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41.
42.
Relative apparent synapomorphy analysis (RASA). I: The statistical measurement of phylogenetic signal 总被引:1,自引:9,他引:1
We have developed a new approach to the measurement of phylogenetic signal
in character state matrices called relative apparent synapomorphy analysis
(RASA). RASA provides a deterministic, statistical measure of natural
cladistic hierarchy (phylogenetic signal) in character state matrices. The
method works by determining whether a measure of the rate of increase of
cladistic similarity among pairs of taxa as a function of phenetic
similarity is greater than a null equiprobable rate of increase. Our
investigation of the utility and limitations of RASA using simulated and
bacteriophage T7 data sets indicates that the method has numerous
advantages over existing measures of signal. A first advantage is
computational efficiency. A second advantage is that RASA employs known
methods of statistical inference, providing measurable sensitivity and
power. The performance of RASA is examined under various conditions of
branching evolution as the number of characters, character states per
character, and mutations per branch length are varied. RASA appears to
provide an unbiased and reliable measure of phylogenetic signal, and the
general approach promises to be useful in the development of new techniques
that should increase the rigor and reliability of phylogenetic estimates.
相似文献
43.
44.
Abstract In recent months, there has been a wealth of promising clinical data suggesting that a more effective treatment regimen, and potentially a cure, for hepatitis C virus (HCV) infection is close at hand. Leading this push are direct-acting antivirals (DAAs), currently comprising inhibitors that target the HCV protease NS3, the viral polymerase NS5B, and the non-structural protein NS5A. In combination with one another, along with the traditional standard-of-care ribavirin and PEGylated-IFNα, these compounds have proven to afford tremendous efficacy to treatment-naíve patients, as well as to prior non-responders. Nevertheless, by targeting viral components, the possibility of selecting for breakthrough and treatment-resistant virus strains remains a concern. Host-targeting antivirals are a distinct class of anti-HCV compounds that is emerging as a complementary set of tools to combat the disease. Cyclophilin (Cyp) inhibitors are one such group in this category. In contrast to DAAs, Cyp inhibitors target a host protein, CypA, and have also demonstrated remarkable antiviral efficiency in clinical trials, without the generation of viral escape mutants. This review serves to summarize the current literature on Cyps and their relation to the HCV viral life cycle, as well as other viruses. 相似文献
45.
Evidence that factor VIII and the ristocetin aggregating factor (VIIIRist) are separate molecular entities 总被引:2,自引:0,他引:2
46.
Cells of Tetrahymena pyriformis, strain GL, induced to divide synchronously by alternating 30 min periods at 34 ° and 28 °C, exhibited an increased rate of phospholipid synthesis during the initial stage of cytokinesis. This sharp peak of biosynthesis was evident from labeling studies with either 32P-orthophosphate or 14C-acetate. However, the period of enhanced lipid synthesis could be dissociated from cytokinesis by altering incubation conditions and was apparently associated more closely with recovery from the heat shocks than with the division process. Cells synchronized by a different procedure involving a single 30 min heat shock per generation showed no peak of labeling with 32Pi but retained the peak when tested with 14C-acetate. It appears that this latter perturbation was triggered by cytokinesis. 相似文献
47.
Polyglutamyl derivatives of tetrahydrofolate as substrates for Lactobacillus casei thymidylate synthase 总被引:1,自引:0,他引:1
Tetrahydropteroylpolyglutamates containing up to seven Glu residues were tested as substrates for Lactobacillus casei thymidylate synthase. The Km values decreased from 24 microM for the monoglutamate to 1.8 microM for the triglutamate. Addition of residues 4, 5, 6, and 7 did not decrease the Km further. When monoglutamate and polyglutamate substrates were simultaneously incubated with the enzyme, the rate observed was characteristic of the polyglutamate even when the monoglutamate concentration was 44 times that of the polyglutamate. Iodoacetamide treatment inhibited the enzyme to the same extent with monoglutamate and polyglutamate substrates. Addition of 0.3 M NaCl doubled the rate obtained with the polyglutamate substrate whereas the rate with the monoglutamate was inhibited 25%. MgCl2 stimulated the reaction only 10% with the polyglutamate substrate compared with 80% stimulation obtained with the monoglutamate. Inhibition by fluorodeoxyuridylate was similar with both mono- and polyglutamate substrates; however, with the phosphonate derivative of fluorodeoxyuridine, the polyglutamate substrate enhanced inhibition 5- to 8-fold. 相似文献
48.
Polygammaglutamyl metabolites of methotrexate 总被引:8,自引:0,他引:8
C M Baugh C L Krumdieck M G Nair 《Biochemical and biophysical research communications》1973,52(1):27-34
Heretofore unrecognized metabolites of methotrexate (MTX) have been detected in human red blood cells and isolated from rat liver and viscera. The metabolites from the rat were identified as 2,4-diamino-N10-methylpteroylglutamyl-γ-glutamic acid [MTX(G1)] and 2,4-diamino-N10-methylpteroylglutamyl-γ-glutamyl-γ-glutamic acid [MTX(G2)] by comparison with authentic synthetic compounds. 相似文献
49.
Expression of exogenous protein in the egg white of transgenic chickens 总被引:14,自引:0,他引:14
Using a replication-deficient retroviral vector based on the avian leukosis virus (ALV), we inserted into the chicken genome a transgene encoding a secreted protein, beta-lactamase, under the control of the ubiquitous cytomegalovirus (CMV) promoter. Biologically active beta-lactamase was secreted into the serum and egg white of four generations of transgenic chickens. The expression levels were similar in successive generations, and expression levels in the magnum of the oviduct were constant over at least 16 months in transgenic hens, indicating that the transgene was stable and not subject to silencing. These results support the potential of the hen as a bioreactor for the production of commercially valuable, biologically active proteins in egg white. 相似文献
50.
Niels H Chavannes Juanita HJ Vernooy Tjard RJ Schermer Jan A Jacobs Mieke A Dentener Chris van Weel Onno CP van Schayck Emiel FM Wouters 《BMC pulmonary medicine》2006,6(1):1-7