Abstract
Peptides composed of hexaproline and glutamic acid (P6E) or lysine (P6K) as C-terminal units show thermally promoted aggregation, affording vesicle-like assemblies upon heating to 80 °C. The aggregation is analyzed by dynamic light scattering (DLS), with number-averaged diameters of ca. 600 and 300 nm, respectively, for P6E and P6K. NMR studies reveal that upon heating the amount of NMR-visible species is reduced to ca. 50% and that an important conformational change is experienced by the molecules in solution. Circular dichroism (CD) shows that at 20 °C the peptides present a polyproline II (PP-II) conformation which is disorganized upon heating. Scanning electron microscopy for samples which were fast frozen at 80 °C reveals vesicle-like assemblies. Using pyrene as a fluorescence probe, a critical aggregation concentration of ca. 30 μM was estimated for P6E, while that of P6K was above 0.6 mM. The aggregation process is found to be fully reversible and could serve as a basis for development of stimuli responsive carriers.
Highlights
Peptide self-assembly has received increasing interest in the last years due to its relevance in difference biological processes
Hexaproline peptides containing as a C-terminal unit the ionizable amino acids glutamic acid (P6E) or lysine (P6K) were studied in phosphate-buffered water at pH 7 (Scheme 1)
An important conformational change takes place, with the peptides losing their secondary structure according to Circular dichroism (CD)
Summary
Peptide self-assembly has received increasing interest in the last years due to its relevance in difference biological processes. Schematic of the Process of Formation of VesicleLike Assemblies for Peptide P6E helix observed in organic solvents.[13] The aggregation of PP motifs in water has been scarcely studied. Circular dichroism spectroscopy and vibrational circular dichroism (VCD) spectroscopy along with Raman and FTIR methods have been used to investigate the conformation of a model triproline peptide in water.[17] VCD has been used to investigate in detail the conformation of oligoproline peptides (P2−P12) in aqueous solutions.[18,19] A reversible conformational transition from PP-I to PP-II upon heating has been observed for a P12 peptide in n-propanol by CD, and it was associated with the cis−trans isomerization of amide bonds.[20] The transition kinetics and thermodynamics were analyzed. No aggregation process has been reported for unmodified oligoproline peptides, to our knowledge
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
