Disulfide bridge, peptides and

Momany, F. A., R. Rone, H. Kunz, R. F. Frey, S. Q. Newton, and L. Schafer. 1993. Geometry Optimization, Energetics and Solvation Studies on Four- and Five-mem-bered Cyclic and Disulfide-bridged Peptides, Using the Programs QUANTA3.3 and CHARMm 22. J. Mol. Struct. 286, 1-18. 

Oxidation of mono-cysteine peptides to the dimer is a straightforward reaction that can produce only the desired product. In the case of bis-cysteine peptides statistically the oxidation leads to the homodimers in parallel and antiparallel orientation as well as to the disulfide-bridged monomer and oligomers. When the two cysteine residues are placed in the adjacent position formation of homodimers is highly favored over the cyclic monomer (Section 6.1.5.1) and the product distribution depends strongly on the peptide concentration. Such a type of intermolecular disulfide bridging is present in bovine seminal ribonuclease, where an antiparallel alignment occurs at the interface of the dimer. 97 ... 

Cys(StBu) with phosphines only a slight excess of tributylphosphine is required for this purpose. Under these conditions reduction of the diselenide does not occur at all, and subsequent air oxidation of the two cysteine residues at high dilution leads in a highly selective manner to the diselenide- and disulfide-bridged peptides. The selectivity of the disulfide bridging is assured by the complete absence of thiol/diselenide exchange reactions even at alkaline pH values due to the very low reactivity of the diselenide toward mono-thiols as a result of their highly differentiated redox potentials. ... 

The same enzymatic cleavage can then be applied to the unreduced enzyme. Pairs of peptide fragments remain linked by the S-S bridges. These crosslinked pairs can be separated, the disulfide bridges cleaved, and the resulting peptides identified, each as one of the already sequenced fragments. Mass spectrometry provides a rapid method for their identification.258... 

Scheme 56 Intrahelical Disulfide-Bridged Peptide 197 and Thiol Amino Acids 198I1081...

With the methods already described above, disulfide-bridged antiparallel and parallel two-stranded peptides can be prepared. The question arises which peptides are stable under benign conditions. The best way to test for specificity of interaction for the parallel or antiparallel orientation is to place the peptides in a redox buffer with various additives to determine if there is specificity and what interactions are driving the specificity. 

A. Jacobi, D. Seebach, How to Stabilize or Break P-Peptidic Helices by Disulfide Bridges Synthesis and CD Investigation of P-Peptides with Cysteine and Homocysteine Side Chains Helv. Chim. Acta 1999, 82, 1150- 1172. 

Step 1 Protein work-up Protein identification Protein isolation Biological property description Protein structure work-up - amino acid sequencing and mapping, glycosylation, disulfide bridging, peptide domains... 

Spider venom peptides, toxic peptides from spiders that mainly modulate neurotransmission. Spider venoms are rich in neurotoxins that influence ion channels, interfere with neurotransmitter exocytosis, or affect neurotransmitter binding. The most important families are the atracotoxins (36-68 amino acids) and the latrotoxins. Many spider venom peptides are translated as prepropeptides and post-translationally modified, e.g., by disulfide bridge formation and C- or N-terminal modification. Because of the high diversity of its constituents, the spider venom is sometimes regarded as a biogenic structurally constrained combinatorial peptide library where nearly all amino acids of the mature sequence may be mutated, with the exception of a few strictly conserved cysteine residues responsible for the three-dimensional fold of the toxin [G. Estrada etal, Nat. Prod. Rep. 2007, 24,145]. 

Flexibilities of Some Polypeptide Helices and Disulfide Bridged Peptides" in Conformation in Biology,... 

Reduction of Disulfide Bonds The disulfide-bridged peptides can also be identified by analyzing the protein digest before and after the dithiothreitol reduction of disulfide bonds. The peaks due to disulfide-containing peptides will disappear, and new peaks related to reduced peptides will appear. If the peptide... 

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