Kinetic Studies of Molecular Recognition Based on Hydrogen Bonding at the Air−Water Interface by Using a Highly Sensitive Quartz-Crystal Microbalance

Abstract

The complementary guest binding process onto the cyanurate lipid 1 monolayer at the air-water interface was observed by using a highly sensitive 27 MHz quartz-crystal microbalance (QCM), which was attached horizontally on the monolayer from the air phase. Binding amount (∆m), association constants (Ka), as well as binding and dissociation rate constants (k1 and k-1) could be obtained from time courses of the frequency decrease (mass increase) of the QCM. A highly sensitive 27 MHz QCM was used to detect small mass changes of Langmuir adsorption of small guest molecules instead of our conventional 9 MHz QCM. Guests such as 2,4,6-triaminopyrimidine (A) possessing three complementary hydrogen bonding sites were selectively bound to the monolayer 1 showing a 1:2 host-guest binding ratio, k 1 ) 2.8 M -1 s -1 , k-1 ) 7.2 × 10 -4 s -1 , and Ka ) 3900 M -1 . The Ka value was consistent with that obtained by NMR spectra in bulk CDCl3. Guest molecules of A hardly bound to monolayers 2-4 with -NH2, -CONH2, and -OH head groups. Binding constants of guest molecules to the monolayer 1 were of the following order: 2,4,6triaminopyrimidine (A) > 2,6-diaminopyridine (B) possessing three hydrogen bonds > 2-aminopyridine (C) forming two hydrogen bonds > pyridine (D) with only one hydrogen bond ≈ barbituric acid (E) having no complementary hydrogen binding sites. The obtained binding kinetics at the water interface were compared with molecular mechanics calculations of binding energy in vacuum.

Identification of Target Domains of the Cardiac Ryanodine Receptor to Correct Channel Disorder in Failing Hearts

“…23,24 The QCM Au electrode was coated with K201 and immersed in a solution (500 L) containing (in mmol/L) 150 NaCl, 20 MOPS (pH 7.4). The amount of drug binding was determined from the frequency changes due to changes in mass on the electrode (with sensitivity on the order of subnanogram) on injection of a small volume (2 to 5 L) of solution containing RyR2 fragments (30 nmol/L).…”

Dynamic Analyses on Induced-Fit Gaseous Guest Binding to Organic Crystals with a Quartz-Crystal Microbalance

“…A QCM has been widely used with various sensing systems, [26±31] and we have already shown its validity for the detection of molecular interactions, for example, molecular adsorption to cast films in gas [32] and aqueous [33] phases, in-situ characterization of Langmuir ± Blodgett films, [34] DNA hybridization, [35] DNA ± protein interactions, [36] and molecular recognition at the air ± water interface. [37] Recently, we combined a QCM technique and a flow cell to detect the molecular recognition of gaseous guests on a functionalized monolayer. [38] In this paper, we report the dynamic studies of gaseous guest binding to the apohost crystals immobilized on a QCM (see Figure 1).…”

Study of adsorption of methylene blue and new methylene blue in liquid?solid interface by slab optical waveguide spectroscopy

“…Binding energy analysis has been used for molecular recognition study [32] and study of interaction between Nafion film and organic gas [33]. The structure of both bare SOWG and ODS-SOWG can be simply represented in (I) and (II), respectively (Fig.…”

“…In general cases, however, SOWG-dye complex would not be 1:1, but here the interactions for various dye molecules are compared for 1:1 complex in relative scale. According to reference [32], the binding energy (DetE) is defined as the difference between the most stable energy of E SOWG-dye complex and the sum of the most stable energies of E SOWG and E dye ,…”