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PubMed1996

Partial characterization of the genome of nine animal caliciviruses.

Caliciviruses (CVs) include at least 42 distinct serotypes. Seventeen CV serotypes have been isolated from marine sources and are called San Miguel sea lion caliciviruses (SMSVs). CVs also have been isolated from reptiles, primates, and other terrestrial animals. Nucleotide sequences from portions of genome of prototype strains for six SMSV serotypes, the reptile CV, Cro-1, the cetacean CV, Tur-1, and the primate CV, Pan-1, are presented. cDNA products of the polymerase (all strains characterized) and capsid (SMSV-17) regions were produced by reverse transcription-polymerase chain reaction using Pan-1 primers. Comparisons of nucleotide and amino acid identity among these and published CV sequences indicated that the nine characterized CVs fall into a phylogenetic group that includes SMSV-1 and SMSV-4 and that is more closely related to other characterized animal CVs than to most human CVs. The phylogenetic analysis also indicated that distinct genera exist among the Caliciviridae. SMSV-17 and SMSV-4 are predicted to be closer to each other than other caliciviruses of known serotype; 574 (82%) of the 704 amino acids in the SMSV-17 and SMSV-4 capsid genes were identical.

Amino Acid Sequence↗

PubMed1991

Tissue characterization with intra-arterial ultrasound: special promise and problems.

Although we are able to identify many tissue types based on the screen image in intravascular ultrasound, there is additional information in the ultrasound signal which could be of assistance in characterization and identification of tissue. Intravascular ultrasound has several special characteristics which affect tissue characterization. These include the high transducer frequency, small transducers, short and relatively uniform path to the tissue, and limited tissue types to identify. These characteristics influence the results obtained by absolute backscatter, local statistics, frequency dependent backscatter, and angle dependency of backscatter. These effects are both positive and negative, and in many cases can be observed in clinical imaging. Another area of tissue characterization which can be performed with ultrasound is measurement of arterial wall elasticity. This can be of importance in the evaluation of mechanisms of dilatation, and the potential for complications.

Arteries↗

PubMed1987

Purification and characterization of the voltage-dependent anion channel from the outer mitochondrial membrane of yeast.

The outer mitochondrial membranes of all organisms so far examined contain a protein which forms voltage-dependent anion selective channels (VDAC) when incorporated into planar phospholipid membranes. Previous reports have suggested that the yeast (Saccharomyces cerevisiae) outer mitochondrial membrane component responsible for channel formation is a protein of 29,000 daltons which is also the major component of this membrane. In this report, we describe the purification of this 29,000-dalton protein to virtual homogeneity from yeast outer mitochondrial membranes. The purified protein readily incorporates into planar phospholipid membranes to produce ionic channels. Electrophysiological characterization of these channels has demonstrated they have a size, selectivity and voltage dependence similar to VDAC from other organisms. Biochemically, the purified protein has been characterized by determining its amino acid composition and isoelectric point (pI). In addition, we have shown that the purified protein, when reconstituted into liposomes, can bind hexokinase in a glucose-6-phosphate dependent manner, as has been shown for VDAC purified from other sources. Since physiological characterization suggests that the functional parameters of this protein have been conserved, antibodies specific to yeast VDAC have been used to assess antigenic conservation among mitochondrial proteins from a wide number of species. These experiments have shown that yeast VDAC antibodies will recognize single mitochondrial proteins from Drosophila, Dictyostelium and Neurospora of the appropriate molecular weight to be VDAC from these organisms. No reaction was seen to any mitochondrial protein from rat liver, rainbow trout, Paramecium, or mung bean. In addition, yeast VDAC antibodies will recognize a 50-kDa mol wt protein present in tobacco chloroplasts.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗

PubMed1994

Inclusion of synthetic DNA templates of similar length and base composition to PCR-amplified products in restriction enzyme digestions: an efficient aid in characterization of point mutations.

Because of a subtle anomaly we encountered upon an analytical gel while characterizing a point mutation in an exon of a patient, we decided to perform expensive and time-consuming procedures to characterize the anomaly. Although initial and subsequent Southern blots and PCR analyses of this patient's mutation suggested that his mutation lay directly within a TaqI recognition site, further characterization revealed that the mutation actually lay in a base immediately outside the recognition site. Had we included an appropriate double-stranded DNA control in the restriction enzyme digestion of this patient's PCR-amplified exon, we could have arrived at the correct conclusion as to the location of the mutation without incurring high costs and time loss. This brief report depicts the use of DNA controls of appropriate length and base composition as a means of avoiding erroneous conclusions and expense in routine mutational analyses in the clinical setting.

Alleles↗

PubMed1996

Characterization of oleoyl-12-hydroxylase in castor microsomes using the putative substrate, 1-acyl-2-oleoyl-sn-glycero-3-phosphocholine.

We have characterized the oleoyl-12-hydroxylase in the microsomal fraction of immature castor bean using the putative substrate, 1-acyl-2-oleoyl-sn-glycero-3-phosphocholine (2-oleoyl-PC). Previous characterizations of this enzyme used oleoyl-CoA as substrate and relied on the enzyme transferring oleate from oleoyl-CoA to lysophosphatidylcholine to form 2-oleoyl-PC (acyl-CoA:lysophosphatidylcholine acyltransferase) in addition to oleoyl-12-hydroxylase. The present assay system and characterization use 2-oleoyl-PC as substrate (oleoyl-12-hydroxylase alone). Use of the actual substrate for assay purposes is important for the eventual purification of the oleoyl-12-hydroxylase. Ricinoleate (product of oleoyl-12-hydroxylase) and linoleate (product of oleoyl-12-desaturase) were identified as metabolites of oleate of 2-oleoyl-PC by high-performance liquid chromatography and gas chromatography/mass spectrometry. The activity of oleoyl-12-hydroxylase in the microsomal fraction reached a peak about 44 d after anthesis of castor, while the activity of oleoyl-12-desaturase reached a peak about 23 d after anthesis. The optimal temperature for the oleoyl-12-hydroxylase was about 22.5 degrees C, and the optimal pH was 6.3. Catalase stimulated oleoyl-12-hydroxylase while bovine serum albumin and CoA did not activate oleoyl-12-hydroxylase. The phosphatidylcholine analogue, oleoyloxyethyl phosphocholine, inhibited the activity of oleoyl-12-hydroxylase. These results further support the hypothesis that the actual substrate of oleoyl-12-hydroxylase is 2-oleoyl-PC.

Adenosine Triphosphate↗

PubMed1989

Characterization of porcine omental lipids.

Porcine omental lipid extracts were fractionated and the major lipid components characterized. Approximately 97% of the chloroform/methanol extract consisted of triglycerides containing primarily 16:0, 18:0, 18:1, and 18:2 fatty acids. Small quantities of free fatty acids, cholesterol, di- and monoglycerides were also detected. The phospholipid fraction, obtained by solvent partition and Unisil column chromatography and characterized by high performance liquid chromatography (HPLC) and HPLC-mass spectrometry, was found to consist primarily of phosphatidylcholine, sphingomyelin, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol. The neutral glycolipids, isolated by solvent partition and Unisil column chromatography and identified by HPTLC and HPLC, were found to consist primarily of di-, tri- and tetraosylceramides. The complex glycolipid fraction, obtained from Folch upper phase solvent partition and characterized by HPTLC and immunoblotting, was found to consist primarily of ganglio-, globo-, and neolacto- neutral glycolipids and ganglio-, globo-, neolacto- and fucosylated gangliosides.

Animals↗

PubMed1993

Molecular cloning and characterization of receptors for the mammalian bombesin-like peptides.

The bombesin-like peptides comprise a large family of peptides common to both amphibians and mammals that function as growth factors, neurotransmitters, and paracrine hormones. GRP, the mammalian homolog of bombesin and its receptor, as well as NMB, the mammalian homolog of ranatensin, are expressed in human neoplasms and, in particular, in small cell lung carcinomas (SCLC). To better characterize the physiological roles of bombesin-like peptides, our laboratory has cloned the receptors for GRP in murines, rats, and humans. The 3T3 GRP receptor was isolated and characterized using the two-electrode-voltage-clamp analysis and acquorin-emission methods in xenopus oocytes expression system. The rat and human GRP and NMB receptors were cloned by hybridization at low stringency, using the mouse cDNA receptor probe. Sequence analysis of the receptors showed 384 and 390 amino acids for GRP and NMB receptors, respectively. The homology between the two receptors is 60% and between species in the same receptor, 90%. The receptors belong to the 7-membrane spanning domains superfamily. The specific GRP-R antagonist blocked the response to bombesin in oocytes injected with GRP-R, but failed to do so in oocytes injected with NMB-R. The two receptors differ in their distribution of tissue expression. RNA blot and RNase protection analysis showed the same size of mRNA without alteration in the receptors. RT + PCR analysis performed on genomic DNA revealed similarity between normal and cell DNAs, suggesting no major gene deletion or rearrangement. Southern blot analysis indicated the absence of gene amplification. Sequence analysis of the exonic segments of the receptor genes displayed identical amino acids to the respective cDNAs. None of the genes had classic TATAA box. Somatic cell hybrids localized the GRP-R on the X-chromosome and the NMB-R on chromosome 6. The same sequence of normal genes and cDNAs of GRP and NMB receptors, together with the gene characterization, demonstrated that SCLC cell lines do not require a structural change in receptor protein or genomic rearrangement.

3T3 Cells↗

PubMed1997

Insulin-like growth factor binding protein (IGFBP) substrate zymography. A new tool to identify and characterize IGFBP-degrading proteinases.

Insulin-like growth factor binding protein (IGFBP) degrading proteinase activities have been described in biological fluids and conditioned media from numerous cell lines. To identify and characterize IGFBP-degrading proteinases, our laboratory has developed IGFBP substrate zymography. Herein, we illustrate how IGFBP substrate zymography can be used both to identify candidate IGFBP-degrading proteinases and characterize their degradative capabilities. For this purpose, human matrix metalloproteinase-3 (MMP-3), a proteinase that degrades IGFBP-3 in human fibroblast cultures, was first electrophoresed through a polyacrylamide gel containing IGFBP-3 as substrate and then analyzed for its ability to degrade the substrate into immunoreactive fragments that were absorbed onto a polyvinylidene difluoride membrane. IGFBP-3 substrate zymography was capable of detecting as little as 20 ng of human MMP-3, demonstrating a sensitivity similar to casein substrate zymography. Using the zymogram as a template, MMP-3 was identified in a standard SDS-polyacrylamide gel run in parallel with the zymogram, and the corresponding area of the gel was excised. Electroelution of the gel slice yielded active MMP-3 when examined by casein substrate zymography. Furthermore, digestion of IGFBP-3 in solution by the electroeluted MMP-3 revealed the same fragmentation pattern of the binding protein as that produced by MMP-3, which had not been electroeluted. Together, these studies demonstrate that IGFBP substrate zymography can be a useful tool for both the identification and the characterization of IGFBP-degrading proteinases.

Caseins↗

PubMed2004

Using multimedia modeling to expedite site characterization.

GOAL, SCOPE AND BACKGROUND: This paper uses two case studies of U.S. Department of Energy nuclear weapons complex installations to illustrate the integration of expedited site characterization (ESC) and multimedia modeling in the remedial action decision making process. CONCEPTUAL SITE MODELS, MULTIMEDIA MODELS, AND EXPEDITED SITE CHARACTERIZATION: Conceptual site models outline assumptions about contaminates and the spatial/temporal distribution of potential receptors. Multimedia models simulate contaminant transport and fate through multiple environmental media, estimate potential human exposure via specific exposure pathways, and estimate the risk of cancer and non-cancer health outcomes. ESC relies on using monitoring data to quantify the key components of an initial conceptual site model that is modified iteratively using the multimedia model. CASE STUDIES: Two case studies are presented that used the ESC approach: Los Alamos National Laboratory (LANL) and Pantex. LANL released radionuclides, metals, and organic compounds, into canyons surrounding the facility. The Pantex Plant has past waste management operations which included burning chemical wastes in unlined pits, burying wastes in unlined landfills, and discharging plant wastewaters into on-site surface waters. CONCLUSIONS: The case studies indicate that using multimedia models with the ESC approach can inform assessors about what, where, and how much site characterization data needs to be collected to reduce the uncertainty associated with risk assessment. Lowering the degree of uncertainty reduces the time and cost associated with assessing potential risk and increases the confidence that decision makers have in the assessments performed.

Decision Making↗

PubMed2006

Molecular characterization of large deletions in the von Hippel-Lindau (VHL) gene by quantitative real-time PCR: the hypothesis of an alu-mediated mechanism underlying VHL gene rearrangements.

INTRODUCTION: Mutations of the von Hippel-Lindau (VHL) gene are responsible for VHL disease. This is a familial autosomal-dominant syndrome, predisposing to the development of benign and malignant tumors, including CNS and retinal hemangioblastomas, pheochromocytomas, and clear cell renal carcinomas. At least 30% of the disease-causing mutations in the VHL gene involve large alterations. Identification of these mutations is not possible using PCR-based mutational scanning methods. Quantitative Southern blot analysis has been traditionally employed for the detection of complete or partial deletions and more complex rearrangements of the gene. METHODS: An alternative quantitative method was developed using a combination of quantitative Southern blot analysis and real-time PCR. With this approach, we studied 24 large VHL gene alterations to determine the exact nature of the mutations and to possibly characterize the boundaries of the deleted regions. RESULTS: This combined molecular approach showed that all the VHL alterations studied were due to deletions, from which the position in the gene could be more precisely mapped. One of the samples that was completely characterized was found to carry an intragenic 2.2kb deletion with both 5' and 3' breakpoints located within Alu-repeat sequences. CONCLUSION: This is the first report on the molecular analysis of large VHL alterations. The results of our study and the complete characterization of a large deletion lead to the hypothesis that an Alu-mediated mechanism may be responsible for the common occurrence of large alterations in the VHL gene.

Alu Elements↗

PubMed1987

Characterization of high titer antithyroglobulin antibodies.

Few autoantibodies directed against thyroglobulin (TgAbs) have been fully characterized in man. The present study was designed to characterize TgAbs from patients with unusually high titers (greater than 1:5(12] using tanned red cell hemagglutination technique (TRC). IgG was isolated from the sera of subjects with Hashimoto's thyroiditis (n = 4), subacute thyroiditis (n = 1) and Graves' disease (n = 1) using DEAE-Sephacel chromatography. Isolated TgAbs were substituted as first antibody in a double antibody thyroglobulin (Tg) RIA and the Ka's were determined by Scatchard analysis. Molecular ratios of antibody to antigen, TgAb: Tg, were calculated from quantitative precipitin curves. The clonality of each antibody was determined using agarose isoelectric focusing and 131I labeled Tg as an autoradiographic probe. All six TgAbs were polyclonal. The Ka's were on the order of 10(9)-10(10). In two sera TgAb:Tg ratios of 20:1 and 8:1 were obtained. These results are significant when compared to previously characterized Tg autoantibodies which have been of low titer, low Ka (10(5], and have been directed towards a restricted portion of the Tg molecule (TgAb: Tg ratios of 2:1 to 6:1). In view of their high affinity constants and recognition of a less restricted portion of the Tg molecule, some of the TgAb's with unusually high titers behave more like Tg heteroantibodies than autoantibodies.

Antibodies↗

PubMed1998

Comparative pharmacology of human adenosine receptor subtypes - characterization of stably transfected receptors in CHO cells.

Four adenosine receptor subtypes of the family of G protein-coupled receptors, designated A1, A2A, A2B and A3 are currently known. In this study all human subtypes were stably transfected into Chinese hamster ovary (CHO) cells in order to be able to study their pharmacological profile in an identical cellular background utilizing radioligand binding studies (A1, A2A, A3) or adenylyl cyclase activity assays (A2B). The A1 subtype showed the typical pharmacological profile with 2-chloro-N6-cyclopentyladenosine (CCPA) as the agonist with the highest affinity and a marked stereoselectivity for the N6-phenylisopropyladenosine (PIA) diastereomers. In competition with antagonist radioligand biphasic curves were observed for agonists. In the presence of GTP all receptors were converted to a single low affinity state indicating functional coupling to endogenous G proteins. For A2A adenosine receptors CGS 21680 (2-[p-(2-carboxyethyl)phenylethylamino]-5'-N-ethylcarboxamidoadeno sine) and N-ethylcarboxamidoadenosine (NECA) were found to be the most potent agonists followed by R- and S-PIA with minor stereoselectivity. The relative potencies of agonists for the A2B adenosine receptor could only be tested by measurement of receptor-stimulated adenylyl cyclase activity. NECA was the most potent agonist with an EC50-value of 2.3 microM whereas all other compounds tested were active at concentrations in the high micromolar range. Inhibition of NECA-stimulated adenylyl cyclase identified xanthine amino congener (XAC; 8-[4-[[[[(2-aminoethyl)amino]-carbonyl]methyl]oxy]phenyl]-1,3-dipropylxa nthine) as the most potent antagonist at this receptor subtype. The A3 receptor was characterized utilizing the nonselective agonist [3H]NECA. The N6-benzyl substituted derivatives of adenosine-5'-N-methyluronamide (MECA) turned out to be the most potent agonists. The notion of xanthine-insensitivity of the A3 receptor should be dropped at least for the human receptor as xanthines with submicromolar affinity were found. Overall, the pharmacological characteristics of the human receptors are similar to other species with some species-specific characteristics. In this study we present for the first time the comparative pharmacology of all known human adenosine receptor subtypes. The CHO cells with stably transfected adenosine receptors provide an identical cellular background for such a pharmacological characterization. These cells are valuable systems for further characterization of specific receptor subtypes and for the development of new ligands.

Adenosine↗

PubMed1998

Molecular characterization and delineation of subtle deletions in de novo "balanced" chromosomal rearrangements.

To test the hypothesis that the phenotypic abnormalities seen in cases with apparently balanced chromosomal rearrangements are the result of the presence of cryptic deletions or duplications of chromosomal material near the breakpoints, we analyzed three cases with apparently balanced chromosomal rearrangements and phenotypic abnormalities. We characterized the breakpoints in these cases by using microsatellite analysis by polymerase chain reaction and fluorescence in situ hybridization analysis of yeast artificial chromosome clones selected from the breakpoint regions. Molecular characterization of the translocation breakpoint in patient 1 [46,XY,t(2;6)(p22.2;q23.1)] showed the presence of a 4- to 6-Mb cryptic deletion between markers D6S412 and D6S1705 near the 6q23.1 breakpoint. Molecular characterization of the proximal inversion 7q22.1 breakpoint in patient 2 [46,XY,inv(7)(q22.1q32.1)] revealed the presence of a 4-Mb cryptic deletion between D7S651 and D7S515 markers. No deletion or duplication of chromosomal material was found near the breakpoints in patient 3 [46,XX,t(2;6)(q33.1;p12.2)]. Our study suggests that a systematic molecular study of breakpoints should be carried out in cases with apparently balanced chromosomal rearrangements and phenotypic abnormalities, because cryptic deletions near the breakpoints may explain the phenotypic abnormalities in these cases.

Abnormalities, Multiple↗

PubMed2001

Characterization of the human beta4 nAChR gene and polymorphisms in CHRNA3 and CHRNB4.

Most neuronal nicotinic acetylcholine receptors are heteropentamers, composed of alpha and beta subunits. Mice lacking the alpha3 subunit and mice lacking both the beta2 and beta4 subunits, but not mice lacking the beta2 or beta4 subunits alone, have a severe phenotype characterized by megacystis, failure of bladder strips to contract in response to nicotine, widely dilated ocular pupils, growth failure, and perinatal mortality. The deficit in bladder contraction was also found in mice lacking only the beta4 subunit, although they did not develop megacystis. The major bladder phenotype resembles the human autosomal recessive disorder of megacystis-microcolon-hypoperistalsis syndrome (MMIHS). Based on the similarity of the mouse and human phenotypes, we initiated mutation analyses in the alpha3 and beta4 genes in MMIHS families. The human gene encoding the beta4 subunit was fully characterized, including refinement of its mapping. Analysis of disease families and controls identified numerous genetic variants, including high-frequency polymorphisms in both CHRNA3 and CHRNB4. Although no loss-of-function mutations have been identified to date, these genes remain strong candidates for involvement in MMIHS, because various mutations might be obscured within the complex cluster of genes. Some of the markers presented here are valuable tools for analysis of the role of genetic variation in responses to nicotine and for characterization of various dysautonomic abnormalities.

Autonomic Nervous System Diseases↗

PubMed2005

Molecular and biochemical characterization of puroindoline a and b alleles in Chinese landraces and historical cultivars.

Kernel hardness that is conditioned by puroindoline genes has a profound effect on milling, baking and end-use quality of bread wheat. In this study, 219 landraces and 166 historical cultivars from China and 12 introduced wheats were investigated for their kernel hardness and puroindoline alleles, using molecular and biochemical markers. The results indicated that frequencies of soft, mixed and hard genotypes were 42.7, 24.3, and 33.0%, respectively, in Chinese landraces and 45.2, 13.9, and 40.9% in historical cultivars. The frequencies of PINA null, Pinb-D1b and Pinb-D1p genotypes were 43.8, 12.3, and 39.7%, respectively, in hard wheat of landraces, while 48.5, 36.8, and 14.7%, respectively, in historical hard wheats. A new Pinb-D1 allele, designated Pinb-D1t, was identified in two landraces, Guangtouxianmai and Hongmai from the Guizhou province, with the characterization of a glycine to arginine substitution at position 47 in the coding region of Pinb gene. Surprisingly, a new Pina-D1 allele, designated Pina-D1m, was detected in the landrace Hongheshang, from the Jiangsu province, with the characterization of a proline to serine substitution at position 35 in the coding region of Pina gene; it was the first novel mutation found in bread wheat, resulting in a hard endosperm with PINA expression. Among the PINA null genotypes, an allele designed as Pina-D1l, was detected in five landraces with a cytosine deletion at position 265 in Pina locus; while another novel Pina-D1 allele, designed as Pina-D1n, was identified in six landraces, with the characterization of an amino acid change from tryptophan-43 to a 'stop' codon in the coding region of Pina gene. The study of puroindoline polymorphism in Chinese wheat germplasm could provide useful information for the further understanding of the molecular basis of kernel hardness in bread wheat.

Alleles↗

PubMed2002

Hyphenated techniques for the characterization and quantification of metallothionein isoforms.

Recent developments in the coupling of highly selective separation techniques such as capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) to element-specific and molecule-specific detectors, such as inductively-coupled plasma mass spectrometry (ICP-MS) and electrospray ionization-tandem mass spectrometry (ESI-MS/MS) for the characterization and quantification of metallothioneins (MTs) are critically reviewed and discussed. This review gives an update based on the literature over the last five years. The coupling of CE to ICP-MS is especially highlighted. As a result of progress in new interface technologies for CE-ICP-MS, research topics presented in the literature are changing from "the characterization of interfaces by metallothioneins" to the "characterization of metallothioneins by CE-ICP-MS". New applications of CE-ICP-MS to the analysis of MTs in real samples are summarized. The potential of the on-line isotope dilution technique for the quantification of MTs and for the determination of the stoichiometric composition of metalloprotein complexes is discussed. Furthermore, a selection of relevant papers dealing with HPLC-ICP-MS for MT analysis are summarized and compared to those dealing with CE-ICP-MS. In particular, the use of size-exclusion (SE)-HPLC as a preliminary separation step for metallothioneins in real samples prior to further chromatographic or electrophoretic separations is considered. Additionally, the application of electrospray ionisation-tandem mass spectrometry (ESI-MS/MS) for the identification of metallothionein isoforms following electrophoretic or chromatographic separation is discussed.

Animals↗

PubMed2002

Characterization of thin polymer and biopolymer layers by ellipsometry and evanescent field technology.

The characterization of sensitive layers is the prerequisite for the optimization of chemical and biochemical sensors. The application of SE (Spectral Ellipsometry) and SPR (Surface Plasmon Resonance) as methods of characterization of such sensitive layers is discussed. In combination with infrared spectroscopy, the properties of polymer networks, micro-porous polymers, liquid crystals, and biomimetic polymers can be examined regarding their applicability for optical sensing. Apart from the basic principles regarding the characterization approaches, applications in the area of environmental sensing, optimization of hydrogel layers for antigen/antibody interaction, and discrimination of analytes in homologous series of alcohols are discussed. The effects of analytes on the phase transition in combination with disordering of liquid crystals are given.

Biopolymers↗

PubMed2003

Development and characterization of a mobile photoacoustic sensor for on-line soot emission monitoring in diesel exhaust gas.

Upcoming regulations for vehicle exhaust emission demand substantial reduction of particle emission in diesel exhaust. To achieve these emission levels, the car manufacturing industry is developing new combustion concepts and exhaust after-treatment techniques such as the use of catalysts and particle filters. Many of the state-of-the-art analytical instruments do not meet the required detection limits, in combination with a high temporal resolution necessary for engine optimization. This paper reports a new detection system and the first results of its application to on-line diesel exhaust soot measurements on a engine test bench (MAN diesel engine facility Nürnberg, Germany). The instrument is based on differential photoacoustic (PA) spectroscopy of black carbon aerosol. It contains two identical PA cells, one for the measurement of the aerosol particles and one which analyses the particle-free gas. Thus, a potential cross-sensitivity to gaseous absorbers in the exhaust gas can be excluded. The PA cells were characterized in a laboratory set-up, with water vapor as reference gas and artificial soot generated by a spark discharge generator. The detection limit was found to be 2 microg m(-3) BC (for diesel soot) with a sampling rate of 3 Hz. The temporal response of the system was found to be in the order of 1 s. After full characterization of the cells, the system was transferred into a mobile 19"-rack. Characterization of the mobile sensor system under real-world conditions was performed during several measurement campaigns at an engine test bench for heavy-duty diesel engines. Results for the limit of detection, the time resolution, accuracy, repeatability, and robustness of the sensor system are very promising with regards to a routine application of the system in engine development.

Journal Article↗