title: Structural changes in R-phycoerythrin upon CdS quantum dot synthesis in tunnel cavities of protein molecules.
abstract: Structural changes in R-phycoerythrin used as a matrix for the synthesis of CdS quantum dots have been analyzed by circular dichroism spectrometry. In deionized water, quantum dot synthesis in the tunnel cavity of the R-phycoerythrin molecule proved to be accompanied by uncoiling of α-helices and changes in the conformation of its chromophore groups, with consequent decay of protein fluorescence. Since R-phycoerythrin fluorescence is important for practical applications, conditions for quantum dot synthesis have been optimized by replacing deionized water with 0.01 M MES buffer, pH 5.7. Under such conditions, the size of the CdS quantum dots (determined from atomic force microscopy images) remains the same as in deionized water, but quantum dots cause only minor structural changes in protein molecules, as follows from circular dichroism and absorption spectra. The thermostability of R-phycoerythrin is enhanced, as indicated by an increase in the experimental activation energy for denaturation (from 140.8 to 149.9 kJ/mol) and the intensity of R-phycoerythrin fluorescence is also enhanced approximately twofold.
authors.affiliation: Department of Structural Biochemistry of Proteins, Bach Institute of Biochemistry, Russian Academy of Sciences, Leninsky prospect 33, Moscow 119071, Russia.
authors.forename: O D
authors.initials: OD
authors.lastname: Bekasova
authors.forename: V V
authors.initials: VV
authors.lastname: Shubin
authors.forename: I V
authors.initials: IV
authors.lastname: Safenkova
authors.forename: L I
authors.initials: LI
authors.lastname: Kovalyov
authors.forename: B I
authors.initials: BI
authors.lastname: Kurganov
mesh_terms: D002942:Circular Dichroism; D018625:Microscopy, Atomic Force; D010799:Phycoerythrin / Q000737:chemistry*; D045663:Quantum Dots; D013057:Spectrum Analysis / Q000379:methods; D013816:Thermodynamics
chemical_list: D010799:Phycoerythrin
keywords: CdS quantum dots ‘·’; Circular dichroism; Nanostructure; R-phycoerythrin; RPE·CdS(MES); RPE·CdS(water); Water-soluble matrix; is R-phycoerythrin with a CdS quantum dot synthesized into the internal tunnel of the protein in 0.01M MES buffer, pH 5.7; is R-phycoerythrin with a CdS quantum dot synthesized into the internal tunnel of the protein in deionized water