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Nielsen J; Peixoto AA; Piccin A; Costa R; Kyriacou CP; Chalmers D 《Molecular biology and evolution》1994,11(6):839-853
The region of the clock gene period (per) that encodes a repetitive tract
of threonine-glycine (Thr-Gly) pairs has been compared between Dipteran
species both within and outside the Drosophilidae. All the non-
Drosophilidae sequences in this region are short and present a remarkably
stable picture compared to the Drosophilidae, in which the region is much
larger and extremely variable, both in size and composition. The
accelerated evolution in the repetitive region of the Drosophilidae appears
to be mainly due to an expansion of two ancestral repeats, one encoding a
Thr-Gly dipeptide and the other a pentapeptide rich in serine, glycine, and
asparagine or threonine. In some drosophilids the expansion involves a
duplication of the pentapeptide sequence, but in Drosophila pseudoobscura
both the dipeptide and the pentapeptide repeats are present in larger
numbers. In the nondrosophilids, however, the pentapeptide sequence is
represented by one copy and the dipeptide by two copies. These observations
fulfill some of the predictions of recent theoretical models that have
simulated the evolution of repetitive sequences.
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Sprays of captafol, carbendazim, carbendazim + tridemorph + maneb, diclobutrazol, triadimefon or triadimefon + carbendazim all completely protected barley plants in a glasshouse against R. secalis for at least 30 days. However, their effectiveness in preventing disease development when applied after inoculation differed: triadimefon, traidimefon + carbendazim, or diclobutrazol were the most effective, completely preventing symptom development when applied up to 5 days after inoculation to plants grown above 16 °C, and up to 8 days below 8 °C. All the fungicides decreased the number of viable conidia produced by leaf blotch lesions, and when applied to infected plants at G. S. 30, greatly decreased the upward spread of the disease under simulated rain conditions; the most effective fungicides in these respects were triadimefon and triadimefon + carbendazim. The above fungicides and fungicide mixtures, together with the recently introduced materials fenpropimorph and propiconazole were applied to diseased winter barley crops in winter or in spring. All treatments decreased leaf blotch development and increased yields. In most cases, a winter application was more effective than spring applications, particularly if applied in mid-November. The most effective fungicides were triadimefon and propiconazole. The field trials data fitted well with the predictions of performance indicated by the glasshouse investigations. 相似文献
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Melanin isolated from the ink sac of Sepia officinalis (Sepia melanin) has been proposed as a standard for natural eumelanin. There are no standard methods for the isolation, purification, and storage of melanins. Mild methods designed to preserve the native composition and structure of melanin are needed. The specific aim of the present work, using Sepia melanin, was to develop a mild and generally applicable protocol for the isolation and purification of melanins. It is well established that melanin polymers contain a large number of free carboxylic acid residues. These anionic residues are responsible for the cation exchange properties observed for melanins. Heating melanins with hydrochloric acid at reflux has been demonstrated to lead to extensive decarboxylation. Indeed, heat alone has been shown to cause decarboxylation, and care must be exercised to avoid such conditions. By analogy with cation exchange resins, melanins should be isolated and named according to the associated counterion (e.g., Sepia melanin—K+ form). The method reported here avoided extremes in pH and temperature, and was designed to yield melanin in the K+ form. Physical disaggregation of particulate melanin using a wet milling step was also found to facilitate removal of significant quantities of adsorbed protein. The following physical parameters were used to monitor the purification and to characterize the resultant melanin: pH, conductance, particle size, and diffuse reflectance spectroscopy. 相似文献
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New durophagous arthrodires from Gogo, Western Australia 总被引:1,自引:0,他引:1
Three new monotypic genera of eubrachythorarid arthrodires with crushing toothplates are described from the Upper Devonian Gogo Formation of Western Australia as Bruntonichthys multidens gen. et sp. nov., Bullerichthysfascidens gen. et sp. nov. and Kendrickkhthys cavemosus gen. et sp. nov. Their structure and relationships are discussed within the framework provided by a sketch cladogram. All three are interchangeable with Coccosteus spp. but their phylogenetic relationships are not known in any detail. However, Kendrickkhthys does appear to be immediately related to Dinomylostoma from North America. 相似文献
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