1. pH-Responsive Biocompatible Supramolecular Peptide Hydrogel
Goutam Ghosh, Ranajit Barman, Jayita Sarkar, Suhrit Ghosh J Phys Chem B. 2019 Jul 11;123(27):5909-5915. doi: 10.1021/acs.jpcb.9b02999. Epub 2019 Jun 27.
Peptide-based hydrogels are highly promising for various biomedical applications owing to their precise self-assembly, biocompatibility, and sensitivity toward biologically relevant external stimuli. Herein, we report pH-responsive self-assembly and gelation of a highly biocompatible amphiphilic peptide PEP-1. This is an octa-peptide and double mutant of a naturally occurring β-strand peptide fragment of the protein Galectin-1, available in bovine spleen. PEP-1 was synthesized by using the Rink amide resin as the solid support in a homemade apparatus. At pH 7.4, it exhibits spontaneous gelation with very high yield stress of 88.0 Pa and gel-to-sol temperature of 84 °C at C = 2.0 wt %. Microscopy studies revealed entangled fibrillar morphology whereas circular dichroism, Fourier tranform IR, and Thioflavin T assay indicated formation of β-sheet rich secondary structure. The assembled state was found to be stable in neutral pH whereas either decrease or increase in the pH resulted in disassembly owing to the presence of the pH responsive Asp and Lys residues. The gel network showed ability to entrap water-soluble guest molecules such as Calcein which could be selectively released at acidic pH whereas under neutral condition the release was negligible. MTT assay revealed remarkable biocompatibility of the PEP-1 gel as almost 100% cells were alive after 48 h incubation in the presence of PEP-1 (2.0 mg/mL).
2. Fragment synthesis of disulfide-containing peptides
Yuxuan Dai, Na Yue, Wenlong Huang, Hai Qian MethodsX. 2020 Jun 4;7:100945. doi: 10.1016/j.mex.2020.100945. eCollection 2020.
A new strategy for solid phase peptide synthesis in the fragment synthesis based on the use of 2-Cl-trityl resin as carrier to obtain protected peptide-resin and Rink Amide Resin, HOBT/HBTU or PyBOP/DIPEA or HATU/DIPEA as the coupling method is described. The highlights of this method are:·Simple.·Low cost.·Solid phase based.
3. C-terminal N-alkylated peptide amides resulting from the linker decomposition of the Rink amide resin: a new cleavage mixture prevents their formation
Panagiotis Stathopoulos, Serafim Papas, Vassilios Tsikaris J Pept Sci. 2006 Mar;12(3):227-32. doi: 10.1002/psc.706.
Decomposition of the resin linkers during TFA cleavage of the peptides in the Fmoc strategy leads to alkylation of sensitive amino acids. The C-terminal amide alkylation, reported for the first time, is shown to be a major problem in peptide amides synthesized on the Rink amide resin. This side reaction occurs as a result of the Rink amide linker decomposition under TFA treatment of the peptide resin. The use of 1,3-dimethoxybenzene in a cleavage cocktail prevents almost quantitatively formation of C-terminal N-alkylated peptide amides. Oxidized by-product in the tested Cys- and Met-containing peptides were not observed, even if thiols were not used in the cleavage mixture.