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Analytical Strategy (analytical + strategy)
Selected AbstractsAnalytical strategies for identifying drug metabolitesMASS SPECTROMETRY REVIEWS, Issue 3 2007Chandra Prakash Abstract With the dramatic increase in the number of new chemical entities (NCEs) arising from combinatorial chemistry and modern high-throughput bioassays, novel bioanalytical techniques are required for the rapid determination of the metabolic stability and metabolites of these NCEs. Knowledge of the metabolic site(s) of the NCEs in early drug discovery is essential for selecting compounds with favorable pharmacokinetic credentials and aiding medicinal chemists in modifying metabolic "soft spots". In development, elucidation of biotransformation pathways of a drug candidate by identifying its circulatory and excretory metabolites is vitally important to understand its physiological effects. Mass spectrometry (MS) and nuclear magnetic resonance (NMR) have played an invaluable role in the structural characterization and quantification of drug metabolites. Indeed, liquid chromatography (LC) coupled with atmospheric pressure ionization (API) MS has now become the most powerful tool for the rapid detection, structure elucidation, and quantification of drug-derived material within various biological fluids. Often, however, MS alone is insufficient to identify the exact position of oxidation, to differentiate isomers, or to provide the precise structure of unusual and/or unstable metabolites. In addition, an excess of endogenous material in biological samples often suppress the ionization of drug-related material complicating metabolite identification by MS. In these cases, multiple analytical and wet chemistry techniques, such as LC-NMR, enzymatic hydrolysis, chemical derivatization, and hydrogen/deuterium-exchange (H/D-exchange) combined with MS are used to characterize the novel and isomeric metabolites of drug candidates. This review describes sample preparation and introduction strategies to minimize ion suppression by biological matrices for metabolite identification studies, the application of various LC-tandem MS (LC-MS/MS) techniques for the rapid quantification and identification of drug metabolites, and future trends in this field. © 2007 Wiley Periodicals, Inc., Mass Spec Rev [source] If We Produce Discrepancies, Then How?JOURNAL OF APPLIED SOCIAL PSYCHOLOGY, Issue 9 2010Testing a Computational Process Model of Positive Goal Revision Within the self-regulation literature on goals, both discrepancy reduction and discrepancy production are considered important theoretical and practical processes. Yet, discrepancy production has only been examined in a limited number of goal-striving contexts, and the analytical strategies employed (e.g., difference scores) are difficult to interpret. This study extends discrepancy production research to multiple goal contexts where the goals are in conflict. Computational modeling and an organizational simulation were used to test a control theory explanation of discrepancy production. The occurrence of discrepancy production in the computational model and participants was assessed using hierarchical linear modeling. Comparing the data from the computational model with participants' data indicated a good fit. Implications of the findings and methods are discussed. [source] Distinguishing N -oxide and hydroxyl compounds: impact of heated capillary/heated ion transfer tube in inducing atmospheric pressure ionization source decompositionsJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2004Dilrukshi M. Peiris Abstract In the pharmaceutical industry, a higher attrition rate during the drug discovery process means a lower drug failure rate in the later stages. This translates into shorter drug development time and reduced cost for bringing a drug to market. Over the past few years, analytical strategies based on liquid chromatography/mass spectrometry (LC/MS) have gone through revolutionary changes and presently accommodate most of the needs of the pharmaceutical industry. Among these LC/MS techniques, collision induced dissociation (CID) or tandem mass spectrometry (MS/MS and MSn) techniques have been widely used to identify unknown compounds and characterize metabolites. MS/MS methods are generally ineffective for distinguishing isomeric compounds such as metabolites involving oxygenation of carbon or nitrogen atoms. Most recently, atmospheric pressure ionization (API) source decomposition methods have been shown to aid in the mass spectral distinction of isomeric oxygenated (N -oxide vs hydroxyl) products/metabolites. In previous studies, experiments were conducted using mass spectrometers equipped with a heated capillary interface between the mass analyzer and the ionization source. In the present study, we investigated the impact of the length of a heated capillary or heated ion transfer tube (a newer version of the heated capillary designed for accommodating orthogonal API source design) in inducing for-API source deoxygenation that allows the distinction of N -oxide from hydroxyl compounds. 8-Hydroxyquinoline (HO-Q), quinoline- N -oxide (Q-NO) and 8-hydroxyquinoline- N -oxide (HO-Q-NO) were used as model compounds on three different mass spectrometers (LCQ Deca, LCQ Advantage and TSQ Quantum). Irrespective of heated capillary or ion transfer tube length, N -oxides from this class of compounds underwent predominantly deoxygenation decomposition under atmospheric pressure chemical ionization conditions and the abundance of the diagnostic [M + H , O]+ ions increased with increasing vaporizer temperature. Furthermore, the results suggest that in API source decompostion methods described in this paper can be conducted using mass spectrometers with non-heated capillary or ion transfer tube API interfaces. Because N-oxides can undergo in-source decomposition and interfere with quantitation experiments, particular attention should be paid when developing API based bioanalytical methods. Copyright © 2004 John Wiley & Sons, Ltd. [source] Mass spectrometry strategies applied to the characterization of proline-rich peptides from secretory parotid granules of pig (Sus scrofa)JOURNAL OF SEPARATION SCIENCE, JSS, Issue 3 2008Chiara Fanali Abstract Basic proline-rich proteins (bPRPs) are a class of proteins widely present in saliva of humans and other mammals. They are synthesized as preproproteins and enzymatically cleaved into small peptides before secretion from the salivary glands. Recently, we characterized two proline-rich peptides (SP-A and SP-B) in parotid secretory granules of pig (Sus Scrofa) that are derived from three isoforms of a PRP proprotein (Swiss-Prot data bank: Q95JC9-1, Q95JC9-2 and Q95JC9-3). Together the coding regions for SP-A and SP-B, which are repeated many times, account for 52,70% of the coding regions of the PRP proproteins. This study was undertaken to identify peptides encoded by unassigned regions of the PRP proproteins. RP-HPLC-ESI-IT-MS analysis of enriched granule preparations from pig parotid glands by two different analytical strategies identified ten new proline-rich peptides derived from the three proproteins. Together with the coding regions for SP-A and SP-B already identified it was possible to assign 68,75% of the proproteins coding regions. The peptide sequences indicated a number of unusual proteolytic cleavage sites suggesting the presence of unknown proprotein convertases. [source] Mass spectrometric determination of insulins and their degradation products in sports drug testingMASS SPECTROMETRY REVIEWS, Issue 1 2008Mario Thevis Abstract Insulins' anabolic and anti-catabolic properties have supposedly led to its misuse in sport. Hence, doping control assays were developed to allow the unequivocal identification of synthetic insulin analogs and metabolic products derived from human insulin and its artificial counterparts in urine and plasma specimens. Analyses were based on immunoaffinity purification and subsequent characterization of target analytes by top-down sequencing-based approaches, which were conducted with hybrid tandem mass spectrometers that consisted of either quadrupole-linear ion trap or linear ion trap-orbitrap analyzers. Diagnostic product ions and analytical strategies are presented and discussed in light of the need to unambiguously identify misused drugs in urine and plasma specimens for doping control. © 2007 Wiley Periodicals, Inc., Mass Spec Rev 27:35,50, 2008 [source] Characterisation of organellar proteomes: A guide to subcellular proteomic fractionation and analysisPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 21 2006Edwin Ho Abstract Subcellular fractionation is being widely used to increase our understanding of the proteome. Fractionation is often coupled with 2-DE, thus allowing the visualisation of proteins and their subsequent identification and characterisation by MS. Whilst this strategy should be effective, to date, there has been little or no consideration given to differences in the mass, pI, hydropathy or abundance of proteins in the organelles and how analytical strategies can be tailored to match the idiosyncrasies of proteins in each particular compartment. To address this, we analysed 3962 Saccharomyces cerevisiae proteins, previously localised to one or more of 22 subcellular compartments. Different compartments showed significantly different distributions of protein pI and hydropathy. Mitochondrial and ER proteins showed the most dramatic differences to other organelles, in their protein pIs and hydropathy, respectively. We show that organelles can be clustered by similarities in these physicochemical protein characteristics. Interestingly, the distribution of protein abundance was also significantly different between many organelles. Our results show that to fully explore subcellular fractions of the proteome, specific analytical strategies should be employed. We outline strategies for all 22 subcellular compartments. [source] The abuse of diuretics as performance-enhancing drugs and masking agents in sport doping: pharmacology, toxicology and analysisBRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2010Amy B Cadwallader Diuretics are drugs that increase the rate of urine flow and sodium excretion to adjust the volume and composition of body fluids. There are several major categories of this drug class and the compounds vary greatly in structure, physicochemical properties, effects on urinary composition and renal haemodynamics, and site and mechanism of action. Diuretics are often abused by athletes to excrete water for rapid weight loss and to mask the presence of other banned substances. Because of their abuse by athletes, diuretics have been included on The World Anti-Doping Agency's (WADA) list of prohibited substances; the use of diuretics is banned both in competition and out of competition and diuretics are routinely screened for by anti-doping laboratories. This review provides an overview of the pharmacology and toxicology of diuretics and discusses their application in sports. The most common analytical strategies currently followed by the anti-doping laboratories accredited by the WADA are discussed along with the challenges laboratories face for the analysis of this diverse class of drugs. [source] INDUSTRIAL SHIFT, POLARIZED LABOR MARKETS AND URBAN VIOLENCE: MODELING THE DYNAMICS BETWEEN THE ECONOMIC TRANSFORMATION AND DISAGGREGATED HOMICIDE,CRIMINOLOGY, Issue 3 2004KAREN F. PARKER Industrial restructuring marks the removal of a manufacturing and production-based economy in urban areas, which had served as a catalyst in concentrating disadvantage and polarizing labor markets since the 1970s. Although scholars have established a relationship between concentrated disadvantage , poverty, joblessness, racial residential segregation , and urban violence in cross-sectional studies, this literature has yet to estimate whether economic restructuring contributed to the change in urban homicide over time. Modeling this relationship requires an analytical strategy that incorporates specific indicators of (race and gender) polarized labor markets, separate from indicators of urban disadvantage, on disaggregated homicides while taking into account the growing dependency of urban cities on formal social control (via police presence and rise in incarceration). In this study I provide a theoretical rationale for linking industrial restructuring to urban homicide. Using a multivariate strategy to capture the shift in labor market forces and disaggregated homicides from 1980 to 1990, I also estimate the impact of this relationship. The results provide evidence of the industrial ship and documents both the decline in Manufacturing jobs for black males and black females and a growth in the service sector opportunities for white males only. I also find that industrial restructuring had a unique impact on disaggregated homicide beyond what has previously been established in cross-sectional studies. [source] Twilight Institutions: Public Authority and Local Politics in AfricaDEVELOPMENT AND CHANGE, Issue 4 2006Christian Lund ABSTRACT Public authority does not always fall within the exclusive realm of government institutions; in some contexts, institutional competition is intense and a range of ostensibly a-political situations become actively politicized. Africa has no shortage of institutions which attempt to exercise public authority: not only are multiple layers and branches of government institutions present and active to various degrees, but so-called traditional institutions bolstered by government recognition also vie for public authority, and new emerging institutions and organizations also enter the field. The practices of these institutions make concepts such as public authority, legitimacy, belonging, citizenship and territory highly relevant. This article proposes an analytical strategy for the understanding of public authority in such contexts. It draws on research from anthropologists, geographers, political scientists and social scientists working on Africa, in an attempt to explore a set of questions related to a variety of political practices and their institutional ramifications. [source] Single nucleotide polymorphisms in succinate dehydrogenase subunits and citrate synthase genes: association results for impaired spermatogenesisINTERNATIONAL JOURNAL OF ANDROLOGY, Issue 3 2007Sandra Bonache Abstract Evaluation of the possible implication of the SDHA, SDHB, SDHC, SDHD and CS genes in non-obstructive male infertility was performed on the basis that sperm concentration in the ejaculate has been previously correlated with nuclear-encoded mitochondrial enzyme activities (the four subunits of succinate dehydrogenase/complex II of the respiratory chain and citrate synthase). We performed an exhaustive analysis of the five genes for the presence of sequence variants that could be associated with impairment of sperm production. blastn searches in the genomic sequence NCBI database evidenced the presence of highly homologous sequences elsewhere on the genome that can interfere with polymerase chain reaction experiments. Therefore, a careful design of the analytical strategy to search for sequence variants was performed. In this report, we provide primer sequences that allowed selective amplification of coding and immediate flanking regions of the five genes. Fifty-five sequence variations in the five genes were identified in infertile and normozoospermic fertile individuals as controls and only one of them (SDHA c.456+32G>A) showed significant genotype association with impairment of sperm production. Moreover, new single nucleotide polymorphisms identified should be useful in future association studies for other human diseases related to nuclear-encoded genes, leading to mitochondrial respiratory chain activity impairment revealing the physiological role of these genes. [source] Balancing robust quantification and identification for iTRAQ: Application of UHR-ToF MSPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 11 2010Saw Yen Ow Abstract iTRAQ reagents allow the simultaneous multiplex identification and quantification of a large number of proteins. Success depends on effective peptide fragmentation in order to generate both peptide sequence ions (higher mass region, 150,2200,m/z) and reporter ions (low mass region, 113,121,m/z) for protein identification and relative quantification, respectively. After collision-induced dissociation, the key requirements to achieve a good balance between the high and low m/z ions are effective ion transmission and detection across the MS/MS mass range, since the ion transmission of the higher m/z range competes with that of the low m/z range. This study describes an analytical strategy for the implementation of iTRAQ on maXis UHR-Qq-ToF instruments, and discusses the impact of adjusting the MS/MS ion transmission parameters on the quality of the overall data sets. A technical discussion highlights a number of maXis-specific parameters, their impact of quantification and identification, and their cross-interactions. [source] A general precursor ion-like scanning mode on quadrupole-TOF instruments compatible with chromatographic separationPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 1 2006Ricarda Niggeweg Abstract MS protein identification and quantitation are key proteomic techniques in biological research. Besides identification of proteins, MS is used increasingly to characterize secondary protein modifications. This often requires trimming the analytical strategy to a specific type of modification. Direct analysis of protein modifications in proteomic samples is often hampered by the limited dynamic range of current analytical tools. Here we present a fast, sensitive, multiplexed precursor ion scanning mode , implemented on a quadrupole-TOF instrument , that allows the specific detection of any modified peptide or molecule that reveals itself by a specific fragment ion or pattern of fragment ions within a complex proteomic sample. The high mass accuracy of the TOF mass spectrometer is available for the marker ion specificity and the precursor ion mass determination. The method is compatible with chromatographic separation. Fragment ions and intact molecular ions are acquired quasi-simultaneously by continuously switching the collision energy between elevated and low levels. Using this technique many secondary modifications can be analyzed in parallel; however, the number of peptides carrying a specific modification that can be analyzed successfully is limited by the chromatographic resolution or, more generally, by the depth of the resolved time domain. [source] Theory, Stylized Heuristic or Self-Fulfilling Prophecy?PUBLIC ADMINISTRATION, Issue 1 2004The Status of Rational Choice Theory in Public Administration Rational choice is intimately associated with positivism and naturalism, its appeal to scholars of public administration lying in its ability to offer a predictive science of politics that is parsimonious in its analytical assumptions, rigorous in its deductive reasoning and overarching in its apparent applicability. In this paper I re-examine the ontology and epistemology which underpins this distinctive approach to public administration, challenging the necessity of the generally unquestioned association between rational choice and both positivism and naturalism. Rational choice, I contend, can only defend its claim to offer a predictive science of politics on the basis of an ingenious, paradoxical, and seldom acknowledged structuralism and a series of analytical assumptions incapable of capturing the complexity and contingency of political systems. I argue that analytical parsimony, though itself a condition of naturalism, is in fact incompatible with the deduction of genuinely explanatory/causal inferences. This suggests that the status of rational choice as an explanatory/predictive theory needs to be reassessed. Yet this is no reason to reject rational choice out of hand. For, deployed not as a theory in its own right, but as a heuristic analytical strategy for exploring hypothetical scenarios, it is a potent and powerful resource in post-positivist public administration. [source] Comprehensive plasma-screening for known and unknown substances in doping controlsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2010Andreas Thomas Occasionally, doping analysis has been recognized as a competitive challenge between cheating sportsmen and the analytical capabilities of testing laboratories. Both have made immense progress during the last decades, but obviously the athletes have the questionable benefit of frequently being able to switch to new, unknown and untested compounds to enhance their performance. Thus, as analytical counteraction and for effective drug testing, a complementary approach to classical targeted methods is required in order to implement a comprehensive screening procedure for known and unknown xenobiotics. The present study provides a new analytical strategy to circumvent the targeted character of classical doping controls without losing the required sensitivity and specificity. Using 50,µL of plasma only, the method potentially identifies illicit drugs in low ng/mL concentrations. Plasma provides the biological fluid with the circulating, unmodified xenobiotics; thus the identification of unknown compounds is facilitated. After a simple protein precipitation, liquid chromatographic separation and subsequent detection by means of high resolution/high accuracy orbitrap mass spectrometry, the procedure enables the determination of numerous compounds from different classes prohibited by the World Anti-Doping Agency (WADA). A new hyphenated mass spectrometry technology was employed without precursor ion selection for higher collision energy dissociation (HCD) fragmentation experiments. Thus the mass spectra contained all the desired information to identify unknown substances retrospectively. The method was validated for 32 selected model compounds for qualitative purposes considering the parameters specificity, selectivity, limit of detection (<0.1,10,ng/mL), precision (9,28%), robustness, linearity, ion suppression and recovery (80,112%). In addition to the identification of unknown compounds, the plasma samples were simultaneously screened for known prohibited targets. Copyright © 2010 John Wiley & Sons, Ltd. [source] Different patterns of associations with anti,citrullinated protein antibody,positive and anti,citrullinated protein antibody,negative rheumatoid arthritis in the extended major histocompatibility complex regionARTHRITIS & RHEUMATISM, Issue 1 2009Bo Ding Objective To identify additional variants in the major histocompatibility complex (MHC) region that independently contribute to risk in 2 disease subsets of rheumatoid arthritis (RA) defined according to the presence or absence of antibodies to citrullinated protein antigens (ACPAs). Methods In a multistep analytical strategy using unmatched as well as matched analyses to adjust for HLA,DRB1 genotype, we analyzed 2,221 single-nucleotide polymorphisms (SNPs) spanning 10.7 Mb, from 6p22.2 to 6p21.31, across the MHC. For ACPA-positive RA, we analyzed samples from the Swedish Epidemiological Investigation of Rheumatoid Arthritis (EIRA) and the North American Rheumatoid Arthritis Consortium (NARAC) studies (totaling 1,255 cases and 1,719 controls). For ACPA-negative RA, we used samples from the EIRA study (640 cases and 670 controls). Plink and SAS statistical packages were used to conduct all statistical analyses. Results A total of 299 SNPs reached locus-wide significance (P < 2.3 × 10,5) for ACPA-positive RA, whereas surprisingly, no SNPs reached this significance for ACPA-negative RA. For ACPA-positive RA, we adjusted for known DRB1 risk alleles and identified additional independent associations with SNPs near HLA,DPB1 (rs3117213; odds ratio 1.42 [95% confidence interval 1.17,1.73], Pcombined = 0.0003 for the strongest association). Conclusion There are distinct genetic patterns of MHC associations in the 2 disease subsets of RA defined according to ACPA status. HLA,DPB1 is an independent risk locus for ACPA-positive RA. We did not identify any associations with SNPs within the MHC for ACPA-negative RA. [source] Rethinking Nationality in the Context of GlobalizationCOMMUNICATION THEORY, Issue 1 2004Stephen B. Crofts Wiley Globalization poses a significant challenge to the nation as a social form and consequently to theories that rely on nationality as a conceptual category. This article reviews a range of approaches to the conceptualization of nationality within mass communication, media theory, and cultural studies: mainstream nation-based theories, critical nation-based theories, relational theories, globalization theories, and contextualist theories. An analytical strategy is then proposed within which nationality is conceptualized as one particular logic among others that organize economic, political, technological, and cultural territories and flows. [source] | ||||||||||||||||