Gijsbert Zomer

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The effects of the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) were studied in DNA repair deficient XPA(-/-) mice. The nullizygous XPA-knockout mice, which lack a functional nucleotide excision repair (NER) pathway, were exposed to dietary concentrations ranging from 10 to 200 p.p.m. The results show that PhIP is extremely toxic to(More)
Outer membrane vesicles (OMV) contain immunogenic proteins and contribute to in vivo survival and virulence of bacterial pathogens. The first OMV vaccines successfully stopped Neisseria meningitidis serogroup B outbreaks but required detergent-extraction for endotoxin removal. Current vaccines use attenuated endotoxin, to preserve immunological properties(More)
An improved detergent-free process has been developed to produce vaccine based on native outer membrane vesicles (NOMV) against Neisseria meningitidis serogroup B. Performance was evaluated with the NonaMen vaccine concept, which provides broad coverage based on nine distinct PorA antigens. Scalable aseptic equipment was implemented, replacing undesirable(More)
Four blisters with suspect Cialis (tadalafil) 20mg tablets were screened for authenticity using near infrared spectroscopy (NIRS) and for the presence of phosphodiesterase 5 (PDE-5) inhibitors using LC-DAD-MS. All samples were identified as counterfeit Cialis and contained sildenafil or a combination of tadalafil and sildenafil. Although the tablets(More)
The bacterial cell-wall-associated teichoic acids contain predominantly D-ribitol residues interconnected by phosphodiester linkages. Because of their location, these antigens may be vaccine candidates as part of conjugate vaccines. Here, we describe the synthesis of extended oligomers of D-ribitol-1-phosphate linked to a spacer having an amino group at its(More)
Proton NMR was evaluated as an alternative to amino acid analysis as an identity test for peptides. Proton NMR can readily distinguish and identify all peptides currently described in the European Pharmacopoeia (Ph. Eur.). A comparison with amino acid analysis as an identity test is presented.
A new analogue of sildenafil was detected in a herbal aphrodisiac. The structure of the compound was established using LC-MS, UV and IR spectroscopy, MS-MS, and NMR. The compound, named thio-homosildenafil is a synthetic N-ethylpiperazine analogue of sildenafil in which also the CO moiety has been converted into a CS group. This is the first time a(More)
Fifty saponin components of Quil A, a commercially available extract from the bark of the South American tree Quillaja saponaria Molina, were partially structurally characterised. The molecular weights were determined by fast-atom bombardment mass spectrometry. The glycosyl and elemental composition of all the saponins was determined by applying our(More)
In this study, the chemiluminescent horseradish peroxidase/H(2)O(2)-catalysed oxidation of acridan (GZ-11) substrate was compared with the well-characterized light-producing luminol reaction. p-Iodophenol and p-phenylphenol were used as enhancers, respectively, for the luminol and acridan reactions. These two light-producing systems showed significant(More)
The reactivity of the N-acetoxy metabolite of 2-amino-5-phenylpyridine (Phe-P-1), a pyrolysis product of phenylalanine, towards 2'-deoxyguanosine (dG), 2'-deoxyguanosine-3'-monophosphate (dGMP) and DNA was studied and compared with that of the ortho-methyl derivative. Reaction of 2-acetoxyamino-5-phenylpyridine (N-OAc-APP) with dG resulted in substitution(More)