Role of Anisotropic Interactions for Proteins and Patchy Nanoparticles

Roberts, Christopher J.; Blanco, Marco A.

doi:10.1021/jp507886r

Cited by 55 publications

(70 citation statements)

References 74 publications

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“…10 However, as proteins are complex molecules able to engage in a variety of protein-protein and protein-solvent interactions, models attempting to predict protein solution behavior at high concentrations have met with mixed results. 9, 11–14 …”

Section: Introductionmentioning

confidence: 99%

Charge Shielding Prevents Aggregation of Supercharged GFP Variants at High Protein Concentration

et al. 2017

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Understanding protein stability is central to combatting protein aggregation diseases and developing new protein therapeutics. At the high concentrations often present in biological systems, purified proteins can exhibit undesirable high solution viscosities and poor solubility mediated by short-range electrostatic and hydrophobic protein-protein interactions. The interplay between protein amino acid sequence, protein structure and solvent conditions to minimize protein-protein interactions is key to design of well-behaved pharmaceutical proteins. However, theoretical approaches have yet to yield a general framework to address these problems. Here, we analyzed the high concentration behavior of super-folder GFP (sfGFP) and two super-charged sfGFP variants engineered to have formal charges of −18 or +15. Under low cosolute conditions, sfGFP and the −18 variant formed a gel or phase separated at ~10 mg/ml. Under conditions that screen surface charges, including formulations with high histidine or high NaCl concentrations, all three variants attained concentrations up to 250 mg/ml with moderate viscosities. Moreover, all three variants exhibited very similar viscosity-concentration profiles over this range. This effect was not mimicked by high sugar concentrations that exert excluded volume effects without shielding charge. Collectively, these data demonstrate that charge shielding not only neutralizes long-range electrostatic interactions but also, surprisingly, short-range electrostatic effects due to surface charge anisotropy. This work shows that supercharged sfGFP behavior under high ionic strength is largely determined by particle geometry, a conclusion that is supported by colloid models and may be applicable to pharmaceutically-relevant proteins.

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Section: Introductionmentioning

confidence: 99%

Charge Shielding Prevents Aggregation of Supercharged GFP Variants at High Protein Concentration

et al. 2017

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“…36,55–59 These models have provided valuable insight into the effect of specific interactions on protein liquid–liquid phase separation 60,61 and crystallization. 62,63 Likewise, they have been fundamental to understanding and controlling the rich range of self-assembled, well-defined structures that patchy colloids can form.…”

Section: Introductionmentioning

confidence: 99%

“…67–70 By contrast, less attention has been given to particles that exhibit specific, long-range repulsive and attractive interactions such as those in zwitterionic particles. Examples of models for charged patchy particles include those for evaluating the effect of the charge pattern on protein–protein/solvent interactions 59,71 and the nucleation of protein crystals, 72 as well as those for studying the self-assembly and gelation of both embedded and induced dipolar colloids. 73–75 Notably, recent studies on particles with simple charge patterns, termed inverse patchy colloids, 66,76,77 have illustrated the role of long-range attractions/repulsions on tuning the equilibrium between phases of fluid, solid, and colloidal monolayers.…”

Section: Introductionmentioning

confidence: 99%

Effect of the surface charge distribution on the fluid phase behavior of charged colloids and proteins

Blanco

Shen

2016

The Journal of Chemical Physics

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A generic but simple model is presented to evaluate the effect of the heterogeneous surface charge distribution of proteins and zwitterionic nanoparticles on their thermodynamic phase behavior. By considering surface charges as continuous “patches”, the rich set of surface patterns that is embedded in proteins and charged patchy particles can readily be described. This model is used to study the fluid phase separation of charged particles where the screening length is of the same order of magnitude as the particle size. In particular, two types of charged particles are studied: dipolar fluids and protein-like fluids. The former represents the simplest case of zwitterionic particles, whose charge distribution can be described by their dipole moment. The latter system corresponds to molecules/particles with complex surface charge arrangements such as those found in biomolecules. The results for both systems suggest a relation between the critical region, the strength of the interparticle interactions, and the arrangement of charged patches, where the critical temperature is strongly correlated to the magnitude of the dipole moment. Additionally, competition between attractive and repulsive charge–charge interactions seems to be related to the formation of fluctuating clusters in the dilute phase of dipolar fluids, as well as to the broadening of the binodal curve in protein-like fluids. Finally, a variety of self-assembled architectures are detected for dipolar fluids upon small changes to the charge distribution, providing the groundwork for studying the self-assembly of charged patchy particles.

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“…The first one originates from the presence of a localized distribution of charges defining an electrostatic patch on the protein surface. Depending on relative orientations, the charge distributions in the patches on the protein molecules can become complementary, thereby leading to an attractive electrostatic force (5). This anisotropic force is short ranged and is hereafter referred to as the electrostatic adhesive force.…”

mentioning

confidence: 99%

Self-association of a highly charged arginine-rich cell-penetrating peptide

Tesei

Vazdar

Jensen

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Small-angle X-ray scattering (SAXS) measurements reveal a striking difference in intermolecular interactions between two short highly charged peptides-deca-arginine (R10) and deca-lysine (K10). Comparison of SAXS curves at high and low salt concentration shows that R10 self-associates, while interactions between K10 chains are purely repulsive. The self-association of R10 is stronger at lower ionic strengths, indicating that the attraction between R10 molecules has an important electrostatic component. SAXS data are complemented by NMR measurements and potentials of mean force between the peptides, calculated by means of umbrella-sampling molecular dynamics (MD) simulations. All-atom MD simulations elucidate the origin of the R10-R10 attraction by providing structural information on the dimeric state. The last two C-terminal residues of R10 constitute an adhesive patch formed by stacking of the side chains of two arginine residues and by salt bridges formed between the like-charge ion pair and the C-terminal carboxyl groups. A statistical analysis of the Protein Data Bank reveals that this mode of interaction is a common feature in proteins.cell-penetrating peptide | self-association | MD simulations | SAXS | NMR R ecent studies focusing on interactions of charged proteins in electrolyte solutions have highlighted the interplay of two counteracting electrostatic forces (1-4). The first one originates from the presence of a localized distribution of charges defining an electrostatic patch on the protein surface. Depending on relative orientations, the charge distributions in the patches on the protein molecules can become complementary, thereby leading to an attractive electrostatic force (5). This anisotropic force is short ranged and is hereafter referred to as the electrostatic adhesive force. The other force is the double-layer force arising from the Coulombic repulsion between like-charged molecules in the electrolyte medium. Both electrostatic adhesive and double-layer forces are weakened by the presence of salt in the solution. As a nontrivial consequence, the propensity of the proteins to aggregate is heightened at low-to-intermediate ionic strengths (1)(2)(3)6). This is because of lowering of Coulombic repulsion due to salt screening of the net charge of the protein, in conjunction with the presence of the adhesive force, which operates at shorter distances and is therefore less efficiently screened.In this work, the competition between electrostatic adhesive and double-layer forces, together with a chemically specific like-charge attraction between guanidinium (Gdm + ) side-chain groups, is reported for solutions of a small highly charged peptide. Observation of the complex aggregation behavior for a relatively simple molecule is substantiated by a comparative investigation of deca-arginine (R10) and deca-lysine (K10), in high and low ionic strength solutions, conducted using small-angle X-ray scattering (SAXS) measurements, all-atom molecular dynamics (MD) simulations, and 1 H-13 C heteronuclear single...

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Role of Anisotropic Interactions for Proteins and Patchy Nanoparticles

Cited by 55 publications

References 74 publications

Charge Shielding Prevents Aggregation of Supercharged GFP Variants at High Protein Concentration

Charge Shielding Prevents Aggregation of Supercharged GFP Variants at High Protein Concentration

Effect of the surface charge distribution on the fluid phase behavior of charged colloids and proteins

Self-association of a highly charged arginine-rich cell-penetrating peptide

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