Dipeptides aggregation

To prevent insolubility resulting from uncontrolled aggregation of extended strands, two adjacent parallel or antiparallel yS-peptide strands can be connected with an appropriate turn segment to form a hairpin. The / -hairpin motif is a functionally important secondary structural element in proteins which has also been used extensively to form stable and soluble a-peptide y9-sheet arrangements in model systems (for reviews, see [1, 4, 5] and references therein). The need for stable turns that can bring the peptide strands into a defined orientation is thus a prerequisite for hairpin formation. For example, type F or II" turns formed by D-Pro-Gly and Asn-Gly dipeptide sequences have been found to promote tight a-pep-tide hairpin folding in aqueous solution. Similarly, various connectors have been... 

Both cyclic dipeptides at all screening concentrations were found to significantly enhance ADP-induced platelet aggregation (P< 0.0001) with cyclo(Gly-Thr) demonstrating greater platelet aggregation activity over cyclo(Gly-Ser). 

Y. Murakami, A. Nakano, H. Ikeda, T. Imori, K. Akiyoshi, Aggregation Behavior of Amphiphiles Functionalized with Dipeptide Segments and Enantioselective Ester Hydrolysis in Their Bilayer Membranes , Bull. Chem. Soc. Jpn., 58,172 (1985)... 

Carnosine is an endogenous dipeptide present in the CNS, with multi-protective homeostatic functions, acting as an intracellular pH buffering molecule, Zn/Cu ion chelator, antioxidant, and anti-crosslinking agent. Carnosine is effective against A(f aggregation [578, 579],... 

C, Rinaldi R et al (2013) Anti-aggregating effect of the naturally occurring dipeptide car-nosine on a(31-42 fibril formation. PLoS One 8 e68159. doi 10.1371/journal. 

Cyclic dipeptides, especially cyclo[(S)-phenylalanyl-(S)-histidyl], are efficient and selective catalysts for the hydrocyanation of aromatic aldehydes (Fig. 5) [41]. The catalysts are not available commercially but can be synthesized by conventional methods and their structure can be varied easily (Fig. 5) [41,42,43]. The catalysts are only selective in a particular heterogeneous state, described as a clear gel [41,43]. It seems that their method of precipitation is crucial [41,44] and that reproducing literature results is not always easy [42]. A recent study confirmed the importance of the aggregate formation and reported a second order rate dependence on the concentration of the cyclic dipeptide [45]. These findings indicate that the enantioselective catalytic species is not monomeric but either a dimer or polymer. 

Figure 2 Synthesis of bio-hybrid amphiphiies by radicai addition of cysteine-based dipeptides onto poly(1,2-butadiene)-Woc/(-poly(ethylene oxide)s and fiuorescence microscopy images of seif-assembied aggregates in aqueous soiution. Reprinted with permission from Geng, Y. Discher, D. E. Justynska, J. Schiaad, H. Angew. Chem., Int. Ed. 2006, 45, 7578 and Lutz, J.-F. Schiaad, H. Polymer2006, 49, 817. Copyright 2008, Elsevier. ...

James, J. Mandal, A. B. Micelle Formation of Tyr-Phe Dipeptide and Val-Tyr-Val Tiip>eptide in Aqueous solution and their Influence on the Aggregation of SDS and PEO-PPO-PEO Copolymer Micelles. Colloid Surf B, 2011, 84,172-180. 

Acrasin an attractant secreted by aggregation centers of slime molds, which stimulates single cells to aggregate and form fruiting bodies. The A. of Dictos-lelium is cyclic AMP (see), which attests to the antiquity of this substance as a hormone. The A. of Poly-sphondium violaceum is a dipeptide called glorin ... 

With peptides that have become aggregated it is frequently not possible to obtain complete reaction, even after carrying out multiple acylation reactions. In such cases it is often necessary to repeat the synthesis, incorporating an Hmb-protected residue (Chapter 5) or an oxazolidine-dipeptide (26-28) two to four residues before the region prone to aggregation. 

Another example where aggregation of a library member drives its synthesis was recently reported by Ulijn ct al. [24, 25]. They used reversible amide bond formation, mediated by thermolysin, which is an enzyme that can catalyze both amide bond hydrolysis and formation, and is only moderately peptide-sequence-dependent. The authors reported that starting from dipeptides and fluorenyl-protected amino acids, the action of thermolysin gives rise to a dynamic mixture of peptides of different lengths (containing typically one to five amino acid residues). When using phenylalanine or leucine as the starting amino acids the... 

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