Amino Acid Analysis Research Articles

Extraction and Evaluation of Active Ingredients of Saussurea costus Roots and Determination of its Antibacterial Activity

Saussurea costus (Sc) plant belongs to the Asteraceae family. It contains various bioactive compounds used traditionally in treating multiple diseases. This study intends to extract and evaluate the active ingredients of Sc roots (Scrs) and determine their antibacterial activities. S. costus roots were purchased from the herbal market and the chemical compositions, including protein, lipid, carbohydrates, moisture, and ash, were determined according to AOAC procedures 2016 with some modifications. HPLC and amino acids analyzer were used to determine the phenolic compounds and amino acid composition of S. costus roots extract (ScrsE). The antibacterial activities of S. costus roots extract were done according to the Kirby-Bauer disc diffusion method. The S. costus roots were revealed a fusiform (or) conical and tapering appearance, collapsing in the centre with longitudinal wrinkles revealing 11-19 cm and 1-2.5 cm for long and wide, respectively. The extraction yield was 9.52% and the weight of the concentrated crude extract was 10 g. According to Proximate analysis, the S. costus roots extract showed 3.88% and 20.12% moisture and ash contents, respectively. The compositions of carbohydrates, protein, and crude fat were 75.25%, 2.51%, and 1.85%, respectively. HPLC analysis showed that the S. costus roots Extract contained two phenolic acids and two flavonoids. Moreover, twelve amino acids were determined for the first time in the S. costus roots extract. Various antibacterial activities were seen with maximum inhibition zone for Streptococcus pyogenes & E.coli; and minimum for Bacillus subtilis & Pseudomonas aeruginosa. In conclusion, this study investigated various contents of S. costus roots extract including amino acids, carbohydrates, protein, and crude fat, in addition to its antibacterial activities. The authors recommend more future studies to investigate the therapeutic activities of S. costus roots extract.

Physicochemical and sensory properties of retort chicken curry mousse fortified with branched-chain amino acids for the elderly

Although retort sterilization is effective in high-temperature sterilization of special nutritional products, its effect on sensorial and nutritional properties after sterilization has not been proven. The purpose of this study was to develop a BCAAs fortified chicken curry mousse (CCM) for the elderly that is easy to chew, swallow, and convenient to cook and consume at home. Additionally, it was to investigate the effect of retort processing on the sensory satisfaction and nutritional formula of the products. A viscosity thickener was added to set the thickener concentration based on the fork drip test of the International Dysphagia Diet Standardization Initiative. CCM was retort-treated at 121 °C for 30 min to evaluate its physicochemical (color, viscosity, rheology, texture, syneresis, pH, and amino acid analysis) and sensory properties. The viscosity decreased and texture changed smoothly after retorting, and the color became darker. The syneresis and pH of the retorted mousse showed fewer changes than the non-retorted during 12 days. Retorted products were increased the BCAAs, and scored high in overall acceptance in the sensory evaluation. Therefore, the BCAAs-enriched retort CCM developed in this study is expected to hedonically appeal to the elderly as well as benefitting their muscle health and nutrition.

Fast, Direct Analysis of Underivatized Amino Acids in Infant Formula

Fast, Direct Analysis of Underivatized Amino Acids in Infant Formula

Flavor improvement of fermented soybean foods by co-fermentation with Bacillus velezensis and Lactiplantibacillus plantarum

This study aimed to improve the flavor of fermented soybean foods and to investigate the molecular mechanisms of this flavor improvement phenomenon. Three fermented soybean foods (Bv, BvLp and Lp) were obtained using Bacillus velezensis SDL1 and Lactiplantibacillus plantarum Ly8 as starter cultures. Organoleptic evaluation showed that BvLp had the best flavor, followed by Bv and Lp. Next, some flavor-related physicochemical properties were investigated. Acid production level was ranked as Lp > BvLp > Bv, in which acetic acid and lactic acid were the main contributors to the variation in sample acid content, and BvLp contained the most lactic acid and isovaleric acid, 3.72−49.62 and 3.61−37.75 times those of Lp and Bv, respectively. Free amino acid analysis showed that the concentration trends of branched-chain amino acids and threonine were consistent with the sensory evaluation. Volatile metabolomics analysis indicated that acetoin and pyrazines were the key compounds for the superior flavor of BvLp. Finally, transcriptomic analysis, combined with the above data, revealed that under a parasitic-like interaction in microbial mixed culture, BvLp had significantly more flavor than Bv and Lp by reducing the acid content and increasing the concentration of some esters, acetoin and pyrazines.

Proximate and amino acid analysis of mulberry and non-mulberry silkworm pupae

Proximate and amino acid analysis of mulberry and non-mulberry silkworm pupae

WEAK SEED DORMANCY 1, an aminotransferase protein, regulates seed dormancy in rice through the GA and ABA pathways

Seed dormancy is a critical trait that enhances plant survival by preventing seed germination at the wrong time or under unsuitable conditions. Lack of seed dormancy in rice can lead to pre-harvest sprouting on mother plants leading to reduced yield and seed quality. Although some genes have been identified, knowledge of regulation of seed dormancy is limited. Here, we characterized a weak seed dormancy mutant named weak seed dormancy 1 (wsd1) that showed a higher seed germination percentage than the wild-type following the harvest ripeness. We cloned the WSD1 encoding an aminotransferase protein using a MutMap approach. WSD1 was stably expressed after imbibition and its protein was localized in the endoplasm reticulum. A widely targeted metabolomics assay and amino acid analysis showed that WSD1 had a role in regulating homeostasis of amino acids. PAC treatment and RNA-seq analysis showed that WSD1 regulates seed dormancy by involvement in the GA biosynthesis pathway. GA1 content and expression of GA biosynthesis-related genes were increased in the wsd1 mutant compared with the wild-type. The wsd1 mutant had reduced sensitivity to ABA. Our overall results indicated that WSD1 regulates seed dormancy by balancing the ABA and GA pathways.

The ionome and proteome landscape of aging in laying hens and relation to egg white quality.

The ionome is essential for maintaining body function and health status by participating in diverse key biological processes. Nevertheless, the distribution and utilization of ionome among different organs and how aging impacts the ionome leading to a decline in egg white quality remain unknown. Thus, we used inductively coupled plasma mass spectrometry (ICP-MS) to analyze 35 elements and their isotopic contents in eight organs of laying hens at 35, 72, and 100 weeks. Moreover, the magnum proteome, amino acids in egg white, and egg white quality were analyzed in laying hens at three different ages using 4D proteomics techniques, an amino acid analyzer, and an egg quality analyzer. Across the organs, we identified varying distribution patterns among macroelements (Mg24, Ca43/44, K39, and P31), transition metals (Zn64/66, Cu63/65, Fe56/57, and Mn55), and toxic elements (Pb208, Ba137, and Sr86). We observed an organ-specific aging pattern characterized by the accumulation of toxic elements (Pb208, Ba137, and Sr86) and calcification in the small intestine. Additionally, a decrease in the utilization of essential trace elements selenium (Se78/82) and manganese (Mn55) was noted in the oviduct. By analyzing ionome in tandem with egg quality, egg white amino acids, and proteome, we unveiled that the reduction of selenium and manganese concentrations in the magnum during the aging process affected amino acid metabolism, particularly tryptophan metabolism, thereby inhibiting the amino acid synthesis in the magnum. Furthermore, it accelerated the senescence of magnum cells through necroptosis activation, leading to a decline in the albumen secretion function of the magnum and subsequently reducing egg white quality. Overall, this study provides insights into the evolution of 35 elements and their isotopes across 8 organs of laying hens with age. It also reveals the elemental composition, interactions, and utilization patterns of these organs, as well as their correlation with egg white quality. The present study highlights the significance of ionome and offers a comprehensive perspective on the selection of ionome for regulating the aging of laying hens.

Sex-Specific Correlation Analysis of Branched-Chain Amino Acids in Dietary Intakes and Plasma among Chinese Adults

BackgroundPrevious findings about the influence of dietary intakes of the branched-chain amino acid (BCAA) on their plasma concentrations have been limited and inconsistent, and evidence from the Chinese population was lacking. ObjectivesThis study aimed to investigate the diet-plasma BCAA correlations in Chinese male and female adults. MethodsThis cross-sectional study was based on a nested case-control study within 2 prospective population-based cohorts in Shanghai, China. Diet information was collected by the food frequency questionnaires. Plasma BCAA concentrations were measured by ultraperformance liquid chromatography coupled with tandem mass spectrometry. Spearman correlations and linear regression models were conducted to examine the relationships between dietary BCAA intakes and plasma BCAA. The multivariable model was adjusted for age at the interview, total energy intake, time of blood collection from last meal, dietary patterns, body mass index (in kg/m2), type 2 diabetes, and physical activity. ResultsA total of 322 males (median age of 57.0 y) and 187 females (median age of 60.0 y) were included in this cross-sectional study. The geometric means of dietary intake of leucine, isoleucine, valine, and BCAA were 4937.7, 3029.6, 3268.5, and 11237.4 mg/d in males, and 4125.7, 2567.8, 2754.3, and 9449.4 mg/d in females. The geometric means of plasma concentrations of leucine, isoleucine, valine, and BCAA were 181.9, 65.0, 219.8, and 469.4 μM/L in males and 161.6, 61.1, 206.5, and 431.6 μM/L in females. Only leucine (r = 0.1660, P = 0.0028) and total BCAA (r = 0.1348, P = 0.0155) in males exhibited weak positive correlation coefficients. After adjustment for the covariates, leucine, isoleucine, valine, and total BCAA in dietary intakes and plasma were not correlated in both males and females. ConclusionsIn Chinese male and female adults, dietary intakes are not major determinants of plasma concentrations of BCAA, and plasma concentrations might not be reflected by usual dietary intakes of BCAA.

Comparative Analysis of Amino Acid and Biogenic Amine Compositions of Fermented Grape Beverages.

Amino acids and biogenic amines are important components of food and beverages. In grape-derived products such as wine and wine vinegar, they can have different origins and can influence the odor and taste of the products. Their concentration is influenced by the grape variety, vintage, and winemaking process. In our study, we carried out an LC-MS-based comparative analysis of 22 grape-derived beverages, including three different wine types and four wine vinegar samples from the Tokaj region in Hungary. The concentrations of 23 amino acids and 10 biogenic amines were examined, and the differences among the sample types were analyzed. The differences in the concentrations of some metabolites between Aszú-Furmint pairs originating from the same wineries and year provide information on the effect of botrytized grape on wine composition. Our data can provide further evidence on how the production process shapes the metabolite content of beverages and highlight the nutritional value of wine vinegar.

Amino Acid Profile of the Oil Seed of Guizotia scabra Harvested From Plateau and Kaduna States – Nigeria

Guizotia scabra (L.F cass. composite) is an oil seed crop found wildly and in some areas cultivated at middle and higher elevations in Nigeria and other African countries. The medicinal importance attached to the plant and the acceptance of the seed in some of our rural areas for preparing different types of delicacies is the driving force of this research. The objectives of this study were to determine the amino acids profile. PTH Amino acid analyser was used to determine amino acids in the sample. Amino acid profile revealed that Glutamic acid in the sample from Plateau was 2.57 g/100g protein while Kaduna state was 3.14g/100g protein; arginine in the sample from Plateau was 1.72 g/100g protein while that from Kaduna was 2.06 g/100g protein. Leucine from Plateau was 1.69 g/100g protein while that of Kaduna was 2.10 g/100g protein; aspartic acid in the sample from Plateau was 1.55 g/100g protein while that of Kaduna was 1.80 g/100g protein. The sample from Plateau was 1.00-glycine per100 g protein while that of Kaduna was 1.17 g/100g protein, tyrosine in sample from Plateau was 0.52 g/100g protein while that of Kaduna was 0.34 g/100g protein, isoleucine in sample from Plateau was 0.49 g/100 g protein while that of Kaduna was 0.82 g/100g protein. In addition, Alanine in the sample from Plateau was 0.42 g/100 g protein while that of Kaduna was 0.53 g/100g protein as valine in the sample from Plateau was 0.41 g/100 g protein while that of Kaduna was 0.61 g/100g protein. The sample from Plateau has 0.41g proline per 100g protein while that of Kaduna was 0.51 g/100g protein. Glycine in the sample from Plateau was 0.38 g/100g protein while that of Kaduna was 0.50 g/100g protein, and phenylalanine in the sample from Plateau was 0.35 g/100g protein while that of Kaduna was 0.44 g/100g protein. The sample from Plateau has 0.24g cysteine per100g protein while that of Kaduna was 0.24 g/100g protein; threonine in the sample from Plateau was 0.19 g/100g protein while that of Kaduna was 0.28 g/100g protein. The sample from Plateau has 0.16g serine per g/100g protein while that of Kaduna was 0.22 g/100g protein. The concentration of tryptophan in the sample from Plateau was 0.16 g/100g protein while that of Kaduna was 0.23 g/100g protein and histidine in the sample from Plateau was 0.10 g/100g protein while that from Kaduna was 0.19 g/100g protein. The essential and non-essential amino acids from plateau state are 36.19% and 38.18% respectively while that from Kaduna state are 38.44% and 61.56% respectively. These therefore makes the seed a good source of protein and it is hereby recommended for the fortification of diets that are low in protein for both man and animals.

Nutritional profiling and quantitative analysis of amino acids and vitamins using LC–MS/MS in selected raw and germinated ancient grains

AbstractBackgroundAncient grains are grains that have remained unchanged over the past decades. Among them, millets and pseudocereals are highly nutritious underutilized grains that are gluten free. The present study compares the nutritional composition of nine important ancient grains in its raw and germinated forms.ResultsAmong the grains studied, amaranth had the highest protein content (14.52%), followed by proso (13.04%) and foxtail millets (12.78%). Amino acid analysis was carried out using LC–MS/MS. Besides amaranth, barnyard, pearl, and proso millets contained considerable amount of essential amino acids. The lysine content of sorghum has increased four folds during germination. Valine, histidine, and glutamic acid contents increased marginally upon sprouting. These grains were also found to contain significant amount of B complex vitamins. The ascorbic acid content of the grains increased considerably upon germination especially in foxtail millet (78.03–30452.90 ng/g).ConclusionThe present study is the first comparative study that has brought out the distinct nutritional superiority of the ancient grains in their raw and germinated forms. These gluten‐free grains can be utilized to improve the nutritional demand and food security of the growing population.

Enzymatic dehairing of sheep skin: Recovery and characterization of commercially important wool hydrolysate and fats

Conventional dehairing methods in the traditional leather-making processes, consume large amounts of toxic chemicals and produce a toxic sludge/effluent, posing disposal challenges and consequently environmental pollution. The by-products of leather processing such as hair and fat, contain toxic chemicals. In this study, crude alkaline protease from <i>bacillus cereus strain 1-p, </i>was used to dehair sheepskin with up to 99.00% recovery of valuable wool and fat. The optimum temperature and pH for wool removal were found to be 30 <sup>°</sup>C and 11, respectively. The recovered wool was enzymatically hydrolyzed to obtain wool hydrolysate powder (48.1% yield). FTIR spectra of the wool hydrolysate showed the presence of amide A, I, and II absorption bands. Further, the amino acid analysis, revealed the presence of 15 amino acids, with glutamic acid (19.65 mole %), glycine (12.72 mole %), and leucine (9.42 mole %) being the most abundant. Fat was trans-esterified using methanol, in the presence of tert-butanol, and the resultant fatty acid methyl esters characterization was done using gas chromatography/mass spectrometry (GC/MS) analysis. GC/MS analysis showed the presence of 60 methyl esters corresponding to 60 fatty acids. The most abundant fatty acid was 9-octadecenoic (oleic) acid (41.64%), followed by hexa-decanoic (palmitic) acid (22.50%), and tetra-decanoic (myristic) acid (4.21%). Thermo-gravimetric analysis of the wool hydrolysate showed that it had good thermal stability. It is shown that crude alkaline protease extracted from <i>bacillus cereus strain 1-p</i> can completely eliminate the use of toxic sodium sulfide and lime in dehairing of skins/hide in tanneries, eliminating environmental pollution. Furthermore, the recovery of fat and wool using an eco-friendly enzymatic dehairing process can significantly reduce the pollution load in the effluent. The recovered wool and fats can be applied in the production of wool hydrolysate, which is high in protein content, amino acids and biodiesel.

Integrated models of blood protein and metabolite enhance the diagnostic accuracy for Non-Small Cell Lung Cancer

BackgroundFor early screening and diagnosis of non-small cell lung cancer (NSCLC), a robust model based on plasma proteomics and metabolomics is required for accurate and accessible non-invasive detection. Here we aim to combine TMT-LC-MS/MS and machine-learning algorithms to establish models with high specificity and sensitivity, and summarize a generalized model building scheme.MethodsTMT-LC-MS/MS was used to discover the differentially expressed proteins (DEPs) in the plasma of NSCLC patients. Plasma proteomics-guided metabolites were selected for clinical evaluation in 110 NSCLC patients who were going to receive therapies, 108 benign pulmonary diseases (BPD) patients, and 100 healthy controls (HC). The data were randomly split into training set and test set in a ratio of 80:20. Three supervised learning algorithms were applied to the training set for models fitting. The best performance models were evaluated with the test data set.ResultsDifferential plasma proteomics and metabolic pathways analyses revealed that the majority of DEPs in NSCLC were enriched in the pathways of complement and coagulation cascades, cholesterol and bile acids metabolism. Moreover, 10 DEPs, 14 amino acids, 15 bile acids, as well as 6 classic tumor biomarkers in blood were quantified using clinically validated assays. Finally, we obtained a high-performance screening model using logistic regression algorithm with AUC of 0.96, sensitivity of 92%, and specificity of 89%, and a diagnostic model with AUC of 0.871, sensitivity of 86%, and specificity of 78%. In the test set, the screening model achieved accuracy of 90%, sensitivity of 91%, and specificity of 90%, and the diagnostic model achieved accuracy of 82%, sensitivity of 77%, and specificity of 86%.ConclusionsIntegrated analysis of DEPs, amino acid, and bile acid features based on plasma proteomics-guided metabolite profiling, together with classical tumor biomarkers, provided a much more accurate detection model for screening and differential diagnosis of NSCLC. In addition, this new mathematical modeling based on plasma proteomics-guided metabolite profiling will be used for evaluation of therapeutic efficacy and long-term recurrence prediction of NSCLC.

Loss of sea ice and intermittent winds alter distributions and diet resources of young forage fish in the Chukchi sea

Loss of sea ice alters habitat for organisms that function as energetic links in Arctic food webs. To address the impacts of such changes on lower trophic levels we focus on forage fish during the early life stages (polar cod: Boreogadus saida and saffron cod: Eleginus gracilis) and copepods (Calanus spp. and Pseudocalanus spp.) in the Chukchi Sea with differing reliance on sea ice environments. We assess distributions throughout years of varying ice extent (2010–2013, 2015, 2017–2018) and diet resources during unprecedented warm years (2017, 2018) using stable isotope analyses (bulk δ13C and δ15N and δ13C compound-specific isotope analysis of amino acids). Calanus spp. and polar cod were found at relatively higher latitudes in closer proximity to recent sea ice, whereas saffron cod were rare and Pseudocalanus spp. were ubiquitous. Polar cod juveniles, but not larvae, were more common in open water, suggesting that low ice and northward ocean currents interact to influence juvenile distributions. Low summer sea ice also coincided with northward expansion of warm Pacific-origin water across the shelf. Stable isotope δ13C values reflected this latitudinal variation in water masses as well as inshore-offshore gradients due to convergence of ocean currents. When summer sea ice was absent during 2017, juvenile polar cod were dispersed across the shelf, abundances were low for both copepod taxa, isotopic niche was reduced for polar cod, and carbon sources for some larval polar cod reflected boreal-associated phytoplankton. Distributions and isotopic patterns suggest that under low ice conditions, along-shelf wind reversals and weak currents can lead to dominance of Pacific-origin water, mixing of organisms from various source locations, and reductions in sea ice-influenced environments. Northward expansion of subarctic water masses and organisms across the Chukchi shelf alters basal resources for lower trophic levels and modifies pelagic habitats to more uniformly resemble lower latitude marine ecosystems.

Comprehensive reversed-phase×chiral two-dimensional liquid chromatography coupled to quadrupole-time-of-flight tandem mass spectrometry with post-first dimension flow splitting for untargeted enantioselective amino acid analysis.

This work describes a comprehensive achiral × chiral two-dimensional liquid chromatography separation for enantioselective amino acid analysis coupled to electrospray ionization-tandem mass spectrometry detection using data-independent acquisition. Flow splitting after the first and second dimension separation was utilized for volumetric flow reduction and for enabling a multi-detector approach (with ultraviolet, fluorescence, charged aerosol, and MS detection), respectively. Derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate provided a chromophore, a fluorophore, and an efficient mass tag for efficient ionization in positive electrospray ionization-mass spectrometry. Chiral columns often have limitations in terms of their chemoselectivity, which may be a problem when complex sample mixtures with structurally related compounds need to be separated. It can be alleviated by a reversed-phase×chiral two-dimensional-liquid chromatography setup, in which the first dimension provides the chemoselectivity and a chiral tandem column constituted of quinine-carbamate derived weak anion-exchanger and zwitterionic ion-exchanger in the second dimension separation of D- and L-amino acid enantiomers. The method was used to control the stereointegrity of the therapeutic peptide octreotide. After hydrolysis, all amino acid constituents were detected with the correct configuration and composition. Some options for flow splitting and integration of destructive detectors in the first dimension separation are outlined.

Controls on the composition of dissolved organic matter in treatment wetland source waters of South Florida, USA

Dissolved organic matter (DOM) plays an important role in the phosphorus (P) and nitrogen (N) cycle, but the examination of coupled biogeochemical cycling in treatment wetlands, like the Everglades Stormwater Treatment Areas (STAs), has been limited. Here, we studied eight STA inflow waters to gain insights into the production and potential photo- and biolability of DOM in surface waters flowing into these treatment wetlands. A suite of optical and fluorometric indices was coupled with amino acid and bulk elemental analyses to evaluate differences in inflow water quality for particulate organic matter (POM), DOM (<0.2 μm), and high and low molecular weight DOM (HMW-DOM and LMW-DOM). A photochemical experiment was conducted with these inflow waters to assess how solar exposure alters DOM turnover and its relationship with nutrient concentrations, and to evaluate the influence of photochemistry on potential STA performance. The DOM of STA inflow water was predominantly composed of allochthonous terrestrial sources, and the LMW-DOM fraction represented 70 to 94% of the total DOM pool. Inflow waters separated along the biophysical dimension of our PCA based on their photolability and bioavailability, driven by differences in the inflow water's DOM composition. UV exposure decreased humic and aromaticity proxies with concomitant photo-production of LMW compounds and increases in bioavailability proxies. Photo-exposure significantly decreased nitrate and dissolved organic carbon (DOC) concentrations for most of the sites and dissolved organic N (DON) for three of the eight sites, but no significant changes were noted for ammonia. One site exhibited an increase in nitrate with UV exposure and had DOM primarily from terrestrial origins. Spectroscopic indices, PARAFAC components, and amino acids provided corroborating evidence that further supported the differences in photo- and biolability at each inflow site, which is likely driven by their original DOM characteristics. PARAFAC components were correlated with dissolved organic P (DOP) and suggest that there may be adsorption of DOP with humic components in the LMW fraction. This work highlights the importance of photochemistry in the STAs, the complexity of DOM turnover in STA source waters, and the potential interactions between dissolved P and other DOM components, which may further influence the treatment efficiency of the STAs.

Comparison of Flavor Profile Relationship of Soy Sauce under Different Storage Conditions.

To elucidate the relation of flavor in soy sauce (SS) kept at room temperature (SSAT) and SS kept under accelerated aging condition (SSAA), four analytical instruments, including electronic nose (E-nose), electronic tongue (E-tongue), gas chromatography-mass spectrometry-olfactory combined with solvent assisted flavor evaporation, and amino acid analyzer, were applied for analyzing the overall flavor profiles and flavor constituents in SSAT and SSAA. The results of E-nose and E-tongue showed overall flavor profile in SSAT for 3 weeks was similar to that of SSAA for 1 week, and 6 weeks (SSAT) was similar to 2 weeks (SSAA). In SS, a total of 35 odor-active compounds were identified and quantitated, and 22 compounds with odor activity value ≥1 were determined as key odorants. The compounds with the highest concentration were 4-hydroxy-2,5-dimethyl-3(2H)-furanone (28,756 μg/mL), followed by acetic acid (8838 μg/mL) and maltol (7984 μg/mL). The heatmap and hierarchical cluster analysis indicated that the concentrations of key odorants and amino acids in SSAT for 3 weeks was close to those of SSAA for 1 week, and 6 weeks (SSAT) was similar to 2 weeks (SSAA). Based on the results obtained above, it was concluded that the flavor changes in SSAA for 1 week were equivalent to those in SSAT for 3 weeks.

Small particles and heterotrophic protists support the mesopelagic zooplankton food web in the subarctic northeast Pacific Ocean

AbstractA quantitative understanding of the mesopelagic zooplankton food web is key to development of accurate carbon budgets and geochemical models in marine systems. Here we use compound specific nitrogen stable isotope analysis of amino acids to quantify the trophic structure of the microzooplankton and mesozooplankton community during summer in the subarctic northeast Pacific Ocean during the EXport Processes in the Ocean from Remote Sensing (EXPORTS) field campaign. Source amino acid values in particles and zooplankton provide strong evidence that basal resources for the mesopelagic zooplankton food web were primarily small (), suspended or slow‐sinking particles, but that surface organic matter delivered by vertically migrating zooplankton may have also been important. Comparisons of values of source and trophic amino acids provide estimates of food web length, which decrease significantly with depth and suggest that protistan microzooplankton are key components of the food web from the surface to at least 500. These results emphasize the importance of small particles as a source of carbon and nitrogen to mesopelagic communities in this region, support observations of an inverse relationship between zooplankton vertical migration and small particles as sources of carbon to deep‐sea food webs in low productivity environments, and document the role of heterotrophic protists as key trophic intermediaries in the mesopelagic zone at this location.

Deconvolving mechanisms of particle flux attenuation using nitrogen isotope analyses of amino acids

AbstractParticulate organic matter settling out of the euphotic zone is a major sink for atmospheric carbon dioxide and serves as a primary food source to mesopelagic food webs. Degradation of this organic matter encompasses a suite of mechanisms that attenuate flux, including heterotrophic metabolic processes of microbes and metazoans. The relative contributions of microbial and metazoan heterotrophy to flux attenuation, however, have been difficult to determine. We present results of compound specific nitrogen isotope analysis of amino acids of sinking particles from sediment traps and size‐fractionated particles from in situ filtration between the surface and 500 m at Ocean Station Papa, collected during NASA EXPORTS (EXport Processes in the Ocean from RemoTe Sensing). With increasing depth, we observe: (1) that, based on the δ15N values of threonine, fecal pellets dominate the sinking particle flux and that attenuation of downward particle flux occurs largely via disaggregation in the upper mesopelagic; (2) an increasing trophic position of particles in the upper water column, reflecting increasing heterotrophic contributions to the nitrogen pool and the loss of particles via remineralization; and (3) increasing δ15N values of source amino acids in submicron and small (1–6 μm) particles, reflecting microbial particle solubilization. We further employ a Bayesian mixing model to estimate the relative proportions of fecal pellets, phytodetritus, and microbially degraded material in particles and compare these results and our interpretations of flux attenuation mechanisms to other, independent methods used during EXPORTS.

Formation and characterization of hollow particles with zein-WPI hybrid shell for curcumin encapsulation

Hollow particles contain the inner aqueous compartment surrounding by a shell layer. Controllable construction of the shell layer may improve the potential use of hollow particles for encapsulating polyphenols. In this study, a novel method with alkaline-heat treatment was developed to fabricate the hollow particles with a hybrid shell of zein and whey protein isolate (WPI). Hollow particles were characterized in terms of soluble proteins, size distribution, ζ-potential, hollow structure and shell hydrophobicity. WPI at 0.25% (w/v) was enough to stabilize its zein complex hollow particles at neutral condition. The size of zein-WPI hollow particles was respectively 90 and 198 nm at pH 11 and 7, with a greater portion of proteins participated in the formation of hollow particles at pH 7 than 11. The formation mechanism of hollow particles was analyzed in terms of circular dichroism, infrared spectroscopy, dissociation test, gel electrophoresis, sulfhydryl contents and amino acid analysis. Hydrophobic interactions played a dominant role in stabilizing the shell structure of zein-WPI hollow particles, while Cys, Tyr and Lys participated in the covalent interaction between zein and WPI in hollow particles. Moreover, the shell hydrophobicity decreased by the presence of WPI, which provided a suitable microenvironment for the encapsulation of curcumin at pH 7. The findings of this study shed light on the design of protein-based hollow particles for the delivery of bioactive compounds.