The binding interaction between cadmium‐based, aqueous‐phase quantum dots with Candida rugosa lipase

Abstract

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.

Size-responsive differential modulation in α-amylase by MPA-CdSe QDs: multispectroscopy and molecular docking study

“…Figure 6 shows the activity of enzyme in the presence and absence Enzymatic activity is a very complex process and depends on several factors. The interaction of MPAcapped CdSe QDs with α-amylase results in loss of secondary structure of α-amylase which could be the possible reason of inhibition of enzymatic activity; it is in accordance with previous studies which reported the similar kind of result (Sun et al 2014;Zhao et al 2018). Although the loss in secondary structure was maximum with the MPA-capped CdSe QDs of the largest size (3.9 nm), inhibition of enzymatic activity is found to be maximum with MPA-capped CdSe QDs of the smallest size 1.9 nm followed by 2.3 nm, 2.5 nm, 3.3 nm, and 3.5 nm.…”

“…The results obtained from molecular docking show that hydrogen bonding and hydrophobic interactions are involved in interaction of MPA with α-amylase; however hydrophobic interaction is found as major force of interaction. Experimental results obtained by Das et al (2016) and Zhao et al (2018) also suggested the hydrophobic interaction as major force of interaction in water-soluble MPA-capped cadmium-based QDs with enzyme lysozyme and candida rugosa lipase (CRL), respectively (Das et al 2016;Zhao et al 2018). It was further indicated that MPA have not interacted directly with the catalytic and substrate binding active site of α-amylase, hence acted as non-competitive inhibitor (Zheng et al 2020).…”

Binding mechanism of maltol with catalase investigated by spectroscopy, molecular docking, and enzyme activity assay

“…Generally, proteins have two major absorption bands, which are the strong absorption peak at 210 nm reflecting polypeptide backbone structure of the protein and the weak absorption peak at 280 nm illustrating the transformation of chromophore microenvironment . Upon the gradual addition of maltol to CAT solution, the absorption intensity of the peak at 210 nm decreased significantly, which could reflect the transition of π → π* of the polypeptide backbone structure and the change of CAT skeleton structure . No significant changes of the peak at 280 nm were observed with changes in the concentration of maltol, indicating maltol have no influence on the transformation of CAT chromophores …”

Spectroscopic and molecular docking studies on the binding mechanism of Mobic and lipase

“…Hydrolyzed triglyceride is con-verted into Glycerin and fatty acids are absorbed by the body [6] and play an important role in the process of digestion and absorption. Zhao Lining et al [7] studied the interaction of three mercaptopropionic acid-terminated CdTe quantum dots with lipase, and proved that three mercaptopropionic acid-terminated CdTe quantum dots can cause toxic side effects on lipase; Zhang Rui et al [8] studied the interaction of bisphenol A with lipase in vitro to better understand the toxicity and toxicity mechanism of bisphenol A.…”