Efficient data acquisition with three-channel centerpieces in sedimentation velocity

An automated interface for sedimentation velocity analysis in SEDFIT

Sedimentation velocity analytical ultracentrifugation (SV-AUC) is an indispensable tool for the study of particle size distributions in biopharmaceutical industry, for example, to characterize protein therapeutics and vaccine products. In particular, the diffusion-deconvoluted sedimentation coefficient distribution analysis, in the software SEDFIT, has found widespread applications due to its relatively high resolution and sensitivity. However, a lack of available software compatible with Good Manufacturing Practices (GMP) has hampered the use of SV-AUC in this regulatory environment. To address this, we have created an interface for SEDFIT so that it can serve as an automatically spawned module with controlled data input through command line parameters and output of key results in files. The interface can be integrated in custom GMP compatible software, and in scripts that provide documentation and meta-analyses for replicate or related samples, for example, to streamline analysis of large families of experimental data, such as binding isotherm analyses in the study of protein interactions. To test and demonstrate this approach we provide a MATLAB script mlSEDFIT.

Analytical Ultracentrifugation (AUC): An Overview of the Application of Fluorescence and Absorbance AUC to the Study of Biological Macromolecules

The biochemical and biophysical investigation of proteins, nucleic acids, and the assemblies that they form yields essential information to understand complex systems. Analytical ultracentrifugation (AUC) represents a broadly applicable and information‐rich method for investigating macromolecular characteristics such as size, shape, stoichiometry, and binding properties, all in the true solution‐state environment that is lacking in most orthogonal methods. Despite this, AUC remains underutilized relative to its capabilities and potential in the fields of biochemistry and molecular biology. Although there has been a rapid development of computing power and AUC analysis tools in this millennium, fewer advancements have occurred in development of new applications of the technique, leaving these powerful instruments underappreciated and underused in many research institutes. With AUC previously limited to absorbance and Rayleigh interference optics, the addition of fluorescence detection systems has greatly enhanced the applicability of AUC to macromolecular systems that are traditionally difficult to characterize. This overview provides a resource for novices, highlighting the potential of AUC and encouraging its use in their research, as well as for current users, who may benefit from our experience. We discuss the strengths of fluorescence‐detected AUC and demonstrate the power of even simple AUC experiments to answer practical and fundamental questions about biophysical properties of macromolecular assemblies. We address the development and utility of AUC, explore experimental design considerations, present case studies investigating properties of biological macromolecules that are of common interest to researchers, and review popular analysis approaches. © 2020 The Authors.

Determining the Stoichiometry of a Protein-Polymer Conjugate Using Multisignal Sedimentation Velocity Analytical Ultracentrifugation

Advances in polymer science have broadened the applications of protein-polymer conjugates as biopharmaceuticals and biotechnology reagents. The complex nature of these conjugates makes characterization challenging. Here, we describe the use of multisignal sedimentation velocity analytical ultracentrifugation to measure the polymer-to-protein ratio. To demonstrate the principle, we applied this approach to a series of antibody-drug conjugates with different polymer-to-protein ratios and various degrees of heterogeneity, and validated results with orthogonal analytical techniques. We found that multisignal sedimentation velocity can provide accurate information on key attributes including polymer-to-protein ratio, which is important for maximizing the therapeutic potential of future protein-polymer conjugates.

Open-source autosampler for elemental and isotopic analyses of solids

Elemental and isotopic analyses are performed using elemental analyzers, and are widely employed for diverse scientific fields. An elemental analyzer is typically equipped with an autosampler. Here we present an open-source autosampler for elemental and isotopic analysis of solid samples. The autosampler consists of 1) a sampling table, on which a carousel pushes samples inside an orifice, and 2) a purging pipe, placed directly beneath the orifice, where the sample is purged off surrounding air, and then delivered to the reaction tube. The action of the purging pipe ensured that air contamination, an issue for the analysis of some elements like nitrogen and oxygen, was negligible, and results for elemental and isotopic composition of nitrogen and carbon were inside specs. Compared to commercial alternatives, the autosampler presented here has the advantages of lower cost to build and maintain, universal compatibility with instruments from different manufacturers, capacity do deal with bulky samples, capacity for a larger number of samples in a single run, and no necessity for time-consuming purging in-between sample loading. The autosampler could potentially also be employed for the analyses of other elements (e.g. oxygen, hydrogen and sulfur) because they are performed using similar equipment.

Resuspending samples in analytical ultracentrifugation

In analytical ultracentrifugation it is often very useful to resuspend samples in situ after sedimentation experiments for further investigation. This can be achieved by manually subjecting the entire sample cell assembly to gentle motion that causes the air bubble in the sample compartment to repeatedly move through the solution and thereby cause convection. Here we describe a cell mixing device that can accomplish the same through axial rotation and slow rocking motion. This cell mixer is low-cost, open-source, and can be easily assembled from readily available components. It can efficiently mix multiple sample cells side-by-side and may be used with various centerpiece designs.