Hemolysis peptides

In another study, the carrier protein was replaced by an enzyme compatible solid-phase resin (PEGA), and enzyme-catalyzed cyclization was used to probe substrate specificity. This study demonstrated also that oxo-esters are tolerated as substrates for TE domains, and then-preparation in library format served as an excellent tool for substrate specificity studies, as well as for preparation of cyclized peptides. Figure 13.11 shows how the TycA TE showed selectivity for only residues 1 and 9 (colored in red), and changes at all other residues were tolerated [42]. Hydrogen bonding interactions are shown in green. Several compounds made from this series were shown to demonstrate improved therapeutic indices (with respect to hemolysis) while retaining antimicrobial activity. 

Hemopexin was first identified as a heme binding P-globin in elec-trophoretograms of plasma of patients with hemolysis (17-19). The protein is synthesized and secreted by the liver (20-22), and during secretion the signal peptide is removed and the protein is glycosylated (23). Tissue forms of hemopexin are expected due to the presence of mRNA in brain (24), peripheral neurons (25), and neural retina (26), pointing to a function of hemopexin in barrier tissues. 

Since the YTX molecule has a hydrophobic polyether skeleton, some hemolytic activity could be expected. However, the toxin did not induce hemolysis [3], Even an important hemolytic property was described to desulfated YTX by interacting with alfa-helix membrane peptides [20],... 

All hemolysis results that are reported in this work were obtained using freshly drawn blood from one individual. During the course of this study, the hemolytic activities of polymers were observed to be dependent on the freshness of the blood. Differences were also noted for blood obtained from different individuals. It was determined that blood stored for more than 7 d was more susceptible to hemolysis than freshly drawn blood. These observations were in accordance with previous literature that reported higher susceptibility to hemolysis, caused by a series of cationic antimicrobial peptides, in the case of blood stored for 21 d in 4 C, as opposed to fresh blood (72). Non-hemolytic polymers, dep-poly6, and dep-polylO remained non-hemolytic against old blood that was stored for 3 weeks at 4 °C, and blood from different individuals, with HC50 values above 4000 pg/mL. 

Osorio e Castro, V. R., Ashwood, E. R., Wood, S. G. and Vernon, L. R, 1990, Hemolysis of erythrocytes and fluorescence polarization changes elicited by peptide toxins, aliphatic alcohols, related glycols and benzylidene derivatives, Biochim. Biophys. Acta, 1029 252. 

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