The gas-phase recognition of native amino acids and the conformational properties of three glucosylthioureidocalix[4]arenes () were studied theoretically and experimentally using ab initio calculations, ESI-FTICR,(1)H and (13)C NMR MS. The conformational and complexation properties of the glucocalixarenes were dependent on the number of glucose units at the upper rim and the length of the alkyl chains at the lower rim of the calixarene skeleton. ESI-MS experiments showed the compounds to form 1 : 1 complexes with the amino acids, with a marked preference for amino acids containing an aromatic nucleus and an additional H-bonding group in their side chain (Trp, Tyr, Phe >> Ser, Leu and Asp). The experimental data were rationalized by the results of ab initio calculations. ESI-MS competitions carried out with enantiomeric-labelled (EL) amino acids showed enantiomeric selectivities ranging from 0.61 (Phe(D)/Phe(L) with ligand ) to 2.58 (Tyr(D)/Tyr(L) with ligand ). In gas-phase hydrogen-deuterium (H/D) exchange reactions, diglucosylcalix[4]arene exhibited extremely slow exchange rates, which were attributed to the close proximity and strong hydrogen bonding between the facing glucosylthioureido groups. H/D exchange rates were much higher for the tetraglucosylcalix[4]arenes and and their amino acid complexes, and the more rigid tetrapropoxy derivative showed more selective H/D exchange reactions than the calixarene . Bi- or trimodal H/D exchange distribution was observed for the tetraglucosyl derivatives indicating that these ligands exist in multiple isomeric forms in gas phase.

Ab initio methods were used to investigate the nanoscale friction between two graphite layers placed in contact. The interaction energies were calculated for four two-layer models in series, C(6(n+1))2H(6n+1))-C(6)(n)2H(6)(n) with n = 1, 2, 3, and 4, and additionally for C(54)H(18)-C(6)H(6) and C(150)H(30)-C(6)H(6). The study was done with the Hartree-Fock method using basis sets 3-21G and 6-31G and with the second-order Møller-Plesset theory using basis set 6-31G. A density functional method (B3PW91) was also tested for reference purposes. The main interest was how the model size and level of theory affect the nanoscale friction coefficient. Most of the calculated friction coefficients fell within the range of values of 0.07-0.14.

The noncovalent complexation of tetraethyl and tetraphenyl resorcinarenes with mono-, di-, and oligosaccharides was studied with negative-polarization electrospray ionization quadrupole ion trap and electrospray ionization Fourier-transform ion cyclotron resonance mass-spectrometric analysis. The saccharides formed 1:1 complexes with deprotonated resorcinarenes, which exhibited clear size and structure selectivity in their complexation. In the case of the monosaccharides, hexoses formed much more abundant and kinetically stable complexes than pentoses or deoxyhexoses. A comparison of the mono-, di-, and oligosaccharides revealed that both the relative abundance and stability of the complexes increase up to biose and triose, but start to decrease after that point, as the length of the oligosaccharide is increased. This behavior was rationalized by comparing the lowest-energy conformations of the complexes formed between the resorcinarene and oligosaccharides. This comparison was achieved by using theoretical calculations and X-ray crystal studies.

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