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Toxins 2017, 9(1), 24;

Detection of Naja atra Cardiotoxin Using Adenosine-Based Molecular Beacon

Institute of Biomedical Sciences, National Sun Yat-Sen University, Kaohsiung 804, Taiwan
Department of Biotechnology, Kaohsiung Medical University, Kaohsiung 807, Taiwan
Author to whom correspondence should be addressed.
Academic Editor: Frank S. Markland
Received: 29 October 2016 / Revised: 2 January 2017 / Accepted: 4 January 2017 / Published: 7 January 2017
(This article belongs to the Section Animal Venoms)
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This study presents an adenosine (A)-based molecular beacon (MB) for selective detection of Naja atra cardiotoxin (CTX) that functions by utilizing the competitive binding between CTX and the poly(A) stem of MB to coralyne. The 5′- and 3′-end of MB were labeled with a reporter fluorophore and a non-fluorescent quencher, respectively. Coralyne induced formation of the stem-loop MB structure through A2-coralyne-A2 coordination, causing fluorescence signal turn-off due to fluorescence resonance energy transfer between the fluorophore and quencher. CTX3 could bind to coralyne. Moreover, CTX3 alone induced the folding of MB structure and quenching of MB fluorescence. Unlike that of snake venom α-neurotoxins, the fluorescence signal of coralyne-MB complexes produced a bell-shaped concentration-dependent curve in the presence of CTX3 and CTX isotoxins; a turn-on fluorescence signal was noted when CTX concentration was ≤80 nM, while a turn-off fluorescence signal was noted with a further increase in toxin concentrations. The fluorescence signal of coralyne-MB complexes yielded a bell-shaped curve in response to varying concentrations of N. atra crude venom but not those of Bungarus multicinctus and Protobothrops mucrosquamatus venoms. Moreover, N. nigricollis venom also functioned as N. atra venom to yield a bell-shaped concentration-dependent curve of MB fluorescence signal, again supporting that the hairpin-shaped MB could detect crude venoms containing CTXs. Taken together, our data validate that a platform composed of coralyne-induced stem-loop MB structure selectively detects CTXs. View Full-Text
Keywords: snake venom; cardiotoxin; molecular beacon; polyadenosine; coralyne snake venom; cardiotoxin; molecular beacon; polyadenosine; coralyne

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Shi, Y.-J.; Chen, Y.-J.; Hu, W.-P.; Chang, L.-S. Detection of Naja atra Cardiotoxin Using Adenosine-Based Molecular Beacon. Toxins 2017, 9, 24.

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