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Quantitative considerations supporting the irrelevance of circulating serum CEA for the immunoscintigraphic visualization of CEA expressing carcinomas (1988)

Bosslet, K. ; Steinsträsser, A. ; Schwarz, A. ; [et al.]

Springer

European journal of nuclear medicine 14 (1988), S. 523-528

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ISSN: 1619-7089

Keywords: CEA ; Conformational change ; MAb ; Immunoscintigraphy

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Abstract Starting from the phenomenon that the amount of circulating CEA in patients' sera did not significantly influence immunoscintigraphic visualization of CEA expressing tumors, we built up an in vitro model to explain this phenomenon. Blocking experiments in this model system showed that the CEA specific MAbs BW 431/26 and BW 431/31 could not be inhibited in their binding to cell associated CEA, if they were preincubated with a 20 molar excess of serum CEA. In contrast, the CEA-NCA cross reactive MAbs could be inhibited in their binding to tumor associated CEA under identical conditions. These data combined with western blotting analysis of patients' sera and affinity constant determinations argue that conformational changes in serum CEA cause a decreased affinity of the CEA specific MAbs to serum CEA allowing a preferential binding to tumor associated CEA.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00286769

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A two-step enzymatic synthesis of dipeptides (1992)

Schwarz, A. ; Wandrey, C. ; Steinke, D. ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 39 (1992), S. 132-140

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ISSN: 0006-3592

Keywords: enzymatic synthesis ; continuous production ; anion-exchange ; peptide-amidase ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology

Notes: A simple system is introduced to produce dipeptides continuously by enzyme catalyzed condensation of amino acid esters and amino acid amides. Synthesis of N-terminal free dipeptide-amides is achieved by means of carboxypeptidase Y. The peptide-amide is deamidated utilizing a newly isolated peptide-amide is deamidated utilizing a newly isolated peptide-amidase. Separation of substrates and products is accomplished by anion-exchange chromatography. Modeling of the reactions shows that the two reactions have to be carried out in a cascade of two reactors in order to prevent hydrolysis of the peptide by the carboxypeptidase. Continuous production of Kyotorphin (H-TyrArg-OH) with a space-time yield of 257 g/L · d shows the feasibility of this concept.

Additional Material: 9 Ill.