| Protein is the most abundant organic substance in the human body.It has biological functions such as catalysis and transport,and plays an indispensable role in human life activities.However,proteins can only exert normal physiological functions in the correct conformation,once the protein is misfolded to form a wrong spatial structure,it will not function properly,and these misfolded proteins will aggregate and form protein precipitates.These precipitates are fibrous,so this behavior is also caled fibrosis of proteins.This amyloid fiber is highly cytotoxic,causing great damage to the organism and causing various neurodegenerative diseases.At present,the main measures taken in clinical practice for these diseases are to find suitable inhibitors to prevent the formation of fibrils,so as to control the occurrence of diseases,but for mature amyloid fibrils,find suitable drugs to destroy its stability,which in turn breaks down mature fibers into small molecule fragments,is also an important measure.Curcumin has strong antioxidant capacity and can inhibit the production of amyloid fibrils,but its solubility in water is too smal,which limits its application in medicine.In order to improve the water solubility of curcumin,a water-soluble curcumin derivative was prepared by modifying isopin with isoleucine: curcumin-isoleucine ester,and used egg white lysozyme(HEWL)as a model protein to investigate the effect of synthetic curcumin-isoleucine ester on lysozyme fibrosis.Finally,curcumin-isoleucine ester was added to the mature lysozyme fiber system to study its effect on the stability of mature lysozyme fiber.The main contents of this paper can be divided into three parts:Chapter 1: A brief introduction to the process and effects of protein fibrosis,as well as screening for protein fibrosis inhibitors.Chapter 2: Commercially available Boc-L-isoleucine and curcumin were used as raw materials to obtain the target product by esterification reaction and de Boc protection group: curcumin-isoleucine diester(DILC)and curcumin-isoleucine monoester(MILC),the solubility of the two in water was tested by gravimetric analysis.The solubility of DILC and MILC was calculated to be 3.05 mg/mL and 2.12 mg/mL(293K),respectively,which was much larger than curcumin solubility in water: 1-10 ?g/mL.At the same time,the effects of curcumin derivatives on lysozyme fibrosis were investigated by spectroscopy and transmission electron microscopy.The results showed that the modified curcumin still inhibited the lysozyme fibrosis,and the inhibitory effect was concentration-dependent,but at the same concentration,MILC is better than DILC,indicating that phenolic hydroxyl in curcumin plays an important role in inhibiting lysozyme fibrosis,but it is not the only group that plays its role.Chapter 3: The curcumin derivative was added to the mature lysozyme fibril system,and the curcumin-isoleucine ester was stabilized against mature fiber by ThT fluorescence,ultraviolet-visible absorption,circular dichroism spectroscopy and transmission electron microscopy.Research indicates,both curcumin derivatives can reduce the stability of mature fibers and destroy its structure,and the higher the temperature,the shorter the decomposition time.At the same temperature,the decomposition rate of mature fibers by MILC is higher than that of DILC.And it can be clearly seen by transmission electron microscopy that mature filamentous fibers are broken down into smaler fragments. |
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