title: Dehydration-induced conformational changes of poly-L-lysine as influenced by drying rate and carbohydrates.
abstract: The conformation of hydrated and air-dried poly-L-lysine in thin films was studied using Fourier transform IR spectroscopy in the amide-I region. Hydrated poly-L-lysine has a random coil conformation. Upon slow drying of small droplets of the polypeptide solution over a period of several hours, an extended beta-sheet conformation is adopted. This conformational transition can be prevented by fast air-drying within 2-3 min. Slow air-drying in the presence of sucrose also preserves the aqueous conformation and results in the formation of a glassy state. Comparison of shifts of the OH band with temperature indicates that sucrose/poly-L-lysine mixtures form a molecularly more densely packed glassy matrix, having a higher glass transition temperature (Tg), than sucrose alone. Whether direct interaction of sugar and polypeptide or glass formation is involved in the stabilization during slow air-drying was studied by drying in the presence of glucose or dextran. Compared with dextran (and sucrose to a lesser extent), glucose gives superior protection. Dried glucose has the lowest Tg and the best interacting properties. We conclude that either immobilization by fast air-drying or sufficient interaction with a protectant through hydrogen bonding (slow drying) plays the leading role in the preservation of the aqueous protein structure.
authors.affiliation: Department of Biomolecular Sciences, Laboratory of Plant Physiology, Wageningen Agricultural University, Netherlands. wim.wolkers@algem.pf.wau.nl
authors.forename: W F
authors.initials: WF
authors.lastname: Wolkers
authors.forename: M G
authors.initials: MG
authors.lastname: van Kilsdonk
authors.forename: F A
authors.initials: FA
authors.lastname: Hoekstra
mesh_terms: D003890:Desiccation; D003911:Dextrans / Q000737:chemistry / Q000494:pharmacology; D005947:Glucose / Q000737:chemistry / Q000494:pharmacology; D006860:Hydrogen Bonding; D066298:In Vitro Techniques; D011107:Polylysine / Q000737:chemistry*; D011487:Protein Conformation / Q000187:drug effects; D017433:Protein Structure, Secondary / Q000187:drug effects; D017550:Spectroscopy, Fourier Transform Infrared; D013395:Sucrose / Q000737:chemistry / Q000494:pharmacology; D013816:Thermodynamics
chemical_list: D003911:Dextrans; D011107:Polylysine; D013395:Sucrose; D005947:Glucose