B van Wickern's research while affiliated with University of Hamburg and other places

Publications (8)

Article
The radiation induced products of tryptophan (TRP) were determined in gamma-irradiated egg white, chicken meat and shrimps using RP-HPLC and electrochemical detection. A two-step hydrolysis with proteinase K and carboxypeptidase A was developed to release the radiation products from egg white and chicken meat and with proteinase K and pronase E fro...
Article
 The products of γ-irradiation of tripeptides (AWA, LWL, LWM) and lysozyme were determined by HPLC and UV/fluorescence detection. A fast and simple one-step hydrolysis with pronase E (30 – 60 min, 40°C) was developed to release the radiation products, without damage, from the peptide chain. N-Formylkynurenine (NFK), oxindolylalanine (OIA), 4-, 5-,...
Article
A HPLC method with UV and fluorescence detection was developed to determine γ-radiation induced products in aqueous solutions of tryptophan. Therefore 4-, 6- and 7-hydroxytryptophan were synthesized in purities which allow their use as reference substances for analytical studies. Oxindolylalanine, N-formylkynurenine, 4-, 5, 6- and 7-hydroxytryptoph...
Article
The products of γ-irradiation of tripeptides (AWA, LWL, LWM) and lysozyme were determined by HPLC and UV/fluorescence detection. A fast and simple one-step hydrolysis with pronase E (30-60 min, 40°C) was developed to release the radiation products, without damage, from the peptide chain. N-Formylkynurenine (NFK), oxindolylalanine (OIA), 4-, 5-, 6-...
Article
The epidemic outbreak of a new disease, the eosinophilia-myalgia syndrome (EMS), was traced back to the intake of L-tryptophan (Trp) of certain lots from a single manufacturer. Since some trace contaminants were related to EMS, it appeared to be necessary to identify and find the origin of most trace contaminants in the EMS related Trp in order to...
Article
Tryptophan oxidation products were determined in pronase E digests of apo B of delipidated, native and Cu2+ oxidized LDL using a sensitive and specific HPLC method. Oxidized LDL contained N-formylkynurenine, kynurenine and tryptamine but no oxindolylalanine and 5-hydroxytryptophan. N-Formylkynurenine increased from an initial value of 0.21 to 1.67...
Article
Conservation of food by ionizing radiation has become legally accepted in 37 countries of the world. Although some methods for the identificaton of irradiated food have been developed, there is a deficit in the detection of the irradiation in food with a high protein content. Up to now, only a single method based on the detection of o- and m-tyrosi...
Article
Eosinophilia-Myalgia-Syndrome (EMS) has been linked to the ingestion of Tryptophan (Trp) manufactured by a single company containing more than 60 UV-detectable minor contaminants (Belongia et al., 1990). Hill et al. (1993) showed by statistical comparison of case and non-case associated lots that six of these contaminants can be associated with EMS...

Citations

... An alkaline hydrolysis has typically been implemented to partially solve this problem. While most methods use sodium hydroxide for hydrolysis (Bech-Andersen, 1991;Van Wickern et al., 1997;Yust et al., 2004;Zhang et al., 2009), other alkaline compounds, such as lithium hydroxide and barium hydroxide, have also been applied (Hugli and Moore, 1972;Lucas and Sotelo, 1980). Barium hydroxide is currently being used in commercial laboratories according to the ISO-standard for protein hydrolysis (ISO 13904:2005(ISO 13904: , 2005. ...
... Due to the considerable amount of literature regarding the production of yellow degradation products from tryptophan [8,19,20], initial experiments focused on the possible contribution of Trp to the color of the degraded feed, by comparing the complete feed to a version lacking Trp. The presence of Trp in the feed caused a clearly visible increase in browning ( Figure 2A). ...
... Further fluorescence studies shown the presence of a different emission spectrum upon excitation at 380 nm. The signal is compatible with the presence of N-formyl- kynurenine [33]. The peptides obtained by hydrolysis of irradiated solution , for which the amino acid composition of peptides was determined, were screened for the fluorescence signal obtained when an excitation wavelength of 380 nm is used. ...
... In addition, it was shown that Cu, Zn-SOD, when it is oxidatively damaged, releases free copper, which can lead to an increase in the formation of • ОН. The formation of α-tocopheroxyl radicals has been shown to contribute to protein damage in atherosclerotic plaques (Giessauf et al., 1996). ...
... Anthranilic acid (AA), and 5-hydroxytryptophan (5-OH-Trp) were obtained from Merck (Darmstadt, Germany). N-Formylkynurenine (NFK) [18], oxindolylalanine (Oia) [18], dioxindolylalanine (DiOia) [18], 4-, 6-, 7-hydroxytryptophan (4-, 6-, 7-OH-Trp) [19], 3a-hydroxy-1,2,3,3a,8,8a-hexahydropyrroloindole-2-carboxylic acid (earlier-eluting diastereomer, PIC A) [6], 3-phenylaminoalanine (PAA) [20], 1,1'-ethylidenebis-L-tryptophan (EBT) [20], 2-(3-indolylmethyl)-L-tryptophan (IMT) [21], 1,2,3,4-tetrahydro-bcarboline-3-carboxylic acid (THCC), 1-methyl-1,2,3,4-tetrahydrob-carboline-3-carboxylic acid (MTHCC) and 1-(3-indolylmethyl)-1,2,3,4-tetrahydro-b-carboline-3-carboxylic acid (IMTHCC) [22] were synthesized as described previously. Two 2-(2,3-dihydroxy-1-(3-indolyl)-propyl)-L-tryptophan diastereoisomers (dhPIT A and B) are reaction products in a mixture of Trp, indole and D-( R)glycerinaldehyde. ...
... Additionally, the -irradiated Trp solutions showed yellow to brown coloration, probably because of the occurrence of polymerization reactions. 4 -6 Van Wickern et al. 8,9 therefore Ł Correspondence to: Pietro Traldi, CNR ISTM, Corso Stati Uniti 4, I-35127, Padova, Italy. E-mail: pietro.traldi@adr.pd.cnr.it. ...
... The transformation is usually acid-catalysed and takes place at low pH and high temperatures [38]. Highly reactive aldehydes are generated during the fermentation processes, thus tetHβCs may be detected in any biotechnologically derived Trp [39]. In the summary, the first and second groups of contaminants are associated with the process of Trp production using fermentation. ...
... Based on the above results a microbiological method for identifying radiation-processed fish could evolve based on lower susceptibility of irradiated fish to bacterial spoilage (Alur et al., 1991). Kleeberg et al. (2000) proposed a method for the analysis of nonprotein bound tyrosine in common shrimps. The procedure involved the homogenization of fresh shrimps followed by solvent precipitation of the proteins with acetone and measurement of the free o-tyrosine by high-performance liquid chromatography with fluorescence detection. ...