Home About us Contact
|
Home About us Contact | ||
|
|
||
Analytical Problems (analytical + problem)
Selected AbstractsCan glycans unveil the origin of glycoprotein hormones?,human chorionic gonadotrophin as an example,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2008R. Ramírez-Llanelis Abstract Doping with (glyco)protein hormones represent an extremely challenging, analytical problem as nearly all are constitutively present at low concentrations that fluctuate according to circadian or alternative periodical, or external stimuli. Thus the mere concentration in a biological sample is only resolutive when this surpasses extreme values. As the vast majority of these molecules are produced by recombinant DNA technology it is believed that the exogenous molecules could bear the signature of the host cell. In particular, these could comprise structural differences originated from co or post-translational differences. In this study we have employed both proteomics and glycomics strategies to compare recombinant and urinary human chorionic gonadotrophin in order to evaluate this hypothesis. As anticipated the recombinant hormone could be shown to contain N -glycolyl neuraminic acid, a sialic acid that cannot be produced by humans. Furthermore, differences were observed in the overall glycosylation, in particular the presence of abundant hybrid-type glycans that were much less pronounced in the recombinant species. These differences were determined to occur predominantly in the ,-subunit for which antidoping strategies focussed on these elements could be used for both chorionic gonadotrophin and lutrophin as they share the same ,-subunit. Copyright © 2008 John Wiley & Sons, Ltd. [source] Cover Picture: Electrophoresis 7'2010ELECTROPHORESIS, Issue 7 2010Article first published online: 26 MAR 2010 Issue no. 7 is a special issue on CE-MS consisting of "19 manuscripts subdivided into three major categories: one devoted to instrumental and methodical advances, two providing an insight into up-to-date applications from the fields of technical and natural products, food and environmental analysis on the one hand and biomedical and pharmaceutical analysis on the other hand. Diverse approaches how CE-MS can be employed for the solution of various analytical problems can be found in these papers. Different modes of electroseparation techniques in the capillary format such as CZE, CEC or MEEKC are coupled to various MS instruments ranging from simple quadrupole MS instruments to state of the art QTOF's, using a range of interfaces such as ESI, ICP or APPI. So this special issue will again try to present an overview of current trends and developments in the fields of CE-MS" [source] Identifying Rivals and Rivalries in World PoliticsINTERNATIONAL STUDIES QUARTERLY, Issue 4 2001William R. Thompson Instead of assuming that all actors are equally likely to clash, and that they do so independently of previous clashes, rivalry analysis can focus on the small number of feuding dyads that cause much of the trouble in the international system. But the value added of this approach will hinge in part on how rivalries are identified. Rivalry dyads are usually identified by satisfying thresholds in the frequency of militarized disputes occurring within some prespecified interval of time. But this approach implies a number of analytical problems including the possibility that rivalry analyses are simply being restricted to a device for distinguishing between states that engage in frequent and infrequent conflict. An alternative approach defines rivalry as a perceptual categorizing process in which actors identify which states are sufficiently threatening competitors to qualify as enemies. A systematic approach to identifying these strategic rivalries is elaborated. The outcome, 174 rivalries in existence between 1816 and 1999 are named and compared to the rivalry identification lists produced by three dispute density approaches. The point of the comparison is not necessarily to assert the superiority of one approach over others as it is to highlight the very real costs and benefits associated with different operational assumptions. The question must also be raised whether all approaches are equally focused on what we customarily mean by rivalries. Moreover, in the absence of a consensus on basic concepts and measures, rivalry findings will be anything but additive even if the subfield continues to be monopolized by largely divergent dispute density approaches. [source] Outcomes of the International Union of Crystallography Commission on Powder Diffraction Round Robin on Quantitative Phase Analysis: samples 2, 3, 4, synthetic bauxite, natural granodiorite and pharmaceuticalsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2002Nicola V. Y. Scarlett The International Union of Crystallography (IUCr) Commission on Powder Diffraction (CPD) has sponsored a round robin on the determination of quantitative phase abundance from diffraction data. The aims of the round robin have been detailed by Madsen et al. [J. Appl. Cryst. (2001), 34, 409,426]. In summary, they were (i) to document the methods and strategies commonly employed in quantitative phases analysis (QPA), especially those involving powder diffraction, (ii) to assess levels of accuracy, precision and lower limits of detection, (iii) to identify specific problem areas and develop practical solutions, (iv) to formulate recommended procedures for QPA using diffraction data, and (v) to create a standard set of samples for future reference. The first paper (Madsen et al., 2001) covered the results of sample 1 (a simple three-phase mixture of corundum, fluorite and zincite). The remaining samples used in the round robin covered a wide range of analytical complexity, and presented a series of different problems to the analysts. These problems included preferred orientation (sample 2), the analysis of amorphous content (sample 3), microabsorption (sample 4), complex synthetic and natural mineral suites, along with pharmaceutical mixtures with and without an amorphous component. This paper forms the second part of the round-robin study and reports the results of samples 2 (corundum, fluorite, zincite, brucite), 3 (corundum, fluorite, zincite, silica flour) and 4 (corundum, magnetite, zircon), synthetic bauxite, natural granodiorite and the synthetic pharmaceutical mixtures (mannitol, nizatidine, valine, sucrose, starch). The outcomes of this second part of the round robin support the findings of the initial study. The presence of increased analytical problems within these samples has only served to exacerbate the difficulties experienced by many operators with the sample 1 suite. The major difficulties are caused by lack of operator expertise, which becomes more apparent with these more complex samples. Some of these samples also introduced the requirement for skill and judgement in sample preparation techniques. This second part of the round robin concluded that the greatest physical obstacle to accurate QPA for X-ray based methods is the presence of absorption contrast between phases (microabsorption), which may prove to be insurmountable in some circumstances. [source] Modern MALDI time-of-flight mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 3 2009Marvin L. Vestal Abstract This paper focuses on development of time-of-flight (TOF) mass spectrometry in response to the invention of matrix-assisted laser desorption/ionization (MALDI). Before this breakthrough ionization technique for nonvolatile molecules, TOF was generally considered as a useful tool for exotic studies of ion properties but was not widely applied to analytical problems. Improved TOF instruments and software that allow the full potential power of MALDI to be applied to difficult biological applications are described. A theoretical approach to the design and optimization of MALDI-TOF instruments for particular applications is presented. Experimental data are provided that are in excellent agreement with theoretical predictions of resolving power and mass accuracy. Data on sensitivity and dynamic range using kilohertz laser rates are also summarized. These results indicate that combinations of high-performance MALDI-TOF and TOF-TOF with off-line high-capacity separations may ultimately provide throughput and dynamic range several orders of magnitude greater than those currently available with electrospray LC-MS and MS-MS. Copyright © 2009 John Wiley & Sons, Ltd. [source] Root dynamics and global change: seeking an ecosystem perspectiveNEW PHYTOLOGIST, Issue 1 2000RICHARD J. NORBY Changes in the production and turnover of roots in forests and grasslands in response to rising atmospheric CO2 concentrations, elevated temperatures, altered precipitation, or nitrogen deposition could be a key link between plant responses and longer-term changes in soil organic matter and ecosystem carbon balance. Here we summarize the experimental observations, ideas, and new hypotheses developed in this area in the rest of this volume. Three central questions are posed. Do elevated atmospheric CO2, nitrogen deposition, and climatic change alter the dynamics of root production and mortality? What are the consequences of root responses to plant physiological processes? What are the implications of root dynamics to soil microbial communities and the fate of carbon in soil? Ecosystem-level observations of root production and mortality in response to global change parameters are just starting to emerge. The challenge to root biologists is to overcome the profound methodological and analytical problems and assemble a more comprehensive data set with sufficient ancillary data that differences between ecosystems can be explained. The assemblage of information reported herein on global patterns of root turnover, basic root biology that controls responses to environmental variables, and new observations of root and associated microbial responses to atmospheric and climatic change helps to sharpen our questions and stimulate new research approaches. New hypotheses have been developed to explain why responses of root turnover might differ in contrasting systems, how carbon allocation to roots is controlled, and how species differences in root chemistry might explain the ultimate fate of carbon in soil. These hypotheses and the enthusiasm for pursuing them are based on the firm belief that a deeper understanding of root dynamics is critical to describing the integrated response of ecosystems to global change. [source] Children, Labour Supply and Child Care: Challenges for Empirical AnalysisTHE AUSTRALIAN ECONOMIC REVIEW, Issue 3 2009Guyonne Kalb The aim of this article is to give an overview of the important issues relating to the labour supply of the primary carer in a household. Child care plays a central role in allowing the primary carer time away from the young children in a household. Therefore, child-care use is a central topic of this article, as well. There are a number of different aspects to child care, such as the price, quality, availability and type of service. This article discusses the analytical problems and challenges, taking Australian data, policy and experience as a focus, but drawing on a wide range of international empirical studies. It reports the results from previous research on child-care use and labour supply and it outlines the areas requiring more study. The focus of the article is on economic research. [source] Some remarks on characterization and application of stationary phases for RP-HPLC determination of biologically important compoundsBIOMEDICAL CHROMATOGRAPHY, Issue 1 2006Sylwia Kowalska Abstract Biologically active compounds such as vitamins, steroids, nucleosides, peptides and proteins play a very important role in coordinating living organism functions. Determination of those substances is indispensable in pathogenesis. Their complex structure and physico-chemical properties cause many analytical problems. Chromatography is the most common technique used in pharmaceutical and biomedical analysis. The interaction between analyte and stationary phase plays a major role in the separation process. The structure of the packing has a significant influence on the results of the separation process. Various types of spectroscopic techniques, such as nuclear magnetic resonance spectroscopy, infrared spectroscopy, fluorescence spectroscopy and photoacoustic spectroscopy can be useful tools for the characterization of packings. Surface area measurements, elemental analysis, thermal analysis and microcalorimetric measurements are also helpful in this field. Part of the paper contains a description of chromatographic tests used for the determination of column properties. The description of the possibilities of surface characterization is not complete, but is focused on the most popular techniques and practical chromatographic tests. All the presented methods made possible the design and quality control of a new generation stationary phases, which are the future of high-performance liquid chromatography. Copyright © 2005 John Wiley & Sons, Ltd. [source] | |||||||||||||