We study the thermodynamics of the interaction between human serum albumin (HSA) and dendritic polyglycerol sulfate (dPGS) of different sizes (generations) by isothermal titration calorimetry (ITC) and computer simulations. The analysis by ITC revealed the formation of a 1:1 complex for the dPGS-G2 of second generation. The secondary structure of HSA remained unchanged in the presence of dPGS-G2, as shown by circular dichroism. For higher generations, several HSA are bound to one polymer (dPGS-G4: 2; dPGS-G5.5: 4). The Gibbs free energy ΔGb was determined at different temperatures and salt concentrations. The binding constant Kb exhibited a logarithmic dependence on the salt concentration thus indicating a marked contribution of counterion-release entropy to ΔGb. The number of released counterions (∼4) was found to be independent of temperature. In addition, the temperature dependence of ΔGb was small, whereas the enthalpy ΔHITC was found to vary strongly with temperature. The corresponding heat capacity change ΔCp,ITC for different generations was of similar values [8 kJ/(mol K)]. The nonlinear van’t Hoff analysis of ΔGb revealed a significant heat capacity change ΔCp,vH of similar magnitude [6 kJ/(mol K)] accompanied by a strong enthalpy-entropy compensation. ΔGb obtained by molecular dynamics simulation with implicit water and explicit ions coincided with experimental results. The agreement indicates that the enthalpy-entropy compensation assigned to hydration effects is practically total and the binding affinity is fully governed by electrostatic interactions.
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28 October 2018
Research Article|
July 18 2018
Interaction of human serum albumin with dendritic polyglycerol sulfate: Rationalizing the thermodynamics of binding
Special Collection:
Chemical Physics of Charged Macromolecules
Qidi Ran;
Qidi Ran
1
Institute of Chemistry and Biochemistry, Freie Universität Berlin
, Takustr. 3, 14195 Berlin, Germany
2
Institute of Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin
, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
3
Multifunctional Biomaterials for Medicine, Helmholtz Virtual Institute
, Kantstr. 55, 14513 Teltow-Seehof, Germany
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Xiao Xu;
Xiao Xu
4
School of Chemical Engineering, Nanjing University of Science and Technology
, 200 Xiao Ling Wei, 210094 Nanjing, People’s Republic of China
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Pradip Dey
;
Pradip Dey
1
Institute of Chemistry and Biochemistry, Freie Universität Berlin
, Takustr. 3, 14195 Berlin, Germany
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Shun Yu;
Shun Yu
2
Institute of Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin
, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
5
Institut für Physik, Humboldt-Universität zu Berlin
, Newtonstr. 15, 12489 Berlin, Germany
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Yan Lu;
Yan Lu
2
Institute of Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin
, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
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Joachim Dzubiella;
Joachim Dzubiella
2
Institute of Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin
, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
3
Multifunctional Biomaterials for Medicine, Helmholtz Virtual Institute
, Kantstr. 55, 14513 Teltow-Seehof, Germany
6
Physikalisches Institut, Albert-Ludwigs-Universität
, 79104 Freiburg, Germany
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Rainer Haag;
Rainer Haag
a)
1
Institute of Chemistry and Biochemistry, Freie Universität Berlin
, Takustr. 3, 14195 Berlin, Germany
3
Multifunctional Biomaterials for Medicine, Helmholtz Virtual Institute
, Kantstr. 55, 14513 Teltow-Seehof, Germany
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Matthias Ballauff
Matthias Ballauff
b)
2
Institute of Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin
, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
3
Multifunctional Biomaterials for Medicine, Helmholtz Virtual Institute
, Kantstr. 55, 14513 Teltow-Seehof, Germany
5
Institut für Physik, Humboldt-Universität zu Berlin
, Newtonstr. 15, 12489 Berlin, Germany
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a)
Electronic mail: [email protected]
b)
Electronic mail: [email protected]
J. Chem. Phys. 149, 163324 (2018)
Article history
Received:
March 23 2018
Accepted:
June 28 2018
Citation
Qidi Ran, Xiao Xu, Pradip Dey, Shun Yu, Yan Lu, Joachim Dzubiella, Rainer Haag, Matthias Ballauff; Interaction of human serum albumin with dendritic polyglycerol sulfate: Rationalizing the thermodynamics of binding. J. Chem. Phys. 28 October 2018; 149 (16): 163324. https://doi.org/10.1063/1.5030601
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