Anion-templated synthesis of a switchable fluorescent [2]catenane with sulfate sensing capability.

Anion templation strategies have facilitated the synthesis of various catenane and rotaxane hosts capable of strong and selective binding of anions in competitive solvents. However, this approach has primarily relied on positively charged precursors, limiting the structural diversity and the range of potential applications of the anion-templated mechanically interlocked molecules. Here we demonstrate the synthesis of a rare electroneutral [2]catenane using a powerful, doubly charged sulfate template and a complementary diamidocarbazole-based hydrogen bonding precursor. Owing to the unique three-dimensional hydrogen bonding cavity and the embedded carbazole fluorophores, the resulting catenane receptor functions as a sensitive fluorescent turn-ON sensor for the highly hydrophilic sulfate, even in the presence of a large excess of water. Importantly, the [2]catenane exhibits enhanced binding affinity and selectivity for sulfate over its parent macrocycle and other acyclic diamidocarbazole-based receptors. We demonstrate also, for the first time, that the co-conformation of the catenane may be controlled by reversible acid/base induced protonation and deprotonation of the anionic template, SO42-. This approach pioneers a new strategy to induce molecular motion of interlocked components using switchable anionic templates.

Fullerene-Functionalized Halogen-Bonding Heteroditopic Hosts for Ion-Pair Recognition.

Despite their hydrophobic surfaces with localized π-holes and rigid well-defined architectures providing a scaffold for preorganizing binding motifs, fullerenes remain unexplored as potential supramolecular host platforms for the recognition of anions. Herein, we present the first example of the rational design, synthesis, and unique recognition properties of novel fullerene-functionalized halogen-bonding (XB) heteroditopic ion-pair receptors containing cation and anion binding domains spatially separated by C60. Fullerene spatial separation of the XB donors and the crown ether complexed potassium cation resulted in a rare example of an artificial receptor containing two anion binding sites with opposing preferences for hard and soft halides. Importantly, the incorporation of the C60 motif into the heteroditopic receptor structure has a significant effect on the halide binding selectivity, which is further amplified upon K+ cation binding. The potassium cation complexed fullerene-based receptors exhibit enhanced selectivity for the soft polarizable iodide ion which is assisted by the C60 scaffold preorganizing the potent XB-based binding domains, anion-π interactions, and the exceptional polarizability of the fullerene moiety, as evidenced from DFT calculations. These observations serve to highlight the unique properties of fullerene surfaces for proximal charged guest binding with potential applications in construction of selective molecular sensors and modulating the properties of solar cell devices.

Engineered Binding Microenvironments in Halogen Bonding Polymers for Enhanced Anion Sensing.

Mimicking Nature's polymeric protein architectures by designing hosts with binding cavities screened from bulk solvent is a promising approach to achieving anion recognition in competitive media. Accomplishing this, however, can be synthetically demanding. Herein we present a synthetically tractable approach, by directly incorporating potent supramolecular anion-receptive motifs into a polymeric scaffold, tuneable through a judicious selection of the co-monomer. A comprehensive analysis of anion recognition and sensing is demonstrated with redox-active, halogen bonding polymeric hosts. Notably, the polymeric hosts consistently outperform their monomeric analogues, with especially large halide binding enhancements of ca. 50-fold observed in aqueous-organic solvent mixtures. These binding enhancements are rationalised by the generation and presentation of low dielectric constant binding microenvironments from which there is appreciable solvent exclusion.

pH-Dependent transport of amino acids across lipid bilayers by simple monotopic anion carriers.

The transport of amino acids across lipid membranes is vital for the proper functioning of every living cell. In spite of that, examples of synthetic transporters that can facilitate amino acid transport are rare. This is mainly because at physiological conditions amino acids predominantly exist as highly polar zwitterions and proper shielding of their charged termini, which is necessary for fast diffusion across lipophilic membranes, requires complex and synthetically challenging heteroditopic receptors. Here we report the first simple monotopic anion receptor, dithioamide 1, that efficiently transports a variety of natural amino acids across lipid bilayers at physiological pH. Mechanistic studies revealed that the receptor rapidly transports deprotonated amino acids, even though at pH 7.4 these forms account for less than 3% of the total amino acid concentration. We also describe a new fluorescent assay for the selective measurement of the transport of deprotonated amino acids into liposomes. The new assay allowed us to study the pH-dependence of amino acid transport and elucidate the mechanism of transport by 1, as well as to explain its exceptionally high activity. With the newly developed assay we screened also four other representative examples of monotopic anion transporters, of which two showed promising activity. Our results imply that heteroditopic receptors are not necessary for achieving high amino acid transport activities and that many of the previously reported anionophores might be active amino acid transporters. Based on these findings, we propose a new strategy for the development of artificial amino acid transporters with improved properties.

Ions in an AC Electric Field: Strong Long-Range Repulsion between Oppositely Charged Surfaces.

Two oppositely charged surfaces separated by a dielectric medium attract each other. In contrast we observe a strong repulsion between two plates of a capacitor that is filled with an aqueous electrolyte upon application of an alternating potential difference between the plates. This long-range force increases with the ratio of diffusion coefficients of the ions in the medium and reaches a steady state after a few minutes, which is much larger than the millisecond timescale of diffusion across the narrow gap. The repulsive force, an order of magnitude stronger than the electrostatic attraction observed in the same setup in air, results from the increase in osmotic pressure as a consequence of the field-induced excess of cations and anions due to lateral transport from adjacent reservoirs.

Oxyanion transport across lipid bilayers: direct measurements in large and giant unilamellar vesicles.

A simple di(thioamido)carbazole 1 serves as a potent multispecific transporter for various biologically relevant oxyanions, such as drugs, metabolites and model organic phosphate. The transport kinetics of a wide range of oxyanions can be easily quantified by a modified lucigenin assay in both large and giant unilamellar vesicles.

1,8-Diamidocarbazoles: an easily tuneable family of fluorescent anion sensors and transporters.

The synthesis, structure and anion recognition properties of an extensive, rationally designed series of bisamide derivatives of 1,8-diaminocarbazole and 1,8-diamino-3,6-dichlorocarbazole are described. Despite simple structures and the presence of only three hydrogen bond donors, such compounds are remarkably strong and selective receptors for oxyanions in DMSO + 0.5%H2O. Owing to their carbazole fluorophore, they are also sensitive turn-on fluorescent sensors for H2PO4- and AcO-, with a more than 15-fold increase in fluorescence intensity upon binding. Despite relatively weak chloride affinity, some of the diamidocarbazoles have also been shown, for the first time, to be very active chloride transporters through lipid bilayers. The binding, sensing and transport properties of these receptors can be easily modulated by the usually overlooked variations in the length and degree of branching of their alkyl side arms. Overall, this study demonstrates that the 1,8-diamidocarbazole binding unit is a very promising and synthetically versatile platform for the development of fluorescent sensors and transporters for anions.

Selective turn-on fluorescence sensing of sulfate in aqueous-organic mixtures by an uncharged bis(diamidocarbazole) receptor.

A linear, uncharged, hydrogen bonding receptor A with two carbazole-based binding domains was synthesised and evaluated for its anion binding properties in DMSO/H2O mixtures. 1H NMR titrations revealed that, in DMSO/H2O 0.5%, A forms both 1 : 1 and 1 : 2 complexes with SO42-, H2PO4-, PhCOO- and Cl-. In 1 : 1 complexes the receptor encloses the tetrahedral anions tightly, forming a helical structure, while Cl- binds with a single carbazole unit only. In the presence of 10% of water the 1 : 2 complexes with SO42- and PhCOO- disappear, and the respective 1 : 1 binding constants decrease sufficiently to be quantified by UV-Vis titration. In this highly competitive medium, A binds sulfate with K1:1 = 105.47 M-1, i.e., it binds approx. 30, 360 and >1000 times more strongly than H2PO4-, PhCOO- and Cl-, respectively. Furthermore, the association with sulfate is over 50 times stronger than that for a model diamidocarbazole 1 under identical conditions, suggesting a very strong chelating effect due to the diglycoyl linker. Increasing the amount of water to 25% (the solubility limit of A) lowers the 1 : 1 binding constant with SO42- to 103.73 M-1. Receptor A was shown to act as a selective turn-on fluorescent sensor for sulfate, able to sense sulfate in sulfate-rich mineral water.

Sulfate templated assembly of neutral receptors in aqueous DMSO - orthogonal versus biplane structures.

Simple, easily available diamidocarbazoles form robust 2 : 1 complexes with SO4(2-) even in the presence of a large excess of water. An appropriate choice of side arms directs the assembly towards the formation of either an orthogonal or a biplane structure, both in solution and in the solid state.

Postural habits of young adults and possibilities of modification.

BACKGROUND: The aim of the study was to assess postural habits in young, healthy people, identify correlations between postural errors and pain and attempt to modify bad habits. MATERIAL AND METHODS: 144 people, aged 18-23 were enrolled. The intervention consisted of 4 stages: Stage 1 - identification of postural habits, description of responses to stress, back pain frequency and intensity (Jackson & Moskowitz); Stage 2 - correction of habitual position with the help of a physiotherapist, briefing about ergonomic everyday behaviours and consequences of continued non-ergonomic behaviours, Stage 3 - follow-up examination: self-assessment of changes, evaluation of the effects of modifications, determination of causes for discontinuing the behaviour modification programme, where applicable; and Stage 4 - final examination, assessment of results. Correlations were sought between inappropriate postural behaviour in various positions and between non-ergonomic postural behaviour and pain location and response to stress. Statistical analysis was carried out with Excel and Statistica v. 7.1. A non-parametric χ(2) test was used at p<0.005. RESULTS: All participants presented poor postural patterns in the standing, sitting and recumbent position. Back pain was reported by half of the participants. Statistically significant relationships between pain and habitual positions were noted with regard to the cervical and lumbar spine and also for abdominal pain as a response to stress in people with excessive thoracic kyphosis. Behaviour modifications caused or intensified lumbar pain or thigh muscle pain. Positive outcomes included better urination and/or defecation and greater comfort in assuming the different positions and performing activities of daily living in these positions. Some examinees discontinued behaviour modification during the first month after the initial instruction and the majority did so over the next three months. CONCLUSIONS: 1. Non-ergonomic postural behaviours are common among young people. 2. Changing the body position does not eliminate the impact of the inappropriate habit. 3. An attempt to modify non-ergonomic postural behaviours usually results in pain, which may act as a demotivating factor. 4. Discomfort associated with the modification of habitual postural behaviours is reduced after 3-4 months of regular training.

Professional experience and ergonomic aspects of midwives' work.

OBJECTIVES: The most frequent manner of attending childbirth imposes on midwives assuming poor body position affecting the musculoskeletal system. Long professional experience does not mitigate the negative effects. The adopted movement habit, as well as the type, number and frequency of actions influence the body posture. The aim of the study was to identify ergonomic threats of basic occupational midwives activities and how particular spinal segments arrangements while attending childbirth using the same technique in senior midwives differ from those of junior ones. It was also checked whether pain influences the working position assumed by midwives. MATERIALS AND METHODS: Examinations were conducted in 95 midwives aged 21-50 (X = 29.25 ± 9.34): 51 graduates of BSc midwifery who worked 680 h in delivery rooms during obligatory practical classes and apprenticeship and 44 senior midwives with professional experience of 7-27 years (X = 14.84 ± 5.98). The study was threefold. The spinal alignment while performing work activities associated with attending childbirth was assessed using the OWAS system and the SonoSens Monitor, the center of gravity projection on basal plane--using the AccuGait AMTI stabilometric platform. The measurements were taken during a simulation of attending childbirth (on examination model). A survey was conducted aimed at identifying spinal pain. RESULTS: Midwives' working postures require unnatural body alignments. Postural instability in the working position and no maximal usage of basal plane were observed. The work overload may afflict the musculoskeletal system, which was confirmed by different pain discomforts in 67.3% of the examinees. CONCLUSIONS: Spinal alignment while attending childbirth is individually differentiated and in every case non-ergonomic. Identifying explicitly spinal overloads is difficult, but the most prevalent ones affect lumbar and cervical regions altogether. Spinal pain is frequently noted, both in junior and senior midwives, and is characteristic for midwives working in maximal movement ranges.

[Evaluations of ophthalmological care expectation in the opinion of countryside dwellers in the example of the Wola Uhruska region]. / Ocena potrzeb zdrowotnych w zakresie narzadu wzroku i ich realizacji w opinii mieszkanców terenów wiejskich na przykladzie gminy Wola Uhruska.

PURPOSE: The aim of the study was the evaluations of ophthalmological care expectation in opinion of countryside inhabitants and their knowledge of eye diseases. MATERIALS AND METHODS: The analysis was performed based on the results of a survey, which covered 198 rural inhabitants living in Wola Uhruska region. The study was carried out during training arranged by Medical University of Lublin in July 2002. RESULTS: The obtained material was analysed and presented in the form of diagrams and written report. The results of the study showed, that 77% of patients was dissatisfied with the ophthalmologic health care access, despite, that the nearest ophthalmologic practice was in the distance of 30 km. Unfortunately, only 25% of persons could indicate the cause of their eye problems. It is important, to provide more information of eye condition for all patients.