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181.
182.
Catherine Bonaïti-Pellié Françoise Clerget-Darpoux Marie-Claude Babron 《Human genetics》1990,86(2):203-208
Summary Although the retinoblastoma gene has been isolated and sequenced, the difference in penetrance and expressivity among families has not yet been fully explained. Balanced chromosomal insertion involving the 13q14 regions has been shown to account for some families with several unaffected carriers. Since there could be cases with karyotypically undetectable insertions, we tested whether this mechanism was general enough to explain the whole difference in expressivity among families. Using 166 pedigrees, reported in nine series available in the literature (including our own), we conclude that balanced insertion cannot entirely explain the familial data, even if we allow for a reduced viability of unbalanced gametes. Other mechanisms are proposed and discussed in this paper. 相似文献
183.
Long-term assessments of species assemblages are valuable tools for detecting species ecological preferences and their dispersal
tracks, as well as for assessing the possible effects of alien species on native communities. Here we report a 50-year-long
study on population dynamics of the four species of land flatworms (Platyhelminthes, Tricladida, Terricola) that have colonized
or become extinct in a 70-year-old Atlantic Forest regrowth remnant through the period 1955–2006. On the one hand, the two
initially most abundant species, which are native to the study site, Notogynaphallia
ernesti and Geoplana multicolor have declined over decades and at present do not exist in the forest remnant. The extinction of these species is most likely
related with their preference for open vegetation areas, which presently do not exist in the forest remnant. On the other
hand, the neotropical Geoplaninae 1 and the exotic Endeavouria septemlineata were detected in the forest only very recently. The long-term study allowed us to conclude that Geoplaninae 1 was introduced
into the study area, although it is only known from the study site. Endeavouria septemlineata, an active predator of the exotic giant African snail, is originally known from Hawaii. This land flatworm species was observed
repeatedly in Brazilian anthropogenic areas, and this is the first report of the species in relatively well preserved native
forest, which may be evidence of an ongoing adaptive process. Monitoring of its geographic spread and its ecological role
would be a good practice for preventing potential damaging effects, since it also feeds on native mollusk fauna, as we observed
in lab conditions.
Júlio Pedroni: Granted by CNPQ–Brazil. 相似文献
184.
The structure of B-helical C-G-A-T-C-G-A-T-C-G and comparison with C-C-A-A-C-G-T-T-G-G. The effect of base pair reversals 总被引:5,自引:0,他引:5
K Grzeskowiak K Yanagi G G Privé R E Dickerson 《The Journal of biological chemistry》1991,266(14):8861-8883
The crystal structure of the DNA decamer C-G-A-T-C-G-A-T-C-G has been solved to a resolution of 1.5 A, with a final R-factor of 16.1% for 5,107 two-sigma reflections. Crystals are orthorhombic space group P2(1)2(1)2(1), with cell dimensions a = 38.93 A, b = 39.63 A, c = 33.30 A, and 10 base pairs/asymmetric unit. The final structure contains 404 DNA atoms, 142 water molecules treated as oxygen atoms, and two Mg(H2O)6(2+) complexes. Decamers stack atop one another to simulate continuous helical columns through the crystal, as with three previously solved monoclinic decamers, but the lateral contacts between columns are quite different in the orthorhombic and monoclinic cells. Narrow and wide regions of the minor groove exhibit a single spine or two ribbons of hydration, respectively, and the minor groove is widest when BII phosphate conformations are opposed diagonally across the groove. Phosphate conformation, in turn, appears to have a base sequence dependence. Twist, rise, cup, and roll are linked as has been observed in the three monoclinic decamers and can be characterized by high or low twist profiles. In all five known decamer crystal structures and eight representative dodecamers, a high twist profile is observed with G-C and G-A steps whereas all other R-R steps are low twist profiles (R = purine). A-T and A-C steps are intermediate in character whereas C-A and C-G exhibit behavior that is strongly influenced by the profiles of the preceding and following steps. When sufficient data are in hand, sequence/structure relationships for all helix parameters probably should be considered in a 4-base pair context. At this stage of limited information the problem is compounded because there are 136 unique 4-base steps x-A-B-y in a double helix as compared with only 10 2-base steps A-B. 相似文献
185.
Synthesis of cyclic peptides on solid support. Application to analogs of hemagglutinin of influenza virus 总被引:1,自引:0,他引:1
S Plaué 《International journal of peptide and protein research》1990,35(6):510-517
In order to mimic a well-known loop structure (site A) of the hemagglutinin of influenza virus, a series of cyclic peptides derived from the region 139-147 were synthesized. The lactam analogs cyclised between the N-terminus Cys 139 and the beta-carboxyl of aspartic acid 148 (small loop) or the epsilon-NH2 of lysine 148 via succinimidyl linker (large loop) were synthesized by the solid phase method. Cyclisation was directly performed on the solid support prior to final cleavage of the peptide. We describe two protection schemes which allow us to obtain different loop sizes derived from the same sequence. Eight of the analogs contained relatively large ring structures (up to 38 membered). For protection of the side chain of aspartic acid in combination with N-alpha-Fmoc protection, the cyclohexyl ester was more satisfactory than the benzyl ester with respect to imide formation. When the rate of cyclodimerisation, as a function of resin substitution, was compared to the rate of cyclic monomer formation, it was found that dimerisation was proportional to the charge of the resin. Furthermore, a comparison of the recently reported BOP reagent over the classical DIPC/HOBt method for the cyclisation reaction shows that in our case the reaction proceeded more rapidly by the BOP procedure although it gave a less pure crude product. 相似文献
186.
Performances of four ELISA kits in the detection of BLV antibodies in bulk tank milk was studied in 76 non-infected herds and 44 herds with low prevalence of BLV infection. None of the kits gave false positive results. On the other hand, there was an important variation in sensitivity. The kits with the highest sensitivity identified 43% of infected herds, which included 65% of infected cows. When concentrated lactoserum was tested, 59% of infected herds, which included 73% of infected cows, could be identified. 相似文献
187.
188.
Jean L. Santos Paulo R. Yamasaki Chung Man Chin Célio H. Takashi Fernando R. Pavan Clarice Q.F. Leite 《Bioorganic & medicinal chemistry》2009,17(11):3795-3799
New phthalimide derivatives were easily prepared through condensation of phthalic anhydride and selected amines with variable yields (70–90%). All compounds (3a–l) were evaluated against Mycobacterium tuberculosis H37Rv using Alamar Blue susceptibility. The compounds 3c, 3i, and 3l have the minimum inhibitory concentrations (MICs) of 3.9, 7.8, and 5.0 μg/mL, respectively, and could be considered new lead compounds in the treatment of tuberculosis and multi-drug resistant tuberculosis. 相似文献
189.
Three different fluorochrome and specific counterstain combination (DAPI/AMD, DA/DAPI and CMA/DA) treatments were applied to the chromosomes of four Microtidae (Rodentia) species. The results complete the data obtained in our previous paper (Burgos, M., Jiménez, R., & Dìaz de la Guardia, R., Genome 30:540–546, 1988) and prove that the changes in the constitutive heterochromatin in the evolution of the karyotypes of these species are not only due to gain or loss of heterochromatin, but are qualitative with respect to their nucleotide composition, repeated base pair organization or DNA-protein complex modification. These variations lead to the differential response to the fluorescence dye combinations used. 相似文献
190.
Conformational energies for the N-acetyl-N'-methylamides of the 20 natural amino acids were calculated, including the solvent effects, as functions of the angles phi and psi for rotation of the main chain and for six positions chi 1 of the C alpha-C beta bond in the side chain (fixed values for chi 2, chi 3, ...). The computed energies were used to evaluate the mean-square end-to-end distance and mean-square dipole moment of homopolypeptides of the 20 natural amino acids. Ten proteins and three enzymes of current interest were also studied. Slight differences in both properties are found on taking the effects of solvent into consideration. Comparison with other computational and experimental results is made. 相似文献