Gas Phase Molecular Recognition on Nucleobase Monolayers Immobilized on a Highly Sensitive Quartz-Crystal Microbalance¹

Abstract

Complementary molecular recognition in the gas phase onto self-assembled monolayers bearing thymine or adenine bases as terminal groups was studied by using a highly sensitive 63 MHz quartz-crystal microbalance. Association constants (K a), binding and dissociation rate constants (k 1 and k - 1), and binding amount in nanogram level (Δm) could be obtained from time coarses of frequency decrease (mass increase) at various gaseous guest concentrations. Kinetic parameters were corrected to avoid the effect of different adsorption ability of guest molecules. Binding of 2-aminopyridine (an adenine model) onto a thymine monolayer showed the 50−100 times larger binding constant than that of a noncomplementary guest molecule, γ-butyrolactam. On the other hand, an adenine monolayer preferentially bound the thymine model of γ-butyrolactam over 2-aminopyridine, the adenine model. When a simple hydrocarbon monolayer of 1-decanethiol was used, all of these guest molecules were hardly bound. The selectivity between complementary and noncomplementary nucleobase pairs observed in the gas/thin film surface was comparable to the selectivity seen in organic solvents. The formation energy of hydrogen bonding obtained from K a values in the gas/thin film surface was consistent with that calculated by molecular mechanics as in a vacuum. K a values of the guest molecules were dependent on the nucleobase content in the mixed monolayer of nucleobase and alkyl chains.

Cation recognition by self-assembled monolayers of oriented helical peptides having a crown ether unit

“…The SAMs, which are composed of compounds having a functional group, are interesting especially in the application fields of biomaterials, 2,3 and microelectronics. 4,5 When the functional group recognizes a specific molecule, the modified gold will be used as an electrode for a chemical sensing device. 6 The molecular recognition process can be detected sensibly by IR spectroscopy, 3 quartz crystal microbalance (QCM), 4,5 surface plasmon resonance (SPR), 6 and electrochemical measurements.…”

Adsorption of gaseous molecule within polyfluorinated surfactant/saponite hybrid compound

“…Since the large gas solubility in perfluoroalkane is mainly ascribable to an incorporation of larger amount of gaseous molecules within the larger intermolecular space among perfluoroalkane molecules than that of ordinary hydrocarbon solution, a gas adsorption into the interlayer of the hybrid compound would promisingly afford crucial information which reflects the microscopic structure of the surfactants, the microenvironment surrounding the short perfluoroalkyl chains, and the micro-cavity formed by the surfactants and the nano-layered saponite. In this paper, we will report on adsorption behavior of gaseous molecules such as water vapor, nitrogen, hydrogen, oxygen, and ethylene into the interlayer of C3F-S/saponite hybrid compound by means of quartz crystal microbalance [12][13][14][15][16][17][18].…”

Effect of salt on the hybridization of DNA by sequential immobilization of oligonucleotides at the air-water interface in the presence of ODA/DOTAP monolayers

“…Much attention has been paid recently to the effects of buffer and ionic strengths upon the binding of DNA with cationic lipids, since these complexes can serve as efficient agents for transfection of eukaryotic cells [8][9][10]. Different routes have been employed for the immobilization of DNA on planar supports, such as assembly at air-water interfaces with Langmuir monolayers [11][12][13][14], self-assembly of thiolated DNA and PNA (peptide nucleic acids) on gold surfaces [15,16], and self-assembly process onto quartz crystal oscillators [17,18]. Some other methods include attachment to terminally functionalized self-assembled monolayers (SAMs) via electrostatic [19] and intercalation interactions [20].The air-water interface has proven to be an excellent medium for the organization of large inorganic ions [21][22][23], colloidal nanoparticles [24][25][26][27], and biomacromolecules such as proteins and enzymes [28][29][30] and in the growth of oriented crystals [31,32].…”