Newer aspects of the synthesis and chemistry of nitroxide spin labels

Keana, John F. W.

doi:10.1021/cr60311a004

Cited by 359 publications

(167 citation statements)

References 31 publications

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“…Only 5% of the gel-isolated cross-linked molecules had intact spinlabels. Nitroxides have a weak absorption at 410 nm and can undergo photoreduction to the hydroxylamine, photoaddition insertion reactions, and, in the case of l-oxy-2,2,5,5-tetramethyl-3-pyrroline, the photoextrusion of nitric oxide (NO) (Keana, 1978). No degradation of the EPR signal was observed when the spin-labeled psoralens or the various nitroxides used to synthesize 3-8 were irradiated with 366 nm laser light in aqueous solution for 5 min (data not shown).…”

Section: Spin-labeled Psoralensmentioning

confidence: 99%

Spin-Labeled Psoralen Probes for the Study of DNA Dynamics

Hp¹,

Dy²,

Ng³

et al. 1995

Biochemistry

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Six nitroxide spin-labeled psoralen derivatives have been synthesized and evaluated as probes for structural and dynamic studies. Sequence specific photoaddition of these derivatives to DNA oligonucleotides resulted in site-specifically cross-linked and spin-labeled oligomers. Comparison of the general line shape features of the observed electron paramagnetic resonance (EPR) spectra of several duplexes ranging in size from 8 to 46 base pairs with simulated EPR spectra indicate that the nitroxide spin-label probe reports the global tumbling motion of the oligomers. While there is no apparent large amplitude motion of the psoralen other than the overall tumbling of the DNA on the time scales investigated, there are indications of bending and other residual motions. The (A)BC excinuclease DNA repair system detects structural or dynamic features of the DNA that distinguish between damaged and undamaged DNA and are independent of the intrinsic structure of the lesion. NMR studies have shown that psoralencross-linked DNA has altered backbone dynamics and conformational populations in the immediate vicinity Psoralen-damaged DNA serves as an excellent substrate for the study of structural and dynamic motifs that DNA repair enzyme systems may recognize. Psoralens are photoreagents which form a well-characterized set of covalent nucleic acid adducts through photochemical addition ( Figure 1) (Straub et al., 1981; Kanne et al., 1982a,b). The primary reaction is cyclobutane ring formation between the 5,6 double bond of thymidine in DNA and either the 4',5' or 3,4 double bonds of the psoralen. Reaction at the 4'3' double bond creates a furanside monoadduct (MAf),' which can react further at a site with opposed and adjacent pyrimidines to create an interstrand cross-link (XL). The XL is a rigid unit formed by the psoralen and the opposite and adjacent pyrimidine bases, linking the two strands together. Reaction at the 3,4 double bond of the psoralen first creates a pyroneside monoadduct (MAP), which cannot form an interstrand cross-link.Psoralen-DNA monoadducts and cross-links are recognized and removed by the excision repair system in both

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Section: Spin-labeled Psoralensmentioning

confidence: 99%

Spin-Labeled Psoralen Probes for the Study of DNA Dynamics

Hp¹,

Dy²,

Ng³

et al. 1995

Biochemistry

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“…The importance of N-oxo compounds is connected with their technological applicability and use as pharmaceuticals (Table 19) and also as reagents in bio-organic (Table 20) and organic chemistry [85][86][87][88][105][106][107][108][109][110][111][112][113][114][115] . In this section, we concentrate on amine N-oxides [86][87][88] , nitroxide radicals and nitrones 89,[106][107][108][109][110][111][112][113][114][115] , and also on nitroso-compounds [116][117][118][119][120][121] .…”

Section: Determination Of N-oxo Compoundsmentioning

confidence: 99%

“…Nitrones are important reagents in organic synthesis 106,107 and also serve as excellent spin traps in electron paramagnetic resonance techniques 108,109 whereas nitroxide radicals play crucial role in spin labeling [113][114][115] . Nitroxide radicals belong to the most common classes of stable free radicals.…”

Section: Determination Of N-oxo Compoundsmentioning

confidence: 99%

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Trifluoroacetic anhydride-sodium iodide reagent. Nature and applications

Kudzin¹,

Kudzin²,

Drabowicz³

et al. 2007

Arkivoc

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Trifluoroacetic anhydride -sodium iodide mixture (TFAA-NaI; TFAA-I) reacts with several compounds bearing semipolar X-O bond, usually in the mode of deoxygenation, with liberation of iodine. The results of systematic investigations of the TFAA-I-reaction with various types of S-oxo and N-oxo compounds were discussed. The majority of these reactions are characterized by quantitative course, with respect to both X-O substrate transformation as well as to the amounts of liberated iodine. On this basis, a variety of sulphoxides and sulphimides were successfully reduced to sulphides and/or arene-N-oxides to amines, using TFAA-I at ambient temperature. Arene-and alkyl-sulphonic acids were reduced to the corresponding thiol derivatives in moderate yields. Stoichiometric course of the TFAA-I reaction with several S-oxo and N-oxo compounds gave origin to their analytical determinations. Thus, due to stoichiometric amounts of iodine formed from sulphoxides, sulphimides, arene-N-oxides, nitrones and nitroxide radicals, and nitroso compounds -the TFAA-I reagent can be applied to their analytical determination (titrimetric on µmol and spectrometric on nmol scale) and/or TLC detection.

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“…The epimerization from 2b-H configuration to 2a-H configuration was investigated by proton nuclear magnetic resonance ( 1 H NMR) spectrometry [16]. However, the 2-H configurations of these spin-labeled derivatives cannot be determined by NMR because conventional NMR spectra of nitroxide-containing molecules are quite broad and are therefore of limited use for monitoring the changes in structure taking place during a chemical synthesis [17]. Hence, also an urgent subject needs a new analytical method for ascertaining the 2-H configurations of these diastereoisomers.…”

Section: Introductionmentioning

confidence: 99%

HPLC‐DAD and HPLC‐ESI‐MS separation, determination and identification of the spin‐labeled diastereoisomers of podophyllotoxin

Zhao

Liu

Fan

et al. 2009

J of Separation Science

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Original Paper HPLC-DAD and HPLC-ESI-MS separation, determination and identification of the spin-labeled diastereoisomers of podophyllotoxinSpin-labeled nitroxide derivatives of podophyllotoxin had better antitumor activity and less toxicity than that of the parent compounds. However, the 2-H configurations of these spin-labeled derivatives cannot be determined by nuclear magnetic resonance (NMR) methods. In the present paper, a high-performance liquid chromatography-diode array detection (HPLC-DAD) and a high-performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI/MS/MS) method were developed and validated for the separation, identification of four pairs of diastereoisomers of spin-labeled derivatives of podophyllotoxin at C-2 position. In the HPLC-ESI/MS spectra, each pair of diastereoisomers of the spin-labeled derivatives in the mixture was directly confirmed and identified by [M+H]

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Newer aspects of the synthesis and chemistry of nitroxide spin labels

Cited by 359 publications

References 31 publications

Spin-Labeled Psoralen Probes for the Study of DNA Dynamics

Spin-Labeled Psoralen Probes for the Study of DNA Dynamics

Trifluoroacetic anhydride-sodium iodide reagent. Nature and applications

HPLC‐DAD and HPLC‐ESI‐MS separation, determination and identification of the spin‐labeled diastereoisomers of podophyllotoxin

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