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154 results on '"Schouten, Olaf"'

1. Short Term Outcomes of a Prospective Registry of Popliteal and Infrapopliteal Endovascular Interventions for Chronic Limb Threatening Ischaemia

Author

Akkersdijk, George P., Bekken, Joost A., Bosma, Jan, Buwalda, Mariska, Cuijpers-Patist, Bianca, Feenstra, Iris, de Fijter, W. Marnix, van den Haak, Ronald F.F., van Hattum, Eline S., (Koen) van Hees, C.P.A., van den Heuvel, Daniel A.F., Heyligers, Jan M.M., Hogendoorn, Wouter, van Huffelen, Kirsten, Hulsebos, Robin G., Jansze, Anouk, Koning, Olivier H.J., van Lammeren, Guus, van de Luijtgaarden, Koen M., van Mierlo – van den Broek, Patricia A.H., Petri, Bart-Jeroen, Schouten, Olaf, Schreve, Michiel A., Siebelt-Klapper, Ilona, de Smet, Andre A.E.A., Teraa, Martin, Toorop, Raechel J., Verhoeven, Bart A.N., Vriens, Patrick W.H.E., Nugteren, Michael J., Hazenberg, Constantijn E.V.B., Bakker, Olaf J., Dinkelman, Maarten K., Fioole, Bram, Hinnen, Jan-Willem, Pierie, Maurice, de Borst, Gert J., and Ünlü, Çağdaş

Published
2025
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3. Qualitative and quantitative characterization of elastin‐like polypeptides combining low‐PH/low‐temperature bottom‐up and intact protein liquid chromatography mass spectrometric analysis.

Author

Vente, André, Mladic, Marija, Schouten, Olaf, Thies, Jens, and van der Hoeven, Rob

Subjects
TANDEM mass spectrometry, ELECTROSPRAY ionization mass spectrometry, MATRIX effect, MASS spectrometers, COMPLEX matrices, THERMORESPONSIVE polymers
Abstract

Rationale: Elastin‐like polypeptides (ELPs) are elastic and thermoresponsive biopolymers composed of VPGXG repeats (X can be any amino acid except proline), used in biomedical applications, for example, tissue engineering and drug delivery. As different variants of ELP are mostly produced fermentatively, there is a need for the development of analysis methods that allow for absolute protein quantification in both complex matrices and purified samples and MW determination of the final products. Methods: ELPs were intracellularly expressed in Escherichia coli quantified after cell lysis and enzymatic digestion using a proline‐specific protease ProAlanase (Promega) at acidic conditions. Resulting peptides were separated by liquid chromatography, and mass spectrometry analysis was conducted by electrospray ionization high‐resolution mass spectrometry using an Orbitrap mass spectrometer. The addition of a stable isotopically labeled internal standard enabled quantification in complex matrices. Prior to intact mass analysis, ELPs were purified from fermentation broth by inverse temperature cycling. Intact protein analysis was performed using reversed‐phase liquid chromatography, and mass spectrometry analysis was conducted by electrospray ionization high‐resolution mass spectrometry using a time‐of‐flight mass spectrometer. Results: Absolute quantification of ELPs was achieved by utilizing ELP‐specific properties, that is, proline‐rich, soluble at low pH and low temperature. The repetitive nature of ELPs allows for sensitivity increase and use of higher dilution factors to minimize the matrix effects. Despite the lack of amino acids with charged side chains (Arg, His, Lys, Asp, and Glu) in ELP, we demonstrated successful intact protein analysis using reversed‐phase LC coupled to electrospray ionization TOF MS. Moreover, truncated protein forms could be chromatographically separated and characterized as well as N‐terminal modifications. Conclusions: Both methods combined enabled quantitative and qualitative characterization of fermentatively produced ELPs. [ABSTRACT FROM AUTHOR]

Published
2024
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5. The Dutch chronic lower limb-threatening ischemia registry (THRILLER): A study protocol for popliteal and infrapopliteal endovascular interventions.

Author

Nugteren, Michael J., Hazenberg, Constantijn E. V. B., Akkersdijk, George P., Bakker, Olaf J., Dinkelman, Maarten K., Fioole, Bram, van den Heuvel, Daniel A. F., Heyligers, Jan M. M., Hinnen, Jan-Willem, Pierie, Maurice, Schouten, Olaf, Schreve, Michiel A., Verhoeven, Bart A. N., de Borst, Gert J., and Ünlü, Çağdaş

Subjects
ENDOVASCULAR surgery, DUPLEX ultrasonography, RESEARCH protocols, PERIPHERAL vascular diseases, LIMB salvage, ISCHEMIA
Abstract

Introduction: Chronic limb-threatening ischemia (CLTI) is the end stage of peripheral arterial disease (PAD) and is associated with high amputation rates, mortality and disease-related health care costs. In infrapopliteal arterial disease (IPAD), endovascular revascularization should be considered for the majority of anatomical and clinical subgroups of CLTI. However, a gap of high-quality evidence exists in this field. The aim of the Dutch Chronic Lower Limb-Threatening Ischemia Registry (THRILLER) is to collect real world data on popliteal and infrapopliteal endovascular interventions. Methods: THRILLER is a clinician-driven, prospective, multicenter, observational registry including all consecutive patients that undergo a popliteal or infrapopliteal endovascular intervention in seven Dutch hospitals. We estimate that THRILLER will include 400–500 interventions annually. Standardized follow-up visits with wound monitoring, toe pressure measurement and duplex ultrasonography will be scheduled at 6–8 weeks and 12 months after the intervention. The independent primary endpoints are primary patency, limb salvage and amputation free survival. Patients must give informed consent before participation and will be included according to predefined reporting standards. A data log of patients who meet the inclusion criteria but are not included in the registry will be maintained. We intend to conduct the first interim analysis two years after the start of inclusion. The results will be published in a scientific journal. Discussion: Despite innovations in medical therapy and revascularization techniques, patients with CLTI undergoing endovascular revascularization still have a moderate prognosis. Previous prospective cohort studies were hampered by small sample sizes or heterogeneous reporting. Randomized controlled trials (RCTs) have high costs, potential conflicts of interest and give a limited reflection of daily practice. THRILLER aims to provide the largest prospective well phenotyped up-to-date dataset on treatment outcomes in CLTI patients to answer multiple underexplored research questions regarding diagnostics, medication, patient selection, treatment strategies and post intervention follow-up. [ABSTRACT FROM AUTHOR]

Published
2023
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8. Native Structural and Functional Proteoform Characterization of the Prolyl-Alanyl-Specific Endoprotease EndoPro from Aspergillus niger

Author

van Schaick, Guusje, Domínguez-Vega, Elena, Gstöttner, Christoph, van den Berg-Verleg, Johanna H, Schouten, Olaf, Akeroyd, Michiel, Olsthoorn, Maurien M A, Wuhrer, Manfred, Heck, Albert J R, Abello, Nicolas, Franc, Vojtech, Afd Biomol.Mass Spect. and Proteomics, Sub Biomol.Mass Spectrometry & Proteom., Biomolecular Mass Spectrometry and Proteomics, Afd Biomol.Mass Spect. and Proteomics, Sub Biomol.Mass Spectrometry & Proteom., and Biomolecular Mass Spectrometry and Proteomics

Subjects
anion exchange chromatography, Glycan, Glycosylation, Chemistry(all), medicine.medical_treatment, Proteomics, Biochemistry, chemistry.chemical_compound, medicine, prolyl-alanyl-specific endoprotease, mass spectrometry, chemistry.chemical_classification, Protease, biology, Chemistry, Aspergillus niger, General Chemistry, biology.organism_classification, Glycopeptide, structure-function relationship, Enzyme, biology.protein, Phosphorylation, native separation
Abstract

The prolyl-alanyl-specific endoprotease (EndoPro) is an industrial enzyme produced in Aspergillus niger. EndoPro is mainly used for food applications but also as a protease in proteomics. In-depth characterization of this enzyme is essential to understand its structural features and functionality. However, there is a lack of analytical methods capable of maintaining both the structural and functional integrity of separated proteoforms. In this study, we developed an anion exchange (AEX) method coupled to native mass spectrometry (MS) for profiling EndoPro proteoforms. Moreover, we investigated purified EndoPro proteoforms with complementary MS-based approaches, including released N-glycan and glycopeptide analysis, to obtain a comprehensive overview of the structural heterogeneity. We showed that EndoPro has at least three sequence variants and seven N-glycosylation sites occupied by high-mannose glycans that can be phosphorylated. Each glycosylation site showed high microheterogeneity with ∼20 glycans per site. The functional characterization of fractionated proteoforms revealed that EndoPro proteoforms remained active after AEX-separation and the specificity of these proteoforms did not depend on N-glycan phosphorylation. Nevertheless, our data confirmed a strong pH dependence of EndoPro cleavage activity. Altogether, our study demonstrates that AEX-MS is an excellent tool to characterize complex industrial enzymes under native conditions.

Published
2021
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18. Non-coronary atherosclerosis

Author

Gallino, Augusto, Aboyans, Victor, Diehm, Curt, Cosentino, Francesco, Stricker, Hans, Falk, Erling, Schouten, Olaf, Lekakis, John, Amann-Vesti, Beatrice, Siclari, Francesco, Poredos, Pavel, Novo, Salvatore, Brodmann, Marianne, Schulte, Karl-Ludwig, Vlachopoulos, Charalambos, De Caterina, Raffaele, Libby, Peter, and Baumgartner, Iris

Published
2014
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34. The efficacy and safety of clopidogrel in vascular surgery patients with immediate postoperative asymptomatic troponin T release for the prevention of late cardiac events: Rationale and design of the Dutch Echocardiographic Cardiac Risk Evaluation Applying Stress Echo-VII (DECREASE-VII) trial

Author

van Kuijk, Jan-Peter, Voute, Michiel T., Flu, Willem-Jan, Schouten, Olaf, Chonchol, Michel, Hoeks, Sanne E., Boersma, Eric E., Verhagen, Hence J.M., Bax, Jeroen J., and Poldermans, Don

Published
2010

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