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Ammonium acetate ACS reagent, ≥97%; CAS Number: 631-61-8; EC Number: 211-162-9; Linear Formula: CH3CO2NH4; find Sigma-Aldrich-238074 MSDS, related peer-reviewed papers, technical documents, similar products & more at Sigma-Aldrich

Ammonium acetate ACS reagent, = 97 631-61-8

Ammonium acetate

Separation of the Positional Isomer Quinocide from the Anti-Malarial Drug Primaquine Using a Discovery? HS F5 HPLC Column.	

Selective inhibition of benzyl ether hydrogenolysis with Pd/C due to the presence of ammonia, pyridine or ammonium acetate.      

Reactions of phenanthraquinone and retenequinone with aldehydes and ammonium acetate in acetic acid solution1.

A new selective preparation of 4H-chromenes by reaction of alkyl cyanoacetate with 3, 5-dibromosalicylaldehyde in the presence of ammonium acetate.

Untargeted liquid chromatography-mass spectrometry (LC-MS)-based metabolomics studies are usually carried out in both positive and negative ion modes; however, it is frequently ignored that the optimal conditions in positive ion mode and negative ion mode are often not the same. We carried out a systematic investigation on urine samples to evaluate the additive effects in negative ion mode. It was found that the widely used conditions, 0.1% formic acid (FA) and NH(4)Ac at different pH, are far from the optimum for untargeted urine metabolomics studies. Compared to 0.1% FA, the use of 1 mM acetic acid (HAc) resulted in almost three times as many detected peaks (401 vs 148) and around five times the size of the peak area (33.55 × 10(6) vs 6.47 × 10(6)). The remarkable improvement can be explained by two factors: (i) a significantly enhanced ionization efficiency due to the combination of an appropriate pH at around 4.0-4.5, the reducibility of H(+), and the high gas-phase basicity of Ac(-) and (ii) a reproducible LC separation due to an acceptable buffering capacity. Our study revealed the importance and necessity of additive optimization, which can be of benefit in related metabolomics studies.

Enhancing the power of liquid chromatography-mass spectrometry-based urine metabolomics in negative ion mode by optimization of the additive.

Nicotinamide adenine dinucleotide (NAD+) is modulated by conditions of metabolic stress and has been reported to decline with aging in preclinical models, but human data are sparse. Nicotinamide riboside (NR) supplementation ameliorates metabolic dysfunction in rodents. We aimed to establish whether oral NR supplementation in aged participants can increase the skeletal muscle NAD+ metabolome and if it can alter muscle mitochondrial bioenergetics. We supplemented 12 aged men with 1 g NR per day for 21 days in a placebo-controlled, randomized, double-blind, crossover trial. Targeted metabolomics showed that NR elevated the muscle NAD+ metabolome, evident by increased nicotinic acid adenine dinucleotide and nicotinamide clearance products. Muscle RNA sequencing revealed NR-mediated downregulation of energy metabolism and mitochondria pathways, without altering mitochondrial bioenergetics. NR also depressed levels of circulating inflammatory cytokines. Our data establish that oral NR is available to aged human muscle and identify anti-inflammatory effects of NR.

Nicotinamide Riboside Augments the Aged Human Skeletal Muscle NAD+ Metabolome and Induces Transcriptomic and Anti-inflammatory Signatures.

Autism affects males more than females, giving rise to the idea that the influence of steroid hormones on early fetal brain development may be one important early biological risk factor. Utilizing the Danish Historic Birth Cohort and Danish Psychiatric Central Register, we identified all amniotic fluid samples of males born between 1993 and 1999 who later received ICD-10 (International Classification of Diseases, 10th Revision) diagnoses of autism, Asperger syndrome or PDD-NOS (pervasive developmental disorder not otherwise specified) (n=128) compared with matched typically developing controls. Concentration levels of Δ4 sex steroids (progesterone, 17α-hydroxy-progesterone, androstenedione and testosterone) and cortisol were measured with liquid chromatography tandem mass spectrometry. All hormones were positively associated with each other and principal component analysis confirmed that one generalized latent steroidogenic factor was driving much of the variation in the data. The autism group showed elevations across all hormones on this latent generalized steroidogenic factor (Cohen's d=0.37, P=0.0009) and this elevation was uniform across ICD-10 diagnostic label. These results provide the first direct evidence of elevated fetal steroidogenic activity in autism. Such elevations may be important as epigenetic fetal programming mechanisms and may interact with other important pathophysiological factors in autism.

Elevated fetal steroidogenic activity in autism.

This study evaluated the effect of the probiotics Pediococcus acidilactici and Saccharomyces cerevisiae boulardii on the intestinal colonization of O149 enterotoxigenic Escherichia coli harbouring the F4 (K88) fimbriae (ETEC F4) and on the expression of ileal cytokines in weaned pigs. At birth, different litters of pigs were randomly assigned to one of the following treatments: 1) control without antibiotics or probiotics (CTRL); 2) reference group in which chlortetracycline and tiamulin were added to weanling feed (ATB); 3) P. acidilactici; 4) S. cerevisiae boulardii; or 5) P. acidilactici + S. cerevisiae boulardii. Probiotics were administered daily (1 × 10(9) CFU per pig) during the lactation period and after weaning (day 21). At 28 days of age, all pigs were orally challenged with an ETEC F4 strain, and a necropsy was performed 24 h later. Intestinal segments were collected to evaluate bacterial colonization in the small intestine and ileal cytokine expressions. Attachment of ETEC F4 to the intestinal mucosa was significantly reduced in pigs treated with P. acidilactici or S. cerevisiae boulardii in comparison with the ATB group (P = 0.01 and P = 0.03, respectively). In addition, proinflammatory cytokines, such as IL-6, were upregulated in ETEC F4 challenged pigs treated with P. acidilactici alone or in combination with S. cerevisiae boulardii compared with the CTRL group. In conclusion, the administration of P. acidilactici or S. cerevisiae boulardii was effective in reducing ETEC F4 attachment to the ileal mucosa, whereas the presence of P. acidilactici was required to modulate the expression of intestinal inflammatory cytokines in pigs challenged with ETEC F4.

Administration of probiotics influences F4 (K88)-positive enterotoxigenic Escherichia coli attachment and intestinal cytokine expression in weaned pigs.

The conditions for the analysis of selected doping substances by UHPSFC-MS/MS were optimized to ensure suitable peak shapes and maximized MS responses. A representative mixture of 31 acidic and basic doping agents was analyzed, in both ESI+ and ESI- modes. The best compromise for all compounds in terms of MS sensitivity and chromatographic performance was obtained when adding 2% water and 10mM ammonium formate in the CO2/MeOH mobile phase. Beside mobile phase, the nature of the make-up solvent added for interfacing UHPSFC with MS was also evaluated. Ethanol was found to be the best candidate as it was able to compensate for the negative effect of 2% water addition in ESI- mode and provided a suitable MS response for all doping agents. Sensitivity of the optimized UHPSFC-MS/MS method was finally assessed and compared to the results obtained in conventional UHPLC-MS/MS. Sensitivity was improved by 5-100-fold in UHPSFC-MS/MS vs. UHPLC-MS/MS for 56% of compounds, while only one compound (bumetanide) offered a significantly higher MS response (4-fold) under UHPLC-MS/MS conditions. In the second paper of this series, the optimal conditions for UHPSFC-MS/MS analysis will be employed to screen >100 doping agents in urine matrix and results will be compared to those obtained by conventional UHPLC-MS/MS.

Ultra high performance supercritical fluid chromatography coupled with tandem mass spectrometry for screening of doping agents. I: Investigation of mobile phase and MS conditions.

A high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, using hydrophilic interaction liquid chromatography (HILIC) chromatography for the analysis of fosfomycin in human plasma and urine, has been developed and validated. The plasma method uses a simple protein precipitation using a low volume sample (10 μL) and is suitable for the concentration range of 1 to 2000 μg/mL. The urine method involves a simple dilution of 10 μL of sample and is suitable for a concentration range of 0.1 to 10 mg/mL. The plasma and urine results, reported, respectively, are for recovery (68, 72%), inter-assay precision (≤9.1%, ≤8.1%) and accuracy (range -7.2 to 3.3%, -1.9 to 1.6%), LLOQ precision (4.7%, 3.1%) and accuracy (1.7% and 1.2%), and includes investigations into the linearity, stability and matrix effects. The method was used in a pilot pharmacokinetic study of a critically ill patient receiving i.v. fosfomycin, which measured a maximum and minimum plasma concentration of 222 μg/mL and 172 μg/mL, respectively, after the initial dose, and a maximum and minimum plasma concentration of 868 μg/mL and 591μg/mL, respectively, after the fifth dose. The urine concentration was 2.03 mg/mL after the initial dose and 0.29 mg/mL after the fifth dose.

A simple LC-MS/MS method using HILIC chromatography for the determination of fosfomycin in plasma and urine: application to a pilot pharmacokinetic study in humans.

One of the factors preventing clinical application of regenerative medicine to degenerative cartilage diseases is a suitable source of cells. Chondrocytes, the only cell type of cartilage, grown in vitro under culture conditions to expand cell numbers lose their phenotype along with the ability to generate hyaline cartilaginous tissue. In this study we determine that a serum- and growth-factor-free three-dimensional (3D) culture system restores the ability of the passaged chondrocytes to form cartilage tissue in vitro, a process that involves sox9. Bovine articular chondrocytes were passaged twice to allow for cell number expansion (P2) and cultured at high density on 3D collagen-type-II-coated membranes in high glucose content media supplemented with insulin and dexamethasone (SF3D). The cells were characterized after monolayer expansion and following 3D culture by flow cytometry, gene expression, and histology. The early changes in signaling transduction pathways during redifferentiation were characterized. The P2 cells showed a progenitor-like antigen profile of 99% CD44(+) and 40% CD105(+) and a gene expression profile suggestive of interzone cells. P2 in SF3D expressed chondrogenic genes and accumulated extracellular matrix. Downregulating insulin receptor (IR) with HNMPA-(AM3) or the PI-3/AKT kinase pathway (activated by insulin treatment) with Wortmannin inhibited collagen synthesis. HNMPA-(AM3) reduced expression of Col2, Col11, and IR genes as well as Sox6 and -9. Co-immunoprecipitation and chromatin immunoprecipitation analyses of HNMPA-(AM3)-treated cells showed binding of the coactivators Sox6 and Med12 with Sox9 but reduced Sox9-Col2a1 binding. We describe a novel culture method that allows for increase in the number of chondrocytes and promotes hyaline-like cartilage tissue formation in part by insulin-mediated Sox9-Col2a1 binding. The suitability of the tissue generated via this approach for use in joint repair needs to be examined in vivo.

Serum- and growth-factor-free three-dimensional culture system supports cartilage tissue formation by promoting collagen synthesis via Sox9-Col2a1 interaction.

Structural variations in genomes are commonly studied by (micro)array-based comparative genomic hybridization. The data analysis methods to infer copy number variation in model organisms (human, mouse) are established. In principle, the procedures are based on signal ratios between test and reference samples and the order of the probe targets in the genome. These procedures are less applicable to experiments with non-model organisms, which frequently comprise non-sequenced genomes with an unknown order of probe targets. We therefore present an additional analysis approach, which does not depend on the structural information of a reference genome, and quantifies the presence or absence of a probe target in an unknown genome. The principle is that intensity values of target probes are compared with the intensities of negative-control probes and positive-control probes from a control hybridization, to determine if a probe target is absent or present. In a test, analyzing the genome content of a known bacterial strain: Staphylococcus aureus MRSA252, this approach proved to be successful, demonstrated by receiver operating characteristic area under the curve values larger than 0.9995. We show its usability in various applications, such as comparing genome content and validating next-generation sequencing reads from eukaryotic non-model organisms.

Absence/presence calling in microarray-based CGH experiments with non-model organisms.

Chlorhexidine may cause type I and type IV allergy. Some chlorhexidine-allergic individuals have been exposed in the healthcare setting as patients or healthcare workers, but for others the source of sensitization is unknown. Chlorhexidine may be used as a preservative or an antimicrobial agent in cosmetic products at a concentration up to 0.3%, as set by the European Cosmetics Directive (now Regulations). To identify cosmetic product types containing chlorhexidine, and to measure the concentration of chlorhexidine in selected products. Between February 2013 and April 2013, we checked for chlorhexidine in cosmetic products in 14 supermarkets, one hairdressing salon and one beauty and retail store in Copenhagen, Denmark by reading the ingredient labels. The chlorhexidine concentration was measured in 10 selected products by high-performance liquid chromatography (HPLC) with an ultraviolet (UV) detector. Chlorhexidine was found in 80 of 2251 checked products (3.6%) in the following categories: hair products (57/760), creams (9/324), face washes (4/24), wet wipes (4/63), skin tonics (3/22), make-up removers (2/25), and mouth washes (1/17). Chlorhexidine concentrations were 0.01-0.15%. We found chlorhexidine in various cosmetic product types, predominantly aimed at females, and in hair products. The measured chlorhexidine concentrations were all within the permitted limit. The relevance for allergic sensitization should be further explored.

Chlorhexidine in cosmetic products - a market survey.

The current project was undertaken with the aim to propose and test an in-depth integrative analysis of neuropharmacokinetic (neuroPK) properties of new chemical entities (NCEs), thereby optimizing the routine of evaluation and selection of novel neurotherapeutics. Forty compounds covering a wide range of physicochemical properties and various CNS targets were investigated. The combinatory mapping approach was used for the assessment of the extent of blood-brain and cellular barriers transport via estimation of unbound-compound brain (Kp,uu,brain) and cell (Kp,uu,cell) partitioning coefficients. Intra-brain distribution was evaluated using the brain slice method. Intra- and sub-cellular distribution was estimated via calculation of unbound-drug cytosolic and lysosomal partitioning coefficients. Assessment of Kp,uu,brain revealed extensive variability in the brain penetration properties across compounds, with a prevalence of compounds actively effluxed at the blood-brain barrier. Kp,uu,cell was valuable for identification of compounds with a tendency to accumulate intracellularly. Prediction of cytosolic and lysosomal partitioning provided insight into the subcellular accumulation. Integration of the neuroPK parameters with pharmacodynamic readouts demonstrated the value of the proposed approach in the evaluation of target engagement and NCE selection. With the rather easily-performed combinatory mapping approach, it was possible to provide quantitative information supporting the decision making in the drug discovery setting.

Mechanistic understanding of brain drug disposition to optimize the selection of potential neurotherapeutics in drug discovery.

Glucocorticoids (GCs) are produced by the adrenal glands and circulate in the blood to coordinate organismal physiology. In addition, different tissues may independently regulate their local GC levels via local GC synthesis. Here, we find that in the mouse, endogenous GCs show tissue-specific developmental patterns, rather than mirroring GCs in the blood. Using solid-phase extraction, HPLC, and specific immunoassays, we quantified endogenous steroids and found that in tissues of female and male mice, (1) local GC levels can be much higher than systemic GC levels, (2) local GCs follow age-related patterns different from those of systemic GCs, and (3) local GCs have identities different from those of systemic GCs. For example, whereas corticosterone is the predominant circulating adrenal GC in mice, high concentrations of cortisol were measured in neonatal thymus, bone marrow, and heart. The presence of cortisol was confirmed with liquid chromatography-tandem mass spectrometry. In addition, gene expression of steroidogenic enzymes was detected across multiple tissues, consistent with local GC production. Our results demonstrate that local GCs can differ from GCs in circulating blood. This finding suggests that steroids are widely used as local (paracrine or autocrine) signals, in addition to their classic role as systemic (endocrine) signals. Local GC regulation may even be the norm, rather than the exception, especially during development.

Steroid profiling reveals widespread local regulation of glucocorticoid levels during mouse development.

An intrinsic performance comparison is made of the reduction in analysis time that can be obtained when switching from HPLC to UHPLC column formats in HILIC and reversed-phase conditions. A detailed overview of the packing characteristics of both stationary phase types is given first. It is demonstrated that HILIC columns demonstrate higher external porosity values than their reversed-phase counterparts resulting in lower flow resistance values. Column total porosity values determined from the elution time of a small marker molecule are shown to depend strongly on the composition of the mobile phase. To omit errors that might arise from an over- or underestimation of the column void time, all plate height and kinetic plot data are therefore expressed as a function of the interstitial velocity. Although only a limited number of columns are evaluated in this study, it is shown that the column efficiency of the HILIC columns is lower than that of their reversed-phase counterparts, at least for the compounds evaluated here. Despite this lower efficiency, the kinetic performance of both stationary phase types is similar, due to the much lower viscosity of the mobile phases typically used in HILIC conditions. Finally, it is demonstrated that a similar, yet slightly larger reduction in analysis time can be obtained when switching from HPLC column formats to UHPLC formats in HILIC compared to reversed-phase conditions.

Evaluation and comparison of the kinetic performance of ultra-high performance liquid chromatography and high-performance liquid chromatography columns in hydrophilic interaction and reversed-phase liquid chromatography conditions.

A subgroup of obese individuals, referred to as metabolically healthy obese (MHO), have preserved insulin sensitivity and a normal lipid profile despite being obese. The molecular basis for this improved cardiometabolic profile remains unclear. Our objective was to integrate metabolite and gene expression profiling to elucidate the molecular distinctions between MHO and metabolically unhealthy obese (MUO) phenotypes. A subset of individuals were selected from the Diabetes Risk Assessment study and classified into three groups using anthropometric and clinical measurements: lean healthy (LH), MHO, and MUO. Serum metabolites were profiled using gas chromatography coupled to mass spectrometry. Multivariate data analysis uncovered metabolites that differed between groups, and these were subsequently validated by capillary electrophoresis coupled to mass spectrometry. Subcutaneous adipose tissue (SAT) gene expression profiling using microarrays was performed in parallel. Amino acids were the most relevant class of metabolites distinguishing MHO from MUO individuals. Serum levels of glutamic acid, valine, and isoleucine were positively associated (i.e., LH < MHO < MUO) with homeostasis model assessment-insulin resistance (HOMA-IR) and glycated hemoglobin (HbA1c) values, while leucine was only correlated with HOMA-IR. The glutamine-to-glutamic acid ratio and glycine were inversely correlated (i.e., LH > MHO > MUO) with HbA1c values. Concomitantly, SAT gene expression profiling revealed that genes related to branched-chain amino acid catabolism and the tricarboxylic acid cycle were less down-regulated in MHO individuals compared to MUO individuals. Together, this integrated analysis revealed that MHO individuals have an intermediate amino acid homeostasis compared to LH and MUO individuals.

Serum and adipose tissue amino acid homeostasis in the metabolically healthy obese.

Free arachidonic acid is functionally interlinked with different lipid signaling networks including those involving prostanoid pathways, the endocannabinoid system, N-acylethanolamines, as well as steroids. A sensitive and specific LC-MS/MS method for the quantification of arachidonic acid, prostaglandin E2, thromboxane B2, anandamide, 2-arachidonoylglycerol, noladin ether, lineoyl ethanolamide, oleoyl ethanolamide, palmitoyl ethanolamide, steroyl ethanolamide, aldosterone, cortisol, dehydroepiandrosterone, progesterone, and testosterone in human plasma was developed and validated. Analytes were extracted using acetonitrile precipitation followed by solid phase extraction. Separations were performed by UFLC using a C18 column and analyzed on a triple quadrupole MS with electron spray ionization. Analytes were run first in negative mode and, subsequently, in positive mode in two independent LC-MS/MS runs. For each analyte, two MRM transitions were collected in order to confirm identity. All analytes showed good linearity over the investigated concentration range (r>0.98). Validated LLOQs ranged from 0.1 to 190ng/mL and LODs ranged from 0.04 to 12.3ng/mL. Our data show that this LC-MS/MS method is suitable for the quantification of a diverse set of bioactive lipids in plasma from human donors (n=32). The determined plasma levels are in agreement with the literature, thus providing a versatile method to explore pathophysiological processes in which changes of these lipids are implicated.

A quantitiative LC-MS/MS method for the measurement of arachidonic acid, prostanoids, endocannabinoids, N-acylethanolamines and steroids in human plasma.

Most stationary phases for hydrophilic interaction liquid chromatography (HILIC) and reversed phase liquid chromatography (RPLC) are based on silica. Porous graphitic carbon (PGC) is an attractive alternative to silica-based phases due to its chemical and thermal stability, and unique selectivity. However, native PGC is strongly hydrophobic and in some instances excessively retentive. PGC particles with covalently attached aniline groups (Dimethylaniline-PGC and Aniline-PGC) were synthesized to alter the surface polarity of PGC. First, the diazonium salt of N,N-dimethyl-p-phenylenediamine or 4-nitroaniline was adsorbed onto the PGC surface. The adsorbed salt was reduced with sodium borohydride and (Aniline-PGC only) the nitro group was further reduced with iron powder to the aniline. X-ray photoelectron spectroscopy confirmed the surface functionalities and that these moieties were introduced to the surface at concentrations of 0.9 and 2.1molecules/nm(2), respectively. These modified PGC phases (especially Aniline-PGC) were evaluated as HILIC and reversed phases. The Dimethylaniline-PGC phase displayed only weak HILIC retention of phenolic solutes. In contrast, the Aniline-PGC phase displayed up to nearly a 7-fold increase in HILIC retention vs. an aniline-silica phase and selectivity that differed from 10 other HILIC phases. Introduction of aniline groups to the PGC surface reduced the RPLC retentivity of PGC up to more than 5-fold and improved the separation efficiency up to 6-fold. The chromatographic performance of Aniline-PGC is demonstrated by separations of nucleotides, nucleosides, carboxylic acids, basic pharmaceuticals, and other compounds.

Ammonium acetate

ACS reagent, ≥97%

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InChI

InChI key

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