Accession Number:

AD1096732

Title:

Nanoparticle Size Influences Localized Enzymatic Enhancement-A Case Study with Phosphotriesterase

Descriptive Note:

Journal Article - Open Access

Corporate Author:

NAVAL RESEARCH LAB WASHINGTON DC WASHINGTON United States

Personal Author(s):

• Breger ,Joyce C.
• Oh ,Eunkeu
• Susumu ,Kimihiro
• Klein ,William P.
• Walper ,Scott A.
• Ancona ,Mario G.
• Medintz ,Igor L.

Report Date:

2019-07-08

Pagination or Media Count:

15.0

Abstract:

Enhancements in enzymatic catalytic activity are frequently observed when an enzyme is displayed on a nanoparticle NP surface. The exact mechanisms of how this unique interfacial environment gives rise to this phenomenon are still not understood, although evidence suggests that it can help alleviate some of the enzymes rate-limiting mechanistic steps. The physicochemical limitations that govern when this process arises are also not known including, in particular, the range of NP size and curvature that are associated with it. To investigate the latter, we undertook a case study using the enzyme phosphotriesterase PTE and a series of differentially sized gold NPs AuNPs. PTE, expressed with a terminal hexahistidine sequence, was ratiometrically coordinated to a series of increasing size AuNPs diameter similar or equal to 1.5, 5, 10, 20, 55, 100 nm surface-functionalized with Ni2 -nitrilotriacetic acid ligands and its activity assayed in a comparative format versus that of equivalent amounts of free enzyme controls. PTE-AuNP samples were prepared where the total PTE concentration and NP surface density were kept fixed by varying AuNP concentration along with the converse format. Assembly to the AuNPs increased PTE kcat ca. 3-10-fold depending upon NP size, with the smaller-sized particles showing the highest increase, while enzyme efficiency only increased 2-fold. Further kinetic testing suggested that the PTE enhancement again arose from alleviating its rate limiting step of enzyme-product release and not from a change in the activation energy. Comparison of kcat and enzyme specificity with AuNP diameter revealed that enhancement was directly correlated to AuNP size and curvature with the smaller NPs showing the largest kinetic enhancements.

Descriptors:

• chemical reactions
• chemical warfare agents
• energy transfer
• heat of activation
• materials
• nanomaterials
• organic chemistry
• united states
• chemical warfare
• materials laboratories
• nerve agents
• synthetic biology
• materials science
• nanotechnology
• quantum dots
• surface plasmon resonance
• nanoparticles
• metallic nanoparticles
• chemical synthesis
• chemistry

Subject Categories:

Distribution Statement:

APPROVED FOR PUBLIC RELEASE