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Complete Analysis (complete + analysis)
Selected AbstractsStructure elucidation of [1,3]oxazolo[4,5- e][2,1]benzisoxazole and naphtho[1,2- d][1,3]- and phenanthro[9,10- d]oxazoles using gradient selected gHMBC, gHMQC and gHMQC-TOCSY NMR techniquesMAGNETIC RESONANCE IN CHEMISTRY, Issue 11 2003Alan R. Katritzky Abstract Structure elucidation of compounds in the benzisoxazole series (1,6) and naphtho[1,2- d][1,3]- (7,10) and phenanthro[9,10- d][1,3]oxazole (11,14) series was accomplished using extensive 2D NMR spectroscopic studies including 1H,1H COSY, long- range 1H,1H COSY, 1H,13C COSY, gHMQC, gHMBC and gHMQC-TOCSY experiments. The distinction between oxazole and isoxazole rings was made on the basis of the magnitude of heteronuclear one-bond 1JC2, H2 (or 1JC3, H3) coupling constants. Complete analysis of the 1H NMR spectra of 11,14 was achieved by iterative calculations. Gradient selected gHMQC-TOCSY spectra of phenanthro[9,10- d][1,3]oxazoles 11,14 were obtained at different mixing times (12, 24, 36, 48 and 80 ms) to identify the spin system where the protons of phenanthrene ring at H-5, H-6 and at H-9 and H-7 and H-8 were highly overlapping. Copyright © 2003 John Wiley & Sons, Ltd. [source] Evidence for a single-step mechanism in the origin of hyperdiploid childhood acute lymphoblastic leukemiaGENES, CHROMOSOMES AND CANCER, Issue 2 2005Kajsa Paulsson High hyperdiploidy (>50 chromosomes) in childhood acute lymphoblastic leukemia (ALL) is characterized by nonrandom multiple trisomies and tetrasomies involving in particular chromosomes X, 4, 6, 8, 10, 14, 17, 18, and 21. This characteristic karyotypic pattern, the most common in pediatric ALL, may arise via a tetraploid state with subsequent loss of chromosomes, by sequential gains of chromosomes in consecutive cell divisions, or by simultaneous gain of chromosomes in a single mitosis. These alternatives may be distinguished by investigation of the allelic ratios of loci on the tetrasomic and disomic chromosomes. Previous studies of tetrasomy 21 and of the occurrence of uniparental disomies (UPDs) have suggested that the most likely mechanism is simultaneous gain. However, the other pathways have not been definitely excluded because complete analyses of all disomies and tetrasomies have never been performed. In the present study, we investigated 27 hyperdiploid ALLs by using 58 polymorphic microsatellite markers mapped to 23 of the 24 human chromosomes. Twenty-six tetrasomies were analyzed (involving chromosomes X, 8, 10, 14, 18, and 21), and the frequency of UPDs was determined in 10 cases. In total, 200 chromosomes were studied. Equal allele dosage was observed in 24 of 26 tetrasomies, and only 7 UPDs were found. These data strongly suggest that hyperdiploidy in childhood ALL generally arises by a simultaneous gain of all additional chromosomes in a single abnormal mitosis. © 2005 Wiley-Liss, Inc. [source] Was Mancur a Maoist?ECONOMICS & POLITICS, Issue 2 2003An Essay on Kleptocracy, Political Stability Much of Mancur Olson's work explored the link between government structure and economic development. This paper provides a framework for thinking about this link that exposes both the powerful insights and the deep tensions in Olson's work. In The Rise and Decline of Nations Olson argued that instability was good for democratic accountability because it upset entrenched interests. In contrast, after the fall of the socialist regimes in Europe and the Soviet Union, Olson argued that the stability of a single autocrat or "stationary bandit" was superior to the competitive rent seeking of competing "roving bandits." I argue that there is a real inconsistency in Olson's thinking on the role of stability and change in political life; I do this by developing the connections between Olson's classic Logic of Collective Action and his subsequent writing. The paper concludes by building on Olson's insights to point the way to a more complete analysis of democracy and transition. [source] Comparison between objective and subjective measurements of quality of service over an Optical Wide Area networkEUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 3 2008Francesco Matera The introduction of intelligence for management and control of the quality of service (QoS) are key issues for the evolution of the next generation IP optical network based on Ethernet technology. A test bed of a core-access network was implemented to investigate such issues and in this paper, the authors report measurements concerning the QoS of multimedia services for different traffic conditions. The network was implemented with a differentiated service over Multi-Protocol Label Switch (MPLS) architecture; it consists of a real optical network based on core routers with optical Gigabit Ethernet (GBE) interfaces connected by means of long single mode fibres (about 50\,km), contained in an installed cable between Rome and Pomezia. The network is based on different access devices, but in this paper we only refer to an access based on Fibre To The building (FTTB) architecture. The QoS was investigated both in terms of network (or objective) tests that include packet loss, jitter, one way delay and throughput measurements and perceptive (or subjective) tests that conversely are based on the evaluation of user perception. The services under test mainly consisted of video streams that circulated in the network according to the switching operations based in the IP differentiated service over MPLS technique that allowed us to guarantee the QoS for some class of service, also in the presence of network overload. Particular attention was given to the correlation between objective and subjective measurements. Furthermore, in order to have a complete analysis about QoS of real networks, measurements were performed also in the presence of restoration operations for link failures; in particular we compare the results in the case of conventional IP network restoration with a procedure proposed by us and based on a link switching activated by the loss of signal command coming from the routers. Copyright © 2007 John Wiley & Sons, Ltd. [source] Up-to-date cancer survival: Period analysis and beyondINTERNATIONAL JOURNAL OF CANCER, Issue 6 2009Hermann Brenner Abstract Since its introduction in 1996, period analysis has been shown to be useful for deriving more up-to-date cancer survival estimates, and the method is now increasingly used for that purpose in national and international cancer survival studies. However, period analysis, like other commonly employed methods, is just a special case from a broad class of design options in the analysis of cancer survival data. Here, we explore a broader range of design options, including 2 model-based approaches, for deriving up-to-date estimates of 5- and 10-year relative survival for patients diagnosed in the most recent 5-year interval for which data are available. The performance of the various designs is evaluated empirically for 20 common forms of cancer using more than 50-year long time series of data from the Finnish Cancer Registry. Period analysis as well as the 2 model-based approaches, one using a "cohort-type model" and another using a "period-type model", all performed better than traditional cohort or complete analysis. Compared with "standard period analysis", the cohort-type model further increased up-to-dateness of survival estimates, whereas the period-type model increased their precision. While our analysis confirms advantages of period analysis over traditional methods in terms of up-to-dateness of cancer survival data, further improvements are possible by flexible use of model-based approaches. © 2008 Wiley-Liss, Inc. [source] Modelling of photonic bandgap devices by the leaky mode propagation methodINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 3 2003Agostino Giorgio Abstract Main modelling approaches used for investigating the Photonic bandgap (PBG) devices are reviewed. In particular, the model based on Leaky Mode Propagation (LMP) method is described. A complete analysis of the propagation characteristics, including the determination of modal propagation constants, electromagnetic field harmonics and total field distribution, transmission and reflection coefficients, total forward and backward power flow in the structure, guided and radiated power, and total losses, can be carried out by a computer program based on the LMP approach. The numerical results have been validated by comparisons with those obtained by using other more complex and expensive models. The new model shows some significant advantages in terms of very low computational time, absence of any a priori theoretical assumptions and approximations, capability of simulating the actual physical behaviour of the device and fast determination of the bandgap position.Copyright © 2003 John Wiley & Sons, Ltd. [source] A precise boundary element method for macromolecular transport propertiesJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 9 2004Sergio Aragon Abstract A very precise boundary element numerical solution of the exact formulation of the hydrodynamic resistance problem with stick boundary conditions is presented. BEST, the Fortran 77 program developed for this purpose, computes the full transport tensors in the center of resistance or the center of diffusion for an arbitrarily shaped rigid body, including rotation-translation coupling. The input for this program is a triangulation of the solvent-defined surface of the molecule of interest, given by Connolly's MSROLL or other suitable triangulator. The triangulation is prepared for BEST by COALESCE, a program that allows user control over the quality and number of triangles to describe the surface. High numerical precision is assured by effectively exact integration of the Oseen tensor over triangular surface elements, and by scaling the hydrodynamic computation to the precise surface area of the molecule. Efficiency of computation is achieved by the use of public domain LAPACK routines that call BLAS Level 3 hardware-optimized subroutines available for most processors. A protein computation can be done in less than 10 min of CPU time in a modern Pentium IV processor. The present work includes a complete analysis of the sources of error in the numerical work and techniques to eliminate these errors. The operation of BEST is illustrated with applications to ellipsoids of revolution, and Lysozyme, a small protein. The typical numerical accuracy achieved is 0.05% compared to analytical theory. The numerical precision for a protein is better than 1%, much better than experimental errors in these quantities, and more than 10 times better than traditional bead-based methods. © 2004 Wiley Periodicals, Inc. J Comput Chem 9: 1191,1205, 2004 [source] Individual patient data meta-analysis of randomized anti-epileptic drug monotherapy trialsJOURNAL OF EVALUATION IN CLINICAL PRACTICE, Issue 2 2000Paula R. Williamson PhD Abstract Meta-analysis may be based on either aggregate data or individual patient data (IPD). Three reasons why IPD are desirable for the meta-analysis of anti-epileptic drug (AED) monotherapy trials are: (1) to undertake a more complete analysis of time-to-event outcomes; (2) to investigate the interaction between AED and type of epilepsy; and (3) to undertake re-analysis of the trial to obtain results for all relevant outcomes. We demonstrate that IPD meta-analysis is possible in AED research. Problems arose from missing data at four levels: (1) unknown trials; (2) known trials but no IPD supplied; (3) known trials but missing outcome data for some individuals within trials; and (4) known trials but missing covariate data for some individuals within trials. Empirical evidence of the reliability of meta-analyses based on aggregate rather than individual patient data is still lacking. Examples of other benefits such projects may bring include improvements to the design of a new trial in the area, in terms of the sample size considerations, the definition of outcomes and data collection. [source] Gerbera jamesonii, a New Host of Fusarium oxysporum f.sp. tracheiphilumJOURNAL OF PHYTOPATHOLOGY, Issue 1 2010Marco Troisi Abstract The random amplified polymorphic DNA (RAPD) technique was used to analyze the total genomic DNA of pathogenic isolates of Fusarium oxysporum on Gerbera jamesonii by comparing them to representatives of the formae speciales chrysanthemi and tracheiphilum. A close genetic relationship was observed among most of the new isolates from G. jamesonii. They shared RAPD markers with the tested representatives of the forma specialis chrysanthemi. Some isolates of those tested from diseased G. jamesonii were placed in a different cluster, which included representative isolates of forma specialis tracheiphilum. This is the first report of F. oxysporum f.sp. tracheiphilum on G. jamesonii. A rapid protocol for DNA extraction directly from fungal colonies grown on potato dextrose agar allowed complete analysis in less than 4 h. [source] Accuracy of single-detector spiral CT in the diagnosis of pulmonary embolism: a prospective multicenter cohort study of consecutive patients with abnormal perfusion scintigraphyJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 1 2005M. J. L. VAN STRIJEN Summary.,Background: Spiral computed tomography (CT) has emerged as a potentially conclusive diagnostic test to exclude pulmonary embolism (PE) in patients with non-high probability scintigraphy and is already widely used,sometimes as the sole primary diagnostic test in the diagnosis of suspected PE. Its true sensitivity and specificity has, however, not been evaluated previously in a large cohort of consecutive patients. Methods: In a multicenter prospective study 627 consecutive patients with clinically suspected PE were studied. Patients with normal perfusion scintigraphy were excluded from further analysis. Single-detector spiral CT scanning and ventilation scintigraphy were then performed in all patients to diagnose PE, while pulmonary angiography was performed as the gold standard. The only exceptions were those patients who had both a high-probability VQ scan and a CT scan positive for PE: these patients were considered to have PE and did not undergo additional pulmonary angiography. All imaging tests were read by independent expert panels. Results: Five hundred and seventeen patients were available for complete analysis. The prevalence of PE was 32%. Spiral CT correctly identified 88 of 128 patients with PE, and 92 of 109 patients without PE, for a sensitivity and specificity of 69%[95% confidence interval (CI) 63,75] and 84% (95% CI 80,89), respectively. The sensitivity of spiral CT was 86% (95% CI 80,92) for segmental or larger PE and 21% (95% CI 14,29) in the group of patients with subsegmental PE. Conclusion: The overall sensitivity of spiral CT for PE is too low to endorse its use as the sole test to exclude PE. This holds true even if one limits the discussion to patients with larger PE in segmental or larger pulmonary artery branches. We conclude that, in patients with clinically suspected PE and an abnormal perfusion scintigraphy, single-slice detector spiral CT is not sensitive enough to be used as the sole test to exclude PE. [source] Influence of the C,H· · ·N intramolecular interaction on the spatial structures and 1H and 13C NMR parameters of heteroaryl vinyl ethers and sulfidesMAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2003Andrei V. Afonin Abstract A complete analysis of the 1H and 13C spectra of the representative series of heteroaryl vinyl ethers and sulfides and heteroaryl styryl sulfides was carried out. The electronic and spatial structures of these compounds are discussed. It was shown that the C,H· · ·N intramolecular interactions in the investigated molecules influence significantly the spectral parameters and the conformational equilibrium. Copyright © 2003 John Wiley & Sons, Ltd. [source] Endogenous Random Asset Prices in Overlapping Generations EconomiesMATHEMATICAL FINANCE, Issue 1 2000Volker Böhm This paper derives a general explicit sequential asset price process for an economy with overlapping generations of consumers. They maximize expected utility with respect to subjective transition probabilities given by Markov kernels. The process is determined primarily by the interaction of exogenous random dividends and the characteristics of consumers, given by arbitrary preferences and expectations, yielding an explicit random dynamical system with expectations feedback. The paper studies asset prices and equity premia for a parametrized class of examples with CARA utilities and exponential distributions. It provides a complete analysis of the role of risk aversion and of subjective as well as rational beliefs. [source] The strong partition relation on ,1 revisitedMLQ- MATHEMATICAL LOGIC QUARTERLY, Issue 1 2004Steve Jackson Abstract We give a new proof of the strong partition relation on ,1, assuming the axiom of determinacy, which uses only a general argument not involving the complete analysis of a measure on ,1. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cosmic microwave background signal in Wilkinson Microwave Anisotropy Probe three-year data with fasticaMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007D. Maino ABSTRACT We present an application of the fast Independent Component Analysis (fastica) to the Wilkinson Microwave Anisotropy Probe (WMAP) three-year data with the goal of extracting the cosmic microwave background (CMB) signal. We evaluate the confidence of our results by means of Monte Carlo simulations including the CMB, foreground contaminations and instrumental noise specific to each WMAP frequency band. We perform a complete analysis involving all or a subset of the WMAP channels in order to select the optimal combination for CMB extraction, using the frequency scaling of the reconstructed component as a figure of merit. We find that the combination KQVW provides the best CMB frequency scaling, indicating that the low-frequency foreground contamination in Q, V and W bands is better traced by the emission in the K band. The CMB angular power spectrum is recovered up to the degree scale; it is consistent within errors for all WMAP channel combinations considered, and in close agreement with the WMAP three-year results. A power spectrum analysis is made of the sky map divided into two hemispheres that have been previously reported as showing evidence of an asymmetric ratio of power on large angular scales. We then confirm the findings of several previous works with independent techniques. [source] Maximum-weight-basis preconditionersNUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 8-9 2004Erik G. Boman Abstract This paper analyses a novel method for constructing preconditioners for diagonally dominant symmetric positive-definite matrices. The method discussed here is based on a simple idea: we construct M by simply dropping offdiagonal non-zeros from A and modifying the diagonal elements to maintain a certain row-sum property. The preconditioners are extensions of Vaidya's augmented maximum-spanning-tree preconditioners. The preconditioners presented here were also mentioned by Vaidya in an unpublished manuscript, but without a complete analysis. The preconditioners that we present have only O(n+t2) nonzeros, where n is the dimension of the matrix and 1,t,n is a parameter that one can choose. Their construction is efficient and guarantees that the condition number of the preconditioned system is O(n2/t2) if the number of nonzeros per row in the matrix is bounded by a constant. We have developed an efficient algorithm to construct these preconditioners and we have implemented it. We used our implementation to solve a simple model problem; we show the combinatorial structure of the preconditioners and we present encouraging convergence results. Copyright © 2004 John Wiley & Sons, Ltd. [source] Primary breast non-Hodgkin's lymphoma: A large single center study of initial characteristics, natural history, and prognostic factors,AMERICAN JOURNAL OF HEMATOLOGY, Issue 3 2009Patricia Validire The aims of this study were to define the initial pathological and clinical characteristics, and prognostic factors of patients with primary breast malignant lymphoma (PBL). All patients treated at the Institut Curie for lymphoma with breast involvement were reviewed. A pathological review of all cases was performed. Forty-five cases were selected in whom 38 cases were of diffuse large B-cell lymphoma. A complete analysis was then performed on these 38 patients. Twenty out of 28 cases (71%) of cases were Bcl-2 positive and four out of 28 (14%) had a CD10 positive staining. Peculiar initial characteristics showed nodal involvement in 58% of the cases and two or more extra-nodal sites in 31% of the cases. Among the 37 patients for whom all data were available, and according to the International Prognostic Index, 19 patients (51%) were classified in the low-risk group, 5 cases (14%) in the low- to intermediate-risk group, 6 patients (16%) in the intermediate- to high-risk group, and 7 (19%) case in the high-risk group. At the end of initial therapy, 34 patients (89%) achieved CR. With a median follow-up of 96 months, 18 patients (47%) relapsed of whom 3 had a relapse in central nervous system site. The 5-year disease-free (DFS) and overall survivals (OS) were 54% and 61%, respectively. In multivariate analysis, the presence of 2 or more extranodal sites was prognostic for lower DFS (P = 0.0008) and OS (P = 0.09), and a performance status ,1 was prognostic for lower OS (P = 0.005). Finally, when our series was compared with a historical series of 111 patients with aggressive nodal lymphomas, we observed significant lower survival rates in localized PBL (P < 0.03). Initial breast localization has a pejorative impact on the outcome of patients with Non-Hodgkin's Lymphoma (NHL), with an impressive adverse influence of additional extranodal sites. These results suggest a specific management of NHL with breast involvement. Am. J. Hematol., 2009. © 2008 Wiley-Liss, Inc. [source] Chemiluminescence inhibition assay for folic acid using flow injection analysisPHYTOCHEMICAL ANALYSIS, Issue 4 2003Zhenghua Song Abstract A new flow injection method for the determination of folic acid is described. A fast oxidation reaction occurred when folic acid was mixed with potassium ferricyanide generating ferrocyanide which then inhibited the chemiluminescent reaction of ferricyanide and luminol in alkaline medium. The decrease of chemiluminescence intensity was correlated with the folic acid concentration in the range 0.1,21,µg/mL; the detection limit for the assay was 0.03,µg/mL (3,). A complete analysis of folic acid, including sampling and washing, could be performed within 2,min with a relative standard deviation of less than 4.0%. The proposed method has been applied successfully to the determination of folic acid in pharmaceutical preparations Copyright © 2003 John Wiley & Sons, Ltd. [source] Analysis of the vacuum infusion molding processPOLYMER COMPOSITES, Issue 1 2000A. Hammami The vacuum infusion molding process is becoming increasingly popular for the production of large composite parts. A comprehensive model of the process has not been proposed yet, making its optimization difficult. The flexible nature of the vacuum bag coupled to the varying pressure inside the mold cavity results in a variation of the cavity thickness during the impregnation. A complete simulation model must incorporate this phenomenon. In this paper, a complete analysis of the vacuum infusion molding process is presented. The analysis is not restricted to the theoretical aspects but also reviews the effect of the main processing parameters. The parameters investigated in this paper are thought to be those of most interest for the process, i.e. the compaction of the reinforcement, the permeability, the infusion strategy and the presence of flow enhancement layers. Following the characterization experiments, a 1-D model for the vacuum infusion molding process is presented. This model is derived assuming that an elastic equlibrium holds in the mold cavity during mold filling. Even though good agreement was found between simulation results and experiments, it is concluded that additional work is needed on the numerical model to integrate interesting findings from the experimental part. [source] Structure of human brain fructose 1,6-(bis)phosphate aldolase: Linking isozyme structure with functionPROTEIN SCIENCE, Issue 12 2004Tracy L. Arakaki Abstract Fructose-1,6-(bis)phosphate aldolase is a ubiquitous enzyme that catalyzes the reversible aldol cleavage of fructose-1,6-(bis)phosphate and fructose 1-phosphate to dihydroxyacetone phosphate and either glyceral-dehyde-3-phosphate or glyceraldehyde, respectively. Vertebrate aldolases exist as three isozymes with different tissue distributions and kinetics: aldolase A (muscle and red blood cell), aldolase B (liver, kidney, and small intestine), and aldolase C (brain and neuronal tissue). The structures of human aldolases A and B are known and herein we report the first structure of the human aldolase C, solved by X-ray crystallography at 3.0 Å resolution. Structural differences between the isozymes were expected to account for isozyme-specific activity. However, the structures of isozymes A, B, and C are the same in their overall fold and active site structure. The subtle changes observed in active site residues Arg42, Lys146, and Arg303 are insufficient to completely account for the tissue-specific isozymic differences. Consequently, the structural analysis has been extended to the isozyme-specific residues (ISRs), those residues conserved among paralogs. A complete analysis of the ISRs in the context of this structure demonstrates that in several cases an amino acid residue that is conserved among aldolase C orthologs prevents an interaction that occurs in paralogs. In addition, the structure confirms the clustering of ISRs into discrete patches on the surface and reveals the existence in aldolase C of a patch of electronegative residues localized near the C terminus. Together, these structural changes highlight the differences required for the tissue and kinetic specificity among aldolase isozymes. [source] Albumin depletion of human plasma also removes low abundance proteins including the cytokinesPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 18 2005Jill Granger Abstract The use of proteomics for efficient, accurate, and complete analysis of clinical samples poses a variety of technical challenges. The presence of higher abundance proteins in the plasma, such as albumin, may mask the detection of lower abundance proteins such as the cytokines. Methods have been proposed to deplete the sample of these higher abundance proteins to facilitate detection of those with lower abundance. In this study, a commercially available albumin depletion kit was used to determine if removal of albumin would measurably reduce detection of lower abundance cytokine proteins in human plasma. The Montage® Albumin Deplete Kit (Millipore) was used to deplete albumin from LPS-stimulated whole blood from 15 normal human donors. Albumin depletion was measured using the BCG reagent and SDS-PAGE, and cytokine recovery was determined by a microassay immunoassay that measures both pro- and anti-inflammatory cytokines. Average albumin depletion from the samples was 72%. However, several cytokines were also significantly reduced when the albumin was removed from the plasma. Additionally, there was a variable reduction in cytokine recovery from a known mixture of cytokines in a minimal amount of plasma that were loaded onto the columns. These data demonstrate that there may be a non-specific loss of cytokines following albumin depletion, which may confound subsequent proteomic analysis. [source] A full-factor multivariate GARCH modelTHE ECONOMETRICS JOURNAL, Issue 2 2003I. D. Vrontos A new multivariate time series model with time varying conditional variances and covariances is presented and analysed. A complete analysis of the proposed model is presented consisting of parameter estimation, model selection and volatility prediction. Classical and Bayesian techniques are used for the estimation of the model parameters. It turns out that the construction of our proposed model allows easy maximum likelihood estimation and construction of well-mixing Markov chain Monte Carlo (MCMC) algorithms. Bayesian model selection is addressed using MCMC model composition. The problem of accounting for model uncertainty is considered using Bayesian model averaging. We provide implementation details and illustrations using daily rates of return on eight stocks of the US market. [source] The commensurate composite ,-structure of ,-tantalumACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2003Alla Arakcheeva The single-crystal investigation of the self-hosting ,-structure of ,-tantalum (,-Ta) at 120,K (low-temperature, LT, structure) and at 293,K (RT-I before cooling and RT-II after cooling and rewarming; RT represents room temperature) shows that this structure is indeed a specific two-component composite where the components have the same (or an integer multiple) lattice constants but different space groups. The space groups of both host (H) and guest (G) components cause systematic absences, which result from their intersection. The highest symmetry of a ,-structure can be described as [H: P42/mnm; G: P4/mbm (cG = 0.5cH); composite: P42/mnm]. A complete analysis of possible symmetries is presented in the Appendix. In ,-Ta, two components modify their symmetry during the thermal process 293,K (RT-I) , 120,K (LT) , 293,K (RT-II): [H: P21m; G: P21m; composite: P21m] , [H: P, G: P4/mbm (cG = 0.5cH), composite: P] , [H: P21m, G: P4/mbm (cG = 0.5cH), composite: P21m]. Thus, the phase transition is reversible with respect to H and irreversible with respect to G. [source] The serine palmitoyltransferase from Sphingomonas wittichii RW1: An interesting link to an unusual acyl carrier proteinBIOPOLYMERS, Issue 9 2010Marine C. C. Raman Abstract Serine palmitoyltransferase (SPT) catalyses the first step in the de novo biosynthesis of sphingolipids (SLs). It uses a decarboxylative Claisen-like condensation reaction to couple L -serine with palmitoyl-CoA to generate a long-chain base product, 3-ketodihydrosphingosine. SLs are produced by mammals, plants, yeast, and some bacteria, and we have exploited the complete genome sequence of Sphingomonas wittichii to begin a complete analysis of bacterial sphingolipid biosynthesis. Here, we describe the enzymatic characterization of the SPT from this organism and present its high-resolution x-ray structure. Moreover, we identified an open reading frame with high sequence homology to acyl carrier proteins (ACPs) that are common to fatty acid biosynthetic pathways. This small protein was co-expressed with the SPT and we isolated and characterised the apo- and holo-forms of the ACP. Our studies suggest a link between fatty acid and sphingolipid metabolism. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 811,822, 2010. [source] | ||||||||||||||||||||||