1. Rapidly Recoverable Thixotropic Hydrogels from the Racemate of Chiral OFm Monosubstituted Cyclo(Glu-Glu) Derivatives
Lu Wang, Xin Jin, Lin Ye, Ai-Ying Zhang, Deon Bezuidenhout, Zeng-Guo Feng Langmuir. 2017 Dec 5;33(48):13821-13827. doi: 10.1021/acs.langmuir.7b03527. Epub 2017 Nov 22.
Both chiral OFm monosubstituted cyclo(l-Glu-l-Glu) and cyclo(d-Glu-d-Glu) display a robust gelation ability in a variety of organic solvents and water. In contrast to an individual enantiomer, their racemate can form rapidly recoverable thixotropic hydrogels with a remarkably shorter thixotropic recovery time. This unexpected thixotropic behavior is induced by the random arrangement of d- and l-enantiomers in the cell units, leading to the formation of "pseudoracemate", noncrystalline self-assemblies in the resulting 3D fibrous network.
2. Synthesis and interaction with metal ions of cyclic oligopeptides bearing carboxyl groups
Y Fusaoka, E Ozeki, S Kimura, Y Imanishi Int J Pept Protein Res. 1989 Aug;34(2):104-10. doi: 10.1111/j.1399-3011.1989.tb01497.x.
Cyclic di- and tetrapeptides bearing carboxyl or carboxylate groups, cyclo[Glu(OBzl)-Glu(OMe)], cyclo[Glu-Glu(OMe)], cyclo(Glu-Glu), cyclo[Glu(OMe)-Pro)2, and cyclo(Glu-Pro)2, were synthesized and investigated on the intramolecular interaction of carboxyl side chains in the complexation with metal ions in relation with the conformation. The three kinds of cyclic dipeptides were found to take a flagpole boat conformation. Folded conformation of side chains was predominant for cyclo[Glu(OBzl)-Glu(OMe)] and cyclo[Glu-Glu(OMe)]. However, cyclo(Glu-Glu) took an unfolded conformation. Intramolecular interaction of carboxyl groups was observed neither in free state nor in complexation with metal ions. The intramolecular interaction of carboxyl groups was observed in the case of cyclo(Glu-Pro)2 in the absence of metal ions added. Cyclo[Glu(OMe)-Pro]2 and cyclo(Glu-Pro)2 formed a complex with Ca2+ and Ba2+ without participation of side chains.
