Hofmeister Effect in Confined Spaces: Halogen Ions and Single Molecule Detection

Despite extensive research in the nanopore-sensing field, there is a paucity of experimental studies that investigate specific ion effects in confined spaces, such as in nanopores. Here, the effect of halogen anions on a simple bimolecular complexation reaction between monodisperse poly(ethylene gly...

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Bibliographic Details
Published in:Biophysical journal 2011-06, Vol.100 (12), p.2929-2935
Main Authors: Rodrigues, Claudio G., Machado, Dijanah C., da Silva, Annielle M.B., Júnior, Janilson J.S., Krasilnikov, Oleg V.
Format: Article
Language:English
Subjects:
Anions
Bacterial Toxins - metabolism
Biological
Biophysics - methods
Chemical reactions
Confined environments
Devices
Electric Conductivity
Electroosmosis
Enzymes
Halogens
Halogens - chemistry
Hemolysin Proteins - metabolism
Ions
Kinetics
Limit of Detection
Membrane
Models, Chemical
Molecular chemistry
Nanocomposites
Nanomaterials
Nanoparticles
Nanostructure
Physical chemistry
Polyethylene Glycols - chemistry
Solubility
Solutions
Water - chemistry
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Summary:Despite extensive research in the nanopore-sensing field, there is a paucity of experimental studies that investigate specific ion effects in confined spaces, such as in nanopores. Here, the effect of halogen anions on a simple bimolecular complexation reaction between monodisperse poly(ethylene glycol) (PEG) and α-hemolysin nanoscale pores have been investigated at the single-molecule level. The anions track the Hofmeister ranking according to their influence upon the on-rate constant. An inverse relationship was demonstrated for the off-rate and the solubility of PEG. The difference among anions spans several hundredfold. Halogen anions play a very significant role in the interaction of PEG with nanopores although, unlike K +, they do not bind to PEG. The specific effect appears dominated by a hydration-dehydration process where ions and PEG compete for water. Our findings provide what we believe to be novel insights into physicochemical mechanisms involved in single-molecule interactions with nanopores and are clearly relevant to more complicated chemical and biological processes involving a transient association of two or more molecules (e.g., reception, signal transduction, enzyme catalysis). It is anticipated that these findings will advance the development of devices with nanopore-based sensors for chemical and biological applications.
ISSN:0006-3495
1542-0086
DOI:10.1016/j.bpj.2011.05.003