Q-Exactive Tandem Mass Spectrometry Research Articles

Decoding Acinetobacter baumannii biofilm dynamics and associated protein markers: proteomic and bioinformatics approach.

Biofilm formation by Acinetobacter baumannii is one of the major cause of its persistence in hospital environment. Biofilm phenotypes are more resistant to physical as well as chemical stresses than their planktonic counterparts. The present study was carried in quest of biofilm-associated protein markers and their association with various biological pathways of A. baumannii. The study was designed with an aim to highlight the crucial common factor present in the majority of the A. baumannii strains irrespective of its resistance nature. A label-free proteome comparison of biofilm and planktonic phenotypes of A. baumannii was done using QExactive tandem mass spectrometry. Our investigation suggests key elevation of adhesion factors, acetate metabolism, nutrient transporters, and secretion system proteins are required for biofilm formation in A. baumannii. Elevation of biofilm-associated proteins revealed that biofilm is the unique phenotype with the potential to form robust matrix-embedded colonies and defeat stress condition. Further, core protein markers of biofilm phenotypes could be used as targets for new clinical interventions to combat biofilm-associated infections.

Estrogenic activity of cylindrospermopsin and anatoxin-a and their oxidative products by FeIII-B*/H2O2

The cyanotoxins released into waters during cyanobacterial blooms can pose serious hazards to humans and animals. Apart from their toxicological mechanisms, cyanotoxins have been shown to be involved in estrogenic activity by in vivo and in vitro assays; however, there is limited information on the change in estrogenicity of cyanotoxins following chemical oxidation. In this study, the estrogenic activity of cylindrospermopsin (CYL) and anatoxin-a (ANA) at concentrations ranging from 2.4 × 10−7 M to 2.4 × 10−12 M (CYL) and 7.1 × 10−6 M to 7.1 × 10−11 M (ANA), and after treatment by the FeIII-B*/H2O2 catalyst system, was investigated by the yeast estrogen screen (YES) assay. The results indicate that CYL and ANA acted as agonists in the YES assay (CYL logEC50 = −8.901; ANA logEC50 = −6.789), their binding affinity to estrogen receptors is associated with their intrinsic properties, including ring structures and toxicant properties. CYL and ANA were shown to simulate endocrine disrupting chemicals (EDCs) to modulate the 17β-estradiol-induced estrogenic activity, resulting in non-monotonic dose responses. The treated CYL showed a significantly altered estrogenicity compared to the untreated CYL (T(2) = 8.168, p ≤ .05), while the estrogenicity of the treated ANA was not significantly different to the untreated ANA (T(2) = 1.295, p > .05). Intermediate products generated from CYL and ANA oxidized by FeIII-B*/H2O2 were identified using Q-Exactive Tandem Mass Spectrometry (LC-MS/MS). Treatment with FeIII-B*/H2O2 yielded open-ring by-products which likely resulted in CYL's reduced binding affinity to estrogen receptors. The insignificant change in the estrogenicity of treated ANA was possibly a result of its multiple ring structure products, which were likely able to bind to estrogen receptors. The comparisons for the estrogenicity of these cyanotoxins before and after FeIII-B*/H2O2 treatment suggest that the reductions in estrogenicity achieved by oxidation were dependent on the levels of cyanotoxins removed, as well as the estrogenicity of the degradation products. This is the first study on the change in the estrogenicity of CYL and ANA upon oxidation by FeIII-B*/H2O2, a high activity catalyst system.

Interactions of free and encapsulated hydroxycinnamic acids from green coffee with egg ovalbumin, whey and soy protein hydrolysates

The interactions of hydroxycinnamic and chlorogenic acids (all described as CHAs) from green coffee with hydrolysates of proteins from egg ovalbumin (EOH), whey (WPH) and soy (SPH) were studied depending on temperature (25 and 90 °C) and CHAs form (free or included in β-cyclodextrin (β-CD)). The binding degree was determined by liquid chromatography with Q-Exactive tandem mass spectrometry. The interactions were confirmed by liquid chromatography with ultrahigh resolution hybrid quadruple-time-of-flight mass spectrometry. As the result of binding, the content of CHAs in protein hydrolysates (PHs) ranged from 12.87 to 15.15 g/100 g. Inclusion of CHAs with β-CD strongly limited these interactions to a level of 0.48–1.32 g/100 g. Thermodynamic parameters of peptide-ligand interactions were determined by isothermal titration calorimetry and energetics of interactions at the atomic level by molecular modelling. The amount of CHAs released during proteolytic digestion was at a relatively low level of 0.06–1.14 g/100 g, and the availability for absorption of CHAs after proteolysis ranged from 1.26 to 4.05 g/100 g for free form and from 14.67 to 15.39 g/100 g for included form, indicating that encapsulating of CHAs in β-CD significantly increased their availability from processed food containing PHs after digestion.