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  • 11
    Electronic Resource
    Electronic Resource
    Cystic fibrosis: typing 89 German families with linked DNA probes (1988)
    Springer
    Human genetics 〈Berlin〉 81 (1988), S. 54-56 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Three hundred and ninety-two subjects from 89 German families were typed for restriction fragment length polymorphisms (RFLPs) detected by the probes pmetH, pmetD, pJ3.11, KM19, and XV2c known to be tightly linked to the cystic fibrosis (CF) gene. The analysis of the predictive value of this typing in individual CF families indicates that the combined use of these probes provides a powerful diagnostic system for both carrier detection and prenatal diagnosis. In 45 families the complete haplotype including all RFLPs was available. Of them 41 (91.1%) were fully informative and 4 were partly informative.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00283729
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  • 12
    Electronic Resource
    Electronic Resource
    Geographic distribution and origin of CFTR mutations in Germany (1996)
    Springer
    Human genetics 〈Berlin〉 97 (1996), S. 727-731 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The geographic distribution and origin of CFTR mutations in Germany was evaluated in 658 three-generation families with cystic fibrosis (CF). Fifty different mutations were detected on 1305 parental CF chromosomes from 22 European countries and overseas. The major mutation ΔF508 was identified on 71.5% of all CF chromosomes, followed by R553X (1.8%), N1303K (1.3%), G542X (1.1%), G551D (0.8%) and R347P (0.8%). According to the grandparents’ birthplace, 74% of CF chromosomes had their origin in Germany; the ΔF508 percentage was 77%, 75%, 70% and 62% in northern, southern, western and eastern Germany, respectively. Ten or more mutant alleles in the investigated CF gene pool originated from Austria, the Czech Republic, Poland, Russia, Turkey and the Ukraine. This widespread geographic origin of CFTR mutations in today’s Germany reflects the many demographic changes and migrations in Central Europe during the 20th century.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004390050128
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  • 13
    Electronic Resource
    Electronic Resource
    Geographic distribution and origin of CFTR mutations in Germany (1996)
    Springer
    Human genetics 〈Berlin〉 97 (1996), S. 727-731 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The geographic distribution and origin of CFTR mutations in Germany was evaluated in 658 three-generation families with cystic fibrosis (CF). Fifty different mutations were detected on 1305 parental CF chromosomes from 22 European countries and overseas. The major mutation ΔF508 was identified on 71.5% of all CF chromosomes, followed by R553X (1.8%), N1303K (1.3%), G542X (1.1%), G551D (0.8%) and R347P (0.8%). According to the grandparents' birthplace, 74% of CF chromosomes had their origin in Germany; the ΔF508 percentage was 77%, 75%, 70% and 62% in northern, southern, western and eastern Germany, respectively. Ten or more mutant alleles in the investigated CF gene pool originated from Austria, the Czech Republic, Poland, Russia, Turkey and the Ukraine. This widespread geographic origin of CFTR mutations in today's Germany reflects the many demographic changes and migrations in Central Europe during the 20th century.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02346181
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  • 14
    Electronic Resource
    Electronic Resource
    Stripping dynamics in the reactions of electronically excited carbon atoms, C(1D), with ethylene and propylene—production of propargyl and methylpropargyl radicals (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 1318-1324 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reactions of electronically excited carbon atoms, C(1D), with ethylene and propylene were studied at three collision energies between 48 and 104 kJmol−1 employing the crossed molecular beam technique. Forward-convolution fitting of our data combined with electronic structure calculations suggests that the reactions proceed via stripping dynamics. Extremely short-lived allene and 1,2-butadiene intermediates decompose via atomic hydrogen emission to yield propargyl and methylpropargyl radicals, respectively. These production routes are of potential importance to form benzene, toluene, and o-/p-xylenes in circumstellar envelopes of carbon stars and combustion flames. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1428754
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  • 15
    Electronic Resource
    Electronic Resource
    A combined crossed beam and ab initio investigation on the reaction of carbon species with C4H6 isomers. I. The 1,3-butadiene molecule, H2CCHCHCH2(X1A′) (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 9622-9636 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction between ground state carbon atoms, C(3Pj), and 1,3-butadiene, H2CCHCHCH2, was studied at three averaged collision energies between 19.3 and 38.8 kJmol−1 using the crossed molecular beam technique. Our experimental data combined with electronic structure calculations show that the carbon atom adds barrierlessly to the π-orbital of the butadiene molecule via a loose, reactantlike transition state located at the centrifugal barrier. This process forms vinylcyclopropylidene which rotates in a plane almost perpendicular to the total angular momentum vector J around its C-axis. The initial collision complex undergoes ring opening to a long-lived vinyl-substituted triplet allene molecule. This complex shows three reaction pathways. Two distinct H atom loss channels form 1- and 3-vinylpropargyl radicals, HCCCHC2H3(X2A″) and H2CCCC2H3(X2A″), through tight exit transition states located about 20 kJmol−1 above the products; the branching ratio of 1- versus 3-vinylpropargyl radical is about 8:1. A minor channel of less than 10% is the formation of a vinyl, C2H3(X2A′), and propargyl radical C3H3(X2B2). The unambiguous identification of two C5H5 chain isomers under single collision has important implications to combustion processes and interstellar chemistry. Here, in denser media such as fuel flames and in circumstellar shells of carbon stars, the linear structures can undergo a collision-induced ring closure followed by a hydrogen migration to cyclic C5H5 isomers such as the cyclopentadienyl radical—a postulated intermediate in the formation of polycyclic aromatic hydrocarbons (PAHs). © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1290285
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  • 16
    Electronic Resource
    Electronic Resource
    Crossed beam reaction of cyano radicals with hydrocarbon molecules. IV. Chemical dynamics of cyanoacetylene (HCCCN; X 1Σ+) formation from reaction of CN(X 2Σ+) with acetylene, C2H2(X 1Σg+) (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 8656-8666 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The chemical reaction dynamics to form cyanoacetylene, HCCCN (X 1Σ+), via the radical–neutral reaction of cyano radicals, CN(X 2Σ+;ν=0), with acetylene, C2H2(X 1Σg+), are unraveled in crossed molecular beam experiments at two collision energies of 21.1 and 27.0 kJ mol−1. Laboratory angular distributions and time-of-flight spectra of the HCCCN product are recorded at m/e=51 and 50. Experiments were supplemented by electronic structure calculations on the doublet C3H2N potential energy surface and RRKM investigations. Forward-convolution fitting of the crossed beam data combined with our theoretical investigations shows that the reaction has no entrance barrier and is initiated by an attack of the CN radical to the π electron density of the acetylene molecule to form a doublet cis/trans HCCHCN collision complex on the 2A′ surface via indirect reactive scattering dynamics. Here 85% of the collision complexes undergo C–H bond rupture through a tight transition state located 22 kJ mol−1 above the cyanoacetylene, HCCCN (X 1Σ+) and H(2S1/2) products (microchannel 1). To a minor amount (15%) trans HCCHCN shows a 1,2-H shift via a 177 kJ mol−1 barrier to form a doublet H2CCCN radical, which is 46 kJ mol−1 more stable than the initial reaction intermediate (microchannel 2). The H2CCCN complex decomposes via a rather loose exit transition state situated only 7 kJ mol−1 above the reaction products HCCCN (X 1Σ+) and H(2S1/2). In both cases the geometry of the exit transition states is reflected in the observed center-of-mass angular distributions showing a mild forward/sideways peaking. The explicit identification of the cyanoacetylene as the only reaction product represents a solid background for the title reaction to be included in reaction networks modeling the chemistry in dark, molecular clouds, outflow of dying carbon stars, hot molecular cores, as well as the atmosphere of hydrocarbon rich planets and satellites such as the Saturnian moon Titan. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1289530
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  • 17
    Electronic Resource
    Electronic Resource
    Crossed beam reaction of phenyl radicals with unsaturated hydrocarbon molecules. I. Chemical dynamics of phenylmethylacetylene (C6H5CCCH3;X 1A′) formation from reaction of C6H5(X 2A1) with methylacetylene, CH3CCH(X 1A1) (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 4994-5001 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The chemical reaction dynamics to form phenylmethylacetylene, C6H5CCCH3(X 1A′), via reactive collisions of the phenyl radical C6H5(X 2A1) with methylacetylene, CH3CCH(X 1A1), are unraveled under single collision conditions in a crossed molecular beam experiment at a collision energy of 140 kJ mol−1. The laboratory angular distribution and time-of-flight spectra of C9H8+ at m/e=116 indicate the existence of a phenyl radical versus hydrogen replacement pathway. Partially deuterated methylacetylene, CH3CCD(X 1A1), was used to identify the site of the carbon–hydrogen bond cleavage. Only the loss of the acetylenic hydrogen atom was observed; the methyl group is conserved in the reaction. Electronic structure calculations reveal that the reaction has an entrance barrier of about 17 kJ mol−1. Forward-convolution fitting of our data shows that the chemical reaction dynamics are on the boundary between an osculating complex and a direct reaction and are governed by an initial attack of the C6H5 radical to the π electron density of the C1 carbon atom of the methylacetylene molecule to form a short lived, highly rovibrationally excited (C6H5)HCCCH3 intermediate. The latter loses a hydrogen atom to form the phenylmethylacetylene molecule on the 2A′ surface. The phenylallene isomer channel was not observed experimentally. The dynamics of the title reaction and the identification of the phenyl versus hydrogen exchange have a profound impact on combustion chemistry and chemical processes in outflows of carbon stars. For the first time, the reaction of phenyl radicals with acetylene and/or substituted acetylene is inferred experimentally as a feasible, possibly elementary reaction in the stepwise growth of polycyclic aromatic hydrocarbon precursor molecules and alkyl substituted species in high temperature environments such as photospheres of carbon stars and oxygen poor combustion systems. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481054
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  • 18
    Electronic Resource
    Electronic Resource
    Chemical dynamics of cyclopropynylidyne (c-C3H; X2B2) formation from the reaction of C(1D) with acetylene, C2H2(X 1Σg+) (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 231-239 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction between electronically excited carbon atoms, C(1D), and acetylene was studied at two average collision energies of 45 kJ mol−1 and 109 kJ mol−1 employing the crossed molecular beam technique. The time-of-flight spectra recorded at mass to charge m/e=37(C3H+) and m/e=36(C3+) show identical patterns indicating the existence of a carbon versus atomic hydrogen exchange pathway to form C3H isomer(s); no H2 elimination to the thermodynamically favorable tricarbon channel was observed. Forward-convolution fitting of our data shows that the reaction proceeds via direct stripping dynamics on the 1A′ surface via an addition of the carbon atom to the π-orbital of acetylene to form a highly rovibrationally, short lived cyclopropenylidene intermediate which decomposes by atomic hydrogen emission to c-C3H(X 2B2). The dynamics of this reaction have important impact on modeling of chemical processes in atmospheres of comets approaching the perihelon as photolytically generated C(1D) atoms are present. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1330232
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  • 19
    Electronic Resource
    Electronic Resource
    Crossed beam reaction of the cyano radical, CN(X 2Σ+), with methylacetylene, CH3CCH (X 1A1): Observation of cyanopropyne, CH3CCCN (X 1A1), and cyanoallene, H2CCCHCN (X 1A′) (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 2857-2860 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The chemical dynamics to form cyanopropyne, CH3CCCN (X 1A1), and cyanoallene, H2CCCHCN (X 1A′), via the neutral–neutral reaction of the cyano radical, CN (X 2Σ+), with methylacetylene, CH3CCH (X 1A1), is investigated under single collision conditions in a crossed molecular beam experiment at a collision energy of 24.7 kJ mol−1. The laboratory angular distribution and time-of-flight spectra of the C4H3N products are recorded at m/e=65, 64, 63, and 62. The reaction of d3-methylacetylene, CD3CCH (X 1A1), with CN radicals yields reactive scattering signal at m/e=68 and m/e=67 demonstrating that two distinct H(D) atom loss channels are open. Forward-convolution fitting of the laboratory data reveal that the reaction dynamics are indirect and governed by an initial attack of the CN radical to the π electron density of the β carbon atom of the methylacetylene molecule to form a long lived CH3CCHCN collision complex. The latter decomposes via two channels, i.e., H atom loss from the CH3 group to yield cyanoallene, and H atom loss from the acetylenic carbon atom to form cyanopropyne. The explicit identification of the CN vs H exchange channel and two distinct product isomers cyanoallene and cyanopropyne strongly suggests the title reaction as a potential route to form these isomers in dark molecular clouds, the outflow of dying carbon stars, hot molecular cores, as well as the atmosphere of hydrocarbon rich planets and satellites such as the Saturnian moon Titan. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479567
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  • 20
    Electronic Resource
    Electronic Resource
    Chemical dynamics of d1-methyldiacetylene (CH3CCCCD; X 1A1) and d1-ethynylallene (H2CCCH(C2D); X 1A′) formation from reaction of C2D(X 2Σ+) with methylacetylene, CH3CCH(X 1A1) (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 3488-3496 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The crossed beam reaction of the d1-ethynyl radical C2D(X 2Σ+), with methylacetylene, CH3CCH(X 1A1), was investigated at an average collision energy of 39.8 kJ mol−1. Our experimental results were combined with electronic structure calculations. The chemical reaction dynamics are indirect, involve three distinct channels, and are initiated via a barrierless addition of C2D to the acetylenic bond through long lived cis and trans CH3CCH(C2D), 1-ethynylpropen-2-yl, intermediates. The reduced cone of acceptance of the carbon atom holding the methyl group favors a carbon–carbon σ bond formation at the carbon atom adjacent to the acetylenic hydrogen atom. A crossed beam experiment of C2D with partially deuterated methylacetylene, CD3CCH, shows explicitly that the reactive intermediates decompose to form both methyldiacetylene, CD3CCCCD (channel 1, 70%–90%), and to a minor amount ethynylallene, D2CCCH(C2D) (channel 2; 10%–30%), isomers through exit transition states located 7–15 kJ mol−1 above the products. The computed reaction energies to form both isomers are −135 and −107 kJ mol−1, respectively, with respect to the separated reactants. A minor reaction pathway involves a H shift in CH3CCH(C2D) to an 1-ethynylpropen-1-yl radical which fragments to methyldiacetylene via a barrier of 8.8 kJ mol−1 (channel 3). Neither methyl group elimination nor the formation of the CC(CH3)(C2D) carbene was observed in our experiments. The experimentally observed "sideways scattering" and ab initio investigation verify our conclusions of a predominate formation of the methyldiacetylene isomer. These electronic structure calculations depict a hydrogen atom loss in the exit transition state to methyldiacetylene almost parallel to the total angular momentum vector J as found in our center-of-mass angular distribution. Since the title reaction and the corresponding reaction of the C2H radical with CH3CCH both have no entrance barriers, are exothermic, and all the involved transition states are located well below the energy of the separated reactants, the assignment of the ethynyl versus H atom exchange suggests the formation of both isomers under single collision conditions in extraterrestrial environments such as cold, molecular clouds as well as the atmosphere of Saturn's moon Titan. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1330233
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