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Open Chemistry
|
2006
|
tom 4
|
nr 4
732-742
EN
Supermolecular complexes formed by oligophenyleneethynylene derivatives and isophthalic acid were studied using AM1 method to obtain binding energy. Electronic spectra and IR spectra of the complexes were calculated by INDO/CIS and AM1 methods based on AM1 geometries. Results indicated that the dimer could be formed by the monomers via hydrogen bonding because of the negative binding energy. Binding energy of the complexes was affected by electronegativity and steric effects of the substituents. The first UV absorptions and IR frequencies of N-H bonds of the complexes were both red-shifted compared with those of the monomers. The complexes could bind small molecules via hydrogen bonds, resulting in the change in UV absorptions and an increase in IR frequencies of N-H bonds.
Open Chemistry
|
2006
|
tom 4
|
nr 2
223-233
EN
Equilibrium geometries and electronic structures of complexes between β-cyclodextrin (β-CD) and some small molecules as well as monosaccharides were investigated by Austin Model 1 (AM1) to obtain binding energy of the complexes. It was indicated that β-CD could bind the structurally similar solvent molecules and monosaccharides because of the negative binding energy of the complexes, and especially could show the chiral binding ability to monosaccharides with more hydroxyl groups, due to its chiral characteristics. The complexes were stabilized by the hydrogen bonding between β-CD and guests. Based on the AM1 optimized geometries, the IR spectra were calculated by AM1 method. Vibration frequencies of O-H bonds in the guests were red-shifted owing to the weakening of the O-H bonds with the formation of the complexes.
EN
By application of preparative high-speed counter-current chromatography (HSCCC) to the crude quinolone alkaloids (1.1 g) from the fruit of Tetradium ruticarpum, 1-methyl-2((6Z,9Z)-pentadecadienyl)-4(1H)-quinolone (1, 8.4 mg), dihydroevocarpine (2, 27.0 mg), and 1-methyl-2-pentadecyl-4(1H)-quinolone (3, 18.8 mg) were isolated in one step with sufficient purity using the solvent system composed of hexane–ethyl acetate–methanol–water (Hex–EtOAc–MeOH–H2O, 5:2:5:3). Further purification of the subfraction was performed by amending the solvent composition and achieved another three quinolone alkaloids, i.e., 1-methyl-2-undecylquinolin-4(1H)-one (4, 13.7 mg), (Z)-1-methyl-2-(tridec-5-en-1-yl) quinolin-4(1H)-one (5, 14.0 mg) from subfraction FR3-A3-85 using Hex–EtOAc–MeOH–H2O (5:3.5:8.75:8.25), and 1-methyl-2-nonylquinolin-4(1H)-one (6, 15.1 mg) from subfraction FR3-A3-36 using Hex–EtOAc–MeOH–H2O (5:3.8:5:4.8). The relationship between the structure of the six alkaloids and their affinities for bovine serum albumin (BSA) was investigated using fluorescence titration analysis. The length and the presence of double bond of the side chain affected their binding process with BSA. The binding behavior might influence their other biological activities.
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