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The host-microbe interaction is critical for intestinal homeostasis. By-products from microbial metabolism of unabsorbed dietary components have been studied increasingly as potential contributors to health and disease. In vitro fermentation systems provide a way to simulate microbial activity and by-product production of the colon using human fecal samples. Objectives of the study were to determine how clarified supernatants from two different fermentation conditions affect markers of cell proliferation, differentiation, barrier function, and immune function in a human-induced pluripotent (iPSC) colon organoid model. SCFA and BCFA's of the supernatants were analyzed and were similar to known in vivo concentrations. Molecular results showed 25% of the clarified supernatant from batch fermentation led to a more physiological intestinal phenotype including increased markers of differentiation, including alkaline phosphatase, chromogranin A, SCFA transport monocarboxylate transporter-1, (6.2-fold, 2.1-fold, and 1.8-fold, respectively

Introduction Personnel engaged in high-stakes occupations, such as military personnel, law enforcement, and emergency first responders, must sustain performance through a range of environmental stressors. To maximize the effectiveness of military personnel, an a priori understanding of traits can help predict their physical and cognitive performance under stress and adversity. This work developed and assessed a suite of measures that have the potential to predict performance during operational scenarios. These measures were designed to characterize four specific trait–based domains: cognitive, health, physical, and social-emotional. Materials and Methods One hundred and ninety-one active duty U.S. Army soldiers completed interleaved questionnaire–based, seated task–based, and physical task–based measures over a period of 3-5 days. Redundancy analysis, dimensionality reduction, and network analyses revealed several patterns of interest. Results First, unique variable analysis revealed a minimally redundant battery of instruments. Second, principal component analysis showed that metrics tended to cluster together in three to five components within each domain. Finally, analyses of cross-domain associations using network analysis illustrated that cognitive, health, physical, and social-emotional domains showed strong construct solidarity. Conclusions The present battery of metrics presents a fieldable toolkit that may be used to predict operational performance that can be clustered into separate components or used independently. It will aid predictive algorithm development aimed to identify critical predictors of individual military personnel and small-unit performance outcomes.

Food processing alters diet digestibility and composition, thereby influencing interactions between host biology, diet, and the gut microbiota. The fecal metabolome offers insight into those relationships by providing a readout of diet-microbiota interactions impacting host health.To determine the effects of consuming a processed diet on the fecal metabolome, and to explore relationships between changes in the fecal metabolome with fecal microbiota composition and gastrointestinal health markers.Secondary analysis of a randomized-controlled trial wherein healthy adults (94% male; 18-61 yr; BMI 26 ± 3 kg.m-2) consumed their usual diet (CON, n = 27) or a Meal, Ready-to-EatTM military ration diet comprised of processed, shelf-stable, ready-to-eat items for 21d (MRE, n = 27). Fecal metabolite profiles, fecal microbiota composition, biomarkers of intestinal barrier function, and gastrointestinal symptoms were measured before and after the intervention. Between-group differences and associations were assessed using nonparametric t-tests, partial least squares discriminant analysis, correlation and redundancy analysis.Fecal levels of multiple dipeptides (Mann-Whitney effect size (ES) = 0.27-0.50) and long-chain saturated fatty acids (ES = 0.35-0.58) increased, whereas, plant-derived compounds (ES = 0.31-0.60) decreased in MRE versus CON (P 0.05; q 0.20). Changes in dipeptides correlated positively with changes in fecal levels of Maillard-reaction products (ρ = 0.29-0.70; P 0.05) and inversely with changes in serum prealbumin (ρ = -0.30 - -0.48; P ≤ 0.03). Multiple bile acids, coffee and caffeine metabolites, and plant-derived compounds were associated with both fecal microbiota composition and gastrointestinal health markers, with changes in fecal microbiota composition explaining 26% of the variability within changes in gastrointestinal health-associated fecal metabolites (P = 0.001).Changes in the fecal metabolomes of adults consuming a Meal, Ready-to-EatTM diet implicate interactions between diet composition, diet digestibility and the gut microbiota as contributing to variability within gastrointestinal responses to the diet. Findings underscore the need to consider both food processing and nutrient composition when investigating the impact of diet-gut microbiota interactions on health outcomes. Clinical trials registration: clinicaltrials.gov NCT02423551.

The Tri-Service Microbiome Consortium (TSMC) was founded to enhance collaboration, coordination, and communication of microbiome research among U.S. Department of Defense (DoD) organizations and to facilitate resource, material and information sharing among consortium members. The 2019 annual symposium was held 22–24 October 2019 at Wright-Patterson Air Force Base in Dayton, OH. Presentations and discussions centered on microbiome-related topics within five broad thematic areas: 1) human microbiomes; 2) transitioning products into Warfighter solutions; 3) environmental microbiomes; 4) engineering microbiomes; and 5) microbiome simulation and characterization. Collectively, the symposium provided an update on the scope of current DoD microbiome research efforts, highlighted innovative research being done in academia and industry that can be leveraged by the DoD, and fostered collaborative opportunities. This report summarizes the presentations and outcomes of the 3rd annual TSMC symposium.

The US Department of Defense, including the Army, Air Force, Navy, and Defense Advanced Research Projects Agency (DARPA) has engaged in cognitive enhancement research and development for over a century, exploring novel pharmaceutical, dietary, neuroscientific, instructional, technological, and sleep-related enhancement strategies. The overall objective of this work is to identify safe, reliable, and robust strategies and technologies to help military personnel achieve dominance through enhanced skill acquisition, vigilance and threat detection, situation awareness, decision-making, teamwork, and emotional control. The present review provides an introductory overview of recent and current US Army research examining several approaches to cognitive enhancement. These include approaches aimed at specifically targeting neural mechanisms and processes directly responsible for enhanced task performance and include transcranial electrical stimulation (tES), augmented reality (AR), and targeted skills training. Also considered are approaches targeting nth-order mechanisms and processes that relatively indirectly affect perception, cognition, and/or emotion and include nutritional and dietary intervention, resilience, cognitive and teamwork training, peripheral nerve stimulation, and sleep modification. We detail several promising approaches and provide an overview of forward-looking research objectives pursued by the US Army. Finally, we provide an overview of some of the ethical, regulatory, methodological, technological, doctrinal, and reliability challenges facing cognitive enhancement research and constraining its immediate application to military training and operations.

Background: Interactions between diet, stress and the gut microbiome are of interest as a means to modulate health and performance. Here, in vitro fermentation was used to explore the effects of a sudden change in diet, 21 days sole sustenance on the Meal, Ready-to-Eat (MRE) U.S. military combat ration, on inter-species competition and functional potential of the human gut microbiota. Human fecal samples collected before and after MRE intervention or consuming a habitual diet (HAB) were introduced to nutrient-rich media supplemented with starch for in vitro fermentation under ascending colon conditions. 16S rRNA amplicon and Whole Genome Sequencing (WGS) were used to measure community composition and functional potential. Specific statistical analyses were implemented to detect changes in relative abundance from taxa, genes and pathways.Results: Differential changes in relative abundance of five taxa, Dorea spp., Akkermansia muciniphila, Prevotella spp., Desulfovibrio spp., and Dialister spp., and four Carbohydrate-Active Enzymes, specifically GH13_14, over the 24 h fermentation were observed as a function of the diet intervention and correlated to specific taxa of interest. Conclusions: These findings suggest that consuming MRE for 21 days minimally effects changes in gut microbiota structure in response to carbohydrate, but may induce alterations in metabolic capacity. Additionally, these findings demonstrate the potential of starch as a candidate supplemental strategy to functionally modulate specific gut commensals during stress-induced states.

Random and block N-isopropylacrylamide (NIPAM)/cysteamine copolymers and a thiol-terminated NIPAM homopolymer have been synthesized, characterized, and covalently linked to gold nanoparticles. Elec...

Vitamins have well-established roles in bacterial metabolism. Menaquinones (MKn, n = prenyl units in sidechain) are bacterially produced forms of vitamin K produced by the gut microbiota and consumed in the diet. Little is known about the influence of dietary vitamin K quinones on gut microbial composition and MKn production. Here, male and female C57BL6 mice were fed a vitamin K deficient diet or vitamin K sufficient diets containing phylloquinone (PK, plant-based vitamin K form), MK4, and/or MK9. DNA was extracted from cecal contents and 16S sequencing conducted to assess microbial composition. Cecal microbial community composition was significantly different in vitamin K deficient female mice compared to females on vitamin K sufficient diets (all p .05 but

OBJECTIVES: Vitamin K (VK) is a family of structurally-related quinones, phylloquinone (PK) and menaquinones (MKn, n = prenyl units in side chain), that share a common napthoquinone ring (menadione, MD). VK quinones function as an essential dietary nutrient for humans. MD is considered a pro-vitamin form of VK. Plants and bacteria that produce VK quinones (PK and MKn, respectively) use them as an electron carrier in energy production. Little is known about the interaction of dietary VK quinones with gut bacteria, which may be bi-directional. The objective of this study was to investigate the influence of VK quinones and MD on human gut bacteria composition and MKn production. METHODS: Stool from 5 healthy male donors was pooled and inoculated in bioreactors under conditions mimicking the colon (anaerobic, pH 6.8, 37°C) for 48 h. Bioreactors were treated with deuterium ((2)H)-labeled quinones ((2)H-PK, (2)H-MK4, (2)H-MK9 or (2)H-MD); no quinones (cell controls); or (2)H-quinone treatment with no stool (cell-free controls). Culture aliquots were collected at 0, 5, 10, 24, and 48 h, and separated into pellet and supernatant fractions. Experiments were conducted in triplicate. All fractions were analyzed for VK quinone content using LC-MS. DNA from 0 and 24 h pellet fractions was extracted and amplified for paired-end 16S sequencing on an Illumina MiSeq 2500. Differences in bacterial composition were assessed using PERMANOVA. RESULTS: Supplemented (2)H-quinones accumulated in the pellet fraction over time. This was not observed in cell-free controls and was thus not a function of culture media solubility. Endogenous (unlabeled) production of MKn was unaffected by supplementation of (2)H-quinones. Generated (2)H-MKn ((2)H-MK4, (2)H-MK9, (2)H-MK10, and (2)H-MK11) were only detected in (2)H-MD supplemented vessels. Community-wide bacterial composition significantly differed between 0 h and 24 h (r(2 )= 0.85, P = 0.001), but not by quinone treatment. CONCLUSIONS: PK and MKn, dietary viamin K quinones, were not transformed by gut microbes to MKn in vitro, whereas the pro-vitamin quinone MD was transformed to MKn of multiple side chain lengths. Although no quinone induced community-wide changes in bacteria composition, additional analyses are needed to assess species-specific growth promotion. FUNDING SOURCES: USDA ARS and DOD Health Program.

The gut microbiome is increasingly recognized as integral to human health, and is emerging as a mediator of human physical and cognitive performance. This has led to the recognition that US Department of Defense (DoD) research supporting a healthy and resilient gut microbiome will be critical to optimizing the health and performance of future Warfighters. To facilitate knowledge dissemination and collaboration, identify resource capabilities and gaps, and maximize the positive impact of gut microbiome research on the Warfighter, DoD partners in microbiome research participated in a 2-day informational meeting co-hosted by the Natick Soldier Research, Engineering and Development Center (NSRDEC) and the US Army Research Institute of Environmental Medicine (USARIEM) on 16–17 November 2015. Attendee presentations and discussions demonstrated that multiple DoD organizations are actively advancing gut microbiome research. Common areas of research included the influence of military-relevant stressors on interactions between the microbiome and Warfighter biology, manipulation of the microbiome to influence Warfighter health, and use of the microbiome as a biomarker of Warfighter health status. Although resources and capabilities are available, they vary across laboratories and it was determined that centralizing certain DoD capabilities could accelerate progress. More significantly, the meeting created a foundation for a coordinated gut microbiome and nutrition research program aligning key DoD partners in the area of microbiome research. This report details the presentations and discussions presented during the 1st DoD Gut Microbiome Informational Meeting.

In vitro fermentation systems offer significant opportunity for deconvoluting complex metabolic dynamics within polymicrobial communities, particularly those associated with the human gut microbiome. In vitro gut models have broad experimental capacity allowing rapid evaluation of multiple parameters, generating knowledge to inform design of subsequent in vivo studies. Here, our method describes an in vitro fermentation test bed to provide a physiologically-relevant assessment of engineered probiotics circuit design functions. Typically, engineered probiotics are evaluated under pristine, monoor co-culture conditions and transitioned directly into animal or human studies, commonly resulting in a loss of desired function when introduced to complex gut communities. Our method encompasses a systematic workflow entailing fermentation, molecular and functional characterization, and statistical analyses to validate an engineered probiotic’s persistence, plasmid stability and reporter response. To demonstrate the workflow, simplified polymicrobial communities of human gut microbial commensals were utilized to investigate the probiotic Escherichia coli Nissle 1917 engineered to produce a fluorescent reporter protein. Commensals were assembled with increasing complexity to produce a mock community based on nutrient utilization. The method assesses engineered probiotic persistence in a competitive growth environment, reporter production and function, effect of engineering on organism growth and influence on commensal composition. The in vitro test bed represents a new element within the Design-Build-Test-Learn paradigm, providing physiologically-relevant feedback for circuit re-design and experimental validation for transition of engineered probiotics to higher fidelity animal or human studies.

Two methods of fabricating metal oxide nanoparticle-functionalized knitted “swatches” from melt-extruded bi-component sheath/core polypropylene (PP) fibers are described, and their possible applications for photocatalysis and gas sensing are investigated. The first method consists of melt extruding a blend of metal oxide nanoparticles and PP into fibers that are subsequently knitted into swatch materials. This method was evaluated for ZnO nanospheres and nanorods. X-ray photoelectron spectroscopy and electron microscopy showed that the nanoparticles were in the near-surface region as well as in the bulk of the fibers. However, the particles were shown to be photocatalytically inactive, likely due to site blocking by PP or processing additives, such as fiber lubricants. The second method consists of plasma-treating virgin PP swatches in air, immersing them in metal oxide colloidal suspensions, ultra-sonicating them to remove loose nanoparticles and drying the swatches. XPS confirmed that plasma treatment forms carboxylate groups on the surface that bond the metal oxide nanoparticles to the swatch. This method was used to functionalize swatches with ZnO and TiO2 nanospheres and ZnO nanorods. Metal oxide functionalization was found to induce dramatic changes in the thermal decomposition temperature of the PP swatch and in the water contact angle, rendering the swatch hydrophobic and producing photocatalytically active PP fabrics. Photoluminescence of the ZnO nanoparticle swatches was measured and shown to change upon exposure to sulfur dioxide. Furthermore, the demonstration of metal oxide-functionalized swatches as a potential gas-sensing platform is discussed.

OBJECTIVES: The human small intestine is a complex and dynamic organ tasked with enzymatic digestion and absorption of nutrients. Design of a small intestine model can provide detailed systematic knowledge of these processes; model design challenges include differential pH and oxygen availability along the length of the small intestine, food-dependent host secretion of digestive compounds, complex nutrient absorption processes, and microbiome interactions with both food and host. Numerous in vitro models have been developed to simulate the small intestine, but physiological relevance is limited. Here, we present an in vitro fermentation model of the small intestine to include microbiota and enhance physiological relevance. METHODS: A stepwise biofidelic model design approach was implemented with initial stages consisting of simulating ileum conditions, including pH and residence time, utilizing an automated bioreactor system for real-time monitoring and control of fermentation parameters, with incorporation of digestive enzymes and bile acids for breakdown of food inputs. Nutrient absorption, simulated using hollow-fiber columns to emulate passive diffusion, was initially optimized using small molecules to mimic dietary digestion byproducts; validation with food components, such as starch or whey powder, is planned. A mock microbial community, with organisms selected to represent major phyla and functions of the small intestine microbiota, was designed, implemented, and characterized in fermentations representing “fed-state” ileum conditions. RESULTS: Design and validation of the model with mock food components will be presented, along with steps taken to integrate in situ nutrient absorption and mock microbial community. Initial characterization of the microbial community indicates synergistic growth dynamics and nutrient utilization under “fed-state” conditions. CONCLUSIONS: These efforts will be the foundation for our long-term goal of simulating the small intestine to complement our large intestine fermentation model, jA(2)COB, creating a complete in vitro fermentation model of the lower GI tract. Insight gleaned from this model, alone or in concert with in vivo studies, can inform nutritional strategies to restore and maintain host gut homeostasis. FUNDING SOURCES: Funded by U.S. Army NSRDEC core applied research funds.

OBJECTIVES: From a military perspective, the gut microbiome serves as an ideal tool to enhance Soldier gut and immune health and to improve survivability and performance. Our work employs in vitro tools as a means to elucidate systematic processes of colonic bacterial metabolism of dietary inputs under native and stressed conditions. This talk will focus on the use of in vitro fermentation to investigate both the prebiotic potential of cranberry proanthocyanidins (PAC) within a healthy microbiome and stress-induced alterations in microbial inter-species competition for fermentable fiber. METHODS: Fermentations were performed in triplicate, utilizing fecal inocula derived from at least three individuals, in a nutrient-rich anaerobic medium with sampling at 0 and 24 hrs. Within PAC supplementation studies, samples were analyzed for bacterial identification (16 s rRNA sequencing) and metabolite content (GC-FID and GC/MS). Stressed metabolism studies, which utilized fecal samples before and after a 21-day change in diet challenge (habitual vs. Meal Ready-to-Eat), employed media supplemented with resistant starch under ascending colon domain-specific conditions; samples taken were analyzed for bacterial identification (16 s rRNA) and enumeration of select organisms (qPCR). RESULTS: Bacterial population dynamics within PAC supplementation studies indicated a dose-dependent increase in several beneficial taxa, including Ruminococcus spp (P

Interactions between gut microbes and dietary components modulate intestinal permeability (IP) and inflammation. Recent studies have reported altered fecal microbiota composition together with increased IP and inflammation in individuals consuming military food rations in austere environments, but could not isolate effects of the diet from environmental factors. To determine how the U.S. Meal, Ready-to-Eat food ration affects fecal microbiota composition, IP and inflammation, 60 adults (95% male,18-61 years) were randomized to consume their usual ad libitum diet for 31 days (CON) or a strictly controlled Meal, Ready-to-Eat-only diet for 21 days followed by their usual diet for 10 days (MRE). In both groups, fecal microbiota composition was measured before, during (INT, days 1-21) and after the intervention period. IP and inflammation [high-sensitivity C-reactive protein (hsCRP)] were measured on days 0, 10, 21 and 31. Longitudinal changes in fecal microbiota composition differed between groups (P=.005), and fecal samples collected from MRE during INT were identified with 88% accuracy using random forest models. The genera making the strongest contribution to that prediction accuracy included multiple lactic acid bacteria (Lactobacillus, Lactococcus, Leuconostoc), which demonstrated lower relative abundance in MRE, and several genera known to dominate the ileal microbiota (Streptococcus, Veillonella, Clostridium), the latter two demonstrating higher relative abundance in MRE. IP and hsCRP were both lower (34% and 41%, respectively) in MRE relative to CON on day 21 (P

Tungsten oxide (WO3) nanoparticles, with an average size of ca. 50 nm, dramatically change color from light to dark green upon methanethiol (MT) exposure. Proton NMR indicates the presence of physisorbed MT and its oxidation product, dimethyldisulfide. X-ray photoelectron spectroscopy indicates that a maximum of ca. 33% of the W6+ is reduced to W5+ in the process of MT oxidation with creation of oxygen vacancies. Raman spectroscopy shows negligible changes in lattice vibrations, consistent with absence of proton insertion. These results demonstrate that the color change is due to W5+ to W6+ intervalence transitions and support an oxygen vacancy mechanism.

Stress, a ubiquitous part of daily human life, has varied biological effects which are increasingly recognized as including modulation of commensal microorganisms residing in the gastrointestinal tract, the gut microbiota. In turn, the gut microbiota influences the host stress response and associated sequelae, thereby implicating the gut microbiota as an important mediator of host health. This narrative review aims to summarize evidence concerning the impact of psychological, environmental, and physical stressors on gut microbiota composition and function. The stressors reviewed include psychological stress, circadian disruption, sleep deprivation, environmental extremes (high altitude, heat, and cold), environmental pathogens, toxicants, pollutants, and noise, physical activity, and diet (nutrient composition and food restriction). Stressors were selected for their direct relevance to military personnel, a population that is commonly exposed to these stressors, often at extremes, and in combination. However, the selected stressors are also common, alone or in combination, in some civilian populations. Evidence from preclinical studies collectively indicates that the reviewed stressors alter the composition, function and metabolic activity of the gut microbiota, but that effects vary across stressors, and can include effects that may be beneficial or detrimental to host health. Translation of these findings to humans is largely lacking at present. This gap precludes concluding with certainty that transient or cumulative exposures to psychological, environmental, and physical stressors have any consistent, meaningful impact on the human gut microbiota. However, provocative preclinical evidence highlights a need for translational research aiming to elucidate the impact of stressors on the human gut microbiota, and how the gut microbiota can be manipulated, for example by using nutrition, to mitigate adverse stress responses.

Monolayer-protected gold nanoparticles (AuNPs) with average diameters of 2-4 nm have been covalently attached to zinc oxide nanorods using dithiol ligands. Electron microscopy and Raman spectroscopy show that ozone treatment or annealing at 300 or 450 °C increases the average diameter of the AuNPs to 6, 8, and 14 (±1) nm, respectively, and decomposes the organic layers to various degrees. These treatments locate the AuNPs closer to the nanorods. Heating and subsequent ozone exposure changes the color of the as-prepared nanocomposite powder from blue to purple due to oxidation of the outer layer of the AuNPs, and heating to 300 °C changes it to pink due to oxygen desorption. ZnO nanorods have a bimodal photoluminescence spectrum that consists of an ultraviolet excitonic peak and a visible, surface defect-related peak. Ozone treatment and annealing of the nanocomposite decreases the intensities of both peaks due to quenching by the AuNPs, but the visible peak is affected less. The photocatalytic efficiency of the nanocomposites toward oxidative degradation of rhodamine B has been measured and follows the order 300 °C450 °Cozone treated ≈ as-prepared ≈ bare ZnO. The greater efficiency of the annealed samples likely arises from decreased electron-hole pair recombination rates.

A naturally occurring antimicrobial peptide, SMAP-29, was synthesized with an n-terminal or c-terminal cysteine, termed c_SMAP and SMAP_c, respectively, for site-directed immobilization to superparamagnetic beads. Immobilized SMAP orientation-dependent activity was probed against multiple bacteria of clinical interest including Acinetobacter baumannii, Pseudomonas aeruginosa, Bacillus anthracis sterne and Staphylococcus aureus. A kinetic microplate assay was employed to reveal both concentration and time-dependent activity for elucidation of minimum bactericidal concentration (MBC) and sub-lethal effects. Immobilized SMAP activity was equivalent or reduced compared with soluble SMAP_c and c_SMAP regardless of immobilization orientation, with only one exception. A comparison of immobilized SMAP_c and c_SMAP activity revealed a bacteria-specific potency dependent on immobilization orientation, which was contrary to that seen in solution, wherein SMAP_c was more potent against all bacteria than c_SMAP. Sub-MBC kinetic studies displayed the influence of peptide exposure to the cells with multiple bacteria exhibiting increased susceptibility and efficacy at lower concentrations upon extended exposure (i.e. MBC enhancement). For instances in which complete killing was not achieved, two predominant effects were evident: retardation of growth rate and an increased lag phase. Both effects, seen independently and concomitantly, indicate some degree of induced cellular damage that can serve as a predictor toward eventual cell death. SMAP_c immobilized on glass through standard silanization chemistry was also investigated to ascertain the influence of substrate on activity against select bacteria.

Polydimethylsiloxane-aromatic dianhydride copolymers (PS-Oxy-PAA and PS-DAH-PAA) were blended through several techniques with organoclays Cloisite 30B, 10A and Na+ ranging from 1 to 5 wt.%. Thermal and flame-retardant analysis revealed an in-situ blending approach was optimal, which led to the generation of a nanocomposite, PS-Oxy-PAA/30B (5 wt.%), with comparable heat release capacity (170.5 J/g-K) and total heat release (12.0 kJ/g) as seen with some commercial polymers. Concomittant dispersion and FTIR analyses revealed that the enhanced thermal stability observed with PS-Oxy-PAA/30B (5 wt.%) is not dispersion related, since the organoclay was exfoliated in all composites formed. The driving force is the interaction between the carbonyl groups of the PS-Oxy-PAA and the hydroxyl groups of the organoclay, which is limited in all other cases. These results suggest judicious selection of organoclay and siloxane copolymers can faciliate the design of new environmentally safe, heat processible, nonhalogenated...

Adsorption of thiols on ZnO(0001) and ZnO nanorods has been investigated using X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS). Ultrahigh vacuum (UHV) dosing of sputter-cleaned ZnO(0001) with methanethiol (MT), 1-dodecanethiol (DDT), and 3-mercaptopropyltrimethoxysilane (MPTMS) leads to S2p peaks with a binding energy of 163.3 eV. Similar results for MPTMS are obtained for sputter-cleaned ZnO(0001) that is pre-dosed with water to form hydroxyl groups. In all cases, the absence of a free thiol S2p peak at 164.2 eV indicates that bonding to the surface occurs via the thiol end of the molecule. A DDT-dosed ZnO(0001) sample stored for 10 days in UHV and heated to temperatures as high as 150 °C exhibits minimal changes in its S/Zn atomic ratio, confirming chemisorption and the presence of a strong bond to the surface. UPS shows that MT adsorption on sputtered ZnO(0001) leads to a 0.7 eV increase in work function and perturbation of the MT molecular orbitals, again consistent with chemisorption. Dry ZnO nanorods have been exposed to MT while monitoring their photoluminescence. XPS and Raman spectroscopy confirm thiol adsorption. Relative to dry ZnO, adsorption causes a decrease in intensity of the visible emission peak, but the UV peak remains unchanged. These results indicate that Zn S bond formation quenches radiative decay to the valence band from defect states, possibly by methanethiolate adsorption filling oxygen vacancies.

The adsorption of 1-dodecanethiol at room temperature and at 75 °C on submicron cuprous and cupric oxide particles suspended in ethanol has been investigated by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy. Thiol adsorption occurs in all cases via Cu-S bond formation, with partial dissolution of CuO at 75 °C and formation of a copper-thiolate complex replacement layer. Regardless of temperature, the surface of the CuO particles is essentially completely reduced to either Cu2O or metallic copper, as evidenced by loss of the characteristic Cu(2+) XPS features of dried powder samples. Companion ultrahigh-vacuum studies have been performed by dosing clean, oxygen-dosed, and ozone-treated single crystal Cu(111) with methanethiol (MT) gas at room temperature. In the latter case, the surface corresponds to CuO/Cu(111). XPS confirms MT adsorption in all cases, with an S 2p peak binding energy of 162.9 ± 0.1 eV, consistent with methanethiolate adsorption. Heating of MT-covered Cu(111) and oxygen-dosed Cu(111) leads to decomposition/desorption of the MT by 100 °C and formation of copper sulfide with an S 2p binding energy of 161.8 eV. Dosing CuO/Cu(111) with 50-200 L of MT leads to only partial reduction/removal of the CuO surface layers prior to methanethiolate adsorption. This is confirmed by ultraviolet photoelectron spectroscopy (UPS), which measures the occupied states near the Fermi level. For both the colloidal CuO and single crystal CuO/Cu(111) studies, the reduction of the Cu(2+) surface is believed to occur by formation and desorption of the corresponding dithiol prior to thiolate adsorption.

ZnO is an alternative to TiO 2 -based dye-sensitized solar cells (DSSCs). Adsorption of cis -ruthenium-bis[2,2′-bipyridine]-bis[4-thiopyridine] onto ZnO nanorods has been studied using X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS). XPS indicates chemisorption with a surface density of ca. 1 × 10 15 molecules/cm 2 , confirming the possibility of using thiol-terminated dyes for ZnO-based DSSC devices. The energy level diagram, based on UPS and absorbance spectroscopy, indicates that the LUMO of this dye is lower in energy than the ZnO conduction band edge, providing minimal enthalpic driving force for photovoltaic electron injection. However, optimization of thiol-functionalized Ru dyes could result in competitive ZnO-based DSSCs.

The interaction of cecropin P1 (CP1) with Escherichiacoli was investigated to gain insight into the time-dependent antimicrobial action. Biophysical characterizations of CP1 with whole bacterial cells were performed using both fluorescent and colorimetric assays to investigate the role of membrane permeability and lipopolysaccharide (LPS) binding in lytic behavior. The kinetics of CP1 growth inhibition assays indicated a minimal inhibitory concentration (MIC) of 3 microM. Bactericidal kinetics at the MIC indicated rapid killing of E.coli (

The studies presented here explore antimicrobial peptide preferential binding behavior for a target pathogen, Escherichia coli O157:H7. A modified immunoassay and surface plasmon resonance were employed to evaluate immobilized peptide binding of whole bacterial cells. The knowledge gained may guide the rational design of peptides with enhanced species binding selectivity.

Nanocrystalline zinc oxide has been functionalized with 11-triethoxysilylundecal to introduce chemical reactivity for subsequent molecular attachment while preserving its unique photoluminescence (PL) properties. Silane bonding is confirmed using FTIR and photoelectron spectroscopy, with a total Si concentration of 3 to 4 atomic %. PL measurements demonstrate a 2-fold enhancement of its UV peak and maintenance of its visible peak compared to control samples. Enhancement of the UV peak is likely due to a decrease in the surface-dependent nonradiative recombination process. These results lay the framework for sensor fabrication, with the aldehyde groups available to bind analytes that would alter the PL spectrum.

Despite its remarkable materials properties, the structure of spider dragline silk has remained unsolved. Results from two probe microscopy techniques provide new insights into the structure of spider dragline silk. A soluble synthetic protein from dragline silk spontaneously forms nanofibers, as observed by atomic force microscopy. These nanofibers have a segmented substructure. The segment length and amino acid sequence are consistent with a slab-like shape for individual silk protein molecules. The height and width of nanofiber segments suggest a stacking pattern of slab-like molecules in each nanofiber segment. This stacking pattern produces nano-crystals in an amorphous matrix, as observed previously by NMR and x-ray diffraction of spider dragline silk. The possible importance of nanofiber formation to native silk production is discussed. Force spectra for single molecules of the silk protein demonstrate that this protein unfolds through a number of rupture events, indicating a modular substructure within single silk protein molecules. A minimal unfolding module size is estimated to be around 14 nm, which corresponds to the extended length of a single repeated module, 38 amino acids long. The structure of this spider silk protein is distinctly different from the structures of other proteins that have been analyzed by single-molecule force spectroscopy, and the force spectra show correspondingly novel features.

Spider silks are protein-based “biopolymer” filaments or threads secreted by specialized epithelial cells as concentrated soluble precursors of highly repetitive primary sequences. Spider dragline silk is a flexible, lightweight fiber of extraordinary strength and toughness comparable to that of synthetic high-performance fibers. We sought to “biomimic” the process of spider silk production by expressing in mammalian cells the dragline silk genes ( ADF-3 / MaSpII and MaSpI ) of two spider species. We produced soluble recombinant (rc)–dragline silk proteins with molecular masses of 60 to 140 kilodaltons. We demonstrated the wet spinning of silk monofilaments spun from a concentrated aqueous solution of soluble rc–spider silk protein (ADF-3; 60 kilodaltons) under modest shear and coagulation conditions. The spun fibers were water insoluble with a fine diameter (10 to 40 micrometers) and exhibited toughness and modulus values comparable to those of native dragline silks but with lower tenacity. Dope solutions with rc–silk protein concentrations >20% and postspinning draw were necessary to achieve improved mechanical properties of the spun fibers. Fiber properties correlated with finer fiber diameter and increased birefringence.