Peptide bridge, effect

Interestingly, one can use a Cys-Gly-Gly linker at the N- or C-terminal of the polypeptide chain in the design of disulfide-bridged coiled coils. The advantage of this approach is that the Cys-Gly-Gly linker allows complete flexibility of the polypeptide chains to adopt their most stable conformation, which includes different oligomerization states, while maintaining the polypeptide chains in a parallel manner. 49 In addition, the Cys-Gly-Gly linker eliminates the monomer-dimer equilibrium and the peptide concentration effect on stability, which is observed in two-stranded coiled-coil formation of noncovalent linked polypeptides. 49 861... 

The effects of different types of electron distribution are of much interest. The most effective bridges, i.e., those with the smallest values of f) (0.14—0.56 A ), are those in which the bridging group contains mainly tt-orbitals. Correspondingly, theoretical molecular-orbital treatments by extended Hiickel methods indicate that aromatic or polyene bridges should be better conductors than purely aliphatic ones (cf. Section 9.2.2.5 below) [27], Peptide bridges, made up of a combination of saturated and unsaturated units, provide a fairly good medium (P 0.7 A ) and likewise proteins = 0.7—1.0 A ). A weak dependence of p on the ionization potential of D has been noted [28]. All this evidence links conduction properties with other indications of electronic mobility. 

The effect of C ,C -disubstituted amino acids (aaAAs) on peptide secondary structure has been studied in recent years.2a d While longer side-chain C ,C -di-n-alkyl amino acids promote extended peptide conformation,23 alicyclic aaAAs, in which the Ca carbon forms a cyclic bridge with itself, such a 1-aminocyclopentane-l-carboxylic acid (Ac5c) and 1-aminocyclohexane-l-carboxylic acid (Ac6c), have helix-forming characteristics similar to those of 1 -aminoisobutyric acid (Aib).2ax... 

Fig. 2.16 Effect of electrostatic interactions on 3i4-helix formation in an aqueous environment [1 75 a, 175 b, 176]. y -Peptides 86 and 87 adopt a stable helical conformation mediated by salt bridges near neutral pH. While the propensity of these peptides to adopt a helical conformation is strongly de-...

Vasopressin is closely related to oxytocin and both peptides are cyclic in that they contain a disulphide bridge. Although much is known about the peripheral actions of the peptides the extent of our current knowledge of their possible CNS function is that vasopressin appears to act as a cognitive enhancer and has positive effects on learning processes in animals. Vasopressin acts on three receptors, Via and b and a V2 receptor. 

Physiologists had postulated for a long time about the existence of a sodium excreting hormone to prevent Na overload and consequent deleterious effects of high blood pressure on the heart and vascular system. At least two such natriuretic factors have been described atrial or A-type and brain or B-type natriuretic factors. Structurally, the natriuretic factors are peptides with a cysteine-cysteine disulfide bridge creating a characteristic loop , this is illustrated by Figure 8.8. 

The innate and the adaptive arms of the immune systems of higher organisms are bridged by a complex set of cellular and molecular mediators. The immunomodulatory activities of host defense peptides, such as the direct chemotactic activity, cytokine and chemokine induction, and the stimulation of differentiation and activation of effector cells, may contribute to this process. Host defense peptides may also influence the polarization of adaptive immune response, for example, through their effects on cytokine production. ... 

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