Widespread and Indiscriminate Nanosilver Use: Genuine Potential for Microbial Resistance

In this era of increasing antibiotic resistance, the use of alternative antimicrobials such as silver has become more widespread. Superior antimicrobial activity has been provided through fabrication of silver nanoparticles or nanosilver (NAg), which imparts cytotoxic actions distinct from those of bulk silver. In the wake of the recent discoveries of bacterial resistance to NAg and its rising incorporation in medical and consumer goods such as wound dressings and dietary supplements, we argue that there is an urgent need to monitor the prevalence and spread of NAg microbial resistance. In this Perspective, we describe how the use of NAg in commercially available products facilitates prolonged microorganism exposure to bioavailable silver, which underpins the development of resistance. Furthermore, we advocate for a judicial approach toward NAg use in order to preserve its efficacy and to avoid environmental disruption

One-Pot Synthesis of High Molecular Weight Synthetic Heteroprotein Dimers Driven by Charge Complementarity Electrostatic Interactions

Despite the importance of protein dimers and dimerization in biology, the formation of protein dimers through synthetic covalent chemistry has not found widespread use. In the case of maleimide–cysteine-based dimerization of proteins, we show here that when the proteins have the same charge, dimerization appears to be inherently difficult with yields around 1% or less, regardless of the nature of the spacer used or whether homo- or heteroprotein dimers are targeted. In contrast, if the proteins have opposing (complementary) charges, the formation of heteroprotein dimers proceeds much more readily, and in the case of one high molecular weight (>80 kDa) synthetic dimer between cytochrome <i>c</i> and bovine serum albumin, a 30% yield of the purified, isolated dimer was achieved. This represents at least a 30-fold increase in yield for protein dimers formed from proteins with complementary charges, compared to when the proteins have the same charge, under otherwise similar conditions. These results illustrate the role of ionic supramolecular interactions in controlling the reactivity of proteins toward bis-functionalized spacers. The strategy here for effective synthetic dimerization of proteins could be very useful for developing novel approaches to study the important role of protein–protein interactions in chemical biology

Heterologous Production and Purification of a Functional Chloroform Reductive Dehalogenase

Reductive dehalogenases (RDases) are key enzymes involved in the respiratory process of anaerobic organohalide respiring bacteria (ORB). Heterologous expression of respiratory RDases is desirable for structural and functional studies; however, there are few reports of successful expression of these enzymes. <i>Dehalobacter</i> sp. strain UNSWDHB is an ORB, whose preferred electron acceptor is chloroform. This study describes efforts to express recombinant reductive dehalogenase (TmrA), derived from UNSW DHB, using the heterologous hosts <i>Escherichia coli</i> and <i>Bacillus megaterium</i>. Here, we report the recombinant expression of soluble and functional TmrA, using <i>B. megaterium</i> as an expression host under a xylose-inducible promoter. Successful incorporation of iron–sulfur clusters and a corrinoid cofactor was demonstrated using UV–vis spectroscopic analyses. <i>In vitro</i> dehalogenation of chloroform using purified recombinant TmrA was demonstrated. This is the first known report of heterologous expression and purification of a respiratory reductive dehalogenase from an obligate organohalide respiring bacterium

Effect of satiety factor infusions on serum levels of human MIC-1/GDF15.

<p>(A) Subjects receiving CCK-8 infusion alone had significant time dependent increase in serum levels of MIC-1/GDF15 with significant increases at 120, 150 and 180 minutes of infusion. Infusion of GLP-1 or CCK plus GLP-1 had no significant effect on serum MIC-1/GDF15 level (<i>n</i> = 9, <i>vehicle vs GLP-1</i>, <i>p</i> = 0.2; <i>vehicle vs CCK-8 + GLP-1</i>, <i>p</i> = 0.06). (B) PYY1-36 or PYY3-36 or saline was infused in subjects that were fasted overnight and had a 310-Kcal meal. Neither PYY1-36 nor PYY3-36 infusions had a significant effect on serum MIC-1/GDF15 levels (<i>n</i> = 8, <i>vehicle vs PYY1-36</i>, <i>p</i> = 0.18; <i>vehicle vs PYY3-36</i>, <i>p</i> = 0.34). Data were analysed by ANOVA <i>with Bonferroni correction</i> and are presented as mean ± s.e.m. * represents <i>p</i> < 0.05.</p

Postprandial changes in human MIC-1/GDF15 serum levels.

<p>Changes in serum MIC-1/GDF15 levels over time were measured in 17 subjects that received 5 different isocaloric meals on 5 separate occasions. (A) Changes in MIC-1/GDF15 serum levels do not differ for the 5 subjects fed the 5 different meals (<i>n</i> = 17, <i>p</i> = 0.26 <i>repeated measure ANOVA</i>). (B) When average data from all meals was pooled and normalised to baseline concentrations, there was significant time dependent alteration in circulating MIC-1/GDF15 levels (<i>n</i> = 5 meal; 17 subject/meal, <i>p</i> < 0.001 <i>one-way ANOVA</i>). (C) The postprandial profile of MIC-1/GDF15 serum levels (red) described in panel B were not significantly from its 24 h oscillatory pattern (<i>p</i> = 0.28, <i>repeated measure ANOVA</i>). Data represented as mean ± s.e.m.</p

Correlation of monozygotic within-pair differences in MIC-1/GDF15 serum levels and within-pair differences in BMI.

<p>Correlation between within twin-pair difference in serum MIC-1/GDF15 levels and within twin-pair difference in BMI (<i>n</i> = 72 twins), performed by Spearman regression, identifies a highly significant correlation. In general the twin of the twin pair with a higher serum MIC-1/GDF15 level generally had a lower BMI than their identical twin pair. The reverse was also true.</p

Fasting diurnal variation of human MIC-1/GDF15 serum levels.

<p>Serum MIC-1/GDF15 levels were measured on blood sample taken from participants every 30min during a 24h period. The oscillatory pattern of serum MIC-1/GDF15 levels for each individual subject was fitted to a cosine curve function.</p

Time of day for maximum and minimum MIC-1/GDF15 serum levels.

<p>Time of day for maximum and minimum MIC-1/GDF15 serum levels.</p