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Selection System (selection + system)
Selected AbstractsA Novel Genetic Selection System for Improved Enantioselectivity of Bacillus subtilis Lipase ACHEMBIOCHEM, Issue 7 2008Ykelien L. Boersma Dr. Abstract In directed evolution experiments, success often depends on the efficacy of screening or selection methods. Genetic selections have proven to be extremely valuable for evolving enzymes with improved catalytic activity, improved stability, or with altered substrate specificity. In contrast, enantioselectivity is a difficult parameter to select for. In this study, we present a successful strategy that not only selects for catalytic activity, but for the first time also for enantioselectivity, as demonstrated by the selection of Bacillus subtilis lipase A variants with inverted and improved enantioselectivity. A lipase mutant library in an aspartate auxotroph Escherichia coli was plated on minimal medium that was supplemented with the aspartate ester of the desired enantiomer (S)-(+)-1,2- O -isopropylidene- sn -glycerol. To inhibit growth of less enantioselective variants, a covalently binding phosphonate ester of the opposite (R)-(,)-1,2- O -isopropylidene- sn -glycerol enantiomer was added as well. After three selection rounds in which the selection pressure was increased by raising the phosphonate ester concentration, a mutant was selected with an improved enantioselectivity increased from an ee of ,29.6,% (conversion 23.4,%) to an ee of +73.1,% (conversion 28.9,%) towards the (S)-(+)-enantiomer. Interestingly, its amino acid sequence showed that the acid of the catalytic triad had migrated to a position further along the loop that connects ,7 and ,E; this shows that the position of the catalytic acid is not necessarily conserved in this lipase. [source] Acoustic microfluidic chip technology to facilitate automation of phage display selectionFEBS JOURNAL, Issue 22 2008Jonas Persson Modern tools in proteomics require access to large arrays of specific binders for use in multiplex array formats, such as microarrays, to decipher complex biological processes. Combinatorial protein libraries offer a solution to the generation of collections of specific binders, but unit operations in the process to isolate binders from such libraries must be automatable to ensure an efficient procedure. In the present study, we show how a microfluidic concept that utilizes particle separation in an acoustic force field can be used to efficiently separate antigen-bound from unbound members of such libraries in a continuous flow format. Such a technology has the hallmarks for incorporation in a fully automated selection system for the isolation of specific binders. [source] Selecting Predictor Subsets: Considering validity and adverse impactINTERNATIONAL JOURNAL OF SELECTION AND ASSESSMENT, Issue 3 2010Wilfried De Corte The paper proposes a procedure for designing Pareto-optimal selection systems considering validity, adverse impact and constraints on the number of predictors from a larger subset that can be included in an operational selection system. The procedure determines Pareto-optimal composites of a given maximum size thereby solving the dual task of identifying the predictors that will be included in the reduced set and determining the weights with which the retained predictors will be combined to the composite predictor. Compared with earlier proposals, the simultaneous consideration of both tasks makes it possible to combine several strategies for reducing adverse impact in a single procedure. In particular, the present approach allows integrating (a) investigating a large number of possible predictors (such as multitest battery of ability tests, or a collection of ability and nonability measures); (b) explicit predictor weighting within feasible test procedures of a given limited size. [source] Restoring Equity or Introducing Bias?JOURNAL OF APPLIED SOCIAL PSYCHOLOGY, Issue 7 2006A Contingency Model of Attitudes Toward Affirmative Action Programs We developed a model to explain how an individual's attitude toward the group targeted by affirmative action impacts support for the program. In this model, attitude toward the targeted group influences the extent to which an individual perceives discrimination to be responsible for workforce disparities. Perceived discrimination affects fairness judgments of affirmative action programs with the effect contingent on the extent to which the remedy involves preferential treatment. To test this, participants were told about the selection system in a company in which minorities were underrepresented. Participants evaluated the extent to which they believed that discrimination occurs in the hiring process and 3 possible remedies. Results supported attitudes toward the targeted minority group as an antecedent of perceived discrimination and found that the amount of perceived discrimination was negatively related to fairness judgments of opportunity enhancement programs, but positively related to evaluations of programs that involved preferential treatment. Fairness judgments were positively related to support for all 3 affirmative action programs. [source] Becoming an undercover police officer: a note on fairness perceptions, behavior, and attitudes,JOURNAL OF ORGANIZATIONAL BEHAVIOR, Issue 4 2003Suzanne J. Farmer Reactions to an undercover police officer selection system were analyzed for 271 officers. Officers given undercover assignments had higher procedural justice perceptions and outcome satisfaction than others awaiting assignment in a qualified applicant pool. Procedural and distributive justice perceptions were subsequently related to the undercover officer's job performance, job satisfaction, and organizational commitment. Copyright © 2003 John Wiley & Sons, Ltd. [source] ENTRY-LEVEL POLICE CANDIDATE ASSESSMENT CENTER: AN EFFICIENT TOOL OR A HAMMER TO KILL A FLY?PERSONNEL PSYCHOLOGY, Issue 4 2002KOBI DAYAN The study examined the validity of the assessment center (AC) as a selection process for entry-level candidates to die police and its unique value beyond cognitive ability tests. The sample included 712 participants who responded to personality and cognitive ability testing (CAT), and underwent an AC procedure. AC results included the overall assessment rating (OAR) and peer evaluation (PE). Seven criterion measures were collected for 585 participants from a training stage and on-the-job performance. Results showed that the selection system was valid. Findings yielded significant unique validities of OAR and PE beyond CAT and of PE beyond OAR even after corrections for restriction of range. Results support the use of ACs for entry-level candidates. [source] Biodegradation of atrazine in transgenic plants expressing a modified bacterial atrazine chlorohydrolase (atzA) genePLANT BIOTECHNOLOGY JOURNAL, Issue 5 2005Lin Wang Summary Atrazine is one of the most widely used herbicides in the USA. Atrazine chlorohydrolase (AtzA), the first enzyme in a six-step pathway leading to the mineralization of atrazine in Gram-negative soil bacteria, catalyses the hydrolytic dechlorination and detoxification of atrazine to hydroxyatrazine. In this study, we investigated the potential use of transgenic plants expressing atzA to take up, dechlorinate and detoxify atrazine. Alfalfa, Arabidopsis thaliana and tobacco were transformed with a modified bacterial atzA gene, p -atzA, under the control of the cassava vein mosaic virus promoter. All transgenic plant species actively expressed p -atzA and grew over a wide range of atrazine concentrations. Thin layer chromatography analyses indicated that in planta expression of p -atzA resulted in the production of hydroxyatrazine. Hydroponically grown transgenic tobacco and alfalfa dechlorinated atrazine to hydroxyatrazine in leaves, stems and roots. Moreover, p -atzA was found to be useful as a conditional-positive selection system to isolate alfalfa and Arabidopsis transformants following Agrobacterium -mediated transformation. Our work suggests that the in planta expression of p -atzA may be useful for the development of plants for the phytoremediation of atrazine-contaminated soils and soil water, and as a marker gene to select for the integration of exogenous DNA into the plant genome. [source] pFARs, Plasmids free of antibiotic resistance markers, display high-level transgene expression in muscle, skin and tumour cellsTHE JOURNAL OF GENE MEDICINE, Issue 4 2010Corinne Marie Abstract Background Nonviral gene therapy requires a high yield and a low cost production of eukaryotic expression vectors that meet defined criteria such as biosafety and quality of pharmaceutical grade. To fulfil these objectives, we designed a novel antibiotic-free selection system. Methods The proposed strategy relies on the suppression of a chromosomal amber mutation by a plasmid-borne function. We first introduced a nonsense mutation into the essential Escherichia coli thyA gene, resulting in thymidine auxotrophy. The bacterial strain was optimized for the production of small and novel plasmids free of antibiotic resistance markers (pFARs) and encoding an amber suppressor t-RNA. Finally, the potentiality of pFARs as eukaryotic expression vectors was assessed by monitoring luciferase activities after electrotransfer of LUC-encoding plasmids into various tissues. Results The introduction of pFARs into the optimized bacterial strain restored normal growth to the auxotrophic mutant and allowed an efficient production of monomeric supercoiled plasmids. The electrotransfer of LUC-encoding pFAR into muscle led to high luciferase activities, demonstrating an efficient gene delivery. In transplanted tumours, transgene expression levels were superior after electrotransfer of the pFAR derivative compared to a plasmid carrying a kanamycin resistance gene. Finally, in skin, whereas luciferase activities decreased within 3 weeks after intradermal electrotransfer of a conventional expression vector, sustained luciferase expression was observed with the pFAR plasmid. Conclusions Thus, we have designed a novel strategy for the efficient production of biosafe plasmids and demonstrated their potentiality for nonviral gene delivery and high-level transgene expression in several tissues. Copyright © 2010 John Wiley & Sons, Ltd. [source] AL03 ADVERSE EVENTS: OUR RESPONSIBILITY FOR REPORTING, REVIEWING AND RESPONDINGANZ JOURNAL OF SURGERY, Issue 2009J. Collins The sustained production of competent surgeons in sufficient numbers to meet the increasing needs of society commences with recruitment and selection of the most able medical graduates. As the process begins through self-selection, accurate information must be readily available to enable these graduates make an informed judgement on their career choice. Each surgical discipline aspires to use best practice selection in order to identify those who have the potential to acquire the necessary standard of technical and non technical skills and attributes required to practice as a surgeon. A selection system must rank applicants effectively and be reliable, valid, fair, defensible, cost effective and feasible. Best practice selection commences with an analysis of the relevant knowledge, skills, abilities and attitudes associated with successful performance in the particular target job. This information is used to construct a person specification in order to identify selection criteria at a level appropriate for entry to training. Selection methods are then chosen which will best elicit measurable applicant behaviour related to these selection criteria. A number of selection methods are used which include structured references, curriculum vitae and interviews. Other methods available although rarely used include tests of mental ability, aptitude tests and personality inventories. More recently selection or assessment centres (a selection method, not a place) involving a combination of selection techniques such as written exercises, interviews and work simulations have been shown to be highly effective. Eligibility criteria for application (long listing), shortlising for interview, scoring of items within each selection method and overall % weighting for each method are important variables in the selection process. [source] Texas Children's Hospital makes leadership development a core business strategyGLOBAL BUSINESS AND ORGANIZATIONAL EXCELLENCE, Issue 3 2007Linda Aldred Even an admirable culture can have its dark side, and convincing current leaders that leadership is the problem is a task best not taken lightly. Texas Children's Hospital rose to the challenge with creative ways for building an enduring commitment to change, and for infusing leadership development into leaders' psyches and practices. Guiding principles and success profiles now link mission and values with the day-to-day expectations for employees, and are fully integrated into measurement, performance management, and selection systems. Powerful new tools and resources are helping build leadership competencies at all levels. Lower turnover and greater employee satisfaction are just the first indicators of the success of the initiative. © 2007 Wiley Periodicals, Inc. [source] Selecting Predictor Subsets: Considering validity and adverse impactINTERNATIONAL JOURNAL OF SELECTION AND ASSESSMENT, Issue 3 2010Wilfried De Corte The paper proposes a procedure for designing Pareto-optimal selection systems considering validity, adverse impact and constraints on the number of predictors from a larger subset that can be included in an operational selection system. The procedure determines Pareto-optimal composites of a given maximum size thereby solving the dual task of identifying the predictors that will be included in the reduced set and determining the weights with which the retained predictors will be combined to the composite predictor. Compared with earlier proposals, the simultaneous consideration of both tasks makes it possible to combine several strategies for reducing adverse impact in a single procedure. In particular, the present approach allows integrating (a) investigating a large number of possible predictors (such as multitest battery of ability tests, or a collection of ability and nonability measures); (b) explicit predictor weighting within feasible test procedures of a given limited size. [source] Procedural Justice and Perceptions of Fairness in Selection PracticeINTERNATIONAL JOURNAL OF SELECTION AND ASSESSMENT, Issue 3 2000Lynette Harris Demonstrating procedural justice through a focus on the psychometric job-related approach to selection continues to be the most effective means for employers to meet legal requirements and potential claims of unfair treatment. A study of selection practice in a large local UK City Council reports how a structured, highly ,job-focused' approach can result in negative perceptions about the fairness of the process, its outcomes and effectiveness. Its findings reveal an organizational dilemma , how to develop selection systems that are sufficiently robust in terms of demonstrating maximum procedural fairness and objectivity to withstand potential litigation but are sufficiently flexible to accommodate those other factors which influence individual perceptions of fairness. It considers the future of the highly structured approach in the light of pressures to develop selection processes which can meet the needs of rapidly changing organizational structures as well the expansion of anti-discrimination legislation and litigation. [source] Bioengineered ,golden' indica rice cultivars with ,-carotene metabolism in the endosperm with hygromycin and mannose selection systemsPLANT BIOTECHNOLOGY JOURNAL, Issue 2 2003Karabi Datta Summary Vitamin-A deficiency (VAD) is a major malnutrition problem in South Asia, where indica rice is the staple food. Indica-type rice varieties feed more than 2 billion people. Hence, we introduced a combination of transgenes using the biolistic system of transformation enabling biosynthesis of provitamin A in the endosperm of several indica rice cultivars adapted to diverse ecosystems of different countries. The rice seed-specific glutelin promoter (Gt-1 P) was used to drive the expression of phytoene synthase (psy), while lycopene ,-cyclase (lcy) and phytoene desaturase (crtI), fused to the transit peptide sequence of the pea-Rubisco small subunit, were driven by the constitutive cauliflower mosaic virus promoter (CaMV35S P). Transgenic plants were recovered through selection with either CaMV35S P driven hph (hygromycin phosphotransferase) gene or cestrum yellow leaf curling virus promoter (CMP) driven pmi (phophomannose isomerase) gene. Molecular and biochemical analyses demonstrated stable integration and expression of the transgenes. The yellow colour of the polished rice grain evidenced the carotenoid accumulation in the endosperm. The colour intensity correlated with the estimated carotenoid content by spectrophotometric and HPLC analysis. Carotenoid level in cooked polished seeds was comparable (with minor loss of xanthophylls) to that in non-cooked seeds of the same transgenic line. The variable segregation pattern in T1 selfing generation indicated single to multiple loci insertion of the transgenes in the genome. This is the first report of using nonantibiotic pmi driven by a novel promoter in generating transgenic indica rice for possible future use in human nutrition. [source] | |||||||||||||||||||