2011.05.17,Professor Sun Lianhong Published a paper entitled "Electrostatic Selectivity in Protein_Nanoparticle Interactions" in Biomacromolecules

  • Author:Kaimin Chen,Yisheng Xu,SubinoyRana,Oscar R. Miranda,Paul L. Dubin, Vincent M. Rotello,Lianhong Sun,and XuhongGuo

    Abstact:The binding of bovine serum albumin (BSA) and β-lactoglobulin (BLG) to TTMA (a cationic gold nanoparticle coupledto 3,6,9,12-tetraoxatricosan-1-aminium, 23-mercapto-N,N,N-trimethyl)was studied by high-resolution turbidimetry (to observe a critical pHfor binding), dynamic light scattering (to monitor particle growth),and isothermal titration calorimetry (to measure binding energetics),all as a function of pH and ionic strength. Distinctively higher affinitiesobserved for BLG versus BSA, despite the lower pI of the latter, wereexplained in terms of their different charge anisotropies, namely, thenegative charge patch of BLG. To confirm this effect, we studied twoisoforms of BLG that differ in only two amino acids. Significantly strongerbinding to BLGA could be attributed to the presence of the additionalaspartates in the negative charge domain for the BLG dimer, bestportrayed in DelPhi. This selectivity decreases at low ionic strength, at which both isoforms bind well below pI. Selectivity increaseswith ionic strength for BLG versus BSA, which binds above pI. This result points to the diminished role of long-range repulsions forbinding above pI. Dynamic light scattering reveals a tendency for higher-order aggregation for TTMA_BSA at pH above the pI of BSA,due to its ability to bridge nanoparticles. In contrast, soluble BLG_TTMAcomplexes were stable over a range of pHbecause the chargeanisotropy of this protein atmakes it unable to bridge nanoparticles. Finally, isothermal titration calorimetry shows endoenthalpic bindingfor all proteins: the higher affinity of TTMA for BLGA versus BLGB comes from a difference in the dominant entropy term.

    dx.doi.org/10.1021/bm200374e | Biomacromolecules 2011, 12, 2552–2561

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