title: Investigation of trypsin-CdSe quantum dot interactions via spectroscopic methods and effects on enzymatic activity.
abstract: The paper presents the interactions between trypsin and water soluble cadmium selenide (CdSe) quantum dots investigated by spectrophotometric methods. CdSe quantum dots have strong ability to quench the intrinsic fluorescence of trypsin by a static quenching mechanism. The quenching has been studied at three different temperatures where the results revealed that electrostatic interactions exist between CdSe quantum dots and trypsin and are responsible to stabilize the complex. The Scatchard plot from quenching revealed 1 binding site for quantum dots by trypsin, the same has been confirmed by making isothermal titrations of quantum dots against trypsin. The distance between donor and acceptor for trypsin-CdSe quantum dot complexes is calculated to be 2.8 nm by energy transfer mechanisms. The intrinsic fluorescence of CdSe quantum dots has also been enhanced by the trypsin, and is linear for concentration of trypsin ranging 1-80 μl. All the observations evidence the formation of trypsin-CdSe quantum dot conjugates, where trypsin retains the enzymatic activity which in turn is temperature and pH dependent.
authors.affiliation: Centre of Advanced Study in Physics, Department of Physics, Panjab University, Chandigarh 160014, India.
authors.forename: Gurvir
authors.initials: G
authors.lastname: Kaur
authors.affiliation: Centre of Advanced Study in Physics, Department of Physics, Panjab University, Chandigarh 160014, India. Electronic address: surya@pu.ac.in.
authors.forename: S K
authors.initials: SK
authors.lastname: Tripathi
mesh_terms: D019187:Cadmium Compounds / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D002151:Calorimetry / Q000379:methods; D002942:Circular Dichroism; D004735:Energy Transfer; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D053758:Nanoparticles / Q000737:chemistry; D045663:Quantum Dots; D018036:Selenium Compounds / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D014357:Trypsin / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D019187:Cadmium Compounds; D018036:Selenium Compounds; C058667:cadmium selenide; D014357:Trypsin
keywords: Binding constant; Enzyme activity; Fluorescence quenching; Förster resonance energy transfer; Quantum dots; Trypsin