Factors influencing the detergent-free membrane protein isolation using synthetic nanodisc-forming polymers

The detergent-free isolation of membrane proteins using synthetic polymers is becoming the desired approach for functional and structural studies of membrane proteins. Since the expression levels for many membrane proteins are low and a high yield of functionalized reconstituted membrane proteins is essential for in vitro studies, it is crucial to optimize the experimental conditions for a given polymer to solubilize target membranes/proteins effectively. The factors that affect membrane solubilization and subsequently the isolation of a target membrane protein include polymer concentration, polymer charge, temperature, pH, and concentration of divalent metal ions. Therefore, it is important to have knowledge about the efficacy of different types of polymers in solubilizing cell membranes. In this study, we evaluate the efficacy of inulin-based non-ionic polymers in solubilizing E. coli membranes enriched with rat flavin mononucleotide binding-domain (FBD) of cytochrome-P450-reductase (CPR) and rabbit cytochrome-b5 (Cyt-b5) under various solubilization conditions. Our results show that a 1:1 (w/w) membrane:polymer ratio, low temperature, high pH and sub-millimolar concentration of metal ions favor the solubilization of E. coli membranes enriched with FBD or Cyt-b5. Conversely, the presence of excess divalent metal ions affected the final protein levels in the polymer-solubilized samples. We believe that the results from this study provide knowledge to assess and plan the use of non-ionic polymers in membrane protein studies.

Factors influencing the detergent-free membrane protein isolation using synthetic nanodisc-forming polymers

The detergent-free isolation of membrane proteins using synthetic polymers is becoming the desired approach for functional and structural studies of membrane proteins. Since the expression levels for many membrane proteins are low and a high yield of functionalized reconstituted membrane proteins is essential for in vitro studies, it is crucial to optimize the experimental conditions for a given polymer to effectively solubilize target membranes/proteins. The factors that affect membrane solubilization and subsequently the isolation of a target membrane protein include polymer concentration, polymer charge, temperature, pH, and concentration of divalent metal ions. Therefore, it is important to have knowledge about the efficacy of different types of polymers in solubilizing cell membranes. In this study, we evaluate the efficacy of inulin-based non-ionic polymers in solubilizing E. coli membranes enriched with rat flavin mononucleotide binding-domain (FBD) of cytochrome-P450-reductase (CPR) and rabbit cytochrome-b5 (Cyt-b5) under various solubilization conditions. Our results show that a 1:1 (w/w) membrane:polymer ratio, low temperature, high pH and sub-millimolar concentration of metal ions favor the solubilization of E. coli membrane enriched with FBD or Cyt-b5. Conversely, the presence of excess divalent metal ions affected the final protein levels in the polymer-solubilized samples. We believe that the results from this study provides knowledge to assess and plan the use of non-ionic polymers in membrane protein studies.

Methicillin-resistant Staphylococcus aureus in food and the prevalence in Brazil: a review

Foodborne diseases (FBD) occur worldwide and affect a large part of the population, being a cause of international concern among health authorities. Staphylococcus aureus can be transmitted by contaminated food, and it is one of the pathogens that most cause foodborne outbreaks in Brazil. Currently, this organism's ability in developing resistance to antibiotics is notorious; methicillin-resistant Staphylococcus aureus-MRSA-is known for its resistance to methicillin, oxacillin, and others. MRSA is one of the leading causes of infections, becoming a major threat to human health worldwide due to the numerous toxins that can produce. At first, the transmission of MRSA occurred in clinical environments; but in recent decades, its presence has been reported in the community, outside the hospital environment, including food and food-producing animals around the world. In this review, information about MRSA was gathered to verify MRSA incidence in the world but especially in Brazil in food samples, food handlers, food-producing animals, and food processing environments. The studies show that MRSA is easily found and in certain cases with high frequency, thus representing a potential risk to public health.

Prebiotics in irritable bowel syndrome and other functional bowel disorders in adults: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Irritable bowel syndrome (IBS) and other functional bowel disorders (FBDs) are prevalent disorders with altered microbiota. Prebiotics positively augment gut microbiota and may offer therapeutic potential.

OBJECTIVES

The aim of this study was to investigate the effect of prebiotics compared with placebo on global response, gastrointestinal symptoms, quality of life (QoL), and gut microbiota, via systematic review and meta-analysis of randomized controlled trials (RCTs) in adults with IBS and other FBDs.

METHODS

Studies were identified using electronic databases, back-searching reference lists, and hand-searching abstracts. RCTs that compared prebiotics to placebo in adults with IBS or other FBDs were included. Two reviewers independently performed screening, data extraction, and bias assessment. Outcome data were synthesized as ORs, weighted mean differences (WMDs) or standardized mean differences (SMDs) with the use of a random-effects model. Subanalyses were performed for type of FBD and dose, type, and duration of prebiotic.

RESULTS

Searches identified 2332 records, and 11 RCTs were eligible (729 patients). The numbers responding were 52/97 (54%) for prebiotic and 59/94 (63%) for placebo, with no difference between groups (OR: 0.62; 95% CI: 0.07, 5.69; P = 0.67). Similarly, no differences were found for severity of abdominal pain, bloating and flatulence, and QoL score between prebiotics and placebo. However, flatulence severity was improved by prebiotics at doses ≤6 g/d (SMD: -0.35; 95% CI: -0.71, 0.00; P = 0.05) and by non-inulin-type fructan prebiotics (SMD: -0.34; 95% CI: -0.66, -0.01; P = 0.04), while inulin-type fructans worsened flatulence (SMD: 0.85; 95% CI: 0.23, 1.47; P = 0.007). Prebiotics increased absolute abundance of bifidobacteria (WMD: 1.16 log10 copies of the 16S ribosomal RNA gene; 95% CI: 0.06, 2.26; P = 0.04). No studies were at low risk of bias across all bias categories.

CONCLUSIONS

Prebiotics do not improve gastrointestinal symptoms or QoL in patients with IBS or other FBDs, but they do increase bifidobacteria. Variations in prebiotic type and dose impacted symptom improvement or exacerbation. This review was registered at PROSPERO as CRD42017074072.