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Hydrolytic enzymes conjugated to quantum dots mostly retain whole catalytic activity.
MedLine Citation:
PMID:  24937605     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Tagging a luminescent quantum dot (QD) with a biological like enzyme (Enz) creates value-added entities like quantum dot-enzyme bioconjugates (QDEnzBio) that find utility as sensors to detect glucose or beacons to track enzymes in vivo. For such applications, it is imperative that the enzyme remains catalytically active while the QD is luminescent in the bioconjugate. A critical feature that dictates this is the QD-Enz linkage chemistry. Previously such linkages have put constraints on polypeptide chain dynamics or hindered substrate diffusion to active site, seriously undermining enzyme catalytic activity. In this work we address this issue using Avidin-Biotin linkage chemistry together with a flexible spacer to conjugate enzyme to QD. The catalytic activity of three biotinylated hydrolytic enzymes, namely, Hen eggwhite lysozyme (HEWL), Alkaline phosphatase (ALP) and Acetylcholinesterase (AChE) were investigated post-conjugation to streptavidin linked QD. We demonstrate that all enzymes retain full catalytic activity in the QDEnzBio in comparison to biotinylated enzyme alone. However, unlike ALP and AChE catalytic activity of HEWL was observed to be increasingly susceptible to ionic strength of medium with rising level of biotinylation. This susceptibility was attributed to arise from depletion of positive charge from lysine amino groups after biotinylation. We reasoned that Avidin-Biotin linkage in presence of a flexible seven atom spacer between biotin and enzyme poses no constraints to enzyme structure/dynamics enabling retention of full enzyme activity. Overall our results demonstrate for the first time that streptavidin-biotin chemistry can yield quantum dot enzyme bioconjugates that retain full catalytic activity as native enzyme.
Authors:
Aditya Iyer; Anil Chandra; Rajaram Swaminathan
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2014-6-14
Journal Detail:
Title:  Biochimica et biophysica acta     Volume:  -     ISSN:  0006-3002     ISO Abbreviation:  Biochim. Biophys. Acta     Publication Date:  2014 Jun 
Date Detail:
Created Date:  2014-6-17     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0217513     Medline TA:  Biochim Biophys Acta     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2014. Published by Elsevier B.V.
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