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71.
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73.
Andersen C Sharma PK Christensen MS Steffansen SI Madsen CM Nielsen P 《Organic & biomolecular chemistry》2008,6(21):3983-3988
Oligodeoxynucleotides containing the double-headed nucleoside 5'(S)-C-(2-(thymin-1-yl)ethyl)thymidine were prepared by standard solid phase synthesis. The synthetic building block for incorporating the double-headed moiety was prepared from thymidine, which was stereoselectively converted to a protected 5'(S)-C-hydroxyethyl derivative and used to alkylate the additional thymine by a Mitsunobu reaction. The oligodeoxynucleotides were studied in different nucleic acid secondary structures: duplexes, bulged duplexes, three-way junctions and artificial DNA zipper motifs. The thermal stability of these complexes was studied, demonstrating an almost uniform thermal penalty of incorporating one double-headed nucleoside moiety into a duplex or a bulged duplex, comparable to the effects of the previously reported double-headed nucleoside 5'(S)-C-(thymin-1-yl)methylthymidine. The additional base showed only very small effects when incorporated into DNA or RNA three-way junctions. The various DNA zipper arrangements indicated that extending the linker from methylene to ethylene almost completely removed the selective minor groove base-base stacking interactions observed for the methylene linker in a (-3)-zipper, whereas interactions, although somewhat smaller, were observed for the ethylene linker in a (-4)-zipper motif. 相似文献
74.
We study the so-called weakly Koszul modules and characterise their Koszul duals. We show that the (adjusted) associated graded module of a weakly Koszul module exactly determines the homology modules of the Koszul dual. We give an example of a quasi-Koszul module which is not weakly Koszul. 相似文献
75.
A green and atom-economical method has been developed for the synthesis of piperazines by cyclocondensation of diols and amines in aqueous media in the presence of a catalytic amount of [Cp*IrCl2]2. 相似文献
76.
L.B. Madsen L.A.A. Nikolopoulos P. Lambropoulos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(1):67-79
Ab initio time-dependent (TD) calculations of the behavior of positronium (Ps) under strong subpicosecond laser pulses are presented.
The results are compared with results in H through scaling. It is found that a substantial amount of the population can be
found in excited states after the pulse. In the perturbative regime, generalized multiphoton ionization cross-sections are
extracted from the results of the time-dependent calculations. The generalized cross-sections are used to predict the response
of Ps to nanosecond laser pulses at wavelengths of current experimental interest. Beyond the application to Ps, the generality
of the method for extracting generalized cross-sections from TD nonperturbative calculations is discussed.
Received 8 June 1999 相似文献
77.
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79.
J. D. Brockman J. M. Guthrie J. S. Morris J. Davis R. Madsen J. D. Robertson 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(2):405-410
The toenail was examined as a biological monitor of Mg, Zn, and Cu intake using an observational case control model. The One
Source Cohort matched 63 individuals in Columbia Missouri who took the One Source multivitamin with 63 control individuals.
The matching criteria were based on age, sex, ethnicity, smoking status, and body mass index. The multivitamin contained supra-nutritional
levels of Se, Mg, Cu, and Zn. The toenail clippings were examined for these elements using instrumental neutron activation
analysis (INAA). A statistical analysis did not indicate a significant difference for Mg, Cu, or Zn between the nails of One
Source supplement users and control subjects (p<0.76, 0.55, and 0.85, respectively). The trace nutrient Se was used as an internal control. Previous studies have consistently
demonstrated that toenail Se is positively correlated with Se supplement use and the analysis did result in a significant
correlation in the toenails of One Source users and control subjects (p<1·10−4). This internal Se control suggests that the One Source Cohort is largely free from misclassification errors that could interfere
with the biomonitor response for the supranutritional intake of Mg, Cu, and Zn. 相似文献
80.
James A. Madsen Jennifer S. Brodbelt 《Journal of the American Society for Mass Spectrometry》2009,20(3):349-358
The number and types of diagnostic ions obtained by infrared multiphoton dissociation (IRMPD) and collision-induced dissociation
(CID) were evaluated for supercharged peptide ions created by electrospray ionization of solutions spiked with m-nitrobenzyl alcohol. IRMPD of supercharged peptide ions increased the sequence coverage compared with that obtained by CID
for all charge states investigated. The number of diagnostic ions increased with the charge state for IRMPD; however, this
trend was not consistent for CID because the supercharged ions did not always yield the greatest number of diagnostic ions.
Significantly different fragmentation pathways were observed for the different charge states upon CID or IRMPD with the latter
yielding far more immonium ions and often fewer uninformative ammonia, water, and phosphoric acid neutral losses. Pulsed-Q
dissociation resulted in an increase in the number of internal product ions, a decrease in sequence-informative ions, and
reduced overall ion abundances. The enhanced sequence coverage afforded by IRMPD of supercharged ions was demonstrated for
a variety of model peptides, as well as for a tryptic digest of cytochrome c. 相似文献