20 research outputs found
Chromatographic Properties of Different Methyl—Phenyl (1:1) Substituted Silicone Stationary Phases for Open-Tubular Gas Chromatography
The influence of different configurations of silicones having 50% methyl and 50% phenyl substitution on chromatographic properties, such as polarity and thermal stability, has been systematically investigated. Polysiloxanes composed of dimethyl and diphenyl units show very low levels of column bleed at temperatures up to 370°C, while polymers having methyl—phenyl substitution show severe bleeding at this temperature. The polarity of the latter polymers, as reflected by Kováts indices, is higher than for the polymers composed by dimethyl—diphenyl unit
Functional characterization of a melon alcohol acyl-transferase gene family involved in the biosynthesis of ester volatiles. Identification of the crucial role of a threonine residue for enzyme activity
Volatile esters, a major class of compounds contributing to the aroma of many fruit, are synthesized by
alcohol acyl-transferases (AAT). We demonstrate here that, in Charentais melon (Cucumis melo var.
cantalupensis), AAT are encoded by a gene family of at least four members with amino acid identity ranging
from 84% (Cm-AAT1/Cm-AAT2) and 58% (Cm-AAT1/Cm-AAT3) to only 22% (Cm-AAT1/Cm-AAT4).
All encoded proteins, except Cm-AAT2, were enzymatically active upon expression in yeast and show
differential substrate preferences. Cm-AAT1 protein produces a wide range of short and long-chain acyl
esters but has strong preference for the formation of E-2-hexenyl acetate and hexyl hexanoate. Cm-AAT3
also accepts a wide range of substrates but with very strong preference for producing benzyl acetate.
Cm-AAT4 is almost exclusively devoted to the formation of acetates, with strong preference for cinnamoyl
acetate. Site directed mutagenesis demonstrated that the failure of Cm-AAT2 to produce volatile esters is
related to the presence of a 268-alanine residue instead of threonine as in all active AAT proteins. Mutating
268-A into 268-T of Cm-AAT2 restored enzyme activity, while mutating 268-T into 268-A abolished
activity of Cm-AAT1. Activities of all three proteins measured with the prefered substrates sharply increase
during fruit ripening. The expression of all Cm-AAT genes is up-regulated during ripening and inhibited in
antisense ACC oxidase melons and in fruit treated with the ethylene antagonist 1-methylcyclopropene
(1-MCP), indicating a positive regulation by ethylene. The data presented in this work suggest that the
multiplicity of AAT genes accounts for the great diversity of esters formed in melon
Enfuvirtide, an HIV-1 Fusion Inhibitor, for Drug-Resistant HIV Infection in North and South America
Background: The T-20 vs. Optimized Regimen Only Study 1 (TORO 1) was a randomized, open-label,
phase 3 study of enfuvirtide (T-20), a human immunodeficiency virus type 1 (HIV-1)
fusion inhibitor.
Methods: Patients from 48 sites in the United States, Canada, Mexico, and Brazil with at least six
months of previous treatment with agents in three classes of antiretroviral drugs, resistance
to drugs in these classes, or both, and with at least 5000 copies of HIV-1 RNA
per milliliter of plasma were randomly assigned in a 2:1 ratio to receive enfuvirtide plus
an optimized background regimen of three to five antiretroviral drugs or such a regimen
alone (control group). The primary efficacy end point was the change in the plasma
HIV-1 RNA level from base line to week 24.
Results: A total of 501 patients underwent randomization, and 491 received at least one dose of
study drug and had at least one measurement of plasma HIV-1 RNA after treatment
began. The two groups were balanced in terms of the median base-line HIV-1 RNA
level (5.2 log10 copies per milliliter in both groups), median CD4+ cell count (75.5
cells per cubic millimeter in the enfuvirtide group, and 87.0 cells per cubic millimeter
in the control group), demographic characteristics, and previous antiretroviral therapy.
At 24 weeks, the least-squares mean change from base line in the viral load (intention-
to-treat, last observation carried forward) was a decrease of 1.696 log10 copies
per milliliter in the enfuvirtide group, and a decrease of 0.764 log10 copies per milliliter
in the control group (P<0.001). The mean increases in CD4+ cell count were 76
cells per cubic millimeter and 32 cells per cubic millimeter, respectively (P<0.001).
Reactions at the site of the injections were reported by 98 percent of patients receiving
enfuvirtide. There were more cases of pneumonia in the enfuvirtide group than in the
control group.
Conclusions: The addition of enfuvirtide to an optimized antiretroviral regimen provided significant
antiretroviral and immunologic benefit through 24 weeks in patients who had previously
received multiple antiretroviral drugs and had multidrug-resistant HIV-1 infection
Continental lithospheric mantle origin of 2.5 Ga old Monchegorsk layered intrusion from the Fennoscandian shield
International audienc
A technique for the cultivation and preparation of tissue cultures for electron microscopy
A geological synthesis of the Precambrian shield in Madagascar
International audiencevailable U-Pb geochronology of the Precambrian shield of Madagascar is summarized and integrated into a synthesis of the region's geological history. The shield is described in terms of six geodynamic domains, from northeast to southwest, the Bemarivo, Antongil-Masora, Antananarivo, Ikalamavony, Androyan-Anosyan, and Vohibory domains. Each domain is defined by distinctive suites of metaigneous rocks and metasedimentary groups, and a unique history of Archean (similar to 2.5 Ga) and Proterozoic (similar to 1.0 Ga, similar to 0.80 Ga, and similar to 0.55 Ga) reworking. Superimposed within and across these domains are scores of Neoproterozoic granitic stocks and batholiths as well as kilometer long zones of steeply dipping, highly strained rocks that record the effects of Gondwana's amalgamation and shortening in latest Neoproterozoic time (0.560-0.520 Ga).The present-day shield of Madagascar is best viewed as part of the Greater Dharwar Craton, of Archean age, to which three exotic terranes were added in Proterozoic time. The domains in Madagascar representing the Greater Dharwar Craton include the Antongil-Masora domain, a fragment of the Western Dharwar of India, and the Neoarchean Antananarivo domain (with its Tsaratanana Complex) which is broadly analogous to the Eastern Dharwar of India. In its reconstructed position, the Greater Dharwar Craton consists of a central nucleus of Paleo-Mesoarchean age (>3.1 Ga), the combined Western Dharwar and Antongil-Masora domain, flanked by mostly juvenile "granite-greenstone belts" of Neoarchean age (2.70-2.56 Ga). The age of the accretionary event that formed this craton is approximately 2.5-2.45 Ga. The three domains in Madagascar exotic to the Greater Dharwar Craton are the Androyan-Anosyan, Vohibory, and Bemarivo. The basement to the Androyan-Anosyan domain is a continental terrane of Paleoproterozoic age (2.0-1.78 Ga) that was accreted to the southern margin (present-day direction) of the Greater Dharwar Craton in pre-Stratherian time (>1.6 Ga), and rejuvenated at 1.03-0.93 Ga with the creation of the Ikalamavony domain. The Vohibory domain, an oceanic terrane of Neoproterozoic age was accreted to the Androyan-Anosyan domain in Cryogenian time (similar to 0.63-0.60 Ga). The Bemarivo domain of north Madagascar is a terrane of Cryogenian igneous rocks, with a cryptic Paleoproterozoic basement, that was accreted to the Greater Dharwar Craton in latest Ediacaran to earliest Cambrian time (0.53-0.51 Ga)
Morphological and genomic assessment of divergence between closely related species of the genus Philaenus (Hemiptera, Aphrophoridae)
National audienc