The bacillithiol pathway is required for biofilm formation in Staphylococcus aureus.

Staphylococcus aureus is a major human pathogen that can cause infections that range from superficial skin and mucosal infections to life threatening disseminated infections. S. aureus can attach to medical devices and host tissues and form biofilms that allow the bacteria to evade the host immune system and provide protection from antimicrobial agents. To counter host-generated oxidative and nitrosative stress mechanisms that are part of the normal host responses to invading pathogens, S. aureus utilizes low molecular weight (LMW) thiols, such as bacillithiol (BSH). Additionally, S. aureus synthesizes its own nitric oxide (NO), which combined with its downstream metabolites may also protect the bacteria against specific host responses. We have previously shown that LMW thiols are required for biofilm formation in Mycobacterium smegmatis and Pseudomonas aeruginosa. Here, we show that the S. aureus bshC mutant strain, which is defective in the last step of the BSH pathway and lacks BSH, is impaired in biofilm formation. We also identify a possible S-nitrosobacillithiol reductase (BSNOR), similar in sequence to an S-nitrosomycothiol reductase found in M. smegmatis and show that the putative S. aureus bsnoR mutant strain has reduced levels of BSH and decreased biofilm formation. Our studies also show that NO plays an important role in biofilm formation and that acidified sodium nitrite severely reduces biofilm thickness. These studies provide insight into the roles of oxidative and nitrosative stress mechanisms on biofilm formation and indicate that BSH and NO are key players in normal biofilm formation in S. aureus.

"I see it very much as an end-of-life food" - Barriers to oral nutritional supplement adherence, views from healthy older adults.

Malnutrition affects approximately one quarter of UK adults aged 65 years and over. As the global demographic shift continues, malnutrition is expected to increase. Oral nutritional supplements (ONS) are used both to prevent and to treat malnutrition. However, their effectiveness is compromised by poor adherence, and it is not well understood what contributes to this. Therefore, the current research was designed to explore ONS adherence from the parallel perspectives of ONS as a prescribed "medication" and as a food supplement/substitute. Eighteen older adults (13F, 5M; mean age = 73.4 yr; range: 70-80 yr) participated in focus groups (three in-person and one online), to investigate experiences of taking prescribed medications, including dietary supplements, and what should be factors to consider in supporting regular intake of ONS for trial development, as well as any potential improvements to products. Focus group sessions were recorded and then transcribed. Thematic Analysis was applied to the transcripts by the first author, and themes were discussed in depth, using exemplar quotes from participants. Five dominant themes were identified from the data: Disgust, Palatability and Acceptance; End-of-Life Care; Resistance to Medicines; Rituals and Reminders; and Real Food Displacement. Nutritional supplements were characterised as "disgusting", "manufactured", and associated with serious, chronic illness, as well as end-of-life care, in contrast to probiotics which were linked with health and wellness. The sweet taste of ONS was identified as a barrier to intake, given that it is generally associated with a signal to stop eating, and low hunger. As a group, participants tried to "avoid taking medicines", and viewed the need to have them negatively, yet most regularly took prescribed medication and/or vitamin supplements. Participants identified several, rituals and reminders to take medicines, including meal-based, or time-of-day-based prompts (e.g., before, with or after meals). To improve adherence, savoury products were suggested, as well as a more person-centred approach to individual nutritional needs and preferences. Overall, the group discussion mainly identified barriers to intake, but that improving taste, adding to "real food" (not replacing meals), and offering variety of flavour and form (e.g., savoury soups as well as sweet drinks) could be included in future trials to improve appeal and therefore intake. Future work should continue to explore how best to formulate, market and/or prescribe ONS, and how this might vary for malnutrition prevention vs treatment strategies.

Effects of cueing multiple memories of eating on people's judgments about their diet.

Past research shows that recalling a single positive health-related experience, such as exercising, can encourage people's subsequent healthy behaviours. In contrast, we reasoned that attempting to recall many healthy experiences might elicit a metacognitive experience of difficulty that would lead people to perceive themselves as less healthy, and perhaps to make other health-related judgments based on this perception. In two pre-registered experiments (combined N = 729), participants recalled either "few" or "many" instances of eating either healthily or unhealthily, before rating the healthiness of their diets and completing measures of their eating preferences and choices. Contrary to our predictions, our pre-registered analyses provided minimal evidence that the number of memories people retrieved affected their judgments. However, exploratory mediation analyses suggested that two counteracting effects may have occurred, whereby retrieving more (un)healthy memories led people to identify as more (un)healthy, yet also created a sense of subjective difficulty that partially or wholly negated these effects. These findings suggest that whereas probing people's dietary memories might sometimes lead to healthier self-perceptions and dietary choices, we should also consider the possibility of backfire effects.

The effect of intranasal insulin on appetite and mood in women with and without obesity: an experimental medicine study.

BACKGROUND/OBJECTIVES: Intranasal (IN) administration of insulin decreases appetite in humans, but the underlying mechanisms are unclear, and it is unknown whether IN insulin affects the food intake of women with obesity. SUBJECTS/METHODS: In a double-blind, placebo-controlled, crossover design, participants (35 lean women and 17 women with obesity) were randomized to receive 160 IU/1.6 mL of IN insulin or placebo in a counterbalanced order in the post prandial state. The effects of IN insulin on cookie intake, appetite, mood, food reward, cognition and neural activity were assessed. RESULTS: IN insulin in the post prandial state reduced cookie intake, appetite and food reward relative to placebo and these effects were more pronounced for women with obesity compared with lean women. IN insulin also improved mood in women with obesity. In both BMI groups, IN insulin increased neural activity in the insula when viewing food pictures. IN insulin did not affect cognitive function. CONCLUSIONS: These results suggest that IN insulin decreases palatable food intake when satiated by reducing food reward and that women with obesity may be more sensitive to this effect than lean women. Further investigation of the therapeutic potential of IN insulin for weight management in women with obesity is warranted.

Frequency of fruit consumption and savoury snacking predict psychological health; selective mediation via cognitive failures.

While there is growing interest in the link between diet and psychological health, there is a surprising lack of studies investigating the precise associations between nutrient-rich foods (such as fruit and vegetables) versus nutrient-poor foods (such as energy-dense savoury and sweet snacks), and psychological health. Similarly, the psychological processes underpinning the relationship between dietary intake and psychological health remain unclear. Hence, the present study aimed to explore the relationship between dietary consumption and psychological health, with cognitive processes as a theoretical mediator. This cross-sectional online study included 428 healthy adults (53% female; mean age= 39.7, SD= 13.0), with participants completing a range of validated questionnaires measuring dietary habits and psychological health. Stepwise multiple regression revealed that more frequent consumption of fruit was associated with reduced symptoms of depression (ß = -.109, p = 0.025) and greater positive psychological wellbeing (ß = .187, p < 0.001). Conversely, more frequent savoury snacking was associated with increased anxiety (ß = .127, p = 0.005). Further, mediation analyses revealed that more frequent consumption of savoury snacks was associated with increased symptoms of depression, stress, anxiety, and reduced psychological wellbeing, via an increase in cognitive failures (ps < 0.001). These results provide new insights on the independent associations between certain types of food and psychological health, and the psychological mechanisms that may mediate these. Further work is now required to establish causality and determine whether these may represent modifiable dietary targets that can directly (and indirectly) influence our psychological health.

Adjunct Use of Continuous Renal Replacement Therapy with Extracorporeal Membrane Oxygenation Achieves Negative Fluid Balance and Enhances Oxygenation Which Improves Survival in Critically Ill Patients without Kidney Failure.

INTRODUCTION: Fluid overload in extracorporeal membrane oxygenation (ECMO) patients has been associated with increased mortality. Patients receiving ECMO and continuous renal replacement therapy (CRRT) who achieve a negative fluid balance have improved survival. Limited data exist on the use of CRRT solely for fluid management in ECMO patients. METHODS: We performed a single-center retrospective review of 19 adult ECMO patients without significant renal dysfunction who received CRRT for fluid management. These patients were compared to a cohort of propensity-matched controls. RESULTS: After 72 h, the treatment group had a fluid balance of -3840 mL versus + 425 mL (p ≤ 0.05). This lower fluid balance correlated with survival to discharge (odds ratio 2.54, 95% confidence interval 1.10-5.87). Improvement in the ratio of arterial oxygen content to fraction of inspired oxygen was also significantly higher in the CRRT group (102.4 vs. 0.7, p ≤ 0.05). We did not observe any significant difference in renal outcomes. CONCLUSIONS: The use of CRRT for fluid management is effective and, when resulting in negative fluid balance, improves survival in adult ECMO patients without significant renal dysfunction.

Front-of-pack health imagery on both 'healthy' and 'unhealthy' foods leads people to misremember seeing health claims: Two memory experiments.

Front-of-pack health imagery can shape people's inferences about food products' health benefits, even leading people to falsely remember reading health claims they never saw. However, research has typically examined these effects in situations where participants have little contextual information to guide their inferences about a product. The present research aimed to replicate the finding that front-of-pack health imagery leads participants to falsely remember reading health claims. It also extends that finding, by exploring whether this effect is moderated by the presence of contextual information signaling the product's actual 'healthiness'. In two pre-registered experiments, participants saw images of fictitious food products accompanied by written nutrition claims. Some of the products contained a health-related image whereas others did not. The supposed 'healthiness' of each product was manipulated by altering the color of the products' multiple traffic light (MTL) label (Experiment 1), or with an explicit healthiness statement (Experiment 2). Participants then attempted to remember the written claims that had appeared on each product's packaging. Health-related images increased participants' tendency to falsely remember reading health claims. But this was true regardless of whether or not participants saw contextual cues about the products' healthiness, either indirectly (Experiment 1) or directly (Experiment 2). These findings suggest that the presence of health imagery on a food product's package can lead consumers to infer health benefits, even when other, more direct cues indicate that the product is unhealthy. This research informs debates on safeguarding consumers from potentially misleading health claims, through the regulation of imagery in food marketing.

Exposure to models' positive facial expressions whilst eating a raw vegetable increases children's acceptance and consumption of the modelled vegetable.

Research has shown that seeing positive facial expressions (FEs) towards food increased children's desire to eat foods rated as disliked. However, the effect of adults' positive FEs whilst eating a raw vegetable on children's acceptance and intake of nutritious foods that are less preferred (e.g., vegetables) remains to be established. This study aimed to examine the effect of models' FEs eating raw broccoli on children's acceptance and intake of raw broccoli. 111 children aged 4-6 years (64 male, 47 female) were randomised to watch a video of unfamiliar adult models eating raw broccoli with a positive or neutral facial expression (FE), or a non-food control video. Children's acceptance and intake of raw broccoli was assessed. Data about parent and child characteristics was provided by parents. There was a main effect of FE type on children's frequency of tastes (p = .03) and intake of broccoli (p = .02). Children who were exposed to models eating broccoli with positive FEs had greater frequency of tastes (p = .04) and intake of broccoli (p = .03), than children in the control condition, but not compared to children in the neutral FE condition (p > .05). There was no effect of positive FEs on children's willingness to try broccoli (p > .05). These findings suggest that observing others enjoy a commonly disliked vegetable can encourage children's tastes and intake of the vegetable. Thus, exposing children to others enjoying vegetables could be a useful strategy for encouraging healthier eating in children. Further work is needed to determine whether a single exposure is sufficient and whether these effects are sustained over time.

Does exposure to socially endorsed food images on social media influence food intake?

Social norms can influence the consumption of high and low energy-dense (HED/LED) snack foods. Such norms could be communicated via social media, however, there is little experimental research investigating this possibility. This laboratory study aimed to investigate the acute effect of socially endorsed social media posts on participants' eating behaviour. Healthy women students (n = 169; mean age = 20.9; mean BMI = 23.3) were assigned to either a HED, LED or control condition, where they viewed three types of images (HED foods, LED foods and interior design as control), but only one type was socially endorsed (e.g. in the control condition, only interior design images were socially endorsed). Participants completed questionnaires and were also provided a snack buffet of grapes and cookies. One-way ANOVA revealed a significant main effect of condition on participants' relative consumption of grapes (percentage of grapes consumed out of total food intake), for both grams and calories consumed (both ps < .05). Follow-up t-tests revealed that participants consumed a larger proportion of grapes (grams and calories) in the LED condition vs HED condition (all ps < .05), and a larger proportion of calories from grapes in the LED compared to control condition (p < .05). These findings suggest that exposure to socially endorsed images of LED food on social media could nudge people to consume more of, and derive more calories from these foods in place of HED foods. Further research is required to examine the potential application of these findings.

YpdA, a putative bacillithiol disulfide reductase, contributes to cellular redox homeostasis and virulence in Staphylococcus aureus.

The intracellular redox environment of Staphylococcus aureus is mainly buffered by bacillithiol (BSH), a low molecular weight thiol. The identity of enzymes responsible for the recycling of oxidized bacillithiol disulfide (BSSB) to the reduced form (BSH) remains elusive. We examined YpdA, a putative bacillithiol reductase, for its role in maintaining intracellular redox homeostasis. The ypdA mutant showed increased levels of BSSB and a lower bacillithiol redox ratio vs. the isogenic parent, indicating a higher level of oxidative stress within the bacterial cytosol. We showed that YpdA consumed NAD(P)H; and YpdA protein levels were augmented in response to stress. Wild type strains overexpressing YpdA showed increased tolerance to oxidants and electrophilic agents. Importantly, YpdA overexpression in the parental strain caused an increase in BSH levels accompanied by a decrease in BSSB concentration in the presence of stress, resulting in an increase in bacillithiol redox ratio vs. the vector control. Additionally, the ypdA mutant exhibited decreased survival in human neutrophils (PMNs) as compared with the parent, while YpdA overexpression protected the resulting strain from oxidative stress in vitro and from killing by human neutrophils ex vivo. Taken together, these data present a new role for YpdA in S. aureus physiology and virulence through the bacillithiol system.

Do perceived norms of social media users' eating habits and preferences predict our own food consumption and BMI?

In laboratory studies, exposure to social norm messages conveying the typical eating behaviour of others has influenced participants' own consumption of food. Given the widespread use of social media, it is plausible that we are implicitly exposed to norms in our wider social circles, and that these influence our eating behaviour, and potentially, Body Mass Index (BMI). This study examined whether four perceived norms (perceived descriptive, injunctive, liking and frequency norms) about Facebook users' eating habits and preferences predicted participants' own food consumption and BMI. In a cross-sectional survey, men and women university students (n = 369; mean age = 22.1 years; mean BMI = 23.7) were asked to report their perceptions of Facebook users' consumption of, and preferences for, fruit, vegetables, energy-dense snacks and sugar sweetened beverages (SSBs), their own consumption of and preferences for these foods, and their BMI. Multiple linear regression revealed that perceived descriptive norms and perceived frequency norms about Facebook users' fruit and vegetable consumption were significant positive predictors of participants' own fruit and vegetable consumption (both ps < .01). Conversely, perceived injunctive norms about Facebook users' energy-dense snack and SSB consumption were significant positive predictors of participants' own snack and SSB consumption (both ps < .05). However, perceived norms did not significantly predict BMI (all ps > .05). These findings suggest that perceived norms concerning actual consumption (descriptive and frequency) and norms related to approval (injunctive) may guide consumption of low and high energy-dense foods and beverages differently. Further work is required to establish whether these perceived norms also affect dietary behaviour over time.

Front-of-pack images can boost the perceived health benefits of dietary products.

Images on dietary supplement packaging can help identify the products' supposed function. However, research shows that these images can also lead people to infer additional health benefits of consuming the products. The present research investigated the extent to which front-of-pack imagery affects people's perceptions of the health risks and benefits of fictional products. In three randomized experiments, participants saw fictitious dietary supplement packages. Some of the packages included a health-related image (e.g. a heart), whereas others did not. Participants were asked to infer the products' intended purpose and then to rate the perceived risks and benefits of consuming the product. In Experiment 1 (N = 546), the inclusion of a health-related image increased the perceived benefits of consuming the product, with minimal effect on the perceived risks. This finding was replicated in Experiment 2 (N = 164), but was contingent on whether each product's assumed health function was confirmed or disconfirmed. In Experiment 3 (N = 306), which used a pre-registered design and analysis plan, the inclusion of a health-related image increased the perceived benefits and decreased the perceived risks of consuming the product. Again, these effects were contingent on whether the assumed health functions were confirmed or disconfirmed. These findings indicate that health-related imagery could lead consumers to infer additional health properties from non-diagnostic information featured on a product's packaging, perhaps as a consequence of increased processing fluency. This research underscores the importance of regulating the use of imagery in health marketing, to protect consumers from the effects of potentially misleading claims.

Using repeated visual exposure, rewards and modelling in a mobile application to increase vegetable acceptance in children.

Children are not consuming the recommended amounts of fruit and vegetables. Repeated visual exposure, modelling, and rewards have been shown to be effective at increasing vegetable acceptance in young children. The aim of this study was to assess the effectiveness of an evidence-based mobile application (Vegetable Maths Masters) which builds on these principles to increase children's liking and acceptance of vegetables. Seventy-four children (37 male, 37 female) aged 3-6 years old were randomised to play with either the vegetable app or a similar control app that did not include any foods. Children played their allocated game for 10 min. Liking and acceptance of the vegetables used in Vegetable Maths Masters (carrot and sweetcorn) and other vegetables which were not used in the game (yellow pepper and tomato) were measured pre- and post-play in both groups. Parents provided data about their child's food fussiness and previous exposure to the foods being used. Children who played with the Vegetable Maths Masters app consumed significantly more vegetables after playing with the app and reported significant increases in their liking of vegetables, relative to the control group. The effect of the Vegetable Maths Masters app on the change in consumption of vegetables was mediated by the change in liking of vegetables. These findings suggest that evidence-based mobile apps can provide an effective tool for increasing children's liking and consumption of vegetables in the short-term. Further work is now required to establish whether these effects are maintained over time.

Two observational studies examining the effect of a social norm and a health message on the purchase of vegetables in student canteen settings.

There is some evidence from laboratory-based studies that descriptive social-norm messages are associated with increased consumption of vegetables, but evidence of their effectiveness in real-world settings is limited. In two observational field studies taking an ecological approach, a vegetable-related social norm (e.g. "Did you know that most students here choose to eat vegetables with their meal?"), and a health message (e.g. "Did you know that students who choose to eat vegetables have a lower risk of heart disease?") were displayed in two different student canteens. Purchases were observed during three stages: baseline, intervention (when the posters were displayed) and immediate post-intervention (when the posters had been removed). Study 1 (n = 7598) observed the purchase of meals containing a portion of vegetables and Study 2 (n = 4052) observed the purchase of side portions of vegetables. In Study 1, relative to baseline, the social-norms intervention was associated with an increase in purchases of vegetables (from 63% to 68% of meals; OR = 1.24, CI = 1.03-1.49), which was sustained post-intervention (67% of meals; OR = 0.96, CI = 0.80-1.15). There was no effect of the health message (75% of meals at baseline, and 74% during the intervention; OR = 0.98, CI = 0.83-1.15). In Study 2, relative to baseline, there was an effect of both the social norm (22.9% of meals at baseline, rising to 32.5% during the intervention; OR = 1.62, CI = 1.27-2.05) and health message (rising from 43.8% at baseline to 52.8%; OR = 0.59, CI = 0.46-0.75). The increase was not sustained post-intervention for the social norm intervention (22.1%; OR = 0.59, CI = 0.46-0.75), but was sustained for the health intervention (48.1%; OR = 0.83, CI = 0.67-1.02). These results support further testing of the effectiveness of such messages in encouraging healthier eating and indicate the need for larger-scale testing at multiple sites using a randomised-controlled design.

Flowers and Wild Megachilid Bees Share Microbes.

Transmission pathways have fundamental influence on microbial symbiont persistence and evolution. For example, the core gut microbiome of honey bees is transmitted socially and via hive surfaces, but some non-core bacteria associated with honey bees are also found on flowers, and these bacteria may therefore be transmitted indirectly between bees via flowers. Here, we test whether multiple flower and wild megachilid bee species share microbes, which would suggest that flowers may act as hubs of microbial transmission. We sampled the microbiomes of flowers (either bagged to exclude bees or open to allow bee visitation), adults, and larvae of seven megachilid bee species and their pollen provisions. We found a Lactobacillus operational taxonomic unit (OTU) in all samples but in the highest relative and absolute abundances in adult and larval bee guts and pollen provisions. The presence of the same bacterial types in open and bagged flowers, pollen provisions, and bees supports the hypothesis that flowers act as hubs of transmission of these bacteria between bees. The presence of bee-associated bacteria in flowers that have not been visited by bees suggests that these bacteria may also be transmitted to flowers via plant surfaces, the air, or minute insect vectors such as thrips. Phylogenetic analyses of nearly full-length 16S rRNA gene sequences indicated that the Lactobacillus OTU dominating in flower- and megachilid-associated microbiomes is monophyletic, and we propose the name Lactobacillus micheneri sp. nov. for this bacterium.

Can social media be used to increase fruit and vegetable consumption? A pilot intervention study.

Background: Exposure to social norms about fruit and vegetable intake has been shown to increase individuals' consumption of these foods. Further, exposure to socially endorsed 'healthy' food posts can increase consumption of low energy-dense (LED), relative to high energy-dense (HED) foods. The current pilot study aimed to investigate whether exposure to healthy eating (vs. control) social media accounts can shift normative perceptions about what others eat, eating intentions and self-reported food consumption. Methods: In a 2 (condition) × 2 (type of food consumed) mixed factorial design, 52 male and female students were asked to follow either healthy eating (intervention) or interior design (control) Instagram accounts over a two-week period. Baseline and post-intervention measures assessed normative perceptions of Instagram users' consumption of fruit and vegetables (LED foods), and energy dense snacks and sugar sweetened beverages (HED foods). Participants' intentions to consume, and self-reported consumption of these foods, were also measured. Results: There were no significant changes in perceptions about what others eat, or participants' own eating intentions (ps > 0.05). However, the intervention increased participants' self-reported consumption of LED foods by 1.37 servings (per day) and decreased consumption of HED foods by 0.81 items (per day), compared to the control condition (ps < 0.05). Conclusions: This novel pilot study demonstrates that a social norm-based social media intervention can successfully encourage healthier eating, with a large effect after two weeks. Certain social media platforms may therefore provide a viable tool for nudging healthy eating. Future work will aim to replicate these findings in a larger and more diverse sample.

Repeated exposure to models' positive facial expressions whilst eating a raw vegetable increases children's consumption of the modelled vegetable.

Exposing children to adults eating a raw vegetable with positive facial expressions ('positive modelling') increases children's consumption of the modelled vegetable. However, whether repeated versus a single exposure to positive modelling enhances this effect, and whether it generalises to a non-modelled vegetable, remains to be examined. Hence, this study examined the effect of a single exposure, versus repeated, exposure to positive modelling on children's acceptance and intake of a modelled and non-modelled vegetable. Children aged 5-6 years (N = 153; 81 males, 72 females) were randomised to one of three conditions in which they had i) a single or ii) repeated exposure to a video of adults eating raw broccoli with positive facial expressions or iii) were exposed to a no-food control video. Children's acceptance (measured as willingness to try and number of tastes), intake and liking of a modelled (raw broccoli) and non-modelled vegetable (raw mangetout) were measured. Children had greater raw broccoli consumption and liking if they had received repeated exposure to positive modelling, compared to children who had received a single exposure, but not compared to children in the control condition. Children's mangetout intake was greater in the single (versus repeated) positive condition, but this effect was not dependent on time. There was no effect on children's vegetable acceptance. Repeatedly exposing children to adults enjoying a vegetable encourages children's intake of the modelled vegetable in comparison to a single exposure. Thus, repeated exposure to others' food enjoyment may be a practical and useful strategy to encourage children's vegetable consumption.

Exposure to models' negative facial expressions whilst eating a vegetable decreases women's liking of the modelled vegetable, but not their desire to eat.

Introduction: Food enjoyment can be conveyed through facial expressions. Observing others' enjoyment of food has been found to influence adults' desirability of liked and disliked food. Exposing adults to other eaters enjoying nutritious foods that are typically disliked (e.g., vegetables) could enhance the consumption of vegetables by young adults. However, this remains to be examined in young adult populations. This study examined the effect of models' facial expressions towards raw broccoli on young adult women's change in liking and change in desire to eat a modelled vegetable (raw broccoli) and a non-modelled vegetable (cucumber). Methods: Young adult women (N = 205) were randomised to watch a video of unfamiliar adult models eating raw broccoli with a positive, negative, or neutral facial expression. Participants' change in liking and change in desire to eat the modelled and non-modelled vegetable was examined. Results: Observing models conveying negative facial expressions whilst eating raw broccoli resulted in a statistically significant reduction in liking ratings of broccoli, but not cucumber. There was no effect of models' facial expressions on the change in desire to eat foods. Discussion: These findings suggest that watching others express a negative facial expression whilst eating a raw vegetable reduces women's liking of the modelled vegetable, in the absence of a significant change to their desire to consume these foods. This highlights the power of others' negative facial expressions on food liking. Further work is needed to establish the effect of others' facial expressions on vegetable intake.

A mechano-electronic DNA switch.

We report a new kind of DNA nanomachine that, fueled by Hg(2+) binding and sequestration, couples mechanical motion to the multiply reversible switching of through-DNA charge transport. This mechano-electronic DNA switch consists of a three-way helical junction, one arm of which is a T-T mismatch containing Hg(2+)-binding domain. We demonstrate, using chemical footprinting and by monitoring charge-flow-dependent guanine oxidation, that the formation of T-Hg(2+)-T base pairs in the Hg(2+)-binding domain sharply increases electron-hole transport between the other two Watson-Crick-paired stems, across the three-way junction. FRET measurements are then used to demonstrate that Hg(2+) binding/dissociation, and the concomitant increase/decrease of hole transport efficiency, are strongly linked to specific mechanical movements of the two conductive helical stems. The increase in hole transport efficiency upon Hg(2+) binding is tightly coupled to the movement of the conductive stems from a bent arrangement toward a more linear one, in which coaxial stacking is facilitated. This switch offers a paradigm wherein the performance of purely mechanical work by a nanodevice can be conveniently monitored by electronic measurement.

Analyte-driven switching of DNA charge transport: de novo creation of electronic sensors for an early lung cancer biomarker.

A general approach is described for the de novo design and construction of aptamer-based electrochemical biosensors, for potentially any analyte of interest (ranging from small ligands to biological macromolecules). As a demonstration of the approach, we report the rapid development of a made-to-order electronic sensor for a newly reported early biomarker for lung cancer (CTAP III/NAP2). The steps include the in vitro selection and characterization of DNA aptamer sequences, design and biochemical testing of wholly DNA sensor constructs, and translation to a functional electrode-bound sensor format. The working principle of this distinct class of electronic biosensors is the enhancement of DNA-mediated charge transport in response to analyte binding. We first verify such analyte-responsive charge transport switching in solution, using biochemical methods; successful sensor variants were then immobilized on gold electrodes. We show that using these sensor-modified electrodes, CTAP III/NAP2 can be detected with both high specificity and sensitivity (K(d) ~1 nM) through a direct electrochemical reading. To investigate the underlying basis of analyte binding-induced conductivity switching, we carried out Förster Resonance Energy Transfer (FRET) experiments. The FRET data establish that analyte binding-induced conductivity switching in these sensors results from very subtle structural/conformational changes, rather than large scale, global folding events. The implications of this finding are discussed with respect to possible charge transport switching mechanisms in electrode-bound sensors. Overall, the approach we describe here represents a unique design principle for aptamer-based electrochemical sensors; its application should enable rapid, on-demand access to a class of portable biosensors that offer robust, inexpensive, and operationally simplified alternatives to conventional antibody-based immunoassays.