Skip to ContentSkip to Navigation
Over ons Actueel Voor de pers

Walvoort, prof. dr. Marthe

Marthe Walvoort
Marthe Walvoort

Marthe Walvoort is universitair docent scheikunde op de Rijksuniversiteit Groningen. Ze onderzoekt de werking en functie van suikermoleculen. Die zitten niet alleen in eten, maar ook in papier of aan de buitenkant van bacteriën en virussen. Walvoort bestudeert deze moleculen door ze na te maken in het laboratorium. Dit staat, in tegenstelling tot het namaken van DNA- en eiwitketens, nog in de kinderschoenen. Een groot gedeelte van haar onderzoek draait daarom om het ontwikkelen van nieuwe methodes om suikerketens te maken.

Bacteriën gebruiken suikers vaak om andere cellen te infecteren. De kennis die het onderzoek van Walvoort oplevert, kan daardoor leiden tot nieuwe manieren om bacteriën onschadelijk te maken. Een ander speerpunt is het ontwikkelen van suikerketens die de groei van goede bacteriën stimuleren ten opzichte van slechte, waardoor in de toekomst minder antibiotica nodig is. In 2022 kreeg Walvoort een ERC Starting Grant ter waarde van 1,5 miljoen euro toegekend voor dit onderzoek.

Walvoort deed aan het eind van haar studie scheikunde in Leiden een jaar onderzoek in Oxford. Daarna promoveerde ze in Leiden cum laude in de scheikunde en was ze van 2012 tot 2015 als postdoctoraal onderzoeker verbonden aan het Massachusetts Institute of Technology (MIT).

Marthe Walvoort is Rosalind Franklin Fellow aan de Rijksuniversiteit Groningen en tevens een van de oprichters van de Young Academy Groningen.

Eerder in het nieuws

Artikel RTV Noord
Artikel RTV Noord

Contact en meer informatie

Publicaties

2024

Tang, X., Chen, X. C., Ferrari, M., Walvoort, M. T. C., & de Vos, P. (2024). Gut Epithelial Barrier Function is Impacted by Hyperglycemia and Secondary Bile Acids in Vitro: Possible Rescuing Effects of Specific Pectins. Molecular Nutrition & Food Research, 68(11), Article e2300910. https://doi.org/10.1002/mnfr.202300910
Ferrari, M., van Leeuwen, S. S., de Vos, P., Jurak, E., & Walvoort, M. T. C. (2025). Impact of GOS and 2’-FL on the production and structural composition of membrane-associated exopolysaccharides by B. adolescentis and B. infantis. Carbohydrate Polymers, 347, Article 122660. Advance online publication. https://doi.org/10.1016/j.carbpol.2024.122660
Marinus, N., Walvoort, M. T. C., Witte, M. D., Minnaard, A. J., & Van Dijk, J. H. M. (2024). Regioselective Palladium Catalyzed Oxidation at C-3 of Methyl Glucoside. In Carbohydrate Chemistry: Proven Synthetic Methods, Volume 5 (Vol. 5, pp. 129-134). CRC Press.
Rampratap, P., Lasorsa, A., Arunachalam, A., Kamperman, M., Walvoort, M. T. C., & van der Wel, P. C. A. (2024). Resolving Atomic-Level Dynamics and Interactions of High-Molecular-Weight Hyaluronic Acid by Multidimensional Solid-State NMR. ACS Applied Materials & Interfaces, 16(33), 43317–43328. https://doi.org/10.1021/acsami.4c08428
Chen, X., Gasaly, N., Tang, X., Walvoort, M. T. C., & de Vos, P. (2024). The effect of nerve cells on the intestinal barrier function and the influence of human milk oligosaccharides (hMOs) on the intestinal neuro-epithelial crosstalk. Current Research in Food Science, 9, Article 100851. https://doi.org/10.1016/j.crfs.2024.100851

2023

Akkerman, R., Oerlemans, M. M. P., Ferrari, M., Fernández-Lainez, C., de Haan, B. J., Faas, M. M., Walvoort, M. T. C., & de Vos, P. (2024). Exopolysaccharide β-(2,6)-levan-type fructans have a molecular-weight-dependent modulatory effect on Toll-like receptor signalling. Food & Function, 15(2), 676-688. https://doi.org/10.1039/d3fo03066k
Reintjens, N. R. M., Bartels, I. M. A., Marinus, N., Massmann, S. C., Bunt, D. V., Walvoort, M. T. C., Witte, M. D., & Minnaard, A. J. (2024). Practical Site-Selective Oxidation of Glycosides with Palladium(II) Acetate/Neocuproine. Synlett, 35(11), 1291-1295. Article a-2186-1485. https://doi.org/10.1055/a-2186-1485
Tang, X., Beukema, M., Ferrari, M., Walvoort, M. T. C., de Haan, B. J., & de Vos, P. (2023). Efficacy of pectins with different degrees of methyl-esterification and of blockiness in preventing gut epithelial cell barrier disruption and the impact on sodium-glucose co-transporter expression under low and high glucose conditions. Food & Function, 14(13), 6226-6235. https://doi.org/10.1039/d3fo01436c
Ziylan, Z. S., de Putter, G. J., Roelofs, M., van Dijl, J. M., Scheffers, D. J., & Walvoort, M. T. C. (2023). Evaluation of Kdo-8-N3 incorporation into lipopolysaccharides of various Escherichia coli strains. RSC Chemical Biology, 4(11), 884–893. https://doi.org/10.1039/d3cb00110e
Low, K. E., Gheorghita, A. A., Tammam, S. D., Whitfield, G. B., Li, Y. E., Riley, L. M., Weadge, J. T., Caldwell, S. J., Chong, P. A., Walvoort, M. T. C., Kitova, E. N., Klassen, J. S., Codée, J. D. C., & Howell, P. L. (2023). Pseudomonas aeruginosa AlgF is a protein-protein interaction mediator required for acetylation of the alginate exopolysaccharide. The Journal of Biological Chemistry, 299(11), Article 105314. https://doi.org/10.1016/j.jbc.2023.105314
Rampratap, P., Lasorsa, A., Perrone, B., van der Wel, P. C. A., & Walvoort, M. T. C. (2023). Production of isotopically enriched high molecular weight hyaluronic acid and characterization by solid-state NMR. Carbohydrate Polymers, 316, 121063. https://doi.org/10.1016/j.carbpol.2023.121063

2022

Reintjens, N. R. M., Yakovlieva, L., Marinus, N., Hekelaar, J., Nuti, F., Papini, A. M., Witte, M. D., Minnaard, A. J., & Walvoort, M. T. C. (2022). Palladium-Catalyzed Oxidation of Glucose in Glycopeptides. European Journal of Organic Chemistry, 2022(25), Article e202200677. https://doi.org/10.1002/ejoc.202200677
Versloot, R. C. A., Lucas, F. L. R., Yakovlieva, L., Tadema, M. J., Zhang, Y., Wood, T. M., Martin, N. I., Marrink, S. J., Walvoort, M. T. C., & Maglia, G. (2022). Quantification of Protein Glycosylation Using Nanopores. Nano Letters, 22(13), 5357-5364. Article 2c10338. https://doi.org/10.1021/acs.nanolett.2c01338
Gheorghita, A. A., Li, Y. E., Kitova, E. N., Bui, D. T., Pfoh, R., Low, K. E., Whitfield, G. B., Walvoort, M. T. C., Zhang, Q., Codée, J. D. C., Klassen, J. S., & Howell, P. L. (2022). Structure of the AlgKX modification and secretion complex required for alginate production and biofilm attachment in Pseudomonas aeruginosa. Nature Communications, 13(1), Article 7631. https://doi.org/10.1038/s41467-022-35131-6

2021

Ferrari, M., Hameleers, L., Stuart, M. C. A., Oerlemans, M. M. P., de Vos, P., Jurak, E., & Walvoort, M. T. C. (2022). Efficient isolation of membrane-associated exopolysaccharides of four commercial bifidobacterial strains. Carbohydrate Polymers, 278, Article 118913. https://doi.org/10.1016/j.carbpol.2021.118913
Yakovlieva, L., Wood, T. M., Kemmink, J., Kotsogianni, I., Koller, F., Lassak, J., Martin, N. I., & Walvoort, M. T. C. (2021). A β-hairpin epitope as novel structural requirement for protein arginine rhamnosylation. Chemical Science, 12(4), 1560-1567. https://doi.org/10.1039/d0sc05823h
Oerlemans, M., Akkerman, R., Ferrari, M., Walvoort, M., & Vos, de, P. (2021). Benefits of bacteria-derived exopolysaccharides on gastrointestinal microbiota, immunity and health. Journal of Functional Foods, 76, Article 104289. https://doi.org/10.1016/j.jff.2020.104289
Yakovlieva, L., Fülleborn, J. A., & Walvoort, M. T. C. (2021). Corrigendum: Opportunities and Challenges of Bacterial Glycosylation for the Development of Novel Antibacterial Strategies (Front. Microbiol., (2021), 12, (745702), 10.3389/fmicb.2021.745702). Frontiers in Microbiology, 12, Article 803203. https://doi.org/10.3389/fmicb.2021.803203
Verkhnyatskaya, S. A., Kong, C., Klostermann, C. E., Schols, H. A., de Vos, P., & Walvoort, M. T. C. (2021). Digestion, fermentation, and pathogen anti-adhesive properties of the hMO-mimic di-fucosyl-β-cyclodextrin. Food and Function, 12(11), 5018-5026. https://doi.org/10.1039/d1fo00830g
Yakovlieva, L., Fülleborn, J. A., & Walvoort, M. T. C. (2021). Opportunities and Challenges of Bacterial Glycosylation for the Development of Novel Antibacterial Strategies. Frontiers in Microbiology, 12, Article 745702. https://doi.org/10.3389/fmicb.2021.745702
Lucas, F. L. R., Versloot, R. C. A., Yakovlieva, L., Walvoort, M. T. C., & Maglia, G. (2021). Protein identification by nanopore peptide profiling. Nature Communications, 12, Article 5795. https://doi.org/10.1038/s41467-021-26046-9
Leeuwenburgh, V. C., Urzua-Traslavina, C. G., Bhattacharya, A., Walvoort, M. T. C., Jalving, M., de Jong, S., & Fehrmann, R. S. N. (2021). Robust metabolic transcriptional components in 34,494 patient-derived cancer-related samples and cell lines. Cancer & Metabolism, 9(1), Article 35. https://doi.org/10.1186/s40170-021-00272-7
Yakovlieva, L., Ramírez-Palacios, C., Marrink, S. J., & Walvoort, M. T. C. (2021). Semiprocessive Hyperglycosylation of Adhesin by Bacterial Protein N-Glycosyltransferases. ACS chemical biology, 16(1), 165-175. https://doi.org/10.1021/acschembio.0c00848

2020

Cheng, L., Akkerman, R., Kong, C., Walvoort, M. T. C., & de Vos, P. (2021). More than sugar in the milk: human milk oligosaccharides as essential bioactive molecules in breast milk and current insight in beneficial effects. Critical Reviews in Food Science and Nutrition, 61(7), 1184-1200. https://doi.org/10.1080/10408398.2020.1754756
Cheng, L., Kiewiet, M. B. G., Logtenberg, M. J., Groeneveld, A., Nauta, A., Schols, H. A., Walvoort, M. T. C., Harmsen, H. J. M., & de Vos, P. (2020). Effects of Different Human Milk Oligosaccharides on Growth of Bifidobacteria in Monoculture and Co-culture With Faecalibacterium prausnitzii. Frontiers in Microbiology, 11, Article 569700. https://doi.org/10.3389/fmicb.2020.569700
Kong, C., Cheng, L., Krenning, G., Fledderus, J., de Haan, B. J., Walvoort, M. T., & de Vos, P. (2020). Human Milk Oligosaccharides Mediate the Crosstalk Between Intestinal Epithelial Caco-2 Cells and Lactobacillus Plantarum WCFS1 in an In Vitro Model with Intestinal Peristaltic Shear Force. The Journal of Nutrition, 150(8), 2077-2088. Article nxaa162. https://doi.org/10.1093/jn/nxaa162
Hu, S., Kuwabara, R., Beukema, M., Ferrari, M., de Haan, B. J., Walvoort, M. T. C., de Vos, P., & Smink, A. M. (2020). Low methyl-esterified pectin protects pancreatic beta-cells against diabetes-induced oxidative and inflammatory stress via galectin-3. Carbohydrate Polymers, 249, Article 116863. https://doi.org/10.1016/j.carbpol.2020.116863
Zhang, J., Yakovlieva, L., de Haan, B. J., de Vos, P., Minnaard, A. J., Witte, M. D., & Walvoort, M. T. C. (2020). Selective Modification of Streptozotocin at the C3 Position to Improve Its Bioactivity as Antibiotic and Reduce Its Cytotoxicity towards Insulin-Producing β Cells. Antibiotics , 9(4), Article 182. https://doi.org/10.3390/antibiotics9040182

2019

Yakovlieva, L., & Walvoort, M. T. C. (2020). Processivity in Bacterial Glycosyltransferases. ACS chemical biology, 15(1), 3-16. https://doi.org/10.1021/acschembio.9b00619
Verkhnyatskaya, S. A., de Vries, A. H., Douma-de Vries, E., Sneep, R. J. L., & Walvoort, M. T. C. (2019). Direct and Regioselective Di-alpha-fucosylation on the Secondary Rim of beta-Cyclodextrin: Cover Profile. Chemistry, 25(27), 6649-6649. https://doi.org/10.1002/chem.201901257
Verkhnyatskaya, S. A., de Vries, A. H., Douma-de Vries, E., Sneep, E. J. L., & Walvoort, M. T. C. (2019). Direct and Regioselective Di-alpha-fucosylation on the Secondary Rim of beta-Cyclodextrin. Chemistry, 25(27), 6722-6727. https://doi.org/10.1002/chem.201806090
Cheng, L., Kong, C., Walvoort, M. T. C., Faas, M. M., & de Vos, P. (2019). Human Milk Oligosaccharides Differently Modulate Goblet Cells Under Homeostatic, Proinflammatory Conditions and ER Stress. Molecular Nutrition & Food Research, Article 1900976. https://doi.org/10.1002/mnfr.201900976
Verkhnyatskaya, S., Ferrari, M., de Vos, P., & Walvoort, M. T. C. (2019). Shaping the Infant Microbiome With Non-digestible Carbohydrates. Frontiers in Microbiology, 10, Article 343. https://doi.org/10.3389/fmicb.2019.00343

2018

Walvoort, M., Fehrmann, R., & Leeuwenburgh, V. (2018). Novel tools to dissect and monitor tumor metabolism in melanoma patients. Digital or Visual Products
Leeuwenburgh, V., Bhattacharya, A., Urzua, C., Walvoort, M., Jalving, H., de Jong, S., & Fehrmann, R. (2018). The metabolic landscape browser: a novel tool for understanding pan-cancer metabolic processes through variance in gene expression data. European Journal of Cancer, 103(Suppl.1), E106-E106. Article 318 (PB-079).

2017

Lukose, V., Walvoort, M. T. C., & Imperiali, B. (2017). Bacterial phosphoglycosyl transferases: initiators of glycan biosynthesis at the membrane interface. Glycobiology, 27(9), 820-833. Article cwx064. https://doi.org/10.1093/glycob/cwx064
Walvoort, M. T. C., Testa, C., Eilam, R., Aharoni, R., Nuti, F., Rossi, G., Real-Fernandez, F., Lanzillo, R., Brescia Morra, V., Lolli, F., Rovero, P., Imperiali, B., & Papini, A. M. (2017). Erratum: Antibodies from multiple sclerosis patients preferentially recognize hyperglucosylated adhesin of non-typeable Haemophilus influenzae. Scientific Reports, 7, 44969. https://doi.org/10.1038/srep44969
Bdira, F. B., Kallemeijn, W. W., Oussoren, S. V., Scheij, S., Bleijlevens, B., Florea, B. I., van Roomen, C. P. A. A., Ottenhoff, R., van Kooten, M. J. F. M., Walvoort, M. T. C., Witte, M. D., Boot, R. G., Ubbink, M., Overkleeft, H. S., & Aerts, J. M. F. G. (2017). Stabilization of Glucocerebrosidase by Active Site Occupancy. ACS chemical biology, 12(7), 1830-1841. https://doi.org/10.1021/acschembio.7b00276

2016

Walvoort, M. T. C., Lukose, V., & Imperiali, B. (2016). A Modular Approach to Phosphoglycosyltransferase Inhibitors Inspired by Nucleoside Antibiotics. Chemistry : a European Journal, 22(11), 3856-3864. https://doi.org/10.1002/chem.201503986
Walvoort, M. T. C., Testa, C., Eilam, R., Aharoni, R., Nuti, F., Rossi, G., Real-Fernandez, F., Lanzillo, R., Brescia Morra, V., Lolli, F., Rovero, P., Imperiali, B., & Papini, A. M. (2016). Antibodies from multiple sclerosis patients preferentially recognize hyperglucosylated adhesin of non-typeable Haemophilus influenzae. Scientific Reports, 6, Article 39430. https://doi.org/10.1038/srep39430
Das, D., Walvoort, M. T. C., Lukose, V., & Imperiali, B. (2016). A Rapid and Efficient Luminescence-based Method for Assaying Phosphoglycosyltransferase Enzymes. Scientific Reports, 6, Article 33412. https://doi.org/10.1038/srep33412

2015

Zhang, Q., van Rijssel, E. R., Walvoort, M. T. C., Overkleeft, H. S., van der Marel, G. A., & Codee, J. D. C. (2015). Acceptor Reactivity in the Total Synthesis of Alginate Fragments Containing -L-Guluronic Acid and -D-Mannuronic Acid. Angewandte Chemie - International Edition, 54(26), 7670-7673. https://doi.org/10.1002/anie.201502581

2014

Wolfram, F., Kitova, E. N., Robinson, H., Walvoort, M. T. C., Codee, J. D. C., Klassen, J. S., & Howell, P. L. (2014). Catalytic Mechanism and Mode of Action of the Periplasmic Alginate Epimerase AlgG. The Journal of Biological Chemistry, 289(9), 6006-6019. https://doi.org/10.1074/jbc.M113.533158
Baker, P., Ricer, T., Moynihan, P. J., Kitova, E. N., Walvoort, M. T. C., Little, D. J., Whitney, J. C., Dawson, K., Weadge, J. T., Robinson, H., Ohman, D. E., Codee, J. D. C., Klassen, J. S., Clarke, A. J., & Howell, P. L. (2014). P. aeruginosa SGNH Hydrolase-Like Proteins AlgJ and AlgX Have Similar Topology but Separate and Distinct Roles in Alginate Acetylation. PLoS Pathogens, 10(8), Article e1004334. https://doi.org/10.1371/journal.ppat.1004334
Li, K. Y., Kallemeijn, W., Jiang, J., Walvoort, M., Willems, L., Beenakker, T., Van Den Elst, H., Van Der Marel, G., Codée, J., Aerts, H., Florea, B., Boot, R., Witte, M., & Overkleeft, H. (2014). Rational Design of Activity-Based Retaining β-Exoglucosidase Probes. In Concepts and Case Studies in Chemical Biology (Vol. 9783527336111, pp. 191-206). Wiley-Blackwell. https://doi.org/10.1002/9783527687503.ch13

2013

Ronnols, J., Walvoort, M. T. C., van der Marel, G. A., Codee, J. D. C., & Widmalm, G. (2013). Chair interconversion and reactivity of mannuronic acid esters. Organic & Biomolecular Chemistry, 11(46), 8127-8134. https://doi.org/10.1039/c3ob41747f
Frihed, T. G., Walvoort, M. T. C., Codee, J. D. C., van der Marel, G. A., Bols, M., & Pedersen, C. M. (2013). Influence of O6 in Mannosylations Using Benzylidene Protected Donors: Stereoelectronic or Conformational Effects? Journal of Organic Chemistry, 78(6), 2191-2205. https://doi.org/10.1021/jo302455d

2012

Walvoort, M. T. C., van den Elst, H., Plante, O. J., Kroeck, L., Seeberger, P. H., Overkleeft, H. S., van der Marel, G. A., & Codee, J. D. C. (2012). Automated Solid-Phase Synthesis of beta-Mannuronic Acid Alginates. Angewandte Chemie - International Edition, 51(18), 4393-4396. https://doi.org/10.1002/anie.201108744
Walvoort, M. T. C., Volbeda, A. G., Reintjens, N. R. M., van den Elst, H., Plante, O. J., Overkleeft, H. S., van der Marel, G. A., & Codee, J. D. C. (2012). Automated Solid-Phase Synthesis of Hyaluronan Oligosaccharides. Organic letters, 14(14), 3776-3779. https://doi.org/10.1021/ol301666n
Walvoort, M. T. C., van der Marel, G. A., Overkleeft, H. S., & Codee, J. D. C. (2012). On the reactivity and selectivity of donor glycosides in glycochemistry and glycobiology: trapped covalent intermediates. Chemical Science, 4(3), 897-906. https://doi.org/10.1039/c2sc21610h
Walvoort, M. T. C., Sail, D., van der Marel, G. A., & Codée, J. D. C. (2012). Synthesis of Methyl Glycuronates by Chemoand Regioselective TEMPO/BAIB-Oxidation. In P. Kovác (Ed.), Carbohydrate chemistry: proven synthetic methods (Vol. 1, pp. 99-105). CRC Press. https://doi.org/10.1201/b11261-17
Walvoort, M. T. C., Kallemeijn, W. W., Willems, L. I., Witte, M. D., Aerts, J. M. F. G., van der Marel, G. A., Codee, J. D. C., & Overkleeft, H. S. (2012). Tuning the leaving group in 2-deoxy-2-fluoroglucoside results in improved activity-based retaining beta-glucosidase probes. Chemical Communications, 48(84), 10386-10388. https://doi.org/10.1039/c2cc35653h

2011

Witte, M. D., Walvoort, M. T. C., Li, K.-Y., Kallemeijn, W. W., Donker-Koopman, W. E., Boot, R. G., Aerts, J. M. F. G., Codee, J. D. C., van der Marel, G. A., & Overkleeft, H. S. (2011). Activity-Based Profiling of Retaining beta-Glucosidases: A Comparative Study. ChemBioChem, 12(8), 1263-1269. https://doi.org/10.1002/cbic.201000773
Walvoort, M. T. C., de Witte, W., van Dijk, J., Dinkelaar, J., Lodder, G., Overkleeft, H. S., Codee, J. D. C., & van der Marel, G. A. (2011). Mannopyranosyl Uronic Acid Donor Reactivity. Organic letters, 13(16), 4360-4363. https://doi.org/10.1021/ol2016862
Codee, J. D. C., Walvoort, M. T. C., de Jong, A.-R., Lodder, G., Overkleeft, H. S., & van der Marel, G. A. (2011). Mannuronic Acids: Reactivity and Selectivity. Journal of carbohydrate chemistry, 30(7-9), 438-457. https://doi.org/10.1080/07328303.2011.624284
Walvoort, M. T. C., Moggre, G.-J., Lodder, G., Overkleeft, H. S., Codee, J. D. C., & van der Marel, G. A. (2011). Stereoselective Synthesis of 2,3-Diamino-2,3-dideoxy-beta-D-mannopyranosyl Uronates. Journal of Organic Chemistry, 76(18), 7301-7315. https://doi.org/10.1021/jo201179p
Codee, J. D. C., Christina, A. E., Walvoort, M. T. C., Overkleeft, H. S., & Van der Marel, G. A. (2011). Uronic Acids in Oligosaccharide and Glycoconjugate Synthesis. In B. FraserReid, & JC. Lopez (Eds.), REACTIVITY TUNING IN OLIGOSACCHARIDE ASSEMBLY (pp. 253-289). (Topics in Current Chemistry; Vol. 301). Springer. https://doi.org/10.1007/128_2010_111

2010

Walvoort, M. T. C., Lodder, G., Overkleeft, H. S., Codee, J. D. C., & van der Marel, G. A. (2010). Mannosazide Methyl Uronate Donors. Glycosylating Properties and Use in the Construction of beta-ManNAcA-Containing Oligosaccharides. Journal of Organic Chemistry, 75(23), 7990-8002. https://doi.org/10.1021/jo101779v
Walvoort, M. T. C., Dinkelaar, J., van den Bos, L. J., Lodder, G., Overkleeft, H. S., Codee, J. D. C., & van der marel, G. A. (2010). The impact of oxacarbenium ion conformers on the stereochemical outcome of glycosylations. Carbohydrate Research, 345(10), 1252-1263. https://doi.org/10.1016/j.carres.2010.02.027

2009

Walvoort, M. T. C., Lodder, G., Mazurek, J., Overkleeft, H. S., Codee, J. D. C., & van der Marel, G. A. (2009). Equatorial Anomeric Triflates from Mannuronic Acid Esters. Journal of the American Chemical Society, 131(34), 12080-12081. https://doi.org/10.1021/ja905008p
Laatst gewijzigd:15 juli 2024 08:58
View this page in: English