background: marginal seal has a principal role in durability and clinical success offissure sealants. the aim of this study was to compare the microleakage of two materials used as pit and fissure sealant with different methods of application. methods: the 55 extracted premolars were assigned randomly to one ofthe following five groups: group 1: acid-etching (ultra-etch) + fissure sealant (conv...

Formation of C–H H–B dihydrogen bonded complexes of acetylene, fluoroacetylene, chloroacetylene, and cyanoacetylene with borane-trimethylamine were investigated with MP2 and B3LYP methods using 6-311++G(d,p) and aug-cc-pVDZ basis sets. The stabilization energies ranged from 6–20 kJ mol . NBO analysis predicts transfer of charge from r B–H bonding orbital to r* C–H anti-bonding orbital. It was a...

To give a deeper insight into the widely discussed catalytic mechanism of biotin, four representative model molecules and their aggregates hydrogen bonding (H-bonding) to water molecules were investigated by means of ab initio calculations and compared with molecular dynamics simulations. The roles of the ureido group, the sulfur atom, and the side chain of biotin are examined and discussed, re...

The effect of hydrogen bonding on the amide group vibrational spectra has traditionally been rationalized by invoking a resonance model where hydrogen bonding impacts the amide functional group by stabilizing its [(-)O-C=NH (+)] structure over the [O=C-NH] structure. However, Triggs and Valentini's UV-Raman study of solvation and hydrogen bonding effects on epsilon-caprolactum, N, N-dimethylace...