Remote activation and detection of up-converted luminescence via surface plasmon polaritons propagating in a silver nanowire

In this paper, we demonstrate remote activation and detection of the 2-photon up-conversion luminescence via surface plasmon polaritons propagating in a long silver nanowire. The hybrid nanostructure was assembled by locally depositing a submicron droplet of nanocrystal-containing colloidal solution on one of the ends of the metallic nanowire. When - using a classic confocal microscope - the second end of the nanowire, without the nanocrystals, is illuminated with infrared laser light, we observe strong emission from the same end. Therefore, it indicates that surface plasmon polaritons activated with infrared light at the second end of the nanowire propagate along it and can excite nanocrystals in the droplet at the opposite end. Subsequently, the excited nanocrystals up-convert the energy and by launching surface plasmon polaritons can guide the up-converted luminescence back to the starting point. The emergence of this effect is much more pronounced for a laser polarized along the nanowire. The spectral and temporal character of this emission reveals strong interactions between surface plasmon polaritons and electronic states of the nanocrystals. The details of local and non-local aspects of the effects of remote excitation and guiding of energy in a silver nanowire are elucidated using a unique experimental setup, based on two microscope objectives for spatial separation and control of both excitation and emission beams.

Spectrally selective fluorescence imaging of Chlorobaculum tepidum reaction centers conjugated to chelator-modified silver nanowires

A polyhistidine tag (His-tag) present on Chlorobaculum tepidum reaction centers (RCs) was used to immobilize photosynthetic complexes on a silver nanowire (AgNW) modified with nickel-chelating nitrilo-triacetic acid (Ni-NTA). The optical properties of conjugated nanostructures were studied using wide-field and confocal fluorescence microscopy. Plasmonic enhancement of RCs conjugated to AgNWs was observed as their fluorescence intensity dependence on the excitation wavelength does not follow the excitation spectrum of RC complexes in solution. The strongest effect of plasmonic interactions on the emission intensity of RCs coincides with the absorption spectrum of AgNWs and is observed for excitation into the carotenoid absorption. From the absence of fluorescence decay shortening, we attribute the emission enhancement to increase of absorption in RC complexes.

Furan in roasted, ground and brewed coffee

Coffee is the most popular hot beverage in the world. The annual coffee production in 2010, 2014 and 2016 was 8.1, 9.0 and 9.3 million tons respectively. There are more than 100 coffee species, but only two of them: Arabica (Coffea arabica) and Robusta (Coffea canephora) have gained commercial importance. During roasting of green coffee beans not only desirable compounds are formed, that exert positive influence on the taste and flavour of coffee, but also small quantities of undesirable ones. Furan (C4H4O) is one of the latter. Furan is a volatile compound (boiling temp. of 31.4 oC) formed during thermal processing of food. The toxicity of furan has been well documented and it is classified as “possible human carcinogen” (Group 2B) by the International Agency for Research on Cancer. Various pathways have been reported for furan formation during food processing. It can be formed from carbohydrates, amino acids by their thermal degradation or thermal re-arrangement and by oxidation of ascorbic acid and polyunsaturated acids and carotenoids. High concentrations of furan have been reported in coffee, baked and roasted food and in food subjected to preserving in cans and jars. Furan levels in brewed coffee are typically near or below 120 μg/L, but it can approach thousands μg/kg in roasted whole beans or ground coffee. The highest concentration of furan in roasted coffee reaches the level of 7000 μg/kg. Taking into account that coffee is the most popular hot drink, it becomes the main contributor to furan exposure from dietary sources for adults. In this article the published scientific papers concerned with the presence of furan in roasted non-brewed and brewed coffee have been reviewed. The formation mechanisms and occurrence of furan in coffee and the harmful influence of furan on the consumer health have been discussed.

Acrylamide in food products - eating habits and consumer awareness among Medical School students

INTRODUCTION

Acrylamide is formed in several foods during high-temperature processing. In view of reports written about the neurotoxic, genotoxic and carcinogenic effects of acrylamide, it was considered that the presence of this substance in food products might pose a risk for human health. Currently, according to EU Commission recommendations, the content of acrylamide in food should be monitored.

OBJECTIVE

The aim of this work was to analyze the food preferences of youth and students from medical schools in Radom, central-eastern Poland, as the most frequent precipitantsas in the field of food products that may be a significant source of acrylamide in the diet. Furthermore, an attempt was made to determine the level of knowledge of the population in the field of acrylamide.

MATERIAL AND METHODS

The research was conducted by questionnaire. The study was based on the answers of 227 respondents. The survey was carried out by direct contact with an interviewer from February - June 2012.

RESULTS

Analysis of the study population shows that women consume more coffee than men. In addition, adults over 25 years old consumed the largest quantity of coffee; it can therefore be assumed that it is a significant source of acrylamide in their bodies. However, even young people under 17 declared that they consume coffee every day (20%).

CONCLUSIONS

Due to the adverse effects of this compound it is important to reduce the level of acrylamide in food products. A few people in the population (7%) had heard of acrylamide previously, but none of them had any knowledge of its occurrence and formation. It is necessary to take strong action to change attitudes towards acrylamide and attempt to introduce ways to reduce this compound in the diet, for example, by appropriate selection of products in the daily diet and appropriate means of thermal preparation of products at home.

Characterization of the essential oil from cone-berries of Juniperus communis L. (Cupressaceae)

Juniperus communis L. (Cupressaceae) is a plant widely cultivated in the Northern hemisphere. Juniper berries, the fruit of Juniperus communis L. are a highly valued, essential oil-rich plant material used traditionally in folk medicine as antiseptic, diuretic, antirheumatic, anti-inflammatory, antibacterial and antifungicidal agent. This paper reviews information on extraction methods of the essential oil from the juniper berries, its chemical composition and antimicrobial as well as antioxidant properties.

Plasmon-induced absorption of blind chlorophylls in photosynthetic proteins assembled on silver nanowires

We demonstrate that controlled assembly of eukaryotic photosystem I with its associated light harvesting antenna complex (PSI-LHCI) on plasmonically active silver nanowires (AgNWs) substantially improves the optical functionality of such a novel biohybrid nanostructure. By comparing fluorescence intensities measured for PSI-LHCI complex randomly oriented on AgNWs and the results obtained for the PSI-LHCI/cytochrome c₅₅₃ (cyt c₅₅₃) bioconjugate with AgNWs we conclude that the specific binding of photosynthetic complexes with defined uniform orientation yields selective excitation of a pool of chlorophyll (Chl) molecules that are otherwise almost non-absorbing. This is remarkable, as this study shows for the first time that plasmonic excitations in metallic nanostructures can not only be used to enhance native absorption of photosynthetic pigments, but also - by employing cyt c₅₅₃ as the conjugation cofactor - to activate the specific Chl pools as the absorbing sites only when the uniform and well-defined orientation of PSI-LHCI with respect to plasmonic nanostructures is achieved. As absorption of PSI alone is comparatively low, our approach lends itself as an innovative approach to outperform the reported-to-date biohybrid devices with respect to solar energy conversion.

Temperature-induced reversible structural phase transition and X-ray diffuse scattering in 2-amino-3-nitropyridinium hydrogen sulfate

The novel polar material 2-amino-3-nitropyridinium hydrogen sulfate, C5H6N3O2(HSO4) (abbreviated as 2A3NP-HS), was obtained and structurally characterized by means of single-crystal X-ray diffraction. At room temperature, 2A3NP-HS crystallizes as a non-centrosymmetric disordered phase (I) in the orthorhombicPna21space group. On cooling below 298 K, 2A3NP-HS undergoes a reversible phase transition to phase (II) with the monoclinic non-centrosymmetricP21space group. This transition might be classified as an `order–disorder' type. The structural details in both phases are analysed. Additionally, for phase (I), in the 304–365 K temperature range, diffuse scattering was found to be present in the form of elongated streaks parallel to thea* direction. This can be unravelled when implementing a short-range order affecting anionic cationic ribbons occurring in the structure, with correlations acting both in thea-direction and in thebc-plane. The results of Monte Carlo simulations, adapting a two-dimensional Ising-type model, reveal the formation of domains, which areb-elongated and thin alonga. Locally, the stacking of the ribbons in the domains reflects the ordered arrangement observed in the low-temperature monoclinic phase (II).

ASSESSMENT OF A STABLE COSMETIC PREPARATION BASED ON ENZYMATIC INTERESTERIFIED FAT, PROPOSED IN THE PREVENTION OF ATOPIC DERMATITIS

Atopic dermatitis is one of the most common skin disorders seen in infants, children and adults. Proper prevention might slow the atopic symptoms. The purpose of the work was a sensory analysis, an evaluation of moistening properties and stability of emulsions based on an enzymatic interesterified fat blend (mutton tallow and walnut oil) and homogenized at different revolutions and different contents of thickener. The emulsions were evaluated with respect to sensory and skin moisturizing properties by 78 respondents. Stability tests, particle size, distribution, dispersity index, morphology structure of the emulsions were determinated too. Taking into consideration all properties of the emulsions, emulsion IV (containing 0.9 g carboxymethyl cellulose and homogenized at 18000 rpm) and emulsion V (1.5 g of carboxymethyl cellulose and homogenized at 24000 rpm) were found to be of optimum composition. The emulsions exhibited good stability, were highly rated in sensory terms and displayed optimum moistening properties. It has been proven that model emulsions based on interesterified fats containing partial acylglicerols, with optimum carboxymethyl cellulose content and specific revolutions at the time of homogenization are an opportunity for developing preparations targeted at skins requiring special care (e.g., with atopic dermatitis or psoriasis). The work proved the use of enzymatic process to create the emulsifier, which represents the innovative contribution of this work. Also it showed an additional application of enzymatic interesterified fats which since has been used only in food industries.

Silver island film substrates for ultrasensitive fluorescence detection of (bio)molecules

A silver island film (SIF) substrate was used to demonstrate that Metal-Enhanced Fluorescence (MEF) is a powerful tool to enable detection of emission from (bio)molecules at very low concentrations. The experiments were carried out with the Fenna-Matthews-Olson (FMO) pigment-protein complex from the photosynthetic green sulfur bacterium Chlorobaculum tepidum. FMO was diluted to a level, at which no emission was detectable on a glass substrate. In contrast, the fluorescence of FMO was readily observed on the SIF substrate, even though the emission wavelength of FMO is displaced by over 300 nm from the maximum of the plasmon resonance of the SIF layer. Estimated enhancements of the fluorescence intensity of FMO on SIF are about 40-fold. The enhancement factor correlates with the improvement of the signal-to-noise ratio for FMO emission on SIF substrates.

Synthesis, photophysical properties and application in organic light emitting devices of rhenium(i) carbonyls incorporating functionalized 2,2′:6′,2′′-terpyridines

Photophysics of [ReCl(CO)₃(4′-R-terpy-κ²N)].

Productivity results and physiological response of the gastrointestinal tract of rabbits fed diets containing rapeseed cake and wheat distillers dried grains with solubles

This study was aimed at determining the possibility of applying rapeseed cake (RC) and wheat distillers dried grains with solubles (DDGS) in diets for HYPLUS meat-type rabbits (n = 64, aged 35–84 days). Control diet (SC) contained 5% of extracted soybean meal. In RC diet, the soybean meal was replaced by RC, in DG diet – by wheat DDGS, whereas in RC–DG diet – by a mixture of RC and wheat DDGS (2.5% each). The study included production analyses, digestibility-balance experiment and physiological assessment of gut response to experimental factors hence data was collected on daily bodyweight gains, feed intake and slaughter performance, nutrients digestibility, nitrogen retention and gut response. The latter included assessment of parameters describing the small intestinal, cecal, and colonic environment of rabbits (e.g. digesta viscosity, ammonia concentration, bacterial enzymes activity, short-chain fatty acid concentration). The highest productivity results were reported for SC group and the lowest ones for DG group. The RC and RC–DG groups were characterised by intermediate productivity. Dressing percentage and contents of carcass elements did not differ among the groups (except for the hind part). Nutrients digestibility and nitrogen retention were the highest in the SC group and the lowest in DG group. The dietary incorporation of DDGS resulted in undesired responses of the gastrointestinal tract including excessively watery digesta in the small intestine, increased concentration of cecal and colonic ammonia, enhanced activity of potentially harmful bacterial β-glucuronidase in cecal digesta, and increased cecal concentration of putrefactive short-chain fatty acids. These negative effects were not due to RC and RC–DG dietary treatments, apart from decreased dry matter concentration in the small intestine in the RC–DG group. In general, the results of our study demonstrated that 5% rape cake can be successfully incorporated into rabbit dietary regimen as a substitute of dietary soybean meal. Considering that the productivity of rabbits fed 2.5% of DDGS (with 2.5% rape cake) and these receiving 5% rape cake was comparable, optional seems also dietary inclusion of up to 2.5% wheat DDGS The higher content of DDGS (5%) in the diet deteriorated most of the growth parameters of rabbits.

Herbal formulations as feed additives in the course of rabbit subclinical coccidiosis

Two simultaneous experiments were carried out in a breeding farm of New Zealand White rabbits (Oryctolagus cuniculus f. domesticus) to determine the feasibility of replacing coccidiostats with garlic and oregano preparation. The research took place during June and July, the period of the greatest threat of coccidiosis caused by Eimeria spp. (Apicomplexa: Eimeriidae). In one investigation, 40 rabbits aged 1-3 months were divided into four groups of ten animals: Group A being a control which received no coccidiostats in feed, Group B receiving the coccidiostat Baycox in water once at weaning, Group C receiving the coccidiostat robenidine in feed, and group D receiving herbal extracts in feed. In the second trial, six mated females were allocated equally to three groups analogous to A, C, and D above during pregnancy and lactation. Bulk stool samples were collected from each group of rabbits at weekly intervals for coproscopic analysis, and the production results of the animals were recorded. In the young rabbits, both the faecal coccidia oocyst counts and body weight gains were more favourable in group D than the remaining groups. Also, the female rabbits of group D were the least infected. The results demonstrate that garlic and oregano feed additives exert a positive influence on the level and course of coccidia infection, with regard to maintaining a good level of animal productivity, and these herbal extracts appear to have potential value in coccidiosis prophylaxy.

Spectroscopic studies of plasmon coupling between photosynthetic complexes and metallic quantum dots

Metallic quantum dots, or nanoparticles, have found an increasing number of applications not only in nanotechnology and nanoscience, but also in neighboring disciplines, such as chemistry and biology. Among the variety of ways to exploit the unique properties of metallic nanostructures is the notion that plasmonic effects associated with the movement of free carriers in metallic nanoparticles may enhance photosynthetic function in naturally evolved organisms. We report on optical microscopy and spectroscopy studies of three hybrid nanostructures composed of spherical gold nanoparticles and peridinin-chlorophyll-protein (PCP), a light-harvesting complex from algae. In the case of a bioconjugated structure we find efficient, concentration dependent quenching due to non-radiative energy transfer. In contrast, for the PCP complexes deposited directly on Au nanoparticles, the emission is increased as a result of the strong increase of the fluorescence quantum yield. Finally, for a structure with controlled separation between metallic nanoparticles and the light-harvesting complexes the emission features non-monotonic behavior with maximum enhancement of about 6, which is due to a combination of fluorescence and absorption rate increases. In this way we demonstrate how the design of plasmonic hybrid nanostructures determines the optical response, which is important for engineering novel systems for photovoltaics and sensor applications, for instance.

Modulation of PC1/3 activity by self-interaction and substrate binding

Prohormone convertase (PC)1/3 is a eukaryotic serine protease in the subtilase family that participates in the proteolytic maturation of prohormone and neuropeptide precursors such as proinsulin and proopiomelanocortin. Despite the important role of this enzyme in peptide synthesis, how PC1/3 activity is regulated is still poorly understood. Using ion exchange chromatography and two-dimensional gel electrophoresis we found that natural PC1/3 present in AtT-20 cells and bovine chromaffin granules, as well as recombinant PC1/3 secreted from overexpressing Chinese hamster ovary cells, exists as multiple ionic forms. Gel filtration and cross-linking studies revealed that protein oligomerization and aggregation contribute greatly to variability in surface charge. The most acidic forms of PC1/3 contained both inactive aggregates as well as oligomerized 87-kDa PC1/3 that exhibited stable activity which was partially latent and could be revealed by dilution. No such latency was observed for the more basic, 66/74-kDa forms of PC1/3. Fractions containing these species were stabilized by preincubation with micromolar concentrations of either fluorogenic substrate or peptides containing pairs of basic residues. In addition, the most active form of 87-kDa PC1/3, a probable homodimer, was activated by preincubation with these same peptides. Cleavage by PC1/3 is often the initiating step in the biosynthetic pathway for peptide hormones, implying that this is a natural step for regulation. Our data suggest that enzyme oligomerization and peptide stabilization represent important contributing factors for the control of PC1/3 activity within secretory granules.

Nutrient digestibility in Arctic fox (Vulpes lagopus) fed diets containing animal meals

Three digestibility experiments on Arctic foxes were carried out. Control groups were fed standard diets (C1 and C2) composed of fresh or frozen animal by-products and steamed ground grain. Dry experimental diets (E1 and E2) contained animal meals, extracted meals and fat, were mixed with water prior to administration. In a preliminary experiment, the digestibility of dry diet E1 moistened with water for 15min and 24h was compared to determine the optimum moistening time during the experimental period proper. The preliminary experiment showed that moistening time had no significant effect on digestibility. In the main experiment, two independent digestibility trials were performed to compare the digestibility of diets fed to foxes during growth (C1 vs. E1) and fur development (C2 vs. E2). Better nutrient digestibility was noted for control diets, compared to experimental. The greatest differences were reported for total protein digestibility. Protein contained in meals undergoes denaturation during heat treatment, which reduces digestibility. It was found that the retention of nitrogen in relation to nitrogen digestion was higher in foxes fed experimental diets (E1 and E2).

[Dynamics of endoparasite infections in rabbits at different rearing regimes]

This study was intended to evaluate the occurrence and seasonality of infection of coccidian and helminth parasites, in three rabbit warrens differently managed. Mothers stayed with their offspring on deep litter (farm A, 90 dams), in boxes cleaned weekly (farm B, 30 dams) or on slatted floor (farm C, 10 females), whereas all the young after weaning (1 to 5 months of age) were kept in cages with slatted floor. Animals were fed a complete balanced pelleted feed (warrens A and B) or traditional forage (herd C). Antiparasitic treatment involved coccidiostatic drugs. Robenidine (alternately with Lerbec in farm A) was added to food in the first two farms, whilst Sulfatyf mixed with water was given once after weaning in farm C. A total of 203 individual faecal samples from females of breeding stock, and 133 pooled samples from young animals, were collected on an annual cycle during 2007-2008 (February-January), and analyzed according to a modified concentration McMaster method. Coccidians were identified based on sporulated oocysts. A number of coccidian species (Eimeria perforans, E. media, E. magna, E. irresidua, E. exiqua, E. coecicola, and E. piriformis) were observed in all farms. The most pathogenic species--E. intestinalis was found both in farm A and B, whereas E. flavescens and E. stiedae--only in the former. The level of infection was high, especially in young rabbits, with the prevalence of 94.9 to 100% and mean intensity from 11,161 to 28,871 oocysts per 1 g of faeces (OPG) in a particular warren. The highest intensity of infection was observed in May, when the mean output increased to 29,454, 56,952, and 23,815 OPG in warrens A, B, and C, respectively. A nematode, Passalurus ambiguus, was detected in all searched farms, with the prevalence from 14.1% to 27.5%, depending on a farm. The species was more often seen in the first part of year. The other helminths (Trichostrongylus retortaeformis, Graphidium strigosum, and Trichuris leporis) were found only in rabbits of warren C. In this warren, the forage of farm origin was suggested to be prepared in a proper way in order to protect it from nematode transmission. The presence of coccidia and their specific composition has been continuously monitored in all farms, to estimate the efficiency of prophylactic measures undertaken.

Synthetic small-molecule prohormone convertase 2 inhibitors

The proprotein convertases are believed to be responsible for the proteolytic maturation of a large number of peptide hormone precursors. Although potent furin inhibitors have been identified, thus far, no small-molecule prohormone convertase 1/3 or prohormone convertase 2 (PC2) inhibitors have been described. After screening 38 small-molecule positional scanning libraries against recombinant mouse PC2, two promising chemical scaffolds were identified: bicyclic guanidines, and pyrrolidine bis-piperazines. A set of individual compounds was designed from each library and tested against PC2. Pyrrolidine bis-piperazines were irreversible, time-dependent inhibitors of PC2, exhibiting noncompetitive inhibition kinetics; the most potent inhibitor exhibited a K(i) value for PC2 of 0.54 microM. In contrast, the most potent bicyclic guanidine inhibitor exhibited a K(i) value of 3.3 microM. Cross-reactivity with other convertases was limited: pyrrolidine bis-piperazines exhibited K(i) values greater than 25 microM for PC1/3 or furin, whereas the K(i) values of bicyclic guanidines for these other convertases were more than 15 microM. We conclude that pyrrolidine bis-piperazines and bicyclic guanidines represent promising initial leads for the optimization of therapeutically active PC2 inhibitors. PC2-specific inhibitors may be useful in the pharmacological blockade of PC2-dependent cleavage events, such as glucagon production in the pancreas and ectopic peptide production in small-cell carcinoma, and to study PC2-dependent proteolytic events, such as opioid peptide production.