Browsing by Subject "Quantum Theory"

Now showing 1 - 3 of 3

Open Access
Application of the Ugi reaction with multiple amino acid-derived components: Synthesis and conformational evaluation of piperazine-based minimalist peptidomimetics
(Royal Society of Chemistry, 2015) Stucchi, M.; Cairati, S.; Cetin-Atalay, R.; Christodoulou, M.S.; Grazioso G.; Pescitelli G.; Silvani, A.; Yildirim, D.C.; Lesma G.
The concurrent employment of α-amino acid-derived chiral components such as aldehydes and α-isocyanoacetates, in a sequential Ugi reaction/cyclization two-step strategy, opens the door to the synthesis of three structurally distinct piperazine-based scaffolds, characterized by the presence of l-Ala and/or l-Phe-derived side chains and bearing appropriate functionalities to be easily applied in peptide chemistry. By means of computational studies, these scaffolds have been demonstrated to act as minimalist peptidomimetics, able to mimic a well defined range of peptide secondary structures and therefore potentially useful for the synthesis of small-molecule PPI modulators. Preliminary biological evaluation of two different resistant hepatocellular carcinoma cellular lines, for which differentiation versus resistance ability seem to be strongly correlated with well defined types of PPIs, has revealed a promising antiproliferative activity for selected compounds. © The Royal Society of Chemistry 2015.
Open Access
Effects of perfluorination on thiophene and pyrrole oligomers
(2010) Salzner, U.
The effect of perfluorination on thiophene and pyrrole oligomers in neutral, cationic, and anionic states was investigated with density functional theory at the (TD)B3P86-30%/6-31G* level. For the title compounds fluorination leads to planarization. For pyrroles a band gap reduction of 0.58 eV results, as unsubstituted pyrroles are nonplanar and disordered in the solid state. For thiophene the band gap is slightly increased as long thiophene oligomers are almost planar. Ionization energies and electron affinities increase upon fluorination by 0.65 and 0.60 eV for polythiophene and by 0.45 and 0.90 eV for polypyrrole. Conduction band widths increase by 0.5 for polythiophene and by 0.7 eV for polypyrrole. Spectra of charged (doped) forms are almost identical to those of the parent systems. Like parent systems, fluorinated oligomers with chain lengths of more than six rings develop a third UV absorption that increases in strength and decreases in energy upon chain length increase.
Open Access
Electronic structure of a Si delta-layer embedded in Ge(001)
(Institute of Physics Publishing, 1991) Gulseren, O.; Çıracı, Salim
Using the Green function formalism with layer orbitals we studied the electronic structure of a Si δ-layer in germanium. We found two-dimensional parabolic subbands near the band edges. This approach is extended to treat the electronic structure of a single quantum well without invoking the periodically repeating models.