Characterizing the Reproducibility of a Protein Profiling Method for the Analysis of Mouse Bronchoalveolar Lavage Fluid

Advances in proteomic techniques for biomarker discovery in COPD

Chronic obstructive pulmonary disease (COPD) is a disorder characterized by chronic inflammation of the lung with airflow obstruction and progressive deterioration of pulmonary function. The need to discover and validate biomarkers as prognostic tools of development and progression of the disease has received further support with the advent of proteomic techniques. Liquid chromatography-mass spectrometry (LC/MS) and gel electrophoresis-mass spectrometry (2-DE/MS) have been applied to investigate the proteome of a number of lung-origin samples, including sputum, bronchoalveolar lavage fluid, exhaled-breath condensate, cells and biopsies from COPD patients. In particular, 2-DE and MS are the main proteomic approaches with 2-DE presenting the major approach for quantitative proteomics. The molecules identified as potential biomarkers of COPD may represent a preliminary step for better comprehension of the mechanisms involved in the onset/progression of the disease.

Optimal preparation methods for automated matrix-assisted laser desorption/ionization time-of-flight mass spectrometry profiling of low molecular weight proteins and peptides

Mass spectrometry (MS) profiling of the proteome and peptidome for disease-associated patterns is a new concept in clinical diagnostics. The technique, however, is highly sensitive to external sources of variation leading to potentially unacceptable numbers of false positive and false negative results. Before MS profiling can be confidently implemented in a medical setting, standard experimental methods must be developed that minimize technical variance. Past studies of variance have focused largely on pre-analytical variation (i.e., sample collection, handling, etc.). Here, we examined how factors at the analytical stage including the matrix and solid-phase extraction influence MS profiling. Firstly, a standard peptide/protein sample was measured automatically by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS across five consecutive days using two different preparation methods, dried droplet and sample/matrix, of four types of matrix: alpha-cyano-4-hydroxycinnamic acid (HCCA), sinapinic acid (SA), 2,5-dihydroxybenzoic acid (DHB) and 2,5-dihydroxyacetophenone (DHAP). The results indicated that the matrix preparation greatly influenced a number of key parameters of the spectra including repeatability (within-day variability), reproducibility (inter-day variability), resolution, signal strength, background intensity and detectability. Secondly, an investigation into the variance associated with C8 magnetic bead extraction of the standard sample prior to automated MS profiling demonstrated that the process did not adversely affect these same parameters. In fact, the spectra were generally more robust following extraction. Thirdly, the best performing matrix preparations were evaluated using C8 magnetic bead extracted human plasma. We conclude that the DHAP prepared according to the dried-droplet method is the most appropriate matrix to use when performing automated MS profiling.