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Flavins were extracted from sporangiophores of the lower fungus Phycomyces blakesleeanus and identified by HPLC with fluorescence detection. In the wild-type strain NRRL1555 they were found to be present at the following concentrations: riboflavin (5.5 x 10(-6) M), flavin mononucleotide (FMN) (4.0 x 10(-6) M) and flavin adenine dinucleotide (1.4 x 10(-6) M). The HPLC elution profiles of the wild type were compared to a set of behavioral mutants (genotype mad) with specific defects in their light-transduction pathway. The photoreceptor mutants C109 (madB), C111 (madB) and L1 (madC) had normal amounts of flavins. The most prominent changes were found in single mutants with a defective madA gene which contained about 25% of riboflavin and about 10% of FMN and FAD normally found in the wild type. A hypertropic mutant with a defective madH gene contained instead 80% of riboflavin and 120% of FMN and FAD. The double mutant L52 (madA madC) and the triple mutant L72 (madA madB madC) had normal amounts of FAD and FMN. This indicates that the madC mutation, which itself causes loss of light sensitivity and which affects the near-UV/blue-light receptor (Galland and Lipson, 1985, Photochem. Photobiol. 41, 331-335) functions as a restorer of the flavin content in a genetic madA background. The double mutant L51 (madA madB) had about 40% of FMN and FAD, suggesting that the madB mutation functions as a partial restorer of flavin content. The photogravitropic thresholds (450 nm) reported for the wild type and the madA and madH mutants were positively correlated to the endogeneous concentrations of FMN and FAD.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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Two headspace-methods were developed for the detection and determination of traces of CFC/HCFC in polymeric foams. These methods consist of capillary gas chromatography using an electron-capture detector (ECD method) or an ion trap detector combined with preconcentration on a cold trap (ITD method). Different CFC/HCFC such as R115, R22, R12, R142b, R114, R11, R141b and R113 were investigated in polyethylene and flexible polyurethane foams. Conditions for sample preparation (e.g. thermostating time and temperature) were optimized. Determination of the detection limits and quantitation of the amount of CFC/HCFC released from the foam were performed with gas standards prepared with the help of mass flow controllers. Quantitative analyses of the total amount of CFC/HCFC present in the foam were performed using multiple headspace extraction. Longterm studies were performed on the rate of release of some CFC/HCFC from the foams. Additionally a method for distinguishing a CFC/HCFC-contaminated foam from an old CFC/HCFC-blown foam is presented. Both methods can be used individually; however, best results are achieved by using the ECD method for screening and the ITD method for confirmation. This combination was used for routine analysis enforcing legal restrictions on the use of CFC/HCFC in foams.Abbreviations CFC
chlorofluorocarbon
- HCFC
partially halogenated chlorofluorohydrocarbon
- PUR
polyurethane
- PS
polystyrene
- PE
polyethylene
- MHE
multiple headspace extraction
- ECD
electron capture detector
- ITD
ion trap detector
- FID
flame ionization detector
- TCD
thermal conductivity detector
- MS
mass spectrometry
- WCOT
wall coated, open tubular (column)
- ppm
parts per million (1:106 v/v)
- ppb
parts per billion (1:109 v/v)
- ppt
parts per trillion (1:1012 v/v)
- DL
detection limit
- RSD
relative standard deviation
- CO2
carbon dioxide
- R115
C2ClF5
- R22
CHClF2
- R12
CCl2F2
- R142b
C2H3ClF2
- R114
C2Cl2F4
- R11
CCl3F
- R141b
C2H3ClF
- R113
C2Cl3F3 相似文献
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A. Vollrath T. Otz C. Hohl H. G. Seiler 《Fresenius' Journal of Analytical Chemistry》1992,344(6):269-274
Summary A microwave digestion procedure and an oxygen flask combustion procedure were developed for the determination of cadmium and lead in plastic materials. A comparison with conventional wet ashing shows acceptable agreement. Different types of plastics such as polyvinylchloride, polypropylene, polyethylene, polystyrene, polyamide, and polyethyleneterephthalate were investigated. The precision of microwave digestion was determined within a series and from day to day. The results obtained by flame atomic absorption spectrometry were verified by measurement with inverse voltammetry. Overall, microwave digestion as well as oxygen flask combustion are time saving and cost-effective dissolution procedures to supervise the legal cadmium limit in plastics.Abbreviations FAAS
Flame atomic absorption spectrometry
- GFAAS
Graphite furnace atomic absorption spectometry
- ICPMS
Inductively coupled plasma mass spectrometry
- PVC
Polyvinylchloride
- PP
Polypropylene
- PE
Polyethylene
- PS
Polystyrene
- PET
Polyethyleneterephthalate
- PA
Polyamide 6.6
- PTFE-TFM
Polytetrafluoroethylene-tetrafluoromethoxylate
- HMDE
Hanging mercury drop electrode
- MS
Mass spectrometry
- OFC
Oxygen flask combustion
- MWD
Microwave digestion
- CWA
Conventional wet ashing
- DL
Detection limit
- QL
Quantification limit 相似文献
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A. Hohl T. Wieder P. A. van Aken T. E. Weirich G. Denninger M. Vidal S. Oswald C. Deneke J. Mayer H. Fuess 《Journal of Non》2003,320(1-3):255-280
The present state of research on the structure of amorphous silicon monoxide (SiO) is reviewed. The black, coal-like modification of bulk SiO is studied by a combination of diffraction, microscopy, spectroscopy, and magnetometry methods. Partial radial distribution functions of SiO are obtained by X-ray, neutron and electron diffraction. Disproportionation of SiO into Si and SiO2 is verified. High resolution TEM gives an upper limit of less than 2 nm for the typical Si cluster size. The Si K-edge electron energy-loss near-edge structure (ELNES) data of SiO are interpreted in terms of the oxidation states Si4+ and Si0. X-ray photoelectron spectroscopy gives first details about possible stoichiometric inhomogeneities related to internal interfaces. The wipe-out effect in the 29Si MAS NMR signal of SiO is confirmed experimentally. The new estimation of the wipe-out radius is about 1.1 nm. First-time W-band, Q-band, and X-band ESR and SQUID measurements indicate an interfacial defect structure. Frequency distributions of atomic nearest-neighbours are derived. The interface clusters mixture model (ICM model) suggested here describes the SiO structure as a disproportionation in the initial state. The model implies clusters of silicon dioxide and clusters of silicon surrounded by a sub-oxide matrix that is comparable to the well-known thin Si/SiO2 interface and significant in the volume because of small cluster sizes. 相似文献
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Both the (R)- and (S)-5'-hydroxy 5'-phosphonate derivatives of cytidine and cytosine arabinoside (ara-C) have been prepared via phosphite addition or a Lewis acid mediated hydrophosphonylation of appropriately protected 5'-nucleoside aldehydes. Phosphite addition to a cytosine aldehyde protected as the 2',3'-acetonide gave predominately the 5'R isomer, while phosphite addition to the corresponding 2',3'-bis TBS derivative favored the 5'S stereochemistry. In contrast, phosphite addition to the 2',3'-bis TBS protected aldehyde derived from ara-C gave only the 5'R adduct. However, TiCl(4)-mediated hydrophosphonylation of the same ara-C aldehyde favored the 5'S stereoisomer by a 2:1 ratio. Once all four of the diastereomers were in hand, the stereochemistry of these compounds could be assigned based on their spectral data or that obtained from their O-methyl mandelate derivatives. After hydrolysis of the phosphonate esters and various protecting groups, the four alpha-hydroxy phosphonic acids were tested for their ability to serve as substrates for the enzyme nucleoside monophosphate kinase and for their toxicity to K562 cells. 相似文献
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R. A. Smith J. B. Niederl J. H. C. Smith H. W. Milner A. W. C. Menzies F. Pregl Wm. J. Saschek M. Haitinger O. Heimstädt Ida B. Routh D. Kladischtscheff A. Soltys P. Muller G. Klein O. Werner H. Linser W. Jaeger L. Kofler W. Dernbach J. Deininger J. Donau F. Emich M. Malmy H. J. Fuchs G. W. Chapman E. Fränkel M. Gruber F. Feigl P. Krumholz Fr. L. Hahn G. Jaeger W. Herbert H. O. Hohl W. Münster J. Winkelmann A. Martini 《Analytical and bioanalytical chemistry》1934,99(9-10):355-364