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181.
Jaramillo Colorado BE Martelo IP Duarte E 《Journal of agricultural and food chemistry》2012,60(25):6364-6368
The chemical composition of essential oils isolated from aerial parts of Triphasia trifolia (Burm. f.) P. Wilson was analyzed using hydrodistillation by GC-MS. The main constituents found were β-pinene (64.36%), (+)-sabinene (8.75%), hexadecanoic acid (6.03%), α-limonene (4.24%) and p-cymene (2.73%). The essential oil from T. trifolia shows high antioxidant potential (94.53%), an effect that is comparable with ascorbic acid (96.40%), used as standard. In addition, these oils had high repellent effects on the insect Tribolium castaneum Herbst (99% ± 1) at 0.2 μL/cm(2) after 2 h of exposure. 相似文献
182.
183.
Abramson J Smirnova I Kasho V Verner G Kaback HR Iwata S 《Science (New York, N.Y.)》2003,301(5633):610-615
Membrane transport proteins that transduce free energy stored in electrochemical ion gradients into a concentration gradient are a major class of membrane proteins. We report the crystal structure at 3.5 angstroms of the Escherichia coli lactose permease, an intensively studied member of the major facilitator superfamily of transporters. The molecule is composed of N- and C-terminal domains, each with six transmembrane helices, symmetrically positioned within the permease. A large internal hydrophilic cavity open to the cytoplasmic side represents the inward-facing conformation of the transporter. The structure with a bound lactose homolog, beta-D-galactopyranosyl-1-thio-beta-D-galactopyranoside, reveals the sugar-binding site in the cavity, and residues that play major roles in substrate recognition and proton translocation are identified. We propose a possible mechanism for lactose/proton symport (co-transport) consistent with both the structure and a large body of experimental data. 相似文献