Pegylation, sites

FIGURE 12 Primary structure of salmon calcitonin. Possible PEGylated sites are Cys1, Lys11, and Lys18. (Reproduced from ref. 79 with permission of Taylor Francis.)... 

Na and Lee reported on the characterization of PEGylated human parathyroid hormone (PEG-PTH) using CZE [136]. As shown in Figure 5.1-12, the CZE was used to optimize reaction conditions by monitoring the effects of reaction pH and the molar ratios of reactants on the PEGylation of PTH. The CZE method also allowed for determination of the extent of positional isomers in mono-PEG-PTH as well as for the identification of PEGylation sites. 

Identification of PEGylation sites in mono-PEG-human CZE 100-mM sodium phosphate (pH 2.5) Polyacrylam ide-coated UV (200nm) [136]... 

Fig. 7 Use of PEG - Met - Nle - OSu or PEG-Met- SAla-OSu to introduce a reporter amino acid at the PEGylation site PEG conjugation followed by polymer moiety release by BrCN leaves Nle or )0Ala, which can be identified on the protein by amino acid sequence analysis...

EM. Veronese, B. Sacca, P. Polverino de Laureto, M. Sergi, P. Cahceti, O. Schiavon, P. Orsolini, New PEGs for peptide and protein modification, suitable for identification of the PEGylation site. Bioconjugate Chem., 12 (1) 62-70. 

S. Jung, S.H. Lee, H. Mok, H.J. Chimg, T.G. Park, Gene silencing efficiency of siRNA-PEG conjugates effect of PEGylation site and PEG molecular weight. J. Control. Release, 144 (3) 306-313, 2010. 

Fig. 3 Chemistry of site-specific PEGylation developed by Brocchini et al. [5, 6]. After cleavage of the native disulfide bond between two cysteine thiols by reduction, the free cysteines are reacted with an a, (3-unsaturated PEG derivative to produce a PEG conjugate via a three-carbon bridge...

Fig. 4 PEGylation at the N-terminal methionine residue. The difference in pKa. between the N-terminal amine and other amines in the protein enables site-specific PEGylation. After reaction with aldehyde-terminated PEG at low pH, reduction of the resultant imine produces PEGylated protein...

Fig. 5 Enzymatic site-specific PEGylation by transglutaminase (TGase). The alkylamine derivative of PEG can be introduced into proteins in a site-specific manner...

The concept of de-PEGylation can be applied to the development of nanoparticle-based drug delivery systems. PEG is used for the modification of liposomes to increase their blood circulation time [38], However, it also prevents cellular uptake, resulting in a decrease in therapeutic efficiency thus, modifications of the liposome surface with PEG interfere with membrane fusion to the cell membrane and liposome decomposition [39]. One of the possible strategies to solve this problem is to cleave the PEG chains after the nanoparticle reaches the target site (Fig. 9). This system of de-PEGylation of liposomes is also useful in avoiding the immune... 

Lee H, Jang IH, Ryu SH, Park TG (2003) N-terminal site-specific mono-PEGylation of epidermal growth factor. Pharm Res 20 818-825... 

Sato H (2002) Enzymatic procedure for site-specific pegylation of proteins. Adv Drug Deliv Rev 54 487-504... 

Fontana A, Spolaore B, Mero A, Veronese FM (2008) Site-specific modification and PEGylation of pharmaceutical proteins mediated by transglutaminase. Adv Dmg Deliv Rev... 

Goodson, R.J., and Katre, N.V. (1990) Site-directed pegylation of recombinant interleukin-2 at its glyco-sylation site. Bio/Technology 8, 343-346. 

Ferrying of molecules into cells via entry through caveolae may represent a way to traffic specifically cytotoxic molecules to specific action sites. For example, elevating the intracellular level of the sphingolipid ceramide is known to exert antimitogenic and proapoptotic effects. While ceramide is cell-permeable and displays antiapoptotic properties in vitro, systemic in vivo use of ceramide is hampered by its hydrophobicity. Using a C6-ceramide formulation in pegylated liposomes was shown to elicit a sixfold reduction in solid phase tumors, when compared to unloaded liposomes in a mouse model of breast adenocarcinoma [68],... 

Solvents are no longer needed and the albumin passes into the body. More pertinent examples include the pegylated interferons (31). Polyethylene glycol (PEG) is attached in a random fashion and at variable numbers of sites on each molecule. A single dose of the combination in each cycle of chemotherapy is as effective as the original version, which required daily injections for up to two weeks. The PEG... 

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