A rapid method for the determination of stable hydrogen isotope ratios of acetic acid in vinegar.

RATIONALE: Vinegar is an everyday condiment made from fermented grains or fruits. It contains acetic acid which is the main organic material produced by fermentation. Vinegar suffers from the authenticity problem of exogenous adulteration due to the indistinguishability of low-cost chemical sources of synthetic acetic acid from acetic acid produced by fermentation. It is necessary to establish a simple and rapid measurement technique. METHODS: Determination was according to the total acid content of vinegar diluted with acetone to a certain concentration. Online separation and determination of acetic acid δD in vinegar were carried out using gas chromatography-pyrolysis-isotope ratio mass spectrometry. RESULTS: An HP-Plot/U column was selected for online separation of acetic acid and water with molecular sieve characteristics. At the same time, combined with the instrument blowback function to remove water. Dilute solvent acetone was treated with a molecular sieve to remove trace water. The reproducibility of this method is less than 3‰. The long-term stability is within a reasonable error range. The accuracy correlation coefficient is greater than 0.99. The δD values of acetic acid in vinegar (-264.5 ± 20.3‰) and from chemical sources (-30.5 ± 90.8‰) were obtained. CONCLUSIONS: A rapid method was developed for identification of different sources of acetic acid. These different sources of acetic acid exhibited significant hydrogen isotope distribution characteristics. Additionally, it was observed that the carboxyl hydrogen of acetic acid exhibited facile exchange with water. In future investigations, we aim to mitigate this interference.

Correction to: Measurement of the 15N/14N ratio of phenylalanine in fermentation matrix by isotope ratio mass spectrometry.

The publisher was alerted that the following important entry in the references of this article was missing.

Measurement of the 15N/14N ratio of phenylalanine in fermentation matrix by isotope ratio mass spectrometry.

OBJECTIVES: To determine the origin of 15N-labeled phenylalanine in microbial metabolic flux analysis using 15N as a tracer, a method for measuring phenylalanine δ15N using HPLC coupled with elemental analysis-isotope ratio mass spectrometry (EA-IRMS) was developed. RESULTS: The original source of the 15N-labeled phenylalanine was determined using this new method that consists of three steps: optimization of the HPLC conditions, evaluation of the isotope fractionation effects, and evaluation of the effect of pre-processing on the phenylalanine nitrogen stable isotope. In addition, the use of a 15N-labeled inorganic nitrogen source, rather than 15N-labeled amino acids, was explored using this method. CONCLUSIONS: The method described here can also be applied to the analysis of metabolic flux.

Discrimination of brewing technologies and assessment of health risks based on rare earth elements: Evidence of fingerprint in Chinese famous vinegars.

Considering the essential influence of vinegar brewing processes on human health, this study determined the content and fractionation of rare earth elements (REEs) in 40 Chinese vinegar products to assess food safety and probe the application of REEs in tracing brewing processes. The total REEs contents in different products exhibited great variations (1.66 µg/kg to 124.54 µg/kg), which should be attributed to the difference in brewing techniques. Vinegars produced by solid brewing fermentation normally contain higher REEs contents than those produced by liquid brewing fermentation. The REEs contents in vinegars from inland areas were higher than those from coastal areas. The health risk assessment indicated that REEs contents were below the daily intake standards; however, considerable attention should be paid on the risk to children. This study contributes foundational data for understanding REEs behavior in vinegars, which is crucial for ensuring food safety and identifying the actual vinegar production process.

A new method to analysis synthetic acetic acid to vinegar: Hydrogen isotope ratio at the methyl site of acetic acid in vinegar by GC-IRMS.

Acetic acid is the key organic substance used to verify the authenticity of vinegar. A new method for precisely determining acetic acid δDCH3 in vinegar via gas chromatography -pyrolytic-stable isotope ratio mass spectrometry (GC-P-IRMS) was established. The δDCH3 values were obtained via calibration with a series of standards. The optimised method demonstrated a repeatability standard deviation within 3 ‰. The standard deviation of accuracy of the new method compared with that of the SNIF-NMR method was within 2.6 ‰. The synthetic acetic acid δDCH3 values was -136.7 ‰ ± 29.6 ‰, and the δDCH3 value of acetic acid in vinegar was -414.9 ‰ ± 40.5 ‰, with significant isotopic distribution characteristics. This methodology serves as a supplementary method for measuring the δDCH3 value of acetic acid in vinegar. It has advantages over other methods in terms of time, sensitivity and operability. And provides a new idea for solving the problem of analyzing substances in the presence of exchangeable groups.

A Review of Development and Utilization for Edible Fungal Polysaccharides: Extraction, Chemical Characteristics, and Bioactivities.

Edible fungi, commonly known as mushrooms, are precious medicinal and edible homologous gifts from nature to us. Because of their distinctive flavor and exceptional nutritional and medicinal value, they have been a frequent visitor to people's dining tables and have become a hot star in the healthcare, pharmaceutical, and cosmetics industries. Edible fungal polysaccharides (EFPs) are an essential nutrient for edible fungi to exert bioactivity. They have attracted much attention because of their antioxidant, immunomodulatory, antitumor, hypoglycemic, and hypolipidemic bioactivities. As a result, EFPs have demonstrated outstanding potential over the past few decades in various disciplines, including molecular biology, immunology, biotechnology, and pharmaceutical chemistry. However, the complexity of EFPs and the significant impact of mushroom variety and extraction techniques on their bioactivities prevents a complete investigation of their biological features. Therefore, the authors of this paper thoroughly reviewed the comparison of different extraction methods of EFPs and their advantages and disadvantages. In addition, the molecular weight, monosaccharide composition, and glycosidic bond type and backbone structure of EFPs are described in detail. Moreover, the in vitro and in vivo bioactivities of EFPs extracted by different methods and their potential regulatory mechanisms are summarized. These provide a valuable reference for improving the extraction process of EFPs and their production and development in the pharmaceutical field.

Stable isotope ratio analysis of carbon to distinguish sialic acid from freshly stewed bird's nest products.

Freshly stewed bird's nest products are easily adulterated with exogenous synthetic sialic acid to enhance the grade of the products and sell at high prices. This paper identifies the carbon stable isotope characteristics of sialic acid from natural and commercially synthetic sources using stable isotope ratio mass spectrometry (IRMS). Specifically, an off-line pretreatment technique combined with on-line LC-IRMS was developed to accurately determine δ13C values of sialic acid in a freshly stewed bird's nest. This method has no obvious isotope fractionation and good reproducibility. EA-IRMS was used to determine the δ13C values of commercial sialic acid. The results showed that the δ13C values of sialic acid from natural and synthetic sources were -29.90% ± 0.42% and -16.26% ± 3.91%, respectively, with distinct carbon stable isotope distribution characteristics. By defining a δ13C threshold value of -28.54% for natural SA, additional commercial SA from a minimum of 10% can be identified. Therefore, δ13C was proposed as a suitable tool for verifying the authenticity of fresh stewed bird's nests on the market.

What's in a wine? - A spot check of the integrity of European wine sold in China based on anthocyanin composition, stable isotope and glycerol impurity analysis.

The international wine market has been repeatedly hit by cases of fraud in recent decades. While several studies attested a special vulnerability of the fast growing wine business in China, reports on chemical analyses of commercial wine samples are rare. We examined 50 predominantly red wines with European labelling, which were purchased on the Chinese market, for fraud-relevant parameters. More than 20% of the tested samples revealed anomalies in relation to the stable isotope ratios of D/H, 18O/16O and 13C/12C, contents of technical glycerol by-products or anthocyanin composition. These results strongly suggested watering of the wines, chaptalisation, glycerol addition or the use of non-Vitis anthocyanin sources, respectively. Some of these samples also showed suspicious spelling errors or other irregularities in the labelling, but the majority appeared genuine to the eye. Hence, this spot check demonstrates the importance of chemical authenticity analysis of market samples in order to detect fraudulent products. Moreover, we used the same sample set for an evaluation of the Chinese standard method for carbon stable isotope determination of wine ethanol in comparison to the current OIV (International Organisation of Vine and Wine) standard method. The results of a Bland-Altman analysis indicated that the methods can be applied interchangeably. As the two methods differ in their workflow and in the requested equipment, this might eventually enable more laboratories to perform 13C/12C analysis of wine and spirits.

Vintage analysis of Chinese Baijiu by GC and 1H NMR combined with multivariable analysis.

Economical-driven counterfeit and inferior aged Chinese Baijiu has caused serious concern of publicity in China. In this study, a total of 167 authentic Chinese Baijiu samples with different vintages including 3 flavor types were carefully collected. Gas chromatography (GC) was used to determine main volatile components and proton nuclear magnetic resonance (1H NMR) spectroscopy was employed to obtain non-targeted fingerprints of Chinese Baijiu samples. Partial least squares regression (PLSR) models, which were confirmed by internal and external validation, were established for effectively identifying actual storage vintage of Chinese Baijiu with various brands, flavor types. Centering (Ctr), pareto scaling (Par), unit variance scaling (UV) data pretreatment methods, principal components (PCs), and three modified variable selection methods were proposed to successfully optimize the vintage model and effectively extract important vintage characteristic factors. This study demonstrated that NMR and GC combined with multivariate statistical analysis are effective tools for validating vintage authenticity of Chinese Baijiu.

Experimental Study on the Failure Mechanisms in Brittle Shales.

The brittle failure of Chengkou shale occurs throughout the exploration and development processes of hydrocarbons. To investigate the failure mechanisms of Chengkou shale and analyze the associated mechanical behavior such as crack initiation, propagation, and coalescence at different stress levels, a series of laboratory experiments were conducted on servo-controlled triaxial cells equipped with ultrasound monitoring. The experimental results show that key mechanical parameters such as peak stress σp, stress onset of dilation σci, and strain at peak stress εp exhibit nearly linear relationships at various confining pressures. In rock bodies, the wave velocity evolution at different stress levels very consistently reproduces the shape of stress-strain curves, while shear wave velocity v s is more sensitive to crack damage than compressional wave velocity v p. Furthermore, the Hoek-Brown failure criterion has an advantage over the Mohr-Coulomb fracture criterion due to the former's higher correlation coefficient r 2. The wing crack damage models with sandwiched multilayers help explain the mixed tensile and shear failure mechanisms of Chengkou shale. The experimental results provide significant guidance for optimizing the design of drilling and well completion jobs, especially hydraulic fracturing operations, both in Chengkou shale and in other brittle shales around the world.

Insights into the Effect of Spontaneous Fluid Imbibition on the Formation Mechanism of Fracture Networks in Brittle Shale: An Experimental Investigation.

In this paper, the high-temperature/high-pressure triaxial testing system of rocks is used to study the effect of spontaneous fluid imbibition on the formation mechanism of fracture networks, by means of acoustic emission (AE) monitoring and ultrasound measurement. After the water-shale interaction, the rock mechanical parameters such as rock strength, elastic modulus, cohesion, and internal friction angle of shales significantly decrease as the imbibition time increases, indicating that the fluid has a strong influence on the mechanical properties of brittle shales. The stress-strain curves of the wet and dry shales and their AE characteristics are quite different: (i) the stress-strain curve of wet shale samples shows multiple fluctuations before macroscopic failure, and its cumulative AE number curve presents a step-like jump many times that corresponds to the local microcracking; (ii) the stress-strain curve of dry shale samples mainly shows the characteristic of linear elastic deformation during early loading, which has less AE event number, and the step-like jump is not observed in all the AE curves. The dry shale only has a large number of AE events until it is close to macroscopic failure. Nuclear magnetic resonance, mineral composition, and microstructure analysis show that Chengkou shale generally develops micro-nanoscale pores with a small pore throat, and thus strong capillary spontaneous absorption occurs. The shale-water interaction includes both chemical and physical effects, which affect the key parameters such as acoustic velocity, frictional force on the surfaces of artificial fracture, fracability, and other mechanical properties. This paper provides new insights to the investigation on the formation mechanism of artificial fracture networks in brittle shales.

Elemental profile and oxygen isotope ratio (δ18O) for verifying the geographical origin of Chinese wines.

The elemental profile and oxygen isotope ratio (δ18O) of 188 wine samples collected from the Changji, Mile, and Changli regions in China were analyzed by inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectroscopy (ICP-OES) and isotope ratio mass spectrometry (IRMS), respectively. By combining the data of δ18O and the concentration data of 52 elements, the analysis of variance (ANOVA) technique was firstly applied to obtain the important descriptors for the discrimination of the three geographical origins. Ca, Al, Mg, B, Fe, K, Rb, Mn, Na, P, Co, Ga, As, Sr, and δ18O were identified as the key explanatory factors. In the second step, the key elements were employed as input variables for the subsequent partial least squares discrimination analysis (PLS-DA) and support vector machine (SVM) analyses. Then, cross validation and random data splitting (training set: test set = 70:30, %) were performed to avoid the over-fitting problem. The average correct classification rates of the PLS-DA and SVM models for the training set were both 98%, while for the test set, these values were 95%, 97%, respectively. Thus, it was suggested that the combination of oxygen isotope ratio (δ18O) and elemental profile with multi-step multivariate analysis is a promising approach for the verification of the considered three geographical origins of Chinese wines.

Rapid Method for the Determination of the Stable Oxygen Isotope Ratio of Water in Alcoholic Beverages.

This paper demonstrates the first successful application of an online pyrolysis technique for the direct determination of oxygen isotope ratios (δ(18)O) of water in alcoholic beverages. Similar water concentrations in each sample were achieved by adjustment with absolute ethyl alcohol, and then a fixed GC split ratio can be used. All of the organic ingredients were successfully separated from the analyte on a CP-PoraBond Q column and subsequently vented out, whereas water molecules were transferred into the reaction furnace and converted to CO. With the system presented, 15-30 µL of raw sample was diluted and can be analyzed repeatedly; the analytical precision was better than 0.4‰ (n = 5) in all cases, and more than 50 injections can be made per day. No apparent memory effect was observed even if water samples were injected using the same syringe; a strong correlation (R(2) = 0.9998) was found between the water δ(18)O of measured sample and that of working standards. There was no significant difference (p > 0.05) between the mean δ(18)O value and that obtained by the traditional method (CO2-water equilibration/isotope ratio mass spectrometry) and the newly developed method in this study. The advantages of this new method are its rapidity and straightforwardness, and less test portion is required.

Yeast dynamin implicated in endocytic scission and the disassembly of endocytic components.

The yeast dynamin-related GTPase Vps1 has been implicated in a range of cellular functions including vacuolar protein sorting, protein trafficking, organization of peroxisome and endocytosis.1,2 Vps1 is present at endocytic sites and may be directly involved in endocytic vesicle invagination through its membrane-tubulating activity. Here, evidence supporting the functional link between Vps1 and the yeast amphiphysin Rvs167 in vesicle invagination is discussed. Though the disassembly of endocytic factors from pinched-off endocytic vesicles appears to be tightly regulated in a spatiotemporal manner, we are far from having complete understanding of the underlying mechanism. In this study, we provide evidence that Vps1 plays a role in the uncoating of endocytic proteins from post-internalized vesicles, based on the observation of a quick disassembly of two endocytic coat proteins Ent1 and Ent2 in cells lacking Vps1.

The yeast dynamin-like protein Vps1:vps1 mutations perturb the internalization and the motility of endocytic vesicles and endosomes via disorganization of the actin cytoskeleton.

Mammalian dynamin is responsible for scission of endocytic vesicles from the plasma membrane. A previous study showed that Vps1, a yeast dynamin-like protein, plays an important role in pheromone receptor internalization (Yu and Cai, 2004; J. Cell Sci. 117, 3839-3853). However, the details of how Vps1 acts in various phases of endocytosis including early internalization of the endocytic vesicle are poorly understood. To investigate the potential roles of Vps1 in both endocytic vesicle formation/maturation on the plasma membrane and endocytic vesicle internalization, time-lapse fluorescent images of GFP-tagged endocytic markers in live cells were analyzed using a particle tracking software. The loss of Vps1 leads to a robust increase in the lifespan of newly forming cortical endocytic vesicles carrying Las17-GFP, Ede1-GFP, Sla1-GFP, and Abp1-GFP, indicating that Vps1 is required for the proper assembly and maturation of endocytic vesicles. Particle track analysis revealed that Abp1-GFP vesicles in vps1 null cells moved a relatively short distance away from the cell membrane due to their non-directional movement. Furthermore, we found that the GTPase and the GED domains of Vps1 are required for the proper endocytic function of Vps1. Our tracking analysis data also revealed that the post-internalized vesicle motility en route to the vacuole was decreased significantly, perhaps due to severe disruption of the actin cables in Vps1 mutant cells.

[Correlation of vascular endothelial growth factor D, microlymphatic density and microvessel density with development and metastasis of rectal cancer].

OBJECTIVE: To investigate the correlation of vascular endothelial growth factor D (VEGF-D) expression, microlymphatic density (MLD) and microvessel density (MVD) levels with the development and metastasis of rectal cancer. METHODS: Eighty specimens from resected middle-lower rectal cancer diagnosed by pathology were examined by immunohistochemistry for VEGF-D,MLD and MVD. Simultaneously, 40 biopsy specimens from rectal polyps and 80 specimens from normal rectal tissue were examined as controls. Correlation between the expression of above three factors and the tumor size, gross morphology, histological type, metastasis, differentiation grade, infiltration depth, Dukes stage, lymph node metastasis and long-distance metastasis before operation were investigated with Spearman method. RESULTS: (1) Positive expression rate of VEGF-D was 55 % (44/80) in rectal cancer, and zero in rectal polyps and normal rectal tissues. The expression of VEGF-D in rectal cancer was significantly higher than that in rectal polyps and normal rectal tissues(P<0.05). MLD was significantly higher in rectal cancer (2.80+/-1.31) than that in rectal polyps (0.50+/-0.72) and normal rectal tissues(0.25+/-0.44)(P<0.05).Meanwhile MVD was significantly higher in rectal cancer (80.10+/-23.18) than that in rectal polyps (27.00+/-11.01) and normal rectal tissues (10.45+/-5.34) (P<0.05). (2) VEGF-D, MLD and MVD were positively correlated with lymph node metastasis and long-distance metastasis before operation (P<0.05). (3) VEGF-D was positively correlated with MLD (P<0.05) and MLD was positively correlated with MVD as well(P<0.05). CONCLUSIONS: Lymphangiogenesis exists in rectal cancer tissues. VEGF-D and MLD can be used as good predictors of lymphangiogenesis and they are the important factors affecting biological behavior of rectal cancer. Lymphangiogenesis and angiogenesis may have a cooperative function in the development of rectal cancer.