Simultaneous stochastic sensing of divalent metal ions

Braha, Orit; Gu, Li-Qun; Zhou, Li; Lu, Xiaofeng; Cheley, Stephen; Bayley, Hagan

doi:10.1038/79275

Cited by 293 publications

(262 citation statements)

References 15 publications

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“…One of the purposes of protein pore study is to detect single molecules. For this purpose protein pores were modulated into a lipid bilayer; they were heteromeric in form for detection of a divalent metal ion, M(II) [30] or simultaneous detection of different M(II)s [31]. In principle, M(II) or different M(II)s were detected as a change in ionic current passing through single pores in planar bilayers.…”

Section: Receptors and Ion Channelsmentioning

confidence: 99%

Current research activity in biosensors

Nakamura

Karube

2003

Analytical and Bioanalytical Chemistry

261

129

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Biosensors consist of a molecular recognition element and a transducer. Since the first biosensor was developed by Updike and Hicks many biosensors and their associated techniques have been studied and developed. In this review current research activity on the fundamentals and applications of biosensors is summarized. In discussion of the former, molecular recognition elements, techniques and tools for biosensor construction, and basic biosensor devices are introduced. Coverage of the latter includes description of biosensors for environmental, food, and clinical fields. Chemical sensors developed in our laboratory for environmental monitoring are also described. This review mainly summarizes work performed by our group and by our colleagues, and refers to the main review articles summarizing each field of biosensor research in recent years.

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Section: Receptors and Ion Channelsmentioning

confidence: 99%

Current research activity in biosensors

Nakamura

Karube

2003

Analytical and Bioanalytical Chemistry

261

129

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“…[2] This has allowed stochastic sensing of analytes down to the single molecule level. [3][4][5] There are a variety of phospholipid membrane systems and detection schemes that can accommodate a host of applications and signal transduction mechanisms. However, the varieties of substrates capable of supporting phospholipid bilayers for electrochemical and optical sensing are somewhat limited.…”

Section: Introductionmentioning

confidence: 99%

Supported Lipid Bilayer on Nanocrystalline Diamond: Dual Optical and Field‐Effect Sensor for Membrane Disruption

Ang

Loh

Wohland

et al. 2008

Adv Funct Materials

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It is demonstrated that a good biomimetic model lipid membrane with dynamic fluidity can be established on optically transparent nanocrystalline diamond (OTND) with surface roughness below 10 nm. Maigainin II, an antimicrobial peptide, is chosen to investigate the permeation of artificial bacterial membranes constructed on OTND. Due to the unique combination of optical transparency and highly sensitive surface conducting channel, intrinsic OTND affords the possibility of dual‐mode sensing based on optical and field effect properties. This opens up new possibilities for making integrated biomolecule–semiconductor microdevices, or sensors where the binding of biomolecules can be tracked using confocal microscopy whilst the associated changes in charge density during membrane perforation can be tracked using the space charge effect in the semiconductor. Such a synergistic approach may provide a powerful methodology for the screening of specific bactericidal activity on biomimetic membrane systems.

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“…The total time taken up by aHL·CB6 events during a given period divided by the time during which the pore is unoccupied by either CB6 or CB6·THF (the fractional occupancy) is proportional to [CB6], which is the concentration of free CB6 in solution. [11] When [12] Assuming that the frequency of occurrence of the CB6·THF binding events is proportional to [CB6·THF] t , the time dependence of the appearance of the events, after the addition of THF, was used to obtain t obs at different THF concentrations in 2.0 m NaCl (Figure 4). A plot The slow dissociation rate constant corresponds to a mean residence time for THF in the CB6 cavity of over 100 s compared to a mean residence time of 35 ms for the CB6·THF complex in the aHL pore, which is consistent with a carrier rather than an adapter mechanism.…”

mentioning

confidence: 99%

Carriers versus Adapters in Stochastic Sensing

Braha

Webb

et al. 2005

ChemPhysChem

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Sensors based on analyte-dependent changes in the conduction of transmembrane protein pores are an interesting prospect. Stochastic sensing, that is, the detection of individual analyte molecules by single pores, has several potential advantages and a variety of sensor elements based on engineered forms of staphylococcal a-hemolysin (aHL) has been tested. [1] In one manifestation of this approach, organic molecules have been detected by using molecular adapters, such as cyclodextrins, which continue to engage in dynamic host-guest interactions after they have become lodged within the lumen of the aHL pore.[2] Here, we show that small organic molecules can also be detected by a scheme in which a host, cucurbit[6]uril (CB6), [3] acts as a carrier rather than an adapter. In this case, the rate of exchange of the guest between the host·guest complex and bulk solvent is slower [4] than the rate of exchange of the host between the solvent and its binding site within the aHL pore. Besides providing a useful means for sensing organic molecules, the carrier system allows the determination of dissociation constants and, independently, association and dissociation rate constants for CB6·guest pairs.CB6 ( Figure 1) contains a hydrophobic cavity, % 5.5 in diameter, which can host small neutral organic molecules.[3] Six carbonyl groups are located at each of the two 4--diameter entrances to the cavity. CB6 is sparingly soluble in water, but its solubility increases in the presence of alkali-metal salts because the carbonyl groups coordinate to the metal cations to form positively charged complexes. [5,6] An X-ray structure of CB6, which was crystallized from an aqueous solution containing Na + ions, shows two sodium ions and their coordinated water molecules at each entrance. [5,6] By contrast, when CB6 is crystallized in the presence of Cs + , only one cesium ion is associated with each entrance.[6] The dimensions of CB6 (maximum external diameter % 14.4 ) suggested that it might become lodged in the lumen of the aHL pore (Figure 1), similar to b-cyclodextrin (diameter % 15.5 ), and mediate the detection of analytes through host-guest interactions.The interaction of CB6 with the aHL pore was first examined in the absence of analyte by monitoring the current through a single pore in a planar bilayer apparatus, as described previously. [7] At + 100 mV in 1.0 m CsCl/10 mm K phosphate buffer (pH 7.4), the current measured through a fully open aHL pore (level L1) was 93.3 AE 1.2 pA (n = 7), and the current with CB6 bound from the trans side (level L2, aHL·CB6) was 41.7 AE 1.5 pA (n = 7) (Figure 2). Binding events were not detected when CB6 was applied to the cis side of the bilayer. The mean interevent intervals (t on ) and the mean durations of the binding events (t off ) were determined from dwell-time histograms.[8]The value of 1/t on increased linearly with [CB6], where [CB6] is the concentration of the cucurbituril, which suggests a simple bimolecular interaction (Scheme 1).[8] The rate constants for association and dissociat...

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Simultaneous stochastic sensing of divalent metal ions

Cited by 293 publications

References 15 publications

Current research activity in biosensors

Current research activity in biosensors

Supported Lipid Bilayer on Nanocrystalline Diamond: Dual Optical and Field‐Effect Sensor for Membrane Disruption

Carriers versus Adapters in Stochastic Sensing

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