RESUMO
A mathematical procedure was developed to predict the partition coefficients of the peptides AIIP, AWWP, AIIPAIIP and AWWPAWWP in poly(ethylene glycol) (PEG)/phosphate aqueous two-phase systems from amino acid hydrophobicities. In general, peptides containing tryptophan partition more into the PEG-enriched upper phase than analogous peptides containing isoleucine. Specifically, as the PEG concentration difference between the phases increased in a PEG/potassium phosphate aqueous two-phase system, the peptide AIIP was observed to have a partition coefficient ranging from 1.2 to 1.6, AIIPAIIP from 2.4 to 5.7, AWWP from 13.5 to 32.2, and AWWPAWWP from 43 to 170. The model was extended to predict the partitioning of a staphylococcal protein A derivative (ZZ) modified with these four peptides. As predicted, the protein modified with isoleucine-containing peptides had lower partition coefficients than the protein modified with tryptophan-containing peptides. The partition coefficient of the ZZ protein ranged from 0.35 to 0.20, that of ZZAIIPAIIP from 0.58 to 0.48, and that of ZZAWWPAWWP from 3.5 to 5.3 in these systems. The results show that short peptide handles can significantly enhance the partitioning of proteins in aqueous two-phase systems. The relationship between the model and the surface exposure of peptide handles and the utility of the model to aid in the design of such handles to enhance purifications are also discussed.
Assuntos
Modelos Químicos , Oligopeptídeos/química , Oligopeptídeos/isolamento & purificação , Sequência de Aminoácidos , Sítios de Ligação , Fenômenos Químicos , Físico-Química , Concentração de Íons de Hidrogênio , Imunoglobulina G/metabolismo , Ponto Isoelétrico , Matemática , Dados de Sequência Molecular , Proteína Estafilocócica A/química , ÁguaRESUMO
Two different tetrapeptides, AlaTrpTrpPro and AlaIleIlePro, were inserted near the C-terminus of the protein ZZT0. The Trp-rich peptide unit strongly increased both the partitioning of ZZT0 into the polyethylene glycol (PEG)-rich phase in a PEG-potassium phosphate aqueous two-phase system and its retention on PEG and propyl hydrophobic interaction chromatographic columns with potassium phosphate as eluent. Both the partitioning and the retention increased with increasing number of Trp-rich peptide units inserted into ZZT0. Insertion of Ile-rich tetrapeptide units affected the partitioning and retention to a much lesser extent. Partition data also indicated a folding of inserted Trp tetrapeptides units, probably to minimize their water contact.
