Dataset Information

Exploiting pH-Regulated Dimer-Tetramer Transformation of Concanavalin A to Develop Colorimetric Biosensing of Bacteria.

ABSTRACT: Gold nanoparticles (AuNPs) aggregation-based colorimetric biosensing remains a challenge for bacteria due to their large size. Here we propose a novel colorimetric biosensor for rapid detection of Escherichia coli O157:H7 (E. coli O157:H7) in milk samples based on pH-regulated transformation of dimer/tetramer of Concanavalin A (Con A) and the Con A-glycosyl recognition. Briefly, antibody-modified magnetic nanoparticles was used to capture and concentrate E. coli O157:H7 and then to label with Con A; pH adjusted to 5 was then applied to dissociate Con A tetramer to release dimer, which was collected and re-formed tetramer at pH of 7 to cause the aggregation of dextran-modified AuNPs. The interesting pH-dependent conformation-transformation behavior of Con A innovated the design of the release from the bacteria surface and then the reconstruction of Con A. Therefore, we realized the sensitive colorimetric biosensing of bacteria, which are much larger than AuNPs that is generally not suitable for this kind of method. The proposed biosensor exhibited a limit of detection down to 41?CFU/mL, short assay time (~95?min) and satisfactory specificity. The biosensor also worked well for the detection in milk sample, and may provide a universal concept for the design of colorimetric biosensors for bacteria and virus.

SUBMITTER: Xu X

PROVIDER: S-EPMC5431225 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

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Exploiting pH-Regulated Dimer-Tetramer Transformation of Concanavalin A to Develop Colorimetric Biosensing of Bacteria.

Xu Xiahong X Yuan Yuwei Y Hu Guixian G Wang Xiangyun X Qi Peipei P Wang Zhiwei Z Wang Qiang Q Wang Xinquan X Fu Yingchun Y Li Yanbin Y Yang Hua H

Scientific reports 20170503 1

Gold nanoparticles (AuNPs) aggregation-based colorimetric biosensing remains a challenge for bacteria due to their large size. Here we propose a novel colorimetric biosensor for rapid detection of Escherichia coli O157:H7 (E. coli O157:H7) in milk samples based on pH-regulated transformation of dimer/tetramer of Concanavalin A (Con A) and the Con A-glycosyl recognition. Briefly, antibody-modified magnetic nanoparticles was used to capture and concentrate E. coli O157:H7 and then to label with Co ...[more]

PMID: 28469128

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Project description:The ground-state properties of (NO)(2) and (NO)(4) have been investigated using multireference second-order perturbation theory (MRMP2) and include a two-tier extrapolation to the complete basis set (CBS) limit. For the NO dimer the MRMP2(18,14)/CBS predicted structure, binding energy (with respect to 2NO; D(e) = 3.46 kcal/mol), and dipole moment (u(e) = 0.169 D) are in excellent agreement with experimental measurements (D(e) = 2.8-3.8 kcal/mol; u(e) = 0.171 D). Additionally, three of four intermolecular anharmonic MRMP2(18,14)/CBS-estimated frequencies (143 cm(-1), 238 cm(-1), 421 cm(-1)) are in excellent agreement with recent gas-phase experimental measurements (135 cm(-1), 239 cm(-1), 429/428 cm(-1)); however, the predicted value of 151 cm(-1) for the out-of-plane torsion (A(2)) is elevated compared to recent experimental estimates of 97-117 cm(-1). Our finding that this infrared-forbidden vibration is also predicted to have an extremely low Raman activity (0.04 Å/amu at the MP2/QZ level of theory) conflicts with Raman measurements of a strong intensity for a low frequency band; however, these studies were performed for low temperature solid and liquid phases. Probing the possibility of the presence of higher order clusters we investigated the stability of (NO)(4) and discovered three isomers, each resembling pairs of dimers, that were stable to dissociation to 2(NO)(2), with the lowest-energy isomer (C(i) structure) having a predicted binding energy almost identical to that of the dimer. Computed vibrational frequencies of the C(i) isomer indicate that the 12 highest-frequency modes resemble barely shifted NO dimer-combined bands while the 13th highest-frequency mode at ~100 cm(-1) is exclusive to (NO)(4). Moreover, this tetramer-unique vibration is infrared inactive but has a very high predicted Raman activity of some 24 Å/amu. Guided by the theoretical results, we reexamined and reassigned experimental Raman and infrared data going back to 1951 and determined that our best predictions of vibrational frequencies of (NO)(2) and (NO)(4) are consistent with experimental observations. We thus postulate the existence and observation of (NO)(4).

Dataset Information

Exploiting pH-Regulated Dimer-Tetramer Transformation of Concanavalin A to Develop Colorimetric Biosensing of Bacteria.

Publications

Exploiting pH-Regulated Dimer-Tetramer Transformation of Concanavalin A to Develop Colorimetric Biosensing of Bacteria.

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