PEGylation Site-Dependent Structural Heterogeneity Study of MonoPEGylated Human Parathyroid Hormone Fragment hPTH(1–34)

• Published in: Langmuir 2014-09, Vol.30 (38), p.11421-11427
• Main Authors: Liu, Chih-Ying, Li, Xin, Chen, Wen-Yih, Chang, Li-Chiao, Chen, Yi-Fan, Chen, Hsin-Lung, Sun, Ya-Sen, Lai, Hsiu-Yun, Huang, E-Wen
• Format: Article
• Language: English
• Subjects: Humans; Molecular Structure; Polyethylene Glycols - chemistry; Teriparatide - chemistry
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la501689d

The structures of C- and N-terminally monoPEGylated human parathyroid hormone fragment hPTH(1–34) as well as their unmodified counterparts, poly­(ethylene glycol) (PEG) and hPTH(1–34), have been studied by small-angle neutron scattering (SANS). The scattering results show that free hPTH(1–34) in 100 mM phosphate buffer (pH 7.4) aggregates into clusters. After conjugation with PEG, the PEG–peptide conjugates self-assemble into a supramolecular core–shell structure with a cylindrical shape. The PEG chains form a shell around the hPTH­(1–34) core to shield hPTH(1–34) from the solvent. The detailed structural information on the self-assembled structures is extracted from SANS using a model of the cylindrical core with a shell of Gaussian chains attached to the core surface. On the basis of the data, because of the charge–dipole interactions between the conjugated PEG chain and the peptide, the conjugated PEG chain forms a more collapsed conformation compared to free PEG. Moreover, the size of the self-assembled structures formed by the C-terminally monoPEGylated hPTH­(1–34) is about 3 times larger than that of the N-terminally monoPEGylated hPTH(1–34). The different aggregation numbers of the self-assembled structures, triggered by different PEGylation sites, are reported. These size discrepancies because of different PEGylation sites could potentially affect the pharmacokinetics of the hPTH(1–34) drug.