A new approach towards highly sensitive detection of endogenous N-acetylaspartic acid, N-acetylglutamic acid, and N-acetylaspartylglutamic acid in brain tissues based on strong anion exchange monolith microextraction coupled with UHPLC-MS/MS.

A novel in-tube solid-phase microextraction coupled with an ultra-high performance liquid chromatography-mass spectrometry method has been established for simultaneous quantification of three crucial brain biomarkers N-acetylaspartic acid (NAA), N-acetylglutamic acid (NAG), and N-acetylaspartylglutamic acid (NAAG). A polymer monolith with quaternary ammonium as the functional group was designed and exhibited efficient enrichment of target analytes through strong anion exchange interaction. Under the optimized conditions, the proposed method displayed wide linear ranges (0.1-80 nM for NAA and NAG, 0.2-160 nM for NAAG) with good precision (RSDs were lower than 15%) and low limits of detection (0.019-0.052 nM), which is by far the most sensitive approach for NAA, NAG, and NAAG determination. Furthermore, this approach has been applied to measure the target analytes in mouse brain samples, and endogenous NAA, NAG, and NAAG were successfully detected and quantified from only around 5 mg of cerebral cortex, cerebellum, and hippocampus. Compared with existing methods, the newly developed method in the current study provides highest sensitivity and lowest sample consumption for NAA, NAG, and NAAG measurements, which would potentially be utilized in determining and tracking these meaningful brain biomarkers in diseases or treatment processes, benefiting the investigations of pathophysiology and treatment of brain disorders.

Chiral electrochemiluminescence for simultaneous enantiomeric detection of aspartic acid and phenylalanine.

The burgeoning interest in rapid, simultaneous multi-target detection has propelled advancements in chiral electrochemiluminescence (ECL) assays. This study presents the design and implementation of a potential-resolved dual-color ECL sensor, engineered for the concurrent detection of aspartic acid (Asp) and phenylalanine (Phe) enantiomers. The sensor array was meticulously constructed by amalgamating anodic chiral ECL probe Ru(phen)2(L-Cys) nanocrystals with cathodic ECL probe ZnO nanoflowers (ZnO NFs). This research explored the potential of executing multianalyte assays via a potential-resolved ECL strategy, contributing to the advancements in the field of chiral ECL assays.

HPLC with chiral stationary phase for separation and kinetics study of aspartic acid epimerization in Peroxiredoxin 2 active site peptide.

Amino acid epimerization, a process of converting L-amino acids to D-amino acids, will lead to modification in the protein structure and, subsequently, its biological function. This modification causes no change in protein m/z and may be overlooked during protein analysis. Aspartic Acid Epimerization (AAE) is faster than other amino acids and could be accelerated by free radicals and peroxides. In this work, a novel and site-specific HPLC method using a chiral stationary phase for determining the AAE in the active site model peptide (AP) of Peroxiredoxin 2 has been developed and validated. The developed method showed good linearity (1 - 200 µg/mL) and recoveries of the limit of quantification (LOQ), low, medium, and high concentrations were between 85% and 115%. The Kinetics of AAE in AP were studied using the developed method, and the results showed that when ascorbic acid and Cu2+ coexisted, the AP epimerized rapidly. The AAE extent increased with time and was positively correlated with hydrogen peroxide generation.

Discrimination of Aspartic and Isoaspartic Acid Residues in Peptides by Tandem Mass Spectrometry with Hydrogen Attachment Dissociation.

Long-lived proteins undergo chemical modifications that can cause age-related diseases. Among these chemical modifications, isomerization is the most difficult to identify. Isomerization often occurs at the aspartic acid (Asp) residues. In this study, we used tandem mass spectrometry equipped with a newly developed ion activation method, hydrogen attachment dissociation (HAD), to analyze peptides containing Asp isomers. Although HAD preferentially produces [cn + 2H]+ and [zm + 2H]+ via N-Cα bond cleavage, [cn + 58 + 2H]+ and [zm - 58 + 2H]+ originate from the fragmentation of the isoAsp residue. Notably, [cn + 58 + 2H]+ and [zm - 58 + 2H]+ could be used as diagnostic fragment ions for the isoAsp residue because these fragment ions did not originate from the Asp residue. The detailed fragmentation mechanism was investigated by computational analysis using density functional theory. According to the results, hydrogen attachment to the carbonyl oxygen in the isoAsp residue results in the Cα-Cß bond cleavage. The experimental and theoretical joint study indicates that the present method allows us to discriminate Asp and isoAsp residues, including site identification of the isoAsp residue. Moreover, we demonstrated that the molar ratio of peptide isomers in the mixture could be estimated from their fragment ion abundance. Therefore, tandem mass spectrometry with HAD is a useful method for the rapid discrimination and semiquantitative analysis of peptides containing isoAsp residues.

TNF-α: A serological marker for evaluating the severity of hippocampal sclerosis in medial temporal lobe epilepsy?

OBJECTIVE: By analysing the difference in TNF-α levels in the peripheral blood of patients with medial temporal lobe epilepsy (mTLE) with or without hippocampal sclerosis and the correlation between TNF-α and N-acetylaspartate levels in the hippocampus, we explored the relationship between TNF-α and the degree of damage to hippocampal sclerosis neurons in medial temporal lobe epilepsy. METHODS: This is a prospective, population-based study. A total of 71 Patients with medial temporal lobe epilepsy diagnosed by clinical seizures, video-EEG, epileptic sequence MRI, and other imaging examinations were recruited from October 2020 to July 2022 in the Department of Neurology, Affiliated Hospital of Xuzhou Medical University. Twenty age-matched healthy subjects were selected as the control group. The patients were divided into two groups: the medial temporal epilepsy with hippocampal sclerosis group (positive group, mTLE-HS-P group) and the medial temporal epilepsy without hippocampal sclerosis group (negative group, mTLE-HS-N group). The levels of IL-1ß, IL-5, IL-6, IL-8, IL-17, IFN-γ and TNF-α in the peripheral blood of the patients in the three groups were detected by multimicrosphere flow immunofluorescence assay. The level of N-acetylaspartate (NAA) in the hippocampus was measured by 1H-MRS. The differences in cytokine levels among the three groups were analysed, and the correlation between cytokine and NAA levels was analysed. RESULTS: The level of TNF-α in the peripheral blood of the patients in the mTLE-HS-P group was significantly higher than that of the patients in the mTLE-HS-N and healthy control groups, and the level of TNF-α in the patients in the mTLE-HS-N group was significantly higher than that of the patients in the healthy control group. The NAA level in mTLE-HS-P group patients was significantly lower than that of mTLE-HS-N patients and healthy controls, but there was no significant difference between mTLE-HS-N patients and healthy controls (P > 0.05). Spearman correlation analysis showed that TNF-α level (rs = -0.437, P < 0.05) and the longest duration of a single seizure (rs = -0.398, P < 0.05) were negatively correlated with NAA level. Logistic regression analysis showed that there was no significant correlation between the longest duration of a single seizure and hippocampal sclerosis, but TNF-α level was closely related to hippocampal sclerosis in patients with mTLE (OR = 1.315, 95 % CI 1.084-1.595, P = 0.005). CONCLUSION: The level of TNF-α in the peripheral blood of patients with medial temporal lobe epilepsy with hippocampal sclerosis was higher, and it was correlated with NAA and hippocampal sclerosis. The high expression of TNF-α may be of important value in the evaluation of hippocampal sclerosis patients.

Peak Resembling N-acetylaspartate (NAA) on Magnetic Resonance Spectroscopy of Brain Metastases.

Background and Objectives: Differentiating between a high-grade glioma (HGG) and solitary cerebral metastasis presents a challenge when using standard magnetic resonance imaging (MRI) alone. Magnetic resonance spectroscopy (MRS), an advanced MRI technique, may assist in resolving this diagnostic dilemma. N-acetylaspartate (NAA), an amino acid found uniquely in the central nervous system and in high concentrations in neurons, typically suggests HGG over metastatic lesions in spectra from ring-enhancing lesions. This study investigates exceptions to this norm. Materials and Methods: We conducted an MRS study on 49 histologically confirmed and previously untreated patients with brain metastases, employing single-voxel (SVS) techniques with short and long echo times, as well as magnetic resonance spectroscopic imaging (MRSI). Results: In our cohort, 44 out of 49 (90%) patients demonstrated a typical MR spectroscopic profile consistent with secondary deposits: a Cho peak, very low or absent Cr, absence of NAA, and the presence of lipids. A peak at approximately 2 ppm, termed the "NAA-like peak", was present in spectra obtained with both short and long echo times. Among the MRS data from 49 individuals, we observed a peak at 2.0 ppm in five brain metastases from mucinous carcinoma of the breast, mucinous non-small-cell lung adenocarcinoma, two metastatic melanomas, and one metastatic non-small-cell lung cancer. Pathohistological verification of mucin in two of these five cases suggested this peak likely represents N-acetyl glycoproteins, indicative of mucin expression in cancer cells. Conclusions: The identification of a prominent peak at 2.0 ppm could be a valuable diagnostic marker for distinguishing single ring-enhancing lesions, potentially associated with mucin-expressing metastases, offering a new avenue for diagnostic specificity in challenging cases.

Non-targeted metabolomics identifies biomarkers in milk with high and low milk fat percentage.

Milk is widely recognized as an important food source with health benefits. Different consumer groups have different requirements for the content and proportion of milk fat; therefore, it is necessary to investigate the differential metabolites and their regulatory mechanisms in milk with high and low milk fat percentages (MFP). In this study, untargeted metabolomics was performed on milk samples from 13 cows with high milk fat percentage (HF) and 13 cows with low milk fat percentage (LF) using ultra-high performance liquid chromatography coupled with mass spectrometry (UHPLC-MS/MS). Forty-eight potential differentially labeled compounds were screened using the orthogonal partial least squares-discriminant analysis (OPLS-DA) combined with the weighted gene co-expression network analysis (WGCNA) method. Amino acid metabolism was the key metabolic pathway with significant enrichment of L-histidine, 5-oxoproline, L-aspartic acid, and L-glutamic acid. The negative correlation with MFP differentiated the HF and LF groups. To further determine the potential regulatory role of these amino acids on milk fat metabolism, the expression levels of marker genes in the milk fat synthesis pathway were explored. It was noticed that L-histidine reduced milk fat concentration primarily by inhibiting the triglycerides (TAG) synthesis pathway. L-aspartic acid and L-glutamic acid inhibited milk fat synthesis through the fatty acid de novo and TAG synthesis pathways. This study provides new insights into the mechanism underlying milk fat synthesis and milk quality improvement.

An engineered biosensor enables dynamic aspartate measurements in living cells.

Intracellular levels of the amino acid aspartate are responsive to changes in metabolism in mammalian cells and can correspondingly alter cell function, highlighting the need for robust tools to measure aspartate abundance. However, comprehensive understanding of aspartate metabolism has been limited by the throughput, cost, and static nature of the mass spectrometry (MS)-based measurements that are typically employed to measure aspartate levels. To address these issues, we have developed a green fluorescent protein (GFP)-based sensor of aspartate (jAspSnFR3), where the fluorescence intensity corresponds to aspartate concentration. As a purified protein, the sensor has a 20-fold increase in fluorescence upon aspartate saturation, with dose-dependent fluorescence changes covering a physiologically relevant aspartate concentration range and no significant off target binding. Expressed in mammalian cell lines, sensor intensity correlated with aspartate levels measured by MS and could resolve temporal changes in intracellular aspartate from genetic, pharmacological, and nutritional manipulations. These data demonstrate the utility of jAspSnFR3 and highlight the opportunities it provides for temporally resolved and high-throughput applications of variables that affect aspartate levels.

Polyelectrolyte-Cation Complexes Using PAsp-Sr Complexes Induce Biomimetic Mineralization with Antibacterial Ability.

Remineralized dentin with an antibacterial ability is still a significant challenge in dentistry. Previously, a polyelectrolyte-calcium complexes pre-precursor (PCCP) process is proposed for rapid collagen mineralization. In the present study, the expansion concept of the PCCP process is explored by replacing the calcium with other cations, such as strontium. The results of transmission electron microscopy (TEM), 3D stochastic optical reconstruction microscopy, energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy, and high-resolution TEM with selected area electron diffraction demonstrate that biomimetic mineralization of collagen fibrils and demineralized dentin could be fulfilled with Sr&F-codoped hydroxyapatite (HAp) after they are treated with poly-aspartic acid-strontium (PAsp-Sr) suspension followed by a phosphate&fluoride solution. Moreover, dentin remineralized with Sr&F-codoped HAp exhibits in vitro and in vivo antibacterial ability against Streptococcus mutans. The cytotoxicity and oral mucosa irritation tests reveal excellent biocompatibility of mineralization mediums (PAsp-Sr suspension and phosphate&fluoride solution). The demineralized dentin's mechanical properties (elastic modulus and microhardness) could be restored almost to that of the intact dentin. Hence, the expansion concept of the PCCP process that replaces calcium ions with some cationic ions along with fluorine opens up new horizons for generating antibacterial remineralized dentin containing ions-doped HAp with excellent biocompatibility via biomimetic mineralization technology.

Variable fragmentation and ionization of amyloid-beta epimers and isomers.

While the existence of D-amino acids in peptides and proteins has recently been accepted in higher forms of life, their roles and importance are yet to be understood. The lack of analytical methods present for such epimeric and/or isomeric analyses often limits developments in the field. Studies have shown the elevated presence of epimeric and isomeric modifications to amyloid-beta (Aß) peptides extracted from Alzheimer's disease patients. These modifications most frequently occur through aspartic acid and serine residues. Because such peptides are indistinguishable by mass alone, selective liquid chromatography tandem mass spectrometry analysis is required to differentiate such peptides. Herein, we examine MS/MS of tryptic fragments of Aß peptides containing D-Asp, L-iso-Asp, D-iso-Asp, and/or D-Ser modifications. Peptide ionizability and fragmentation are explored through selected reaction monitoring, selected ion monitoring, and product ion scan. The results show the variability of ionization and fragmentation for many "identical mass peptides" and how these differences can affect the analysis of isomeric and epimeric peptides.

[Chromatographic analysis of hard tooth tissue to determine the age of personality]. / Khromatograficheskii analiz tverdykh tkanei zuba v tselyakh opredeleniya vozrasta lichnosti.

The biochemical approach for age assessment is most appropriate in forensic medicine, as racemization of aspartic acid in bones and teeth is closely related to human biological age. The aim of the study is to assess the biochemical parameters of aspartic acid in human teeth, which can be implemented into forensic practice in Russia. Samples of dentin in amount of 20, taken from the teeth of subjects aged between 16 and 76, were examined. Chromatographic analysis of the samples was performed on a gas chromatograph using chiral column. Statistical data processing showed that the relative squared peak of D-aspartic acid has a strong correlation with human biological age. Data, obtained from the Russian population study, demonstrate the applicability of chromatography for forensic purposes. It should be noted that the approach to the racemization rate estimation in the hard tooth tissue was performed using standard laboratory equipment, which allows to easily implement this method in forensic medical practice.

An enzymatic fluorimetric assay for determination of N-acetylaspartate.

N-acetylaspartate (NAA) is an abundant metabolite in the mammalian brain and a precursor of the neuropeptide N-acetylaspartylglutamate (NAAG). The physiological role of NAA is not fully understood and requires further studies. We here describe the development of a coupled enzymatic fluorimetric assay for the determination of NAA in biological samples. Deproteinized tissue extracts are first passed through a strong cation exchange column to remove aspartate. NAA in the sample is hydrolysed by aspartoacylase and released aspartate oxidized using l-aspartate oxidase. Generated H2O2 is measured with peroxidase in a fluorimetric assay using Ampliflu Red. The limit of detection and the lower limit of quantification are 1.0 µM (10 pmol/well) and 3.3 µM (33 pmol/well), respectively, with a linear range to 100 µM. Specificity of the assay was confirmed using samples from mice deficient in NAA synthase Nat8l that were spiked with NAA. Analysis of samples from aspartoacylase-deficient mice showed a 2 to 3-fold increase in brain NAA concentration, in line with previous reports. Mice lacking NAAG synthetases had a slightly reduced (-10%) brain NAA level. Thus, the new fluorimetric enzymatic assay is useful to perform sensitive and large scale quantification of NAA in biological samples without the need for expensive equipment.

Elevated choline in dorsolateral prefrontal cortex of lithium responders with bipolar I disorder.

INTRODUCTION: Response to lithium maintenance varies widely across patients with bipolar disorder (BD). The studies on neurochemical correlates of long-term lithium response in BD remain scant. AIM: To assess the neurochemical profile in DLPFC based on lithium response status among subjects with bipolar I disorder (BD-I) using in vivo MRS. MATERIALS AND METHOD: This was an observational study of 40 right-handed, euthymic adult participants with DSM-5 BD-I on long-term lithium maintenance with no psychiatric comorbidities (MINI 7.0). Using Alda Lithium Response Scale (LRS), a cut-off ≥ 7 for excellent lithium response, the sample was grouped into study group I for responders and group II for non-responders. All participants were assessed using NIMH Life Chart Method and IGSLI typical/atypical features scale. 1H-MRS was carried out on a 3 T MR scanner (Achieva, Phillips) using a 32-channel head coil, with a voxel placed at the left DLPFC. LC model was used to measure absolute concentrations of neurochemicals and their ratios in relation to creatine. RESULTS: Group I (n = 20) was comparable to Group II (n = 20) with respect to demographic and illness profile. The GPC/Cr+PCr ratio was significantly higher (p = 0.028) among excellent lithium responders (0.32 ± 0.20 mmol/l) compared to sub-optimal responders (0.25 ± 0.05 mmol/l). Choline-containing compounds reflect alterations in cell membrane synthesis or myelin turnover, and are a marker of overall cell density. No significant alterations were detected in NAA, glutamate, glutamine, myo-inositol and creatine. CONCLUSION: The lithium responders exhibited elevated choline (GPC) in the left DLPFC compared to non-responders.

Impact of dietary supplementation with N-carbamoyl-aspartic acid on serum metabolites and intestinal microflora of sows.

BACKGROUND: N-Carbamoyl-aspartic acid (NCA) is a critical precursor for de novo biosynthesis of pyrimidine nucleotides. To investigate the cumulative effects of maternal supplementation with NCA on the productive performance, serum metabolites and intestinal microbiota of sows, 40 pregnant sows (∼day 80) were assigned into two groups: (1) the control (CON) and (2) treatment (NCA, 50 g t-1 NCA). RESULTS: Results showed that piglets from the NCA group had heavier birth weight than those in the CON group (P < 0.05). In addition, maternal supplementation with NCA decreased the backfat loss of sows during lactation (P < 0.05). Furthermore,16S-rRNA sequencing results revealed that maternal NCA supplementation decreased the abundance of Cellulosilyticum, Fournierella, Anaerovibrio, and Oribacterium genera of sows during late pregnancy (P < 0.05). Similarly, on the 14th day of lactation, maternal supplementation with NCA reduced the diversity of fecal microbes of sows as evidenced by significantly lower observed species, Chao1, and Ace indexes, and decreased the abundance of Lachnospire, Faecalibacterium, and Anaerovorax genera, while enriched the abundance of Catenisphaera (P < 0.05). Untargeted metabolomics showed that a total of 48 differentially abundant biomarkers were identified, which were mainly involved in metabolic pathways of arginine/proline metabolism, phenylalanine/tyrosine metabolism, and fatty acid biosynthesis, etc. CONCLUSION: Overall, the results indicated that NCA supplementation regulated intestinal microbial composition of sows and serum differential metabolites related to arginine, proline, phenylalanine, tyrosine, and fatty acids metabolism that may contribute to regulating the backfat loss of sows, and the birth weight and diarrhea rate of piglets. © 2022 Society of Chemical Industry.

Cognitive dysfunction and neurometabolic alternations in major depressive disorder with gastrointestinal symptoms.

BACKGROUND: Brain biochemical abnormalities have been associated with major depressive disorder (MDD) and cognitive impairments. However, the cognitive performance and neurometabolic alterations of MDD patients accompanied by gastrointestinal (GI) symptoms remain to be elucidated. We aimed to reveal the features and correlation between cognitive impairments and brain biochemical abnormalities of depressed patients with GI symptoms. METHODS: Fifty MDD patients with GI symptoms (GI group), 46 patients without GI symptoms (NGI group) and 50 demographically matched healthy controls (HCs) underwent Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) Consensus Cognitive Battery (MCCB) assessments. In addition, proton magnetic resonance spectroscopy (1H-MRS) was used to obtain ratios of N-acetyl aspartate to creatine (NAA/Cr) and choline-containing compounds to creatine (Cho/Cr) in the thalamus, putamen and anterior cingulate cortex (ACC). Finally, association analysis was conducted to investigate the relationships of these measurements. RESULTS: Compared to HCs, participants in both the GI and NGI groups had significantly reduced performance in the six MCCB cognitive domains (all p < 0.05), except for reasoning and problem solving. Higher Cho/Cr ratios in the right thalamus (p < 0.05) and lower NAA/Cr ratios in the left putamen (p < 0.05) were found in the NGI group than in the GI group. The severity of GI symptoms was negatively correlated with Cho/Cr ratios in the right ACC (r = -0.288, p = 0.037). In addition, the T-scores of visual learning were negatively correlated with NAA/Cr ratios in the right ACC (r = -0.443, p = 0.001) and right thalamus (r = -0.335, p = 0.015). CONCLUSION: Our findings suggest that MDD patients with GI symptoms may exhibit greater neurometabolic alternations than those without GI symptoms, while both show similar cognitive dysfunction. In addition, neurometabolic alterations in the ACC and thalamus may underlie the neural basis of GI symptoms and cognitive impairment in MDD.

Milk metabolome reveals pyrimidine and its degradation products as the discriminant markers of different corn silage-based nutritional strategies.

The purpose of this study was to evaluate the effect of 6 different feeding systems (based on corn silage as the main ingredient) on the chemical composition of milk and to highlight the potential of untargeted metabolomics to find discriminant marker compounds of different nutritional strategies. Interestingly, the multivariate statistical analysis discriminated milk samples mainly according to the high-moisture ear corn (HMC) included in the diet formulation. Overall, the most discriminant compounds, identified as a function of the HMC, belonged to AA (10 compounds), peptides (71 compounds), pyrimidines (38 compounds), purines (15 compounds), and pyridines (14 compounds). The discriminant milk metabolites were found to significantly explain the metabolic pathways of pyrimidines and vitamin B6. Interestingly, pathway analyses revealed that the inclusion of HMC in the diet formulation strongly affected the pyrimidine metabolism in milk, determining a significant up-accumulation of pyrimidine degradation products, such as 3-ureidopropionic acid, 3-ureidoisobutyric acid, and 3-aminoisobutyric acid. Also, some pyrimidine intermediates (such as l-aspartic acid, N-carbamoyl-l-aspartic acid, and orotic acid) were found to possess a high discrimination degree. Additionally, our findings suggested that the inclusion of alfalfa silage in the diet formulation was potentially correlated with the vitamin B6 metabolism in milk, being 4-pyridoxic acid (a pyridoxal phosphate degradation product) the most significant and up-accumulated compound. Taken together, the accumulation trends of different marker compounds revealed that both pyrimidine intermediates and degradation products are potential marker compounds of HMC-based diets, likely involving a complex metabolism of microbial nitrogen based on total splanchnic fluxes from the rumen to mammary gland in dairy cows. Also, our findings highlight the potential of untargeted metabolomics in both foodomics and foodomics-based studies involving dairy products.

Chemical Composition Assessment of Structural Parts (Seeds, Peel, Pulp) of Physalis alkekengi L. Fruits.

In recent years there has been an extensive search for nature-based products with functional potential. All structural parts of Physalis alkekengi (bladder cherry), including fruits, pulp, and less-explored parts, such as seeds and peel, can be considered sources of functional macro- and micronutrients, bioactive compounds, such as vitamins, minerals, polyphenols, and polyunsaturated fatty acids, and dietetic fiber. The chemical composition of all fruit structural parts (seeds, peel, and pulp) of two phenotypes of P. alkekengi were studied. The seeds were found to be a rich source of oil, yielding 14-17%, with abundant amounts of unsaturated fatty acids (over 88%) and tocopherols, or vitamin E (up to 5378 mg/kg dw; dry weight). The predominant fatty acid in the seed oils was linoleic acid, followed by oleic acid. The seeds contained most of the fruit's protein (16-19% dw) and fiber (6-8% dw). The peel oil differed significantly from the seed oil in fatty acid and tocopherol composition. Seed cakes, the waste after oil extraction, contained arginine and aspartic acid as the main amino acids; valine, phenylalanine, threonine, and isoleucine were present in slightly higher amounts than the other essential amino acids. They were also rich in key minerals, such as K, Mg, Fe, and Zn. From the peel and pulp fractions were extracted fruit concretes, aromatic products with specific fragrance profiles, of which volatile compositions (GC-MS) were identified. The major volatiles in peel and pulp concretes were ß-linalool, α-pinene, and γ-terpinene. The results from the investigation substantiated the potential of all the studied fruit structures as new sources of bioactive compounds that could be used as prospective sources in human and animal nutrition, while the aroma-active compounds in the concretes supported the plant's potential in perfumery and cosmetics.

Effect of exogenous l-aspartate nano­calcium on root growth, calcium forms and cell wall metabolism of Brassica napus L.

Currently, l-aspartate nano­calcium (Ca(L-asp)-NPs) has been sued as a calcium supplement for humans, but its effects on plants are not well elucidated. This study aimed to investigate the effect of exogenous Ca(L-asp)-NPs on the growth of rapeseed (Brassica napus L.) for the first time. Different concentrations (0, 50, 100, 150, and 200 mg L-1) of Ca(L-asp)-NPs and 1.18 g L-1 Ca(NO3)2 were used in the nutrient solution. The results indicated that Ca2+ released from Ca(L-asp)-NPs were absorbed by the roots, and had a significant effect on plant height, root length, biomass accumulation, and root structure formation, especially on the growth and development of coarse roots at 100 mg L-1 Ca(L-asp)-NPs. Calcium (Ca) accumulation, Ca-pectinate, Ca-phosphate and Ca­carbonate, and Ca-oxalate in plant roots and leaves were positively linked with Ca(L-asp)-NPs concentration. For cell wall, Ca(L-asp)-NPs treatment increased the content of pectin, and the activity of cell wall degrading enzymes in roots, such as pectin methyl-esterase (PME), cellulose enzyme (CE), polygalacturonase (PG), and ß-galactosidase (ß-Gal). For cell membrane osmotic regulation, Ca(L-asp)-NPs promoted the accumulation of soluble sugar and soluble protein. This finding suggests that 100 mg L-1 Ca(L-asp)-NPs had the best growth-promoting effect on rapeseed. This study provides a valuable reference for exogenous Ca(L-asp)-NPs as new nano Ca supplements for plant growth.

The effects of low pH on the taste and amino acid composition of tiger shrimp.

Recent research has revealed that shrimp sensory quality may be affected by ocean acidification but we do not exactly know why. Here we conducted controlled pH exposure experiments on adult tiger shrimp, which were kept in 1000-L tanks continuously supplied with coastal seawater. We compared survival rate, carapace properties and flesh sensory properties and amino acid composition of shrimp exposed to pH 7.5 and pH 8.0 treatments for 28 days. Shrimp reared at pH 7.5 had a lower amino acid content (17.6% w/w) than those reared at pH 8.0 (19.5% w/w). Interestingly, the amino acids responsible for the umami taste, i.e. glutamate and aspartic acid, were present at significantly lower levels in the pH 7.5 than the pH 8.0 shrimp, and the pH 7.5 shrimp were also rated as less desirable in a blind quality test by 40 volunteer assessors. These results indicate that tiger shrimp may become less palatable in the future due to a lower production of some amino acids. Finally, tiger shrimp also had a lower survival rate over 28 days at pH 7.5 than at pH 8.0 (73% vs. 81%) suggesting that ocean acidification may affect both the quality and quantity of future shrimp resources.

Separation and determination of 3-hydroxyaspartate by online concentration capillary electrophoresis/laser-induced fluorescence with microwave-assisted derivatization.

A chiral analytical method was proposed based on capillary electrophoresis with laser-induced fluorescence detection coupled with microwave-assisted derivatization for the simultaneous baseline separation and sensitive detection of four stereoisomers of 3-hydroxyaspartate. The derivatization reaction of 3-hydroxyaspartate with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole was greatly accelerated by microwave irradiation. Under the optimized conditions, the derivatization yield was increased by 20% and the derivatization time was shortened by 20 min when compared with those from conventional water bath heating. In addition, the sensitivity was improved by online sample concentration methods. The detection limit of l-threo-3-hydroxyaspartate obtained by large-volume sample stacking with polarity switching was 5.3 nmol/L, which was around 1000-fold lower than that of the capillary electrophoresis/laser-induced fluorescence without stacking. The excellent analytical performance in terms of linearity and precision was also achieved. Furthermore, the developed method was successfully applied to the determination of 3-hydroxyaspartate in the spiked urine, and satisfactory recoveries were obtained ranging from 90.5 to 107.0%.