Phosphomolybdenum Blue Detection – A Review of Characteristics, Achievements, Challenges and Future Prospects

Phosphate detection in the environment (especially, water bodies) is very essential in view of its consequent pollution effects on eutrophication. Continuous monitoring of phosphate concentration (and phosphorus compounds in general) in water samples has been based on phosphomolybdenum blue formation coupled with spectrophotometric detection. Continu­ous flow injection analyses (FIA) are well known to present numerous advantages over batch methods. Furthermore, the development of on-chip micro-channel analytical (μFIA) systems begun and have gained much attention within the last two decades in view of the striking advantages over conventional FIA techniques. This paper reviews published information on detection of phosphomolybdenum blue in conventional systems as well as on micro-chip. It reports on the challenges encountered (interference from other complex anions), the achieve­ments made so far (intereference removal by electrokinetic separation) and what the future holds (simultaneous determination)

Black Girls Speak STEM: Counterstories of Informal and Formal Learning Experiences

This study presents the interpretations and perceptions of Black girls who participated in I AM STEM – a community-based informal science, technology, engineering, and mathematics (STEM) program. Using narrative inquiry, participants generated detailed accounts of their informal and formal STEM learning experiences. Critical race methodology informed this research to portray the dynamic and complex experiences of girls of color, whose stories have historically been silenced and misrepresented. The data sources for this qualitative study included individual interviews, student reflection journals, samples of student work, and researcher memos, which were triangulated to produce six robust counterstories. Excerpts of the counterstories are presented in this article. The major findings of this research revealed that I AM STEM ignited an interest in STEM learning through field trips and direct engagement in scientific phenomena that allowed the girls to become agentic in continuing their engagement in STEM activities throughout the year. This call to awaken the voices of Black girls to speak casts light on their experiences and challenges as STEM learners ⎯ from their perspectives. The findings confirm that when credence and counterspaces are given to Black girls, they are poised to reveal their luster toward STEM learning. This study provided a space for Black girls to reflect on their STEM learning experiences, formulate new understandings, and make connections between the informal and formal learning environments within the context of their everyday lives, thus offering a more holistic approach to STEM learning that occurs across settings and over a lifetime

Rhabdovirus Matrix Protein Structures Reveal a Novel Mode of Self-Association

The matrix (M) proteins of rhabdoviruses are multifunctional proteins essential for virus maturation and budding that also regulate the expression of viral and host proteins. We have solved the structures of M from the vesicular stomatitis virus serotype New Jersey (genus: Vesiculovirus) and from Lagos bat virus (genus: Lyssavirus), revealing that both share a common fold despite sharing no identifiable sequence homology. Strikingly, in both structures a stretch of residues from the otherwise-disordered N terminus of a crystallographically adjacent molecule is observed binding to a hydrophobic cavity on the surface of the protein, thereby forming non-covalent linear polymers of M in the crystals. While the overall topology of the interaction is conserved between the two structures, the molecular details of the interactions are completely different. The observed interactions provide a compelling model for the flexible self-assembly of the matrix protein during virion morphogenesis and may also modulate interactions with host proteins

Extreme events are more likely to affect the breeding success of lesser kestrels than average climate change

Climate change is predicted to severely impact interactions between prey, predators and habitats. In Southern Europe, within the Mediterranean climate, herbaceous vegetation achieves its maximum growth in middle spring followed by a three-month dry summer, limiting prey availability for insectivorous birds. Lesser kestrels (Falco naumanni) breed in a time-window that matches the nestling-rearing period with the peak abundance of grasshoppers and forecasted climate change may impact reproductive success through changes in prey availability and abundance. We used Normalised Difference Vegetation Index (NDVI) as a surrogate of habitat quality and prey availability to investigate the impacts of forecasted climate change and extreme climatic events on lesser kestrel breeding performance. First, using 14 years of data from 15 colonies in Southwestern Iberia, we linked fledging success and climatic variables with NDVI, and secondly, based on these relationships and according to climatic scenarios for 2050 and 2070, forecasted NDVI and fledging success. Finally, we evaluated how fledging success was influenced by drought events since 2004. Despite predicting a decrease in vegetation greenness in lesser kestrel foraging areas during spring, we found no impacts of predicted gradual rise in temperature and decline in precipitation on their fledging success. Notwithstanding, we found a decrease of 12% in offspring survival associated with drought events, suggesting that a higher frequency of droughts might, in the future, jeopardize the recent recovery of the European population. Here, we show that extreme events, such as droughts, can have more significant impacts on species than gradual climatic changes, especially in regions like the Mediterranean Basin, a biodiversity and climate change hotspotinfo:eu-repo/semantics/publishedVersio

Quantitative 3-dimensional profiling of channel networks within transparent 'lab-on-a-chip' microreactors using a digital imaging method

We have developed a method for the quantitative 3-dimensional profiling of micron sized channel networks within optically transparent lab-on-a-chip microreactor devices. The method involves capturing digitised microscope images of the channel network filled with an optically absorbing dye. The microscope is operated in transmission mode using light filtered through a narrow bandpass filter with a maximum transmission wavelength matching the wavelength of the absorbance maximum of the dye solution. Digitised images of a chip filled with solvent and dye solution are analysed pixel by pixel to yield a spatially resolved array of absorbance values. This array is then converted to optical path length values using the Beer–Lambert law, thereby providing the 3D profile of the channel network. The method is capable of measuring channel depths from 10 to 500 µm (and probably even smaller depths) with an accuracy of a few percent. Lateral spatial resolution of less than 1 µm is achievable. It has been established that distortion of the measured profiles resulting from a mismatch in refractive index between the dye solution and the glass of the microreactors is insignificant. The method has been successfully used here to investigate the effects of thermal bonding and etch time on channel profiles. The technique provides a convenient, accurate and non-destructive method required to determine channel profiles; information which is essential to enable optimisation of the operating characteristics of microreactor devices for particular applications

Immobilization of thermophilic enzymes in miniaturized flow reactors

Abstract The exploitation of enzymes for biotransformation reactions for the production of new and safer drug intermediates has been the focus of much research. While a number of enzymes are commercially available, their use in an industrial setting is often limited to reactions that are cost-effective and they are rarely investigated further. However, the development of miniaturized flow reactor technology has meant that the cost of such research, once considered cost-and time-inefficient, would be much less prohibitive. The use of miniaturized flow reactors for enzyme screening offers a number of advantages over batch enzyme assay systems. Since the assay is performed on a miniaturized scale, enzyme, substrate and cofactor quantities are significantly reduced, thus reducing the cost of laboratory-scale investigations. Since flow reactors use microfluidic systems, where the substrate and products flow out of the system, the problems of substrate inhibition and product inhibition encountered by some enzymes are avoided. Quite often, enzymes fulfil a single-use function in biotransformation processes; however, enzyme immobilization allows enzyme reuse and often helps to increase enzyme stability. We have used an aminoacylase enzyme with potential use for industrial biotransformation reactions and have successfully immobilized it in miniaturized flow reactors. This l-aminoacylase is from the thermophilic archaeon Thermococcus litoralis. Two approaches to enzyme immobilization have been examined, both involving enzyme cross-linking. The first reactor type has used monoliths, to which the enzyme was attached, and the second contained previously cross-linked enzyme trapped using frits, in the microfluidic channels. Two different microreactor designs were used in the investigation: microreactor chips for the monoliths and capillary flow reactors for the cross-linked enzyme. These systems allowed passage of the substrate and product through the system while retaining the aminoacylase enzyme performing the catalytic conversion. The enzyme has been successfully immobilized and used to produce stable biocatalytic microreactors that can be used repeatedly over a period of several months