Glass Fiber Filter Paper Research Articles

Determination of the relaxation characteristics of sugar glasses embedded in microfiber substrates

Recently there has been considerable interest in developing sugar glasses that enable storage of biologics without refrigeration. Microfiber filter papers are good substrates for drying biologics in the presence of sugar glass-formers, providing for an even distribution of samples and an enhanced surface area for drying, but the opaqueness prevents macroscopic observation of the sample and can introduce complexities that impede physical characterization. Because drying kinetics and processing conditions can impact the relaxation dynamics (e.g., α- and β-relaxation), which can influence the efficacy of the glass as a stabilizer, methods are needed that can enable a determination of relaxation phenomena of sugar glasses in such complex environments. In this study we present a method which provides verification of the absence of crystallinity following drying on glass fiber filter paper and also enables the determination of relaxation characteristics of amorphous sugar compositions embedded within these filter substrates. Using material pockets to contain the sugar glass-embedded microfiber paper, the α-relaxation temperature, Tα, was determined as a function of the water content in trehalose and sucrose samples using Dynamic Mechanical Analysis (DMA). Results were verified by comparison with previous calorimetric and spectroscopic studies. The data also demonstrated the plasticizing effects of water, as Tα was shown to correlate with water content via a Gordon–Taylor-like relationship. Our findings validate a new approach for determining the relaxation characteristics of microfiber embedded sugar glasses, and offer new insights into the relaxation characteristics of glasses prepared by microwave-assisted drying on filter papers.

Characteristics of trace metals in fine (PM2.5) and inhalable (PM10) particles and its health risk assessment along with in-silico approach in indoor environment of India

Indoor concentrations of fine (PM2.5: aerodynamic diameter ≤ 2.5) and inhalable (PM10: aerodynamic diameter ≤ 10 μm) particles and its associated toxic metals are of concern now-a-days due to its effects on human health and environment. PM10 and PM2.5 samples were collected from indoor microenvironments on glass fiber and PTFE filter paper using low volume air sampler in Pune. The average concentration of PM2.5 and PM10 were 89.7 ± 43.2 μg m−3 and 138.2 ± 68.2 μg m−3 at urban site while it was 197.5 ± 84.3 and 287 ± 92 μg m−3 at rural site. Trace metals such as Cd, Co, Cr, Cu, Fe, Mn, Pb, Sb and Zn in particulate matter were estimated by ICP–AES. Concentrations of crustal metals were found to be higher than the carcinogenic metals in both the microenvironments. On the contrary the soluble and bio-availability fraction of carcinogenic metals were found higher thus it may cause the higher risk to human health. Therefore, cancer risk assessment of carcinogenic metals; Cr, Ni and Cd was calculated. Among the carcinogenic metals, Ni showed highest cancer risk in indoor PM. The higher cancer risk assessment of Ni has been supported by In-silico study which suggested that Ni actively formed co-ordination complex with histone proteins (i.e. H3–Ni/H4–Ni) by maintaining strong hydrogen bonding interactions with Asp and Glu residues of nucleosomal proteins. Present In-silico study of Ni-histone complexes will help to emphasize the possible role of Asp and Glu residues in DNA methylation, deacetylation and ubiquitinations of nucleosomal proteins. Hence, this study could pave the way to understand the structural consequence of Ni in nucleosomal proteins and its impact on epigenetic changes which ultimately cause lung and nasal cancer.

Environmental fate and behavior of some PAHs at roadside ambient air in a fast developing city environment of northern India

Atmospheric polycyclic aromatic hydrocarbon (PAH) concentrations were measured at two monitoring stations (interior and outskirt of the city) for a span of one year during 2013 at Jalandhar, a fast developing city in the state of Punjab in northern India. The objective of the study was to ascertain PAH contamination levels, distribution behavior, seasonal variation, and ratio of low and high carcinogenic PAHs in the ambient air. Samples were collected using high volume sampler fitted with glass fiber filter paper and polyurethane foam plug (PUF) erected at two monitoring stations of the city. The PAHs were extracted by soxhlet using toluene as a solvent and analyzed on gas chromatography-flame ionization detector. Recovery range was found between 30% and 70% with the lower value corresponding to the low molecular weight PAH compound.The mean concentration of total low/high carcinogenic PAHs (among 16 PAHs) for the year was found to be 4.79 and 5.49 ng/m3 (ratio 1:1.14) in the interiors and 3.55 and 5.79 n...

DNA Promoter Methylation-dependent Transcription of the Double C2-like Domain β (DOC2B) Gene Regulates Tumor Growth in Human Cervical Cancer

Double C2-like domain β (DOC2B) gene encodes for a calcium-binding protein, which is involved in neurotransmitter release, sorting, and exocytosis. We have identified the promoter region of the DOC2B gene as hypermethylated in pre-malignant, malignant cervical tissues, and cervical cancer cell lines by methylation-sensitive dimethyl sulfoxide-polymerase chain reaction and bisulfite genome sequencing; whereas, it was unmethylated in normal cervical tissues (p < 0.05). The promoter hypermethylation was inversely associated with mRNA expression in SiHa, CaSki, and HeLa cells and treatment with demethylating agent 5-aza-2-deoxycytidine restored DOC2B expression. The region -630 to +25 bp of the DOC2B gene showed robust promoter activity by a luciferase reporter assay and was inhibited by in vitro artificial methylation with Sss1 methylase prior to transient transfections. Overexpression of the DOC2B gene in SiHa cells when compared with controls showed significantly reduced colony formation, cell proliferation, induced cell cycle arrest, and repressed cell migration and invasion (p < 0.05). Ectopic expression of DOC2B resulted in anoikis-mediated cell death and repressed tumor growth in a nude mice xenograft model (p < 0.05). DOC2B expressing cells showed a significant increase in intracellular calcium level (p < 0.05), impaired AKT1 and ERK1/2 signaling, and induced actin cytoskeleton remodeling. Our results show that promoter hypermethylation and silencing of the DOC2B gene is an early and frequent event during cervical carcinogenesis and whose reduced expression due to DNA promoter methylation may lead to selective cervical tumor growth.

Concentration and source identification of polycyclic aromatic hydrocarbons (PAHs) in PM10 of urban, industrial and semi-urban areas in Malaysia

Particulate matter (PM10) associated with polycyclic aromatic hydrocarbons (PAHs) in ambient air were determined at two sites within the Klang Valley, Kuala Lumpur (urban, KL) and Petaling Jaya (industrial, PJ), and one site outside the Klang Valley, Bangi (semi-urban, BG). This study aimed to determine the concentration and distribution of PAHs in PM10 and the source of origin through principal component analysis (PCA) and diagnostic ratio analysis. This study also assessed the health risk from exposure to airborne BaPeq. PM10 samples were collected on glass fiber filter paper using a High Volume Sampler (HVS) for 24 h between September 2010 and April 2011. The filter papers with PM10 were extracted using dichloromethane-methanol (3:1), and analysis of 16 USEPA priority PAHs was determined using gas chromatography with mass spectra (GC–MS). Health risk assessment was estimated using toxic equivalency factors (TEFs) and incremental lifetime cancer risk (ILCR) which quantitatively estimate the exposure risk for age specific group. The results showed that the total PAHs concentrations throughout seasonal monsoons for KL, PJ and BG ranged from 1.33 ng m−3 to 2.97 ng m−3, 2.24 ng m−3 to 4.84 ng m−3 and 1.64 ng m−3 to 3.45 ng m−3 respectively. More than 80% of total PAHs consisted of 5-ring and 6-ring PAHs such as benzo[a]pyrene (BaP), indeno[1,2,3-cd]pyrene (IcP), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF) and benzo[g,h,i]perylene (BgP). The presence of benzo[g,h,i]perylene (BgP) with high concentration at all locations suggested a source indicator for traffic emission. PCA and diagnostic ratio analysis also suggested substantial contributions from traffic emission with minimal influence from coal combustion and natural gas emissions. The use of total BaPeq concentration provide a better estimation of carcinogenicity activities, where they contributed to more than 50% of the potential health risk. Health risk assessment showed that the estimated incremental lifetime cancer risk (ILCR) from exposure to airborne BaPeq is negligible at all sampling sites for all age specific group.

A direct chemical method for the rapid, sensitive and cost effective detection of phosphite in plant material

Phosphite application mitigates diseases caused by oomycete plant pathogens. Tissue concentrations of phosphite above 1 mM are generally required for disease protection. Determining the concentration of phosphite in plant material requires extensive extraction and derivatisation procedures prior to separation by gas–liquid chromatography (GLC). This paper describes a direct chemical method to estimate the concentration of phosphite using a silver nitrate reagent. Glass fiber filter papers were saturated with a 1 M aqueous solution of silver nitrate (adjusted to pH 2.5 with nitric acid) and dried for 2 h at 60 °C. 20 μL of polyvinylpolypyrrolidone treated aqueous plant extract was adsorbed onto the filter paper and incubated in the dark at room temperature (25 °C) for 1 h. The presence of phosphite in the extract reduces the silver ions to elemental silver resulting in a grey-black precipitate that is clearly visible. The method is rapid, sensitive and inexpensive, and can detect phosphite at concentrations of 1 mM in 20 μl of aqueous extract from 100 mg of fresh plant material. Samples analysed by this method gave similar results to analysis by GLC, indicating the method can be used in the field or the laboratory to determine uptake and distribution phosphite in the plant, the retention of phosphite over time and the timing of phosphite reapplication.

Determination of glyphosate in air of workplaces by ion chromatography

To establish a method for determining glyphosate in the air of workplaces by ion chromatography. Ultra-fine glass fiber filter paper was used to collect glyphosate from the workplace air. After being ultrasonically eluted with deionized water, samples were determined by ion chromatography using a conductivity detector. Within the range of 0.05-1.00 mg/L, a linear relationship was found with a limit of detection of 0.003 mg/m(3). The minimum detectable concentration was 0.000 41 mg/m(3) (calculated by sampling 75 L of air). For three different concentrations of glyphosate, the intra-batch relative standard deviations (RSDs) were 1.8%, 1.6%, and 0.8%, respectively, and the inter-batch RSDs were 1.9%, 2.1%, and 2.2%, respectively. The recovery rate ranged from 94.8% to 97.4%. The elution efficiency ranged from 94.5% to 96.7%. The sampling efficiency was 100%. Samples could be stored at room temperature for at least 7 days. This presented method meets the requirements of Guide for establishing occupational health standards-Part 4: Determination methods of air chemicals in workplace and is feasible for determination of glyphosate in the air of workplaces.

Construction a process to measurement the indoor radon concentration

Radon is a naturally radioactive gas , but it causes lung cancer to humans. The risk of lung cancer due to radiation depends on the amount of radon inhalation and radon exposure time. In Vietnam, radon concentrations are usually determined by RAD7, however RAD7 just showed the immediate values of radon, and have to regularly calibrate it. The construction process to determine the accumulates indoor radon concentration by detector CR- 39 in order to be widely used in the study of environmental pollution, especially the study of health risks of radon for humans and mapping radon pollution.&#x0D; Detector CR - 39 is placed in a 7 cm - plastic holder, and in exposure time, the holders were covered with glass fiber filter paper ∅ 47mm on the bottom of the detector to avoid the exposure of dust. Then it is hung in the indoor location as Vietnam Standard 7889:2008. After 3 months, holders are returned to a laboratory, and CR - 39 will be soaked in 6M NaOH at 700C. Indoor radon concentrations will be proportional to the density traces obtained on CR-39.&#x0D; The study uses an radium 226 source of the NIST (National Institute for Standards and Technology) with the released radon coefficient : f = 0.891 ± 0.015. Results show the calibration factor K is 4.533 ± 0.218 [(Bq.m-3. day)]/(tracks / CR-39)]. Using K factor, we can determine the cumulative indoor radon concentration.

Characterization of PM10 in the ambient air during Deepawali festival of Rajnandgaon district, India

Deepawali is one of the main festivals for Hindu religion which falls in the period October–November every year with great fireworks display. In this study, we investigated the levels of water soluble ions and heavy metals—during the fireworks festival in Rajnandgaon, Central India. The chemical compositions and noise level distributions are reported from the sampling site. First time during Deepawali, air quality was studied in this area, The Aerosol samples of PM10 (particle aerodynamic diameter <10 μm) are collected in October 24–28, 2011. Aims of the present studies are (1) To describe the particulate concentrations and associated chemical species during Deepawali festival, (2) To recognize the noise level in Deepawali festival. For study, the samples were collected in glass fiber filter paper and analyzed for the major water soluble ions F−, Cl−, NO3 −, SO4 2−, Na2+, NH4 +, K+, Ca2+, and Mg2+ employing ion chromatograph. Concentration of heavy metals was analyzed by ICP-MS and was observed to occur in order Fe > Zn > Pb > Ni > Cr > Cd. The result revels that all concentration are above the permissible limit fixed by CPCB, USPEA, and WHO standard. It is concluded that the burning of fireworks during Deepawali festival was the main source of heavy metals and ion.

Technical Note: A novel rocket-based in situ collection technique for mesospheric and stratospheric aerosol particles

Abstract. A technique for collecting aerosol particles between altitudes of 17 and 85 km is described. Spin-stabilized collection probes are ejected from a sounding rocket allowing for multi-point measurements. Each probe is equipped with 110 collection samples that are 3 mm in diameter. The collection samples are one of three types: standard transmission electron microscopy carbon grids, glass fibre filter paper or silicone gel. Collection samples are exposed over a 50 m to 5 km height range with a total of 45 separate ranges. Post-flight electron microscopy will give size-resolved information on particle number, shape and elemental composition. Each collection probe is equipped with a suite of sensors to capture the probe's status during the fall. Parachute recovery systems along with GPS-based localization will ensure that each probe can be located and recovered for post-flight analysis.

Use of constant wavelength synchronous spectrofluorimetry for identification of polycyclic aromatic hydrocarbons in air particulate samples

We have developed a simple, rapid, inexpensive method for the identification of fluoranthene (Flan), benz(a)anthracene (BaA), benzo(a)pyrene (BaP), benzo(k)fluoranthene (BkF), pyrene (Pyr), benz(ghi)perylene (BghiP) in suspended particulate matter in an urban environment of Delhi. Suspended particulate matter samples of 24h duration were collected on glass fiber filter papers. Polycyclic aromatic hydrocarbons (PAHs) were extracted from the filter papers using dichloromethane (DCM) and hexane with ultrasonication method. Comparison of the characteristic emission of spectra of PAHs with standard spectra indicated the degree of condensation of aromatic compounds present in investigated mixtures. It was also possible to identify some individual compounds. However, this identification could be more effective with the use of the respective values of Δλ parameter for each particular component of the mixture.

Diffusivity of 1-methylcyclopropene in spinach and bok choi leaf tissue, disks of tomato and avocado fruit tissue, and whole tomato fruit

Gaseous 1-methylcyclopropene (1-MCP) has been widely employed for delaying ripening and senescence of harvested fruit and vegetables; however, details on ingress of gaseous1-MCP in plant tissues, which might contribute to differences in responsiveness of different horticultural commodities to 1-MCP, have not been reported. In this study, we used spinach and bok choi leaves, disks from tomato epidermis, stem-scar and avocado-exocarp tissues, and whole tomato fruit to examine ingress of gaseous 1-MCP. Using a dual-flask system, equilibration of 20μLL−1 (831μmolm−3) 1-MCP through leaf tissue was reached within 1–2h, and paralleled 1-MCP transfer through glass-fiber filter paper. For disks derived from fruit tissues, changes in 1-MCP concentrations in the dual-flask system showed anomalous patterns, declining as much as 70% in source flasks with negligible accumulation in sink flasks. The pattern of 1-MCP distribution was markedly different from that of ethylene, which approached equal distribution with tomato stem-scar and avocado exocarp but not tomato epidermis tissues. 1-MCP ingress was further addressed by exposing whole tomato fruit to 20μLL−1 1-MCP followed by sampling of internal fruit atmosphere. Tomato fruit accumulated internal gaseous 1-MCP rapidly, reaching approximately 8–9μLL−1 within 3–6h at 20°C. Internal 1-MCP concentration ([1-MCP]) declined around 74 and 94% at 1 and 3h after exposure, respectively. Ingress was similar at all ripening stages and reduced by 45% in fruit coated with commercial wax. Blocking 1-MCP ingress through stem- and blossom-scar tissues reduced accumulation by around 60%, indicating that ingress also occurs through epidermal tissue. Fruit preloaded with 1-MCP and immersed in water for 2h retained about 45% of post-exposure gaseous [1-MCP], indicating that 1-MCP is not rapidly sorbed or metabolized by whole tomato fruit. Rapid ingress of gaseous 1-MCP was also observed in tomato fruit exposed to aqueous 1-MCP. Both accumulation and post-exposure decline in internal gaseous [1-MCP] are likely to vary among different fruit and vegetables in accordance with inherent sorption-capacity, surface properties (e.g., waxes, stoma), volume and continuity of gas-filled intercellular spaces, and tissue hydration.

Indoor/outdoor relationship of trace metals in the atmospheric particulate matter of an industrial area

Present study is based on the measurement and monitoring of indoor and outdoor atmospheric particulate matter from an industrial area (Wah Cantt, Pakistan). The particulate samples are collected on glass fiber filter paper using high volume air sampler. Trace metals (Cd, Co, Cr, Cu, Fe, Mn, Pb, Sb and Zn) in the particulate samples are estimated by atomic absorption spectrometry. On the average TSP level is significantly higher in outdoor atmosphere than indoor, and both of them are higher than WHO and USEPA standards. The distribution of trace metals is considerably diverse in indoor and outdoor particulates. Average concentrations of Fe, Zn, Co, Cr and Mn are significantly higher in outdoor particulates, whereas Cu and Pb levels are considerably higher in the indoor particulates. Source apportionment carried out by PCA and CA is diverse in indoor/outdoor particulates and the major pollution sources identified are industrial activities, automobile emissions and soil derived dust. Among the trace metals, Cd, Sb, Zn, Pb and Co are found to be highly enriched in the atmospheric particulate matter. The present atmospheric trace metals levels are also compared with those reported from other regions around the world, and are many-folds higher than previously reported results.

Determination of carcinogenic polycyclic aromatic hydrocarbons (pahs), anthracene in different variety of fish samples in the Bangsai river of Bangladesh

Carcinogenic polycyclic aromatic hydrocarbons (PAHs), widely scattered in the environment because of inadequate combustion of fuels, are an important class of toxicological compounds. In the past decade, PAHs have drawn considerable attention because of their possible contamination to the environment and foodstuffs. A crude extract of the fish samples collected from the most polluted part of Bangsai river at Saver industrial zone was analyzed for the presence of polycyclic aromatic hydrocarbon, anthracene, by gas chromatography-mass spectrometry (GC-MS). Asuitable procedure for the extraction of PAHs from the fish sample was developed. A multi-layer clean-up (silica gel) column was used, followed by glass fiber filter (GFF) paper to eliminate the interfering organic compounds as well as lipids, fat and foreign particles. It was observed that PAHs deposition on the samples takes place in different morphological parts of the biological materials. Analysis was made for environmentally important PAHs and the results, the methods and some associatedproblems are discussed. Anthracene was found in almost all fish samples with the concentration in edible fishes collected from the Bangsai river being 0.761 to 3.294 ìg/g. This concentration is within the range reported for other comparable regions of the world. Thus, it was suggested PAHs is oil contamination originating from the effluents of different industries such as tannery, dye, plastic, chemical, fertilizer or spillage’s and/or heavy ship traffic. However, the high concentration of carcinogenic anthracene encountered in these fishes should be considered serious as it is hazardous to human health. Based on fish consumption by Bangladeshi population, the daily intake of total carcinogens was 0.15 ng/person/day. Recovery studies with fortified samples indicated that the recovery efficiency for anthracene was 85.32%. It is concluded that three fish samples: baim, bata and taki were contaminated by the various aspects such as industrial effluents, air, highway vehicle exhaust and highwaytar samples.

Naphthalene, a polycyclic aromatic hydrocarbon, in the fish samples from the Bangsai river of Bangladesh by gas chromatograph–mass spectrometry

Naphthalene, a polycyclic aromatic hydrocarbon (PAH), was detected and quantified in the selected varieties of fishes collected from the Bangsai river, one of the contaminated rivers located at Savar near the Dhaka Export Processing Zone (DEPZ), Bangladesh, during the period October 2009. Naphthalene, a carcinogenic compound, was analyzed by GC–MS as it was in the mixture of dichloromethane–hexane (1:1) crude extract of the flesh of fish samples collected from the aforesaid river. A suitable and reliable procedure for the extraction of naphthalene from the fish sample has been developed. A multi-layer clean-up (silica gel) column was used, followed by glass fiber filter (GFF) paper to eliminate the interfering organic compounds as well as the lipids and fat. It was observed that PAHs deposition on the samples takes place in different morphological parts of the biological materials. The PAH, naphthalene, was found in almost all of the fish samples and the concentration of which was in the range 0.030–1.004μg/g. Recovery studies with fortified samples indicated that the recovery efficiency for naphthalene was about 79.14%. This concentration is within the range of values reported for other comparable regions of the world.

Impact of particle size on distribution of major ions in acid- and water-soluble components of PM10 atmospheric aerosols in the coastal region of Mumbai

In this study, the concentration of acid and water-soluble ions (Na+, K+, Mg++, Ca++, F−, Cl−, NO3− and SO4− −) in different particle size range (>1.1–<2.0μm, >2.0–<3.3μm, >3.3–<4.7μm, >4.7–<5.8μm, >5.8–<9.0μm and >9μm–<10μm) of PM10 atmospheric aerosols collected by six stages Anderson Cascade Impactor were determined using conductivity suppressed ion-chromatography system. Suspended particulate matters in the form of respirable (PM10) aerosols were collected on the roof of a three storied building at a height of 20m above the ground, at Bhabha Atomic Research Centre (BARC), Mumbai using Hi-Volume Sampler (HVS) with Whatman glass fiber filter paper during the period of March–June 2009. The sequence of solubility of ions in both extractants (acid+water) of PM10 aerosols from greatest to least was found to be Na+>Ca++>K+>Cl−>F−>Mg++>NO3−≈SO4−−. The average concentration of Na+, K+, Mg++, Ca++, F−, Cl−, NO3− and SO4−− in PM10 aerosols was estimated to be 13.36g/kg, 3.76g/kg,0.251g/kg,3.771g/kg,0.833g/kg,1.17g/kg, 81μg/kg and 290μg/kg respectively. The enrichment of particular ion in soluble components may be due to its high abundance in PM10 aerosols, less sorptivity with the tiny solid particles of atmospheric dust, high extractability and leachability, high solubility and mobility. By classifying the PM10 aerosols into two categories viz fine particle (<2.5μm) and coarse particle (>2.5μm–<10μm), it was found that generally, in the fine particle, the geometric mean concentration of total soluble ions in acid and water components was found to be higher than coarse particle. Overall, it was also observed that generally as particle size increases, the geometric mean concentration of soluble ions in both extractants of PM10 aerosols decreases.

IDENTIFICATION OF SOME CARCINOGENIC POLYCYCLIC AROMATIC HYDROCARBONS IN BANGLADESHI VEHICLES EXHAUST TAR BY GAS CHROMATOGRAPHY-MASS SPECTROPHOTOMETER

A more sensitive GC-MS method has been established for the determination of some carcinogenic polycyclic aromatic hydrocarbons (PAHs) in vehicles exhaust tar samples. The tar samples were extracted using dichloromethane (DMC): n-hexane solvent mixture. A multi-layer clean-up (silica gel/sodium sulphate) column was used, followed by glass fiber filter (GFF) paper. The method was successfully applied to determine a number of PAHs present in exhaust tar sample of different vehicles of the Atomic Energy Centre, Dhaka, Bangladesh. Keywords: Carcinogenic polycyclic aromatic hydrocarbons, vehicles tar samples, identification, GC-MS/MS

Aerosol size distribution in a uranium processing and fuel fabrication facility

In the nuclear fuel complex, magnesium diuranate is processed to produce UO(2) through different chemical and metallurgical processes. UO(2) powder is compacted to produce uranium pallets as fuel. International Commission on Radiological Protection has considered default particle size of 5-mum activity median aerodynamic diameter (AMAD) and 2.5 of geometric standard deviation (GSD) for working out dose coefficients. There is a likelihood of variation in the particle size during each stage of operation. The present study is undertaken to determine the prevailing uranium aerosol size distribution at every stage of operation using Anderson impactor with glass fibre filter paper as collection substrate. AMAD and respective GSD were determined. Aerosol size distribution was studied. Airborne uranium concentration was found to be higher for higher particle sizes in all areas. Average AMAD for different locations varied from 5.8 to 7.7 mum with GSD from 1.63 to 6.73 and the ratio of calculated ALI to standard varies from 1.13 to 1.55.

Measuring Submicron-Size Fractionated Particulate Matter on Aluminum Impactor Disks

Sub-micron sized airborne particulate matter (PM) is not collected well on regular quartz or glass fiber filter papers. We used a micro-orifice uniform deposit impactor (MOUDI) to fractionate PM into six size fractions and deposit it on specially designed high purity thin aluminum disks. The MOUDI separated PM into fractions 56-100 nm, 100-180 nm, 180-320 nm, 320-560 nm, 560-1000 nm, and 1000-1800 nm. Since the MOUDI has a low flow rate (30 L/min), it takes several days to collect sufficient carbon on 47 mm foil disks. The small carbon mass (20-200 microgram C) and large aluminum substrate (~25 mg Al) present several challenges to production of graphite targets for accelerator mass spectrometry (AMS) analysis. The Al foil consumes large amounts of oxygen as it is heated and tends to melt into quartz combustion tubes, causing gas leaks. We describe sample processing techniques to reliably produce graphitic targets for (14)C-AMS analysis of PM deposited on Al impact foils.

Disease-causing Mutation in GPR54 Reveals the Importance of the Second Intracellular Loop for Class A G-protein-coupled Receptor Function

The G-protein-coupled receptor (GPCR) GPR54 is essential for the development and maintenance of reproductive function in mammals. A point mutation (L148S) in the second intracellular loop (IL2) of GPR54 causes idiopathic hypogonadotropic hypogonadism, a disorder characterized by delayed puberty and infertility. Here, we characterize the molecular mechanism by which the L148S mutation causes disease and address the role of IL2 in Class A GPCR function. Biochemical, immunocytochemical, and pharmacological analysis demonstrates that the mutation does not affect the expression, ligand binding properties, or protein interaction network of GPR54. In contrast, diverse GPR54 functional responses are markedly inhibited by the L148S mutation. Importantly, the leucine residue at this position is highly conserved among class A GPCRs. Indeed, mutating the corresponding leucine of the alpha(1A)-AR recapitulates the effects observed with L148S GPR54, suggesting the critical importance of this hydrophobic IL2 residue for Class A GPCR functional coupling. Interestingly, co-immunoprecipitation studies indicate that L148S does not hinder the association of Galpha subunits with GPR54. However, fluorescence resonance energy transfer analysis strongly suggests that L148S impairs the ligand-induced catalytic activation of Galpha. Combining our data with a predictive Class A GPCR/Galpha model suggests that IL2 domains contain a conserved hydrophobic motif that, upon agonist stimulation, might stabilize the switch II region of Galpha. Such an interaction could promote opening of switch II of Galpha to facilitate GDP-GTP exchange and coupling to downstream signaling responses. Importantly, mutations that disrupt this key hydrophobic interface can manifest as human disease.