Selective Protein Separation Based On Spherical Polyelectrolyte Brush

Phase separation based on polyelectrolyte complexs is a simple,efficient,and highly selective new method for proteins separation and purification.It makes up for some of the shortcomings of existing protein separation methods and is a promising new technology.Due to the anisotropy of the surface charge of the protein,when polyelectrolyte interacts with it,polyelectrolyte can selectively adsorb the target protein under certain conditions to achieve the separation and purification of the protein.The nature of this interaction is an electrostatic interaction,which is affected by factors such as pH and ionic strength in the solution.The separation process can be optimized by adjusting these variables.In this paper,the interaction between a single nanosphere polyelectrolyte brush and various proteins and the interaction between a polyelectrolyte system containing two opposite charges and various proteins are respectively investigated.Moreover,the effect of pH and ionic strength on the interaction were explored,verifying the possibility of separating proteins using the anisotropy of the protein charge.The main research contents are as follows:1.Herein,the protein binding behaviors on SPBs were probed as an effect of charge anisotropy of proteins.Strong cationic SPBs can achieve higher binding affinity than weak cationic SPBs.The strong cationic groups likely provide stronger binding affinity hence better selective adsorptions of proteins on SPBs which ultimately leads to better phase separations of proteins.The interaction between proteins with similar isoelectric points(BSA and BLG)and PDMC-SPB was explored by turbidimetric titration and isothermal calorimetry.Although they have very similar isoelectric points,the negative charge distribution on the surface of BLG is more concentrated,resulting in its selective binding to PDMC-SPB.By adjusting the pH and ionic strength,the protein separation conditions were optimized,and the selective adsorption of BLG by PDMC-SPB was used to separate the mixture of BSA and BLG based on the phase separation method.2.The interaction between PDMC-SPB and two proteins with similar molecular weights(BSA and HB)was studied.The main analytical methods are turbidity titration and isothermal calorimetry.Although the molecular weights of these two proteins are similar,the surface of BSA has a more concentrated negative charge region relative to HB,so BSA can selectively bind to PDMC-SPB,and the protein separation conditions are also optimized by adjusting pH and ionic strength.BSA was selectively separated in a mixture of BSA and HB.3.The selective separation of PDMC-SPB for complex three protein systems(BSA,BLG and HB)was studied,due to the difference in their binding strength with PDMC-SPB:BLG>BSA>HB.Based on the phase separation method,through two separation experiments,BLG,BSA and HB were sequentially separated,showing a high separation efficiency.4.The adsorption behavior of proteins in the ternary system of cationic polyelectrolyte,anionic polyelectrolyte and protein(PDMAEMA-HA and lysozyme,PDMAEMA-HA and BLG,PAH-HA and lysozyme,PAH-HA and BLG)was studied.The electrolytes ratio F-is an important influencing factor.At different F-,the system and protein will have different interaction behaviors,and there is an optimal ratio Fopt-.Under this condition,the system has maximum adsorption capacity for protein.Fopt-has a lot to do with the properties of the protein and the polyelectrolyte.Ionic strength and pH are also very important influencing factors.By adjusting the ionic strength and pH of the system,protein adsorption and desorption can be controlled.In this experiment,PAH-HA system was used to separate lysozyme and BLG under the condition of F-=0.55.PAH-HA system was able to selectively adsorb BLG.