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Research On The Interaction Mechanism Between Spirulina Platensis Photosystem I And Lipopeptides

Posted on:2022-12-24Degree:MasterType:Thesis
Country:ChinaCandidate:R R ChenFull Text:PDF
GTID:2530307109463724Subject:Biochemical Engineering
Abstract/Summary:PDF Full Text Request
Surfactants are the basis for the correct analysis of the structure and function of photosynthetic membrane proteins,and are critical to the structural integrity and thermal stability of membrane protein complexes.The use of surfactants can improve the solubility of membrane proteins in vitro environment,but it is still challenging to find suitable surfactants that can increase the solubility without destroying its natural structure and biological activity.Previous studies have found that the biosurfactant lipopeptides have a huge advantage in the stability of membrane proteins,but the interaction mechanism of membrane protein-lipopeptide surfactants is still unclear.The subject takes the photosynthetic membrane protein complex-photosystem I of Spirulina platensis as the research object to study the structural integrity,time stability and thermal stability of PSI particles and n-dodecyl-β-D-maltoside(DDM)pre-solubilized PSI in lipopeptide solution system,further analyze thermodynamic process and microscopic mechanism of PSI and lipopeptides,select the interaction mode and types of lipopeptides that have better solubilization and stabilization effects on PSI,achieve the complete solubilization of membrane proteins by using low-concentration lipopeptides in a short time,and construct PSI-lipopeptide complexes that keep the PSI structural integrity and high stability.Based on the structure of the CyNDND lipopeptides designed in previous stage,lipopeptides with expected function were obtained by regulating the alkyl chain length of hydrophobic tail fatty acids and the number of hydrophilic head amino acids.The new types of CyND lipopeptides are designed and synthesized,then the self-assembly behavior and the microscopic morphology of the assembly of the new lipopeptides in buffer solution were investigated by using various characterization methods such as surface tensiometer,circular dichroism spectrometer,and transmission electron microscope.Firstly,the CyNDND lipopeptides were studied to interact with PSI.The data shows that1×CMC lipopeptide CyNDND has insufficient solubilization ability for PSI,and the use of vertical mixing to accelerate the solubilization of PSI leads to a small amount of chlorophyll uncoupling.During the temperature-programming process,different lipopeptides show different thermodynamic processes when they interact with PSI.The lipopeptides with long alkyl chains have strong solubilizing ability and more damage to the PSI structure.The synergistic effects of high temperature and lipopeptides lead to a large number of chlorophyll uncoupling and PSI protein subunit aggregation and denaturation,and even irreversible unfolding of α-helix.Secondly,the interaction between CyNDND lipopeptides and DDM pre-solubilized PSI was studied.It is found that the method can achieve complete solubilization of PSI particles,however,when PSI is in a fully solubilized state,it is more susceptible to damage by the mechanical action of vertical mixing.The synergistic effects of high temperature and lipopeptides aggravate chlorophyll uncoupling,and the framework of PSI protein subunits tends to aggregate and denature.At the same time,the hydrogen bond formed by lipopeptide CyNDND itself during the cooling process,which has a certain stabilizing effect on the structure of PSI protein subunit and inhibits high temperature hydrogen bond dissociation and denaturation of protein subunits.Finally,the new types of CyND lipopeptides with lower CMC interact DDM pre-solubilize PSI to achieve complete solubility of membrane proteins with lower concentration of lipopeptides in a short period of time,and to maintain PSI structural integrity for a long time when standing at room temperature.Compared with the CyNDND lipopeptides,the new CyND lipopeptides have less number of hydrophilic head groups,which is less damage to the structure of PSI complex and more useful to maintain the integrity of PSI structure during the solubilization process,and to a certain extent,improves the thermal stability of PSI.The synergistic effects of high temperature and lipopeptides aggravate the chlorophyll uncoupling process,which initiates the aggregation and degeneration of PSI protein subunits and the formation of white precipitate,and even accelerates the unfolding of α-helices.In summary,the subject uses a variety of characterization methods to systematically compare the interaction between lipopeptides and PSI before and after heat treatment,and conducts in-depth study on the interaction between PSI complex and lipopeptide at room temperature,the thermodynamic process and the components of the PSI-lipopeptide assembly after heat treatment,which has laid a foundation for the construction of the PSI-lippeptide complex that maintains the integrity of the PSI structure and has a high stability and helps to promote the structure and function research of related membrane proteins.
Keywords/Search Tags:Photosystem Ⅰ, Lipopeptides, n-dodecyl-β-D-maltoside, Solubilization, Stability
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