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41.
Coenen MJ Cremers M den Boer D van den Bruele FJ Khoury T Sintic M Crossley MJ van Enckevort WJ Hendriksen BL Elemans JA Speller S 《Chemical communications (Cambridge, England)》2011,47(34):9666-9668
The transition from low to high density 2D surface structures of copper porphyrins at a liquid/solid interface requires specific defects at which nearly all exchange of physisorbed molecules with those dissolved in the supernatant occurs. 相似文献
42.
M. M. Shehata B. Scholten I. Spahn S. M. Qaim H. H. Coenen 《Journal of Radioanalytical and Nuclear Chemistry》2011,288(3):887-893
The radiochemical separation of radiogallium from radiogermanium was studied using ion-exchange chromatography (Amberlite IR-120) and solvent extraction (Aliquat 336 in o-xylene). Both Amberlite IR-120 and Aliquat 336 in o-xylene have been used for the first time in separations involving radiogallium and radiogermanium. For tracer studies the radionuclides 68Ge (t 1/2 = 270.8 days), 69Ge (t 1/2 = 39 h) and 67Ga (t 1/2 = 78.3 h) were used. They were produced by the nuclear reactions natGa(p,xn)68,69Ge and natZn(p,xn)67Ga, respectively, and separated from their target materials in no-carrier-added form. Several factors affecting the separation of radiogallium from radiogermanium were studied and for each procedure the optimum conditions were determined. The solvent extraction using Aliquat 336 was found to be better. The separation yield of radiogallium was >95%, the time of separation short, the contamination from radiogermanium <0.008% and the final product was obtained in 0.5 M KOH. This method was adapted to the separation of n.c.a. 68Ga from its parent n.c.a. 68Ge. The quality of the product thus obtained is discussed. 相似文献
43.
SL Mironov E Skorova G Taschenberger N Hartelt VO Nikolaev MJ Lohse S Kügler 《BMC neuroscience》2009,10(1):29-11
Background
cAMP is an ubiquitous second messenger mediating various neuronal functions, often as a consequence of increased intracellular Ca2+ levels. While imaging of calcium is commonly used in neuroscience applications, probing for cAMP levels has not yet been performed in living vertebrate neuronal tissue before. 相似文献44.
This paper describes an efficient synthesis of fluorobenzyloxoimidazolidinone derivatives. The title compounds 1a, 1b and 1c could be prepared with high diasteromeric purity (>99%) and overall yields of 19%, 48% and 41% in a ten or six-step synthetic procedure, respectively. These compounds are used as precursors for isotopic 18F-labelling. 相似文献
45.
2-[(18)F]Fluoro-L-phenylalanine and 2-[(18)F]fluoro-L-tyrosine have been developed as promising radiopharmaceuticals for molecular imaging using positron emission tomography (PET). However, the lack of a convenient radiosynthetic pathway has limited their practical use. In this work a new three-step nucleophilic synthesis of these compounds starting from [(18)F]fluoride is described. Corresponding precursors (1a and 1b) were (18)F-fluorinated by isotopic exchange, followed by the removal of an activating formyl group with Rh(PPh(3))(3)Cl and subsequent hydrolysis of protecting groups in acidic medium. All reactions were carried out using both conventional and microwave heating. Conventional heated reactions yielded the desired products 2-[(18)F]Fphe and 2-[(18)F]Ftyr in 43% and 49% whereas radiochemical yields of 34% and 43%, respectively, were obtained when they were heated by microwaves. Under optimized conditions the enantiomeric purity was ≥94% for both radiopharmaceuticals. 相似文献
46.
Synthesis of no-carrier-added 4-[18F]fluorophenol from 4-benzyloxyphenyl-(2-thienyl)iodonium bromide
4-[(18)F]Fluorophenol is a versatile synthon for the synthesis of more complex radiopharmaceuticals bearing a 4-[(18)F]fluorophenoxy moiety. In order to prepare 4-[(18)F]fluorophenol in no-carrier-added (n.c.a.) form only a nucleophilic labelling method starting from [(18)F]fluoride is suitable. In this paper a new, two step radiosynthesis starting from 4-benzyloxyphenyl-(2-thienyl)iodonium bromide and [(18)F]fluoride with subsequent deprotection is described, yielding n.c.a. [(18)F]fluorophenol in 34 to 36% radiochemical yield. 相似文献
47.
48.
49.
MJ Lazaro AA Herod M Domin Y Zhuo CA Islas R Kandiyoti 《Rapid communications in mass spectrometry : RCM》1999,13(14):1401-1412
Three methods for determining a 'safe' estimate for high-mass limits of MALDI spectra of coal derived liquids were explored, using a sample of coal-tar pitch and its pyridine-insoluble fraction. Co-addition of increasing numbers of single-shot spectra (10, 30, 50 and 100 pulses) showed visually observable reductions in noise levels, consistent with robust and statistically meaningful signals. Three separate types of post-acquisition calculation were used to identify high-mass limits of the spectra. (i) A literature method indicated high-mass limits similar to those observed visually-as a shift from baseline at the highest masses, nearly 350 000 u for the coal tar pitch and about 390 000 u for its pyridine insoluble fraction. (ii) Comparing instrument signal with pre-selected multiples of the standard deviation, upper mass estimates of between 40-60 000 u for the coal-tar pitch and about 95 000 u for its pyridine-insoluble fraction were found. (iii) Calculation of the slope was used to identify 'lift-off' of the spectrum from baseline. The angle between the smoothed spectrum and the baseline was matched to a pre-selected value (e.g. 0.5 degrees and 1 degrees ). However, the arbitrary specification of the key parameter did not establish this last method on a firm basis. The choice of a criterion for estimating high-mass limits of MALDI spectra remains a semi-quantitative procedure; a reasonably conservative high-mass limit may be estimated by comparison of signal with five times the standard deviation. However, evaluation of size exclusion chromatograms of the present samples using polystyrene standards suggests that molecular mass distributions of pitch samples arrived at by MALDI mass spectrometry are, at least partly, determined by the limitations of available instruments. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
50.
V. R. Bom P. C. Coops R. W. Hollander E. Coenen K. Deneffe P. Van Duppen M. Huyse 《Zeitschrift für Physik A Hadrons and Nuclei》1986,325(2):149-155
Theβ +-spectra of the neutron deficient indium nuclei, produced in the reactionnatMo(16O,pxn), have been measured using a solid state beta detector, and mass separated sources. Values forQ EC have been determined for105–108In anc for105Cd and106Ag. 相似文献