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Bixin and norbixin are extracted from annatto seeds, and the residual seed waste can be used as a potential source of annatto starch (AS), contributing to the circular economy of the regional communities where the resource is grown/processed. To assess AS suitability as a food ingredient, its physicochemical, antioxidant, microstructural, and functional properties were evaluated after being purified by: Soaking in sodium metabisulfite solution (low purity), defatting for removing lipids (medium purity), alkaline treatment for extracting protein (medium purity), and combined defatting/alkaline (high purity) treatments. AS degree of purity affected all the evaluated parameters. The ζ-potential values ranged between − 18.30 and − 24.10 mV and those of the antioxidant activity between 0.52 and 1.14 µg TE/g (ABTS•+ assay). AS presented a heterogeneous morphology with granules tending to agglomerate, and the mean Sauter diameter varied from 26.8 to 31.1 µm. FTIR spectroscopy showed that protein molecules were present despite the alkaline treatment. X-ray patterns pinpointed that the starch crystalline region was not modified by the deproteinization treatment. The apparent viscosity and viscoelastic properties of gelatinized starch dispersions increased when lipids and proteins were simultaneously removed. The swelling power (21.44–22.71 g/g), solubility index (21.77–40.43%), water absorption (3.9–4.56 g/g), and oil absorption (1.78–2.41 g/g) increased with the purification degree. The in vitro digestibility assay showed that AS presented a higher fraction of slowly digestible starch (36.57–40.68%) than rapidly digestible and resistant starch fractions. This work demonstrates that AS has suitable functional properties that open the possibility for its use in the food industry.

Brosimum alicastrum is a native tree widely distributed in the Yucatan peninsula where is called Ramon. Some studies have reported that Ramon seeds contain high starch content, recently used in developing novel and sustainable biomaterials. This work aimed to evaluate the effect of the extractive solution on the starch isolation Ramon seed flour; for that, distilled water (S1) and NaOH solution (S2) were used. The Ramon starch yield was 28.0 ± 1.4% and 31.9 ± 1.7% for S1 and S2. The morphology of starches was observed with scanning electronic microscopy, the functional groups were determined through Fourier-transform Infrared Spectroscopy and crystallinity was calculated by X-ray diffraction analysis. The results indicate that both types of starch presented spherical morphology, similar functional groups and crystallinity values, suggesting that both extraction methods are suitable. The starches isolated exhibited similar thermal behavior assessed by differential scanning calorimetry and thermogravimetric analysis.

Multiple experiments on the electron transport through solid-state junctions based on different proteins have suggested that the dominant transport mechanism is quantum tunneling (or coherent trans...

Physicochemical and rheological properties, total phenolic content (TPC), capsaicinoids identification and quantification, antioxidant activity (AA) and sensorial analysis were determined on two ripening stages of habanero (Capsicum chinense Jacq.) pepper pastes added with lemon essential oil (LEO) as natural preservative and subjected to thermal process. Rheological parameters indicated that habanero chili pastes with orange ripening stage and thermal processing presented the higher consistency coefficient, flow index, and viscoelastic (G´ and G´´) behavior values. The addition of LEO favored the increment of TPC and AA, as well as color preservation. Thermal processing potentiated total capsaicinoid content (TCC), TPC, and AA, but affected the color characteristics. The combination of LEO and thermal processing significantly affect the sensorial attributes in two of the three sensorial tests performed. These results suggested that apart from sensorial perception, the natural preservative LEO and the thermal processing improved physicochemical and rheological properties as well as biological activity of habanero pastes of the two ripening stage increasing habanero pepper quality and marketing possibilities.

Understanding charge transport in DNA molecules is a long-standing problem of fundamental importance across disciplines1,2. It is also of great technological interest due to DNA’s ability to form versatile and complex programmable structures. Charge transport in DNA-based junctions has been reported using a wide variety of set-ups2–4, but experiments so far have yielded seemingly contradictory results that range from insulating5–8 or semiconducting9,10 to metallic-like behaviour11. As a result, the intrinsic charge transport mechanism in molecular junction set-ups is not well understood, which is mainly due to the lack of techniques to form reproducible and stable contacts with individual long DNA molecules. Here we report charge-transport measurements through single 30-nm-long double-stranded DNA (dsDNA) molecules with an experimental set-up that enables us to address individual molecules repeatedly and to measure the current–voltage characteristics from 5 K up to room temperature. Strikingly, we observed very high currents of tens of nanoamperes, which flowed through both homogeneous and non-homogeneous base-pair sequences. The currents are fairly temperature independent in the range 5–60 K and show a power-law decrease with temperature above 60 K, which is reminiscent of charge transport in organic crystals. Moreover, we show that the presence of even a single discontinuity (‘nick’) in both strands that compose the dsDNA leads to complete suppression of the current, which suggests that the backbones mediate the long-distance conduction in dsDNA, contrary to the common wisdom in DNA electronics2–4. Measurements of electrical conductance in double-stranded DNA suggest that the backbones mediate the long-distance conduction in dsDNA, contrary to the common wisdom in DNA electronics.

Wound healing is fundamental to restore the tissue integrity. A topical study of the influence of Aloe vera hydrogel, formulated with 1,2-propanediol (propanediol) and triethanolamine (TEA), on the skin wound-healing process was investigated in female Wistar rats. FTIR spectroscopy confirms the presence of carboxylic acid and methyl ester carboxylate groups related with important compounds that confer the hydrogel a good interaction with proteins and growth factors. SEM images show a microstructure and micro-roughness that promote a good adhesion to the wound. Therefore, the swelling kinetics and the contact angle response contribute to the understanding of the in vivo results of the animal test. The results indicated that the Aloe vera hydrogel, prepared with propanediol and TEA, together with its superficial characteristics, improve its rapid penetration without drying out the treated tissue. This produced a positive influence on inflammation, angiogenesis, and wound contraction, reducing 29% the total healing time, reaching the total closure of the wound in 15 days.

The ternary edible films based on commercial or bio-chemical chitosan (CCh or BCh) and starch (S) with different concentration of gallic acid (GA) were produced by casting. This work analyzed the effect of different type of Ch and GA concentrations (1.25 mg/gTB and 2.5 mg/gTB) on the rheological properties of the film-forming solutions, as well as physicochemical (thickness, moisture content, swelling index, water vapor permeability (WVP), tensile strength, microstructure, opacity, and color) and antioxidant properties of the edible films themselves. The chemical cross-linking between the GA and Ch into the edible films of biopolymers could form of ester linkages between the carboxyl groups of GA and the hydroxyl groups of Ch. Results showed that the ternary edible films of BCh-S-GA5.0 resulted with a positive effect on their rheological (η0, λ, and p), physicochemical (WVP, swelling, tensile strength, microstructure) and antioxidant properties. The greatest incorporation of polyphenol into the BCh-S-GA5.0 films greatly reduced WVP and swelling values in approximately 61.01% and 23%, respectively also the tensile strength value increased to 37.372 MPa. The ternary edible films developed in this study showed many desirable characteristics, which could potentially be used as bioactive packaging films for food applications.

The effect of temperature (60, 70, 80 and 90 ºC) and time (30, 45, 60, 75 and 90 min) on citric acid extraction of Haden mango ( Mangifera indica L . cv. Haden) peel pectin was evaluated in the present study. In order to obtain a better understanding of both the extraction process and the characteristics of the pectin (obtained from an agro-industrial waste) for a future scaling process, the following characterizations were performed: 1) Kinetic, with the maximum extraction times and yields at all evaluated temperatures; 2) thermodynamic, obtaining activation energies, enthalpies, entropies and Gibbs free energies for each stage of the process; 3) physicochemical (chemical analysis, monosaccharide composition, degree of esterification, galacturonic acid content, free acidity, Fourier-transform infrared spectroscopy, thermogravimetric and derivative thermogravimetric analyses) and; 4) economical, of the pectin with the highest yield. The mango Haden peel pectin was found to be characterized by a high-esterified degree (81.81 ± 0.00 %), regular galacturonic acid content (71.57 ± 1.26 %), low protein (0.83 ± 0.05 %) and high ash (3.53 ± 0.02 %) content, low mean viscometric molecular weight (55.91 kDa) and high equivalent weight (3657.55 ± 8.41), which makes it potentially useful for food, pharmaceutical and environmental applications such as delivery system, gelling agent or as an emulsifier.Statement of NoveltyThe novelty of this work lies in the valorization of an agro-industrial waste (Haden mango peel) through the kinetic, thermodynamic, physicochemical, and economic characterization of a product obtained (pectin). This work contributes to laying the groundwork for an industrial scale-up for pectin production in a mango processing industry.

Currently, nanotechnology is perceived as a promising science that produces materials with diverse unique properties at a nanometric scale. Biocompatibility tests of poly-ε-caprolactone nanofibers, embedded with silver nanoparticles manufactured by means of the electrospinning technique, were carried out in Wistar rats to be used as oral dressings for the eradication of bacteria. Solutions of 12.5, 25, 50 and 100 mM of silver nitrate were made using N-dimethylformamide (DMF) and tetrahydrofuran (THF) as reducing solvents with 8% of poly-ε-caprolactone (PCL) polymer. The solutions were electrospun, and the nanofibers obtained in the process were characterized by infrared spectroscopy, Raman spectroscopy, dark field optical microscopy, scanning electron microscopy and X-ray scattering spectroscopy. The nanofibers had an average diameter of 400 ± 100 nm. Once the characterization of the material was done, three implants of each concentration of the nanofibers were formed and placed in the subcutaneous tissue of the rats. Three experimental subjects were used, leaving the material in them for a length of two, four and six weeks, respectively. The rats showed good healing, with the lesions completely healed at four weeks after implantation. After that time, biopsies were taken, and histopathological sections were made to evaluate the inflammatory infiltrate. The tissues of the rats presented chronic inflammatory infiltrate composed mainly of lymphocytes and giant multinucleated cells. The material was rejected by the rats when a layer of collagen and fibroblasts was produced, coating the material, a process characteristic of a foreign body reaction.

The objective of this work was the recovery of chitosan by ultrasound-assisted extraction (UAE) from white shrimp (Litopenaeus vannamei) chitin, and the physicochemical and structural characterization of the obtained biopolymer, as well as its antimicrobial effect on Pythium ultimum growth. A 23 factorial design was used to evaluate chitosan extraction conditions. Instrumental analysis techniques for chitosan characterization and radial growth inhibition, as an antifungal activity test, were performed. The ultrasonically extracted chitosan (UC) reached a yield of 86.96% with 100% solubility, a degree of deacetylation (DDA) &gt, 78%, molecular weight (MW) of 3.928 &times, 105 g mol&minus, 1, and a crystallinity index (Icr) of 87%, calculated through nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy (FTIR), size exclusion chromatography (SEC), and X-ray diffraction (XRD), respectively. The inhibitory activity of the chitosan was evaluated against the oomycete Pythium ultimum, observing a 93% radial inhibition over 24 h. UAE proved to be an excellent alternative to the conventional deacetylation, reducing reaction time and obtaining a UC with higher MW and (Icr) than the commercial one, which could potentiate its applications.

Tangerine (Citrus reticulata. CRP) and grapefruit (Citrus paradisi. CPP) pectins obtained by ultrasound-assisted extraction (UAE) and conventional extraction (CE) using citric acid were characterized to establish their potential uses as an alternative source of commercial pectin. The pectins obtained by UAE and CE presented a pseudoplastic fluid characteristic with shear thinning behavior, a high esterification degree (CRP 82.30–71.81% and CPP 84.25–72.15%) and were of commercial quality based on galacturonic acid content (CRP 76.03% and CPP 76.03–71.01%). CPP presented greater viscosimetric molecular weight than CRP. Meanwhile, CRP presented greater polyphenol and protein content with respect CPP. The functional properties were influenced by citrus source and extraction method. UAE favored greater yields in a shorter time (CPP: 26.05%, 30 min; CRP: 13.46%, 15 min) compared to CE. UAE combined with the use of citric acid offers an effective alternative for obtaining high-quality pectins with lower polluting effluent, time and energy requirements.

There has been different synthetic route used for the synthesis of zirconia mixed metal oxide nanoparticles. The different synthetic methods coupled with other factors like concentration, PH, type of precursor used etc help to synthesize zirconia mixed metal oxide nanoparticles having different physicochemical properties. This paper discusses the different synthetic routes of sol-gel, hydrothermal and coprecipitation method for the formation of zirconia in combination with other metal oxide to form zirconia mixed metal oxide nanoparticles, the physicochemical properties of the synthesized zirconia mixed metal oxide nanoparticle, their characterization and application.

We present a theoretical study of the blue-copper azurin extracted from Pseudomonas aeruginosa and several of its single amino acid mutants. For the first time, we consider the whole structure of this kind of protein rather than limiting our analysis to the copper complex only. This is accomplished by combining fully ab initio calculations based on density functional theory with atomic-scale molecular dynamics simulations. Beyond the main features arising from the copper complex, our study reveals the role played by the peripheral parts of the proteins. In particular, we find that oxygen atoms belonging to carboxyl groups which are distributed all over the protein contribute to electronic states near the HOMO. The contribution of the outer regions to the electronic structure of azurins had so far been overlooked. Our results highlight the need to investigate them thoroughly; this is especially important in prospect of understanding complex processes such as the electronic transport through metal-metalloprotein-metal junctions, We thank the financial support from the Spanish MINECO (MAT2014-58982-JIN, FIS2017-84057-P, MDM-2014-0377 and MAT2017-83273-R). J. G. V. acknowledges funding from a Marie Sklodowska-Curie Fellowship within the Horizons 2020 framework (grant number DLV-795286)

The effect of temperature (60, 70, 80, and 90 °C) and time (30, 45, 60, 75, and 90 min) on citric acid extraction of Haden mango (Mangifera indica L. cv. Haden) peel pectin was evaluated in the present study. In order to obtain a better understanding of both the extraction process and the characteristics of the pectin (obtained from an agro-industrial waste) for a future scaling process, the following characterizations were performed: (1) Kinetic, with the maximum extraction times and yields at all evaluated temperatures, (2) thermodynamic, obtaining activation energies, enthalpies, entropies, and Gibbs free energies for each stage of the process, (3) physicochemical (chemical analysis, monosaccharide composition, degree of esterification, galacturonic acid content, free acidity, Fourier-transform infrared spectroscopy, thermogravimetric and derivative thermogravimetric analyses), and (4) economical, of the pectin with the highest yield. The Haden mango peel pectin was found to be characterized by a high-esterified degree (81.81 ± 0.00%), regular galacturonic acid content (71.57 ± 1.26%), low protein (0.83 ± 0.05%) and high ash (3.53 ± 0.02%) content, low mean viscometric molecular weight (55.91 kDa), and high equivalent weight (3657.55 ± 8.41), which makes it potentially useful for food applications.

Graphical abstract, Highlights • Ultrasound is a fast method for phenolic compounds recovery from C. chinense leaves. • Solvent polarity has a strong effect on the recovery of phenolic compounds. • Dielectric constant was propose to predict the most appropriate solvent for phenolic extraction. • Antioxidant activity correlates with total phenolic content of C. chinense leaves extracts. • Identification of phenolic compounds was performed by UPLC-PDA-ESI-MS/MS., Phenolic compounds are secondary metabolites involved in plant adaptation processes. The development of extraction procedures, quantification, and identification of this compounds in habanero pepper (Capsicum chinense) leaves can provide information about their accumulation and possible biological function. The main objective of this work was to study the effect of the UAE method and the polarity of different extraction solvents on the recovery of phenolic compounds from C. chinense leaves. Quantification of the total phenolic content (TPC), antioxidant activity (AA) by ABTS+ and DPPH radical inhibition methods, and the relation between the dielectric constant (ε) as polarity parameter of the solvents and TPC using Weibull and Gaussian distribution models was analyzed. The major phenolic compounds in C. chinense leaves extracts were identified and quantified by UPLC-PDA-ESI-MS/MS. The highest recovery of TPC (24.39 ± 2.41 mg GAE g−1 dry wt) was obtained using MeOH (50%) by UAE method. Correlations between TPC and AA of 0.89 and 0.91 were found for both radical inhibition methods (ABTS+ and DPPH). The Weibull and Gaussian models showed high regression values (0.93 to 0.95) suggesting that the highest phenolic compounds recovery is obtained using solvents with “ε” values between 35 and 52 by UAE. The major compounds were identified as N-caffeoyl putrescine, apigenin, luteolin and diosmetin derivatives. The models presented are proposed as a useful tool to predict the appropriate solvent composition for the extraction of phenolic compounds from C. chinense leaves by UAE based on the “ε” of the solvents for future metabolomic studies.

Introduction. Tissue engineering is an elementary necessity for several applications in the biomedical field through the use of several biopolymers derived from plants. Larrea tridentata (LT) is a very used plant for various medicinal applications with interesting properties; however, its use into cellulose hydrogels for possible regenerative therapeutics is still limited. Cellulose films could be applied in medical field as wound healing, scaffold for connective tissue for periodontal applications, and so on. The aim of this study was to evaluate the mechanical properties and in vivo and in vitro biocompatibility of cellulose hydrogels that have been enriched with LT in a rat model. Methods. By in vivo and in vitro assays, the concentration of LT was varied from 1 to 5 wt%, respectively. Hydrogel films were implanted intramuscularly into female Wistar rats, 250 g in weight and aged 2 months, to analyze their cytocompatibility and biocompatibility. Results. No case showed any evidence of inflammation or toxicity. Regarding cell morphology and adhesion, the prepared LT cellulose films had better cytocompatibility values than when polystyrene (PS) dishes were used as the control. In all cases, the results suggest that the addition of LT to the hydrogel films did not affect their cytocompatibility or biocompatibility properties and increases their clinical application due to the reported uses of LT. Conclusions. Cellulose hydrogel films enriched with LT have the potential to be used in the biomedical field acting as regenerative scaffolds.

The physicochemical properties, proximate composition, minerals, total polyphenols, carotenoids, phenolic compounds, antioxidant, and antibacterial activities of ciricote (Cordia dodecandra A. DC.) tropical fruit were investigated. Minerals were quantified by using micro-Energy Dispersive X-Ray Fluorescence. Lutein and β-carotene were identified in ciricote fruit by using UPLC-PDA analysis. The highest values of the total polyphenols content and antioxidant activity were presented in ethanolic crude extracts obtaining by the ultrasonic-assisted method with freeze-dried fruit. The phenolic acids profile was identified and quantified by UPLC-PDA-ESI-MS. The main phenolic acids were caffeoyl hexoside, rufescenolide, quercetin 3-O-rutinoside, and rosmarinic acid. The ciricote extracts presented antibacterial activity against Staphylococus aureus (Gram+) and Salmonella typhymurium (Gram−). In conclusion, the ciricote (Cordia dodecandra A. DC.) tropical fruits could be very useful source of biological macromolecules, micro-elements, and phytochemical compounds for the food and pharmaceutical industry.

Introduction. In our days, several approaches reported the use of natural compounds in medical applications. Among them, pectin and allantoin are nontoxic, biocompatible, and biodegradable; however, its use for possible wound healing therapeutics is still limited. Pectin and allantoin have been applied in pharmaceutical industry and beauty cosmetic and could be also applied as scaffolds for tissue regeneration, wound healing, and so on. The aim of this study was to combine by the first time two natural ingredients to develop a new biomaterial to treat skin injuries in a rat model. Methods. For the hydrogel development, new synthesis parameters were established for the obtaining of the film such as temperature, mixing velocity and time, and drying temperatures as well. To enrich the film, the allantoin concentrations were set at 90 wt% and 100 wt% of pectin used. By in vivo assay, films were tested in wound healing in female Wistar rats, 190 ± 10 g in weight and 2 months aged. Results. The obtained films comprise 2 well-differentiated layers, one layer rich in allantoin, which will be the regenerative layer, and one rich in pectin, which will work as an antimicrobial and protective layer to the wound. These were characterized by swelling kinetics, Fourier transform of the infrared spectrum of absorption (FTIR) spectroscopy, and contact angle. The morphology and topography were determined by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). In vivo assay showed remarkable reduce in a time period in a wound healing process when the film was used. The results show that the use of PA (Pectin-Allantoin) hydrogel reduces the total healing time by 25% approximately. Conclusions. Pectin-Allantoin (PA) film has potential use in medical applications as wound healing material promoting healthy tissue renewal.

Bioactive Phenols-loaded chitosan nanoparticles (PL-CNps) were developed by ionic gelation from Persian lemon (Citrus latifolia) waste (PLW) and chitosan nanoparticles. Response Surface Methodology (RSM) was used to determine the optimal Ultrasound-Assisted Extraction (UAE) conditions for the total phenolic compounds (TPC) recovery from PLW (58.13 mg GAE/g dw), evaluating the ethanol concentration, extraction time, amplitude, and solid/liquid ratio. Eight compounds expressed as mg/g dry weight (dw) were identified by ultra-performance liquid chromatography coupled photo diode array (UPLC-PDA) analysis: eriocitrin (20.71 &plusmn, 0.09), diosmin (18.59 &plusmn, 0.13), hesperidin (7.30 &plusmn, 0.04), sinapic acid (3.67 &plusmn, 0.04), catechin (2.92 &plusmn, 0.05), coumaric acid (2.86 &plusmn, 0.01), neohesperidin (1.63 &plusmn, 0.00), and naringenin (0.44 &plusmn, 0.00). The PL-CNps presented size of 232.7 nm, polydispersity index of 0.182, Z potential of &minus, 3.8 mV, and encapsulation efficiency of 81.16%. The results indicated that a synergic effect between phenolic compounds from PLW and chitosan nanoparticles was observed in antioxidant and antibacterial activity, according to Limpel&rsquo, s equation. Such results indicate that PLW in such bioprocesses shows excellent potential as substrates for the production of value-added compounds with a special application for the food industry.

Licensee MDPI, Basel, Switzerland. Protein-based electronics is an emerging field which has attracted considerable attention over the past decade. Here, we present a theoretical study of the formation and electronic structure of a metal-protein-metal junction based on the blue-copper azurin from pseudomonas aeruginosa. We focus on the case in which the protein is adsorbed on a gold surface and is contacted, at the opposite side, to an STM (Scanning Tunneling Microscopy) tip by spontaneous attachment. This has been simulated through a combination of molecular dynamics and density functional theory. We find that the attachment to the tip induces structural changes in the protein which, however, do not affect the overall electronic properties of the protein. Indeed, only changes in certain residues are observed, whereas the electronic structure of the Cu-centered complex remains unaltered, as does the total density of states of the whole protein, This research was funded by the Spanish MINECO (MAT2014-58982-JIN, FIS2017-84057-P, MDM-2014-0377 and MAT2017-83273-R). J.G.V. acknowledges funding from a Marie Sklodowska-Curie Fellowship within the Horizons 2020 framework (grant number DLV 795286). I.D.-P. thanks the ERC project Fields4CAT (ref. 772391) for financial support

In the growing field of biomolecular electronics, blue-copper Azurin stands out as one of the most widely studied protein in single-molecule contacts. Interestingly, despite the paramount importance of the structure/dynamics of molecular contacts in their transport properties, these factors remain largely unexplored from the theoretical point of view in the context of single Azurin junctions. Here we address this issue using all-atom Molecular Dynamics (MD) of Pseudomonas Aeruginosa Azurin adsorbed to a Au(111) substrate. In particular, we focus on the structure and dynamics of the free/adsorbed protein and how these properties are altered upon single-point mutations. The results revealed that wild-type Azurin adsorbs on Au(111) along two well defined configurations: one tethered via cysteine groups and the other via the hydrophobic pocket surrounding the Cu 2 + . Surprisingly, our simulations revealed that single amino-acid mutations gave rise to a quenching of protein vibrations ultimately resulting in its overall stiffening. Given the role of amino-acid vibrations and reorientation in the dehydration process at the protein-water-substrate interface, we suggest that this might have an effect on the adsorption process of the mutant, giving rise to new adsorption configurations.

Motivated by a recent experiment [C. Guo et al., Proc. Natl. Acad. Sci. U. S. A. 113, 10785 (2016)], we carry out a theoretical study of electron transport through peptide-based single-molecule junctions. We analyze the pristine hepta-alanine and its functionalizations with a single tryptophan unit, which is placed in three different locations along the backbone. Contrary to expectations from the experiment on self-assembled monolayers, we find that insertion of tryptophan does not raise the electrical conductance and that the resulting peptides instead remain insulating in the framework of a coherent transport picture. The poor performance of these molecules as conductors can be ascribed to the strongly off-resonant transport and low electrode-molecule coupling of the frontier orbitals. Although the introduction of tryptophan increases the energy of the highest occupied molecular orbital (HOMO) of the peptides in the gas phase, the new HOMO states are localized on the tryptophan unit and therefore essentially do not contribute to coherent charge transport.

The adhesion ability and adaptability of bacteria, coupled with constant use of the same bactericides, have made the increase in the diversity of treatments against infections necessary. Nanotechnology has played an important role in the search for new ways to prevent and treat infections, including the use of metallic nanoparticles with antibacterial properties. In this study, we worked on the design of a composite of silver nanoparticles (AgNPS) embedded in poly-epsilon-caprolactone nanofibers and evaluated its antimicrobial properties against various Gram-positive and Gram-negative microorganisms associated with drug-resistant infections. Polycaprolactone-silver composites (PCL-AgNPs) were prepared in two steps. The first step consisted in the reduction in situ of Ag+ions using N,N-dimethylformamide (DMF) in tetrahydrofuran (THF) solution, and the second step involved the simple addition of polycaprolactone before electrospinning process. Antibacterial activity of PCL-AgNPs nanofibers againstE. coli,S. mutans,K. pneumoniae,S. aureus,P. aeruginosa, andB. subtiliswas evaluated. Results showed sensibility ofE. coli,K. pneumoniae,S. aureus, andP. aeruginosa, but not forB. subtilisandS. mutans. This antimicrobial activity of PCL-AgNPs showed significant positive correlations associated with the dose-dependent effect. The antibacterial property of the PCL/Ag nanofibers might have high potential medical applications in drug-resistant infections.

Cactus pear (Opuntia sp.) is a highly perishable fruit that starts to deteriorate after several days of storage at room temperature. After two weeks at room temperature, 70% of the fruit shows signs of deterioration. Cactus pear quality for stored pears depends on harvest techniques and on practices for prolonging shelf life. A pneumatic cauterizing machine with a resistive heating element was used to seal cactus pears on their peduncle. More effective contact between the heater element and fruit was obtained after cutting the peduncle. Internal pulp temperature was measured with NTC thermistors and it was found that after heating at 200 °C for 30 s, pulp temperature increased to 60 °C. Surface temperature was measured with a thermal infrared camera. Cactus pear shelf life, water loss, firmness and ° Brix were evaluated using piston pressures of 50, 100, 150 and 200 kPa during 30 s at cauterizing temperatures of 150, 180, 200 and 240 °C. The best shelf life was obtained after pressing the fruit with 100 kPa during 30 s at a temperature of 200 °C. Thirty-seven days after being cauterized, fruits began to rot, and half of the fruit was not marketable after 63 days. Pulp firmness decreased by 81% after 60 storage days, and soluble solids increased by 105%. Pears that did not seal properly were detected using thermal imaging three days after cauterizing. Pears were sliced and cauterized again unless the rotting area was over 50% and firmness lower than 15 N cm−2.

The physicochemical characteristics, intrinsic viscosity, adsorption dynamics and emulsifying properties of two hawthorn accessions pectins (HP50 and HP55) were evaluated and compared to those obtained for commercial citrus pectin (CP). Mark-Houwink-Kuhn-Sakurada coefficients, aMHKS = 0.71 ± 0.02 and kMHKS = 5.08 × 10− 3 ± 2 × 10− 4 g dL− 1 were obtained from intrinsic viscosity data. The diffusion (Kdiff), penetration (K1) and the rearrangement (K2) constants were determined from adsorption dynamics data of the pectins at the canola oil-water interface. Kdiff was higher and K1 was lower for HP50 than for HP55 and for CP. These results had bearing on the stability of oil-in-water emulsions. Higher Kdiff produced smaller initial droplet sizes, due to the faster diffusion of molecules to the interface, while lower K1 produced longer-term stability, as a more consolidated and stronger interfacial film was formed faster, making arduous the penetration of newly arriving molecules through the monolayer. The rate of creaming was lower the smaller was the initial droplet size and the higher the apparent viscosity of the emulsions.

Introduction: Grape seed oil (GSO) contains unsaturated fatty acids that make it susceptible to degradation, causing it to deteriorate. In this sense, microencapsulation in biopolymer matrices is a good alternative to protect it. Objective: To microencapsulate GSO by spray drying of emulsions stabilized with biopolymer complexes formed from whey protein concentrate (WPC) and hawthorn pectin (HP) from two different cultivars. Methodology: Emulsions were developed with different wall material: GSO ratios (2:1 and 3:1) and percentage of total solids (30 and 40 %). The wall materials were WPC-citrus pectin and WPC-HP from two cultivars (HP55 and HP100, with an esterification degree of 70.3 and 61 %, respectively). The factors evaluated were viscosity, mean surface diameter (d3,2) and morphology of the emulsions, and d3,2, microencapsulation efficiency (MEE) and electron microscopy of the microcapsules. Results: The d3,2 of the emulsions ranged from 1.45 to 2.54 μm, where EWPC-HP100,3:1 exhibited the smallest d3,2. These values were related to the type of pectin and were inversely proportional to the viscosity and solids content. The highest MEE was presented by MWPC-HP100,3:1 (71.29 %), which had the highest viscosity and the lowest d3,2 in the emulsion. Study limitations: The behavior of only two hawthorn cultivars is presented. Originality: There are no reports of the use of HP biopolymer complexes from national cultivars and WPC as wall materials for the protection of bioactive materials. Conclusions: The use of novel biopolymers such as HP (HP55 and HP100) allowed obtaining microcapsules with adequate morphology and high ME

Bioelectronics moves toward designing nanoscale electronic platforms that allow in vivo determinations. Such devices require interfacing complex biomolecular moieties as the sensing units to an electronic platform for signal transduction. Inevitably, a systematic design goes through a bottom-up understanding of the structurally related electrical signatures of the biomolecular circuit, which will ultimately lead us to tailor its electrical properties. Toward this aim, we show here the first example of bioengineered charge transport in a single-protein electrical contact. The results reveal that a single point-site mutation at the docking hydrophobic patch of a Cu-azurin causes minor structural distortion of the protein blue Cu site and a dramatic change in the charge transport regime of the single-protein contact, which goes from the classical Cu-mediated two-step transport in this system to a direct coherent tunneling. Our extensive spectroscopic studies and molecular-dynamics simulations show that the proteins' folding structures are preserved in the single-protein junction. The DFT-computed frontier orbital of the relevant protein segments suggests that the Cu center participation in each protein variant accounts for the different observed charge transport behavior. This work is a direct evidence of charge transport control in a protein backbone through external mutagenesis and a unique nanoscale platform to study structurally related biological electron transfer.

Calorimetry reaches an atomic junction Electrical and thermal conductivity in metals are linked at the macroscopic length scale because electrons carry both heat and current. Cui et al. found that this relationship, the Wiedemann-Franz law, holds down to the atomic scale in gold and platinum (see the Perspective by Segal). They made thermal and electrical conductance measurements through a point contact only one atom thick. In gold, the thermal and electrical conductance was quantized, owing to the electronic band structure of the metal. The experiments pave the way for high-resolution calorimetry and other thermal measurements at the nanoscale. Science , this issue p. 1192 ; see also p. 1125

The effect of surface plasmons on the conductance of single-molecule junctions is studied using a squeezable break junction setup. We show that the conductance of 2,7-diaminofluorene single-molecule junctions can be enhanced upon laser irradiation. Our experimental approach enables us to show that this enhancement is due to the plasmon-induced oscillating field within the nanoscale metal gap of the junctions. The effective plasmon field enhancement within the gap is calculated to be ∼1000. The experimental procedure presented in this work, which enables one to explore the coupling between plasmons and molecular excitations via transport measurements, could potentially become a valuable tool in the field of plexcitonics.

Wollamide B is a cationic antimycobacterial cyclohexapeptide that exhibits activity against Mycobacterium bovis (M. bovis) (IC50 of 3.1 μM). Aiming to define its structural activity relationship (SAR), optimizing potency and pharmacokinetic properties, libraries of analogues were synthesized following a standard Fmoc-based solid phase peptide synthesis approach. The antimycobacterial activities of wollamide B and all the synthesized analogues were tested against Mycobacterium tuberculosis (Mtb) H37Rv. Parallely, in vitro drug metabolism and pharmacokinetic (ADME) profiling was done for the synthesized compounds to evaluate their drug likeness. Among the 25 synthesized wollamides five of them showed potent activities with MICs ≤ 3.1 μM and found to be nontoxic against human HepG2 cells up to 100 μM. The results of the in vitro ADME profiling revealed the remarkable plasma stability and very good aqueous solubility of the class in general while the metabolic stability was found to be moderate to low. Of particular note, compounds 7c (MIC = 1.1 μM) and 13c (0.6 μM) that exhibited good balance of antimycobacterial activity vs. optimal pharmacokinetic properties could be used as a new lead for further development.

International audience; Motivated by recent experiments, we present here a detailed theoretical analysis of the use of carbon-based conductive tips in scanning tunnelling microscopy. In particular, we employ ab initio methods based on density functional theory to explore a graphitic, an amorphous carbon and two diamond-like tips for imaging with a scanning tunnelling microscope (STM), and we compare them with standard metallic tips made of gold and tungsten. We investigate the performance of these tips in terms of the corrugation of the STM images acquired when scanning a single graphene sheet. Moreover, we analyse the impact of the tip-sample distance and show that it plays a fundamental role in the resolution and symmetry of the STM images. We also explore in depth how the adsorption of single atoms and molecules in the tip apexes modifies the STM images and demonstrate that, in general, it leads to an improved image resolution. The ensemble of our results provides strong evidence that carbon-based tips can significantly improve the resolution of STM images, as compared to more standard metallic tips, which may open a new line of research in scanning tunnelling microscopy.

Motivated by recent experiments, we present here a systematic ab-initio study of the length dependence of the thermal conductance of single-molecule junctions. We make use of a combination of density functional theory with non-equilibrium Green's function techniques to investigate the length dependence of the phonon transport in single alkane chains, contacted with gold electrodes via both thiol and amine anchoring groups. Additionally, we study the effect of the substitution of the hydrogen atoms in the alkane chains by heavier fluorine atoms to form polytetrafluoroethylenes. Our results demonstrate that (i) the room-temperature thermal conductance is fairly length-independent for chains with more than 5 methylene units and (ii) the efficiency of the thermal transport is strongly influenced by the strength of the phononic metal-molecule coupling. Our study sheds new light onto the phonon transport in molecular junctions, and it provides clear guidelines for the design of molecular junctions for thermal management., Comment: 9 pages, 7 figures

Present trends in the miniaturization of electronic devices suggest that ultimately single atoms and molecules may be used as electronically active elements in a variety of applications. In this context, there is an obvious request for a theory that can elucidate the transport mechanisms at the single-molecule scale, and in turn help in the future engineering of molecular devices. We present here a candidate to such a theory, which based on the combination of quantum chemistry methods and Green functions techniques. Our main goal in this work is to show how the electronic structure of single atoms and molecules controls the macroscopic electrical properties of the circuits in which they are used as building blocks. In particular, we review our work on three basic problems that have received a special experimental attention in the last years: (i) the conductance of a single-atom contact; (ii) the conductance of a hydrogen molecule; and (iii) the current through single organic molecules.

© 2015 AIP Publishing LLC. A combined experimental and theoretical study of the magneto-optic properties of a series of nickel antidot thin films is presented. The hole diameter varies from 869 down to 636 nm, while the lattice periodicity is fixed at 920 nm. This results in an overall increase of the polar Kerr rotation with decreasing hole diameter due to the increasing surface coverage with nickel. In addition, at photon energies of 2.7 and 3.3 eV, where surface-plasmon excitations are expected, we observe distinct features in the polar Kerr rotation not present in continuous nickel films. The spectral position of the peaks exhibits a red shift with decreasing hole size. This is explained within the context of an effective medium theory by a change in the effective dielectric function of the Ni thin films., H.F. gratefully acknowledges China Scholarship Council (CSC) for financial support and André Schirmeisen for the data of Ni film. A.G.-M. and B.C. acknowledge funding from Spanish Ministry of Economy and Competitiveness through grants “FUNCOAT” CONSOLIDER CSD2008-00023 and “MAPS” MAT2011-29194-C02-01. J.C.C. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (Contract No. FIS2011-28851-C02-01) and from the Comunidad de Madrid (Contract No. S2013/MIT-2740). E.M.A. and M.G. acknowledge financial support by the European Union under the project CosmoPHOS with the number “3100337”.

We describe the synthesis and single-molecule electrical transport properties of a molecular wire containing a π-extended tetrathiafulvalene (exTTF) group and its charge-transfer complex with F4TCNQ. We form single-molecule junctions using the in situ break junction technique using a homebuilt scanning tunneling microscope with a range of conductance between 10 G0 down to 10-7 G0. Within this range we do not observe a clear conductance signature of the neutral parent molecule, suggesting either that its conductance is too low or that it does not form a stable junction. Conversely, we do find a clear conductance signature in the experiments carried out on the charge-transfer complex. Due to the fact we expected this species to have a higher conductance than the neutral molecule, we believe this supports the idea that the conductance of the neutral molecule is very low, below our measurement sensitivity. This idea is further supported by theoretical calculations. To the best of our knowledge, these are the first reported single-molecule conductance measurements on a molecular charge-transfer species, Financial support by the European Commission (EC) FP7 ITN “MOLESCO” Project No. 606728, the European Research Council (ERC-436 2012 ADG_20120216-Chirallcarbon), the CAM (PHOTOCARBON project S2013/MIT-2841, NANOFRONTMAG-CM project S2013/MIT-2850 and MAD2D project S2013/MIT-3007), FP7- ENERGY-2012-1-2STAGE-number 309223 (PHOCS) and the Spanish MICINN/MINECO through the programs MAT2011- 25046, MAT2014-57915-R and PRI-PIBUS-2011-1067 is acknowledged. MB was partly supported by a FY2012 (P12501) Postdoctoral Fellowship for Foreign Researchers from the Japan Society for Promotion of Science (JSPS) and by a JSPS KAKENHI, “Grant-in-Aid for JSPS Fellows”, grant no. 24·02501. YA is also thankful to another KAKENHI, “Grantin-Aid for Scientific Research on Innovation Areas, Molecular Architectonics: Orchestration of Single Molecules for Novel Functions” (#25110009). LAZ was supported by the Spanish MICINN under Grant MAT2011-23627. FP acknowledges support by the Carl-Zeiss foundation and the Collaborative Research Center 767 “Controlled Nanosystems: Interaction and Interfacing to the Macroscale”

We report conductance and thermopower measurements of metallic atomic-size contacts, namely gold and platinum, using a scanning tunneling microscope (STM) at room temperature. We find that few-atom gold contacts have an average negative thermopower, whereas platinum contacts present a positive thermopower, showing that for both metals, the sign of the thermopower in the nanoscale differs from that of bulk wires. We also find that the magnitude of the thermopower exhibits minima at the maxima of the conductance histogram in the case of gold nanocontacts while for platinum it presents large fluctuations. Tight-binding calculations and Green's function techniques, together with molecular dynamics simulations, show that these observations can be understood in the context of the Landauer-Büttiker picture of coherent transport in atomic-scale wires. In particular, we show that the differences in the thermopower between these two metals are due to the fact that the elastic transport is dominated by the 6s orbitals in the case of gold and by the 5d orbitals in the case of platinum.

Single-molecule junctions with high rectification ratios can be realized by exposing different electrode surface areas to an ionic liquid.

An enantiospecific synthesis of a monocyclic core of the antifungal sordarins and sordaricins has been achieved. This synthesis is based on the conversion of (+)-3,9-dibromocamphor into a 1,1,2,2,5-pentasubstituted cyclopentane bearing all the key functionalities present in these antifungals.

Fabrication of structures at the atomic scale is now possible using state-of-the-art techniques for manipulating individual atoms1, and it may become possible to design electrical circuits atom by atom. A prerequisite for successful design is a knowledge of the relationship between the macroscopic electrical characteristics of such circuits and the quantum properties of the individual atoms used as building blocks. As a first step, we show here that the chemical valence determines the conduction properties of the simplest imaginable circuit—a one-atom contact between two metallic banks. The extended quantum states that carry the current from one bank to the other necessarily proceed through the valence orbitals of the constriction atom. It thus seems reasonable to conjecture that the number of current-carrying modes (or ‘channels’) of a one-atom contact is determined by the number of available valence orbitals, and so should strongly differ for metallic elements in different series of the periodic table. We have tested this conjecture using scanning tunnelling microscopy and mechanically controllable break-junction techniques2,3 to obtain atomic-size constrictions for four different metallic elements (Pb, Al, Nb and Au), covering a broad range of valences and orbital structures. Our results demonstrate unambiguously a direct link between valence orbitals and the number of conduction channels in one-atom contacts.

International audience; We present here an exhaustive ab initio study of the use of carbon-based tips as electrodes in single-molecule junctions. Motivated by recent experiments, we show that carbon tips can be combined with other carbon nanostructures, such as graphene, to form all-carbon molecular junctions with molecules like benzene or C 60. Our results show that the use of carbon tips can lead to relatively conductive molecular junctions. However, contrary to junctions formed with standard metals, the conductance traces recorded during the formation of the all-carbon single-molecule junctions do not exhibit clear conductance plateaus, which can be attributed to the inability of the hydrogenated carbon tips to form chemical bonds with the organic molecules. Additionally, we explore here the use of carbon tips for scanning tunneling microscopy and show that they are well suited for obtaining sample images with atomic resolution.

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of the American Chemical Society, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/ja3100116, We present a theoretical study of electron transport through single-molecule junctions incorporating a Pt6 metal cluster bound within an organic framework. The insertion of this molecule between a pair of electrodes leads to a fully atomically engineered nanometallic device with high conductance at the Fermi level and two sequential high on/off switching states. The origin of this property can be traced back to the existence of a degenerate HOMO consisting of two asymmetric orbitals with energies close to the Fermi level of the metal leads. The degeneracy is broken when the molecule is contacted to the leads, giving rise to two resonances that become pinned to the Fermi level and display destructive interference, This research was supported by the Comunidad de Madrid through the project NANOBIOMAGNET S2009/MAT1726, by the Generalitat Valenciana through the project PROMETEO2012/011 and by the Spanish MICINN under the Grant Nos. FIS2010-21883 and CONSOLIDER CSD2007-0010. EL was funded by the EU through the ELFOS Network (FP7-ICT2009-6)

Atomic and single-molecule junctions represent the ultimate limit to the miniaturization of electrical circuits. They are also ideal platforms to test quantum transport theories that are required to describe charge and energy transfer in novel functional nanodevices. Recent work has successfully probed electric and thermoelectric phenomena in atomic-scale junctions. However, heat dissipation and transport in atomic-scale devices remain poorly characterized due to experimental challenges. Here, using custom-fabricated scanning probes with integrated nanoscale thermocouples, we show that heat dissipation in the electrodes of molecular junctions, whose transmission characteristics are strongly dependent on energy, is asymmetric, i.e. unequal and dependent on both the bias polarity and the identity of majority charge carriers (electrons vs. holes). In contrast, atomic junctions whose transmission characteristics show weak energy dependence do not exhibit appreciable asymmetry. Our results unambiguously relate the electronic transmission characteristics of atomic-scale junctions to their heat dissipation properties establishing a framework for understanding heat dissipation in a range of mesoscopic systems where transport is elastic. We anticipate that the techniques established here will enable the study of Peltier effects at the atomic scale, a field that has been barely explored experimentally despite interesting theoretical predictions. Furthermore, the experimental advances described here are also expected to enable the study of heat transport in atomic and molecular junctions, which is an important and challenging scientific and technological goal that has remained elusive., Comment: supporting information available in the journal web site or upon request

We fabricate and characterize carbon-fiber tips for their use in combined scanning tunneling and force microscopy based on piezoelectric quartz tuning fork force sensors. An electrochemical fabrication procedure to etch the tips is used to yield reproducible sub-100-nm apex. We also study electron transport through single-molecule junctions formed by a single octanethiol molecule bonded by the thiol anchoring group to a gold electrode and linked to a carbon tip by the methyl group. We observe the presence of conductance plateaus during the stretching of the molecular bridge, which is the signature of the formation of a molecular junction., Conference Proceeding (Trends in NanoTechnology 2011, Tenerife SPAIN); Nanoscale Research Letters, (2012) 7:254