Glycosylation is an ubiquitous posttranslational modification of biomolecules, such as proteins and lipids. The ability of the same protein to exert different biofunctions depends on its glycosylation that can alter the protein conformation and/or present different bioscripts.1,2 Here, we used a glycopeptide reducionist model to investigate the effect of the carbohydrate stereochemistry on the assembled supramolecular structure. The model is composed by L- or D-glucosamine bound to an aromatic portion (Fmoc) representing any biomolecule that is involved in the CH-p interactions. We studied the assembly of these amphiphiles at different energy inputs, mimicking different cellular states (e.g. cancer cells have high energy). While live systems use adenosine triphosphate to tune the energetical input, we used temperature as an alternative as it allows tight control and simplicity.
Both enantiomers, i.e. fmoc-D-GlcN and fmoc-L-GlcN, were able to assemble into nanofibres (AFM and fluorescence spectroscopy) and gel upon heating and following cooling to room temperature. However, the energy input generated significant differences in the supramolecular helicity as detected by CD. Fmoc-L-GlcN presented a similar CD profile when the nanofibres are generated through a fast (40 ºC/min) or slow cooling rate (5 ºC/min). On the other hand, fast cooling induced a switch of CD signal for Fmoc-D-GlcN from positive to negative values. We also evaluated the storage modulus (G’) and gelation temperature (Tgel) of the produced hydrogels under the different cooling rates. As expected, there is an increment of both properties with the increase of the amphiphile’s concentration (i.e. G’24mM>G’12mM, Tgel24mM>Tgel12mM). However, fmoc-D-GlcN always generated stiffer gels when prepared under a slow cooling regime, while the same happened for fmoc-L-GlcN when prepared using fast cooling conditions. This could be explained by alterations on the nucleation and nanofiber growth kinetics as a function of the GlcN enantiomer.
Our results demonstrate that amphiphiles of carbohydrate enantiomers and the energy input can generate different nanofibre organization, which is reflected in the macroscopic properties of the generated hydrogels.