Step by step preparation of urine samples for in-Solution, gel-free proteomic studies, suitable for MALDI TOF MS and LCMS QTOF MS

Two-dimensional electrophoresis is an established method for isolating and separating proteins for proteomic analysis and identification of proteins. However, it requires a lot of optimization and it suffers from some ongoing concerns regarding quantitative reproducibility and limitations on its ability to study certain class of proteins. We propose a simpler method in preparing urine samples from acute melioidosis patients for in-solution proteomics using liquid chromatography coupled with mass spectrometry quadrupole time of flight (LCMS-QTOF MS) or matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). This method is relatively easier than 2-dimensional electrophoresis, affordable, reproducible, can be performed in less equipped laboratories for transport to specialized centers for proteomic studies and bioinformatic analysis

Optimized preparation of urine samples from acute melioidosis patients for in-solution proteomic studies using LCMS QTOF or MALDI TOF MS

Introduction: Investigation of urine proteome in patients with acute melioidosis may reveal potential disease markers, from either bacterial or human proteins. We used an in-solution gel-free method instead of 2-DE to detect human and Burkholderia pseudomallei proteins in urine of patients with acute melioidosis. Here, we propose a simpler, economical method for preparing urine samples directly from melioidosis patients, for in-solution proteomic analysis using LCMS-QTOF MS/MS or MALDI-TOF MS/MS. Material and Methods: We adapted an acetone-TCA based protein precipitation method with LCMS-QTOF MS to detect the B. pseudomallei proteins directly from urine of acute melioidosis patients (culture positive and negative). This process involves protein precipitation, desalting, trypsin digestion, and optimization for the mass spectrometry. Results: A total of 3,866 human peptides were detected across 11 urine samples from clinically suspected acute melioidosis patients. Among them were three Burkholderia specific proteins detected in 75% of culture positive samples. Large amounts of acute phase proteins, cell mediated immunity proteins, complement pathway proteins and inflammatory mediators were seen upon gene ontology (GO) annotation and GO enrichment analysis. Conclusions: This simple in-solution sample preparation method can be replicated easily for LCMS/MS-QTOF and MALDI-TOF proteomic analyses, avoiding tedious optimization steps in 2-DE. This method is cost effective and can be done in centres without specialized 2-DE or MS equipment and elutes can be easily transported for analysis and bioinformatics. This is the first study to analyse urine samples directly for B. pseudomallei proteins. Discovery of the entire proteome as a whole is important in leading to biomarker discovery

Burkholderia pseudomallei short-chain dehydrogenase/ oxidoreductase: potential urine biomarker candidate for acute melioidosis

INTRODUCTION: In the current climate of urgency in identifying biomarkers for the development of rapid diagnostic kits, the use of urine samples to diagnose acute melioidosis was evaluated, comparing urine samples from Burkholderia pseudomallei culture-positive and culture-negative patients, and comparing pneumonic and septicemic melioidosis. MATERIAL AND METHODS: Eleven urine samples from clinically suspected melioidosis patients from a tertiary referral center, Hospital Tengku Ampuan Afzan, Pahang was used. An in-solution method for the detection of bacterial proteins using liquid chromatography-mass spectrometry quadrupole time-of-flight (LCMS QTOF) was used. RESULTS: Three bacterial proteins were consistently detected among all the culture[1]positive and PCR-positive cases tested, namely SDR family NAD(P)-dependent oxidoreductase protein (32kDa), 3-hydroxyacyl-CoA dehydrogenase Burkholderia sp. (32kDa), and NAD(P)-dependent dehydrogenase (short-subunit alcohol dehydrogenase family) Burkholderia sp. (33kDa). CONCLUSIONS: Short-chain dehydrogenase (SDO) proteins could potentially be a urine biomarker candidate as these have shown to aid in the ability of Burkholderia spp. to invade host cells as this action is important for the initial intracellular survival of the organism