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    ABSTRACT: This review is the third update of the original review, published in 1999, on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings the topic to the end of 2004. Both fundamental studies and applications are covered. The main topics include methodological developments, matrices, fragmentation of carbohydrates and applications to large polymeric carbohydrates from plants, glycans from glycoproteins and those from various glycolipids. Other topics include the use of MALDI MS to study enzymes related to carbohydrate biosynthesis and degradation, its use in industrial processes, particularly biopharmaceuticals and its use to monitor products of chemical synthesis where glycodendrimers and carbohydrate-protein complexes are highlighted.
    Mass Spectrometry Reviews 04/2014; 28(2):273-361. DOI:10.1002/mas.20192
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    ABSTRACT: Complement Factor H (FH) is an abundant, non-enzymic plasma/serum glycoprotein, which has a major role in regulating activation of the complement system. It can be purified from human plasma/serum by affinity chromatography, using a monoclonal anti-FH antibody as ligand. Other affinity chromatography ligands, including cardiolipin and trinitrophenyl-bovine serum albumin (TNP-BSA), can be used to purify human FH and also FH from a wide range of vertebrates, including mammals, birds, bony fish. Human FH protein concentration can be quantified by sandwich ELISA. The activity of FH is generally measured by assays which detect the cleavage, by complement factor I, of the complement protein C3b to form iC3b. Cleavage occurs only in the presence of a cofactor, and FH is one of a small number of cofactors for this reaction.
    Methods in molecular biology (Clifton, N.J.) 01/2014; 1100:207-23. DOI:10.1007/978-1-62703-724-2_17
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    ABSTRACT: Mammalian cells make the proliferation or quiescence decision at a specific point in the cell cycle called the restriction point, after which they become committed to proliferation and independent of growth factors for completion of mitosis. In the textbook view, this crucial transition occurs several hours after mitotic division (in the middle of G1 phase). In a Cell paper, Spencer et al. show that the restriction point should be defined not as a particular time point in G1 phase but in terms of the ON-OFF status of a bistable switch that emerges from the positive feedback in the CDK2-RB-E2F (cyclin-dependent kinase 2-retinoblastoma-E2F) interaction network.
    Science Signaling 12/2013; 6(305):pe37. DOI:10.1126/scisignal.2004891
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    ABSTRACT: We report an unusual case of a patient with two combined X-linked diseases, severe hemophilia A (HA) and Duchenne muscular dystrophy (DMD), of which only HA was hereditary. There was no family history of muscular dystrophy. Genetic analysis revealed that HA was caused by the hereditary coagulation factor VIII (F8) intron 22 inversion (distal/type I inversion), whereas DMD was caused by a de novo deletion in the dystrophin gene. This is the first report of a patient with two severe X-linked diseases, of which only HA was hereditary. Despite the fact that the probability of acquiring two X-linked abnormalities, one hereditary and one de novo, is extremely low, the emergence of such cases indicates that genetic testing for distinct X-linked diseases could be of importance in patients with hereditary hemophilia.
    International journal of hematology 12/2013; DOI:10.1007/s12185-013-1488-4
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    ABSTRACT: Water-mediated bond formation: The structure of the peptide GPG-NH2 has been investigated in aqueous solution to understand the role of water in the formation of a β-turn. Using a combination of neutron diffraction enhanced by isotopic substitution, NMR spectroscopy, and computer simulations, it was found that water is an essential component to initiate folding in solution.
    Angewandte Chemie International Edition 12/2013; 125(49). DOI:10.1002/anie.201307657
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    ABSTRACT: Radiation damage is a major cause of failure in macromolecular crystallography experiments. Although it is always best to evenly illuminate the entire volume of a homogeneously diffracting crystal, limitations of the available equipment and imperfections in the sample often require a more sophisticated targeting strategy, involving microbeams smaller than the crystal, and translations of the crystal during data collection. This leads to a highly inhomogeneous distribution of absorbed X-rays (i.e., dose). Under these common experimental conditions, the relationship between dose and time is nonlinear, making it difficult to design an experimental strategy that optimizes the radiation damage lifetime of the crystal, or to assign appropriate dose values to an experiment. We present, and experimentally validate, a predictive metric diffraction-weighted dose for modeling the rate of decay of total diffracted intensity from protein crystals in macromolecular crystallography, and hence we can now assign appropriate "dose" values to modern experimental setups. Further, by taking the ratio of total elastic scattering to diffraction-weighted dose, we show that it is possible to directly compare potential data-collection strategies to optimize the diffraction for a given level of damage under specific experimental conditions. As an example of the applicability of this method, we demonstrate that by offsetting the rotation axis from the beam axis by 1.25 times the full-width half maximum of the beam, it is possible to significantly extend the dose lifetime of the crystal, leading to a higher number of diffracted photons, better statistics, and lower overall radiation damage.
    Proceedings of the National Academy of Sciences 12/2013; 110(51). DOI:10.1073/pnas.1315879110
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    ABSTRACT: Although current textbook explanations of cell-cycle control in eukaryotes emphasize the periodic activation of cyclin-dependent protein kinases (CDKs), recent experimental observations suggest a significant role for the periodic activation and inactivation of a CDK-counteracting protein phosphatase 2A with a B55δ subunit (PP2A:B55δ), during mitotic cycles in frog-egg extracts and early embryos. In this paper, we extend an earlier mathematical model of embryonic cell cycles to include experimentally motivated roles for PP2A:B55δ and its regulation by Greatwall kinase. Our model is consistent with what is already known about the regulation of CDK and PP2A:B55δ in frog eggs, and it suggests a previously undescribed role for the Greatwall-PP2A:B55δ interaction in creating a toggle switch for activation of the anaphase-promoting complex as embryonic cells exit mitosis and return to interphase.
    Proceedings of the National Academy of Sciences 12/2013; 110(51). DOI:10.1073/pnas.1318065110
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    ABSTRACT: Centromere proteins CENP-S and CENP-X are members of the constitutive centromere-associated network, which is a conserved group of proteins that are needed for the assembly and function of kinetochores at centromeres. Intriguingly CENP-S and CENP-X have alter egos going by the names of MHF1 (FANCM-associated histone-fold protein 1) and MHF2 respectively. In this guise they function with a DNA translocase called FANCM (Fanconi's anemia complementation group M) to promote DNA repair and homologous recombination. In the present review we discuss current knowledge of the biological roles of CENP-S and CENP-X and how their dual existence may be a common feature of CCAN (constitutive centromere-associated network) proteins.
    Biochemical Society Transactions 12/2013; 41(6):1726-1730. DOI:10.1042/BST20130200
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    ABSTRACT: Eukaryotic mRNAs are extensively processed to generate functional transcripts, which are 5' capped, spliced and 3' polyadenylated. Accumulation of unprocessed (aberrant) mRNAs can be deleterious for the cell, hence processing fidelity is closely monitored by QC (quality control) mechanisms that identify erroneous transcripts and initiate their selective removal. Nucleases including Xrn2/Rat1 and the nuclear exosome have been shown to play an important role in the turnover of aberrant mRNAs. Recently, with the growing appreciation that mRNA processing occurs concomitantly with polII (RNA polymerase II) transcription, it has become evident that QC acts at the transcriptional level in addition to degrading aberrant RNAs. In the present review, we discuss mechanisms that allow cells to co-transcriptionally initiate the removal of RNAs as well as down-regulate transcription of transcripts where processing repeatedly fails.
    Biochemical Society Transactions 12/2013; 41(6):1666-1672. DOI:10.1042/BST20130202
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    ABSTRACT: Since the dissolution of sister chromatid cohesion by separase and cyclin B destruction is irreversible, it is essential to delay both until all chromosomes have bioriented on the mitotic spindle. Kinetochores that are not correctly attached to the spindle generate the mitotic checkpoint complex (MCC), which inhibits the anaphase-promoting complex/cyclosome (APC/C) and blocks anaphase onset. This process is known as the spindle assembly checkpoint (SAC) [1]. The SAC is especially important in meiosis I, where bivalents consisting of homologous chromosomes held together by chiasmata biorient. Since the first meiotic division is unaffected by rare achiasmatic chromosomes or misaligned bivalents [2-7], it is thought that several tensionless kinetochores are required to produce sufficient MCC for APC/C inhibition. Consistent with this, univalents lacking chiasmata elicit a SAC-mediated arrest in Mlh1(-/-) oocytes. In contrast, chromatids generated by TEV protease-induced cohesin cleavage in Rec8(TEV/TEV) oocytes merely delay APC/C activation. Since the arrest of Mlh1(-/-)Rec8(TEV/TEV) oocytes is alleviated by TEV protease, even when targeted to kinetochores, we conclude that their SAC depends on cohesin as well as dedicated kinetochore proteins. This has important implications for aging oocytes [8, 9], where cohesin deterioration will induce sister kinetochore biorientation and compromise MCC production, leading to chromosome missegregation and aneuploid fetuses.
    Current biology: CB 11/2013; 23(24). DOI:10.1016/j.cub.2013.10.052
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