Nanomechanical Recognition ofN-Methylammonium Salts

Abstract

Turning molecular recognition into an effective mechanical response is critical for many applications ranging from molecular motors and responsive materials to sensors. Herein, we demonstrate how the energy of the molecular recognition between a supramolecular host and small alkylammonium salts can be harnessed to perform a nanomechanical task in a univocal way. Nanomechanical Si microcantilevers (MCs) functionalized by a film of tetra-phosphonate cavitands were employed to screen as guests the compounds of the butylammonium chloride series 1-4, which comprises a range of low molecular weight (LMW) molecules (molecular mass< 150 Da) that differ from each other by one or a few N-methyl groups (molecular mass 15 Da). The cavitand surface recognition of each individual guest drove a specific MC bending (from a few to several tens of nanometer), disclosing a direct, label-free, and real-time mean to sort them. The complexation preferences of tetraphosphonate cavitands toward ammonium chloride guests 1-4 were independently assessed by isothermal titration calorimetry. Both direct and displacement binding experiments concurred to define the following binding order in the alkylammonium series: 2 > 3 ≈ 1 ≫ 4. This trend is consistent with the number of interactions established by each guest with the host. The complementary ITC experiments showed that the host-guest complexation affinity in solution is transferred to the MC bending. These findings were benchmarked by implementing cavitand-functionalized MCs to discriminate sarcosine from glycine in water.

Cavitand-Functionalized SWCNTs for N-Methylammonium Detection

“…The measurements were performed at pH 5 to ensure protonation of the amine. As controls, the weaker binding glycine ethyl ester hydrochloride ( 5 ) and tetraethylammonium chloride ( 6 ) that is too bulky for binding, 9 were chosen.…”

Investigation of Ph-Assisted Human Serum Albumin (HSA)-Cobalt (Co)Binding Using Nanomechanical Deflection and Circular Dichroism

“…However, upon binding to Co(II) we see a shift in [θ] values, indicates there may be change in other secondary structures present in the protein. The conformational change in solution is different than on a solid surface, however recently Bergese et al and Shrotiya et al have compared the binding of host-guest molecules using isothermal titration calorimeter (ITC) measurements in solution and on microcantilever surface that matched fairly well [59,60]. Similarly, if we relate the solution work with the conformational change upon binding of CoCl 2 to the microcantilever surface it shows various similarities.…”

Micro- and nano-structure based oligonucleotide sensors

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