Kinetics Modelling And Experiment Study Of Protein Aggregation Processes

With the continuous development of detection theory and technology,detection object has extended to image, chemistry, biology, medicine and otherfields from the traditional detection field, protein aggregation phenomenon iswidespread in the field of biological pharmacy, food, chemical and so on. Studyon protein dynamic accumulation process is one of hot topics in the study ofscholars, the research is of great significance for protein accumulation resultingin a loss of efficacy, cause immune response, related toxicological effect, such asthe shelf life of medicine in biological medicine.The protein aggregation process mainly depends on experience formula, thelaw of mass action, the relevant mathematical model to predict the results. If wecan continuously control initial conditions in the production process, using thetested intermediate results to modify initial conditions, the closed loop controlcan prevent protein concentrations as much as possible. How to control the initialcondition and which time points in the process of aggregation is more effective tomodify initial conditions, depends on dynamic equation of the accumulationprocess. At present, the models of accumulation dynamics equation are allassumed:1protein belongs to a particular morphology, such as spherical, rodsand other simple geometric shapes;2On the basis of assumption that certainmorphology, calculate the size of aggregate particles;3Accumulation is adynamic process and it includes nucleation, aggregation, growth anddepolymerization behavior, on the basis of the former two behaviors,identification of model parameters, obtain the initial conditions of equation, itcan be seen that this method is lack of universality, because of the topography ofprotein is complex and changing. In this paper, fractal dimension method is usedto describe and express the aggregation morphology, instead of assuming ageometric shape, in order to establish a new aggregate dynamic model. Thismodel can reflect aggregate size and fractal dimensions characteristics at the same time, increase the universality, initial conditions of the model, parameterestimation and identification of model parameters at the same time, simulationand experimental work is used for verify the proposed model and the satisfactoryresult is given.In this research, the main work can be summarized as follows:1. Adopt fractal theory and population balance equation (PBE), dynamicmodel is proposed for describe protein aggregation process, the growth functionand kernel function of dynamic model was deduced. The proposed modelaccomplishment dynamic size and dynamic fractal dimension simulation bycomputer simulation. The model can parse the size and fractal dimension ofprotein aggregation at the same time. In view of calculation problems ofaggregate size and fractal dimension, finite element cover Larkin method is usedto compile computer software and the purpose is to solve dynamic equations.2. In the process of closed loop control, constantly revised initial conditions,that is model parameters. Aim at the identification problem of aggregationdynamic model, a kind of protein aggregation process model parameteridentification method is proposed based on K-L information distance, optimizingthe algorithm, initial conditions and experimental testing point of proteinaggregation process were given, this method can guide the experimental designof experimental verification work and select lysozyme aggregate experiment ofuniversal significance.3. This method was applied to lysozyme aggregation process control, makeuse of the given initial conditions, time check points by parameter identificationmethod, using a laser granulometer and density gauge measuring general rule ofsize and concentration change during lysozyme cooling gathered process,according to the change rule, precise fitting size and concentration change rulebased on aggregation kinetics parameters. Experiments show that dynamic modelof describe protein aggregation process based on fractal theory and populationbalance equation (PBE) is proposed, the model can effectively predict theaggregation morphology and distribution.4. Aimed at the Macro aggregation phenomenon in the process ofaggregation is difficult to measured, large size particles fractal dimensionmeasurement problem is studied, with different dilution condition to add rennetin milk solution as the experimental materials, a new dense aggregates fractal dimension measuring method based on PBE simulation model is proposed, in thecase of don’t build aggregation cross-correlation function, measuring proteinaggregation large size fractal dimension.5. Establish a protein aggregation process measurement system, the systemis used to verify the effectiveness of the proposed method in the dissertation, inthe process of hen egg white lysozyme intermittent cooling condition, theinfluence of temperature, pH value and other condition on the accumulationprocess is studied by the proposed model. The results showed that lysozymeaccumulation process difference is bigger under the condition of differenttemperature and pH value, the PBE mathematical model has a good predictionwith accumulation process difference. Systematically studied the relationshipbetween protein aggregation light scattering characteristics and fractal features、aggregation size distribution、 fractal dimension distribution and proteinaggregate particles, the article proposed method laid a foundation for the study ofaggregation process instrumentation.