaptoethanol and urea) critically affect the adsorption process as protein molecules undergo conformational changes and their hydrophobic or hydrophilic amino acid residues interact with the surrounding medium. In general, the adsorption of the undenatured proteins onto lignin is more extensive compared to that of the denatured biomolecules and a large amount of water is coupled to the adsorbed molecules. The reduction in water contact angle after protein adsorption (by ~40° and 35° for undenatured 11S and 7S, respectively) is explained by strong nonspecific interactions between soy proteins and lignin.
authors.affiliation: Department of Forest Biomaterials, North Carolina State University, Raleigh, North Carolina 27695, United States.
authors.forename: Carlos
authors.initials: C
authors.lastname: Salas
authors.forename: Orlando J
authors.initials: OJ
authors.lastname: Rojas
authors.forename: Lucian A
authors.initials: LA
authors.lastname: Lucia
authors.forename: Martin A
authors.initials: MA
authors.lastname: Hubbe
authors.forename: Jan
authors.initials: J
authors.lastname: Genzer
mesh_terms: D000327:Adsorption; D052179:Antigens, Plant / Q000737:chemistry* / Q000378:metabolism; D004058:Diffusion; D005916:Globulins / Q000737:chemistry* / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D008031:Lignin / Q000737:chemistry* / Q000378:metabolism; D008623:Mercaptoethanol / Q000737:chemistry; D011489:Protein Denaturation; D055314:Seed Storage Proteins / Q000737:chemistry* / Q000378:metabolism; D030262:Soybean Proteins / Q000737:chemistry* / Q000378:metabolism; D020349:Surface Plasmon Resonance; D014508:Urea / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D052179:Antigens, Plant; D005916:Globulins; D055314:Seed Storage Proteins; D030262:Soybean Proteins; C013894:beta-conglycinin protein, Glycine max; D014867:Water; D008623:Mercaptoethanol; D014508:Urea; D008031:Lignin; C011474:glycinin