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Wei Y, Li W, Han Y, Xiong Y, Kuang Y, Zhang J. CdTe based water-soluble fluorescent probe for rapid detection of zilpaterol in swine urine and pork. Food Chem 2024; 445:138668. [PMID: 38367555 DOI: 10.1016/j.foodchem.2024.138668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 01/31/2024] [Accepted: 02/02/2024] [Indexed: 02/19/2024]
Abstract
Zilpaterol hydrochloride (zilpaterol) is used in animal feed as it can increase the lean meat mass. However, consuming zilpaterol-containing animal products may damage human health. Therefore, rapid detection of zilpaterol is attracting increasing research attention. This study aimed to developed a fast, accurate, and ultrasensitive fluorescence immunoassay based on CdTe quantum dots (QDs). A CdTe QD fluorescence sensor was synthesized from thioglycolic acid using a simple hydrothermal method. The morphology and structure of the CdTe QDs were characterized using transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy. The detection limits of our method in swine urine and pork samples were 0.5 μg/L and 1.2 μg/kg, respectively. A wide linear range of 0.1-10000 μg/L (R2 = 0.996) was achieved. Both within-run precision (CVw) and between-run precision (CVb) were ≤ 10 %. The method was then successfully applied for the analysis of zilpaterol contents in swine urine and pork samples.
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Affiliation(s)
- Yihua Wei
- Institute for Quality & Safety and standards of Agricultural products rearch, Jiangxi Academy of Agricultural Sciences, Nanlian Road 602, Nanchang 330200, China
| | - Weihong Li
- Institute for Quality & Safety and standards of Agricultural products rearch, Jiangxi Academy of Agricultural Sciences, Nanlian Road 602, Nanchang 330200, China
| | - Yan Han
- Institute for Quality & Safety and standards of Agricultural products rearch, Jiangxi Academy of Agricultural Sciences, Nanlian Road 602, Nanchang 330200, China
| | - Yan Xiong
- Institute for Quality & Safety and standards of Agricultural products rearch, Jiangxi Academy of Agricultural Sciences, Nanlian Road 602, Nanchang 330200, China
| | - Yuanying Kuang
- Institute for Quality & Safety and standards of Agricultural products rearch, Jiangxi Academy of Agricultural Sciences, Nanlian Road 602, Nanchang 330200, China
| | - Jinyan Zhang
- Institute for Quality & Safety and standards of Agricultural products rearch, Jiangxi Academy of Agricultural Sciences, Nanlian Road 602, Nanchang 330200, China.
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Jang TJ, Yun HS, Hyun CM, Kim JE, Lee SH, Seo JK. Fully automatic integration of dental CBCT images and full-arch intraoral impressions with stitching error correction via individual tooth segmentation and identification. Med Image Anal 2024; 93:103096. [PMID: 38301347 DOI: 10.1016/j.media.2024.103096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 12/31/2023] [Accepted: 01/25/2024] [Indexed: 02/03/2024]
Abstract
We present a fully automated method of integrating intraoral scan (IOS) and dental cone-beam computerized tomography (CBCT) images into one image by complementing each image's weaknesses. Dental CBCT alone may not be able to delineate precise details of the tooth surface due to limited image resolution and various CBCT artifacts, including metal-induced artifacts. IOS is very accurate for the scanning of narrow areas, but it produces cumulative stitching errors during full-arch scanning. The proposed method is intended not only to compensate the low-quality of CBCT-derived tooth surfaces with IOS, but also to correct the cumulative stitching errors of IOS across the entire dental arch. Moreover, the integration provides both gingival structure of IOS and tooth roots of CBCT in one image. The proposed fully automated method consists of four parts; (i) individual tooth segmentation and identification module for IOS data (TSIM-IOS); (ii) individual tooth segmentation and identification module for CBCT data (TSIM-CBCT); (iii) global-to-local tooth registration between IOS and CBCT; and (iv) stitching error correction for full-arch IOS. The experimental results show that the proposed method achieved landmark and surface distance errors of 112.4μm and 301.7μm, respectively.
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Affiliation(s)
- Tae Jun Jang
- School of Mathematics and Computing (Computational Science and Engineering), Yonsei University, Seoul, South Korea
| | - Hye Sun Yun
- School of Mathematics and Computing (Computational Science and Engineering), Yonsei University, Seoul, South Korea.
| | - Chang Min Hyun
- School of Mathematics and Computing (Computational Science and Engineering), Yonsei University, Seoul, South Korea
| | - Jong-Eun Kim
- Department of Prosthodontics, College of Dentistry, Yonsei University, Seoul, South Korea
| | - Sang-Hwy Lee
- Department of Oral and Maxillofacial Surgery, Oral Science Research Center, College of Dentistry, Yonsei University, Seoul, South Korea
| | - Jin Keun Seo
- School of Mathematics and Computing (Computational Science and Engineering), Yonsei University, Seoul, South Korea
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Euler L, Wagener F, Thomas A, Thevis M. Determination and enantioselective separation of zilpaterol in human urine after mimicking consumption of contaminated meat using high-performance liquid chromatography with tandem mass spectrometry techniques. Rapid Commun Mass Spectrom 2022; 36:e9357. [PMID: 35851724 DOI: 10.1002/rcm.9357] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 07/15/2022] [Accepted: 07/16/2022] [Indexed: 06/15/2023]
Abstract
RATIONALE The synthetic β-adrenoreceptor agonist zilpaterol is legitimately used as an animal feed supplement in selected countries due to its known effects on lipolysis and protein biosynthesis. These pharmacological characteristics of zilpaterol have contributed to its classification as doping agent in sport by the World Anti-Doping Agency. However, the use as a feed supplement can lead to residues of the drug in edible tissues and, possibly, also in the urine of consumers. METHODS To provide urinary elimination profiles of microdosed zilpaterol and to determine whether the ingestion of zilpaterol below or at the acceptable daily intake level of 0.04 μg/kg bodyweight can result in an adverse analytical finding (AAF) in doping controls, healthy volunteers were administered single or multiple oral doses of 0.5 μg or 3 μg zilpaterol to mimic ingestion of contaminated cattle meat. Urine samples were collected and analyzed using a validated high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) method and a newly developed chiral high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry (HPLC-APCI-MS/MS) method. RESULTS Urinary peak concentrations of zilpaterol were observed for all volunteers 1.5-12.5 h after ingestion, and maximum levels >5 ng/mL, which would constitute an AAF in doping controls, were found after the intake of 3 μg of zilpaterol on five consecutive days in one out of five study participants. Noteworthy, the enantiomeric ratio of excreted zilpaterol remained constant over time. CONCLUSION This study provides first insights into the urinary excretion of microdosed zilpaterol. Furthermore, a method was successfully developed and applied for the separation of the zilpaterol enantiomers with mass spectrometric detection.
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Affiliation(s)
- Luisa Euler
- Institute of Biochemistry/Center for Preventive Doping Research, German Sport University Cologne, Cologne, Germany
| | - Felicitas Wagener
- Institute of Biochemistry/Center for Preventive Doping Research, German Sport University Cologne, Cologne, Germany
| | - Andreas Thomas
- Institute of Biochemistry/Center for Preventive Doping Research, German Sport University Cologne, Cologne, Germany
| | - Mario Thevis
- Institute of Biochemistry/Center for Preventive Doping Research, German Sport University Cologne, Cologne, Germany
- European Monitoring Center for Emerging Doping Agents (EuMoCEDA), Cologne, Germany
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Rontani JF, Aubert C. Electron ionization mass fragmentation of monounsaturated long-chain α,ω-dicarboxylic acid trimethylsilyl derivatives. Rapid Commun Mass Spectrom 2022; 36:e9321. [PMID: 35485611 DOI: 10.1002/rcm.9321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 04/28/2022] [Accepted: 04/28/2022] [Indexed: 06/14/2023]
Affiliation(s)
| | - Claude Aubert
- Laboratoire de Pharmacocinétique et Toxicocinétique (EA 3286), Faculté de Pharmacie, Marseille, France
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Cosovanu D, Llovera M, Villorbina G, Canela-Garayoa R, Eras J. A simple and fast method for metabolomic analysis by gas liquid chromatography-mass spectrometry. Metabolomics 2021; 17:22. [PMID: 33547979 DOI: 10.1007/s11306-021-01771-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 01/20/2021] [Indexed: 10/22/2022]
Abstract
INTRODUCTION The metabolomic profile is an essential tool for understanding the physiological processes of biological samples and their changes. In addition, it makes it possible to find new substances with industrial applications or use as drugs. As GC-MS is a very common tool for obtaining the metabolomic profile, a simple and fast method for sample preparation is required. OBJECTIVES The aim of this research was to develop a direct derivatization method for GC-MS to simplify the sample preparation process and apply it to a wide range of samples for non-targeted metabolomic analysis purposes. METHODS One pot combined esterification of carboxylic acids with methanol and silylation of the hydroxyl groups was achieved using a molar excess of chlorotrimethylsilane with respect to methanol in the presence of pyridine. RESULTS The metabolome profile obtained from different samples, such as bilberry and cherry cuticles, olive leaves, P. aeruginosa and E. coli bacteria, A. niger fungi and human sebum from the ceruminous gland, shows that the procedure allows the identification of a wide variety of metabolites. Aliphatic fatty acids, hydroxyfatty acids, phenolic and other aromatic compounds, fatty alcohols, fatty aldehydes dimethylacetals, hydrocarbons, terpenoids, sterols and carbohydrates were identified at different MSI levels using their mass spectra. CONCLUSION The metabolomic profile of different biological samples can be easily obtained by GC-MS using an efficient simultaneous esterification-silylation reaction. The derivatization method can be carried out in a short time in the same injection vial with a small amount of reagents.
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Affiliation(s)
- Diana Cosovanu
- Department of Chemistry, DBA Center, ETSEA, University of Lleida, 25003, Lleida, Spain
| | - Montserrat Llovera
- Scientific Technical Service TCEM, University of Lleida, 25003, Lleida, Spain
| | - Gemma Villorbina
- Department of Chemistry, DBA Center, ETSEA, University of Lleida, 25003, Lleida, Spain
| | - Ramon Canela-Garayoa
- Department of Chemistry, DBA Center, ETSEA, University of Lleida, 25003, Lleida, Spain
| | - Jordi Eras
- Department of Chemistry, DBA Center, ETSEA, University of Lleida, 25003, Lleida, Spain.
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Piña-Olmos S, Dolores-Hernández M, Villaseñor A, Díaz-Torres R, Ramírez Bribiesca E, López-Arellano R, Ramírez-Noguera P. Extracellular and intracellular zilpaterol and clenbuterol quantification in Hep G2 liver cells by UPLC-PDA and UPLC-MS/MS. J Pharm Biomed Anal 2020; 195:113817. [PMID: 33303268 DOI: 10.1016/j.jpba.2020.113817] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 11/23/2020] [Accepted: 11/29/2020] [Indexed: 11/17/2022]
Abstract
Zilpaterol and Clenbuterol are β-adrenergic agonists that have been widely used to feed cattle. Although the use of Zilpaterol has been approved, Clenbuterol is still used illegally at unknown doses. However, the research of both substances has been based mainly on the evaluation of residues. To our knowledge, this is the first time that a cellular model using Hep G2 cells treated with Zilpaterol and Clenbuterol is presented as an alternative approach to quantify both drugs at the cellular level. Thus, a complete analytical methodology has been developed for the accurate quantitation of these β-adrenergic agonists in both cellular compartments. We propose the use of ultra-performance liquid chromatography with photodiode array detector (UPLC-PDA) for extracellular determinations while UPLC coupled to a tandem mass spectrometer (UPLC-MS/MS) for intracellular analysis. The methods were fully validated in terms of selectivity, linearity, accuracy, and precision, limits of detection and quantitation (LOD and LOQ, respectively), stability, carryover, and matrix effect. The method for intracellular content was linear ranging from 0.25 to 8 ng/mL while for extracellular content, the concentration of Zilpaterol and Clenbuterol ranged from 0.125 to 4 μg/mL, with correlation coefficients of R > 0.98 and >0.99, respectively. The combination of the two methodologies in the cellular model showed intracellular concentrations of 0.344 ± 0.06 μg/mL and 2.483 ± 0.36 μg/mL for Zilpaterol and Clenbuterol, respectively. Extracellular concentration was 0.728 ± 0.14 μg/mL and 0.822 ± 0.11 μg/mL for Zilpaterol and Clenbuterol, respectively. This work shows the potential applications of cellular modelling in the study of toxicity for the mentioned drugs.
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Affiliation(s)
- Sofia Piña-Olmos
- Laboratorio de Toxicología Celular, Unidad de Investigación Multidisciplinaria, FES-Cuautitlán, Campo 4, Universidad Nacional Autónoma de México, Carretera México-Teoloyucan Km 2.5, San Sebastián Xhala, Cuautitlán Izcalli Estado de México, 54714, Mexico
| | - Mariana Dolores-Hernández
- Laboratorio de Desarrollo Farmacéutico (LEDEFAR), Unidad de Investigación Multidisciplinaria, FES-Cuautitlán, Campo 4, Universidad Nacional Autónoma de México, Carretera México-Teoloyucan Km 2.5, San Sebastián Xhala, Cuautitlán Izcalli Estado de México, 54714, Mexico
| | - Alma Villaseñor
- Instituto de Medicina Molecular Aplicada (IMMA), Departamento de Ciencias Médicas Básicas, Facultad de Medicina, Universidad San Pablo-CEU, CEU Universities, Madrid, Spain
| | - Roberto Díaz-Torres
- Laboratorio de Toxicología Celular, Unidad de Investigación Multidisciplinaria, FES-Cuautitlán, Campo 4, Universidad Nacional Autónoma de México, Carretera México-Teoloyucan Km 2.5, San Sebastián Xhala, Cuautitlán Izcalli Estado de México, 54714, Mexico
| | - Efrén Ramírez Bribiesca
- Programa de Ganadería, Colegio de Posgraduados, Montecillo, Carretera México-Texcoco Km.36.5, Montecillo, Texcoco, 56230, Estado de México, Mexico
| | - Raquel López-Arellano
- Laboratorio de Desarrollo Farmacéutico (LEDEFAR), Unidad de Investigación Multidisciplinaria, FES-Cuautitlán, Campo 4, Universidad Nacional Autónoma de México, Carretera México-Teoloyucan Km 2.5, San Sebastián Xhala, Cuautitlán Izcalli Estado de México, 54714, Mexico
| | - Patricia Ramírez-Noguera
- Laboratorio de Toxicología Celular, Unidad de Investigación Multidisciplinaria, FES-Cuautitlán, Campo 4, Universidad Nacional Autónoma de México, Carretera México-Teoloyucan Km 2.5, San Sebastián Xhala, Cuautitlán Izcalli Estado de México, 54714, Mexico.
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Kumirska J, Łukaszewicz P, Caban M, Migowska N, Plenis A, Białk-Bielińska A, Czerwicka M, Qi F, Piotr S. Determination of twenty pharmaceutical contaminants in soil using ultrasound-assisted extraction with gas chromatography-mass spectrometric detection. Chemosphere 2019; 232:232-242. [PMID: 31154184 DOI: 10.1016/j.chemosphere.2019.05.164] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 05/17/2019] [Accepted: 05/18/2019] [Indexed: 06/09/2023]
Abstract
In this paper, an analytical method for the simultaneous determination of twenty pharmaceuticals (eight non-steroidal anti-inflammatory drugs, five oestrogenic hormones, two antiepileptic drugs, two β-blockers, and three antidepressants) in soils was developed. The optimal method included ultrasound-assisted extraction, a clean-up step on a silica gel column, derivatization using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and 1% trimethylchlorosilane (TMCS) in pyridine and ethyl acetate (2:1:1, v/v/v) for 30 min at 60 °C, and determination by gas chromatography-mass spectrometry working in the selected ion monitoring mode. This affords good resolution, high sensitivity and reproducibility, and freedom from interferences even from complex matrices such as soils. The method detection limits ranged from 0.3 to 1.7 ng g-1, the intra-day precision represented as RSDs ranged from 1.1 to 10.0%, and the intra-day accuracy from 81.3 to 119.7%. The absolute recoveries of the target compounds were above 80%, except for valproic acid and diethylstilbestrol. The developed method was successfully applied in the analysis of the target compounds in soils collected in Poland. Among the 20 pharmaceuticals, 12 compounds were detected at least once in the soils. The determination of antiepileptic drugs, β-blockers, and antidepressants was also performed for the first time.
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Affiliation(s)
- Jolanta Kumirska
- Faculty of Chemistry, University of Gdansk, Wita Stwosza 63, 80-308, Gdańsk, Poland.
| | - Paulina Łukaszewicz
- Faculty of Chemistry, University of Gdansk, Wita Stwosza 63, 80-308, Gdańsk, Poland
| | - Magda Caban
- Faculty of Chemistry, University of Gdansk, Wita Stwosza 63, 80-308, Gdańsk, Poland
| | - Natalia Migowska
- Faculty of Chemistry, University of Gdansk, Wita Stwosza 63, 80-308, Gdańsk, Poland
| | - Alina Plenis
- Department of Pharmaceutical Chemistry, Medical University of Gdańsk, Hallera 107, 80-416, Gdańsk, Poland
| | - Anna Białk-Bielińska
- Faculty of Chemistry, University of Gdansk, Wita Stwosza 63, 80-308, Gdańsk, Poland
| | - Małgorzata Czerwicka
- Faculty of Chemistry, University of Gdansk, Wita Stwosza 63, 80-308, Gdańsk, Poland
| | - Fei Qi
- Key Lab for Source Control Technology of Water Pollution, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, 100083, PR China
| | - Stepnowski Piotr
- Faculty of Chemistry, University of Gdansk, Wita Stwosza 63, 80-308, Gdańsk, Poland
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Abstract
Metabolic profiling by 1H NMR spectroscopy is an underutilized technology in salivary research, although preliminary studies have identified promising results in multiple fields (diagnostics, nutrition, sports physiology). Translation of preliminary findings into validated, clinically approved knowledge is hindered by variability in protocol for the collection, storage, preparation, and analysis of saliva. This study aims to evaluate the effects of differing sample pretreatments on the 1H NMR metabolic profile of saliva. Protocol considerations are highly varied in the current literature base, including centrifugation, freeze-thaw cycles, and different NMR quantification methods. Our findings suggest that the 1H NMR metabolite profile of saliva is resilient to any change resulting from freezing, including freezing of saliva prior to centrifuging. However, centrifugation was necessary to remove an unidentified broad peak between 1.24 and 1.3 ppm, the intensity of which correlated strongly with saliva cellular content. This peak obscured the methyl peak from lactate and significantly affected quantification. Metabolite quantification was similar for saliva centrifuged between 750 g to 15 000 g. Quantification of salivary metabolites was similar whether quantified using internal phosphate-buffered sodium trimethylsilyl-[2,2,3,3-2H4]-propionate (TSP) or external TSP in a coaxial NMR tube placed inside the NMR tube containing the saliva sample. Our results suggest that the existing literature on salivary 1H NMR will not have been adversely affected by variations of the common protocol; however, use of TSP as an internal standard without a buffered medium appears to affect metabolite quantification, notably for acetate and methanol. We include protocol recommendations to facilitate future NMR-based studies of saliva.
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Affiliation(s)
- Alexander Gardner
- Department of Mucosal and Salivary Biology, Dental Institute, King’s College London, London SE1 9RT, United Kingdom
| | | | - Guy H. Carpenter
- Department of Mucosal and Salivary Biology, Dental Institute, King’s College London, London SE1 9RT, United Kingdom
| | - Po-Wah So
- Department of Neuroimaging, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, Maurice Wohl Clinical Neuroscience Institute, 5, Cutcombe Road, London SE5 9RX, United Kingdom
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Avendaño-Reyes L, Meraz-Murillo FJ, Pérez-Linares C, Figueroa-Saavedra F, Correa A, Álvarez-Valenzuela FD, Guerra-Liera JE, López-Rincón G, Macías-Cruz U. Evaluation of the efficacy of Grofactor, a beta-adrenergic agonist based on zilpaterol hydrochloride, using feedlot finishing bulls. J Anim Sci 2017; 94:2954-61. [PMID: 27482682 DOI: 10.2527/jas.2015-9878] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Beta-adrenergic agonists (β-AA) have been shown to positively impact finishing performance and some carcass traits of feedlot cattle. Our objective was to evaluate the efficacy of a β-AA on the basis of zilpaterol hydrochloride (Grofactor, Laboratorios Virbac México, Guadalajara, Mexico) on growth and DMI, carcass characteristics, and meat quality of finishing bulls. Forty-five bulls (75% 25% ) initially weighing 448.7 ± 2.58 kg were blocked by BW and randomly assigned to 1 of 3 diets, using pens of 3 animals, in a randomized complete block design: 1) daily feeding without β-AA in the basal diet (Control), 2) daily feeding with 0.15 mg/kg BW of Grofactor added to the basal diet (ZHG), or 3) daily feeding with 0.15 mg/kg BW of Zilmax (MSD Salud Animal México, Mexico City, Mexico) added to the basal diet (ZHZ). The duration of the feeding period was 30 d with a subsequent 4-d withdrawal period. Compared with Control bulls, the group fed ZHG had a 12% better ( < 0.025) G:F ratio, and their final BW ( 0.094) and ADG ( 0.084) tended to be enhanced. Feedlot performance of ZHG and ZHZ bulls was similar, although the DMI was ∼4% lower ( 0.05) in ZHG bulls vs. the ZHZ and Control groups. The HCW ( 0.001) and dressing percentage ( 0.015) were higher by 20 kg and 3%, respectively, in ZHG bulls vs. Control bulls. The KPH fat was lower ( 0.007) in bulls fed ZHG than in nonsupplemented bulls, but other carcass characteristics were not different in the ZHG and ZHZ bulls, and noncarcass components were not affected by ZHG or ZHZ supplementation. At 48 h postmortem, ZHG bulls had lower ( 0.007) water holding capacity and trended toward ( 0.06) increased chroma and reduced pH ( 0.09) compared to Control bulls. However, compared to ZHZ bulls, ZHG bulls had higher ( 0.02) chroma and a trend ( 0.08) toward increased hue angle. At 14 d postmortem, meat quality variables did not differ between the 3 groups of bulls. Supplementation of ZH Grofactor improved feedlot performance and some carcass characteristics of finishing bulls without affecting meat quality. The effects of Grofactor on feedlot performance, carcass traits, and meat quality were similar to those of Zilmax.
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Tansel B, Surita SC. Selectivity and limitations of carbon sorption tubes for capturing siloxanes in biogas during field sampling. Waste Manag 2016; 52:122-129. [PMID: 27055363 DOI: 10.1016/j.wasman.2016.03.057] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2015] [Revised: 03/30/2016] [Accepted: 03/30/2016] [Indexed: 06/05/2023]
Abstract
Siloxane levels in biogas can jeopardize the warranties of the engines used at the biogas to energy facilities. The chemical structure of siloxanes consists of silicon and oxygen atoms, alternating in position, with hydrocarbon groups attached to the silicon side chain. Siloxanes can be either in cyclic (D) or linear (L) configuration and referred with a letter corresponding to their structure followed by a number corresponding to the number of silicon atoms present. When siloxanes are burned, the hydrocarbon fraction is lost and silicon is converted to silicates. The purpose of this study was to evaluate the adequacy of activated carbon gas samplers for quantitative analysis of siloxanes in biogas samples. Biogas samples were collected from a landfill and an anaerobic digester using multiple carbon sorbent tubes assembled in series. One set of samples was collected for 30min (sampling 6-L gas), and the second set was collected for 60min (sampling 12-L gas). Carbon particles were thermally desorbed and analyzed by Gas Chromatography Mass Spectrometry (GC/MS). The results showed that biogas sampling using a single tube would not adequately capture octamethyltrisiloxane (L3), hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6). Even with 4 tubes were used in series, D5 was not captured effectively. The single sorbent tube sampling method was adequate only for capturing trimethylsilanol (TMS) and hexamethyldisiloxane (L2). Affinity of siloxanes for activated carbon decreased with increasing molecular weight. Using multiple carbon sorbent tubes in series can be an appropriate method for developing a standard procedure for determining siloxane levels for low molecular weight siloxanes (up to D3). Appropriate quality assurance and quality control procedures should be developed for adequately quantifying the levels of the higher molecular weight siloxanes in biogas with sorbent tubes.
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Affiliation(s)
- Berrin Tansel
- Department of Civil and Environmental Engineering, Florida International University, College of Engineering and Computing, 10155 West Flagler St, Miami, FL 33174, United States.
| | - Sharon C Surita
- Department of Civil and Environmental Engineering, Florida International University, College of Engineering and Computing, 10155 West Flagler St, Miami, FL 33174, United States
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World Health Organization. Evaluation of certain veterinary drug residues in food. Eighty-first report of the Joint FAO/WHO Expert Committee on Food Additives. World Health Organ Tech Rep Ser 2016;:1-110. [PMID: 27509597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This report represents the conclusions of a Joint FAO/WHO Expert Committee convened to evaluate the safety of residues of certain veterinary drugs in food and to recommend maximum levels for such residues in food. The first part of the report considers general principles regarding the evaluation of residues of veterinary drugs within the terms of reference of the Joint FAO/WHO Expert Committee on Food Additives (JECFA), including MRLs for generic fish species, acute reference doses (ARfDs) for veterinary drugs, an approach for dietary exposure assessment of compounds used for multiple purposes (i.e veterinary drugs and pesticides), dietary exposure assessment for less-than-lifetime exposure, and the assessment of short-term (90-day and 12-month) studies in dogs. Summaries follow of the Committee's evaluations of toxicological and residue data on a variety of veterinary drugs: two insecticides (diflubenzuron and teflubenzuron), an antiparasitic agent (ivermectin), an ectoparasiticide (sisapronil) and a β2-adrenoceptor agonist (zilpaterol hydrochloride). In addition, the Committee considered issues raised in concern forms from the Codex Committee on Residues of Veterinary Drugs in Foods on lasalocid sodium, an antiparasitic agent. Annexed to the report is a summary of the Committee's recommendations on these drugs, including acceptable daily intakes (ADIs), ARfDs and proposed MRLs.
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Sterrett JD, Marks M, Dunlap J, Swann J, Schrock K. The effects of scanning electron microscopy desiccation preparation on demineralized dentin surfaces. INT J PERIODONT REST 2015; 35:403-8. [PMID: 25909528 DOI: 10.11607/prd.2053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
This study assessed the effect various scanning electron microscopy (SEM) desiccation preparation techniques have on a tufted collagen surface produced using an acid-burnished (rubbed) demineralization application technique. Citric acid- soaked cotton pellets (30%) were burnished on the dentin treatment region, rinsed in water, and then fixed. Four SEM desiccation preparation techniques were employed: (1) air-dried from glutaraldehyde; (2) air-dried from ethanol; (3) critical point dried from liquid carbon dioxide (control); or (4) air-dried from tetramethylsilane. Control specimens all displayed a characteristic tufted fibril surface. In all experimental groups, fibrils collapsed, forming an intact, undulating nondescript surface monolayer. All air-drying SEM desiccation preparation procedures appear to cause artifactual distortion of a tufted dentin collagen surface.
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Jeilani YA, Li H, Harruna II, Alhooshani KR, Al-Saadi AA. Collision induced dissociations of non-derivatized and trimethylsilyl-derivatized estradiols: similarities in fragmentation patterns. J Mass Spectrom 2015; 50:308-315. [PMID: 25800012 DOI: 10.1002/jms.3529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2014] [Revised: 10/07/2014] [Accepted: 10/14/2014] [Indexed: 06/04/2023]
Abstract
Fragmentation mechanisms of estradiol and trimethylsilyl (TMS)-derivatized estradiol were studied by triple quadrupole tandem mass spectrometry (MSMS) and density functional theory (DFT) at B3LYP/6-311G(d,p) level. Collision induced dissociations (CID) of estradiol give product ions that are associated with the cleavage of B, C and D rings. Characteristic fragments from the cleavage of the aromatic ring A were not identified, and this was confirmed with both labeled estradiol and trimethylsilyl (TMS)-derivatized estradiol. The mechanisms are based on charge-site directed, radical-directed and charge remote fragmentations that are consistent with previous studies of steroids. CID spectra show ion pairs at m/z: 145/146, 157/158, 185/186, 211/213 and 225/226 with significant intensities, suggesting that these pairs are not from isotopic contributions. The mechanisms show similarities with some minor differences in the fragmentation patterns between the non-derivatized and the TMS-derivatized estradiol.
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Affiliation(s)
- Yassin A Jeilani
- Department of Chemistry and Biochemistry, Spelman College, 350 Spelman Lane, Box 1134, Atlanta, GA, 30314, USA
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14
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Rubino M, Milin S, D'Onofrio A, Signoret P, Hatté C, Balesdent J. Measurement of δ13C values of soil amino acids by GC-C-IRMS using trimethylsilylation: a critical assessment. Isotopes Environ Health Stud 2014; 50:516-530. [PMID: 25331967 DOI: 10.1080/10256016.2014.959444] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In this study, we evaluated trimethylsilyl (TMS) derivatives as derivatization reagents for the compound-specific stable carbon isotope analysis of soil amino acids by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). We used non-proteinogenic amino acids to show that the extraction-derivatization-analysis procedure provides a reliable method to measure δ(13)C values of amino acids extracted from soil. However, we found a number of drawbacks that significantly increase the final total uncertainty. These include the following: production of multiple peaks for each amino acid, identified as di-, tri- and tetra-TMS derivatives; a number of TMS-carbon (TMS-C) atoms added lower than the stoichiometric one, possibly due to incomplete combustion; different TMS-C δ(13)C for di-, tri- and tetra-TMS derivatives. For soil samples, only four amino acids (leucine, valine, threonine and serine) provide reliable δ(13)C values with a total average uncertainty of 1.3 ‰. We conclude that trimethylsilyl derivatives are only suitable for determining the (13)C incorporation in amino acids within experiments using (13)C-labelled tracers but cannot be applied for amino acids with natural carbon isotope abundance until the drawbacks described here are overcome and the measured total uncertainty significantly decreased.
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Affiliation(s)
- Mauro Rubino
- a Dipartimento di Matematica e Fisica , Seconda Università di Napoli , Caserta , Italy
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15
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Sánchez-Brunete C, Miguel E, Albero B, Tadeo JL. Analysis of salicylate and benzophenone-type UV filters in soils and sediments by simultaneous extraction cleanup and gas chromatography-mass spectrometry. J Chromatogr A 2011; 1218:4291-8. [PMID: 21636087 DOI: 10.1016/j.chroma.2011.05.030] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Revised: 05/06/2011] [Accepted: 05/09/2011] [Indexed: 11/18/2022]
Abstract
An analytical method for the determination of UV filters in soil and sediment has been developed and validated considering benzophenones (BP) and salicylates as target analytes. Soil and sediment samples were extracted with ethyl acetate-methanol (90:10, v/v) assisted with sonication, performing a simultaneous clean-up step. Quantification of these compounds was carried out by gas chromatography-mass spectrometry (GC-MS) after derivatization of the extracts with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA). Recoveries from spiked soil samples ranged from 89.8% to 104.4% and they were between 88.4% and 105.3% for spiked sediment samples. The effect of the residence time and soil moisture content on the recovery of these compounds was also studied. The precision, expressed as relative standard deviation, was in all cases below 6.1% and the limits of detection (S/N=3) varied from 0.07 to 0.10 ng g(-1) and from 0.11 to 0.28 ng g(-1) for soils and sediments, respectively. The validated method was applied to the analysis of five benzophenone and two salicylate UV filters in soil and sediment samples collected in different areas of Spain.
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16
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Persson M, Albet-Torres N, Ionov L, Sundberg M, Höök F, Diez S, Månsson A, Balaz M. Heavy meromyosin molecules extending more than 50 nm above adsorbing electronegative surfaces. Langmuir 2010; 26:9927-9936. [PMID: 20337414 DOI: 10.1021/la100395a] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
In the in vitro motility assay, actin filaments are propelled by surface-adsorbed myosin motors, or rather, myosin motor fragments such as heavy meromyosin (HMM). Recently, efforts have been made to develop actomyosin powered nanodevices on the basis of this assay but such developments are hampered by limited understanding of the HMM adsorption geometry. Therefore, we here investigate the HMM adsorption geometries on trimethylchlorosilane- [TMCS-] derivatized hydrophobic surfaces and on hydrophilic negatively charged surfaces (SiO(2)). The TMCS surface is of great relevance in fundamental studies of actomyosin and both surface substrates are important for the development of motor powered nanodevices. Whereas both the TMCS and SiO(2) surfaces were nearly saturated with HMM (incubation at 120 microg mL(-1)) there was little actin binding on SiO(2) in the absence of ATP and no filament sliding in the presence of ATP. This contrasts with excellent actin-binding and motility on TMCS. Quartz crystal microbalance with dissipation (QCM-D) studies demonstrate a HMM layer with substantial protein mass up to 40 nm above the TMCS surface, considerably more than observed for myosin subfragment 1 (S1; 6 nm). Together with the excellent actin transportation on TMCS, this strongly suggests that HMM adsorbs to TMCS mainly via its most C-terminal tail part. Consistent with this idea, fluorescence interference contrast (FLIC) microscopy showed that actin filaments are held by HMM 38 +/- 2 nm above the TMCS-surface with the catalytic site, on average, 20-30 nm above the surface. Viewed in a context with FLIC, QCM-D and TIRF results, the lack of actin motility and the limited actin binding on SiO(2) shows that HMM adsorbs largely via the actin-binding region on this surface with the C-terminal coiled-coil tails extending >50 nm into solution. The results and new insights from this study are of value, not only for the development of motor powered nanodevices but also for the interpretation of fundamental biophysical studies of actomyosin function and for the understanding of surface-protein interactions in general.
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Affiliation(s)
- Malin Persson
- School of Natural Sciences, The Linnaeus University SE-391 82 Kalmar, Sweden
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Sha Y, Deng C, Zhang H, Xie W, Liu B. Microwave-assisted silylation followed by gas chromatography/mass spectrometry for rapid determination of ergosterol in cigarettes. J Sep Sci 2008; 31:2451-6. [PMID: 18604841 DOI: 10.1002/jssc.200800108] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Ergosterol is one of the important precursors of tumorigenic polynuclear aromatic hydrocarbons. To the best of our knowledge, a large amount of ergosterol is present in moldy cigarettes, which derives from fungal contaminations. Thus, the development of a simple, fast, and efficient method for the analysis of ergosterol is in great demand. In this paper, GC/MS following microwave-assisted silylation (MAS) was developed for the rapid quantitative analysis of ergosterol in cigarettes for the first time. In our work, total ergosterol in cigarettes after NaOH saponification was extracted with hexane, and then was fast derivatized with bis(trimethylsilyl)trifluoroacetamide (BSTFA) under microwave irradiation. Finally, the ergosterol trimethylsilyl derivative was analyzed by GC/MS. Derivatization conditions including microwave reaction solvent, irradiation time, and power were investigated. Method validations (linear range, LOD, precision, and recovery) were also studied. The results showed that the proposed method provided a fast, simple, and sensitive approach for the determination of ergosterol in cigarettes. Finally it was successfully applied to the analysis of ergosterol in normal and mildewy cigarettes.
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Affiliation(s)
- Yunfei Sha
- Shanghai Tobacco (Group) Corporation Technical Center, Shanghai, China
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Albet-Torres N, O'Mahony J, Charlton C, Balaz M, Lisboa P, Aastrup T, Månsson A, Nicholls IA. Mode of heavy meromyosin adsorption and motor function correlated with surface hydrophobicity and charge. Langmuir 2007; 23:11147-56. [PMID: 17696458 DOI: 10.1021/la7008682] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The in vitro motility assay is valuable for fundamental studies of actomyosin function and has recently been combined with nanostructuring techniques for the development of nanotechnological applications. However, the limited understanding of the interaction mechanisms between myosin motor fragments (heavy meromyosin, HMM) and artificial surfaces hampers the development as well as the interpretation of fundamental studies. Here we elucidate the HMM-surface interaction mechanisms for a range of negatively charged surfaces (silanized glass and SiO2), which is relevant both to nanotechnology and fundamental studies. The results show that the HMM-propelled actin filament sliding speed (after a single injection of HMM, 120 microg/mL) increased with the contact angle of the surfaces (in the range of 20-80 degrees). However, quartz crystal microbalance (QCM) studies suggested a reduction in the adsorption of HMM (with coupled water) under these conditions. This result and actin filament binding data, together with previous measurements of the HMM density (Sundberg, M.; Balaz, M.; Bunk, R.; Rosengren-Holmberg, J. P.; Montelius, L.; Nicholls, I. A.; Omling, P.; Tågerud, S.; Månsson, A. Langmuir 2006, 22, 7302-7312. Balaz, M.; Sundberg, M.; Persson, M.; Kvassman, J.; Månsson, A. Biochemistry 2007, 46, 7233-7251), are consistent with (1) an HMM monolayer and (2) different HMM configurations at different contact angles of the surface. More specifically, the QCM and in vitro motility assay data are consistent with a model where the molecules are adsorbed either via their flexible C-terminal tail part (HMMC) or via their positively charged N-terminal motor domain (HMMN) without other surface contact points. Measurements of zeta potentials suggest that an increased contact angle is correlated with a reduced negative charge of the surfaces. As a consequence, the HMMC configuration would be the dominant configuration at high contact angles but would be supplemented with electrostatically adsorbed HMM molecules (HMMN configuration) at low contact angles. This would explain the higher initial HMM adsorption (from probability arguments) under the latter conditions. Furthermore, because the HMMN mode would have no actin binding it would also account for the lower sliding velocity at low contact angles. The results are compared to previous studies of the microtubule-kinesin system and are also discussed in relation to fundamental studies of actomyosin and nanotechnological developments and applications.
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Affiliation(s)
- Nuria Albet-Torres
- Department of Chemistry and Biomedical Sciences, University of Kalmar, SE-391 82 Kalmar, Sweden
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19
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Eick JD, Kotha SP, Chappelow CC, Kilway KV, Giese GJ, Glaros AG, Pinzino CS. Properties of silorane-based dental resins and composites containing a stress-reducing monomer. Dent Mater 2007; 23:1011-7. [PMID: 17097138 DOI: 10.1016/j.dental.2006.09.002] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2006] [Revised: 08/31/2006] [Accepted: 09/13/2006] [Indexed: 01/04/2023]
Abstract
OBJECTIVE To evaluate properties of silorane-based resins and composites containing a stress reducing monomer. METHODS Resin mixtures and composites were formulated containing (a) a developmental stress reducing monomer [TOSU; Midwest Research Institute]; (b) Sil-Mix (3M-ESPE); (c) photo cationic initiator system. Standard BISGMA/TEGDMA resin (B/T) and composite (Filtek Z250) were used as controls. Polymerization volume change was measured using a NIST mercury dilatometer and polymerization stress using an Enduratec mechanical testing machine. Three point bend tests determined flexural elastic modulus, work of fracture, and ultimate strength (ADA 27; ISO 4049). Fracture toughness was measured using ASTM E399-90. Four groups of resins and composites were tested: Sil-Mix, methacrylate standard, and Sil-Mix with two addition levels of TOSU. An ANOVA was used and significant differences ranked using Student-Newman-Keuls test (alpha=0.05). RESULTS Polymerization stress values for resins containing TOSU were significantly less than the other materials. Polymerization shrinkage values for Sil-Mix formulations were significantly less than for B/T, but were not different from each other. TOSU-containing formulations generally had somewhat lower mechanical properties values than Sil-Mix or B/T. Polymerization stress values for Sil-Mix-based composites were significantly less as compared to Z250. The 1wt.% TOSU composite had the lowest stress. No difference between composite groups was noted for fracture toughness or work of fracture. For ultimate strength, the 5wt.% TOSU formulation differed significantly from Z250. All Sil-Mix formulations had elastic modulus values significantly different from Z250. SIGNIFICANCE The ability of TOSU to reduce polymerization stress without a proportional reduction in mechanical properties provides a basis for improvement of silorane-based composites.
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Affiliation(s)
- J David Eick
- Department of Oral Biology, University of Missouri-Kansas City, Kansas City, MO, USA.
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20
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Abstract
A silyl-modified variant of the Bellus-Claisen rearrangement is described; the generality of this rearrangement has been demonstrated with a range of allylic amines and ketenes.
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Affiliation(s)
- Donald Craig
- Department of Chemistry, Imperial College London, South Kensington Campus, London, UKSW7 2AZ.
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21
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Ranz A, Lankmayr E. Screening and optimization of the derivatization of polar herbicides with trimethylanilinium hydroxide for GC-MS analysis. ACTA ACUST UNITED AC 2006; 69:3-14. [PMID: 16563514 DOI: 10.1016/j.jbbm.2006.02.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2005] [Revised: 01/19/2006] [Accepted: 02/09/2006] [Indexed: 10/24/2022]
Abstract
In the present study, a derivatization method for the determination of acidic herbicides has been investigated. This procedure involves the methylation with the quaternary ammonium salt trimethylanilinium hydroxide (TMAH) directly in the gas chromatographic auto-sampler vial for analysis by gas chromatography combined with mass spectrometry. The derivatization reaction has been screened for influential factors and statistically significant parameters. The identified factors, reaction time, temperature and hold-up time were optimized by a complete factorial response surface design and optimal reaction conditions were generated. Finally, the optimized methylation procedure was compared to different alkylation methods and obtained results demonstrated the applicability of derivatization with trimethylanilinium hydroxide. Acidic herbicides used in the study consist of several families of compounds like derivatives of acetic acid (2,4-D and 2,4,5-T), butanoic acid (MCPB), benzoic acid (chloramben, dicamba), phenol (dinoseb and dinoterb), propanoic acid (mecoprop) and other miscellaneous acids such as pyridinecarboxlyic acid (picloram). A reliably working, rapid method for the preparation of methyl compounds is generated with respect to automation for routine analysis.
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Affiliation(s)
- A Ranz
- Graz University of Technology, Institute of Analytical Chemistry and Radiochemistry, Technikerstr. 4, A-8010 Graz, Austria
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22
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Barboni L, Giarlo G, Ballini R, Fontana G. 14β-Hydroxy-10-deacetylbaccatin III as a convenient, alternative substrate for the improved synthesis of methoxylated second-generation taxanes. Bioorg Med Chem Lett 2006; 16:5389-91. [PMID: 16890428 DOI: 10.1016/j.bmcl.2006.07.067] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2006] [Revised: 07/19/2006] [Accepted: 07/20/2006] [Indexed: 11/25/2022]
Abstract
This article describes a new, convenient, improved synthesis of the 2-debenzoyl-2-m-methoxybenzoyl-7-triethylsilyl-13-oxo-14beta-hydroxybaccatin III 1,14-carbonate, the key intermediate in the synthesis of two new second-generation antitumor taxanes.
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Affiliation(s)
- Luciano Barboni
- Dipartimento di Scienze Chimiche, Università di Camerino, Via S. Agostino 1, 62032 Camerino (MC), Italy.
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Li Y, Wei G, Yu B. Aryl C-glycosylation of phenols with glycosyl trifluoroacetimidates. Carbohydr Res 2006; 341:2717-22. [PMID: 16978594 DOI: 10.1016/j.carres.2006.08.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Revised: 08/21/2006] [Accepted: 08/25/2006] [Indexed: 11/22/2022]
Abstract
Aryl C-glycosylation of a variety of phenols with glycosyl trifluoroacetimidates in the presence of TMSOTf was examined, leading to the corresponding ortho-hydroxyaryl C-glycosides in variable yields.
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Affiliation(s)
- Yuwen Li
- State Key Laboratory of Bio-organic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
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24
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van Well RM, Kärkkäinen TS, Kartha KPR, Field RA. Contrasting reactivity of thioglucoside and selenoglucoside donors towards promoters: implications for glycosylation stereocontrol. Carbohydr Res 2006; 341:1391-7. [PMID: 16697999 DOI: 10.1016/j.carres.2006.04.029] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2006] [Revised: 04/12/2006] [Accepted: 04/14/2006] [Indexed: 11/15/2022]
Abstract
The stereochemical outcome of glycosylation reactions with model thioglycosides and selenoglycosides proved to be dependent on the source of promoter iodonium ion, with iodine giving different results to N-iodosuccinimide (NIS) alone or N-iodosuccinimide/trimethylsilyltrifluoromethanesulfonate (NIS/TMSOTf). In contrast to armed thioglycosides, which anomerise, and disarmed thioglycosides, which do not react, both armed and disarmed selenoglycosides give rise to the corresponding glycosyl iodides when reacted with iodine. Further, whilst the single electron transfer agent DDQ alone is an ineffective promoter, in combination with iodine it produces better acetonitrile-assisted beta-stereoselectivity with both thioglycosides and selenoglycosides than does tris(4-bromophenyl)aminium hexachloroantimonate (BAHA).
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Affiliation(s)
- Renate M van Well
- Centre for Carbohydrate Chemistry, School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich NR4 7TJ, UK
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25
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Jaoui M, Kleindienst TE, Lewandowski M, Edney EO. Identification and quantification of aerosol polar oxygenated compounds bearing carboxylic or hydroxyl groups. 1. Method development. Anal Chem 2006; 76:4765-78. [PMID: 15307788 DOI: 10.1021/ac049919h] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this study, a new analytical technique was developed for the identification and quantification of multifunctional compounds containing simultaneously at least one hydroxyl or one carboxylic group, or both. This technique is based on derivatizing first the carboxylic group(s) of the multifunctional compound using an alcohol (e.g., methanol, 1-butanol) in the presence of a relatively strong Lewis acid (BF3) as a catalyst. This esterification reaction quickly and quantitatively converts carboxylic acids to their ester forms. The second step is based on silylation of the ester compounds using bis(trimethylsilyl) trifluoroacetamide (BSTFA) as the derivatizing agent. For compounds bearing ketone groups in addition to carboxylic and hydroxyl groups, a third step was used based on PFBHA derivatization of the carbonyls. Different parameters including temperature, reaction time, and effect due to artifacts were optimized. A GC/MS in EI and in methane-CI mode was used for the analysis of these compounds. The new approach was tested on a number of multifunctional compounds. The interpretation of their EI (70 eV) and CI mass spectra shows that critical information is gained leading to unambiguous identification of unknown compounds. For example, when derivatized only with BF(3)-methanol, their mass spectra comprise primary ions at m/z M.+ + 1, M.+ + 29, and M.+ - 31 for compounds bearing only carboxylic groups and M.+ + 1, M.+ + 29, M.+ - 31, and M+. - 17 for those bearing hydroxyl and carboxylic groups. However, when a second derivatization (BSTFA) was used, compounds bearing hydroxyl and carboxylic groups simultaneously show, in addition to the ions observed before, ions at m/z M.+ + 73, M.+ - 15, M.+ - 59, M.+ - 75, M.+ - 89, and 73. To the best of our knowledge, this technique describes systematically for the first time a method for identifying multifunctional oxygenated compounds containing simultaneously one or more hydroxyl and carboxylic acid groups.
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Affiliation(s)
- M Jaoui
- ManTech Environmental Technology, Inc., P.O. Box 12313, Research Triangle Park, North Carolina 27709, USA.
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Abstract
Like other colloidal particles bacteria have a surface charge that originates from the ionization of surface molecules and of the adsorption of ions from solution. Bacterial cell wall and membranes containing numerous proteins, lipid molecules, teichoic acids, lipopolisaccharides which give them characteristic charge. Therefore, bacterial cells undergo electrophoresis in a free solution with their own mobility depending on ionic strength and pH of buffer solution. Various electromigration techniques can be used to separate and determine the intact cells. Successful separation of five species of bacteria was obtained using a trimethylchlorosilane-modified capillary and a divinylbenzene-modified with suppressed EOF over a short distance (8.5 cm). The utilization of coated capillaries prevents adsorption of bacteria to the capillary wall. Another approach is utilization of a dilute dissolved polymer, polyethylene oxide (PEO) in the running buffer as a non-bonded coating for the purpose of altering the EOE These experiment have proved the possibility of diagnosing a variety of diseases and the ability to separate and identify viable cells.
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Affiliation(s)
- Michał Szumski
- Department of Environmental Chemistry and Ecoanalytics, Faculty of Chemistry, Nicolas Copernicus University, ul. Gagarina 7, 87-100 Toruń, Poland
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Komeyama K, Kawabata T, Takehira K, Takaki K. Rare-Earth Silylamide-Catalyzed Selective Dimerization of Terminal Alkynes and Subsequent Hydrophosphination in One Pot. J Org Chem 2005; 70:7260-6. [PMID: 16122246 DOI: 10.1021/jo0509206] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[reaction: see text] Rare-earth silylamides, Ln[N(SiMe3)2]3 (Ln = Y, La, Sm), catalyzed regio- and stereoselective dimerization of terminal alkynes in the presence of amine additives to give conjugated enynes in high yields. The additives played a crucial role to depress the oligomerization and to control the regio- and stereochemistry of the dimerization. Thus, the selectivity for (Z)-head-to-head enynes was increased in the order of tertiary < secondary < primary amine additives. On the other hand, the reversed order was observed for the formation of head-to-tail dimers. When alpha,omega-diynes were subjected to the dimerization, very novel cyclic bisenyne compounds were given through double-dimerization in satisfactory yields. In addition, an application of the system allowed subsequent hydrophosphination of the enynes generated in situ with diphenylphosphine, giving rise to 1-phosphinyl-1,3-dienes as the sole products in excellent yields after oxidative workup.
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Affiliation(s)
- Kimihiro Komeyama
- Department of Chemistry and Chemical Engineering, Graduate School of Engineering, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8527, Japan.
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Abstract
[reaction: see text] (+)-Zoapatanol was synthesized by using four key-steps: a Suzuki cross-coupling to prepare a (Z)-alpha,beta-unsaturated ester followed by an enantioselective dihydroxylation to control the C2' and C3' stereocenters, an intramolecular Horner-Wadsworth-Emmons olefination to construct the oxepane ring, and a chemoselective nucleophilic addition/Birch reduction process of a Weinreb amide to introduce simultaneously the beta,gamma-unsaturated ketone on the side-chain and regenerate alcohols from benzyl ethers.
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Affiliation(s)
- Catherine Taillier
- Laboratoire de Chimie Organique, associé au CNRS, 10 rue Vauquelin, 75231 Paris Cedex 05, France
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Zhang L, Liu Y, Xie MX, Qiu YM. Simultaneous determination of thyreostatic residues in animal tissues by matrix solid-phase dispersion and gas chromatography–mass spectrometry. J Chromatogr A 2005; 1074:1-7. [PMID: 15941032 DOI: 10.1016/j.chroma.2005.03.086] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
A method for determination of thyreostatic residues in animal tissues by matrix solid-phase dispersion (MSPD) and gas chromatography-mass spectrometry in selected ion detection mode was developed. Thyreostatic compounds in different matrices were extracted and purified by combination of MSPD and subsequent solid-phase extraction. Silica gel was selected as the solid support of both procedures and the conditions of the procedures were optimized. Thyreostats were derivatized with pentafluorobenzylbromide (PFBBr) in strong basic medium and then with N-methyl-N-(trimethylsilyl)-trifluoroacetamide (MSTFA), which can improve the yields of derivatization for thyreostats, the repeatability, and therefore the limits of detection (LOD) of thyreostats. The limits of detection reached 10 microg/kg (2-thiouracil, 6-methyl-2-thiouracil and 6-propyl-2-thiouracil), 20 microg/kg (6-phenyl-2-thiouracil) and 50 microg/kg (tapazole) with high recoveries (more than 70% for most of thyreostats) and relative standard deviations between 4.5% and 8.7%.
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Affiliation(s)
- Lei Zhang
- Analytical & Testing Center of Beijing Normal University, Xinjiekowaidajie 19, Beijing 100875, China
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31
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Domeño C, Ruiz B, Nerín C. Determination of sterols in biological samples by SPME with on-fiber derivatization and GC/FID. Anal Bioanal Chem 2005; 381:1576-83. [PMID: 15827725 DOI: 10.1007/s00216-005-3056-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2004] [Revised: 12/13/2004] [Accepted: 01/03/2005] [Indexed: 10/25/2022]
Abstract
A new procedure for the determination of sterols in serum samples is proposed. The system consists of coating a Solid Phase Microextraction (SPME) microfiber in headspace mode with the derivatizing agent N,O-bis(trimethylsilyl)trifluoracetamide (BSTFA) and then applying this coated fiber to the simultaneous extraction and derivatization of three precursors in the cholesterol biosynthesis pathway (desmosterol, lathosterol and lanosterol) and two phytosterols (sitosterol and sitostanol) in serum samples. Optimization of the analytical procedure via the application of an experimental design, a study of matrix effects, and an analysis of serum pool samples are all described and discussed.
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Affiliation(s)
- Celia Domeño
- Department of Analytical Chemistry, Centro Politécnico Superior (CPS), University of Zaragoza, María de Luna 3, 50018 Zaragoza, Spain
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Berns A, Vinken R, Bertmer M, Breitschwerdt A, Schäffer A. Use of 15N-depleted artificial compost in bound residue studies. Chemosphere 2005; 59:649-658. [PMID: 15792662 DOI: 10.1016/j.chemosphere.2004.10.027] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2004] [Revised: 10/14/2004] [Accepted: 10/19/2004] [Indexed: 05/24/2023]
Abstract
Association of bound residues to soil humic matter may be accomplished by different binding mechanisms such as sequestration in hydrophobic interiors of the organic material or covalent linkage to the organic matter. The structures and chemical environments of compounds can be observed by NMR spectroscopy. We applied 15N-NMR spectroscopy to study the soil-bound residues of 15N-labeled simazine. As the 15N-isotope has a low sensitivity and natural abundance 15N-NMR experiments require long measurement times and often result in low signal-to-noise (S/N) ratios. Therefore, in addition to the use of 15N-labeled simazine, 15N-depleted compost was used to reduce the amount of background signal and enhance the sensitivity. The compost was produced from maize and wheat plants grown on sand with 15N-depleted NH4NO3 as sole nitrogen source. The plants were freeze-dried, ground and mixed with sand for composting. After a composting period of 224 days analysis of the compost revealed a 15N-content of 267 ppm as opposed to a natural abundance of 3650 ppm. Characterization of this artificial compost produced parameter values similar to those of a natural compost. The 13C-NMR-spectra of the humic and fulvic acids during different stages of maturity showed that there was a shift from single-bond functional groups to more complex double-bond and aromatic structures. Experiments with this compost showed an increased signal intensity. The improved sensitivity made it possible to obtain interpretable NMR signals in contrast to experiments with 15N-simazine on native soil where no signals were detectable. The data indicated that the bound residues of simazine are composed of metabolites resulting from N-dealkylation and triazine ring destruction. Silylation of the bound residues showed a very strong binding of the residues to the matrix as only a small fraction could be solubilized.
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Affiliation(s)
- Anne Berns
- Forschungszentrum Juelich GmbH, Institute of Chemistry and Dynamics of the Geosphere, Institute IV: Agrosphere, 52425, Juelich, Germany.
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Ubero-Pascal N, Fortuño JM, de Los Angeles Puig M. New application of air-drying techniques for studying Ephemeroptera and Plecoptera eggs by scanning electron microscopy. Microsc Res Tech 2005; 68:264-71. [PMID: 16315231 DOI: 10.1002/jemt.20248] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Hexamethyldisilizane (HMDS) and tetramethylsilane are organic compounds that are volatile at ambient temperature and which can therefore be used for air-drying biological samples for SEM studies. The techniques using these compounds provide results that are comparable with those obtained by critical point drying, but which involve a very simple process that saves time and money. Both techniques were applied to SEM studies of Ephemeroptera and Plecoptera eggs in order to assess their suitability as alternative methods to critical point drying for these kinds of biological material. The results show no morphological differences between eggs HMDS air-dried and critical point-dried.
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Affiliation(s)
- Nicolás Ubero-Pascal
- Departamento de Zoología y Antropología Física, Facultad de Biología, Universidad de Murcia, Campus de Espinardo s/n, 30100 Espinardo-Murcia, Spain.
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Abstract
[reaction: see text] Glucosyl-, galactosyl-, and mannosyl iodides efficiently react with strained oxacycloalkane acceptors to afford O-glycosides with high beta-selectivity. The mechanism of ring opening was investigated by reacting mannosyl iodides with pure enantiomers of propylene oxide and styrene oxide. Competition experiments between three- and five-membered oxacycloalkanes were also investigated. Finally, beta-thiomannosides were synthesized from thiocycloalkane acceptors.
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Affiliation(s)
- Darrin R Dabideen
- Department of Chemistry, University of California Davis, Davis, California 95616, USA
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Sundberg M, Rosengren JP, Bunk R, Lindahl J, Nicholls IA, Tågerud S, Omling P, Montelius L, Månsson A. Silanized surfaces for in vitro studies of actomyosin function and nanotechnology applications. Anal Biochem 2004; 323:127-38. [PMID: 14622967 DOI: 10.1016/j.ab.2003.07.022] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We have previously shown that selective heavy meromyosin (HMM) adsorption to predefined regions of nanostructured polymer resist surfaces may be used to produce a nanostructured in vitro motility assay. However, actomyosin function was of lower quality than on conventional nitrocellulose films. We have therefore studied actomyosin function on differently derivatized glass surfaces with the aim to find a substitute for the polymer resists. We have found that surfaces derivatized with trimethylchlorosilane (TMCS) were superior to all other surfaces tested, including nitrocellulose. High-quality actin filament motility was observed up to 6 days after incubation with HMM and the fraction of motile actin filaments and the velocity of smooth sliding were generally higher on TMCS than on nitrocellulose. The actomyosin function on TMCS-derivatized glass and nitrocellulose is considered in relation to roughness and hydrophobicity of these surfaces. The results suggest that TMCS is an ideal substitute for polymer resists in the nanostructured in vitro motility assay. Furthermore, TMCS derivatized glass also seems to offer several advantages over nitrocellulose for HMM adsorption in the ordinary in vitro motility assay.
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Affiliation(s)
- Mark Sundberg
- Department of Chemistry and Biomedical Sciences, University of Kalmar, SE-391 82 Kalmar, Sweden
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Abstract
This paper describes a procedure for the detection and quantification of ethyl-glucuronide (EtG) in hair samples. During method development the efficacy of extraction of EtG from hair was compared in four extraction methods: (a) methanol; (b) methanol:water (1:1); (c) water; and (d) water:trifluoroacetic acid (9:1). In addition, three derivatizing agents were compared as well: N,O-bistrimethylsilyl-trifluoroacetamide (BSTFA): trimethylchlorosilane (TMCS) (99:1), pentafluoropropionic anhydride (PFPA) and heptafluorobutyric anhydride (HFBA). Water was found to be the best extracting solvent and PFPA the best derivatizing agent. Both provided the highest recoveries, with cleaner extracts and more stable derivatives. The final method is as follows: about 100mg of hair are sequentially washed with water and acetone. The decontaminated sample is finely cut with scissors, then the deuterated internal standard (EtG-d5) and 2 mL of water are added. After sonication for 2 h, the sample is maintained at room temperature overnight. Derivatization is performed with PFPA. Derivatives are injected into a GC-MS system in the electronic impact mode. The method shows linearity over the range of concentrations from 0.050 to 5 ng/mg. Detection and quantification limits are 0.025 and 0.050 ng/mg, respectively. Mean recoveries for the three studied concentrations (low, medium and high) are higher than 87%. The coefficients of variation in intra- and inter-assay precision are always lower than 7%. The method is being routinely applied in our lab for the diagnosis of chronic alcohol consumption.
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Affiliation(s)
- C Jurado
- Instituto Nacional de Toxicología, P.O. Box 863, 41080 Sevilla, Spain.
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Abstract
This report describes a concept in which an immunoassay is used indirectly to quantify a nonantigenic very low molecular weight compound participating in a chemical reaction with a haptenic reporter. The detection limit of each reagent is, therefore, governed only by the affinity of the antibodies toward the reporter. Fluoride was used as a model, and silylated estradiol was used as a reporter. Upon silylation with N-O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) or N-O-bis(dimethylterbutylsilyl) trifluoroacetamide (MTBSTFA), estradiol is no longer recognized by antibodies specific to estradiol. After reaction with hydrofluoric acid (HF) or fluoride salts (KF, CsF, NaF), its immunoreactivity is restored, and native estradiol is formed and is detected by immunoassay. The level of synthesized estradiol is dependent on the concentration of fluoride. A fluoride detection limit of 0.3 microg/L (15 nM) is obtained. Potential interference with other acids has been eliminated by choosing the silyl group (trimethylsilyl vs tert-butyldimethylsilyl) and by selecting optimal reaction conditions for the desilylation. The method has been applied to the detection of fluoride salts in natural waters (range 0.28-9.0 mg/L) and in an atmosphere artificially contaminated with HF between 8 and 160 microg/m(3) in the parts-per-billion range. This indirect immunoassay combines simplicity and high sensitivity and, therefore, can be used in field monitoring. Finally, the extension of the concept to other chemicals is discussed.
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Affiliation(s)
- Marie-Astrid Sagot
- CEA, Service de Pharmacologie et d'Immunologie, UMR CNRS6014, 76131 Mont St-Aignan, France
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Abstract
A sensitive method for the quantification of free salbutamol in human urine is described. Sample clean up is performed using SPE on a mixed phase extraction column. Derivatisation is performed with N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA) and the extract is analysed by GC-MS. The method was found to be suitable for use in the doping field, where a cut-off limit of 1 microg salbutamol/mL urine is set by the International Olympic Committee (IOC) and approved by the World Anti-Doping Agency (WADA). Above that value a doping violation occurs. In addition, the stability of salbutamol in human urine has been evaluated.
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Affiliation(s)
- Guro Forsdahl
- Doping Control Laboratory, ARC Seibersdorf research GmbH, A-2224 Seibersdorf, Austria
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Abstract
First measurements with a prototype ionization chamber are described to be applied in online monitoring of modulated fields in radiation therapy. The liquids isooctane, isononane (TMP) and tetramethylsilane (TMS) are used in a high purity grade in order to realize high current signals for electronic read-out in parallel at frequencies exceeding 10 Hz. Signals of more than a factor 4 with respect to isooctane, analysis grade, are obtained. With an electrode structure of 400 pads, a uniformity in efficiency within 1.2% has been measured. The penumbra of a multileaf collimator could be resolved. Theoretical examination verifies that the free electrons in the liquids cause higher signals when the measured currents are compared with expectation for ion transport only.
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Affiliation(s)
- K Eberle
- University of Karlsruhe, Institut für Experimentelle Kernphysik, PO Box 3640, 76021 Karlsruhe, Germany
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40
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Abstract
The chemical shift of TMS is commonly assumed to be zero. However, it varies by over 1 ppm for 1H and 4 ppm for 13C and shows a correlation with the physical properties of the solvent. Using the commonly accepted convention that TMS always resonates at zero leads to significant errors when comparing chemical shifts in different solvents. A new method for measuring absolute chemical shift with a conventional NMR spectrometer is demonstrated. The observed chemical shift is corrected by measuring and correcting for susceptibility and shape factor. Practical suggestions are made for modifying the current chemical shift standard while maintaining compatibility with earlier literature.
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Affiliation(s)
- Roy E Hoffman
- Department of Organic Chemistry, Institute of Chemistry, Safra Campus, The Hebrew University of Jerusalem, Givat Ram, Jerusalem 91904, Israel.
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41
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Kress M, Meissner D, Kaiser P, Hanke R, Wood WG. The measurement of theophylline in human serum or plasma using gas chromatography and isotope dilution-mass spectrometry (GC-IDMS) taking other substituted xanthines into consideration. Clin Lab 2003; 48:535-40. [PMID: 12389715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
Abstract
A method is described which uses a combination of gas chromatography and isotope dilution-mass spectrometry (GC-IDMS) to determine the concentration of theophylline (1,3-dimethyl xanthine) in human plasma or serum samples. The effects of similar substituted xanthines - namely theobromine (3,7-dimethyl xanthine), paraxanthine (1,7-dimethyl xanthine) 1,3-dimethyl-7-(2-hydroxyethyl) xanthine (internal standard HPLC) and caffeine (1,3,7-trimethyl xanthine) were tested to confirm the specificity of the method. The derivatisation of all xanthines was performed with N-methyl-N-trimethylsilyl trifluroacetamide (MSTFA). The internal standard used was 2-(13)C ,1,3-(15)N2-theophylline. The extraction and derivatisation procedures were examined in detail and optimised stepwise during the development of the method. High-performance liquid chromatography (HPLC) was used for comparison.
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Affiliation(s)
- Michael Kress
- Instand Reference Laboratories Instand e.V., Düsseldorf, Germany
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Abstract
The interaction between the peptide hormone motilin and bicelles has been investigated by pulsed field gradient-nuclear magnetic resonance methods and by the use of paramagnetic probes. Diffusion coefficients were measured for motilin, the phospholipids with and without motilin, and for tetramethylsilane. The results show that around 90% of motilin is bound to acidic bicelles and 84% of motilin is bound to neutral bicelles. It is found that the apparent bicelle size is reduced by the presence of motilin. This cannot be explained by changes in 1,2-dihexanoyl-sn-glycero-3-phosphatidylcholine solubility. The use of paramagnetic agents to investigate the position of motilin shows that the turn in the N-terminus of motilin is inserted into the bicelle, while the helix most likely resides within the head-group layer.
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Affiliation(s)
- August Andersson
- Department of Biochemistry and Biophysics, Arrhenius Laboratory, Stockholm University, 10691, Stockholm, Sweden
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Abstract
Tetramethylsilane reacts with 2,2,2-trifluoroethanol (TFE) in the presence of a cationic platinum(II) catalyst [(NN)PtMe(TFE)]+ (NN = 1,2-bis(3,5-dimethylphenylimino)butane). Catalytic Si-C bond heterolysis results in the formation of the trimethylsilyl ether, Me3SiOCH2CF3, accompanied by liberation of one equivalent of methane. Preliminary experiments suggest that a rate-determining C-H bond activation precedes rapid attack by solvent at silicon to yield the silyl ether product and regenerate the active platinum methyl cation.
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Affiliation(s)
- Alan F Heyduk
- Arnold and Mabel Beckman Laboratories of Chemical Synthesis, California Institute of Technology, Pasadena, California 91125
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Flaherty S, Wark S, Street G, Farley JW, Brumley WC. Investigation of capillary electrophoresis-laser induced fluorescence as a tool in the characterization of sewage effluent for fluorescent acids: determination of salicylic acid. Electrophoresis 2002; 23:2327-32. [PMID: 12210239 DOI: 10.1002/1522-2683(200207)23:14<2327::aid-elps2327>3.0.co;2-k] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The investigation of emerging contaminant issues is a proactive effort in environmental analysis. As a part of this effort, sewage effluent is of current analytical interest because of the presence of pharmaceuticals and their metabolites and personal care products. The environmental impact of these components is still under investigation but their constant perfusion into receiving waters and their potential effect on biota is of concern. This paper examines a tool for the characterization of sewage effluent using capillary electrophoresis-laser induced fluorescence (CE-LIF) with a frequency-doubled laser operated in the ultraviolet (UV). Fluorescent acidic analytes are targeted because they present special problems for techniques such as gas chromatography-mass spectrometry (GC-MS) but are readily accessible to CE-LIF. As an example of the application of this tool, salicylic acid is determined near the 100 ng/L (7 x 10(-10) M) level in sewage effluent. Salicylic acid is a metabolite of various analgesics. Relatively stable in the environment, it is a common contaminant of municipal sewage systems. Salicylic acid was recovered from freshly collected samples of the effluent by liquid-liquid extraction. Confirmation of identity was by electron ionization GC-MS after conversion of the salicylic acid to the methyl ester by means of trimethylsilyldiazomethane. CE-LIF in the UV has revealed more than 50 individual peaks in the extract and a background response that suggests a large and indeterminate number of additional compounds are present. These data together with complementary techniques provide information on the complexity and components in these effluent streams.
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Affiliation(s)
- Sean Flaherty
- Department of Physics, University of Nevada-Las Vegas, NV 89154-4002, USA
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Hernández-Pérez JM, Cabré E, Fluvià L, Motos A, Pastor C, Corominas A, Gassull MA. Improved method for gas chromatographic-mass spectrometric analysis of 1-(13)C-labeled long-chain fatty acids in plasma samples. Clin Chem 2002; 48:906-12. [PMID: 12029007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
BACKGROUND Gas chromatographic-mass spectrometric (GC/MS) tracking of stable-isotope-labeled substrates is useful in metabolic studies. However, GC/MS analysis of long-chain fatty acid methyl esters yields results that mostly depend on their concentration in the system. We describe a protocol aimed to obviate this and other drawbacks in plasma [1-(13)C]palmitic and [1-(13)C]oleic acid measurements. METHODS Lipoproteins were separated by sequential ultracentrifugation. Free or esterified heptadecanoic acid was used as internal standard. Fatty acids were derivatized to trimethylsilyl (TMS) esters. GC separation was in isothermal mode at 210 degrees C for 27 min. For both TMS-palmitate and TMS-oleate, M and [M + 1] signals were simultaneously acquired with a dual acquisition program in single-ion monitoring mode. Calibration mixtures containing increasing amounts of labeled fatty acids were prepared gravimetrically to construct calibration curves for isotopic enrichment. Likewise, five calibration curves (for increasing concentrations) were constructed for each fatty acid; this allowed selection of the most appropriate curve for the concentration in a plasma sample. RESULTS Oleic acid-TMS ester was clearly separated from that of its stereoisomer, elaidic acid. Within a 10-fold concentration range, the isotopic ratio was independent on the amount of the analyte in the sample, with a maximum uncertainty of 0.34% in terms of molar percent excess. In addition, the within- and between-day imprecision (CV) of the method was <1%. CONCLUSION Results obtained with this method are independent of concentration and sufficiently precise for tracking 1-(13)C-labeled palmitic and oleic acids in biological samples
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Affiliation(s)
- José M Hernández-Pérez
- Research Unit, Department of Gastroenterology, Hospital Universitari Germans Trias i Pujol, 08916 Badalona, Catalonia, Spain
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Abstract
Time domain multiplexing (TDM) is presented as a viable approach to increasing the sensitivity and efficiency of magnetic resonance spectroscopic (MRS) experiments through multi-channel signal acquisition. By switching very rapidly between coils of a receive phased array, TDM receiver extensions allow the acquisition of multiple, independent spectra through a single channel magnetic resonance console. A TDM receiver extension designed for imaging and spectroscopy is described, and the impact of this hardware extension on the processing and quantitation of MRS data is addressed. The primary complication involves the use of fixed bandwidth RF band-pass filters that can not be adjusted to match the spectral width of the desired MRS experiment.MRS sequences whose bandwidths are narrower than the bandwidth provided by TDM band-pass filters can be acquired through TDM with minimal loss of SNR as long as two constraints are met. The first constraint requires that the entire bandwidth of the band-pass filters be sampled at or more rapidly than the Nyquist rate associated with their bandwidth, to prevent extra noise from aliasing into the final spectrum. The second requirement is that spectral resolution be held constant to that of the desired experiment. Results from a two-channel multiplexed MRS experiment, conducted according to these guidelines, illustrate that TDM can be used to allow acquisition of multi-channel MRS experiments through single channel console systems with a minimal loss in SNR.
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Affiliation(s)
- J A Bankson
- Department of Electrical Engineering, Texas A&M University, College Station, TX, USA.
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47
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Lee S, Jørgensen M, Hartwig JF. Palladium-catalyzed synthesis of arylamines from aryl halides and lithium bis(trimethylsilyl)amide as an ammonia equivalent. Org Lett 2001; 3:2729-32. [PMID: 11506620 DOI: 10.1021/ol016333y] [Citation(s) in RCA: 153] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[reaction: see text]. A simple, palladium-catalyzed method to convert aryl halides to the parent anilines using lithium bis(trimethylsilyl)amide (LiN(SiMe3)2) is reported. The reaction is catalyzed by Pd(dba)2 and P(t-Bu)3 and can be run with as little as 0.2 mol % of catalyst. The reaction is faster than competing generation of benzyne intermediates and, therefore, provides the aniline products regiospecifically.
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Affiliation(s)
- S Lee
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, USA
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Duncan D, Livinghouse T. Intramolecular cyclizations of imines bearing the 2-(thiomethyl)-3-trimethylsilyl-1-propenyl terminator. An efficient new procedure for the stereocontrolled synthesis of functionalized pyrrolidine derivatives. J Org Chem 2001; 66:5237-40. [PMID: 11463278 DOI: 10.1021/jo0015366] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- D Duncan
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, USA
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49
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Affiliation(s)
- S Mei
- College of Chemistry, Wuhan University, Wuhan 430072, China
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50
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Haber E, Muñoz-Guerra JA, Soriano C, Carreras D, Rodriguez C, Rodriguez FA. Automated sample preparation and gas chromatographic-mass spectrometric analysis of urinary androgenic anabolic steroids. J Chromatogr B Biomed Sci Appl 2001; 755:17-26. [PMID: 11393702 DOI: 10.1016/s0378-4347(00)00539-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This paper presents an automated method for extracting anabolic agents from urine samples for their GC-MS analysis by selected-ion monitoring. The sample preparation was carried out in a Hewlett-Packard 7686 SPE PrepStation system. Each 0.6-ml aliquot was hydrolyzed, extracted, dried and trimethylsilyl (TMS) derivatized in a 2-ml vial without any hands-on labor. When sample preparation was finished 2 microl of the extract was injected into the gas chromatograph by split (1:10) mode. Due to the small amount of free space in the 2-ml vials for handling the sample, parameters like time of hydrolysis, type of shaking, number of extractions and some TMS derivatization parameters had to be adjusted to achieve the best recovery for all of the compounds in the screening. Manual and automated sample preparation schemes were compared in terms of linearity, precision, accuracy, limit of detection and recovery data. When large concentrations were analyzed using the automated method no carry-over effect was observed.
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Affiliation(s)
- E Haber
- Doping Control Laboratory, Higher Sports Council, Madrid, Spain
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