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221.
222.
A new lignan for which the name seco-isolariciresinol is proposed, has been isolated from the heartwood of Podocarpus spicatus. The structure has been shown to be 2:3-bis(4′-hydroxy-3′- methoxybenzyl)-butan-1:4-diol (II, R = H), and confirmed by an absolute synthesis from (−)-matairesinol (I, R = H). A further examination of the extractives of the heartwood has resulted in the isolation of the minor constituents, (+)-taxifolin, (+)-aromadendrin, kaempferol and sequoyitol, in addition to the previously reported compounds, matairesinol, -conidendrin, quercetin, genistein and podospicatin. 相似文献
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225.
H. Thoms Marks Neidle Jacob Barab A. Golodetz T. B. Briggs G. Stanley Walpole William Brown B. Hömberg C. Brahm und H. Mühsam 《Fresenius' Journal of Analytical Chemistry》1919,58(8):356-358
Ohne Zusammenfassung 相似文献
226.
J. Kevelam J. B. F. N. Engberts M. J. Blandamer B. Briggs P. M. Cullis 《Colloid and polymer science》1998,276(2):190-194
Differential scanning microcalorimetric thermograms have been recorded for aqueous solutions containing vesicles formed by
sodium di-n-dodecyl phosphate, in the presence of different concentrations of poly(sodium acrylate-co-n-alkyl methacrylate), where n-alkyl= C9H19, C12H25, C18H37. The mole fraction of hydrophobic moieties in the copolymer is 0.04. The main phase transition temperature (T
m) is hardly affected by the presence of poly(sodium acrylate)s bearing n-dodecyl chains, whereas the anchoring of polymers bearing n-nonyl or n-octadecyl groups reduces the main phase transition temperature significantly from ca. 34 °C to ca. 32 °C. In parallel, the
enthalpy of transition per mole of DDP monomer (Δm
H
int) is lowered upon adding polymer. Again, the polymer containing n-dodecyl moieties hardly affects Δm
H
int. These patterns are explained by the notion that the extent of the disruptive effect of alkyl chains incorporated into the
bilayer depends on the extent of the mismatch between the chain lengths of the intruding alkyl chains and the hydrophobic
moieties composing the vesicle bilayer. Added hydrophobically modified polymers increase the cooperativity of the melting
process, as shown by the increase of n
DDP. We suggest that the anchoring poly(sodium acrylate-co-n-alkyl methacrylate) relieves the strain in the curved outer monolayer of a pure DDP bilayer by allowing the presence of larger
“patches” characterized by low curvature.
Received: 12 May 1997 Accepted: 20 October 1997 相似文献
227.
[structure: see text]. Crystal structures of the cis-bis[60]fullerene adduct of 6,13-diphenylpentacene (with the closest carbon atoms on adjacent fullerenes only 3.065(8) angstroms apart) and the [60]fullerene-pentacene monoadduct are in remarkably close agreement with the MM2 calculated structures. 相似文献
228.
229.
Absolute cross sections for double-electron transfer in H(-) + H(+) collisions have been measured for center-of-mass energies from 0.5 to 12 keV. Clear oscillations in the cross section are observed shedding new light on earlier measurements. Calculations based on a diabatic approach are shown to reproduce this behavior, but require a larger diabatic ion-pair splitting than previously assumed. 相似文献
230.
Efficient 3D database screening for novel HIV-1 IN inhibitors 总被引:2,自引:0,他引:2
Barreca ML Rao A De Luca L Zappalà M Gurnari C Monforte P De Clercq E Van Maele B Debyser Z Witvrouw M Briggs JM Chimirri A 《Journal of chemical information and computer sciences》2004,44(4):1450-1455
We describe the use of pharmacophore modeling as an efficient tool in the discovery of novel HIV-1 integrase (IN) inhibitors. A three-dimensional hypothetical model for the binding of diketo acid analogues to the enzyme was built by means of the Catalyst program. Using these models as a query for virtual screening, we found several compounds that contain the specified 3D patterns of chemical functions. Biological testing shows that our strategy was successful in searching for new structural leads as HIV-1 IN inhibitors. 相似文献