Model Ziegler-Natta α-Olefin Polymerization Catalysts Derived from [{(η^5-C_5Me_4)SiMe_2(η^1-NCMe_3)}(PMe_3)Sc(µ_2-H)]_2 and [{(η^5-C_5Me_4)SiMe_2(η^1-NCMe_3)}Sc(µ_2-CH_2CH_2CH_3)]_2. Synthesis, Structures, and Kinetic and Equilibrium Investigations of the Catalytically Active Species in Solution

The scandium hydride complex [(Cp*SiNR)(PMe_3)Sc(µ-H)]_2 (1), ((Cp*SiNR) = ((η^5-C_5Me_4)SiMe_2(η^1-NCMe_3)}) is prepared by hydrogenation of (Cp*SiNR)ScCH(SiMe_3)_2 in the presence of trimethylphosphine. The hydride complex is a catalyst precursor for the polymerization of α-olefins, yielding atactic products of low molecular weight (M, = 3000-7000). GC/MS analysis of volatile, oligomeric products revealed that all scandium centers are active during the polymerization. Selectivity for head-to-tail insertion is high (>99%) and for the tetramer, pentamer, and hexamer formed during propene polymerization, the maximum theoretical numbers of head-to-tail stereoisomers are observed by capillary GC. The stoichiometric reaction between 1 and 2 equiv of ethylene produces the unusual ethylene-bridged dimer [(Cp*SiNR)(PMe_3)Sc]_2(µ,η^2,η^2-C_2H_4) (2) and an equivalent of ethane, whereas the same reaction with propene affords the phosphine-free, alkyl-bridged scandium dimer [(Cp*S~NR)Sc]_2(µ-CH_2CH_2CH_3)_2 (3). The absence of coordinating phosphine allows the latter complex to function as a more active olefin polymerization catalyst precursor. 1 reacts with styrene to form a unique double-insertion product arising from sequential 1,2- and 2,1-styrene insertion. The structure of the catalytic intermediate in solution was determined by low-temperature ^(13)C-NMR studies of the model complexes (Cp*SiNR)(P(^(13)CH_3)_3]ScCH_2CH(CH_3)CHCH_2CH_2CH_3 and (Cp*SiNR)(PMe_3)Sc^(13)CH_2CHCH(^(13)CH_3)_2. One phosphine-bound species is observed in equilibrium with only one phosphine-free species. The symmetry properties of the latter indicate that it is a monomeric, hence 12-electron, scandium alkyl complex. Semiquantitative treatment of equilibrium concentration data supports this conclusion

Model Ziegler-Natta α-Olefin Polymerization Catalysts Derived from [{(η^5-C_5Me_4)SiMe_2(η^1-NCMe_3)}(PMe_3)Sc(µ_2-H)]_2 and [{(η^5-C_5Me_4)SiMe_2(η^1-NCMe_3)}Sc(µ_2-CH_2CH_2CH_3)]_2. Synthesis, Structures, and Kinetic and Equilibrium Investigations of the Catalytically Active Species in Solution

The scandium hydride complex [(Cp*SiNR)(PMe_3)Sc(µ-H)]_2 (1), ((Cp*SiNR) = ((η^5-C_5Me_4)SiMe_2(η^1-NCMe_3)}) is prepared by hydrogenation of (Cp*SiNR)ScCH(SiMe_3)_2 in the presence of trimethylphosphine. The hydride complex is a catalyst precursor for the polymerization of α-olefins, yielding atactic products of low molecular weight (M, = 3000-7000). GC/MS analysis of volatile, oligomeric products revealed that all scandium centers are active during the polymerization. Selectivity for head-to-tail insertion is high (>99%) and for the tetramer, pentamer, and hexamer formed during propene polymerization, the maximum theoretical numbers of head-to-tail stereoisomers are observed by capillary GC. The stoichiometric reaction between 1 and 2 equiv of ethylene produces the unusual ethylene-bridged dimer [(Cp*SiNR)(PMe_3)Sc]_2(µ,η^2,η^2-C_2H_4) (2) and an equivalent of ethane, whereas the same reaction with propene affords the phosphine-free, alkyl-bridged scandium dimer [(Cp*S~NR)Sc]_2(µ-CH_2CH_2CH_3)_2 (3). The absence of coordinating phosphine allows the latter complex to function as a more active olefin polymerization catalyst precursor. 1 reacts with styrene to form a unique double-insertion product arising from sequential 1,2- and 2,1-styrene insertion. The structure of the catalytic intermediate in solution was determined by low-temperature ^(13)C-NMR studies of the model complexes (Cp*SiNR)(P(^(13)CH_3)_3]ScCH_2CH(CH_3)CHCH_2CH_2CH_3 and (Cp*SiNR)(PMe_3)Sc^(13)CH_2CHCH(^(13)CH_3)_2. One phosphine-bound species is observed in equilibrium with only one phosphine-free species. The symmetry properties of the latter indicate that it is a monomeric, hence 12-electron, scandium alkyl complex. Semiquantitative treatment of equilibrium concentration data supports this conclusion

Age-related Changes in Human Bone Proteoglycan Structure: IMPACT OF OSTEOGENESIS IMPERFECTA

Proteoglycans (PGs) are a family of molecules that undergo extensive post-translational modifications that include addition of glycosaminoglycan (GAG) chains as well as N- and O-linked oligosaccharides to the protein core. PG composition and structure have been reported to alter with age. To test whether the post-translational modifications to PGs can serve as in vitro surrogate end point markers for chronological age, the extent of GAG modifications was determined for PGs derived from normal human bone cells of 14 donors (age range, fetal to 60 years). Isolated cells were steady state radiolabeled with (35)SO(4)(2-) and [(3)H]GlcN. For biglycan and decorin, iduronate content was linearly correlated with age (increased 1.5x between fetal and age 60 years). For the syndecan-like heparan sulfate PG, the N-sulfation of post-natal cells increased over 3.5-fold until reaching a plateau during the 4th decade of life. The amount of O-linked oligosaccharides was also found to decrease as a function of increasing normal donor age, whereas the specific activity of the metabolic precursor pool remained constant regardless of donor age. These age-related changes in post-translational modifications were then used to demonstrate that osteoblasts derived from patients with osteogenesis imperfecta did not exhibit facets of a pre-mature aging, but rather were arrested in a fetal-like phenotypic state. A growth matrix rich in thrombospondin altered PG metabolism in osteoblastic cells, resulting in the production and secretion of the fetal-like (rich in O-linked oligosaccharides) forms of decorin and biglycan. This effect was qualitatively different from the effect of transforming growth factor-beta, which predominantly altered GAGs rather than O-linked oligosaccharides. No other Arg-Gly-Asp protein (fibronectin, vitronectin, type I collagen, osteopontin, and bone sialoprotein) showed any detectable effect on PG metabolism in bone cells. These results indicate that a proper matrix stoichiometry is critical for metabolism of PGs

Sequence-based prediction for vaccine strain selection and identification of antigenic variability in foot-and-mouth disease virus

Identifying when past exposure to an infectious disease will protect against newly emerging strains is central to understanding the spread and the severity of epidemics, but the prediction of viral cross-protection remains an important unsolved problem. For foot-and-mouth disease virus (FMDV) research in particular, improved methods for predicting this cross-protection are critical for predicting the severity of outbreaks within endemic settings where multiple serotypes and subtypes commonly co-circulate, as well as for deciding whether appropriate vaccine(s) exist and how much they could mitigate the effects of any outbreak. To identify antigenic relationships and their predictors, we used linear mixed effects models to account for variation in pairwise cross-neutralization titres using only viral sequences and structural data. We identified those substitutions in surface-exposed structural proteins that are correlates of loss of cross-reactivity. These allowed prediction of both the best vaccine match for any single virus and the breadth of coverage of new vaccine candidates from their capsid sequences as effectively as or better than serology. Sub-sequences chosen by the model-building process all contained sites that are known epitopes on other serotypes. Furthermore, for the SAT1 serotype, for which epitopes have never previously been identified, we provide strong evidence - by controlling for phylogenetic structure - for the presence of three epitopes across a panel of viruses and quantify the relative significance of some individual residues in determining cross-neutralization. Identifying and quantifying the importance of sites that predict viral strain cross-reactivity not just for single viruses but across entire serotypes can help in the design of vaccines with better targeting and broader coverage. These techniques can be generalized to any infectious agents where cross-reactivity assays have been carried out. As the parameterization uses pre-existing datasets, this approach quickly and cheaply increases both our understanding of antigenic relationships and our power to control disease

Prediction of cardiovascular outcomes with machine learning techniques: application to the Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL) study.

Background: Data derived from the Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL) study were analyzed in an effort to employ machine learning methods to predict the composite endpoint described in the original study. Methods: We identified 573 CORAL subjects with complete baseline data and the presence or absence of a composite endpoint for the study. These data were subjected to several models including a generalized linear (logistic-linear) model, support vector machine, decision tree, feed-forward neural network, and random forest, in an effort to attempt to predict the composite endpoint. The subjects were arbitrarily divided into training and testing subsets according to an 80%:20% distribution with various seeds. Prediction models were optimized within the CARET package of R. Results: The best performance of the different machine learning techniques was that of the random forest method which yielded a receiver operator curve (ROC) area of 68.1%±4.2% (mean ± SD) on the testing subset with ten different seed values used to separate training and testing subsets. The four most important variables in the random forest method were SBP, serum creatinine, glycosylated hemoglobin, and DBP. Each of these variables was also important in at least some of the other methods. The treatment assignment group was not consistently an important determinant in any of the models. Conclusion: Prediction of a composite cardiovascular outcome was difficult in the CORAL population, even when employing machine learning methods. Assignment to either the stenting or best medical therapy group did not serve as an important predictor of composite outcome. Clinical Trial Registration: ClinicalTrials.gov, NCT00081731

Quantifying sociodemographic and income disparities in medical therapy and lifestyle among symptomatic patients with suspected coronary artery disease: a cross-sectional study in North America

Objectives: To evaluate potential gaps in preventive medical therapy and healthy lifestyle practices among symptomatic patients with suspected coronary artery disease (CAD) seeing primary care physicians and cardiologists and how gaps vary by sociodemographic characteristics and baseline cardiovascular risk. Design: Cross-sectional study assessing potential preventive gaps. Participants: 10 003 symptomatic outpatients evaluated by primary care physicians, cardiologists or other specialists for suspected CAD. Setting: PROspective Multicenter Imaging Study for Evaluation of Chest Painfrom 2010 to 2014. Measures Primary measures were absence of an antihypertensive, statin or angiotensin-converting enzyme inhibitor/angiotensin receptor blocker for renal protection in patients with hypertension, dyslipidaemia or diabetes, respectively, and being sedentary, smoking or being obese. Results: Preventive treatment gaps affected 14% of patients with hypertension, 36% of patients with dyslipidaemia and 32% of patients with diabetes. Overall, 49% of patients were sedentary, 18% currently smoked and 48% were obese. Women were significantly more likely to not take a statin for dyslipidaemia and to be sedentary. Patients with lower socioeconomic status were also significantly more likely to not take a statin. Compared with Whites, Blacks were significantly more likely to be obese, while Asians were less likely to smoke or be obese. High-risk patients sometimes experienced larger preventive care gaps than low-risk patients. For patients with dyslipidaemia, the presence of a treatment gap was associated with a higher risk of an adverse event (HR 1.35, 95% CI 1.02 to 1.82). Conclusions: Among contemporary, symptomatic patients with suspected CAD, significant gaps exist in preventive care and lifestyle practices, and high-risk patients sometimes had larger gaps. Differences by sex, age, race/ethnicity, socioeconomic status and geography are modest but contribute to disparities and have implications for improving opulation health. For patients with dyslipidaemia, the presence of a treatment gap was associated with a higher risk of an adverse event. Clinical trial registration Clinical Trials.gov identifier NCT01174550

Immunogenomic profiling determines responses to combined PARP and PD-1 inhibition in ovarian cancer

Combined PARP and immune checkpoint inhibition has yielded encouraging results in ovarian cancer, but predictive biomarkers are lacking. We performed immunogenomic profiling and highly multiplexed single-cell imaging on tumor samples from patients enrolled in a Phase I/II trial of niraparib and pembrolizumab in ovarian cancer (NCT02657889). We identify two determinants of response; mutational signature 3 reflecting defective homologous recombination DNA repair, and positive immune score as a surrogate of interferon-primed exhausted CD8+T-cells in the tumor microenvironment. Presence of one or both features associates with an improved outcome while concurrent absence yields no responses. Single-cell spatial analysis reveals prominent interactions of exhausted CD8+T-cells and PD-L1+macrophages and PD-L1+tumor cells as mechanistic determinants of response. Furthermore, spatial analysis of two extreme responders shows differential clustering of exhausted CD8+T-cells with PD-L1+macrophages in the first, and exhausted CD8+T-cells with cancer cells harboring genomic PD-L1 and PD-L2 amplification in the second. A Phase I/II trial previously revealed variable anti-tumor efficacy of the PARP inhibitor niraparib in combination with the PD-1 inhibitor pembrolizumab in platinum-resistant ovarian cancer patients. Here, the authors perform an integrated genomic and immunomics analysis of tumor samples from the same patients and find potential predictive biomarkers of response to such combination therapy.Peer reviewe

The \u3cem\u3eChlamydomonas\u3c/em\u3e Genome Reveals the Evolution of Key Animal and Plant Functions

Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the ∼120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella