This communication describes the self-assembly of a tripeptide into a functional coating that resists biofouling. Using this peptide-based coating we were able to prevent protein adsorption and interrupt biofilm formation. This coating can be applied on numerous substrates and therefore can serve in applications related to health care, marine and water treatment.
Understanding the mechanism of interaction between peptides and inorganic materials is of high importance for the development of new composite materials. Here, we combined an experimental approach along with molecular simulations in order to gain insights into this binding process. Using single molecule force spectroscopy by atomic force microscopy and molecular simulations we studied the binding of a peptide towards an inorganic substrate. By performing alanine scan we examined the propensity of each amino acid in the peptide sequence to bind the substrate (mica). Our results indicate that this binding is not controlled by the specific sequence of the peptide, but rather by its conformational freedom in solution versus its freedom when it is in proximity to the substrate. When the conformational freedom of the peptide is identical in both environments, the peptide will not adhere to the substrate. However, when the conformational freedom is reduced, i.e., when the peptide is in close proximity to the substrate, binding will occur. These results shed light on the interaction between peptides and inorganic materials.
A limitation of the amyloid hypothesis in explaining the development of neurodegenerative diseases is that the level of amyloidogenic polypeptide in vivo is below the critical concentration required to form the aggregates observed in post-mortem brains. We discovered a novel, on-surface aggregation pathway of amyloidogenic polypeptide that eliminates this long-standing controversy. We applied atomic force microscope (AFM) to demonstrate directly that on-surface aggregation takes place at a concentration at which no aggregation in solution is observed. The experiments were performed with the full-size Aβ protein (Aβ42), a decapeptide Aβ(14-23) and α-synuclein; all three systems demonstrate a dramatic preference of the on-surface aggregation pathway compared to the aggregation in the bulk solution. Time-lapse AFM imaging, in solution, show that over time, oligomers increase in size and number and release in solution, suggesting that assembled aggregates can serve as nuclei for aggregation in bulk solution. Computational modeling performed with the all-atom MD simulations for Aβ(14-23) peptide shows that surface interactions induce conformational transitions of the monomer, which facilitate interactions with another monomer that undergoes conformational changes stabilizing the dimer assembly. Our findings suggest that interactions of amyloidogenic polypeptides with cellular surfaces play a major role in determining disease onset.
A terminally protected tripeptide Boc-Val(1)-Phe(2)-Phe(3)-OMe 1 having sequence similarity with Ab 18-20 (the central hydrophobic fragment 18-20 of the amyloid b-peptide Ab 42 ) forms sonication induced organogels. The peptide forms a very weak gel only in 1,2-dichlorobenzene after heating, cooling and ageing for 3 days. But ultrasound energy induces instant fibril formation and gelation in a wide range of organic solvents starting from hexane, cyclohexane, petrol, kerosene to benzene, toluene, xylene and ethanol. CD, FT-IR, NMR and wide angle X-ray scattering (WAXS) studies of the peptide 1 exhibit distinct structural changes before and after sonication. Atomic force microscopy (AFM) and field emission scanning electron microscopy (FE-SEM) of the xerogels reveal a nanofibrillar morphology, which is obtained by the sonication induced self-assembly of the gelator. These gels bind with Congo red, a physiological dye, and show a green-gold birefringence under polarized light, a characteristic feature of amyloid fibrils.
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