title: The effect of palmitoylation on the conformation and physical stability of a model peptide hormone.
abstract: Peptides are ideal drug candidates due to their potency and specificity, but suffer from a short half-life and low membrane permeability. Acylation can overcome these limitations but the consequences to stability under different formulation conditions and stresses are largely unreported. Using synchrotron radiation circular dichroism (SRCD), we show that palmitoylation of a 28 amino acid peptide hormone (pI 9.82) induced a structural transition from 310-helix to α-helix, irrespective of buffer type and pH investigated (5.5-8.0) when compared to the non acylated analogues. These conformational preferences were retained in the presence of non-ionic micelles but not anionic micelles, which induced an α-helical structure for all peptides. Palmitoylation promoted an irreversible peptide denaturation under thermal stress at pH ≥ 6.5 and increased the propensity for loss of helical structure under high photon flux (here used as a novel accelerated photostability test). The presence of either ionic or non-ionic micelles did not recover these conformational changes over the same irradiation period. These results demonstrate that acylation can change peptide conformation and decrease thermal-/photo-stability, with important consequences for drug-development strategies.
authors.affiliation: Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom.
authors.forename: Edoardo
authors.initials: E
authors.lastname: Longo
authors.affiliation: Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom.
authors.forename: Emiliana De
authors.initials: ED
authors.lastname: Santis
authors.affiliation: Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom. Electronic address: rohanah.hussain@diamond.ac.uk.
authors.forename: Rohanah
authors.initials: R
authors.lastname: Hussain
authors.affiliation: MedImmune Ltd., Formulation Sciences, Granta Park, Cambridge CB21 6GH, United Kingdom.
authors.forename: Christopher F
authors.initials: CF
authors.lastname: van der Walle
authors.affiliation: MedImmune LLC, Analytical Biochemistry, Gaithersburg, MD 20878, USA.
authors.forename: Jose
authors.initials: J
authors.lastname: Casas-Finet
authors.affiliation: MedImmune Ltd., Formulation Sciences, Granta Park, Cambridge CB21 6GH, United Kingdom.
authors.forename: Shahid
authors.initials: S
authors.lastname: Uddin
authors.affiliation: MedImmune Ltd., Formulation Sciences, Granta Park, Cambridge CB21 6GH, United Kingdom.
authors.forename: Ana Dos
authors.initials: AD
authors.lastname: Santos
authors.affiliation: Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom.
authors.forename: Giuliano
authors.initials: G
authors.lastname: Siligardi
mesh_terms: D002942:Circular Dichroism; D004355:Drug Stability; D054878:Lipoylation; D036361:Peptide Hormones / Q000737:chemistry*; D011487:Protein Conformation
chemical_list: D036361:Peptide Hormones
keywords: Accelerated stability studies; Circular dichroism; Conformation; Drug development; Photo-degradation; Vasoactive intestinal peptide