219 research outputs found
âThis Wonderful Machineâ: How Should We Teach Humanities Texts like Gulliverâs Travels in the Time of ChatGPT?
The quoted phrase in the essay title comes from a passage in Jonathan Swift\u27s Gulliverâs Travels in which a Grand Academy of Lagado professor demonstrates a âwonderful Machineâ that can generate scores of books âwithout the least Assistance from Genius or Study.â The essay explore the challenge for teaching classic humanities texts like Gulliver that the (perhaps not so) âwonderful Machineâ called ChatGPT poses. Student Owen Terryâs Chronicle essay (May 12, 2023) identifies two crucial aspects of that challenge: âWe donât fully lean into AI and teach how to best use it, and we donât fully prohibit it to keep it from interfering with exercises in critical thinking.â The essay explains my rationale not to âlean into AI but to prohibit it and to promote instead âcritical thinking
Structural analysis of the carboxy terminal PH domain of pleckstrin bound to D-myo-inositol 1,2,3,5,6-pentakisphosphate
<p>Abstract</p> <p>Background</p> <p>Pleckstrin homology (PH) domains are one of the most prevalent domains in the human proteome and represent the major phosphoinositide-binding module. These domains are often found in signaling proteins and function predominately by targeting their host proteins to the cell membrane. Inositol phosphates, which are structurally similar to phosphoinositides, are not only known to play a role as signaling molecules but are also capable of being bound by PH domains.</p> <p>Results</p> <p>In the work presented here it is shown that the addition of commercial <it>myo</it>-inositol hexakisphosphate (IP<sub>6</sub>) inhibited the binding of the carboxy terminal PH domain of pleckstrin (C-PH) to phosphatidylinositol 3,4-bisphosphate with an IC<sub>50 </sub>of 7.5 ÎŒM. In an attempt to characterize this binding structurally, C-PH was crystallized in the presence of IP<sub>6 </sub>and the structure was determined to 1.35 Ă
. Examination of the resulting electron density unexpectedly revealed the bound ligand to be D-<it>myo</it>-inositol 1,2,3,5,6-pentakisphosphate.</p> <p>Conclusion</p> <p>The discovery of D-<it>myo</it>-inositol 1,2,3,5,6-pentakisphosphate in the crystal structure suggests that the inhibitory effects observed in the binding studies may be due to this ligand rather than IP<sub>6</sub>. Analysis of the protein-ligand interaction demonstrated that this <it>myo</it>-inositol pentakisphosphate isomer interacts specifically with protein residues known to be involved in phosphoinositide binding. In addition to this, a structural alignment of other PH domains bound to inositol phosphates containing either four or five phosphate groups revealed that the majority of phosphate groups occupy conserved locations in the binding pockets of PH domains. These findings, taken together with other recently reported studies suggest that <it>myo-</it>inositol pentakisphosphates could act to regulate PH domain-phosphoinositide interactions by directly competing for binding, thus playing an important role as signaling molecules.</p
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Oat and lipolysis: food matrix effect
Oat is rich in a wide range of phytochemicals with various physico-chemical, colloidal and interfacial properties. These characteristics are likely to influence human lipid metabolism and the subsequent effect on health following oat consumption. The aim of this work was to investigate the impact of oat materials varying in complexity on the lipolysis process. The composition, structure and digestibility of different lipid systems (emulsions, oil bodies and oil enriched in phytosterols) were determined. The surface activities of phytosterols were examined using the pendant drop technique. Differences in lipid digestibility of the oat oil emulsions and the oil bodies were clearly seen. Also, the digestion of sunflower oil was reduced proportionally to the concentration of phytosterols present. This may be due to their interfacial properties as demonstrated by the pendant drop experiments. This work highlights the importance of considering the overall structure of the system studied and not only its composition
A Binary Millisecond Pulsar in Globular Cluster NGC6544
We report the detection of a new 3.06 ms binary pulsar in the globular
cluster NGC6544 using a Fourier-domain ``acceleration'' search. With an implied
companion mass of ~0.01 solar masses and an orbital period of only P_b~1.7
hours, it displays very similar orbital properties to many pulsars which are
eclipsed by their companion winds. The orbital period is the second shortest of
known binary pulsars after 47 Tuc R. The measured flux density of 1.3 +/- 0.4
mJy at 1332 MHz indicates that the pulsar is almost certainly the known
steep-spectrum point source near the core of NGC6544.Comment: Accepted by ApJ Letters on 11 October 2000, 5 page
Overexpression of an endogenous type 2 diacylglycerol acyltransferase in the marine diatom Phaeodactylum tricornutum enhances lipid production and omega-3 long-chain polyunsaturated fatty acid content
Background: Oleaginous microalgae represent a valuable resource for the production of high-value molecules. Considering the importance of omega-3 long-chain polyunsaturated fatty acids (LC-PUFAs) for human health and nutrition the yields of high-value eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) require significant improvement to meet demand; however, the current cost of production remains high. A promising approach is to metabolically engineer strains with enhanced levels of triacylglycerols (TAGs) enriched in EPA and DHA.
Results: Recently, we have engineered the marine diatom Phaeodactylum tricornutum to accumulate enhanced levels of DHA in TAG. To further improve the incorporation of omega-3 LC-PUFAs in TAG, we focused our effort on the identification of a type 2 acyl-CoA:diacylglycerol acyltransferase (DGAT) capable of improving lipid production and the incorporation of DHA in TAG. DGAT is a key enzyme in lipid synthesis. Following a diatom based in vivo screen of candidate DGATs, a native P. tricornutum DGAT2B was taken forward for detailed characterisation. Overexpression of the endogenous P. tricornutum DGAT2B was confirmed by qRT-PCR and the transgenic strain grew successfully in comparison to wildtype. PtDGAT2B has broad substrate specificity with preferences for C16 and LC-PUFAs acyl groups. Moreover, the overexpression of an endogenous DGAT2B resulted in higher lipid yields and enhanced levels of DHA in TAG. Furthermore, a combined overexpression of the endogenous DGAT2B and ectopic expression of a Î5-elongase showed how iterative metabolic engineering can be used to increase DHA and TAG content, irrespective of nitrogen treatment.
Conclusion: This study provides further insight into lipid metabolism in P. tricornutum and suggests a metabolic engineering approach for the efficient production of EPA and DHA in microalgae
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb carbonate geochronology: strategies, progress, and limitations
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) UâPb geochronology of carbonate minerals, calcite in particular, is rapidly gaining popularity as an absolute dating method. The high spatial resolution of LA-ICP-MS UâPb carbonate geochronology has benefits over traditional isotope dilution methods, particularly for diagenetic and hydrothermal calcite, because uranium and lead are heterogeneously distributed on the sub-millimetre scale. At the same time, this can provide limitations to the method, as locating zones of radiogenic lead can be time-consuming and âhit or missâ. Here, we present strategies for dating carbonates with in situ techniques, through imaging and petrographic techniques to data interpretation; our examples are drawn from the dating of fracture-filling calcite, but our discussion is relevant to all carbonate applications. We review several limitations to the method, including open-system behaviour, variable initial-lead compositions, and Uâdaughter disequilibrium. We also discuss two approaches to data collection: traditional spot analyses guided by petrographic and elemental imaging and image-based dating that utilises LA-ICP-MS elemental and isotopic map data
Estimating the bispectrum of the Very Small Array data
We estimate the bispectrum of the Very Small Array data from the compact and
extended configuration observations released in December 2002, and compare our
results to those obtained from Gaussian simulations. There is a slight excess
of large bispectrum values for two individual fields, but this does not appear
when the fields are combined. Given our expected level of residual point
sources, we do not expect these to be the source of the discrepancy. Using the
compact configuration data, we put an upper limit of 5400 on the value of f_NL,
the non-linear coupling parameter, at 95 per cent confidence. We test our
bispectrum estimator using non-Gaussian simulations with a known bispectrum,
and recover the input values.Comment: 17 pages, 16 figures, replaced with version accepted by MNRAS.
Primordial bispectrum recalculated and figure 11 change
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