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Nuñez Santiago I, Machushynets NV, Mladic M, van Bergeijk DA, Elsayed SS, Hankemeier T, van Wezel GP. nanoRAPIDS as an analytical pipeline for the discovery of novel bioactive metabolites in complex culture extracts at the nanoscale. Commun Chem 2024; 7:71. [PMID: 38561415 PMCID: PMC10984978 DOI: 10.1038/s42004-024-01153-y] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Accepted: 03/15/2024] [Indexed: 04/04/2024] Open
Abstract
Microbial natural products form the basis of most of the antibiotics used in the clinic. The vast majority has not yet been discovered, among others because the hidden chemical space is obscured by previously identified (and typically abundant) antibiotics in culture extracts. Efficient dereplication is therefore key to the discovery of our future medicines. Here we present an analytical platform for the efficient identification and prioritization of low abundance bioactive compounds at nanoliter scale, called nanoRAPIDS. NanoRAPIDS encompasses analytical scale separation and nanofractionation of natural extracts, followed by the bioassay of interest, automated mass spectrometry identification, and Global Natural Products Social molecular networking (GNPS) for dereplication. As little as 10 μL crude extract is fractionated into 384 fractions. First, bioactive congeners of iturins and surfactins were identified in Bacillus, based on their bioactivity. Subsequently, bioactive molecules were identified in an extensive network of angucyclines elicited by catechol in cultures of Streptomyces sp. This allowed the discovery of a highly unusual N-acetylcysteine conjugate of saquayamycin, despite low production levels in an otherwise abundant molecular family. These data underline the utility and broad application of the technology for the prioritization of minor bioactive compounds in complex extracts.
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Affiliation(s)
- Isabel Nuñez Santiago
- Molecular Biotechnology, Institute of Biology, Leiden University, Leiden, The Netherlands
| | | | - Marija Mladic
- Molecular Biotechnology, Institute of Biology, Leiden University, Leiden, The Netherlands
- DSM-Firmenich, Delft, The Netherlands
| | - Doris A van Bergeijk
- Department of Microbiology, KU Leuven, Immunology and Transplantation (Laboratory of Molecular Bacteriology), Leuven, Belgium
- VIB, Center for Microbiology, Leuven, Belgium
| | - Somayah S Elsayed
- Molecular Biotechnology, Institute of Biology, Leiden University, Leiden, The Netherlands
| | - Thomas Hankemeier
- Leiden Academic Centre for Drug Research (LACDR), Leiden University, Leiden, The Netherlands
| | - Gilles P van Wezel
- Molecular Biotechnology, Institute of Biology, Leiden University, Leiden, The Netherlands.
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2
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Zietek BM, Mladic M, Bruyneel B, Niessen WMA, Honing M, Somsen GW, Kool J. Nanofractionation Platform with Parallel Mass Spectrometry for Identification of CYP1A2 Inhibitors in Metabolic Mixtures. SLAS Discov 2017; 23:283-293. [PMID: 29262760 DOI: 10.1177/2472555217746323] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
With early assessment of inhibitory properties of drug candidates and their circulating metabolites toward cytochrome P450 enzymes, drug attrition, especially later in the drug development process, can be decreased. Here we describe the development and validation of an at-line nanofractionation platform, which was applied for screening of CYP1A2 inhibitors in Phase I metabolic mixtures. With this platform, a metabolic mixture is separated by liquid chromatography (LC), followed by parallel nanofractionation on a microtiter well plate and mass spectrometry (MS) analysis. After solvent evaporation, all metabolites present in the nanofractionated mixture are assayed utilizing a fluorescence CYP1A2 inhibition bioassay performed on the plate. Next, a bioactivity chromatogram is constructed from the bioassay results. By peak shape and retention time correlation of the bioactivity peaks with the obtained MS data, CYP1A2-bioactive inhibiting metabolites can be identified. The method correctly evaluated the potency of five CYP1A2 inhibitors. Mixtures comprising potent inhibitors of CYP1A2 or in vitro-generated metabolites of ellipticine were evaluated for their inhibitory bioactivities. In both cases, good LC separation of all compounds was achieved and bioactivity data could be accurately correlated with the parallel recorded MS data. Generation and evaluation of Phase II metabolites of hydroxylated ellipticine was also pursued.
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Affiliation(s)
- Barbara M Zietek
- 1 Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Marija Mladic
- 1 Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Ben Bruyneel
- 1 Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Wilfried M A Niessen
- 1 Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, Amsterdam, Netherlands.,3 hyphen MassSpec, Voorhout, Netherlands
| | - Maarten Honing
- 1 Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, Amsterdam, Netherlands.,2 DSM Materials Science Center, Geleen, Netherlands
| | - Govert W Somsen
- 1 Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Jeroen Kool
- 1 Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
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3
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Mladic M, de Waal T, Burggraaff L, Slagboom J, Somsen GW, Niessen WMA, Manjunatha Kini R, Kool J. Rapid screening and identification of ACE inhibitors in snake venoms using at-line nanofractionation LC-MS. Anal Bioanal Chem 2017; 409:5987-5997. [PMID: 28801827 PMCID: PMC5602078 DOI: 10.1007/s00216-017-0531-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 06/13/2017] [Accepted: 07/17/2017] [Indexed: 11/05/2022]
Abstract
This study presents an analytical method for the screening of snake venoms for inhibitors of the angiotensin-converting enzyme (ACE) and a strategy for their rapid identification. The method is based on an at-line nanofractionation approach, which combines liquid chromatography (LC), mass spectrometry (MS), and pharmacology in one platform. After initial LC separation of a crude venom, a post-column flow split is introduced enabling parallel MS identification and high-resolution fractionation onto 384-well plates. The plates are subsequently freeze-dried and used in a fluorescence-based ACE activity assay to determine the ability of the nanofractions to inhibit ACE activity. Once the bioactive wells are identified, the parallel MS data reveals the masses corresponding to the activities found. Narrowing down of possible bioactive candidates is provided by comparison of bioactivity profiles after reversed-phase liquid chromatography (RPLC) and after hydrophilic interaction chromatography (HILIC) of a crude venom. Additional nanoLC-MS/MS analysis is performed on the content of the bioactive nanofractions to determine peptide sequences. The method described was optimized, evaluated, and successfully applied for screening of 30 snake venoms for the presence of ACE inhibitors. As a result, two new bioactive peptides were identified: pELWPRPHVPP in Crotalus viridis viridis venom with IC50 = 1.1 μM and pEWPPWPPRPPIPP in Cerastes cerastes cerastes venom with IC50 = 3.5 μM. The identified peptides possess a high sequence similarity to other bradykinin-potentiating peptides (BPPs), which are known ACE inhibitors found in snake venoms.
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Affiliation(s)
- Marija Mladic
- Division of BioAnalytical Chemistry, Amsterdam Institute for Molecules Medicines and Systems, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV, Amsterdam, The Netherlands
| | - Tessa de Waal
- Division of BioAnalytical Chemistry, Amsterdam Institute for Molecules Medicines and Systems, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV, Amsterdam, The Netherlands
| | - Lindsey Burggraaff
- Division of BioAnalytical Chemistry, Amsterdam Institute for Molecules Medicines and Systems, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV, Amsterdam, The Netherlands
| | - Julien Slagboom
- Division of BioAnalytical Chemistry, Amsterdam Institute for Molecules Medicines and Systems, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV, Amsterdam, The Netherlands
| | - Govert W Somsen
- Division of BioAnalytical Chemistry, Amsterdam Institute for Molecules Medicines and Systems, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV, Amsterdam, The Netherlands
| | - Wilfried M A Niessen
- Division of BioAnalytical Chemistry, Amsterdam Institute for Molecules Medicines and Systems, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV, Amsterdam, The Netherlands.,hyphen MassSpec, Herenweg 95, 2361 EK, Warmond, The Netherlands
| | - R Manjunatha Kini
- Department of Biological Science, National University of Singapore, 14 Science Drive 4, Singapore, 117543, Singapore
| | - Jeroen Kool
- Division of BioAnalytical Chemistry, Amsterdam Institute for Molecules Medicines and Systems, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV, Amsterdam, The Netherlands.
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Mladic M, Zietek BM, Iyer JK, Hermarij P, Niessen WM, Somsen GW, Kini RM, Kool J. At-line nanofractionation with parallel mass spectrometry and bioactivity assessment for the rapid screening of thrombin and factor Xa inhibitors in snake venoms. Toxicon 2016; 110:79-89. [DOI: 10.1016/j.toxicon.2015.12.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 12/04/2015] [Accepted: 12/16/2015] [Indexed: 12/26/2022]
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Otvos RA, Mladic M, Arias-Alpizar G, Niessen WMA, Somsen GW, Smit AB, Kool J. At-Line Cellular Screening Methodology for Bioactives in Mixtures Targeting the α7-Nicotinic Acetylcholine Receptor. ACTA ACUST UNITED AC 2016; 21:459-67. [DOI: 10.1177/1087057115625307] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 12/11/2015] [Indexed: 01/03/2023]
Abstract
The α7-nicotinic acetylcholine receptor (α7-nAChR) is a ligand-gated ion channel expressed in different regions of the central nervous system (CNS). The α7-nAChR has been associated with Alzheimer’s disease, epilepsy, and schizophrenia, and therefore is extensively studied as a drug target for the treatment of these diseases. Important sources for new compounds in drug discovery are natural extracts. Since natural extracts are complex mixtures, identification of the bioactives demands the use of analytical techniques to separate a bioactive from inactive compounds. This study describes screening methodology for identifying bioactive compounds in mixtures acting on the α7-nAChR. The methodology developed combines liquid chromatography (LC) coupled via a split with both an at-line calcium (Ca2+)-flux assay and high-resolution mass spectrometry (MS). This allows evaluation of α7-nAChR responses after LC separation, while parallel MS enables compound identification. The methodology was optimized for analysis of agonists and positive allosteric modulators, and was successfully applied to screening of the hallucinogen mushroom Psilocybe Mckennaii. The crude mushroom extract was analyzed using both reversed-phase and hydrophilic interaction liquid chromatography. Matching retention times and peak shapes of bioactives found with data from the parallel MS measurements allowed rapid pinpointing of accurate masses corresponding to the bioactives.
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Affiliation(s)
- Reka A. Otvos
- AIMMS Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
- Department of Molecular and Cellular Neurobiology, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - Marija Mladic
- AIMMS Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - Gabriela Arias-Alpizar
- AIMMS Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - Wilfried M. A. Niessen
- AIMMS Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
- hyphen MassSpec, Warmond, the Netherlands
| | - Govert W. Somsen
- AIMMS Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - August B. Smit
- Department of Molecular and Cellular Neurobiology, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - Jeroen Kool
- AIMMS Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
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Mladic M, Scholten DJ, Niessen WMA, Somsen GW, Smit MJ, Kool J. At-line coupling of LC-MS to bioaffinity and selectivity assessment for metabolic profiling of ligands towards chemokine receptors CXCR1 and CXCR2. J Chromatogr B Analyt Technol Biomed Life Sci 2015; 1002:42-53. [PMID: 26301479 DOI: 10.1016/j.jchromb.2015.08.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 08/03/2015] [Accepted: 08/04/2015] [Indexed: 11/28/2022]
Abstract
This study describes an analytical method for bioaffinity and selectivity assessment of CXCR2 antagonists and their metabolites. The method is based on liquid chromatographic separation (LC) of metabolic mixtures followed by parallel mass spectrometry (MS) identification and bioaffinity determination. The bioaffinity is assessed using radioligand binding assays in 96-well plates after at-line nanofractionation. The described method was optimized for chemokines and low-molecular weight CXCR2 ligands. The limits of detection (LODs; injected amounts) for MK-7123, a high affinity binder to both CXCR1 and CXCR2 receptors belonging to the diaminocyclobutendione chemical class, were 40pmol in CXCR1 binding and 8pmol in CXCR2 binding. For CXCL8, the LOD was 5pmol in both binding assays. A control compound was always taken along with each bioassay plate as triplicate dose-response curve. For MK-7123, the calculated IC50 values were 314±59nM (CXCR1 binding) and 38±11nM (CXCR2 binding). For CXCL8, the IC50 values were 6.9±1.4nM (CXCR1 binding) and 2.7±1.3nM (CXCR2 binding). After optimization, the method was applied to the analysis of metabolic mixtures of eight LMW CXCR2 antagonists generated by incubation with pig liver microsomes. Moreover, metabolic profiling of the MK-7123 compound was described using the developed method. Three bioactive metabolites were found, two of which were (partially) identified. This method is suitable for bioaffinity and selectivity assessment of mixtures targeting the CXCR2. In contrary to conventional LC-MS based metabolic profiling studies done at the early lead discovery stage, additional qualitative bioactivity information of drug metabolites is obtained with the method described.
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Affiliation(s)
- Marija Mladic
- Amsterdam Institute for Molecules Medicines and Systems, Division of BioAnalytical Chemistry, VU University Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands; Amsterdam Institute for Molecules Medicines and Systems, Division of Medicinal Chemistry, VU University Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands
| | - Danny J Scholten
- Amsterdam Institute for Molecules Medicines and Systems, Division of Medicinal Chemistry, VU University Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands
| | - Wilfried M A Niessen
- Amsterdam Institute for Molecules Medicines and Systems, Division of BioAnalytical Chemistry, VU University Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands; hyphen MassSpec, de Wetstraat 8, 2332XT Leiden, The Netherlands
| | - Govert W Somsen
- Amsterdam Institute for Molecules Medicines and Systems, Division of BioAnalytical Chemistry, VU University Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands
| | - Martine J Smit
- Amsterdam Institute for Molecules Medicines and Systems, Division of Medicinal Chemistry, VU University Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands
| | - Jeroen Kool
- Amsterdam Institute for Molecules Medicines and Systems, Division of BioAnalytical Chemistry, VU University Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands.
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7
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Mladic M, Scholten DJ, Wijtmans M, Falck D, Leurs R, Niessen WMA, Smit MJ, Kool J. Metabolic profiling of ligands for the chemokine receptor CXCR3 by liquid chromatography-mass spectrometry coupled to bioaffinity assessment. Anal Bioanal Chem 2015; 407:7067-81. [PMID: 26164305 PMCID: PMC4551560 DOI: 10.1007/s00216-015-8867-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 06/16/2015] [Accepted: 06/18/2015] [Indexed: 01/08/2023]
Abstract
Chemokine receptors belong to the class of G protein-coupled receptors and are important in the host defense against infections and inflammation. However, aberrant chemokine signaling is linked to different disorders such as cancer, central nervous system and immune disorders, and viral infections [Scholten DJ et al. (2012) Br J Pharmacol 165(6):1617–1643]. Modulating the chemokine receptor function provides new ways of targeting specific diseases. Therefore, discovery and development of drugs targeting chemokine receptors have received considerable attention from the pharmaceutical industry in the past decade. Along with that, the determination of bioactivities of individual metabolites derived from lead compounds towards chemokine receptors is crucial for drug selectivity, pharmacodynamics, and potential toxicity issues. Therefore, advanced analytical methodologies are in high demand. This study is aimed at the optimization of a new analytical method for metabolic profiling with parallel bioaffinity assessment of CXCR3 ligands of the azaquinazolinone and piperazinyl-piperidine class and their metabolites. The method is based on mass spectrometric (MS) identification after liquid chromatographic (LC) separation of metabolic mixtures. The bioaffinity assessment is performed “at-line” via high-resolution nanofractionation onto 96-well plates allowing direct integration of radioligand binding assays. This new method enables identification of metabolites from lead compounds with associated estimation of their individual bioaffinity. Moreover, the identification of the metabolite structures via accurate mass measurements and MS2 allows the identification of liable metabolic “hotspots” for further lead optimization. The efficient combination of chemokine receptor ligand binding assays with analytical techniques, involving nanofractionation as linking technology, allows implementation of comprehensive metabolic profiling in an early phase of the drug discovery process.
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Affiliation(s)
- Marija Mladic
- />Division of BioAnalytical Chemistry, Amsterdam Institute for Molecules Medicines and Systems, VU University Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands
- />Division of Medicinal Chemistry, Amsterdam Institute for Molecules Medicines and Systems, VU University Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands
| | - Danny J. Scholten
- />Division of Medicinal Chemistry, Amsterdam Institute for Molecules Medicines and Systems, VU University Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands
| | - Maikel Wijtmans
- />Division of Medicinal Chemistry, Amsterdam Institute for Molecules Medicines and Systems, VU University Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands
| | - David Falck
- />Division of BioAnalytical Chemistry, Amsterdam Institute for Molecules Medicines and Systems, VU University Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands
| | - Rob Leurs
- />Division of Medicinal Chemistry, Amsterdam Institute for Molecules Medicines and Systems, VU University Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands
| | - Wilfried M. A. Niessen
- />Division of BioAnalytical Chemistry, Amsterdam Institute for Molecules Medicines and Systems, VU University Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands
- />hyphen MassSpec, de Wetstraat 8, 2332 XT Leiden, The Netherlands
| | - Martine J. Smit
- />Division of Medicinal Chemistry, Amsterdam Institute for Molecules Medicines and Systems, VU University Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands
| | - Jeroen Kool
- />Division of BioAnalytical Chemistry, Amsterdam Institute for Molecules Medicines and Systems, VU University Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands
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Pieke E, Heus F, Kamstra JH, Mladic M, Velzen MV, Kamminga D, Lamoree MH, Hamers T, Leonards P, Niessen WMA, Kool J. High-Resolution Fractionation after Gas Chromatography for Effect-Directed Analysis. Anal Chem 2013; 85:8204-11. [DOI: 10.1021/ac401384q] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Eelco Pieke
- AIMMS Division of
BioAnalytical Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV
Amsterdam, The Netherlands
| | - Ferry Heus
- AIMMS Division of
BioAnalytical Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV
Amsterdam, The Netherlands
| | - Jorke H. Kamstra
- Institute for Environmental
Studies (IVM), Faculty of Earth and Life Sciences, VU University Amsterdam, De Boelelaan 1085, 1081 HV
Amsterdam, The Netherlands
| | - Marija Mladic
- AIMMS Division of
BioAnalytical Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV
Amsterdam, The Netherlands
| | - Martin van Velzen
- Institute for Environmental
Studies (IVM), Faculty of Earth and Life Sciences, VU University Amsterdam, De Boelelaan 1085, 1081 HV
Amsterdam, The Netherlands
| | - Dik Kamminga
- AIMMS Division of
BioAnalytical Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV
Amsterdam, The Netherlands
| | - Marja H. Lamoree
- Institute for Environmental
Studies (IVM), Faculty of Earth and Life Sciences, VU University Amsterdam, De Boelelaan 1085, 1081 HV
Amsterdam, The Netherlands
| | - Timo Hamers
- Institute for Environmental
Studies (IVM), Faculty of Earth and Life Sciences, VU University Amsterdam, De Boelelaan 1085, 1081 HV
Amsterdam, The Netherlands
| | - Pim Leonards
- Institute for Environmental
Studies (IVM), Faculty of Earth and Life Sciences, VU University Amsterdam, De Boelelaan 1085, 1081 HV
Amsterdam, The Netherlands
| | - Wilfried M. A. Niessen
- AIMMS Division of
BioAnalytical Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV
Amsterdam, The Netherlands
| | - Jeroen Kool
- AIMMS Division of
BioAnalytical Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV
Amsterdam, The Netherlands
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