Enrichment of adeno-associated virus serotype 5 full capsids by anion exchange chromatography with dual salt elution gradients.

Adeno-associated virus-based gene therapies have demonstrated substantial therapeutic benefit for the treatment of genetic disorders. In manufacturing processes, viral capsids are produced with and without the encapsidated gene of interest. Capsids devoid of the gene of interest, or "empty" capsids, represent a product-related impurity. As a result, a robust and scalable method to enrich full capsids is crucial to provide patients with as much potentially active product as possible. Anion exchange chromatography has emerged as a highly utilized method for full capsid enrichment across many serotypes due to its ease of use, robustness, and scalability. However, achieving sufficient resolution between the full and empty capsids is not trivial. In this work, anion exchange chromatography was used to achieve empty and full capsid resolution for adeno-associated virus serotype 5. A salt gradient screen of multiple salts with varied valency and Hofmeister series properties was performed to determine optimal peak resolution and aggregate reduction. Dual salt effects were evaluated on the same product and process attributes to identify any synergies with the use of mixed ion gradients. The modified process provided as high as ≥75% AAV5 full capsids (≥3-fold enrichment based on the percent full in the feed stream) with near baseline separation of empty capsids and achieved an overall vector genome step yield of >65%.

Observation of small cluster formation in concentrated monoclonal antibody solutions and its implications to solution viscosity.

Monoclonal antibodies (mAbs) are a major class of biopharmaceuticals. It is hypothesized that some concentrated mAb solutions exhibit formation of a solution phase consisting of reversibly self-associated aggregates (or reversible clusters), which is speculated to be responsible for their distinct solution properties. Here, we report direct observation of reversible clusters in concentrated solutions of mAbs using neutron spin echo. Specifically, a stable mAb solution is studied across a transition from dispersed monomers in dilute solution to clustered states at more concentrated conditions, where clusters of a preferred size are observed. Once mAb clusters have formed, their size, in contrast to that observed in typical globular protein solutions, is observed to remain nearly constant over a wide range of concentrations. Our results not only conclusively establish a clear relationship between the undesirable high viscosity of some mAb solutions and the formation of reversible clusters with extended open structures, but also directly observe self-assembled mAb protein clusters of preferred small finite size similar to that in micelle formation that dominate the properties of concentrated mAb solutions.

Small-angle neutron scattering characterization of monoclonal antibody conformations and interactions at high concentrations.

Small-angle neutron scattering (SANS) is used to probe the solution structure of two protein therapeutics (monoclonal antibodies 1 and 2 (MAb1 and MAb2)) and their protein-protein interaction (PPI) at high concentrations. These MAbs differ by small sequence alterations in the complementarity-determining region but show very large differences in solution viscosity. The analyses of SANS patterns as a function of different solution conditions suggest that the average intramolecular structure of both MAbs in solution is not significantly altered over the studied protein concentrations and experimental conditions. Even though a strong repulsive interaction is expected for both MAbs due to their net charges and low solvent ionic strength, analysis of the SANS data shows that the effective PPI for MAb1 is dominated by a very strong attraction at small volume fraction that becomes negligible at large concentrations. The MAb1 PPI cannot be modeled simply by a spherically symmetric central forces model. It is proposed that an anisotropic attraction strongly affects the local interprotein structure and leads to an anomalously large viscosity of concentrated MAb1 solutions. Conversely, MAb2 displays a repulsive interaction potential throughout the concentration series probed and a comparatively small solution viscosity.

Shear-induced metastable states of end-grafted polystyrene.

The in situ molecular scale response of end-grafted polystyrene to shear against a deuterated polystyrene melt was investigated with neutron reflectometry. The derived grafted polystyrene density profiles showed that the grafted polystyrene was retained on the quartz wafer during the measurements. The profiles suggested that the end-grafted polystyrene response to shear results in a series of metastable states, rather than equilibrium states assumed in the current theory. Except for some possible extension and/or contraction of the grafted polystyrene with shear, there was no obvious correlation between the grafted polymer structure and the shear thinning behavior observed in these samples.

The Los Alamos Neutron Science Center neutron rheometer in the cone and plate geometry to examine tethered polymers/polymer melt interfaces via neutron reflectivity.

Although several other neutron rheometers have been built to study soft matter under nonequilibrium conditions, none of them have the ability to measure the structure and behavior of the polymeric interfacial regions in highly viscous polymer melts which require high torques/high strain rates and high temperatures. A neutron rheometer in the cone and plate geometry has been constructed at the Los Alamos Neutron Science Center to rectify this lack of experimental instrumentation. It is also the first-of-its-kind to perform neutron reflectivity studies concurrently with rheological measurements. The details of both the development and testing of the Los Alamos Neutron Science Center neutron rheometer in the cone and plate configuration are described. Proof of principle neutron reflectivity results of end-grafted polystyrene against an identical melt under shear are presented, showing qualitatively that the structural attributes of the end-grafted polymer change when exposed to shear.

The Couette configuration of the Los Alamos Neutron Science Center neutron rheometer for the investigation of polymers in the bulk via small-angle neutron scattering.

A neutron rheometer in the Couette geometry has been built at the Los Alamos Neutron Science Center to examine the molecular steady-state and dynamic responses of entangled polymeric materials in the bulk under the application of shear stress via small-angle neutron scattering. Although similar neutron rheometers have been fabricated elsewhere, this new design operates under the extreme conditions required for measuring the structure and behavior of high molecular weight polymer melts. Specifically, the rheometer achieves high torques (200 N m) and shear rates (865 s(-1)) simultaneously, never before attainable with other neutron rheometers at temperatures up to 240 degrees C under an inert gas environment. The design of the instrument is such that relatively small sample sizes are required. The testing of the Los Alamos Neutron Science Center Neutron Rheometer in the Couette design both as a rheometer and in the small-angle neutron optical configuration on highly viscous polystyrene is presented. The observed anisotropic neutron scattering pattern of the polystyrene melt at a molecular weight above entanglement provides evidence that the conformation of the polymer chains are elongated in the direction of the melt flow, in agreement with the current theories concerning linear polymers in the bulk.

5-Aminonaphthalene-1-sulfonic acid and its manganese, nickel and cobalt salts.

5-Ammonionaphthalene-1-sulfonate monohydrate, C10H9NO3S x H2O, contains layers of zwitterionic molecules with the acidic sulfonic acid H atom transferred to the amine N atom. Within each layer, the charged groups (NH3(+) and SO3(-)) are directed to the surface of the layer and are inverted on adjacent molecules. The naphthalene rings in a given layer are all parallel. The layers are held together by N-H...O and O-H...O hydrogen bonds involving the ammonium, sulfonate and water atoms. The Mn and Ni salts crystallize as fully aquated trihydrates, namely hexaaquamanagnese(II) bis(5-aminonaphthalene-1-sulfonate) trihydrate, [Mn(H2O)6](C10H8NO3S)2 x 3 H2O, (II), and hexaaquanickel(II) bis(5-aminonaphthalene-1-sulfonate) trihydrate, [Ni(H2O)6](C10H8NO3S)2 x 3 H2O, (III), in which layers of hexaaquametal(II) complexes alternate with layers of 5-aminonaphthalene-1-sulfonate anions. The cations reside on twofold rotation axes and display regular octahedral coordination. The additional water molecules are found in the inorganic layer between the complex cations, one on a twofold axis and one in a general position. The anions are packed in a herring-bone arrangement with the rings of neighboring rows of anions approximately 43 degrees out of parallel. The NH2 and SO3(-) groups line the surface of the layer, where they participate in numerous hydrogen bonds with the water molecules. Whereas the Mn and Ni salts are orthorhombic, the Co salt, hexaaquacobalt(II) bis(5-aminonaphthalene-1-sulfonate) dihydrate, [Co(H2O)6](C10H8NO3S)2 x 2 H2O, (IV), crystallizes in a triclinic cell of similar dimensions, with the cations situated on centers of inversion. The overall packing is very similar to that of the Mn and Ni salts, with the main differences being the absence of the solvent water molecule on the special position and subtle modifications in the positioning of the anions within their layers. This series of salts is compared with those of the same metals with the 5-aminonaphthalene-2-sulfonate and 4-aminonaphthalene-1-sulfonate isomers, allowing for similarities and differences in packing to be discussed on the basis of the differing substitution of the naphthalene ring and, in some cases, differing degrees of hydration.

Binding of genistein to the estrogen receptor based on an experimental electron density study.

In a continuing effort to determine a relationship between the biological function and the electronic properties of steroidal and nonsteroidal estrogens by analysis of the submolecular properties, an experimental charge density study has been pursued on the nonsteroidal phytoestrogen, genistein. X-ray diffraction data were obtained using a Rigaku R-Axis Rapid high-power rotating anode diffractometer with a curved image plate detector at 20(1) K. The total electron density was modeled using the Hansen-Coppens multipole model. Genistein packs in puckered sheets characterized by intra- and intermolecular hydrogen bonds while weaker intermolecular hydrogen bonds (O...H-C) exist between the sheets. A topological analysis of the electron density of genistein was then completed to characterize all covalent bonds, three O...H-O and four O...H-C intermolecular hydrogen bonds. Two O...H-O hydrogen bonds are incipient (partially covalent) type bonds, while the other O...H-O hydrogen bond and O...H-C hydrogen bonds are of the pure closed-shell interaction type. In addition, two intermolecular H...H interactions have also been characterized from the topology of the electron density. The binding of genistein to the estrogen receptor is discussed in terms of the electrostatic potential derived from the electron density distribution.

2,3,10,11-Tetrathiatricyclo[10.4.0.0(4,9)]hexadeca-4,6,8,12,14,16-hexaene (precession camera versus CCD).

The title compound, C(12)H(8)S(4), has crystallographic \overline{1} symmetry, the benzene groups thus being anti with respect to the plane of the four S atoms. The S-S and C-S bond lengths of the sulfur-carbon eight-membered ring were found to be similar to those in other structures containing such sulfur-carbon rings. There is evidence for pi-pi interactions between the aromatic rings of neighboring molecules, linking them into sheets.