Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session J34: Focus Session: Charged Colloids with Short-Range Attractions II |
Hide Abstracts |
Sponsoring Units: DPOLY DCMP DBIO Chair: Frank Schreiber, Institut fuer Angewandte Physik, Universitaet Tuebingen Room: 342 |
Tuesday, March 19, 2013 2:30PM - 3:06PM |
J34.00001: DILLON MEDAL BREAK
|
Tuesday, March 19, 2013 3:06PM - 3:42PM |
J34.00002: Concentrated dispersions of therapeutic proteins Invited Speaker: Thomas Truskett In this talk, recent experiments characterizing highly concentrated dispersions of therapeutic proteins, which are of interest for at-home treatment of disease via subcutaneous injection, are discussed. In particular, evidence for protein nanocluster formation in these systems is explored. The roles of dispersion composition, pH, and experimental pathway are elucidated for several protein systems. Observed correlations between nanocluster properties, solution viscosity, and protein stability/activity, as well as prospective theoretical explanations for these behaviors, are highlighted. [Preview Abstract] |
Tuesday, March 19, 2013 3:42PM - 3:54PM |
J34.00003: Transition from monomeric phase to dynamic cluster phase in lysozyme protein solutions Yun Liu, Peter Falus, Lionel Porcar, Emiliano Fratini, Wei-Ren Chen, Antonio Faraone, Kunlun Hong, Piero Baglioni Intermediate range order (IRO) has been recently observed in lysozyme solution that is caused by a combination of a short-range attraction and long-range repulsion. At very high concentration, there is observed cluster formation in lysozyme solutions that is one type of IRO structures. Here, we investigate the temperature effect on the dynamic cluster formation and identify the transition concentration from a monomeric protein phase to a cluster phase. The normalized short-time self-diffusion coefficient is not affected by changing attraction strength at the concentration of about 10{\%} mass fraction, indicating that the system is still dominated by monomeric protein phase. However, at high concentrations, the average self-diffusion coefficient is sensitive to the change of short-range attraction strength, which is interpreted due to the growth of the size of dynamic clusters in solution. The transition concentration from dominating monomeric phase to dynamic cluster phase is estimated to be around 14 {\%} mass fraction. [Preview Abstract] |
Tuesday, March 19, 2013 3:54PM - 4:06PM |
J34.00004: Langevin Dynamics Simulation of DNA Condensation Induced by Nanoparticles in Confinement Guo-Jun Liao, Yeng-Long Chen We study nanoparticle-induced DNA condensation in a confined suspension of dilute DNA molecules and ideal nanoparticles (NPs) with Langevin dynamics simulation. DNA condensation has been observed in a solution of dilute DNA molecules (persistence length $P \approx 50$ nm) and high concentration of electrostatically neutral NPs (diameter $d \approx$ 5 to 35 nm) in recent experimental measurements. It is believed that NPs entropically induce an attraction between DNA segments. For NPs much smaller than $P$, a DNA molecule can be considered as a chain of connected rods, and the NP-induced depletion attraction between DNA segments can be regarded as rod-rod attraction. Thus, the strength of the depletion attraction is proportional to the number of persistence length in a DNA chain, $N=L/P$, the depletion volume $NP^2d$, and the NP density $\rho$, where $L$ is the DNA contour length. In slit confinement, DNA conformation changes are much different from in an unconfined environment. The height of the slit relative to the NPs size ($H/d$) strongly influences the DNA conformation. For $H/d \approx 1$, DNA size decreases monotonically as $\rho$ increases, while non-monotonic dependence happens for $H/d \approx 5$, due to the competition between DNA-DNA, DNA-NP, and NP-wall interactions. [Preview Abstract] |
Tuesday, March 19, 2013 4:06PM - 4:18PM |
J34.00005: Small-Angle Neutron Scattering and Neutron Spin Echo Characterization of Monoclonal Antibody Self-Associations at High Concentrations Eric Yearley, Isidro (Dan) Zarraga, Paul (Doug) Godfrin, Tatiana Perevozchikova, Norman Wagner, Yun Liu Concentrated therapeutic protein formulations offer numerous delivery and stability challenges. In particular, it has been found that several therapeutic proteins exhibit a large increase in viscosity as a function of concentration that may be dependent on the protein-protein interactions. Small-Angle Neutron Scattering (SANS) and Neutron Spin Echo (NSE) investigations have been performed to probe the protein-protein interactions and diffusive properties of highly concentrated MAbs. The SANS data demonstrate that the inter-particle interactions for a highly viscous MAb at high concentrations (MAb1) are highly attractive, anisotropic and change significantly with concentration while the viscosity and interactions do not differ considerably for MAb2. The NSE results furthermore indicate that MAb1 and MAb2 have strong concentration dependencies of dynamics at high Q that are correlated to the translational motion of the proteins. Finally, it has also been revealed that the individual MAb1 proteins form small clusters at high concentrations in contrast to the MAb2 proteins, which are well-dispersed. It is proposed that the formation of these clusters is the primary cause of the dramatic increase in viscosity of MAb1 in crowded or concentrated environments. [Preview Abstract] |
Tuesday, March 19, 2013 4:18PM - 4:30PM |
J34.00006: The Structural Properties and Stability of Monoclonal Antibodies at Freezing Conditions Tatiana Perevozchikova, Isidro Zarraga, Thomas Scherer, Norman Wagner, Yun Liu Monoclonal Antibodies (MAb) have become a crucial therapeutic agent in a number of anti-cancer treatments. Due to the inherent unstable nature of proteins in an aqueous formulation, a freeze-drying method has been developed to maintain long-term stability of biotherapeutics. The microstructural changes in Mabs during freezing, however, remain not fully described, and it was proposed that the formed morphology of freeze drying samples could affect the final product quality after reconstitution. Furthermore, it is well known that proteins tend to aggregate during the freezing process if a careful processing procedure is not formulated. Small Angle Neutron Scattering (SANS) is a powerful tool to investigate the structural properties and interactions of Mabs during various stages of lyophilization in situ. Here we present the SANS results of freeze-thaw studies on two MAbs at several different freezing temperatures. While the chosen proteins share a significant sequence homology, their freezing properties are found to be strikingly distinctive. We also show the effect of excipients, concentration and quenching speed on the final morphology of the frozen samples. These findings provide critical information for more effective lyophilization schemes for therapeutic proteins, as well as increase our understanding on structural properties of proteins under cryogenic conditions. [Preview Abstract] |
Tuesday, March 19, 2013 4:30PM - 4:42PM |
J34.00007: Shear-Dependent Interactions in Rheology Modifier (RM)-Latex Suspensions Tirtha Chatterjee, Alan I. Nakatani, Antony K. VanDyk Paint viscosity, under shear is governed by its shear-induced structure which in turn controls the application properties. The micro and macroscopic structure of the RM-latex combinations under shear is central to understand paint application behavior. Using in-situ shear-small-angle neutron scattering (shear-SANS) the RM-latex structure has been studied. All studies reported here are performed on acrylic-based latex with different hydrophobically modified ethoxylated urethane (HEUR) RM varying in their hydrophobe density/chain. At a quiescent condition, latex and RM form a spherical core-shell structure, with latex particles being the core and adsorbed RMs on the surface forming the shell. The shell thickness decreases with increasing RM hydrophobe density/chain. Under shear, the solvent (D2O/H2O) is squeezed out (hydrodynamic squeezing) from the swollen RM chains and the shell structure becomes denser and \textit{anisotropic} due to differing degrees of compression along the flow and vorticity directions. An effective shear-dependent latex-RM hydrodynamic volume fraction has been calculated using SANS structural data. High shear viscosity calculated on the basis of effective hydrodynamic volume using existing models do not match with the experimental data. This suggests the existence of RM molecule mediated interactions even at high shear rate. [Preview Abstract] |
Tuesday, March 19, 2013 4:42PM - 4:54PM |
J34.00008: Multi-body effects in Charged Colloids - Polyelectrolyte systems Victor Pryamitsyn, Venkat Ganesan Multibody effects upon the electrostatic interaction between particles, polyelectrolyte molecules and monovalent ions were analyzed within Poisson-Boltzmann approximation. The numerical self-consistent field (SCF) theory for a polymer - nanoparticles systems was developed for a mixture of quenched polyelectrolytes and charged and uncharged particles and the pseudo-spectral method was used to solve polymer SCF equations in three dimensions within the Grand Canonical Ensemble for polymer and ions. A calculation of the free energies of a single particle and of two particles in polyelectrolyte solutions allowed us to calculate respectively the particle insertion free energy and particle-particle interactions as a function of the properties of solution, polymer-particle interaction and particle size. By explicitly calculating the free energy of three particles after subtraction of the contributions from two-body interaction allowed us to calculate effective contribution of 3-body particle-particle interactions in polyelectrolyte -particles systems. We have found that the polyelectrolyte mediated two body interactions are repulsive for the larger particle-particle distances and lower polymer concentrations. Interestingly, such an electrostatic repulsion exists even if particles have [Preview Abstract] |
Tuesday, March 19, 2013 4:54PM - 5:06PM |
J34.00009: A density functional approach to model highly charged spherical colloids in electrolyte mixtures Bharat Medasani, Zaven Ovanesyan, Marcelo Marucho We present a classical density functional (DFT) approach to study the effects of ion size asymmetry, ion-ion correlation and solvent excluded volume on the structural and thermodynamic properties of strongly interacting charged systems. The hard sphere correlation effects are modeled non-perturbatively with weighted density approximation, where as electrostatic correlations are modeled perturbatively within the mean spherical approximation. The present DFT approach is able to describe macro-ions in electrolytes comprising neutral hard sphere mimicking water molecules and ions with dissimilar valence and realistic sizes and densities. We applied the theory to study spherical electric double layers and obtained results in good agreement with simulations. We calculated ion profiles, integrated charge, mean electrostatic potential, ionic coordination number, zeta potential, and inverse differential capacity at different conditions. For higher surface charge on macromolecule, charge inversion is noticed and when the counter-ions are bigger than co-ions, surface charge amplification is observed. Layering and screening effects are more pronounced when water molecules are explicitly considered. This work has potential applications in bio-electrostatics and colloidal engineering. [Preview Abstract] |
Tuesday, March 19, 2013 5:06PM - 5:18PM |
J34.00010: Measuring inter-nucleosome interactions and the roles of histone tails Steven Howell, Kurt Andresen, Isabel Jimenez-Useche, Chongli Yuan, Xiangyun Qiu Nucleosome is the first level of genome organization and regulation in eukaryotes, where negatively charged DNA is wrapped around positively charged histone proteins. Being a DNA-protein complex of biological origin, nucleosome is also a model multi-phasic nanoparticle with heterogeneous charge distributions and brush-like flexible tails of the histone proteins. In solutions of nucleosomes, electrostatic forces dominate inter-nucleosome interactions at long range while specific contacts, in particular the flexible histone tails, guides short range interactions. We have thus quantified how the ions from salts (KCl, MgCl2) modulate the inter-nucleosome pair potential by modeling the total small angle x-ray scattering profiles. We additionally elucidated the individual role of the charged tails of histones H3 and H4. We found that measured effective changes at low salt concentrations are about 1/5th of theoretically predicted renormalized charges and that H4 tail deletion suppresses the attraction at high salt concentrations to a larger extent than H3 tail deletion. [Preview Abstract] |
Tuesday, March 19, 2013 5:18PM - 5:30PM |
J34.00011: Multivalent Colloids through DNA Patchy Particles Yufeng Wang, Yu Wang, Dana Breed, Vinothan Manoharan, Lang Feng, Andrew Hollingsworth, Marcus Weck, David Pine We demonstrate a general method for creating the colloidal analogs of atoms with multiple valences: colloidal particles with chemically functionalized patches that can form highly directional specific bonds. The valences of these ``colloidal atoms'' possess all the common symmetries characteristic of hybridized atomic orbitals, including sp, sp$^{2}$, sp$^{3}$, sp$^{3}$d, sp$^{3}$d$^{2}$, and sp$^{3}$d$^{3}$. The chemical functionality of the patches is programmable and specific using DNA with single-stranded sticky ends, thereby creating colloidal atoms from which different kinds of ``colloidal molecules'' can be assembled, including the colloidal analogs of carbon dioxide and tetrahedrally coordinated methane. The bonds between these new colloidal atoms are highly directional and fully reversible with temperature. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700