Mechanism Of The Effect Of Changes In Electrochemical Properties Of Oxidized Modified Sarcoplasmic Proteins On Protein Hydration

During the processing and post-mortem storage of muscles,protein oxidation is highly prone to occur.Under the action of free radicals and related oxides,proteins will deteriorate,and it will increase muscle juice loss.Protein oxidation is essentially a process of electron transfer.The change of surface charge of the protein will affect the electrostatic interaction between the protein and water.However,the mechanism of the electrochemical nature of protein oxidation affecting its surface charge is still unclear.In this paper,the sarcoplasmic protein was extracted from the longissimus dorsi muscle,and the three oxidative simulation systems of linoleic acid/lipoxygenase?OLA?,malondialdehyde?MDA?and hydroxyl radical?·OH?were applied to the sarcoplasmic protein.After dialysis and salt removal,we can analyze the change of surface charge for protein hydration ability,and provide a theoretical basis for further revealing the mechanism of protein oxidation on protein water retention.The main research contents and results of this thesis are as follows:1.To investigate the effects of different concentrations of linoleic acid?0,0.5,1,5,10 and 20 mmol/L?on the surface charge characteristics,protein structure and hydration effects of sarcoplasmic proteins in linoleic acid/lipoxygenase?OLA?oxidation system,the sarcoplasmic protein extracted from the longissimus dorsi of Du Chang Da ternary crossbred pigs was used.After deoxidation and dialysis for 48 h,the desalting effect was good.After 48 h,the phosphate content in dialysate decreased by 99.43%compared with dialysis for 3 h.The thiol content,amino acid content,zeta potential,protein surface hydrophobicity and protein secondary structure of the sample were determined.The results showed that with the increase of linoleic acid concentration,the content of sarcoplasmic peptone decreased from 183.36 nmol/mg to 170.55 nmol/mg.The zeta potential of the protein decreased first and then increased with the increase of linoleic acid concentration.Oxidation causes the hydrophobicity of the protein surface to rise first and then decrease,which is opposite to the positive charge change,and causes the secondary structure of the protein to change,the?-helix content is significantly decreased?p<0.05?,and the irregular curl content is significantly increased?p<0.05?.In summary,the experimental results show that,oxidation leads to poor structural stability of the protein,and the more net positive charge on the surface of the protein,the stronger the protein hydration effect.2.To investigate the effects of different concentrations of MDA?0?0.5?1?5?10and 20 mmol/L?on the surface charge characteristics,protein structure and hydration effects of sarcoplasmic proteins,the Lipid secondary oxidation products represented by malondialdehyde?MDA?act on sarcoplasmic proteins.The results showed that with the increase of MDA concentration,the content of sarcoplasmic peptone decreased from181.29 nmol/mg to 168.49 nmol/mg,and the content of positively charged lysine,arginine and glutamic acid decreased significantly?p<0.05?.The zeta potential of the protein decreased with increasing H₂O₂ concentration,with the zeta potential decreasing from 1.24 mV?0 mmol/L MDA?to-7.02 mV?20 mmol/L MDA?.Oxidation caused a significant increase in the hydrophobic content of the protein surface?p<0.05?,and caused a change in the secondary structure of the protein,a significant decrease in the?-helix content and a significant decrease in the random curl content?p<0.05?,and a significant increase in the?-turn content?p<0.05?.In summary,the experimental results show that as the degree of oxidation increases,the positive charge number on the surface of the protein decreases significantly,and the stability of the protein structure deteriorates,resulting in weakened protein hydration.3.Study on the effects of different concentrations of H₂O₂?0?0.5?1?5?10 and20 mmol/L?on the surface charge characteristics,protein structure and hydration effects of sarcoplasmic proteins in the oxidation system of iron-ascorbic acid-hydrogen peroxide?FeCl₃-Vc-H₂O₂?.The results showed that with the increase of H₂O₂concentration,the content of sarcoplasmic peptone decreased from 177.16 nmol/mg to159.96 nmol/mg,the content of cysteine and lysine decreased significantly?p<0.05?.The zeta potential of the protein decreased with the increase of H₂O₂ concentration,the zeta potential value decreased from 5.98 mV?0 mmol/L H₂O₂?to 3.93 mV?20 mmol/L H₂O₂?,and the absolute value decreased significantly?p<0.05?.Oxidation resulted in a significant increase in the hydrophobic content of the protein surface?p<0.05?,and at the same time it caused a change in the secondary structure of the protein,a significant decrease in the?-helix content?p<0.05?and a significant increase in the random curl content?p<0.05?.In summary,the experimental results show that protein oxidation leads to a significant decrease in the surface positive charge number,and the stability of the protein structure deteriorates,resulting in weakened protein hydration.