Search

The assignment of structure by tandem mass spectrometry (MS/MS) relies on the interpretation of the fragmentation behavior of gas-phase ions. Mass spectra were acquired for a series of heterocyclic mimetics of acidic amino acids and a related series of nitrile amino acids. All amino acids were readily protonated or deprotonated by electrospray ionization (ESI), and distinctive fragmentation processes were observed when the ions were subjected to collision-induced dissociation (CID). The deprotonated heterocycles showed bond cleavages of the 3-hydroxyfurazan ring with formation of oxoisocyanate and the complementary deprotonated nitrile amino acid. Further fragmentation of the deprotonated nitrile amino acids was greatly dependent on the length of the alkyl nitrile side chain. Competing losses of CO 2 versus HCN occurred from α-cyanoglycinate (shortest chain), whereas water was lost from 2-amino-5-cyanopentanoate (longest chain). Interestingly, loss of acrylonitrile by a McLafferty-type fragmentation process was detected for 2-amino-4-cyanobutanoate, and several competing processes were observed for β-cyanoalanate. In one process, cyanide ion was formed either by consecutive losses of ammonia, carbon dioxide, and acetylene or by a one-step decarboxylative elimination. In another, complementary ions were obtained from β-cyanoalanate by loss of acetonitrile or HN=CHCO 2 H. Fragmentation of the protonated 3-hydroxyfurazan and nitrile amino acids resulted in the cumulative loss (H 2 O + CO), a loss that is commonly observed for protonated aliphatic α-amino acids. Overall, the distinct fragmentation behavior of the multifunctional 3-hydroxyfurazan amino acids correlated with the charged site, whereas fragmentations of the deprotonated nitrile amino acids showed cooperative interactions between the nitrile and the carboxylate groups., (© 2024 The Authors. Journal of Mass Spectrometry published by John Wiley & Sons Ltd.)

This review covers the know-how of the Grupo de Química Analítica e Quimiometria regarding the analysis of fatty acids by capillary electrophoresis acquired over its 20 years of existence. Therefore, the fundamentals, advantages, and applications of this technique for analyzing different fatty acids in samples such as food, oils, cosmetics, and biological matrices are presented and discussed. Capillary electrophoresis is, thus, shown as an interesting and valuable separation technique for the target analysis of these analytes as an alternative to the gas chromatography coupled to flame ionization detection, as it offers advantages over the latter such as low analysis times, low sample and reagent consumption, the use of a nondedicated column, and simpler sample preparation. In addition, the methods shown in this literature review can be useful for quality control, adulteration, and health-related research by regulatory agencies., (© 2023 Wiley-VCH GmbH.)

In order to improve students' theoretical level and practical ability, a comprehensive experiment, the determination of amino acids in Cerasus humilis fruit, was designed for instrumental analysis course. The sample analysis pretreatment process was introduced to construct a complete instrumental analysis process. Through the comparison of amino acid extraction methods and the exploration of solid phase extraction technology in the process of amino acid purification, students' theoretical knowledge and practical ability can be effectively fused and improved, and the scientific literacy and comprehensive thinking ability of students can thus be improved during the process of solving practical problems. [ABSTRACT FROM AUTHOR]

A branched DNA-based electrochemical biosensor was designed to sensitively detect specific nucleic acids. On this platform, novel a branched DNA with three sticky ends could be used as a biosensor to sensitively and specifically detect nucleic acids. Meanwhile, we also employed branched DNA-modified AuNPs as a signal amplifier to further improve the sensitivity. Branched DNA sensors, target DNA, and DNA-modified AuNPs formed a sandwich structure to produce an electronic signal for target DNA detection. The reaction primarily involved DNA hybridization without bulky thermal cyclers and enzymes. We proved that the hybridization reaction easily occurred under different conditions, such as the NaCl concentration, reaction time, pH, and temperature, except for a pH lower than 4. The limit of detection could go as low as 0.09 pM (S/N = 3) with excellent specificity and selectivity. There was a correlation curve relationship between the peak current and the logarithm of the target DNA concentration (0.10 pM to 10 nM). The correlation coefficient reached 0.987. The electrochemical platform enables a branched DNA nanostructure to determine nucleic acids for disease diagnosis.

Alternating‐rich copolymer of vinylboronic acid pinacol ester (VBpin) and maleic anhydride (MAH) was found to catalyze direct dehydrative esterification of carboxylic acid and alcohol. The key to the catalytic function is the activation of the MAH unit by the neighboring Lewis acidic boron directly connected to the backbone through the formation of five‐membered ring. The effects of the side‐chain cooperation were clarified through comparisons with the polymers having similar structures and a conventional titanium catalyst as well as the analyses of reactions with carboxylic acid or alcohol. The catalytic activity was enhanced as the molecular weight was higher, which is owing to the structural feature that boron is directly attached to the backbone. The cooperative catalysis is of interest because of its conceptual similarity with enzyme. [ABSTRACT FROM AUTHOR]

Boswellia serrata ole-gum-resin extracts (BSEs) are commonly used as food supplements, especially in osteoarthritis management. The quality standard is established by determining 11-keto-β-boswellic acid (KBA) and acetyl-11-keto-boswellic acid (AKBA) content using high-performance liquid chromatography (HPLC) or assessing the total boswellic acid (TBA) content by titrimetry. The limited geographical distribution of Boswellia species and increasing industrial demand could increase the risk of adulteration in Boswellia-containing products. In this study, 14 BSEs from commercial sources, used in food supplements, were analyzed in comparison with a USP Reference Standard extract. The KBA and AKBA content was determined by HPLC, whereas the TBA content was determined by titration. Targeted UHPLC-high-resolution mass spectrometry (HRMS) was applied to identify the carboxylic acid content in the samples. The 1H NMR spectra of extracts were also analyzed. Only two products met the criteria for KBA and AKBA content. Although, the TBA content complied with the expected amount, 10 extracts contained citric acid levels of 6–11% even though citric acid is not a cha-racteristic component of BSEs. Our results suggest undeclared addition of citric acid to comply with declared contents of TBA when using titration methods. Incorporation of citric acid to industrial samples – in order to alter the outcomes of the titration analysis – was demonstrated for the first time. [ABSTRACT FROM AUTHOR]

Ion chromatography (IC) is a variant of high-performance liquid chromatography. Its most important applications include the determination of inorganic and some organic ions in different types of liquid samples. The development of new types of stationary phases with various separation mechanisms, sample preparation methods, and detection modes has extended ion chromatography applications to practically all ionic and ionogenic substances, as well as extending sample types to include gaseous and solid matrices. Carboxylic acids and their derivatives are examples of compounds that are becoming more frequently analyzed using ion chromatography and related techniques. Their occurrence in the environment can be natural or anthropogenic in origin and are broadly used in various industries and daily life. This article discusses the applications of ion chromatography and related techniques for the determination of carboxylic acids in different types of liquid, solid, and gaseous matrices. It also presents detailed methodologies and literature data on this subject from the last 15 years. [ABSTRACT FROM AUTHOR]

Previous researches showed that fatty acids analysis might be a useful tool to support the taxonomic investigation. In this approach the fatty acids content of ten Malvoideae species was analyzed and its chemotaxonomic significance has been investigated. The aerial parts of the species were collected in the Northeast of Brazil and their fatty acid methyl esters were analyzed by gas chromatography with flame ionization detector. The chemometric analysis consisted of principal component analysis (PCA) and hierarchical clustering analysis (HCA) with the euclidean distance between the samples given by the Ward.D2 algorithm. This is the first report of fatty acids from Wissadula peripocifolia, Herissantia crispa, Bakeridesia pickelii, Sidastrum micranthum, Pavonia cancellata and Pavonia malacophylla. The results showed the predominance of palmitic (C16:0), oleic (C18:1) and linoleic (C18:2) acids in the studied species. By the PCA and HCA analysis, the fatty acid composition was able to distinguish the species Herissantia crispa and Pavonia malacophylla. Our findings showed a chemotaxonomic proximity among species from different genera reflecting the taxonomic and phylogenetic closeness previously demonstrated by molecular investigations on Malvoidae species. Furthermore, our results demonstrated that the fatty acid analysis may be an interesting tool to support the taxonomic investigations on Malvoideae species.

A branched DNA-based electrochemical biosensor was designed to sensitively detect specific nucleic acids. On this platform, novel a branched DNA with three sticky ends could be used as a biosensor to sensitively and specifically detect nucleic acids. Meanwhile, we also employed branched DNA-modified AuNPs as a signal amplifier to further improve the sensitivity. Branched DNA sensors, target DNA, and DNA-modified AuNPs formed a sandwich structure to produce an electronic signal for target DNA detection. The reaction primarily involved DNA hybridization without bulky thermal cyclers and enzymes. We proved that the hybridization reaction easily occurred under different conditions, such as the NaCl concentration, reaction time, pH, and temperature, except for a pH lower than 4. The limit of detection could go as low as 0.09 pM (S/N = 3) with excellent specificity and selectivity. There was a correlation curve relationship between the peak current and the logarithm of the target DNA concentration (0.10 pM to 10 nM). The correlation coefficient reached 0.987. The electrochemical platform enables a branched DNA nanostructure to determine nucleic acids for disease diagnosis.

A silicon lab-on-chip, for the detection of nucleic acids through the integrated PCR and hybridization microarray, was developed. The silicon lab-on-chip manufactured through bio-MEMS technology is composed of two PCR microreactors (each volume 11.2 µL) and a microarray-hybridization microchamber (volume 30 µL), fluidically connected by buried bypass. It contains heaters and temperature sensors for the management and control of the temperature cycles during the PCR amplification and hybridization processes. A post-silicon process based on (i) plasmo-O2 cleaning/activation, (ii) vapor phase epoxy silanization, (iii) microarray fabrication and (iv) a protein-based passivation step was developed and fully characterized. The ssDNA microarray (4 rows × 10 columns) composed of 400 spots (spot size—70 ± 12 µm; spot-to-spot distance—130 ± 13 µm) was manufactured by piezo-dispense technology. A DNA microarray probe density in the range of 1310 to 2070 probe µm−2 was observed, together with a limit of detection of about 19 target µm−2. The performances of the silicon lab-on-chip were validated by the detection of the beta-globin gene directly from human blood. Remarkable sensitivity, multiplexing analysis and specificity were demonstrated for the detection of beta-globin and mycobacterium tuberculosis sequences.

Antilipopolysaecharide factors (ALF) are antimicrobial peptides in the humoral defense mechanism in shrimps, with broad activity against bacteria, viruses, and fungi. Several ALF and their isoforms have been reported in decapod crustaceans, showing structural and functional differences. This work describes the Litopenaeus vannamei antilipopolysaecharide factor 5. initially found in a hepatopancreatic transcriptomic database. The LvALF5 gDNA sequence is 1,619 bp, with a complete mRNA sequence of 934 bp. The ORF encodes a 124 amino acids sequence, including a 26 amino acids signal peptide and 98 amino acids mature peptide, highly similar to the Litopenaeus stylirostris ALF peptide sequence (96%). This peptide shows main differences in the LPS-binding domain, having only 2 positive amino acids conserved. The evolutionary analysis shows that LvALF5 is in cluster 2, which indicates that structurally it has characteristics of the other white shrimp isoforms. LrALF5 is highly expressed in healthy shrimp hemocytes, 20-fold more than in other tissues. It is up-regulated during bacterial and viral challenges. Inhibition experiments using a recombinant LrALF5 show a more efficient antibacterial activity against Vibrio parahaemolytieus than Staphylococcus aureus bacteria strains. KEY WORDS: Litopenaeus vannamei, antimicrobial peptides, gene expression, Vibrio parahaemolvticus, WSSV, antibacterial activity, INTRODUCTION The Pacific white shrimp Litopenaeus vannamei is one of the most important cultured species in the aquaculture industry. Despite being a very profitable commercial product reaching 5.8 million tonnes [...]