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Comparative functional dynamics studies on the enzyme nano-bio interface

Authors Thomas SE, Comer J, Kim MJ, Marroquin S, Murthy V, Ramani M, Hopke TG, McCall J, Choi SO, DeLong RK

Received 21 September 2017

Accepted for publication 17 March 2018

Published 8 August 2018 Volume 2018:13 Pages 4523—4536


Checked for plagiarism Yes

Review by Single-blind

Peer reviewers approved by Dr Govarthanan Muthusamy

Peer reviewer comments 3

Editor who approved publication: Dr Thomas Webster

Video abstract presented by Robert K DeLong.

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Spencer E Thomas,1,2,* Jeffrey Comer,1,* Min Jung Kim,1 Shanna Marroquin,1 Vaibhav Murthy,1 Meghana Ramani,1 Tabetha Gaile Hopke,2 Jayden McCall,1 Seong-O Choi,1 Robert K DeLong1

1Nanotechnology Innovation Center of Kansas State, Department of Anatomy and Physiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA; 2Department of Biomedical Science, Missouri State University, Springfield, MO, USA

*These authors contributed equally to this work

Introduction: Biomedical applications of nanoparticles (NPs) as enzyme inhibitors have recently come to light. Oxides of metals native to the physiological environment (eg, Fe, Zn, Mg, etc.) are of particular interest—especially the functional consequences of their enzyme interaction.
Materials and methods: Here, Fe2O3, zinc oxide (ZnO), magnesium oxide (MgO) and nickel oxide (NiO) NPs are compared to copper (Cu) and boron carbide (B4C) NPs. The functional impact of NP interaction to the model enzyme luciferase is determined by 2-dimensional fluorescence difference spectroscopy (2-D FDS) and 2-dimensional photoluminescence difference spectroscopy (2-D PLDS). By 2-D FDS analysis, the change in maximal intensity and in 2-D FDS area under the curve (AUC) is in the order Cu~B4C>ZnO>NiO>>Fe2O3>MgO. The induced changes in protein conformation are confirmed by tryptic digests and gel electrophoresis.
Results: Analysis of possible trypsin cleavage sites suggest that cleavage mostly occurs in the range of residues 112–155 and 372–439, giving a major 45 kDa band. By 2-D PLDS, it is found that B4C NPs completely ablate bioluminescence, while Cu and Fe2O3 NPs yield a unique bimodal negative decay rate, -7.67×103 and -3.50×101 relative light units respectively. Cu NPs, in particular, give a remarkable 271% change in enzyme activity. Molecular dynamics simulations in water predicted that the surfaces of metal oxide NPs become capped with metal hydroxide groups under physiological conditions, while the surface of B4C becomes populated with boronic acid or borinic acid groups. These predictions are supported by the experimentally determined zeta potential. Thin layer chromatography patterns further support this conception of the NP surfaces, where stabilizing interactions were in the order ionic>polar>non-polar for the series tested.
Conclusion: Overall the results suggest that B4C and Cu NP functional dynamics on enzyme biochemistry are unique and should be examined further for potential ramifications on other model, physiological or disease-relevant enzymes.

Keywords: 2-dimensional fluorescence difference, 2-D FDS, AUC, corrected light intensity emitted, emission wavelength, excitation wavelength, wavelength of max intensity, RLU

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