Abstract
In this study, we report a detailed experimental, binding free energy calculation and molecular dynamics (MD) simulation investigation of the interactions of carboxylic-functionalized multi-walled carbon nanotubes (COOH-f-MWCNTs) with porcine trypsin (pTry). The enzyme exhibits decreased thermostability at 330K in the presence of COOH-f-MWCNTs. Furthermore, the activity of pTry also decreases in the presence of COOH-f-MWCNTs. The restricted diffusion of the substrate to the active site of the enzyme was observed in the experiment. The MD simulation analysis suggested that this could be because of the blocking of the S1 pocket of pTry, which plays a vital role in the substrate selectivity. The intrinsic fluorescence of pTry is quenched with increase in the COOH-f-MWCNTs concentration. Circular dichroism (CD) and UV–visible absorption spectroscopies indicate the ability of COOH-f-MWCNTs to experience conformational change in the native structure of the enzyme. The binding free energy calculations also show that electrostatics, π-cation, and π-π stacking interactions play important roles in the binding of the carboxylated CNTs with pTry. The MD simulation results demonstrated that the carboxylated CNTs adsorb to the enzyme stronger than the CNT without the–COOH groups. Our observations can provide an example of the nanoscale toxicity of COOH-f-MWCNTs for proteins, which is a critical issue for in vivo application of COOH-f-MWCNTs.
Highlights
Carbon-based nanomaterials have unique atomic conformation, high volume-surface ratio, high electrical conductivity, good optical features, mechanical stability, and easy functionalization capacity
The interactions of COOH-f-MWCNTs with porcine trypsin (pTry) were investigated in this paper by using experimental and molecular dynamics (MD) simulation techniques
The results indicate that the inherent fluorescence intensity of pTry decreases in the presence of increased COOH-f-MWCNTs concentrations based on the static quenching mechanism
Summary
Carbon-based nanomaterials have unique atomic conformation, high volume-surface ratio, high electrical conductivity, good optical features, mechanical stability, and easy functionalization capacity. Nowadays, they have attracted considerable attention in nanobiotechnological and nanomedical applications [1,2,3,4,5,6]. Investigations of interactions of CNTs with drugs and biomolecules have increased biosafety issues for in vivo therapeutic applications [12,13,14,15]. Functionalization of CNTs makes them amenable for further binding of additional biomolecules, significantly increasing their biochemical and biophysical properties [21,22,23]
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