title: Folding control and unfolding free energy of yeast iso-1-cytochrome c bound to layered zirconium phosphate materials monitored by surface plasmon resonance.
abstract: The free energy change (Delta G degrees ) for the unfolding of immobilized yeast iso-1-cytochrome c (Cyt c) at nanoassemblies was measured by surface plasmon resonance (SPR) spectroscopy. Data show that SPR is sensitive to protein conformational changes, and protein solid interface exerts a major influence on bound protein stability. First, Cyt c was self-assembled on the Au film via the single thiol of Cys-102. Then, crystalline sheets of layered alpha-Zr(O(3)POH)(2).H(2)O (alpha-ZrP) or Zr(O(3)PCH(2)CH(2)COOH)(2).xH(2)O (alpha-ZrCEP) were adsorbed to construct alpha-ZrP/Cyt c/Au or alpha-ZrCEP/Cyt c/Au nanoassemblies. The construction of each layer was monitored by SPR, in real time, and the assemblies were further characterized by atomic force microscopy and electrochemical studies. Thermodynamic stability of the protein nanoassembly was assessed by urea-induced unfolding. Surprisingly, unfolding is reversible in all cases studied here. Stability of Cyt c in alpha-ZrP/Cyt c/Au increased by approximately 4.3 kJ/mol when compared to the unfolding free energy of Cyt c/Au assembly. In contrast, the protein stability decreased by approximately 1.5 kJ/mol for alpha-ZrCEP/Cyt c/Au layer. Thus, OH-decorated surfaces stabilized the protein whereas COOH-decorated surfaces destabilized it. These data quantitate the role of specific functional groups of the inorganic layers in controlling bound protein stability.
authors.affiliation: Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA.
authors.forename: Akhilesh
authors.initials: A
authors.lastname: Bhambhani
authors.forename: Soonwoo
authors.initials: S
authors.lastname: Chah
authors.forename: Eli G
authors.initials: EG
authors.lastname: Hvastkovs
authors.forename: Gary C
authors.initials: GC
authors.lastname: Jensen
authors.forename: James F
authors.initials: JF
authors.lastname: Rusling
authors.forename: Richard N
authors.initials: RN
authors.lastname: Zare
authors.forename: Challa V
authors.initials: CV
authors.lastname: Kumar
mesh_terms: D003543:Cysteamine / Q000737:chemistry; D045304:Cytochromes c / Q000378:metabolism*; D004563:Electrochemistry; D005656:Fungal Proteins / Q000378:metabolism*; D006046:Gold / Q000378:metabolism; D018625:Microscopy, Atomic Force; D011485:Protein Binding; D011489:Protein Denaturation; D017510:Protein Folding; D013057:Spectrum Analysis; D020349:Surface Plasmon Resonance; D013816:Thermodynamics; D015040:Zirconium / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; C027006:zirconium phosphate; D003543:Cysteamine; D006046:Gold; D045304:Cytochromes c; D015040:Zirconium