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Multiple Rounds (multiple + round)

Distribution by Scientific Domains

Life Sciences	42%
Chemistry	28%

Selected Abstracts

A Magnetically Separable Heterogeneous Deallylation Catalyst: [CpRu(,3 -C3H5)(2-pyridinecarboxylato)]PF6 Complex Supported on a Ferromagnetic Microsize Particle Fe3O4@SiO2

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2009
Takuya Hirakawa
Abstract The highly reactive and chemoselective homogeneousdeallylation catalyst CpRu(,3 -C3H5)(4-substituted-2-pyridinecarboxylato) was immobilized on microsize spherical Fe3O4@SiO2 particles. The resultant heterogeneous catalyst displays high saturation magnetization, weak coercive forces and high levels of dispersibility. The catalyst has increased the utility of deallylation by allowing the reaction to be conducted without extra additives. The only co-product of the reaction is a volatile allyl ether compound. Here, we demonstrate the efficient deallylation and separation of highly polar multifunctional compounds as well as multiple rounds of catalyst recycling without significant loss of reactivity. The usefulness of this catalyst has been confirmed by the synthesis of a triribonucleotide 3,5 U. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

DNA gyrase requirements distinguish the alternate pathways of Mu transposition

MOLECULAR MICROBIOLOGY, Issue 2 2003
Tanya D. Sokolsky
Summary The MuA transposase mediates transposition of bacteriophage Mu through two distinct mechanisms. The first integration event following infection occurs through a non-replicative mechanism. In contrast, during lytic growth, multiple rounds of replicative transposition amplify the phage genome. We have examined the influence of gyrase and DNA supercoiling on these two transposition pathways using both a gyrase-inhibiting drug and several distinct gyrase mutants. These experiments reveal that gyrase activity is not essential for integration; both lysogens and recombination intermediates are detected when gyrase is inhibited during Mu infection. In contrast, gyrase inhibition causes severe defects in replicative transposition. In two of the mutants, as well as in drug-treated cells, replicative transposition is almost completely blocked. Experiments probing for formation of MuA,DNA complexes in vivo reveal that this block occurs very early, during assembly of the transposase complex required for the catalytic steps of recombination. The findings establish that DNA structure-based signals are used differently for integrative and replicative transposition. We propose that transposase assembly, the committed step for recombination, has evolved to depend on different DNA /architectural signals to control the reaction outcome during these two distinct phases of the phage life cycle. [source]

SEPH, a Cdc7p orthologue from Aspergillus nidulans, functions upstream of actin ring formation during cytokinesis

MOLECULAR MICROBIOLOGY, Issue 1 2001
Kenneth S. Bruno
In the filamentous fungus, Aspergillus nidulans, multiple rounds of nuclear division occur before cytokinesis, allowing an unambiguous identification of genes required specifically for cytokinesis. As in animal cells, both an intact microtubule cytoskeleton and progression through mitosis are required for actin ring formation and contraction. The sepH gene from A. nidulans was discovered in a screen for temperature-sensitive cytokinesis mutants. Sequence analysis showed that SEPH is 42% identical to the serine,threonine kinase Cdc7p from fission yeast. Signalling through the Septation Initiation Network (SIN), which includes Cdc7p and the GTPase Spg1p, is emerging as a primary regulatory pathway used by fission yeast to control cytokinesis. A similar group of proteins comprise the Mitotic Exit Network (MEN) in budding yeast. This is the first direct evidence for the existence of a functional SIN,MEN pathway outside budding and fission yeast. In addition to SEPH, potential homologues were also identified in other fungi and plants but not in animal cells. Deletion of sepH resulted in a viable strain that failed to septate at any temperature. Interestingly, quantitative analysis of the actin cytoskeleton revealed that sepH is required for construction of the actin ring. Therefore, SEPH is distinct from its counterpart in fission yeast, in which SIN components operate downstream of actin ring formation and are necessary for ring contraction and later events of septation. We conclude that A. nidulans has components of a SIN,MEN pathway, one of which, SEPH, is required for early events during cytokinesis. [source]

A Resource-Process Framework of New Service Development

PRODUCTION AND OPERATIONS MANAGEMENT, Issue 2 2007
Craig M. Froehle
Motivated by the increasing attention given to the operational importance of developing new services, this paper offers a theoretical framework that integrates both process- and resource-oriented perspectives of new service development (NSD) by defining and organizing 45 practice constructs for NSD-related practices and activities that occur in contemporary service firms. We employ a rigorous procedure whereby both quantitative and qualitative data were gathered through multiple rounds of interviews and card-sorting exercises with senior service managers. This iterative refinement process helps ensure that the construct domains and definitions are consistent and that they are applicable across multiple service sectors. A primary contribution of this research is to provide precise operational definitions of theoretically important NSD practice constructs. Importantly, this study expands on the NSD literature by including both resource- and process-centric perspectives within a single framework. A second contribution is to illustrate a general methodology for developing clear, concise, and consistent construct definitions that may be generally useful for production and operations management scholars interested in new construct development for emerging areas. Empirical results suggest that the resource-process framework can help guide and organize future research on, and provide insight into, a more comprehensive view of new service development. [source]

Low free energy cost of very long loop insertions in proteins

PROTEIN SCIENCE, Issue 2 2003
Michelle Scalley-Kim
Abstract Long insertions into a loop of a folded host protein are expected to have destabilizing effects because of the entropic cost associated with loop closure unless the inserted sequence adopts a folded structure with amino- and carboxy-termini in close proximity. A loop entropy reduction screen based on this concept was used in an attempt to retrieve folded sequences from random sequence libraries. A library of long random sequences was inserted into a loop of the SH2 domain, displayed on the surface of M13 phage, and the inserted sequences that did not disrupt SH2 function were retrieved by panning using beads coated with a phosphotyrosine containing SH2 peptide ligand. Two sequences of a library of 2 × 108 sequences were isolated after multiple rounds of panning, and were found to have recovery levels similar to the wild-type SH2 domain and to be relatively intolerant to further mutation in PCR mutagenesis experiments. Surprisingly, although these inserted sequences exhibited little nonrandom structure, they do not significantly destabilize the host SH2 domain. Additional insertion variants recovered at lower levels in the panning experiments were also found to have a minimal effect on the stability and peptide-binding function of the SH2 domain. The additional level of selection present in the panning experiments is likely to involve in vivo folding and assembly, as there was a rough correlation between recovery levels in the phage-panning experiments and protein solubility. The finding that loop insertions of 60,80 amino acids have minimal effects on SH2 domain stability suggests that the free energy cost of inserting long loops may be considerably less than polymer theory estimates based on the entropic cost of loop closure, and, hence, that loop insertion may have provided an evolutionary route to multidomain protein structures. [source]

The Effect of Refinancing Costs and Market Imperfections on the Optimal Call Strategy and the Pricing of Debt Contracts

REAL ESTATE ECONOMICS, Issue 4 2005
Kenneth B. Dunn
This article, which was originally written in 1986, develops a methodology for valuing mortgage-backed securities with refinancing costs. We solve simultaneously for the valuation of the mortgage-backed security (loan) and the borrower's refinancing strategy, pricing all coupon levels simultaneously. Because the borrower may refinance his or her loan and incur costs at many times in the future, the optimal refinancing decisions arise from an optimal dynamic strategy that reflects the costs of all potential future refinancings. Though the borrower faces multiple rounds of refinancing costs, the market value of the loan cannot exceed the call price plus a single round of refinancing costs. [source]

De novo synthesis and assembly of multiplex riboswitches in vitro

BIOTECHNOLOGY PROGRESS, Issue 5 2009
Hao-Hua Sun
Abstract Pools of short synthetic oligonucleotides (oligos) are required in the multiplex and parallel DNA construction. Microarray technology provides a fast and economical mean for massive parallel synthesis of oligos. The method of oligo synthesis with the programmable microfluidic PicoArray could simultaneously synthesize the designed oligos for multiple riboswitch genes. The synthetic oligos were recovered and purified as a pool of oligo mixture (OligoMix). Three temperature steps were employed to denature, anneal and extend the designed OligoMix until, after multiple rounds of thermocycling, the riboswitches with the desired length are obtained. The OligoMix was amplified using this PCR-based technique and the flanking adapter segments were cleaved for following assembly. Based on these oligos derived from 197 riboswitch sequences, the method of simultaneous assembling multiplex riboswitches (SAMRs) showed high fidelity by sequence identification. The resultant error rate was determined to be 2.78,. With the templates from SAMRs, in vitro transcription was applied to produce milligram amounts of biologically active riboswitches. With the verification of biological activity based on the high specificity of recognizing small-molecule metabolites as well as the DNA sequence redivivus by RT-PCR, the assembled riboswitches can be used for further gene operation and biological application. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]