title: Spectroscopic investigations on the effect of N-acetyl-L-cysteine-capped CdTe Quantum Dots on catalase.
abstract: Quantum dots (QDs) are recognized as some of the most promising semiconductor nanocrystals in biomedical applications. However, the potential toxicity of QDs has aroused wide public concern. Catalase (CAT) is a common enzyme in animal and plant tissues. For the potential application of QDs in vivo, it is important to investigate the interaction of QDs with CAT. In this work, the effect of N-Acetyl-L-cysteine-Capped CdTe Quantum Dots with fluorescence emission peak at 612 nm (QDs-612) on CAT was investigated by fluorescence, synchronous fluorescence, fluorescence lifetime, ultraviolet-visible (UV-vis) absorption and circular dichroism (CD) techniques. Binding of QDs-612 to CAT caused static quenching of the fluorescence, the change of the secondary structure of CAT and the alteration of the microenvironment of tryptophan residues. The association constants K were determined to be K288K=7.98×10(5)Lmol(-1) and K298K=7.21×10(5)Lmol(-1). The interaction between QDs-612 and CAT was spontaneous with 1:1 stoichiometry approximately. The CAT activity was also inhibited for the bound QDs-612. This work provides direct evidence about enzyme toxicity of QDs-612 to CAT in vitro and establishes a new strategy to investigate the interaction between enzyme and QDs at a molecular level, which is helpful for clarifying the bioactivities of QDs in vivo.
authors.affiliation: School of Environmental Science and Engineering, Shandong University, China-America CRC for Environment & Health, Shandong Province, 27# Shanda South Road, Jinan 250100, PR China.
authors.forename: Haoyu
authors.initials: H
authors.lastname: Sun
authors.affiliation: School of Environmental Science and Engineering, Shandong University, China-America CRC for Environment & Health, Shandong Province, 27# Shanda South Road, Jinan 250100, PR China.
authors.forename: Bingjun
authors.initials: B
authors.lastname: Yang
authors.affiliation: School of Environmental Science and Engineering, Shandong University, China-America CRC for Environment & Health, Shandong Province, 27# Shanda South Road, Jinan 250100, PR China.
authors.forename: Erqian
authors.initials: E
authors.lastname: Cui
authors.affiliation: School of Environmental Science and Engineering, Shandong University, China-America CRC for Environment & Health, Shandong Province, 27# Shanda South Road, Jinan 250100, PR China. Electronic address: rutaoliu@sdu.edu.cn.
authors.forename: Rutao
authors.initials: R
authors.lastname: Liu
mesh_terms: D000111:Acetylcysteine / Q000737:chemistry*; D000818:Animals; D019187:Cadmium Compounds / Q000737:chemistry*; D002374:Catalase / Q000737:chemistry*; D002417:Cattle; D002942:Circular Dichroism; D007700:Kinetics; D011485:Protein Binding; D017433:Protein Structure, Secondary; D045663:Quantum Dots / Q000737:chemistry* / Q000648:ultrastructure; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013691:Tellurium / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D019187:Cadmium Compounds; D002374:Catalase; D013691:Tellurium; C028337:cadmium telluride; D000111:Acetylcysteine
keywords: Activity inhibition; Catalase; QDs; Spectroscopic studies; Static and dynamic quenching