Ecdysteroids of quinoa seeds (Chenopodium quinoa Willd.)     

Zhu N  Kikuzaki H  Vastano BC  Nakatani N  Karwe MV  Rosen RT  Ho CT 《Journal of agricultural and food chemistry》2001,49(5):2576-2578

Quinoa (Chenopodium quinoa) is a hardy and nutritious Latin American pseudo-cereal. Studies on the seeds led to the isolation of five ecdysteroids using column chromatography. Their structures were determined as ecdysterone, makisterone A, 24-epi-makisterone A, 24(28)-dehydromakisterone A, and 20,26-dihydroxyecdysone by spectroscopic methods. This study demonstrates that quinoa seeds are a source of ecdysteroids, which were reported to be molting hormones in insects.  相似文献   

Ballistic 2-d imaging through scattering walls using an ultrafast optical kerr gate     

Wang L  Ho PP  Liu C  Zhang G  Alfano RR 《Science (New York, N.Y.)》1991,253(5021):769-771

An ultrafast optical shutter was used to image ultrasmall objects hidden behind scattering walls by a procedure that selects in time the ballistic component and rejects the scattered diffusive light. Scattering walls used in this experiment included human breast tissue, chicken breast tissue, and a water suspension of polystyrene particles with scattering coefficients up to 21.7. Submillimeter resolution was achieved for two-dimensional ballistic images of a single point, a double-point fluorescence source, and a bar test chart in or behind these different turbid media.  相似文献   

Functional interaction and partial homology between human immunodeficiency virus and neuroleukin   总被引：8，自引：0，他引：8  

M R Lee  D D Ho  M E Gurney 《Science (New York, N.Y.)》1987,237(4818):1047-1051

Dementia is common in patients with AIDS, but the mechanism by which the human immunodeficiency virus type 1 (HIV-1) causes the neurological impairment is unknown. In this study the possibility that an antigen of HIV-1 suppresses neuronal responses to neurotrophic factors was examined. Both HIV-1 and a related retrovirus, simian immunodeficiency virus (SIV), inhibited the growth of sensory neurons from chick dorsal root ganglia in medium containing neuroleukin (NLK) but not in medium containing nerve growth factor. An unrelated type D retrovirus, simian acquired immunodeficiency syndrome virus, did not affect the growth of neurons in the presence of either neurotrophic factor. The inhibition by HIV-1 of neuron growth in the presence of NLK was found to be due to the gp120 envelope glycoprotein. Regions of sequence homology between gp120 and NLK may account for this inhibitory property of gp120 and functional interactions between gp120 and NLK may be important in the pathogenesis of the AIDS dementia complex.  相似文献   

Single-bond formation and characterization with a scanning tunneling microscope     

Lee HJ  Ho W 《Science (New York, N.Y.)》1999,286(5445):1719-1722

A scanning tunneling microscope (STM) was used to manipulate the bonding of a carbon monoxide (CO) molecule and to analyze the structure and vibrational properties of individual products. Individual iron (Fe) atoms were evaporated and coadsorbed with CO molecules on a silver (110) surface at 13 kelvin. A CO molecule was transferred from the surface to the STM tip and bonded with an Fe atom to form Fe(CO). A second CO molecule was similarly transferred and bonded with Fe(CO) to form Fe(CO)(2). Controlled bond formation and characterization at the single-bond level probe chemistry at the spatial limit.  相似文献   

Electrical resistance of long conjugated molecular wires     

Ho Choi S  Kim B  Frisbie CD 《Science (New York, N.Y.)》2008,320(5882):1482-1486

The charge transport mechanism of a wire can be revealed by how its electrical resistance varies with length. We have measured the resistance and current-voltage characteristics of conjugated molecular wires ranging in length from 1 to 7 nanometers, connected between metal electrodes. We observe the theoretically predicted change in direct-current transport from tunneling to hopping as a function of systematically controlled wire length. We also demonstrate that site-specific disruption of conjugation in the wires greatly increases resistance in the hopping regime but has only a small effect in the tunneling regime. These nanoscale transport measurements elucidate the role of molecular length and bond architecture on molecular conductivity and open opportunities for greater understanding of electrical transport in conjugated polymer films.  相似文献   

PHYSICS. Arrival of the fermion superfluid     

Ho TL 《Science (New York, N.Y.)》2004,305(5687):1114-1115

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Narcotic tolerance and dependence and serotonin turnover     

R J Hitzemann  I K Ho  H H Loh 《Science (New York, N.Y.)》1972,178(61):645-647

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Midbody targeting of the ESCRT machinery by a noncanonical coiled coil in CEP55   总被引：1，自引：0，他引：1  

Lee HH  Elia N  Ghirlando R  Lippincott-Schwartz J  Hurley JH 《Science (New York, N.Y.)》2008,322(5901):576-580

The ESCRT (endosomal sorting complex required for transport) machinery is required for the scission of membrane necks in processes including the budding of HIV-1 and cytokinesis. An essential step in cytokinesis is recruitment of the ESCRT-I complex and the ESCRT-associated protein ALIX to the midbody (the structure that tethers two daughter cells) by the protein CEP55. Biochemical experiments show that peptides from ALIX and the ESCRT-I subunit TSG101 compete for binding to the ESCRT and ALIX-binding region (EABR) of CEP55. We solved the crystal structure of EABR bound to an ALIX peptide at a resolution of 2.0 angstroms. The structure shows that EABR forms an aberrant dimeric parallel coiled coil. Bulky and charged residues at the interface of the two central heptad repeats create asymmetry and a single binding site for an ALIX or TSG101 peptide. Both ALIX and ESCRT-I are required for cytokinesis, which suggests that multiple CEP55 dimers are required for function.  相似文献   

Retraction of an interpretation     

Zhang L  Lopez P  He T  Yu W  Ho DD 《Science (New York, N.Y.)》2004,303(5657):467

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A magnetic nanoprobe technology for detecting molecular interactions in live cells     

Won J  Kim M  Yi YW  Kim YH  Jung N  Kim TK 《Science (New York, N.Y.)》2005,309(5731):121-125

Technologies to assess the molecular targets of biomolecules in living cells are lacking. We have developed a technology called magnetism-based interaction capture (MAGIC) that identifies molecular targets on the basis of induced movement of superparamagnetic nanoparticles inside living cells. Efficient intracellular uptake of superparamagnetic nanoparticles (coated with a small molecule of interest) was mediated by a transducible fusogenic peptide. These nanoprobes captured the small molecule's labeled target protein and were translocated in a direction specified by the magnetic field. Use of MAGIC in genome-wide expression screening identified multiple protein targets of a drug. MAGIC was also used to monitor signal-dependent modification and multiple interactions of proteins.  相似文献