Elena Chernokalskaya

Development of a Univariate Membrane-Based Mid-Infrared Method for Protein Quantitation and Total Lipid Content Analysis of Biological Samples

Biological samples present a range of complexities from homogeneous purified protein to multicomponent mixtures. Accurate qualification of such samples is paramount to downstream applications. We describe the development of an MIR spectroscopy-based analytical method offering simultaneous protein quantitation (0.25–5 mg/mL) and analysis of total lipid or detergent species, as well as the identification of other biomolecules present in biological samples. The method utilizes a hydrophilic PTFE membrane engineered for presentation of aqueous samples in a dried format compatible with fast infrared analysis. Unlike classical quantification techniques, the reported method is amino acid sequence independent and thus applicable to complex samples of unknown composition. By comparison to existing platforms, this MIR-based method enables direct quantification using minimal sample volume (2 µL); it is well-suited where repeat access and limited sample size are critical parameters. Further, accurate results can be derived without specialized training or knowledge of IR spectroscopy. Overall, the simplified application and analysis system provides a more cost-effective alternative to high-throughput IR systems for research laboratories with minimal throughput demands. In summary, the MIR-based system provides a viable alternative to current protein quantitation methods; it also uniquely offers simultaneous qualification of other components, notably lipids and detergents.

Filtration as a Sample Preparation Technique Prior to Mass Spectrometry: Selecting the Right Filtration Device

Filtration is one of the simplest forms of sample preparation prior to any analysis including mass spectrometry. Being the simplest, filtration is also one of the most neglected steps during optimization of sample preparation which can lead to problems in downstream analysis. This report provides guidelines towards selection of the right filtration device for the application. The factors which decide choice of filter are sample size, chemical characteristics of sample, particle load and downstream analytical technique. This report also provides useful information regarding extractables and analyte binding and ways to minimize both of these.