Protein absorbption is a natural phenomenon that is relevant to a vareity of bio
ID: 2252785 • Letter: P
Question
Protein absorbption is a natural phenomenon that is relevant to a vareity of biomedical applications.
Protein adsorption is a natural phenomenon that is relevant to a variety of biomedical applications. For instance, after a pharmaceutical company finishes the manufacturing a protein drug, the protein drug has to be stored in a container. The adsorption of protein to the wall of the container can induce permanent denaturation of protein drugs and the loss of therapeutic efficacy. Moreover, the denatured proteins can cause undesired immune response against normal protein drugs. Another example is related to the implantation of a biomaterial (e.g., artificial blood vessel) to the human body. Protein adsorption to the surface of the implant often leads to thrombosis and the failure of implantation. Therefore, it is important to understand the mechanism of protein adsorption at the solid-liquid interface. However, the adsorption behavior of proteins at interfaces results from various types of interactions between the different components in the system. These factors account for the occurrence of spontaneous protein adsorption (at constant pressure and body temperature) that is driven by the decrease of the Gibbs energy of the system. The following table shows the experimental analysis of the changes of enthalpy and entropy to analyze several important factors. The experiment was pursued by using lysozyme and polystyrene as a model. Based on the experimental data collected at 37 degree C, please calculate the contribution of each factor to the change of Gibbs free energy and analyze which factor makes more contribution to the change of Gibbs free energy. Moreover, based on the data shown in the table and your calculation, please further analyze why that factor makes so much contribution from the viewpoint of thermodynamics.Explanation / Answer
1) Electrostatic interactions
dG = dH - TdS
given temp T = 310 K
dG = -80 + 0.37 x 310
dG = 34.7
2) Surface dehydration
dG = dH - TdS
dG = -40 - 0.6 x 310
dG = -226
3) conformational change
dG = 50- 0.37 x 310
dG = -64.7
So the Surface dehydration contributes more to the change in gibbs free energy
electrostatic forces do not contribute to the decrease in free energy . Becasue of the interactions there is a loss in
entropy and low enthalpy value .
Surface dehydration contributes largely because enthalpy is a bit high and the major factor is increase in entropy .
Thewater molecules are removed and there is a more positive change in entropy ,which is a driving force for ad sorption .
conformational changes in the protein can greatly contribute to the driving force for adsorption. Proteins are highly
ordered structures (i.e., states of low conformational entropy). Partial or complete unfolding of the protein on the sorbent
surface leads to an increase in conformational entropy, which can be the driving force for protein adsorption.
The driving force for adsorption is non-electrostaticaly forces, dehydration of the hydrophilic surface and entropy
gain from conformational changes.
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