Detection of toxins involved in foodborne diseases caused by Gram‐positive bacteria

Bacterial toxins are food safety hazards causing about 10% of all reported foodborne outbreaks in Europe. Pertinent to Gram‐positive pathogens, the most relevant toxins are emetic toxin and diarrheal enterotoxins of Bacillus cereus, neurotoxins of Clostridium botulinum, enterotoxin of Clostridium perfringens, and a family of enterotoxins produced by Staphylococcus aureus and some other staphylococci. These toxins are the most important virulence factors of respective foodborne pathogens and a primary cause of the related foodborne diseases. They are proteins or peptides that differ from each other in their size, structure, toxicity, toxicological end points, solubility, and stability, types of food matrix to which they are mostly related to. These differences influence the characteristics of required detection methods. Therefore, detection of these toxins in food samples, or detection of toxin production capacity in the bacterial isolate, remains one of the cornerstones of microbial food analysis and an essential tool in understanding the relevant properties of these toxins. Advanced research has led into new insights of the incidence of toxins, mechanisms of their production, their physicochemical properties, and their toxicological mode of action and dose‐response profile. This review focuses on biological, immunological, mass spectrometry, and molecular assays as the most commonly used detection and quantification methods for toxins of B. cereus, C. botulinum, C. perfringens, and S. aureus. Gathered and analyzed information provides a comprehensive blueprint of the existing knowledge on the principles of these assays, their application in food safety, limits of detection and quantification, matrices in which they are applicable, and type of information they provide to the user.     

Chemical Protein Modification through Cysteine

The modification of proteins with non‐protein entities is important for a wealth of applications, and methods for chemically modifying proteins attract considerable attention. Generally, modification is desired at a single site to maintain homogeneity and to minimise loss of function. Though protein modification can be achieved by targeting some natural amino acid side chains, this often leads to ill‐defined and randomly modified proteins. Amongst the natural amino acids, cysteine combines advantageous properties contributing to its suitability for site‐selective modification, including a unique nucleophilicity, and a low natural abundance—both allowing chemo‐ and regioselectivity. Native cysteine residues can be targeted, or Cys can be introduced at a desired site in a protein by means of reliable genetic engineering techniques. This review on chemical protein modification through cysteine should appeal to those interested in modifying proteins for a range of applications.     

简约至上

<正>在这个栏目中,我们将向你展现如何用最简约的手法拍摄黑白的海景照片。打开网页和杂志,色彩鲜艳、视觉前卫的图片比比皆是,但是看得多了这些"大片"不免让人有些审美疲劳。现在,让我们返璞归真,拍摄一些极致简约的照片吧,这也许能为你在繁华中带来一丝宁静。简约并不只是一种纯粹的感觉,它是有方法可     

精准地控制景深

<正>学会使用景深预览按钮,让控制照片的景深不再神秘!景深,简单来说就是照片中焦点平面前后清晰的一段距离。在这段距离之外,都是模糊的。摄影师经常要利用这种模糊与清晰的对比来表现主体,发挥创意,拍摄出好看的图片。     

Dynamic hyperinflation: comparison of jet ventilation versus conventional ventilation in patients with severe end-stage obstructive lung disease

Positive pressure ventilation in patients with obstructive lung disease may result in over-inflation of the relatively compliant lungs, resulting in dynamic hyperinflation (DHI). Using a crossover trial design, we compared high-frequency jet ventilation (HFJV) versus "optimal" intermittent positive pressure ventilation (IPPV) in ten patients undergoing lung transplantation for severe, end-stage obstructive lung disease. We measured haemodynamics and the degree of DHI after both modes of ventilation. There were no significant differences between IPPV and HFJV, with respect to efficiency of ventilation (PaCO2), haemodynamic effects (stroke volume, blood pressure and cardiac output), or lung hyperinflation (trapped gas volume). This study suggests that HFJV, when compared with optimal IPPV, is no better at minimizing DHI in patients with severe, end-stage obstructive lung disease.