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61.
Jayne E Rattray Marc Strous Huub JM Op den Camp Stefan Schouten Mike SM Jetten Jaap S Sinninghe Damsté 《Biology direct》2009,4(1):8-16
Background
The fatty acids of anaerobic ammonium oxidizing (anammox) bacteria contain linearly concatenated cyclobutane moieties, so far unique to biology. These moieties are under high ring strain and are synthesised by a presently unknown biosynthetic pathway. 相似文献62.
Background
Analysis of heart rate variation (HRV) has become a popular noninvasive tool for assessing the activities of the autonomic nervous system (ANS). HRV analysis is based on the concept that fast fluctuations may specifically reflect changes of sympathetic and vagal activity. It shows that the structure generating the signal is not simply linear, but also involves nonlinear contributions. These signals are essentially non-stationary; may contain indicators of current disease, or even warnings about impending diseases. The indicators may be present at all times or may occur at random in the time scale. However, to study and pinpoint abnormalities in voluminous data collected over several hours is strenuous and time consuming. 相似文献63.
Evolution of transposable elements: an IS10 insertion increases fitness in Escherichia coli 总被引:3,自引:0,他引:3
Strains of Escherichia coli carrying Tn10, a transposon consisting of two
IS10 insertion sequences flanking a segment encoding for a
tetracycline-resistance determinant, gain a competitive advantage in
chemostat cultures. All Tn10-bearing strains that increase in frequency
during competition have a new IS10 insertion that is found in the same
location in the genome of those strains. We mapped, by a gradient of
transmission, the position of the new IS10 insertion. We examined 11
isolates whose IS10 insertion was deleted by recombinational crossing-
over, and in all cases the competitive fitness of the isolates was
decreased. These results show that the IS10-generated insertion increases
fitness in chemostat cultures. We named the insertion fit::IS10 and suggest
that transposable elements may speed the rate of evolution by promoting
nonhomologous recombination between preexisting variations within a genome
and thereby generating adaptive variation.
相似文献
64.
Members of the ZFY and ZNF6 gene families have been cloned from species
representing different taxa and different modes of sex determination.
Comparisons of these genes show the ZFY-like and ZNF6 sequences to be
strongly conserved across marsupials, birds, and lepidosaurians. Sequence
analyzed by neighbor-joining indicated that both gene families are
monophyletic with a high bootstrap value. Pairing of sequences from males
and females of nonmammalian species showed there to be no significant
difference between male and female sequences from a single species,
consistent with autosomal locations. The molecular distances between murine
Zfy-1, Zfy-2, and other ZFY-like sequences suggested that Zfy genes have
undergone a period of rapid evolutionary change not seen in human ZFY.
相似文献
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Ribosomal proteins L7/L12 localized at a single region of the large subunit by immune electron microscopy. 总被引:6,自引:0,他引:6
Ribosomal proteins have been mapped by immune electron microscopy. These multiple copy proteins are located at a single region extending from the large subunit, known as the stalk. The stalk is approximately 100 Å long, about 40 Å wide and extends at an angle of approximately 50 ° from one side of the central protuberance of the large subunit. In the monomeric 70 S ribosome, the portion of the stalk proximal to the 50 S subunit is located in the vicinity of the 30 S-50 S interface.Anti- antibody binding to the stalk was shown to be solely dependent upon the presence of by the following experiments. Sucrose gradient analysis was used to demonstrate that large subunits depleted of were unable to bind anti- antibodies and that re-incorporation of restored the ability of -depleted cores to react with anti- antibodies. Anti- antibodies pre-absorbed with did not react with 50 S subunits.Anti- antibodies used in these experiments reacted only with the stalk and with no other region of the subunit. This was shown by electron microscopy and by immune electron microscopy in the following ways. Electron microscopy of 50 S subunits, -depleted 50 S cores, and reconstituted 50 S subunits was used to demonstrate that stripping removes the stalk from more than 95% of the subunits, and that re-incorporation of into depleted cores restores the stalk. Double-labelling experiments, using monomeric subunits with two or more attached anti- immunoglobulins, were used to demonstrate, independently of 50 S subunit morphology, that are located only on the stalk. 相似文献
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