Istvan Schon

In Vitro Effects of Tp5 Analogs on E-Rosette Formation and Cell Division

AbstractThe effects of seventeen synthetic analogs of thymopentin (TP-5) have been studied in the active and azathioprine-inhibited E-rosette tests.Thymopentin was gradually shortened from the C terminus to peptides and single amino acids. Thymopoietin 32-34 (Arg-Lys-Asp-RGH-0205-TP-3) (II) and thymopoietin 32-35 (Arg-Lys-Asp-Val-RGH-0206-TP-4) (I) were the most active peptides.Dipeptide Arg-Lys produced significant stimulatory effect on azathioprine (ED75) inhibited E-receptor. Treatment of azathioprine (ED75-inhibited E-rosette forming cells (ERFC) with arginine or especially lysine increased the number of ERFC.Some of TP-4 analogs decreased further the number of ERFC decreased by azathioprine ED30. These “suppressive” peptides as well as TP-3 caused a partial arrest of K 562 cell proliferation up to 96 hours.Results suggest that TP-5 is not the smallest active fragment of thymopoietins, since peptides (TP-3 and TP-4) exhibit similar or higher T-cell membrane activation on E-receptor. Arginine, lysine, ...

Unprecedented transformation of aspartyl peptides by conjugative degradation

Simultaneous covalent conjugation and cleavage of aspartyl peptides observed in model experiments may give an explanation of some aggregative phenomena in defective metabolism as well as of decomposition during processing and storage of peptides and proteins.

Synthesis of biotinylated thymocartins

Four biotinylated derivatives of Arg-Lys-Asp-Val immunostimulating tetrapeptide labelled either at the α-amino group of arginyl or the ϵ-amino moiety for lysyl residue have been synthesized for biological studies using classical methods. Copyright

1H-NMR studies on thymopoietin-type oligopeptides — assignment of the proton resonances and investigation of conformational preferences

The thymopoietin-type tripeptides TP3 (HArg-Lys-AspOH), TP(D-Asp)3(HArg-Lys-D-AspOH) and tetrapeptide TP4 (HArg-Lys-Asp-ValOH) were studied by one- and two-dimensional, 500 MHz 1H-NMR spectroscopy in H2O and D2O solutions at four different pH values. All proton resonances of the three oligopeptides were assigned by two-dimensional phase-sensitive TOCSY experiments at pH 12.2, 9.1, 5.9 and 3.6. At these pH-values well-defined stages of protonation and concomitant molecular charges exist, allowing different possibilities for intra-molecular and inter-residual orientations. Conformation-sensitive rotating frame nuclear Overhauser enhancement (ROESY) two-dimensional experiments were also performed at the above pH values. These experiments indicated no definite solution conformation of any of the molecules at any pH. Standard one-dimensional experiments were also carried out and three-bond coupling constants were measured for the NH--CH and the Asp CH--CH moieties. The coupling constants provided evidence that non-statistical orientations of the functional groups exist which are changed upon protonation of the basic sites.