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Nicolás Carcelén J, Potes Rodríguez H, González-Gago A, Marchante-Gayón JM, Ballesteros A, González JM, García Alonso JI, Rodríguez-González P. Evaluation of different isotope dilution mass spectrometry strategies for the characterization of naturally abundant and isotopically labelled peptide standards. Anal Bioanal Chem 2024; 416:1717-1731. [PMID: 38363304 PMCID: PMC10899365 DOI: 10.1007/s00216-024-05176-1] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Revised: 01/18/2024] [Accepted: 01/23/2024] [Indexed: 02/17/2024]
Abstract
Natural abundance and isotopically labelled tryptic peptides are routinely employed as standards in quantitative proteomics. The certification of the peptide content is usually carried out by amino acid analysis using isotope dilution mass spectrometry (IDMS) after the acid hydrolysis of the peptide. For the validation and traceability of the amino acid analysis procedure, expensive certified peptides must be employed. In this work we evaluate different IDMS alternatives which will reduce the amount of certified peptide required for validation of the amino acid analysis procedure. In this context, the characterization of both natural and isotopically labelled synthetic angiotensin I peptides was carried out. First, we applied a fast procedure for peptide hydrolysis based on microwave-assisted digestion and employed two certified peptide reference materials SRM 998 angiotensin I and CRM 6901-b C-peptide for validation of the hydrolysis procedure. The amino acids proline, leucine, isoleucine, valine, tyrosine, arginine and phenylalanine were evaluated for their suitability for peptide certification by IDMS by both liquid chromatography with tandem mass spectrometry (LC-MS/MS) and gas chromatography with mass spectrometry (GC)-MS/MS. Then, natural angiotensin I and 13C1-labelled angiotensin I were synthesized in-house and purified by preparative liquid chromatography. The concentration of the 13C1-labelled angiotensin I peptide was established by reverse IDMS in its native form using SRM 998 angiotensin I as reference. The concentration of the natural synthesized peptide was determined by IDMS both using the 13C1-labelled peptide in its native form and by amino acid analysis showing comparable results. Finally, the synthetic naturally abundant angiotensin I peptide was employed as "in-house" standard for the validation of subsequent peptide characterization procedures. Therefore, the novelty of this work relies on, first, the development of a faster hydrolysis procedure assisted by focused microwaves, providing complete hydrolysis in 150 min, and secondly, a validation strategy combining GC-MS and LC-MS/MS that allowed us to certify the purity of an in-house-synthesized peptide standard that can be employed as quality control in further experiments.
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Affiliation(s)
- Jesús Nicolás Carcelén
- Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Oviedo, Spain
| | - Helí Potes Rodríguez
- Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Oviedo, Spain
| | - Adriana González-Gago
- Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Oviedo, Spain
| | | | - Alfredo Ballesteros
- Department of Organic and Inorganic Chemistry, Faculty of Chemistry, University of Oviedo, Oviedo, Spain
| | - José Manuel González
- Department of Organic and Inorganic Chemistry, Faculty of Chemistry, University of Oviedo, Oviedo, Spain
| | - José Ignacio García Alonso
- Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Oviedo, Spain
| | - Pablo Rodríguez-González
- Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Oviedo, Spain
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Carcelén JN, Marchante-Gayón JM, Rodríguez-González P, Ballesteros A, González JM, Cocho de Juan JÁ, García Alonso JI. Determination of 3-monoiodotyrosine and 3,5-diiodotyrosine in newborn urine and dried urine spots by isotope dilution tandem mass spectrometry. Analyst 2022; 147:1329-1340. [DOI: 10.1039/d1an02203b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Development of an analytical method for the determination of MIT and DIT in newborn urine and dried urine spots by Liquid Chromatography Isotope Dilution Tandem Mass Spectrometry capable of correcting analyte interconversion during sample preparation.
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Affiliation(s)
- Jesús Nicolás Carcelén
- Department of Physical and Analytical Chemistry. Faculty of Chemistry. University of Oviedo, 33006 Oviedo, Spain
| | - Juan Manuel Marchante-Gayón
- Department of Physical and Analytical Chemistry. Faculty of Chemistry. University of Oviedo, 33006 Oviedo, Spain
| | - Pablo Rodríguez-González
- Department of Physical and Analytical Chemistry. Faculty of Chemistry. University of Oviedo, 33006 Oviedo, Spain
| | - Alfredo Ballesteros
- Department of Inorganic and Organic Chemistry. Faculty of Chemistry. University of Oviedo, 33006 Oviedo, Spain
| | - José M. González
- Department of Inorganic and Organic Chemistry. Faculty of Chemistry. University of Oviedo, 33006 Oviedo, Spain
| | - José Ángel Cocho de Juan
- Laboratory of Metabolic Disorders, Santiago de Compostela University Hospital, 15706 Santiago, Spain
| | - José Ignacio García Alonso
- Department of Physical and Analytical Chemistry. Faculty of Chemistry. University of Oviedo, 33006 Oviedo, Spain
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Queipo-Abad S, González PR, Martínez-Morillo E, Davis WC, García Alonso JI. Concentration of mercury species in hair, blood and urine of individuals occupationally exposed to gaseous elemental mercury in Asturias (Spain) and its comparison with individuals from a control group formed by close relatives. Sci Total Environ 2019; 672:314-323. [PMID: 30959298 DOI: 10.1016/j.scitotenv.2019.03.367] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [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: 01/31/2019] [Revised: 03/22/2019] [Accepted: 03/23/2019] [Indexed: 06/09/2023]
Abstract
Between November 19th, 2012 and December 3rd, 2012, 50 workers were intoxicated with gaseous Hg in San Juan de Nieva (Asturias, Spain) during the maintenance of a heat exchanger of a zinc manufacturer. We have quantified the concentration of methylmercury (MeHg), ethylmercury (EtHg) and Hg(II) in blood, hair and urine samples of those individuals taken three years after the accident. Blood, hair and urine of their closest relatives were also analyzed to assess whether the mercury burden present in the intoxicated individuals was due to the occupational exposure or to environmental or lifestyle-related factors. The determination of the mercury species in the samples was carried out applying multiple spiking Isotope Dilution GC-ICP-MS. This procedure corrects for possible interconversion reactions between the Hg species during the sample preparation procedure. Linear correlations were observed for both groups when plotting MeHg in blood vs MeHg in hair, and MeHg in hair vs Hg (II) in urine. The concentrations of Hg species in the intoxicated individuals were not significantly different from those obtained in the control group except for MeHg in blood. Significantly higher levels of MeHg in blood were obtained in some of the intoxicated individuals who had not consumed fish or seafood since the accident. A different correlation between MeHg in hair and MeHg in blood was obtained for these individuals compared to the control group who showed a hair-to-blood ratio consistent with the reported value for people exposed to Hg via fish consumption. Our results suggest that ingested MeHg followed the same pathway of deposition in hair in exposed and non-exposed individuals. However, the exposed individuals with high MeHg levels in blood showed a significantly different extent of MeHg deposition in hair compared to the control group.
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Affiliation(s)
- Silvia Queipo-Abad
- Department of Physical and Analytical Chemistry, University of Oviedo, Julián Clavería, 8, 33006 Oviedo, Spain
| | - Pablo Rodríguez González
- Department of Physical and Analytical Chemistry, University of Oviedo, Julián Clavería, 8, 33006 Oviedo, Spain.
| | - Eduardo Martínez-Morillo
- Service of Clinical Biochemistry, Laboratory of Medicine, Central University Hospital of Asturias (HUCA), 33011 Oviedo, Spain
| | - W Clay Davis
- Chemical Sciences Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - José Ignacio García Alonso
- Department of Physical and Analytical Chemistry, University of Oviedo, Julián Clavería, 8, 33006 Oviedo, Spain
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Rodríguez-Menéndez S, Fernández B, González-Iglesias H, García M, Álvarez L, García Alonso JI, Pereiro R. Isotopically Enriched Tracers and Inductively Coupled Plasma Mass Spectrometry Methodologies to Study Zinc Supplementation in Single-Cells of Retinal Pigment Epithelium in Vitro. Anal Chem 2019; 91:4488-4495. [DOI: 10.1021/acs.analchem.8b05256] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Sara Rodríguez-Menéndez
- Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Julián Clavería, 8, 33006, Oviedo, Spain
| | - Beatriz Fernández
- Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Julián Clavería, 8, 33006, Oviedo, Spain
- Instituto Universitario Fernández-Vega (Fundación de Investigación Oftalmológica, Universidad de Oviedo), 33012 Oviedo, Spain
| | - Héctor González-Iglesias
- Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Julián Clavería, 8, 33006, Oviedo, Spain
- Instituto Universitario Fernández-Vega (Fundación de Investigación Oftalmológica, Universidad de Oviedo), 33012 Oviedo, Spain
- Instituto Oftalmológico Fernández-Vega, Avenida Doctores Fernández-Vega, 34, 33012, Oviedo, Spain
| | - Montserrat García
- Instituto Universitario Fernández-Vega (Fundación de Investigación Oftalmológica, Universidad de Oviedo), 33012 Oviedo, Spain
- Instituto Oftalmológico Fernández-Vega, Avenida Doctores Fernández-Vega, 34, 33012, Oviedo, Spain
| | - Lydia Álvarez
- Instituto Universitario Fernández-Vega (Fundación de Investigación Oftalmológica, Universidad de Oviedo), 33012 Oviedo, Spain
| | - José Ignacio García Alonso
- Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Julián Clavería, 8, 33006, Oviedo, Spain
| | - Rosario Pereiro
- Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Julián Clavería, 8, 33006, Oviedo, Spain
- Instituto Universitario Fernández-Vega (Fundación de Investigación Oftalmológica, Universidad de Oviedo), 33012 Oviedo, Spain
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Nicolás Carcelén J, Marchante-Gayón JM, González PR, Valledor L, Cañal MJ, Alonso JIG. A cost-effective approach to produce 15N-labelled amino acids employing Chlamydomonas reinhardtii CC503. Microb Cell Fact 2017; 16:146. [PMID: 28821247 PMCID: PMC5563056 DOI: 10.1186/s12934-017-0759-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 08/10/2017] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND The use of enriched stable isotopes is of outstanding importance in chemical metrology as it allows the application of isotope dilution mass spectrometry (IDMS). Primary methods based on IDMS ensure the quality of the analytical measurements and traceability of the results to the international system of units. However, the synthesis of isotopically labelled molecules from enriched stable isotopes is an expensive and a difficult task. Either chemical and biochemical methods to produce labelled molecules have been proposed, but so far, few cost-effective methods have been described. RESULTS The aim of this study was to use the microalgae Chlamydomonas reinhardtii to produce, at laboratory scale, 15N-labelled amino acids with a high isotopic enrichment. To do that, a culture media containing 15NH4Cl was used. No kinetic isotope effect (KIE) was observed. The labelled proteins biosynthesized by the microorganism were extracted from the biomass and the 15N-labelled amino acids were obtained after a protein hydrolysis with HCl. The use of the wall deficient strain CC503 cw92 mt+ is fit for purpose, as it only assimilates ammonia as nitrogen source, avoiding isotope contamination with nitrogen from the atmosphere or the reagents used in the culture medium, and enhancing the protein extraction efficiency compared to cell-walled wild type Chlamydomonas. The isotopic enrichment of the labelled amino acids was calculated from their isotopic composition measured by gas chromatography mass spectrometry (GC-MS). The average isotopic enrichment for the 16 amino acids characterized was 99.56 ± 0.05% and the concentration of the amino acids in the hydrolysate ranged from 18 to 90 µg/mL. CONCLUSIONS Previously reported biochemical methods to produce isotopically labelled proteins have been applied in the fields of proteomics and fluxomics. For these approaches, low amounts of products are required and the isotopic enrichment of the molecules has never been properly determined. So far, only 13C-labelled fatty acids have been isolated from labelled microalga biomass as valuable industrial products. In this study, we propose Chlamydomonas reinhardtii CC503 as a feasible microorganism and strain to produce labelled biomass from which a standard containing sixteen 15N-labelled amino acids could be obtained.
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Affiliation(s)
- Jesús Nicolás Carcelén
- Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Julián Clavería 8, 33006 Oviedo, Spain
| | - Juan Manuel Marchante-Gayón
- Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Julián Clavería 8, 33006 Oviedo, Spain
| | - Pablo Rodríguez González
- Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Julián Clavería 8, 33006 Oviedo, Spain
| | - Luis Valledor
- Department of Organisms and Systems Biology, University of Oviedo, C/Catedrático Rodrigo Uría s/n, 33071 Oviedo, Spain
| | - María Jesús Cañal
- Department of Organisms and Systems Biology, University of Oviedo, C/Catedrático Rodrigo Uría s/n, 33071 Oviedo, Spain
| | - José Ignacio García Alonso
- Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Julián Clavería 8, 33006 Oviedo, Spain
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Queipo Abad S, Rodríguez-González P, Davis WC, García Alonso JI. Development of a Common Procedure for the Determination of Methylmercury, Ethylmercury, and Inorganic Mercury in Human Whole Blood, Hair, and Urine by Triple Spike Species-Specific Isotope Dilution Mass Spectrometry. Anal Chem 2017; 89:6731-6739. [DOI: 10.1021/acs.analchem.7b00966] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Silvia Queipo Abad
- Department of Physical
and Analytical Chemistry, University of Oviedo, Julián
Clavería, 8, 33006 Oviedo, Spain
| | - Pablo Rodríguez-González
- Department of Physical
and Analytical Chemistry, University of Oviedo, Julián
Clavería, 8, 33006 Oviedo, Spain
| | - W. Clay Davis
- Chemical Sciences
Division, National Institute of Standards and Technology, Charleston, South Carolina 29412, United States
| | - José Ignacio García Alonso
- Department of Physical
and Analytical Chemistry, University of Oviedo, Julián
Clavería, 8, 33006 Oviedo, Spain
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Galilea San Blas O, Moreno Sanz F, Herrero Espílez P, Sainz Menéndez RM, Mayo Barallo JC, Marchante-Gayón JM, García Alonso JI. Evaluation of sulfur isotopic enrichment of urine metabolites for the differentiation of healthy and prostate cancer mice after the administration of 34S labelled yeast. J Trace Elem Med Biol 2017; 39:155-161. [PMID: 27908409 DOI: 10.1016/j.jtemb.2016.09.006] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Revised: 09/14/2016] [Accepted: 09/22/2016] [Indexed: 11/15/2022]
Abstract
Sulfur isotopic enrichment of urine metabolites in healthy and prostate cancer mice using 34S enriched yeast and High Performance Liquid Chromatography coupled to Multicollector Inductively Coupled Plasma Mass Spectrometry (HPLC-MC-ICP-MS) has been evaluated. A 30 weeks experiment (since the eleventh to the fortieth week of life) was carried out collecting the urine of three healthy mice and three transgenic mice with prostate cancer during 24h after a single oral administration of a 34S enriched yeast slurry. The isotopic enrichment of different sulphur metabolites was monitored by coupling a C18 reverse phase HPLC column with a multicollector ICP-MS using a membrane desolvating system. Quantification of sulfur in the chromatographic peaks was carried out by post-column isotope dilution using a 33S enriched spike. Differences between the 34S enrichment in the urine metabolites of healthy and prostate cancer mice were found from the beginning of the disease. Both populations could be differentiated using a principal component analysis (PCA). Finally, 7 unknown mice were correctly classified in each population using a linear discriminant analysis.
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Affiliation(s)
- Oscar Galilea San Blas
- Department of Physical and Analytical Chemistry, University of Oviedo, Julian Clavería 8, 33006 Oviedo, Spain
| | | | | | | | | | - Juan Manuel Marchante-Gayón
- Department of Physical and Analytical Chemistry, University of Oviedo, Julian Clavería 8, 33006 Oviedo, Spain
| | - José Ignacio García Alonso
- Department of Physical and Analytical Chemistry, University of Oviedo, Julian Clavería 8, 33006 Oviedo, Spain.
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Díaz SC, Encinar JR, Sanz-Medel A, Alonso JIG. Towards compound-independent calibration for organic compounds using online isotope dilution mass spectrometry. Anal Bioanal Chem 2012; 402:91-7. [DOI: 10.1007/s00216-011-5464-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Revised: 09/15/2011] [Accepted: 09/29/2011] [Indexed: 10/16/2022]
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González-Antuña A, Lavandera I, Rodríguez-González P, Rodríguez J, García Alonso JI, Gotor V. A straightforward route to obtain 13C1-labeled clenbuterol. Tetrahedron 2011. [DOI: 10.1016/j.tet.2011.05.118] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Lahbib Y, Abidli S, González PR, Alonso JIG, El Menif NT. Monitoring of organotin pollution in Bizerta channel (northern Tunisia): temporal trend from 2002 to 2010. Bull Environ Contam Toxicol 2011; 86:531-534. [PMID: 21437786 DOI: 10.1007/s00128-011-0248-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Accepted: 03/14/2011] [Indexed: 05/30/2023]
Abstract
Imposex and tributyltin (TBT) body burden were quantified in the gastropod Hexaplex trunculus collected from the Bizerta channel between 2002 and 2010. Except for the imposex frequency that remained maximal (100%), all the other imposex indices decreased throughout the study period. Similarly, TBT levels also decreased over time, being the less frequent compound among butyltins, with a proportion of 22.2%, against 42.9% for dibutyltin (DBT) and 34.9% for monobutyltin (MBT). These findings reflect the effectiveness of new generation of TBT-free antifouling paint introduced in the Tunisian market and global ban of TBT on reducing the environmental impact of this biocide.
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Affiliation(s)
- Youssef Lahbib
- Department of Biology, Laboratory of Environment Biomonitoring, Applied and Fundamental Malacology Group (LBE/MAF), Faculty of Sciences of Bizerta, University of Carthage, 7021 Zarzouna, Tunisia.
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Lahbib Y, Abidli S, Rodríguez González P, García Alonso JI, Trigui-El Menif N. Potential of Nassarius nitidus for monitoring organotin pollution in the lagoon of Bizerta (northern Thunisia). J Environ Sci (China) 2011; 23:1551-1557. [PMID: 22432293 DOI: 10.1016/s1001-0742(10)60582-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [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: 05/31/2023]
Abstract
Imposex and butyltin burden were assessed in Nassarius nitidus, Bolinus brandaris and Hexaplex trunculus collected at five stations in the Bizerta lagoon. Biological analysis showed that imposex followed type (a) in N. nitidus (distal evolution), against type (d) in the two muricids (proximal evolution). Imposex indices were higher in sites located nearby sources of tributyltin and N. nitidus was the least affected species of the five sites, followed by B. brandaris and H. trunculus. Butyltin analysis showed lower accumulation in N. nitidus followed by H. trunculus and B. brandaris. This study has allowed the gathering of data on imposex in a snail studied for the first time in Tunisia (N. nitidus). It suggests the possibility of using such snail as a complementary species for organotin monitoring programs in the Mediterranean and further confirmed that H. trunculus is the most suitable species for such investigations.
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Affiliation(s)
- Youssef Lahbib
- Department of Biology, Laboratory of Environment Biomonitoring, Group of Applied and Fundamental Malacology, Faculty of Sciences of Bizerta, University of Carthage, 7021 Tunisia.
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Reyes LH, Encinar JR, Marchante-Gayón JM, Alonso JIG, Sanz-Medel A. Selenium bioaccessibility assessment in selenized yeast after “in vitro” gastrointestinal digestion using two-dimensional chromatography and mass spectrometry. J Chromatogr A 2006; 1110:108-16. [PMID: 16480727 DOI: 10.1016/j.chroma.2006.01.088] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [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: 11/10/2005] [Revised: 12/21/2005] [Accepted: 01/20/2006] [Indexed: 11/18/2022]
Abstract
In order to investigate the potentially bioavailable selenium-containing compounds in the selenized yeast candidate reference material SEAS 6, a two-dimensional (size exclusion-reversed phase) chromatography approach has been worked out. Electrospray tandem mass spectrometry (ESI Q-TOF MS) was then used for off-line identification of low molecular weigh selenocompounds generated during the gastrointestinal digestion. Selenomethionine (SeMet) was the major compound identified in the gastrointestinal extract while SeMet selenoxide was its main degradation product formed after medium and long-term sample storage, respectively. Total Se and SeMet were quantified in both the soluble extracts and the residue. Results showed that 89+/-3% of total Se was extracted after gastrointestinal digestion, but only 34+/-1% was surprisingly quantified as free SeMet. The rest of Se was present as many other low, medium and high molecular weight Se-species, which could be detected and further characterized by using the two-dimensional chromatography approach proposed here. Interestingly, most of Se-species seemed to be Se-peptides unspecifically produced by the gastrointestinal juice. These results show for the first time that while the efficiency of human gastrointestinal digestion to dissolve Se-containing proteins present in yeast may be high, its efficiency to convert them into free SeMet is much lower. Se-species present in the insoluble residue (not assimilated by the organism), accounting for 11+/-1% of the total Se in selenized yeast, were also studied. After treatment with SDS (denaturing agent) only 13+/-2% of this "insoluble" Se was solubilized, indicating that it was mainly non-protein bound and likely associated to other insoluble matrix components.
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Affiliation(s)
- Laura Hinojosa Reyes
- Department of Physical and Analytical Chemistry, University of Oviedo, C/Julián Clavería 8, 33006 Oviedo, Spain
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