Posttranscriptional regulation of genes of mammalian iron metabolism is mediated by the interaction of iron regulatory proteins (IRPs) with RNA stem-loop sequence elements known as iron-responsive elements (IREs)

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We have analyzed, by site-directed mutagenesis, the molecular basis of the editing function and its relation to the synthetic function of Escherichia coli methionyl-tRNA synthetase. The data obtained fit a model of the active site that partitions an amino acid substrate between synthetic and editing pathways. Hydrophobic and hydrogen bonding interactions direct the cognate substrate methionine through the synthetic pathway and prevent it from entering the editing pathway. Two hydrophobic interactions are proposed: between the side chain of Trp-305 and a methyl group ofmethionine and between the benzene ring of Tyr-15 and the 1& and f-CH2 groups of the substrate. An essential hydrogen bond forms between the OH of Tyr-15 and an electron pair of the sulfur atom of methionine. Consistent with these functions, side chains of Trp-305 and Tyr-15 are localized on opposite sides of the cavity forming a putative methionine binding pocket that is observed in the three-dimensional crystallographic structure of methionyl-tRNA synthetase. Enzymes W305A, Y15A, and Y15F have diminished ability to discriminate against homocysteine in the synthetic reaction, compared to the wild-type enzyme. At the same time, mutant enzymes have lost the ability to discriminate against methionine in the editing reaction and edited Met-AMP to a similar extent as Hcy-AMP. Interactions of residues Arg-233 and Asp-52 of methionyl-tRNA synthetase with the carboxyl and amino groups, respectively, of the substrate, which are essential for the synthetic function, were also essential for the editing function of the enzyme. Deacylation of Met-tRNA to S-methylhomocysteine thiolactone catalyzed by W305A, Y15A, and Y15F mutant enzymes was only slightly impaired relative to the wild-type enzyme. However, enzymes R233Q, R233A, and D52A did not deacylate MettRNA. The model also explains why the noncognate homocysteine is edited by methionyl-tRNA synthetase.

Five furanocoumarins including a new one were isolated from the root of Angelica dahurica by repeated silica gel column chromatography. Their chemical structures were determined to be isoimperatorin (1), oxypeucedanin hydrate-3"-butyl ether (2), imperatorin (3), knidilin (4), and oxypeucedanin hydrate (5). This represents the first study in which the compound 2 has been isolated and identified. The long-range coupling (5J) in the 1H-NMR spectrum observed in the linear furanocoumarin skeleton was also investigated in detail.

Animal origin food products, including fish and seafood, meat and poultry, milk and dairy foods, and other related products play significant roles in human nutrition. However, fraud in this food sector frequently occurs, leading to negative economic impacts on consumers and potential risks to public health and the environment. Therefore, the development of analytical techniques that can rapidly detect fraud and verify the authenticity of such products is of paramount importance. Traditionally, a wide variety of targeted approaches, such as chemical, chromatographic, molecular, and protein-based techniques, among others, have been frequently used to identify animal species, production methods, provenance, and processing of food products. Although these conventional methods are accurate and reliable, they are destructive, time-consuming, and can only be employed at the laboratory scale. On the contrary, alternative methods based mainly on spectroscopy have emerged in recent years as invaluable tools to overcome most of the limitations associated with traditional measurements. The number of scientific studies reporting on various authenticity issues investigated by vibrational spectroscopy, nuclear magnetic resonance, and fluorescence spectroscopy has increased substantially over the past few years, indicating the tremendous potential of these techniques in the fight against food fraud. It is the aim of the present manuscript to review the state-of-the-art research advances since 2015 regarding the use of analytical methods applied to detect fraud in food products of animal origin, with particular attention paid to spectroscopic measurements coupled with chemometric analysis. The opportunities and challenges surrounding the use of spectroscopic techniques and possible future directions will also be discussed.

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Two new triterpenoids along with three known ones, 3-oxoolean-12-en-27-oic acid (1), 3alpha-hydroxyolean-12-en-27-oic acid (2) and 3beta-hydroxyolean-12-en-27-oic acid (3), were isolated from Aceriphyllum rossii. The structures of the new compounds were determined to be a 3alpha,23-dihydroxyolean-12-en-27-oic acid (4) and a 3alpha,23-dihydroxyolean-12-en-29-oic acid (5) by spectroscopic and chemical methods; they were designated aceriphyllic acids A and B, respectively. Compounds 2, 3 and 4 remarkably inhibited the activity of ACAT.

Recently, Near-infrared (NIR)-induced photothermal killing of pathogenic bacteria has received considerable attention due to the increase in antibiotic resistant bacteria. In this paper, we report a simple aqueous solution-based strategy to construct an effective photothermal nanocomposite composed of poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) and agarose with thermo-processability, light triggered self-healing, and excellent antibacterial activity. Our experiments revealed that PEDOT:PSS/agarose was easily coated on both a 2D glass substrate and 3D cotton structure. Additionally, PEDOT:PSS/agarose can be designed into free-standing objects of diverse shape as well as restored through an NIR light-induced self-healing effect after damage. Taking advantage of strong NIR light absorption, PEDOT:PSS/agarose exhibited a sharp temperature increase of 24.5 °C during NIR exposure for 100 sec. More importantly, we demonstrated that the temperature increase on PEDOT:PSS/agarose via photothermal conversion resulted in the rapid and effective killing of nearly 100% of the pathogenic bacteria within 2 min of NIR irradiation.