Research On The Mechanism Of Amyloid Peptide Self-assembly And Its Modulation

In recent decades,studies have shown that the misfolding and abnormal aggregation of amyloid peptide is one of the major causes of many degenerative diseases,such as type II diabetes,Alzheimer's disease,Parkinson's disease,and Huntington's disease.The cytotoxicity of amyloid proteins is mainly derived from the aggregation of amyloid protein and the interaction between aggregates and cell membranes.In this paper,we focused on dimensionality of carbon nanomaterial impacting on the modulation of amyloid peptide assembly,differential modulating effect of MoS₂ on amyloid peptide assemblies,thermal effect on the degradation of hIAPP20-29 fibrils.At the same time,we focused on exploring the intermolecular force of amyloid peptides.This study has profound implications for understanding the pathological mechanism of amyloidosis and provides a theoretical basis for the development of potential therapeutic approaches.1)We studied the modulation effect of three carbon nanomaterials with different dimension?graphene oxide,carbon nanotubes,and carbon quantum dots?on A?33-42peptide assembly.Firstly,pure A?33-42 peptide of different concentration were incubated at 37°C for 12.5 h.Atomic force microscopy and quartz crystal microbalance were used to explore the concentration condition for the formation of A?33-42 fibrils.Then graphene oxide,carbon nanotubes and carbon quantum dots were incubated with A?33-42 peptide at 37°C for 12.5 h.The modulating effect of three carbon nanomaterials on A?33-42 peptide assembly was studied by quartz crystal microbalance,atomic force microscopy,and circular dichroism spectroscopy.The result shows that the two-dimensional material graphene oxide had the strongest effect on A?33-42 peptide assembly,followed by one-dimensional material carbon nanotubes,and the zero-dimensional material carbon quantum dots were the weakest.2)On the basis of the previous study,we also studied the modulating effect of molybdenum disulfide?MoS₂?on A?33-42 and hIAPP20-29 peptide assembly.First,MoS₂ with different concentrations were incubated with A?33-42 peptide at 37°C,respectively.Then the mixtures were characterized by atomic force microscopy.The result shows that the modulation effect of MoS₂ on A?33-42 peptide assembly is very strong,and the modulation effect is proportional to the concentration of MoS₂.Next,the modulation effect of MoS₂ on hIAPP20-29 peptide assembly was studied by similar mothed.The result indicates that MoS₂ has a stronger modulation effect on hIAPP20-29 peptide assembly than the modulation on A?33-42 peptide assembly.Then we monitored the assemblies of the mixture of A?33-42 and MoS₂ or the mixture of hIAPP20-29 and MoS₂,with peptide of different concentrations in real time on a gold chip by quartz crystal microbalance.The result shows that the modulation effect of MoS₂ on hIAPP20-29 peptide assembly was similar to the modulation on A?33-42 peptide,although both of which have similar trend.Finally,the secondary structure of the mixtures of MoS₂ and A?33-42 or the mixtures of MoS₂and hIAPP20-29 after incubation was studied by circular dichroism.The result shows that MoS₂ resulted in the reduction of?-sheet structure during the assembling of A?33-42 and hIAPP20-29 peptide,and with the concentration of MoS₂ increase,the content of?-sheet structure formed became less.Finally,we calculated and the modulation effect of MoS₂ on A?33-42 and hIAPP20-29 peptide assemblies.The result shows that compared to A?33-42 peptide assembly,the modulation effect of MoS₂ on hIAPP20-29 peptide assembly is stronger than on A?33-42 peptide assembly.3)In addition,we also studied the effect of temperature on the thermal degradation of amyloid fibrils.Firstly,hIAPP20-29 peptide was incubated at 37°C for12 h.Atomic force microscopy was used to determine the concentration condition in the formation of hIAPP20-29 mature fibrils.Then,hIAPP20-29 mature fibrils were heat-treated at 50,60 and 80°C for 24 h,respectively,and the samples before and after heat treatment were characterized by atomic force microscopy.The result shows that heat treatment could lead to the degradation of hIAPP20-29 mature fibrils.The mechanical properties of amyloid aggregates before and after heat treatment were also studied by atomic force microscopy.The result shows that the heat treatment can make the Young's modulus and adhesion of the fibrils to decrease.Finally,the secondary structure of amyloid aggregates before and after heat treatment was studied by circular dichroism.The result shows that the heat treatment resulted in the change in the secondary structure of the amyloid fibrils.A possible mechanistic explanation was proposed:As the temperature increases,the internal secondary structure of the amyloid fibril varies,with more and more hydrophobic groups exposing outside,and the hydrophobic interaction being weaken,and finally resulting in the degradation of amyloid fibrils.