Zum Mechanismus des anaeroben, radikalinduzierten DNA‐Strangbruches

Giese, Bernd; Beyrich-Graf, Xenia; Burger, Jutta; Kesselheim, Christoph; Senn, Martin; Schäfer, Thomas

doi:10.1002/ange.19931051244

Cited by 24 publications

(11 citation statements)

References 13 publications

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“…This observation may be explained by a slightly higher absorption of the salt 2d ( 350 ϭ 7157 M Ϫ1 cm Ϫ1 ) compared with that of 2a (⑀ 350 ϭ 4973 M Ϫ1 cm Ϫ1 ). However, because the LD spectroscopic investigations showed unambiguously that the ratio between the intercalated and the externally bound dye is higher for amine 2a than for the derivatives 2b-2e, we conclude that the strand break takes place on the external sugar moiety of the nucleic acid according to the mechanism proposed by Schulte-Frohlinde and coworkers (27), further elucidated by Giese et al (28). Further evidence of this assumption is provided by the observation that the DNA cleavage takes place under anaerobic conditions, and no alkaline work-up is required to detect the strand breaks.…”

Section: Discussionsupporting

confidence: 55%

Acridizinium Salts as a Novel Class of DNA-binding and Site-selective DNA-photodamaging Chromophores¶

Ihmels¹,

Faulhaber²,

Sturm³

et al. 2001

Photochem Photobiol

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It was demonstrated that the interaction of the aminoacridizinium salts 2a-2d with DNA depends on the substitution pattern of the chromophore. Spectrophotometric and fluorometric titrations of the acridizinium salts 2a-2d with natural and synthetic polynucleotides reveal that the degree of interaction of the acridizinium salts 2a-2d with the nucleic acid differs significantly. The binding mode of the dyes with DNA was evaluated by circular dichroism and linear dichroism spectroscopy and compared with the parent system 2c. Whereas the 9-aminoacridizinium (2a) mainly intercalates into DNA, the salts 2b-c show a higher degree of association to the DNA backbone. The intercalated aminoacridizinium 2a caused few strand breaks upon UVA exposure, whereas the salts 2b-2d exhibit relatively efficient DNA-damaging properties. All acridizinium salts showed a sequence-selective strand cleavage for guanine-rich DNA regions.

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Section: Discussionsupporting

confidence: 55%

Acridizinium Salts as a Novel Class of DNA-binding and Site-selective DNA-photodamaging Chromophores¶

Ihmels¹,

Faulhaber²,

Sturm³

et al. 2001

Photochem Photobiol

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“…(2)]. In support of this mechanistic hypothesis, Giese,7a Newcomb,7b and Crich7c have previously demonstrated the fundamental steps of this proposal through radical cation generation from β‐(phosphatoxy)alkyl selenides and PTOC esters, respectively. …”

Section: Methodsmentioning

confidence: 81%

Diffusion‐weighted magnetic resonance imaging of acute hypoxic‐ischemic cerebral lesions in the survivor of a monochorionic twin pregnancy: case report

Righini

Kustermann

Parazzini

et al. 2007

Ultrasound in Obstet & Gyne

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CASE REPORTA 30-year-old woman, gravida 2 para 1, was referred to our fetal magnetic resonance imaging (MRI) service at week 24 of a monochorionic twin pregnancy, because 4 h earlier a transabdominal ultrasound examination had demonstrated absence of cardiac activity in the smaller twin and no brain lesions in the survivor. There was a history of twin-to-twin transfusion syndrome. No serological signs of maternal-fetal infections had been reported. A transabdominal ultrasound examination that had been performed 44 h earlier had shown the twins alive and with normal intracranial anatomy. Based on our experience of fetal MRI detection of ischemic lesions in survivors of monochorionic twin pregnancies 1 , in our institution pregnant women carrying the diagnosis of cotwin death usually undergo fetal brain MRI as early as possible, followed by a second examination 2-3 weeks later. The woman gave written consent to undergo prenatal MRI at our institution.MRI was performed at 1.5 Tesla, using an abdominal phase-array coil, with 4-mm thick multiplanar single-shot fast spin-echo (ss-FSE) T2-weighted sections (TR/TE = 3000/180 ms, field of view = 320 mm, matrix = 256 × 256) and with 6-mm thick multiplanar diffusion-weighted imaging (DWI) sections (TR/TE = 1000/90 ms, field of view = 360 mm, matrix = 128 × 128, b-factor max = 600 mm 2 /s, three axis diffusion sensitized gradient directions, acquisition time = 7 s, during maternal apnea). Apparent diffusion coefficient (ADC) maps were calculated. While ss-FSE T2-weighted images were uninformative, the ADC value was markedly reduced compared to normal (0.4 µm 2 /ms; normal fetal brain value = 1.9 µm 2 /ms (Righini et al. 2 )) within the deep frontal white matter of both hemispheres, especially on coronal sections (Figure 1). At the 14-day follow-up MRI study, ss-FSE T2-weighted images showed extensive malacic areas bilaterally in the periventricular frontal white matter, with disruption of the anterior portion of the corpus callosum and of the septum pellucidum, and with a cyst at the level of the septum pellucidum remnants. The medial frontal cortex was partially involved at the level of the pericallosum gyrus bilaterally. On the same occasion, ultrasound imaging showed large hypoechogenic areas within the medial and anterior portions of both cerebral hemispheres (Figure 2).Normal vaginal delivery occurred at 35 weeks of gestation. Neonatal neurological examination showed mild hypotonia but no seizures were noted. MRI confirmed the prenatal imaging findings.

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“…The products are best explained as arising from nucleophilic attack on the radical cation (19) by the allyl alcohol, followed by radical cyclization (Scheme 23) [47]. The very high degree of retention of configuration at the 3' site in the major product prompted Zipse to propose a double inversion mechanism for the direct substitution.…”

Section: Substitution Reactions and Their Applications In Synthesismentioning

confidence: 99%

Radical Rearrangements of Esters

Crich¹

2001

Radicals in Organic Synthesis

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Long considered inert toward radicals, esters are now known to have a rich and interesting spectrum of free-radical chemistry. The purpose of this chapter is to highlight this reactivity and its applications, real and potential, in synthetic organic chemistry. Application and mechanism are intimately linked and it is therefore necessary to begin by placing the very broad spectrum of reactivity within as comprehensive a mechanistic framework as possible, which should provide a solid basis for further rational development of the area. The subject was comprehensively reviewed in 1997 [ I] and the reader is referred to that article for a detailed discussion of the early development of the field as well as for a complete listing of kinetic parameters available at the time. In the meantime, however, there have been major developments, particularly with regard to mechanism, and a brief recapitulation is needed in order that they may be fully appreciated. Kinetic parameters that have appeared since 1997 are to be found in articles by Crich and Newcomb [2-41; illustrative rate constants are given, whenever available, in the Schemes below. MechanismThe mechanism of the p-( phosphatoxy)alkyl and /I-(acy1oxy)alkyl rearrangements and their less well known but closely related cousins, the /?-(su1fatoxy)alkyl and pnitroxyalkyl rearrangements, has long presented a conundrum to workers in the field [ 11. Instances of reactions proceeding via pure 2,3-shifts [ I ] and pure 1,2-shifts [5] are known as are apparent mixed mechanisms, leading to the suggestion [ 11 that 5-center-5-electron and 3-center-3-electron concerted pathways both exist, with the precise selection for a particular example being a function of substituent effects and solvent. However, the possibility that all rearrangements occurred via a rapid radical ionic fragmentation, to give an alkene radical cation and a carboxylate or phosphate counter ion followed by rapid recombination, advocated by Sprecher [6], Radicals in Organic Synthesis Edited

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Zum Mechanismus des anaeroben, radikalinduzierten DNA‐Strangbruches

Cited by 24 publications

References 13 publications

Acridizinium Salts as a Novel Class of DNA-binding and Site-selective DNA-photodamaging Chromophores¶

Acridizinium Salts as a Novel Class of DNA-binding and Site-selective DNA-photodamaging Chromophores¶

Diffusion‐weighted magnetic resonance imaging of acute hypoxic‐ischemic cerebral lesions in the survivor of a monochorionic twin pregnancy: case report

Radical Rearrangements of Esters

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