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The effects of an eight-year natural aging of ASC impregnated activated carbon on the adsorption capacity and breakthrough times of model organic vapors and of the nerve agent sarin were investigated. Aging delayed methanol breakthrough from dry air on pre-dried carbon, but shortened the breakthrough time of both methanol and hexane under relative humidity (RH) of 30-85% on pre-humidified carbon. Aging also shortened the breakthrough time of the less volatile model compound 2-methoxyethanol, especially under RH of 60-85%. Aging significantly reduced the protection capacity against sarin at RH of 85%. The effects of aging on physisorption are attributed to enhanced hydrogen-bonding capability and strength of the interaction between water and adsorption sites on the carbon surface.

Mild treatment with hydrogen peroxide solutions (3-30%) efficiently decomposes adsorbed chemical warfare agents (CWAs) on microporous activated carbons used in protective garments and air filters. Better than 95% decomposition of adsorbed sulfur mustard (HD), sarin, and VX was achieved at ambient temperatures within 1-24 h, depending on the H2O2 concentration. HD was oxidized to the nontoxic HD-sulfoxide. The nerve agents were perhydrolyzed to the respective nontoxic methylphosphonic acids. The relative rapidity of the oxidation and perhydrolysis under these conditions is attributed to the microenvironment of the micropores. Apparently, the reactions are favored due to basic sites on the carbon surface. Our findings suggest a potential environmentally friendly route for decontamination of adsorbed CWAs, using H2O2 without the need of cosolvents or activators.

An upgraded microcalorimeter comprising a MEMS-based thermal conductivity vacuum gauge with a ∼1.3 mV/K thermopile sensor and a thin Si 3 N x film heater was constructed. The improved features relative to a previous design are linear rise of the temperature with time and rapid heating of up to ∼500 °C/s. The device was used for thermal analysis of micrometer-size particles of the explosives TNT, RDX and PETN by measuring temperature changes while heating the film heater. The TNT thermogram features a single exotherm that is well separated from the endotherm. The area and position of the melting and decomposition peaks in the RDX thermogram are proportional to the particle mass. The observed heats of melting agree with known thermodynamic data. The observed heat of deflagration is less than 1% of the calculated value, because a large fraction of the heated sample was sputtered from the heater and most of the heat was lost to the surrounding. Monitoring the air temperature above the heater with an ultrathin thermocouple yielded identifiable thermograms in accord with the surface thermograms. Such contactless sensing above the heater can detect the decomposition of micrometer-size particles and offers potential for the development of an inexpensive, simple to use field explosive detector.

Hydrothermal treatment of activated carbon contaminated with adsorbed HD, VX, or sarin at temperatures of 90–120 °C decomposes >95% of the adsorbed chemical warfare agents within a period of 0.5–4 h, in an environmentally friendly route that is free of corrosive chemicals and ends in nontoxic products.

Thermal and hydrothermal degradations of adsorbed sulfur mustard (HD) on activated carbon particles from a chemical protective over-garment were studied. Carbon loaded with 5 wt.% HD was heated in a closed reactor at temperatures up to 160 °C for 0.5–6 h and analyzed by solid-state 13 C MAS NMR. On dry carbon at room temperature, HD was stable for months. On a thoroughly pre-wetted carbon, adsorbed HD partially degraded to thiodiglycol (TDG) and TDG-sulfoxide (TDG-SO) within 2–3 months. Heating dry HD-loaded carbon to 160 °C caused partial degradation within 4 h to 1,4-thioxane, along with 1,4-dithiane and vinyl sulfides. Complete degradation within 2.5 h to the same products occurred upon hydrothermal treatment of the HD-loaded carbon, using a water/carbon ratio of 0.3:1. With higher water/carbon ratios of 0.6:1–5:1 at temperatures of 120 °C and above, adsorbed HD hydrolyzed rapidly within 0.5 h. The latter reaction led to the formation of TDG concurrent with either thioxane (at 160 °C) or TDG-SO and TDG-dimer (at 120 °C). The mechanisms of the observed degradation processes are discussed.

Cardiotoxicity associated with doxorubicin (DOX) treatment limits the therapeutic efficiency of this drug against cancer. 2-Chloro-N(6)-(3-iodobenzyl)adenosine-5'-N-methyluronamide (Cl-IB-MECA), a selective agonist of A(3) adenosine receptor (A(3)R), reduces DOX toxicity in newborn rat cultured cardiomyocytes. The study's aim was to determine whether the protection demonstrated by Cl-IB-MECA attenuates cardiac depression in vivo. In addition, we wished to examine whether this protective pathway affects the sarcoplasmic reticulum (SR) calcium uptake and release, as well as intramitochondrial Ca(2+) accumulation induced by DOX. Rats were injected every alternate day (6 times) with (1) saline, (2) 2.5mg/kg i.p. DOX, (3) 33 microg/kg i.v. Cl-IB-MECA, (4) DOX+Cl-IB-MECA. Left ventricular functions were assessed by invasive (pressure) and non-invasive (echocardiography) techniques at the end of the injection period and 4 weeks later. Cytosolic and intramitochondrial calcium levels were measured with indo-1 and rhod-2 probes. SR Ca(2+) content was determined by exposing cultured rat cardiomyocytes to caffeine. Echocardiography data demonstrate left ventricular wall thinning (23%), an increase in the end systolic dimension (170%) and decreased fractional shortening (35+/-5% vs. 54+/-5%, p

The involvement of nitric oxide (NO) in the late phase of ischemic preconditioning is well established. However, the role of NO as a trigger or mediator of “classic preconditioning” remains to be determined. The present study was designed to investigate the effects of NO on calcium homeostasis in cultured newborn rat cardiomyocytes in normoxia and hypoxia. We found that treatment with the NO donor, sodium nitroprusside (SNP) induced a sustained elevation of intracellular calcium level ([Ca 2+ ] i ) followed by a decrease to control levels. Elevation of extracellular calcium, which generally occurs during ischemia, caused an immediate increase in [Ca 2+ ] i and arrhythmia in cultures of newborn cardiomyocytes. Treatment with SNP decreased [Ca 2+ ] i to control levels and re-established synchronized beating of cardiomyocytes. A decrease in extracellular [Na + ], which inhibits the Na + /Ca 2+ exchanger, did not prevent [Ca 2+ ] i reduction by SNP. In contrast, application of thapsigargin, an inhibitor of sarcoplasmic reticulum Ca 2+ -ATPase (SERCA2a), increased [Ca 2+ ] i , and in its presence, SNP did not reduce [Ca 2+ ] i , indicating that Ca 2+ reduction is achieved via activation of SERCA2a. The results obtained suggest that activation of SERCA2a by SNP increases Ca 2+ uptake into the sarcoplasmic reticulum (SR) and prevents cytosolic Ca 2+ overload, which might explain the protective effect of SNP from hypoxic damage.

The fate of the OP nerve agent isopropyl methylphosphonofluoridate (sarin) on granular activated and metal-impregnated activated carbons that are used in gas-mask filters was investigated by means of 31 P magic-angle-spinning (MAS) NMR spectroscopy. The results show that most of the adsorbed sarin on extensively dried carbons decomposes with a half-life of 5-12 days. A MAS-NMR signal of the degradation product isopropyl methylphosphonic acid (IMPA) appears in the spectra of sarin on non-impregnated carbons. The IMPA signal is not visible in the spectra from metal-impregnated carbons, probably due to strong binding of the acid molecule to paramagnetic Cr 3+ and Cu 2+ ions. Exposure of BPL and ASC carbons to air of 53% relative humidity shortens the degradation time by approximately an order of magnitude. Wetting shortens the half-life of sarin on BPL carbon to approximately 2 hours.

The effects of high relative humidity (RH) on the breakthrough of the nerve agent simulant dimethyl methylphosphonate (DMMP) vapor in beds of ASC-impregnated, activated carbon were investigated. Maximum concentrations of DMMP at room temperature and RH > 60% were found to be lower by more than an order of magnitude than in dry air. The breakthrough time (tB) of 1.2 × 10−4 g l−1 DMMP in pre-humidified beds and humid air of RH = 90% was shortened by a factor of 1.6 relative to adsorption in dry beds and dry air. Analysis of the breakthrough curves according to the Wheeler–Jonas model indicated that the high RH lowered the dynamic adsorption capacity (WE) but had nearly no effect on the critical bed weight (WC). The reduction of WE by humidity correlates with the observed displacement of adsorbed water by DMMP. The use of DMMP for testing filter performance is limited to low and intermediate relative humidities. On the other hand, DMMP in dry air can be used to advantage for testing the capacity of new or used respirator filters and for the detection of filter channeling.

Low energy visible light (LEVL) irradiation has been shown to exert some beneficial effects on various cell cultures. For example, it increases the fertilizing capability of sperm cells, promotes cell proliferation, induces sprouting of neurons, and more. To learn about the mechanism of photobiostimulation, we studied the relationship between increased intracellular calcium ([Ca2+] i) and reactive oxygen species production following LEVL illumination of cardiomyocytes. We found that visible light causes the production of O 2 · ¯ and H2O2 and that exogenously added H2O2 (12 μm) can mimic the effect of LEVL (3.6 J/cm2) to induce a slow and transient increase in [Ca2+] i. This [Ca2+] i elevation can be reduced by verapamil, a voltage-dependent calcium channel inhibitor. The kinetics of [Ca2+] i elevation and morphologic damage following light or addition of H2O2 were found to be dosedependent. For example, LEVL, 3.6 J/cm2, which induced a transient increase in [Ca2+] i , did not cause any cell damage, whereas visible light at 12 J/cm2 induced a linear increase in [Ca2+] i and damaged the cells. The linear increase in [Ca2+] i resulting from high energy doses of light could be attenuated into a non-linear small rise in [Ca2+] i by the presence of extracellular catalase during illumination. We suggest that the different kinetics of [Ca2+] i elevation following various light irradiation or H2O2 treatment represents correspondingly different adaptation levels to oxidative stress. The adaptive response of the cells to LEVL represented by the transient increase in [Ca2+] i can explain LEVL beneficial effects.

The Wheeler–Jonas (WJ) model for prediction of the protection capacity of organic vapor filters under a fixed airflow was extended to breathing-simulation, pulsating flow. Breakthrough curves of dimethyl-methyl phosphonate (DMMP) and decane were measured under fixed flow and sinusoidal flow. A linear dependence of ln( C X / C 0 ) on the breakthrough time ( t B ) was observed in all the experiments, indicating that the concepts of critical bed weight ( W C ) and dynamic adsorption capacity ( W E ) as defined by the WJ model are applicable to pulsating flow as well. W E was found to be almost unchanged by the flow pattern, whereas W C was considerably larger (by 7–44%) at pulsating flow compared to fixed flow with the same average rate. Thus, shifting from fixed flow to pulsating flow may shorten t B significantly. The effect of the flow type on t B increases with the ratio of the critical weight to the total bed weight. For a high protection level ( C 0 / C X =60 000), the protection capacity of personal NBC canisters was reduced by up to 15% upon shifting from fixed to pulsating flow.

The ability of cells to coordinately migrate in groups is crucial to enable them to travel long distances during embryonic development, wound healing and tumorigenesis, but the fundamental mechanisms underlying intercellular coordination during collective cell migration remain elusive despite considerable research efforts. A novel analytical framework is introduced here to explicitly detect and quantify cell clusters that move coordinately in a monolayer. The analysis combines and associates vast amount of spatiotemporal data across multiple experiments into transparent quantitative measures to report the emergence of new modes of organized behavior during collective migration of tumor and epithelial cells in wound healing assays. First, we discovered the emergence of a wave of coordinated migration propagating backward from the wound front, which reflects formation of clusters of coordinately migrating cells that are generated further away from the wound edge and disintegrate close to the advancing front. This wave emerges in both normal and tumor cells, and is amplified by Met activation with hepatocyte growth factor/scatter factor. Second, Met activation was found to induce coinciding waves of cellular acceleration and stretching, which in turn trigger the emergence of a backward propagating wave of directional migration with about an hour phase lag. Assessments of the relations between the waves revealed that amplified coordinated migration is associated with the emergence of directional migration. Taken together, our data and simplified modeling-based assessments suggest that increased velocity leads to enhanced coordination: higher motility arises due to acceleration and stretching that seems to increase directionality by temporarily diminishing the velocity components orthogonal to the direction defined by the monolayer geometry. Spatial and temporal accumulation of directionality thus defines coordination. The findings offer new insight and suggest a basic cellular mechanism for long-term cell guidance and intercellular communication during collective cell migration., Author Summary The fundamental mechanisms underlying intercellular coordination during collective cell migration remain elusive despite considerable research efforts. We present a novel analytical framework that considers spatiotemporal dynamics across several traits. Our approach was applied to discover new modes of organized collective dynamics of cancer and normal cells. Following disruption of a cell monolayer, a propagating wave of coordinated migration emerges as clusters of coordinately moving cells are formed away from the wound and disintegrate near the advancing front. Activation of Met signal transduction by hepatocyte growth factor/scatter factor, master regulators of cell motility in malignant and normal processes, generates coinciding waves of cellular acceleration and stretching that propagate backward from the wound front and trigger a delayed wave of directional migration. Amplified coordination is intrinsically associated with enhanced directionality suggesting that even a weak directional cue is sufficient to promote a coordinated response that is transmitted to cells within the cell sheet. Our findings provide important novel insights on the basic cellular organization during collective cell migration and establish a mechanism of long-range cell guidance, intercellular coordination and pattern formation during monolayer wound healing.

Breakthrough times ( t B ) of activated carbon, at constant rate and pulsating (breathing-simulation) flow challenge of dimethyl methyl phosphonate (DMMP), an accepted simulant for organophosphorus warfare agents, were obtained. For personal filter canisters, t B at pulsating flow rates of 30 or 45 l min −1 on the average were found to be shorter than t B obtained at fixed flow rates by 4 and 6%, respectively. The shortening of t B by pulsating flow patterns relative to fixed flow is explained in terms of the critical bed weight as used in the Wheeler-Jonas model. The difference in t B between pulsating and fixed flow rate is expected to increase with decreasing bed depths that approach the critical bed depth.

The long-term effects of octreotide, thesynthetic analog of the hormone somatostatin, on acuteexperimental pancreatitis were studied. Acutepancreatitis was induced in rats by intraparenchymalinjections of 0.5 ml 5% or 10% sodium taurocholate.Octreotide (10 mg/kg/day, subcutaneously), or salineinjections as controls, were started four hours later,and their effects were assessed 30, 60, and 90 daysafter the induction of pancreatitis. Neitherintrapancreatic saline injections nor octreotideadministration without the induction of pancreatitiscaused any biochemical or histological abnormalities.Taurocholate-induced pancreatitis was followed by remarkablehyperglycemia, which was ameliorated by octreotide.Thirty days after induction of pancreatitis, glucoselevels were 269 ± 21 mg/100 ml and 153 ±17 mg/100 ml in the control and octreotide treated animals,respectively (P < 0.02). Octreotide administrationwas associated with increased pH values after 60 and 90days (P < 0.05 for the 90 days group). The levels ofhematocrit, calcium, and amylase were already within thenormal ranges after 30 days and were unaffected byoctreotide. There were no signs of chronic exocrineinsufficiency and all the surviving rats gained weight during the follow-up. However, the relativeweights of the pancreases of the octreotide-treatedanimals were higher than those of the controls 30 daysafter IOP. Histopathological evaluation demonstrated regeneration of the pancreatic tissue, andincreased number and hypertrophy of the islets ofLangherhans. There were no significant differenceswhether the octreotide treatment was given for only 48or 96 hr. Survival was significantly improved byoctreotide; only one octreotide-treated rat (2.5%) with10% taurocholate-induced pancreatitis died, while six(15%) of the control animals succumbed (P < 0.05). These studies provided data on the sequelae ofacute pancreatitis and showed that octreotide may havelong-term beneficial effects in this disease.

A graded response to calcium is the defining feature of calcium-regulated exocytosis. That is, there exist calcium concentrations that elicit submaximal exocytotic responses in which only a fraction of the available population of secretory vesicles fuse. The role of calcium-dependent inactivation in defining the calcium sensitivity of sea urchin egg secretory vesicle exocytosis in vitro was examined. The cessation of fusion in the continued presence of calcium was not due to calcium-dependent inactivation. Rather, the calcium sensitivity of individual vesicles within a population of exocytotic vesicles is heterogeneous. Any specific calcium concentration above threshold triggered subpopulations of vesicles to fuse and the size of the subpopulations was dependent upon the magnitude of the calcium stimulus. The existence of multiple, stable subpopulations of vesicles is consistent with a fusion process that requires the action of an even greater number of calcium ions than the numbers suggested by models based on the assumption of a homogeneous vesicle population.

Differences in the calcium sensitivity of individual secretory vesicles can explain a defining feature of calcium-regulated exocytosis, a graded response to calcium. The role of the time dependence of calcium delivery in defining the observed differences in the calcium sensitivity of sea urchin egg secretory vesicles in vitro was examined. The calcium sensitivity of individual secretory vesicles (i.e., the distribution of calcium thresholds) is invariant over a range of calcium delivery rates from faster than micromolar per millisecond to slower than micromolar per second. Any specific calcium concentration above threshold triggers subpopulations of vesicles to fuse, and the size of these subpopulations is independent of the time course required to reach that calcium concentration. All evidence supports the hypothesis that the magnitude of the free calcium is the single controlling variable that determines the fraction of vesicles that fuse, and that this fraction is established before the application of calcium. Submaximal responses to calcium cannot be attributed to alterations in the calcium sensitivity of individual secretory vesicles arising from the temporal properties of the calcium delivery. Models that attempt to explain the cessation of fusion using changes in the distribution of calcium thresholds arising from the rate of calcium delivery and/or adaptation are not applicable to this system, and thus cannot be general.

The absorption and desorption of chlorobenzene, o-dichlorobenzene, and chloroform in poly[n-butyl methacrylate] (PBMA) was studied in polymer-coated 104 MHz surface acoustic wave (SAW) sensors, and in free-standing polymer films by thermogravimetric analysis (TGA). The sorption processes were analyzed by a Fickian simulation and best-fit partition, and diffusion coefficients were derived. Good correlations were found between simulated and observed data. Partition coefficients derived from SAW response were independent of coating thickness and were found to be about two to three times bigger than those derived from the gravimetric response. In contrast, the diffusion coefficients increased linearly with coating thickness in the range 70−560 kHz. For the thickest polymer coating, SAW-derived diffusion coefficients were comparable with TGA-related diffusion coefficients. This study reconfirms the finding for other polymers that the response of SAW chemosensors is higher than that anticipated from a mass chan...

Multiple therapeutic modalities studied for acute pancreatitis often show a poor correlation between results obtained in experimental studies and results of clinical trials. One of the main reasons for this discrepancy is that in most experimental studies the drugs were administered immediately after induction of pancreatitis, whereas in the clinical setting there is almost always a delay between the onset of the disease and initiation of the treatment. We studied the effects of a delayed treatment with octreotide, the synthetic analogue of the hormone somatostatin, on acute experimental pancreatitis in rats. The disease was induced by intraparenchymal injections of 0.5 ml 5% sodium taurocholate, and octreotide (10 mg/kg/day s.c.) was started either 4 or 12 hr later. Subcutaneous saline injections were used in controls. One-half of the animals of each study group was sacrificed after 36 hr, and the following parameters were examined: pancreatic weight, plasma pH, serum calcium and amylase, and histopathological damage. The same parameters, as well as survival, were assessed after 20 days in the remaining rats. Neither intrapancreatic saline injections, nor octreotide administration without the induction of pancreatitis, caused any biochemical or histological alterations. Hypocalcemia and acidosis in pancreatitis-induced rats were improved by octreotide, but, as expected, it had no effect on amylase levels. Octreotide ameliorated pancreatic edema, intestinal dilatation, and the histopathological injury score 36 hr after induction of pancreatitis. Mortality was 40% in control animals, and only 20% in rats treated with octreotide. Overall, octreotide had beneficial effects in acute experimental pancreatitis, and was more effective when started earlier. These results indicate that octreotide may have a role in the management of acute pancreatitis.

Fusion of individual human erythrocytes to fibroblasts expressing the influenza virus hemagglutinin Cells were attached to coverslips fitted in a specially designed flow chamber mounted on a microscope stage, and fusion was triggered by rapid acidification to pH less than 5.2. Fusion between single cell pairs was monitored by a fluorescence increase due to redistribution of fluorescent dyes between either membrane or cytoplasmic compartments of fusing cells. The single cell fusion events were broadly heterogenous in lag times, rise times, and overall shape of the curves. Lag times obtained with a water-soluble dye were within the range obtained with a water-soluble dye were within the range obtained with the membrane-bound fluorophores, (10-160 s). Fusion was both all-or-nothing and irreversible, in that once dye redistribution in any cell commenced, it completed, regardless of pH. Short pulses of pH 4.9 for 6-10 s led to about half of the cell pairs fusing, but pulses greater than 14 s were as effective as constant low pH. Pulses that were too short to trigger fusion did not partially activate nor deactivate the fusion process, as shown by the ability of a second acidification to cause fusion of the same cells, with similar lag times. These results indicate that the overall hemagglutinin-mediated fusion process is composed of at least two stages, one required for commitment of the hemagglutinin to a fusogenic state that is pH-dependent and a maturation stage that is pH-independent.

Employing [ 3 H]Ro5-4864 as a radioligand, the existence of peripheral benzodiazepine binding sites in rat hind limb skeletal fibroblasts was explored. Saturable, high affinity binding of this ligang is described for fibroblasts and cell membrane preparations, demonstrating a pharmacological profile characteristic for such receptors. The binding of [ 3 H]Ro5-4864 exhibited higher affinity and density in fibroblasts compared to membrane preparations. A quarternaryamine derivative of PK 11195 showed a similar potency as a displacer of [ 3 H]Ro5-4864 in both preparations. The data suggest that peripheral benzodiazepine receptors are present in the plasma membrane of primary mammalian fibroblasts.

The fate of the persistent OP nerve agent O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX) on granular activated carbons that are used for gas filtration was studied by means of 31P magic angle spinning (MAS) NMR spectroscopy. VX as vapor or liquid was adsorbed on carbon granules, and MAS NMR spectra were recorded periodically. The results show that at least 90% of the adsorbed VX decomposes within 20 days or less to the nontoxic ethyl methylphosphonic acid (EMPA) and bis(S-2-diisopropylaminoethane) {(DES)2}. Decomposition occurred irrespective of the phase from which VX was loaded, the presence of metal impregnation on the carbon surface, and the water content of the carbon. Theoretical and practical aspects of the degradation are discussed.

Calcium ions have been implicated in the mechanisms of ventricular arrhythmias. Impairment of intercellular coupling by calcium overload is considered to facilitate ventricular fibrillation (VF) and to sup-press its self termination. According to our hypothesis, any compound that decreases intracellular calcium concentration [Ca 2+ ] i during VF can serve as defibrillating drug. In this study, we examined the effect of d-sotalol and tedisamil on calcium overload in cultured, spontaneously beating rat cardiomyocytes. The changes of [Ca 2+ ] i were measured by indo-1 method and the intercellular synchronization by image analysis. The results showed that increase in [Ca 2+ ] o from 1.9 mM to 3.9 mM increased [Ca 2+ ] i from 100 nM to 320 nM and transformed the synchronized cell movement to an asynchronous one. Administration of 5 × 10 −6 M d-sotalol or 10 −6 M tedisamil, decreased the [Ca 2+ ] i to its basic level and restored the synchronized activity. In summary: Our results showed that increase in [Ca 2+ ] i known to caused inhibition of intercellular coupling, that could lead to arrhythmia and fibrillation while d-sotalol or tedisamil prevented this effect. These results support our hypothesis, that class III antiarrhythmic compounds with positive inotropic effect, increase intercellular synchronization, by decreasing free [Ca 2+ ] i , most probably by increasing the Ca 2+ uptake by the sarcoplasmic reticulum, and therefore act as a defibrillating compound.

A comparative study of the spin-lattice relaxation times (T1) of proton-bearing carbons in bilirubin and its derivatives is reported. The NT1 values of the backbone carbons indicate that the overall reorientation of the molecule is isotropic. In dimethyl sulphoxide solutions, the segmental motion of the propionic side chains is very limited in bilirubin, bilirubin dimethyl ester and mesobilirubin dimethyl ester, faster in dimethoxybilirubin dimethyl ester and is very fast in the propionic residue of vinylneoxanthobilirubinic acid methyl ester. The relative mobilities of the propionic residues are interpreted on the basis of intramolecular hydrogen bonding in which the solvent participates. The dimeric form of bilirubin dimethyl ester in chloroform solutions is confirmed by the correlation time of tumbling of the backbone. In this solvent the segmental motion of the propionic side chains is rapid, indicating the probable absence of hydrogen-bonding. In bilirubin, bilirubin dimethyl ester and dimethoxybilirubin dimethyl ester, internal rotation is rapid for the endo-vinyl group and slow for the exo group, correlating with reported differences in the chemical behaviour of these residues in bile pigments.

The structure of bilirubin and of bilirubin derivatives has been studied by various physical techniques, including optical spectroscopy(1,2), optical rotatory dispersion,(4) isotope exchange(5) and proton magnetic resonance spectroscopy(2,3,5). A good deal of chemical information on bilirubin is also available(6). The interpretation of most of the experimental results, however, have been inconclusive and different possible structures of the molecule could be shown to accommodate the experimental data.

An individual assignment of certain peaks in the proton and 13C NMR spectra of bilirubin and of bilirubin dimethyl ester is described. The assignment was achieved through the spectra of vinylneoxanthobilirubinic acid and by off-resonance decoupled 13C spectra of bilirubin dimethyl ester. The signals due to the endo and exo vinyl groups were separately assigned. This assignment allows a rational interpretation of previously obtained spin-lattice relaxation times of the vinyl carbon peaks. The two vinyl groups are found to differ considerably in their motional correlation time.

Literature NMR data of bilirubin and related compounds and their interpretation in terms of structure, solution conformation and dynamic properties have been reviewed. 1H-spectrum assignments as well as solvent and temperature dependencies of the chemical shifts are described. Proton exchange rates, longitudinal relaxation times and nuclear Overhauser enhancements are surveyed. NMR is shown to provide knowledge on the basic structure, conformation, tautomerism, hydrogen bonding, acidity constants, segmental motion of side-chains, interconversion between enantiomers and aggregation—disaggregation of these compounds in solution.

The 13C NMR spectrum of dimethoxybilirubin dimethyl ester (1) is reported. Methoxyvinylneoxanthobilirubinic acid methyl ester, a compound containing one endo-vinylpyrromethene unit, was prepared and used in the assignment of the spectrum of 1.

Background The wound healing assay is the common method to study collective cell migration in vitro. Computational analyses of live imaging exploit the rich temporal information and significantly improve understanding of complex phenomena that emerge during this mode of collective motility. Publicly available experimental data can allow application of new analyses to promote new discoveries, and assess algorithms’ capabilities to distinguish between different experimental conditions. Findings A freely-available dataset of 31 time-lapse in vitro wound healing experiments of two cell lines is presented. It consists of six different experimental conditions with 4–6 replicates each, gathered to study the effects of a growth factor on collective cell migration. The raw data is available at ‘The Cell: an Image Library’ repository. This Data Note provides detailed description of the data, intermediately processed data, scripts and experimental validations that have not been reported before and are currently available at GigaDB. This is the first publicly available repository of live collective cell migration data that includes independent replicates for each set of conditions. Conclusions This dataset has the potential for extensive reuse. Some aspects in the data remain unexplored and can be exploited extensively to reveal new insight. The dataset could also be used to assess the performance of available and new quantification methods by demonstrating phenotypic discriminatory capabilities between the different experimental conditions. It may allow faster and more elaborated, reproducible and effective analyses, which will likely lead to new biological and biophysical discoveries. Electronic supplementary material The online version of this article (doi:10.1186/s13742-015-0049-6) contains supplementary material, which is available to authorized users.

1 H N.m.r. spectra of bilirubin and mesobilirubin in chloroform solutions and their temperature dependence were studied. At room temperature the spectrum of the methylene protons of the two propionic acid residues appear as two partially overlapping ABCX multiplets. Specific assignments of the signals were obtained through the 1H–1H nuclear Overhauser enhancement and selectively protondecoupled 13C spectra. Approximate conformation of the propionic acid residues in terms of the dihedral angles within the CH2CH2 residue and its angles relative to the rest of the molecule was determined on the basis of the chemical shifts, geminal, and vicinal coupling constants. The results are consistent with previous determinations of the conformation of bilirubin and mesobilirubin in chloroform solutions and in the solid state. At elevated temperatures the spectral lineshape of the propionic methylene protons of bilirubin and mesobilirubin changes drastically. The changes were successfully simulated using the DNMR5 computer program, assuming an exchange of the type ABCX A′B′C′X′⇌XCBA X′C′B′A′, caused by inversion between the two enantiomeric conformations of these molecules. The activation parameters of the exchange are ΔH‡ 74.1 ± 2.5 kJ mol–1 and ΔS‡– 8.8 ± 7.1 J K–1 mol–1 for bilirubin and ΔH‡ 72.4 ± 1.2kJ mol–1 and ΔS‡– 12.5 ± 3.8J k –1 mol–1 for mesobilirubin.

Selective and non-selective spin–lattice relaxation times (T1), nuclear Overhauser enhancements (NOE), and rates of exchange of protons in bilirubin and related compounds in chloroform solutions were measured. The NOE observed between methyl and methine protons and between lactam and pyrrole NH protons indicate that the configuration within the pyrromethenone units is exclusively syn-Z. An NOE was also observed between the protons of the carboxylic acid and the lactam NH groups of mesobilirubin. The selective T1 relaxation times, NOE values of the protons, and correlation times calculated from carbon-13 relaxation data were used for the calculation of interproton distances. These distances, as well as the extremely slow rates of exchange of the pyrrole NH protons, establish the presence of hydrogen bonds between the carboxy-residues and the lactam and pyrrole NH groups of mesobilirubin in chloroform solutions. The T1 values, chemical shifts, and rates of proton exchange in bilirubin are similar to those of mesobilirubin, indicating that the same conformation occurs for the two compounds. The conformation of bilirubin dimethyl ester is very different from that of bilirubin and mesobilirubin. It is present as a dimer even at concentrations as high as 0.17M. The proton exchange rates of both the lactam and pyrrole NH groups of bilirubin dimethyl ester are slightly slower than in a model pyrromethenone compound.