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931.
Melanocytes are potential immunocompetent cells: evidence from recognition of immunological characteristics of cultured human melanocytes 总被引:5,自引:0,他引:5
932.
933.
Recursive SVM feature selection and sample classification for mass-spectrometry and microarray data 总被引:3,自引:0,他引:3
Xuegong Zhang Xin Lu Qian Shi Xiu-qin Xu Hon-chiu E Leung Lyndsay N Harris James D Iglehart Alexander Miron Jun S Liu Wing H Wong 《BMC bioinformatics》2006,7(1):197-13
Background
Like microarray-based investigations, high-throughput proteomics techniques require machine learning algorithms to identify biomarkers that are informative for biological classification problems. Feature selection and classification algorithms need to be robust to noise and outliers in the data. 相似文献934.
A single-crystal of SmCl3·C5H10O5·5H2O was obtained from methanol-water solution and its structure determined by X-ray. Two forms of the complex as a pair of anomers and related conformers were found in the single-crystal in a disordered state. One ligand is α-d-ribopyranose in the 4C1 conformation and the other one is β-d-ribopyranose. The anomeric ratio is 1:1. Both ligands provide three hydroxyl groups in ax-eq-ax orientation for coordination. The Sm3+ ion is nine-coordinated with five Sm-O bonds from water molecules, three Sm-O bonds from hydroxyl groups of the d-ribopyranose and one Sm-Cl bond. The hydroxyl groups, water molecules and chloride ions form an extensive hydrogen-bond network. The IR spectral C-C, O-H, C-O, and C-O-H vibrations were observed to be shifted in the complex and the IR results are in accord with those of X-ray diffraction. 相似文献
935.
936.
Cellular genomes suffer extensive damage from exogenous agents and reactive oxygen species formed during normal metabolism.
The MutT homologs (MutT/MTH) remove oxidized nucleotide precursors so that they cannot be incorporated into DNA during replication.
Among many repair pathways, the base excision repair (BER) pathway is the most important cellular protection mechanism responding
to oxidative DNA damage. The 8-oxoG glycosylases (Fpg or MutM/OGG) and the MutY homologs (MutY/MYH) glycosylases along with
MutT/MTH protect cells from the mutagenic effects of 8-oxoG, the most stable and deleterious product known caused by oxidative
damage to DNA. The key enzymes in the BER process are DNA glycosylases, which remove different damaged bases by cleavage of
the N-glycosylic bonds between the bases and the deoxyribose moieties of the nucleotide residues. Biochemical and structural studies
have demonstrated the substrate recognition and reaction mechanism of BER enzymes. Cocrystal structures of strated the substrate
recognition and reaction mechanism of BER enzymes. Cocrystal structures of several glycosylases show that the substrate base
flips out of the sharply bent DNA helix and the minor groove is widened to be accessed by the glycosylases. To complete the
repair after glycosylase action, the apurinic/apyrimidinic (AP) site is further processed by an incision step, DNA synthesis,
an excision step, and DNA ligation through two alternative pathways. The short-patch BER (1-nucleotide patch size) and long-patch
BER (2–6-nucleotide patch size) pathways need AP endonuclease to generate a 3′ hydroxyl group but require different sets of
enzymes for DNA synthesis and ligation. Protein-protein interactions have been reported among the enzymes involved in BER.
It is possible that the successive players in the repair pathway are assembled in a complex to perform concerted actions.
The BER pathways are proposed to protect cells and organisms from mutagenesis and carcinogenesis. 相似文献
937.
Ohmura K Kawamoto H Lu M Ikawa T Ozaki S Nakao K Katsura Y 《Journal of immunology (Baltimore, Md. : 1950)》2001,166(5):3290-3296
Previous studies indicated that multipotent progenitors exist in early fetuses that do not contain long-term reconstituting (LTR) activity. However, it remained unclear whether these multipotent progenitors are committed to the hemopoietic lineage or are immature mesodermal cells or hemangioblasts. In this study, we have succeeded in enriching the multipotent progenitors that are capable of generating myeloid, T, and B cells in the LFA-1(-) subpopulation of TER-119(-)c-kit(+)CD45(+) cells from the aorta-gonad-mesonephros (AGM) region of day 10 fetuses. We found that these day 10 AGM LFA-1(-) cells do not show the LTR activity, whereas day 11 AGM LFA-1(-) cells do have such an activity. These results strongly suggest that multipotent progenitors lacking LTR activity emerge as CD45(+) hemopoietic progenitor cells in the AGM region on the 10th day of gestation, and such p-Multi mature into hemopoietic stem cells by acquiring LTR activity. 相似文献
938.
By use of pulse radiolysis techniques, the radical cations of purine nucleotides have been successfully produced by the SO4- ion oxidation. Time-resolved spectroscopic evidence is provided that the one-electron-oxidized radicals of dAMP and dGMP can be efficiently repaired by aromatic amino acids (including tyrosine and tryptophan) via electron transfer reaction. As a model peptide, Arg-Tyr-AcOH was also investigated with regard to its interaction with deprotonated purine radical cations. The rate constants of the electron transfer reactions were determined to be (1 approximately 5) x 10(8) dm(3) mol(-1) s(-1). These results suggest that the aromatic amino acids in DNA-associated proteins may play some role in electron transfer reactions through DNA. 相似文献
939.
Dendroctonus valens is an invasive pest in coniferous forests of northern China. It was suspected of being responsible for the death of more
than three million Pinus tabuliformis trees. The present study sought to identify the ophiostomatoid fungi associated with D. valens in northern China and understand the possible role of these fungi in the pine decline. On the basis of morphology, physiology,
mating compatibility and phylogenetic analyses of multiple DNA sequences, seven species of ophiostomatoid fungi were isolated
from and around D. valens galleries: Leptographium alethinum, Grosmannia koreana (teleomorph of L. koreanum), L. procerum, L. sinoprocerum, L. truncatum, Pesotum aureum and P. pini. All have been recorded for the first time in China. Among them, the occurrence of the dominant species L. procerum is positively linked to attack intensities of D. valens. The pathogenicity of four species (L. koreanum, L. procerum, L. sinoprocerum and L. truncatum) was tested on mature P. tabuliformis trees by stem inoculation. All inoculated strains caused significant necrotic lesions on the inner bark. However, L. koreanum and L. truncatum induced more extensive lesions than L. procerum and L. sinoprocerum. Their association with D. valens and the P. tabuliformis decline is discussed. 相似文献
940.
E S Imasheva M Lu S P Balashov T G Ebrey Y Chen Z Ablonczy D R Menick R K Crouch 《Biochemistry》2001,40(44):13320-13330
Tyrosine-83, a residue which is conserved in all halobacterial retinal proteins, is located at the extracellular side in helix C of bacteriorhodopsin. Structural studies indicate that its hydroxyl group is hydrogen bonded to Trp189 and possibly to Glu194, a residue which is part of the proton release complex (PRC) in bacteriorhodopsin. To elucidate the role of Tyr83 in proton transport, we studied the Y83F and Y83N mutants. The Y83F mutation causes an 11 nm blue shift of the absorption spectrum and decreases the size of the absorption changes seen upon dark adaptation. The light-induced fast proton release, which accompanies formation of the M intermediate, is observed only at pH above 7 in Y83F. The pK(a) of the PRC in M is elevated in Y83F to about 7.3 (compared to 5.8 in WT). The rate of the recovery of the initial state (the rate of the O --> BR transition) and light-induced proton release at pH below 7 is very slow in Y83F (ca. 30 ms at pH 6). The amount of the O intermediate is decreased in Y83F despite the longer lifetime of O. The Y83N mutant shows a similar phenotype in respect to proton release. As in Y83F, the recovery of the initial state is slowed several fold in Y83N. The O intermediate is not seen in this mutant. The data indicate that the PRC is functional in Y83F and Y83N but its pK(a) in M is increased by about 1.5 pK units compared to the WT. This suggests that Tyr83 is not the main source for the proton released upon M formation in the WT; however, Tyr83 is involved in the proton release affecting the pK(a) of the PRC in M and the rate of proton transport from Asp85 to PRC during the O --> bR transition. Both the Y83F and the Y83N mutations lead to a greatly decreased functionality of the pigment at high pH because most of the pigment is converted into the inactive P480 species, with a pK(a) 8-9. 相似文献