Total synthesis of methionine-enkephalin.
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Amino Acid Sequence↗
Biomedical subjects
H Kalbacher
Publications and source records attributed to H Kalbacher.
[Synthesis and spectroscopic investigation of Namide-ethylthyroliberin (author's transl)].
A synthesis of Namide-ethylthroliberin is described. The structure of this analog of thyroliberin is proved by elemental analysis, mass spectrometry and circular dichroism. It shows, compared to the natural hormone still considerable thyrotropin-releasing activity.
Biological Assay↗
Molecular parameters in melittin immunogenicity.
Based on immunogenicity studies, two T-cell epitopes in melittin were found to be functional in guinea pigs, one being centrally located, the other one residing in the C-terminal chain. In Balb/c mice only the central epitope was found to be active. A human T-cell clone was found by T-cell proliferation studies to employ strictly the C-terminal chain. Truncation of melittin peptides at the N-terminus did not markedly affect the capacity of guinea pigs to develop anti-IgG responses towards peptidic epitopes and towards a C-terminally attached haptenic group. Attachment of various substituents inside and outside the T-cell epitopic areas had no marked effect on antibody responses. In contrast, the substituents positioned within a T-cell epitope abolished T-cell proliferation. This difference between whole animal data and cellular in vitro responses is presently not understood.
Amino Acid Sequence↗
Presentation of insulin and insulin A chain peptides to mouse T cells: involvement of cysteine residues.
The requirements for insulin presentation and recognition by A alpha b A beta b- and A alpha b A beta k-restricted mouse T cells were studied using a variety of derivatives of the insulin A chain. It was found that A chain peptides with irreversibly blocked Cys residues are non-stimulatory for the T cells. This suggests that at least one of the Cys residues is essential for recognition. On the other hand, all A chain peptides containing Cys residues modified in a way reversible by reaction with thiols are stimulatory yet differ in antigenic potency. All these A chain derivatives including a 14 amino acid fragment require uptake by antigen presenting cells (APC) for efficient presentation. Differences in stimulatory potency between the A chain peptides derived from the same insulin appear to be mainly due to the efficiency of uptake and/or processing by APC. Based on these findings we propose that processing in the case of insulin and its A chain derivatives involves the reductive deblocking of Cys residues or the rearrangement of disulfide bonds apart from a possible proteolytic cleavage. The same may apply to other proteins if Cys residues in the presented peptides are important for the interaction with Ia or the T cell receptor.
Animals↗