School of Environmental Science and Engineering, Shandong University, China-America CRC for Environment & Health, Shandong Province, Jinan, P. R. China.
Laboratory of Immunology for Environment and Health, Shandong Analysis and Test Center, Qilu University of Technology (Shandong Academy of Sciences), Jinan, China.
J Mol Recognit. 2018 Aug;31(8):e2712. doi: 10.1002/jmr.2712. Epub 2018 Apr 14.
As a promising biolabeling biomaterials, quantum dots (QDs) present a great potential. However, the toxicity of QDs to organisms has attracted wide attention. In our research, we introduced an in vitro method to study the molecular mechanisms for the structure and activity alterations of Candida rugosa lipase (CRL) with the binding of 3-mercaptopropionic acid-capped CdTe QDs. Multiple spectroscopic methods, isothermal titration calorimetry, and enzyme activity measurements were used in this paper. QDs statically quenched the intrinsic fluorescence of CRL with the quenching constant decreases from 2.46 × 10 to 1.64 × 10 L mol second (298 to 310 K). It binds to CRL through hydrophobic force with 1 binding site, unfolding and loosening the skeleton and changed its secondary structure. Rather than aggregating on the surface, it enters the pocket of the CRL to interact with Ser-209 (2.43 Å) and the residues surrounding Ser-209, making the catalytic triad more exposed. Furthermore, the activity of CRL was inhibited by approximately 15%. This work demonstrates that 3-mercaptopropionic acid-capped CdTe QDs may cause negative effects to CRL and obtains a molecular mechanism on QD-induced toxicity to proteins in vitro.
作为一种有前途的生物标记生物材料，量子点 (QD) 具有很大的潜力。然而，QD 对生物体的毒性引起了广泛关注。在我们的研究中，我们引入了一种体外方法来研究 3-巯基丙酸修饰的 CdTe QD 与 Candida rugosa 脂肪酶 (CRL) 结合时结构和活性变化的分子机制。本文使用了多种光谱方法、等温滴定量热法和酶活性测量。QD 静态猝灭了 CRL 的内源荧光，猝灭常数从 2.46×10 降低到 1.64×10 L/mol 秒（298 至 310 K）。它通过疏水作用力与 CRL 结合，有 1 个结合位点，使骨架展开和松弛，并改变其二级结构。它不是在表面聚集，而是进入 CRL 的口袋与 Ser-209（2.43 Å）和围绕 Ser-209 的残基相互作用，使催化三联体更加暴露。此外，CRL 的活性被抑制了约 15%。这项工作表明，3-巯基丙酸修饰的 CdTe QD 可能对 CRL 产生负面影响，并获得了体外 QD 诱导蛋白质毒性的分子机制。
