Detection of attomole quantities [correction of quantitites] of DNA targets on gold microelectrodes by electrocatalytic nucleobase oxidation

The electrochemical detection of nucleic acid targets at low concentrations has a number of applications in diagnostics and pharmaceutical research. Self-assembled monolayers of alkanethiol-derivatized oligonucleotides on gold electrodes provide a useful platform for such detectors, and the electrocatalytic oxidation of nucleobases included in the DNA targets is a particularly sensitive method of electrochemical detection. A strategy has been developed for combining these two aspects by substituting either 7,8-dihydro-8-oxoguanine (8G) or 5-aminouridine (5U) into DNA targets. Upon hybridization of targets containing these modified nucleobases, electrocatalytic signals at probe-modified gold electrodes are observed in the presence of Os(bpy)(3)(2+), which oxidizes both 8G and 5U upon oxidation to the Os(III) state. Self-assembled monolayers were prepared on both macro (1.6 mm) and micro (25 microm) gold electrodes using published procedures involving C6-terminated alkanethiol oligonucleotides and mercaptohexanol as the diluent. The extent of electrode modification by the modified probe was assessed using radiolabeling and a standard chronocoulometry method; both approaches gave loading levels within expected ranges ((1-6) x 10(12) molecules/cm(2)). Hybridization of the modified targets where the non-native nucleobase was incorporated by solid-phase synthesis produced electrocatalytic signals from strands that were independently detected using radiolabeling and chronocoulometry. This result was used as a basis to develop an on-electrode amplification scheme where Taq polymerase was used to extend the immobilized DNA probes from solution-phase polymeric templates using modified nucleotriphosphates. This reaction produced an electrode that was modified with extended DNA containing the appropriate modified nucleotide. Radiolabeled nucleotide triphosphates were used to confirm the desired on-electrode DNA synthesis. When these electrodes were cycled in the presence of Os(bpy)(3)(2+), electrocatalytic signals were observed when as little as 40 amol (400 fM) of the desired target was present in the hybridization solution.     

Effects of high-γ-linolenic acid canola oil compared with borage oil on reproduction,growth, and brain and behavioral development in mice

Previous research in rats and mice has suggested that γ-linolenic acid (GLA) derived from borage oil (BO: 23% GLA) may be an appropriate source for increasing levels of long-chain n−6 FA in the developing brain. Recently, transgenic technology has made available a highly enriched GLA seed oil from the canola plant (HGCO: 36% GLA). The first objective of this study was to compare the effects of diets containing equal levels of GLA (23%) from either BO or HGCO on reproduction, pup development, and pup brain FA composition in mice. The second objective was to compare the effects of the HGCO diluted to 23% GLA (GLA-23) with those of undiluted HGCO containing 36% GLA (GLA-36). The diets were fed to the dams prior to conception and throughout pregnancy and lactation, as well as to the pups after weaning. The behavioral development of the pups was measured 12 d after birth, and anxiety in the adult male offspring was assessed using the plus maze. The findings show that despite equivalent levels of GLA, GLA-23 differed from BO in that it reduced pup body weight and was associated with a slight increase in neonatal pup attrition. However, there were no significant effects on pup behavioral development or on performance in the plus maze. An increase in dietary GLA resulted in an increase in brain 20∶4n−6 and 22∶4n−6, with a corresponding decrease in 22∶6n−3. Again, despite their similar levels of GLA, these effects tended to be larger in GLA-23 than in BO. In comparison with GLA-23, GLA-36 had larger effects on growth and brain FA composition but no differences with respect to effects on reproduction and behavioral development. These findings suggest that the HGCO can be used as an alternative source of GLA.     

Application of a breeder genetic algorithm for filter optimization

In this work we are optimizing an adaptive finite impulse response filter applied to the problem of system identification. We are proposing a breeder genetic algorithm (BGA) for performing the parametric search in highly multimoldal landscapes since in this kind of filters there exits epistiasis. The results of BGA were compared to the traditional genetic algorithm, and we found that the BGA was clearly superior (in accuracy) in most of the cases. We used the statistical least mean squared for validating the results. We suggest to hybridized both methods for real world applications.     

Contamination-free continuous flow microfluidic polymerase chain reaction for quantitative and clinical applications

We present a method for performing polymerase chain reaction (PCR) using isolated droplets flowing in an immiscible fluorinated solvent system. Thanks to an optimized control of interfacial properties, we could achieve in this capillary-based system reproducible amplification factors, without any detectable contamination between neighboring droplets. The system is readily amenable to further miniaturization and automation and serves as the first step toward a clinically viable, high-throughput, quantitative continuous flow PCR apparatus.     

Substrate interactions with the nitrogenase active site

The chemical mechanism for biological cleavage of the N(2) triple bond at ambient pressure and temperature has been the subject of intense study for many years. The site of substrate activation and reduction has been localized to a complex cofactor, called FeMo cofactor, yet until now the complexity of the system has denied information concerning exactly where and how substrates interact with the metal-sulfur framework of the active site. In this Account, we describe a combined genetic, biophysical, and biochemical approach that was used to provide direct and detailed information concerning where alternative alkyne substrates interact with FeMo cofactor during catalysis. The relevance and limitations of this work with respect to N(2) binding and reduction also are discussed.     

Comparative Investigation of the Volatile Urinary Profiles in Different <Emphasis Type="Italic">Phodopus</Emphasis> Hamster Species

Stir bar sorptive extraction method was used for investigation of the urinary volatile profiles in male and female Phodopus campbelli and Phodopus sungorus hamsters. Additionally, female Phodopus roborowsky urinary profiles were characterized. A quantitative analytical approach allowed comparisons of 17 selected compounds in urine. Results showed that campbelli and sungorus species show similar urinary volatile profiles for males and females. Differences appeared only in concentrations. Several unique compounds, such as pyrazine derivatives, were found to be gender- and age-specific. P. roborowsky females exhibited a completely different urinary volatile profile from campbelli and sungorus females, featuring a unique set of substituted quinoxalines.     

College Students' Memory for Vocabulary in Their Majors: Evidence for a Nonlinear Relation Between Knowledge and Memory.

The effect of domain knowledge on students' memory for vocabulary terms was investigated. Participants were 142 college students (94 education majors and 48 business majors). The measure of domain knowledge was the number of courses completed in the major. Students recalled three different lists (control, education, and business) of 20 words. Knowledge effects were estimated controlling for academic aptitude, academic achievement, and general memory ability. Domain-specific knowledge consistently predicted recall, above and beyond the effect of these control variables. Moreover, nonlinear models better represented the relation between knowledge and memory, with very similar functions predicting recall in both knowledge domains. Specifically, early in the majors more classes corresponded with increased memory performance, but a plateau period, when more classes did not result in higher recall, was evident for both majors. Longitudinal research is needed to explore at what point in learning novices' performance begins to resemble experts' performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Towards integrated catchment management: increasing the dialogue between scientists,policy‐makers and stakeholders

The aim of the Hydrology for the Environment, Life and Policy (HELP) project is to strengthen the role and inputs of the scientific community in the integrated catchment management process. Water resources management in the 21st century requires a radical reorientation and an effective dialogue between decision‐makers, stakeholders and the scientific water community. This paper offers a skeleton worldview as a starting point for that dialogue by bringing together key issues as identified by water resource experts from different disciplines. Experiences from all over the world demonstrate the need for multistakeholder advocacy and the importance of compromise‐building mechanisms. Water law defines the rules of the game and provides a necessary framework for policy and its execution. However, there must be adequate social acceptance and active compliance, otherwise the formal rules and administrative regulation will not be perceived as legitimate and ultimately could prove ineffective. The challenge now is to create management systems where the formal decision‐makers interact with relevant members of the scientific community, users and other stakeholders for a coordinated approach that successfully orchestrates water uses towards internal compatibility. Integrated water resources management is essential for securing a proper overview of all the activities that depend on the same resource—the precipitation over the basin—and which are internally linked by the mobility of water from the water divide to the river mouth.     

On being ethical in legal places.

Comments that many ethical pitfalls may await psychologists who participate as expert witnesses in the legal process. This article describes the ethical problems and examines their origin in light of important differences in purpose between psychological practice and legal process. Special attention is given to problems of objectivity in the assessment process, ethical issues in the interpretation of data in the courtroom, and the client's psychological welfare. Suggestions for maintaining ethical practice in the role of expert witness are provided. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)