Investigation On The Interaction Mechanisms Between Low-dimensional Small-sized Carbon-based Nanomaterials And Key Proteins Of Protein Conformational Diseases

Diseases caused abnormal changes in the spatial structure of proteins are called Protein Conformational Diseases(PCDs),including Alzheimer’s disease(AD),Parkinson’s disease(PD),cataracts and type Ⅱ diabetes,etc.The hallmark of these diseases is the abnormal aggregation of specific proteins,and ultimately pathological changes in tissues and organs.Many studies have revealed that each of these diseases is associated to a specific protein,such as AD and amyloid β-protein(Aβ),cataracts and human y-crystallins(HγD-crys).In this dissertation,we focus on AD and cataract in PCDs,and introduce the research progress of protein misfolding aggregation in recent years.Then,we explored the potential therapeutic effect of low-dimensional small sized carbon-nanomaterials-f-Gd@C82 and C3N on AD and the interaction mechanism between these two carbon-based nanomaterials with Aβ1-42,by using the combination of experiments and molecular dynamics(MD)simulation.In addition,we also explored the interaction mechanism between lanosterol and human γD-crystallins(HγD-crys),another key protein of cataract,by using MD simulation.(ⅰ)Embedded metal fullerenes(EMFs),usually have more unique properties and have very broad application prospects in biomedicine and other fields.Here,we prepared a functional EMF,f-Gd@C82.in vitro and cell experiments showed that f-Gd@C82 can significantly inhibit the aggregation of Aβ1-42 and inhibit the cellular cytotoxicity caused by Aβ1-42 in neurons.Further MD simulation studies revealed that f-Gd@C82,On the one hand,inhibiting the formation of ordered oligomer structureβ-sheet of Aβ1-42 through electrostatic interaction;on the other hand,f-Gd@C82 specifically binds to the significant areas of Aβ1-42 protofibrils,hindering the elongation and lateral binding of the Aβ1-42 oligomer/monomer,thus preventing the further formation of higher order aggregates.(ii)Heteroatom-doped(such as nitrogen,boron,sulfur,and phosphorus)carbon nanomaterials have recently emerged as promising nanomaterials.Due to their remarkable mechanical,optical,and electrical properties.In this dissertation,we selected C3N nano-dots as our model material because its small size and good photochemical stability.MD simulation results shown that C3N can completely adsorbs the Aβ1-42 peptide to its surface through hydrophobic,electrostatic and hydrogen bonding interactions,in which HγDrophobic interaction plays the leading role.Thus,preventing the formation of ordered secondary structure β-sheet,driving the peptide chain away from the "on-pathway",avoiding the generation of toxic oligomers and subsequent fibrosis.The experimental study shown that the C3N inhibit the aggregation of Aβ1-42 and reduce the cytotoxicity of neurons,effectively improve the learning and memory ability and cognitive behavior of AD mouse,.(iii)Lanosterol is a steroid compound highly enriched in the eye lens,which has been recently identified to reverse protein aggregation in cataracts.However,the interaction mechanism of lanosterol with crystallin is still unclear.Using MD simulation,we focused on the molecular interaction between lanosterol and UV damaged mutant HγD-Crys with higher aggregation tendency.That is,tryptophan is substituted by kynurenine,Trp>KN.It is found that lanosterol can prevent the mutant HγD-Crys from misunfolding into the aggregation precursor of "N-terminal(N-td)mostly unfolded,while C-terminal(C-td)partially unfolded".This strong structural protective activity of lanosterol originates from its capability to acts as a"water blocker",preventing the invasion of solvent molecules into the hydrophobic core.Thus protecting the structural stability of protein.Through our research work,we summarized some meaningful rules that nanomaterials or small molecules with small size,relatively amphiphilic,good dispersion,can form hydrogen bond with polypeptides,local hydrophobicity can destroy the hydrophobic core in protein polypeptides,which can disrupt the aggregation of conformational disease-related proteins and will have a certain potential for disease prevention and treatment.Our research of this dissertation contribute to the development and design of potential drug molecules that interfere with amyloid formation in protein PCDs,and provide a reference for the screening and design of other PCDs drugs.