Cellular and mitochondrial determination of low molecular mass organic acids by LC-MS/MS

A selective and sensitive method for the determination of low molecular mass organic acids (LMMOAs) in cell and mitochondrial extracts is presented. The analytical method consists in the separation by reversed phase liquid chromatography and detection with tandem mass spectrometry (LC-MS/MS) of the LMMOAs like malic, succinic, formic and citric acids. These acids are among the cellular intermediates of the tricarboxylic acid cycle (TCA), thus their quantitation can provide essential information about the catabolic and anabolic processes occurring in cells under physiological and pathological conditions. The analytical method was fully validated in terms of linearity, detection and quantification limits, recovery and precision. Detection limits (LOD) for malic, succinic and fumaric acids were in the range of 1-10nM, while 20nM was obtained for citric acid. Analytical recovery in cell and mitochondrial extracts was found between 88 and 105% (CV% ≤7.1) and matrix effect was estimated to be less than 108%. The LC-MS/MS method applied to the quantification of TCA cycle metabolites revealed a different distribution of the four acids in cells and mitochondria, and it could be used to monitoring metabolic alterations associated with TCA cycle and oxidative phosphorylation dysfunctions.

Combined effects of low-molecular-weight organic acids on mobilization of arsenic and lead from multi-contaminated soils

A batch experiment was conducted to examine the combined effects of three common low-molecular-weight organic acids (LMWOAs) on the mobilization of arsenic and lead in different types of multi-contaminated soils. The capacity of individual LMWOAs (at a same molar concentration) to mobilize soil-borne As and Pb varied significantly. The combination of the organic acids did not make a marked "additive" effect on the mobilization of the investigated three elements. An "antagonistic" effect on element mobilization was clear in the treatments involving oxalic acid for some soils. The acid strength of a LMWOA did not play an important role in controlling the mobilization of elements. While the mobilization of As and Pb was closely associated with the dissolution of soil-borne Fe, soil properties such as original soil pH, organic matter contents and the total amount of the element relative to the total Fe markedly complicated the mobility of that element. Aging led to continual consumption of proton introduced from addition of LMWOAs and consequently caused dramatic changes in solution-borne Fe, which in turn resulted in change in As and Pb in the soil solution though different elements behaved differently.

Influence of deficit irrigation on strawberry (Fragaria × ananassa Duch.) fruit quality

BACKGROUND

Three different irrigation regimes - upper limit of field capacity (UFC), -12 kPa); lower limit of field capacity (LFC), -33 kPa; and deficit irrigation (DI), -70 kPa) were established on silty-loam soil and monitored with tensiometers. Yield and fruit quality of 'Flamenco' and 'Eva's Delight' ever-bearing strawberry cultivars were monitored. The aim of the study was to evaluate the effect of different irrigation regimes on the content of sugars, organic acids and phenolic compounds using high-performance liquid chromatography-mass spectrometry HPLC/HPLC-MS.

RESULTS

Deficit irrigation significantly increased the content of sugars (from 1.1- to 1.3 fold), organic acids (from 1.1- to 1.3-fold), their ratio (from 1.1- to 1.2-fold) and the content of most identified phenolics in cv. 'Flamenco'. Conversely, higher amounts of total sugars and organic acids (1.7- to 1.8-fold) were detected in 'Eva's Delight' strawberries at UFC and LFC irrigation. Deficit irrigation generally decreased strawberry yield of cv. 'Eva's Delight'.

CONCLUSION

The results suggest superior fruit quality and taste of strawberries grown under minor deficit irrigation for cv. 'Flamenco'. © 2016 Society of Chemical Industry.

Bioaccumulation and distribution of perfloroalkyl acids in seafood products from Bohai Bay, China

Ten perfluoroalkyl acids (PFAAs) were measured in seafood collected from Bohai Bay, China in 2010. The summed concentrations of the PFAAs were in the ranges of not detected to 194 ng/g dry weight and 4.0 to 304 ng/g dry weight for invertebrates and fish, respectively. The levels of perflurooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA) in the seafood were lower than those from North America, the Mediterranean Sea, and South Korea. Living habitat, trophic level, and feeding habits had important impacts on the bioaccumulation and distribution of PFAAs in the seafood. The species at higher trophic levels had the potential to accumulate more PFAAs than benthic invertebrates. Tidal-flat organisms tended to accumulate more PFOA than PFOS, whereas the opposite was seen for shallow-water species. For all the species, PFOS and PFOA were partitioned preferentially in the liver or viscera. Risk assessment indicated that the current level of PFAAs in the seafood of Bohai Bay does not represent an immediate source of harm to public health.

Quantifying instantaneous regeneration rates of plant leaf waxes using stable hydrogen isotope labeling

Leaf waxes protect terrestrial plants from biotic and abiotic stresses and are important sedimentary biomarkers for terrestrial plants. Thus, understanding the production and ablation of leaf waxes is critical in plant physiology and for geochemical studies. However, there have been no accurate approaches to quantify leaf wax production at different time scales. In this study, we demonstrate a novel approach to study leaf wax regeneration by irrigating plants with a pulse of deuterium-enriched water, followed by measurements of leaf wax D/H ratios by gas chromatography/isotope-ratio mass spectrometry (GC/IRMS). We demonstrate the efficacy of this approach using the grass species Phleum pratense in a greenhouse environment. Using a binary isotope mass balance model, we are able to quantify the regeneration rates of the C(16), C(18) acids and leaf waxes (C(23)-C(31) n-alkanes; C(22)-C(30) n-acids) over a diurnal cycle. Our results show that within one day 33-47% of C(16) and C(18) acids are regenerated, and thus the recycling time for these compounds is 2-3 days. For C(22)-C(26) n-alkyl lipids, 7-21% are regenerated within one day and thus they require 5-16 days to recycle. In comparison, the recycling time for long-chain n-alkyl lipids (C(27)-C(31)) is as long as 71-128 days. Our approach can be applied to different plants at shorter or longer time scales by adjusting the degree of isotopic labeling, sampling intervals and the amount of irrigation water.

Size distributions of aerosol and water-soluble ions in Nanjing during a crop residual burning event

To investigate the impact on urban air pollution by crop residual burning outside Nanjing, aerosol concentration, pollution gas concentration, mass concentration, and water-soluble ion size distribution were observed during one event of November 4-9, 2010. Results show that the size distribution of aerosol concentration is bimodal on pollution days and normal days, with peak values at 60-70 and 200-300 nm, respectively. Aerosol concentration is 10(4) cm(-3) x nm(-1) on pollution days. The peak value of spectrum distribution of aerosol concentration on pollution days is 1.5-3.3 times higher than that on a normal day. Crop residual burning has a great impact on the concentration of fine particles. Diurnal variation of aerosol concentration is trimodal on pollution days and normal days, with peak values at 03:00, 09:00 and 19:00 local standard time. The first peak is impacted by meteorological elements, while the second and third peaks are due to human activities, such as rush hour traffic. Crop residual burning has the greatest impact on SO2 concentration, followed by NO2, O3 is hardly affected. The impact of crop residual burning on fine particles (< 2.1 microm) is larger than on coarse particles (> 2.1 microm), thus ion concentration in fine particles is higher than that in coarse particles. Crop residual burning leads to similar increase in all ion components, thus it has a small impact on the water-soluble ions order. Crop residual burning has a strong impact on the size distribution of K+, Cl-, Na+, and F- and has a weak impact on the size distributions of NH4+, Ca2+, NO3- and SO4(2-).

Polar organic marker compounds in PM2.5 aerosol from a mixed forest site in western Germany

The molecular composition of PM2.5 (particulate matter with an aerodynamic diameter <2.5 microm) aerosol samples collected during a very warm and dry 2003 summer period at a mixed forest site in Jülich, Germany, was determined by gas chromatography/mass spectrometry in an effort to evaluate photooxidation products of biogenic volatile organic compounds (BVOCs) and other markers for aerosol source characterization. Six major classes of compounds represented by twenty-four individual organic species were identified and measured, comprising tracers for biomass combustion, short-chain acids, fatty acids, sugars/sugar alcohols, and tracers for the photooxidation of isoprene and alpha-/beta-pinene. The tracers for the photooxidation of alpha-/beta-pinene include two compounds, 3-hydroxyglutaric acid and 3-methyl-1,2,3-butanetricarboxylic acid, which have only recently been elucidated. The characteristic molecular distribution of the fatty acids with a strong even/odd number carbon preference indicates a biological origin, while the presence of isoprene and terpene secondary organic aerosol products suggests that the photooxidation of BVOCs contributes to aerosol formation at this site. The sum of the median concentrations of the isoprene oxidation products was 21.2 ng m(-3), while that of the terpene oxidation products was 19.8 ng m(-3). On the other hand, the high median concentration of malic acid (37 ng m(-3)) implies that photooxidation of unsaturated fatty acids should also be considered as an important aerosol source process. In addition, the occurrence of levoglucosan and pyrogallol indicates that the site is affected by biomass combustion. Their median concentrations were 30 and 8.9 ng m(-3), respectively.

Corn hybrid affects in vitro and in vivo measures of nutrient digestibility in dogs

Corn is a commonly used ingredient in dry pet foods because there is a stable supply and it is a relatively inexpensive source of nutrients. Corn hybrids are available that are higher in CP and amylose and lower in phytate concentration than conventional hybrids. Approximately 500 mg of high-protein (HP), high-protein, low-phytate (HPLP), and high-amylose (HA) corn were compared with conventional (CONV) corn and amylomaize starch (AM) in triplicate and exposed to pepsin/hydrochloric acid and pancreatin to simulate hydrolytic digestion. Substrate remaining after this was used to determine in vitro colonic fermentation. Organic matter disappearances as a result of hydrolytic digestion were >80% for CONV, HP, and HPLP, whereas HA (60.7%) and AM (43.7%) were lower (P < 0.05). Total digestion (TD) values after hydrolytic digestion and 8 h of fermentation using canine fecal inoculum were greater (P < 0.05) for CONV, HP, and HPLP vs. HA and AM. The residue left after hydrolytic digestion of all substrates was poorly fermented. Five ileal-cannulated dogs were fed each corn hybrid at approximately 31% of the diet in a 5 x5 Latin square design. Dogs fed diets containing HP corn had higher (P < 0.05) ileal OM digestibility (70.3%) and tended (P < 0.10) to have higher DM digestibility (64.6%). Ileal starch digestibilities were lower (P < 0.05) for dogs fed HA (64.0%) and AM (63.0%). Ileal digestibilities of essential (71.2%), nonessential (67.4%), and total (69.0%) AA tended to be higher (P < 0.10) for HP diets compared with CONV (66.4, 62.4, and 64.0%, respectively). Total-tract DM, OM, CP, and GE digestibilities (77, 82, 77, and 84%, on average, respectively) were higher (P < 0.05) for dogs fed CONV, HP, and HPLP than for those fed AM (66.9, 71.6, 72.6, and 76.5%) and HA (60.6, 65.7, 69.7, and 71.5%). Total-tract fat digestibilities were lower (P < 0.05) for dogs fed HA diets (86.6%) than for all other treatments (91.0%, on average). Total-tract starch digestibilities were higher (P < 0.05) for dogs fed CONV, HP, and HPLP (98%, on average) compared with HA (72.8%) and AM (76.5%). No differences were detected among treatments in fecal bifidobacteria, lactobacilli, or Clostridium perfringens concentrations. The experiments demonstrated that HP and HPLP corn had hydrolytic digestion and fermentation characteristics similar to those of CONV corn, whereas HA resulted in similar responses to AM, a well-established resistant starch ingredient.

Isolation and Structure Determination of Complexed Poly(3-hydroxyalkanoate) from Beet (Beta vulgaris L.)

Complexed poly(3-hydroxyalkanoate)s (cPHAs), one of two types of natural PHAs, occur in both prokaryotes and eukaryotes as a complex with biomacromolecules and could be involved in various physiological functions. In this study, a cPHA-component derived from a complex with calcium polyphosphate was isolated from sugar beet (Beta vulgaris L.) and determined to be a homopolymer composed of 3-hydroxybutyrate. MALDI MS provided the number-average molecular weight (Mn = 9,124 Da) and polydispersity index (PDI = 1.01), showing that beet cPHA has a slightly lower molecular mass than the known Escherichia coli cPHA. In addition, the structural analysis of both end groups showed that (i) 100 mol-% of the carboxyl end is free, while about 30 mol-% of the hydroxyl end is free and about 70 mol-% masked and (ii) the end hydroxyl group is masked by at least six identified short-chain alkanoic and alkanedioic acids. Based on such end-group characteristics, the polymerization mechanism of beet cPHA is discussed.

Microbial population of spruce soil in Tatachia mountain of Taiwan

To investigate the role of microorganisms in the ecology and the nutrient transformation of forest soil, soil property, microbial population, biomass and organic acid content of Spruce soil in Tatachia mountain were determined during January 1997 to November 1999. Soil temperatures were between 5.5 and 15.6 degrees C and soil pH ranged from 3.6 to 5.0. Total organic carbon and nitrogen contents ranged from 5.83% to 34.35% and from 0.90% to 3.19%, respectively. C/N ratio was between 7.07 and 18.24. Each gram of dry soil contained microbial biomass carbon 308-870 microg, microbial biomass nitrogen 107-240 microg, malic acid 74-211 nM and succinic acid 32-175 nM. In addition, each gram of dry organic layer contained microbial biomass carbon 216-653 microg, microbial biomass nitrogen 10.3-33.8 microg, formic acid 256-421 nM, acetic acid 301-435 nM, malic acid 795-1027 nM and succinic acid 204-670 nM. About 45.5-90.9% of topsoil samples had higher microbial population than those of subsoil especially in actinomycetes, cellulolytic and phosphate-solubilizing microorganisms. Although rhizosphere of Spruce had higher total organic carbon and total nitrogen content than non-rhizosphere and dwarf bamboo areas, the microbial population had no significant difference among them.

A study of oral health condition in individuals with no oral hygiene and its association with plaque acidogenesis

OBJECTIVE

To study the association of long-term deposited plaque, due to lack of oral hygiene, with acidogenesis of the plaque bacteria.

METHODS

Seventy-seven subjects with poor oral hygiene were selected. Debris index (DI) and calculus index (CI) were recorded. Among them, 16 were DMFS > 8, and comprised the caries active (CA) group; 27 were caries free, and comprised the caries free (CF) group. Plaque fluids in both groups were analyzed for organic acids, phosphate, and inorganic cations by use of capillary electrophoresis, while pH was measured by microelectrodes.

RESULTS

No differences were found on debris index (CF group measured 2.07-0.47, CA group measured 2.01-0.53) or calculus index (CF group measured 2.47-0.50, CA group measured 2.48-0.53) relative to carious status, although there was a positive relationship between DI and CI (r = 0.52, P < 0.001). The main finding in this study was that the quantity of lactic acid produced by sucrose exposure in these individuals with poor oral hygiene was much less (increased no more than 2 times, compared with content at rest) than in a previous report (increased 3 to 5 times, compared with content at rest) on subjects with good oral hygiene habits.

CONCLUSIONS

Long-term deposited plaque due to lack of oral hygiene may have less cariogenic capability, although patients' susceptibility to periodontal disease would increase.