μM Of Concentration Research Articles

A series of novel 1H-indole-7-carbohydrazide derivatives with photoswitching and AIE properties: “On-off” fluorescence sensors for Cu2+

In order to exploit novel fluorescent sensors with photoswitching properties, six fluorescent molecules were synthesized via coupling 1H-indole-7-carbohydrazide and corresponding substituted formaldehyde through an acylhydrazone bond. All title compounds were characterized via1H, 13C NMR, and elemental analysis, the single crystal structure of compound IC-PD was obtained via X-ray diffraction. The compounds IC-EL and IC-4PZ exhibited aggregation-induced emission (AIE) characteristics and also with regular responses to temperature and alkalinity in the solvent system dominated via deionized water. Probes IC-PL, IC-4PZ, and IC-PD could be used as fluorescence probes to detect copper (Ⅱ) with the LODs of 0.37, 0.27, and 0.26 μM in concentration of 0–50 μM, especially extraordinary bits of complex IC-PD-Cu2+ could also exhibited bright yellow in tetrahydrofuran (THF), which ensured the convenience of detection for Cu2+ ion. The exploration on the combination mechanism of representative compound IC-PD and Cu2+ ion via FT-IR and 1H NMR, which confirmed that the proton of hydrazide was protonated via Cu2+ ion, resulting in the excited state intramolecular proton transfer (ESIPT) process was interfered. When IC-PD was irradiation to the 302 nm photostationary state (PSS), the fluorescence emission intensity of IC-PD in THF was slightly enhanced, accompanied with the increased sensitivity of detection for Cu2+. Although the improvement was not significant, it was also provided a design foundation for the development of stimuli responsive fluorescent materials with photoswitching properties.

Stable Cavitation Interferes with Aβ16-22 Oligomerization.

Ultrasound and microbubbles are used for many medical applications nowadays. Scanning ultrasound can remove amyloid-β (Aβ) aggregates in the mouse brain and restores memory in an Alzheimer's disease mouse model. In vitro studies showed that amyloid fibrils are fragmented due to the ultrasound-induced bubble inertial cavitation, and ultrasonic pulses accelerate the depolymerization of Aβ fibrils into monomers at 1 μM of concentration. Under applied ultrasound, microbubbles can be in a stable oscillating state or unstable inertial cavitation state. The latter occurs when ultrasound causes a dramatic change of bubble sizes above a certain acoustic pressure. We have developed and implemented a nonequilibrium molecular dynamics simulation algorithm to the AMBER package, to facilitate the investigation of the molecular mechanism of Aβ oligomerization under stable cavitation. Our results indicated that stable cavitation not only inhibited oligomeric formation, but also prevented the formation of β-rich oligomers. The network analysis of state transitions revealed that stable cavitation altered the oligomerization pathways of Aβ16-22 peptides. Our simulation tool may be applied to optimize the experimental conditions to achieve the best therapeutical effect.

Moscatilin Induces Apoptosis in Human Head and Neck Squamous Cell Carcinoma Cells via JNK Signaling Pathway.

Dendrobii Herba is an herbal medicine that uses the stems of Dendrobium species (Orchidacea). It has been traditionally used to treat fever, hydrodipsomania, stomach disorders, and amyotrophia. In our previous study, a bibenzyl compound, moscatilin, which is isolated from Dendrobii Herba, showed potent cytotoxicity against a FaDu human pharyngeal squamous carcinoma cell line. Prompted by this finding, we performed additional studies in FaDu cells to investigate the mechanism of action. Moscatilin induced FaDu cell death by using 5 μM of concentration and by mediating apoptosis, whereas cell proliferation following treatment with 1 μM of moscatilin was not suppressed to the same levels as by the anti-cancer agent, cisplatin. Apoptosis-related protein expression (cleaved caspase-8, cleaved caspase-7, cytochrome c, cleaved caspase-9, cleaved caspase-3, and poly (ADP-ribose) polymerase (PARP) was increased by treating with 5 μM of moscatilin. This suggests that moscatilin-mediated apoptosis is associated with the extrinsic and intrinsic apoptotic signaling pathways. In addition, moscatilin-induced apoptosis was mediated by the c-Jun N-terminal kinase (JNK) signaling pathway. Overall, this study identified additional biological activity of moscatilin derived from natural products and suggested its potential application as a chemotherapeutic agent for the management of head and neck squamous cell carcinoma.

Characteristics of new bioreductive fluorescent probes based on the xanthene fluorophore: Detection of nitroreductase and imaging of hypoxic cells

Hypoxia is a common feature of many solid tumors and is known to cause the resistance to chemotherapy and radiotherapy. Nitroreductase (NTR), a common biomarker of hypoxia, is an attractive target for the design of therapeutics and imaging agents targeting hypoxia. Under hypoxic condition, nitroreductase can reduce an aromatic nitro group conjugated to a drug or fluorophore to amine, which leads to release a free drug or fluorophore through the subsequent 1,6-rearrangment elimination. This type of 1,6-rearrangement elimination to release a drug or fluorophore has been widely used in the development of activity-based “turn on” fluorescent probes as well as targeted therapeutics such as antibody-drug conjugates (ADCs) and small molecule-drug conjugates (SMDCs). In this paper, novel “turn on” NTR-responsive fluorescent probes diversely linked to a 4-nitrobenzyl moiety via ether, carbonate, amine and carbamate linkages have been developed. The effect of variation in linkage on the release of fluorophore has been studied by the analysis of spectroscopic properties, temperature and pH stability, kinetics and concentration-dependency of the probes during NTR reaction. Fluorescent probes with an ether (10) or a carbamate (16) linkage showed biocompatible nature, high sensitivity (working below 1 μM of concentration) and strong fluorescence emission in the presence of NTR whereas they showed very low quantum yields in the absence of NTR. Finally, the probes (10, 16) were successfully applied to in vitro imaging of hypoxic cancer cells.

Serotonergic modulation of social status-dependent behavioural plasticity of the crayfish avoidance reaction.

Small crayfish usually showed escape-like dart responses to mechanical stimulation of the tailfan. Following agonistic bouts with conspecifics, dominant crayfish showed a defensive-like turn response to the same sensory stimulus. During the dart response, both uropods closed and animals walked forwards with the abdomen extended, while during the turn response the uropod on the stimulated side opened and animals turned towards the stimulus source with the abdomen frequently flexed. Using an isolated nerve cord preparation, we found that the spike activities of both the abdominal postural and uropod motor neurones in response to sensory stimulation of the exopodite reversed in dominant animals. In naive and subordinate animals, extensor motor neurones were excited and antagonistic flexor motor neurones inhibited in response to sensory stimulation. Furthermore, the spike frequency of uropod closer motor neurones increased while that of the antagonistic opener motor neurones decreased. By contrast, in more than half of the dominant animals, flexor and opener motor neurones showed excitatory responses while extensor and closer motor neurones showed inhibitory responses to the same sensory stimulation. This reverse of activity of the abdominal postural and uropod motor neurones was also observed when serotonin of more than 12.5 μM in concentration was applied.

Protective Effect of Selenomethionine on Aflatoxin B1-Induced Oxidative Stress in MDCK Cells

AFB1 is a mycotoxin which exerts their cytotoxicity through increasing oxidative damage in target organ. Kidney is one of target organs vulnerable to damage caused by AFB1. In this study, Madin-Darby canine kidney (MDCK) cells were used to evaluate the AFB1-induced cell damage by the MTT assay. The results revealed that the toxic effect of AFB1 on MDCK cells is both dose and time dependent. Half maximal toxic concentration (IC50) was noted at 0.25 μg/ml of AFB1. Further, protective effect of six different concentrations (0.2, 0.8, 1, 2, 4, and 8 μM) of selenomethionine (SeMet) was observed against 0.25 μg/ml of AFB1-induced damage. The results showed that 0.25 μg/ml of AFB1 caused significant increase in oxidative stress, which was demonstrated by significant increase of malondialdehyde (MDA) level, reduction of intracellular GSH level, as well as GPX1 activity and mRNA level in MDCK cells when compared with control. SeMet protected the cells from AFB1-induced oxidative damage in a dose-dependant manner. Good protection could be achieved between 1 and 4 μM of concentration. Amid this range, MDA level significantly decreased while intracellular GSH level and GPX1 activity in addition to mRNA level significantly increased. Moreover, cell viability was significantly improved. It could be concluded that SeMet is a potential antioxidative agent to alleviate AFB1-induced oxidative stress.

Unique Features of the Anti-parallel, Heterodimeric Coiled-coil Interaction between Methyl-cytosine Binding Domain 2 (MBD2) Homologues and GATA Zinc Finger Domain Containing 2A (GATAD2A/p66α)

The methyl-cytosine binding domain 2 (MBD2)-nucleosome remodeling and deacetylase (NuRD) complex recognizes methylated DNA and silences expression of associated genes through histone deacetylase and nucleosome remodeling functions. Our previous structural work demonstrated that a coiled-coil interaction between MBD2 and GATA zinc finger domain containing 2A (GATAD2A/p66α) proteins recruits the chromodomain helicase DNA-binding protein (CHD4/Mi2β) to the NuRD complex and is necessary for MBD2-mediated DNA methylation-dependent gene silencing in vivo (Gnanapragasam, M. N., Scarsdale, J. N., Amaya, M. L., Webb, H. D., Desai, M. A., Walavalkar, N. M., Wang, S. Z., Zu Zhu, S., Ginder, G. D., and Williams, D. C., Jr. (2011) p66α-MBD2 coiled-coil interaction and recruitment of Mi-2 are critical for globin gene silencing by the MBD2-NuRD complex. Proc. Natl. Acad. Sci. U.S.A. 108, 7487-7492). The p66α-MBD2 interaction differs from most coiled-coils studied to date by forming an anti-parallel heterodimeric complex between two peptides that are largely monomeric in isolation. To further characterize unique features of this complex that drive heterodimeric specificity and high affinity binding, we carried out biophysical analyses of MBD2 and the related homologues MBD3, MBD3-like protein 1 (MBD3L1), and MBD3-like protein 2 (MBD3L2) as well as specific mutations that modify charge-charge interactions and helical propensity of the coiled-coil domains. Analytical ultracentrifugation analyses show that the individual peptides remain monomeric in isolation even at 300 μM in concentration for MBD2. Circular dichroism analyses demonstrate a direct correlation between helical content of the coiled-coil domains in isolation and binding affinity for p66α. Furthermore, complementary electrostatic surface potentials and inherent helical content of each peptide are necessary to maintain high-affinity association. These factors lead to a binding affinity hierarchy of p66α for the different MBD2 homologues (MBD2 ≈ MBD3 > MBD3L1 ≈ MBD3L2) and suggest a hierarchical regulatory model in tissue and life cycle stage-specific silencing by NuRD complexes.

A quasi-droplet optofluidic ring resonator laser using a micro-bubble

Optofluidic ring resonator lasers based on micro-bubbles filled with liquid gain medium are demonstrated. Due to the sub-micron wall thickness of the micro-bubble, significant amount of the electric field resides inside the liquid. Consequently, micro-bubbles mimic the droplets in air that have 3-dimensional optical confinement, extremely high Q-factors, and versatility in handling liquids of different refractive index. Furthermore, they enable repetitive interrogation and easy directional laser emission out-coupling without evaporation or size/shape variations. The laser using Rhodamine 6G in methanol is achieved with a threshold of 300 nJ/mm2 and 5.3 μJ/mm2 for 1 mM and 10 μM in concentration, respectively.

Abstract 2296: Sorafenib inhibits hepatocyte growth factor-induced epithelial mesenchymal transition in hepatocellular carcinoma

Abstract Sorafenib is a multikinase inhibitor with activity against Raf kinase and several receptor tyrosine kinases, including vascular endothelial growth factor receptor2, platelet-derived growth factor receptor. Epithelial mesenchymal transition (EMT) describes a process wherein static epithelial cells lose cell-cell contacts, acquire mesenchymal features and manifest a migratory phenotype, mediating malignant phenotypes for cancer cells. It remains unclear for involvement of Sorafenib against EMT, especially in hepatocellular carcinoma (HCC). Hepatocyte growth factor (HGF) activated HGF/MET signaling pathway in HepG2 and Huh7 cells and resulted in cell scattering and spindle-shaped morphology, changes that are characteristic of EMT. SNAI1 is a key transcription factor known to be involved in EMT. HGF up-regulated SNAI1 and N-cadherin expression, and down-regulated E-cadherin in a dose- and time-dependent manner. Knockdown of SNAI1 by siRNA almost completely inhibited these morphological changes, indicating that SNAI1 was required for HGF-induced EMT in HCC cell lines. Similarly, Sorafenib and the MEK inhibitor U0126 markedly inhibited the HGF-induced SNAI1 expression and these morphological changes at 10 μM of concentration, whereas PI3 kinase inhibitor Wortmannin did not. In conclusion, Sorafenib exerts a potent inhibitory activity against EMT via ERK/SNAI1 in HCC. This activity may provide an additional clinical benefit in patients with HCC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2296.

The behaviour of inositol 1,3,4,5,6-pentakisphosphate in the presence of the major biological metal cations

The inositol phosphates are ubiquitous metabolites in eukaryotes, of which the most abundant are inositol hexakisphosphate (InsP6) and inositol 1,3,4,5,6-pentakisphosphate [Ins(1,3,4,5,6)P5)]. These two compounds, poorly understood functionally, have complicated complexation and solid formation behaviours with multivalent cations. For InsP6, we have previously described this chemistry and its biological implications (Veiga et al. in J Inorg Biochem 100:1800, 2006; Torres et al. in J Inorg Biochem 99:828, 2005). We now cover similar ground for Ins(1,3,4,5,6)P5, describing its interactions in solution with Na+, K+, Mg2+, Ca2+, Cu2+, Fe2+ and Fe3+, and its solid-formation equilibria with Ca2+ and Mg2+. Ins(1,3,4,5,6)P5 forms soluble complexes of 1:1 stoichiometry with all multivalent cations studied. The affinity for Fe3+ is similar to that of InsP6 and inositol 1,2,3-trisphosphate, indicating that the 1,2,3-trisphosphate motif, which Ins(1,3,4,5,6)P5 lacks, is not absolutely necessary for high-affinity Fe3+ complexation by inositol phosphates, even if it is necessary for their prevention of the Fenton reaction. With excess Ca2+ and Mg2+, Ins(1,3,4,5,6)P5 also forms the polymetallic complexes [M4(H2L)] [where L is fully deprotonated Ins(1,3,4,5,6)P5]. However, unlike InsP6, Ins(1,3,4,5,6)P5 is predicted not to be fully associated with Mg2+ under simulated cytosolic/nuclear conditions. The neutral Mg2+ and Ca2+ complexes have significant windows of solubility, but they precipitate as [Mg4(H2L)]·23H2O or [Ca4(H2L)]·16H2O whenever they exceed 135 and 56 μM in concentration, respectively. Nonetheless, the low stability of the [M4(H2L)] complexes means that the 1:1 species contribute to the overall solubility of Ins(1,3,4,5,6)P5 even under significant Mg2+ or Ca2+ excesses. We summarize the solubility behaviour of Ins(1,3,4,5,6)P5 in straightforward plots.Electronic supplementary materialThe online version of this article (doi:10.1007/s00775-009-0510-z) contains supplementary material, which is available to authorized users.

Encapsulated gadolinium zirconate pyrochlore particles in soda borosilicate glass as novel radioactive waste form

Gadolinium zirconate pyrochlore crystals, with a potential for hosting radioactive elements, were encapsulated in a soda borosilicate glass matrix forming a composite material. The fabrication process involved mixing as a powder followed by hot pressing at a relatively low temperature of 620 °C. Composites containing pyrochlore particles of mean particle size <60 μm in concentration of up to 40 vol% exhibited a homogeneous distribution of the particles in the glass matrix. The absence of debonding of Gd zirconate particles or deflection of cracks during fracture, indicates that a strong interface between the glass matrix and the gadolinium zirconate particles was achieved, which suggests a high mechanical strength and hardness of the composites. Mechanical tests were carried out and it was confirmed that the presence of the gadolinium zirconate particles increased the Young's modulus and fracture toughness of the composite by 35% and >100%, respectively, in comparison with plain borosilicate glass. The results indicate that the new waste forms are superior in terms of structural integrity and fracture behaviour than plain borosilicate glass waste forms.

Homogeneous Ice Nucleation in Subtropical and Tropical Convection and Its Influence on Cirrus Anvil Microphysics

Abstract This study uses a unique set of microphysical measurements obtained in a vigorous, convective updraft core at temperatures between −33° and −36°C, together with a microphysical model, to investigate the role of homogeneous ice nucleation in deep tropical convection and how it influences the microphysical properties of the associated cirrus anvils. The core and anvil formed along a sea-breeze front during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers–Florida Area Cirrus Experiment (CRYSTAL–FACE). The updraft core contained two distinct regions as traversed horizontally: the upwind portion of the core contained droplets of diameter 10–20 μm in concentrations of around 100 cm−3 with updraft speeds of 5–10 m s−1; the downwind portion of the core was glaciated with high concentrations of small ice particles and stronger updrafts of 10–20 m s−1. Throughout the core, rimed particles up to 0.6-cm diameter were observed. The anvil contained high concentrations of both small particles and large aggregates. Thermodynamic analysis suggests that the air sampled in the updraft core was mixed with air from higher altitudes that descended along the upwind edge of the cloud in an evaporatively driven downdraft, introducing free-tropospheric cloud condensation nuclei into the updraft below the aircraft sampling height. Farther downwind in the glaciated portion of the core, the entrained air contained high concentrations of ice particles that inhibit droplet formation and homogeneous nucleation. Calculations of droplet and ice particle growth and homogeneous ice nucleation are used to investigate the influence of large ice particles lofted in updrafts from lower levels in this and previously studied tropical ice clouds on the homogeneous nucleation process. The preexisting large ice particles act to suppress homogeneous nucleation through competition via diffusional and accretional growth, mainly when the updrafts are &amp;lt; 5 m s−1. In deep convective updrafts &amp;gt; 5–10 m s−1, the anvil is the depository for the small, radiatively important ice particles (homogeneously nucleated) and the large ice particles from below (heterogeneously or secondarily produced, or recycled).

Signal Transduction in Eclosion Hormone-induced Secretion of Ecdysis-triggering Hormone

Inka cells of insect epitracheal glands (EGs) secrete preecdysis and ecdysis-triggering hormones (PETH and ETH) at the end of each developmental stage. Both peptides act in the central nervous system to evoke the ecdysis behavioral sequence, a stereotype behavior during which old cuticle is shed. Secretion of ETH is stimulated by a brain neuropeptide, eclosion hormone (EH). EH evokes accumulation of cGMP followed by release of ETH from Inka cells, and exogenous cGMP evokes secretion of ETH. The secretory responses to EH and cGMP are inhibited by the broad-spectrum kinase inhibitor staurosporine, and the response to EH is potentiated by the phosphatase inhibitor calyculin A. Staurosporine did not inhibit EH-evoked accumulation of cGMP. Changes in cytoplasmic Ca2+ in Inka cells during EH signaling were monitored via fluorescence ratioing with fura-2-loaded EGs. Cytoplasmic Ca2+ increases within 30-120 s after addition of EH to EGs, and it remains elevated for at least 10 min, corresponding with the time course of secretion. Secretion is increased in dose-dependent manner by the Ca2+-ATPase inhibitor thapsigargin, a treatment that does not elevate glandular cGMP above basal levels. The secretory response to EH is partially inhibited in glands loaded with EGTA, while cGMP levels are unaffected. These findings suggest that EH activates second messenger cascades leading to cGMP accumulation and Ca2+ mobilization and/or influx and that both pathways are required for a full secretory response. cGMP activates a staurosporine-inhibitable protein kinase. We propose that Ca2+ acts via a parallel cascade with a time course that is similar to that for cGMP activation of a cGMP-dependent protein kinase.

In situ observations of contrail microphysics and implications for their radiative impact

In this study we present the microphysical characteristics of 21 jet contrail clouds sampled in situ and examine the possible effects of exhaust on natural cirrus and radiative effects of contrails. Microphysical samples were obtained with Particle Measuring Systems (PMS) 2D‐C, 1D‐C, and FSSP probes. About one half of the study contrails were generated by the sampling aircraft, a Cessna Citation, primarily at times of 3–15 min after generation; the source and age of the others is unknown. On average, the contrails contained particles of mean diameter of the order of 10 μm in concentrations exceeding 10,000 L−1. Contrails embedded in natural cirrus appeared to have little effect on the natural cloud microphysics. Anomalous diffraction theory was used to model radiative properties of sampled contrails. The contrail cirrus showed considerably more spectral variation in extinction and absorption efficiencies than natural cirrus because of the large numbers of small crystals in contrails. Embedded contrails also displayed greater emissivity and emission than natural cirrus and a greater spectral variation in transmission.

The production of high ice‐crystal concentrations in stratiform clouds

AbstractThe appearance of ice crystals in high concentrations, of ∼ 500 1−1 in the −3 to −8°C zone of stratiform clouds, recently reported by Bower et al., is explained by the shedding of splinters by riming ice crystals at rates observed in the laboratory earlier by Hallett and Mossop. The appearance of a second maximum at −15°C, with small crystals of diameter less than 125 μm in concentrations of ∼ 1000 1−1, is attributed to the transport of small ice splinters produced in the Hallet‐Mossop zone that grow at small ice supersaturations in weak updraughts between the −8°C and −12°C levels, and thereafter at water saturation in convective cells containing liquid water and updraughts of 1 m s−1 between the −12°C and −15°C levels.

Changes in phosphoadenylate concentrations and adenylate energy charge as an integrated biochemical measure of stress in invertebrates: The effects of cadmium on the freshwater clamCorbicula fluminea

Concentrations of phosphadenylates ATP, ADP and AMP were measured in foot muscle tissue of the Asian clam, Corbicula fluminea Muller, by the luciferin‐luciferase bioluminescence technique. Total adenylate concentration μM · g‐ 1, dry weight and adenylate energy charge [AEC = (ATP+1/2ADP)/(ATP + ADP + AMP] were calculated. The effects of laboratory acclimation, starvation and exposure to 0.005, 0.05, 0.5 and 5.0mgCd · l‐1 were investigated. We observed no significant difference between the AEC of clams collected from the Savannah River Channel below Augusta, Georgia and those collected from Clark Hill reservoir on the Savannah River above Augusta. When C. fluminea, collected from the Savannah River were taken to the laboratory and fed and maintained in aerated water at 21°C, the AEC increased from 0.76±0.06 to 0.95±0.01 (x±95% CI, n = 8). This indicates that C. fluminea in the Savannah River were living under sub‐optimal conditions. Starvation for 10 and 20 days did not significantly decrease the AEC. Howe...

Production of Ice Crystals in Slightly Supercooled Cumulus

PERHAPS the most puzzling observation in cloud physics reveals that some slightly supercooled cumulus clouds, with summit temperatures only a few degrees below 0° C, contain high concentrations of ice crystals—two to four orders of magnitude greater than the concentrations of ice nuclei measured in clear air at the same level. According to a series of careful and detailed aircraft observations and measurements by Mossop and his colleagues, such high concentrations of crystals occur only in aged cumulus that has been in existence for some time and acquired widths of several kilometres but are absent from newly rising cloud towers. They are also absent from slightly supercooled stratocumulus clouds. Mossop et al.1,2 report small ice crystals in concentrations of 10 to 100 l−1 in clouds with summit temperatures as high as − 8° C but always in association with rimed ice pellets of diameter of order 1 mm in concentrations of order 1 l−1 and with large droplets of r>250 µm in concentrations of order 100 m−3. The concentrations of ice nuclei active at − 8° C are below those that can be reliably measured by conventional techniques but probably do not exceed 1 m−3.