Direct Observation of Guanine Radical Cation Deprotonation in Duplex DNA Using Pulse Radiolysis

2003 ◽  
Vol 125 (34) ◽  
pp. 10213-10218 ◽  
Author(s):  
Kazuo Kobayashi ◽  
Seiichi Tagawa
Keyword(s):  
Radical Cation ◽  
Direct Observation ◽  
Pulse Radiolysis ◽  
Duplex Dna

Phenylalanine: Its ˙OH and SO4˙⁻-Induced Oxidation and Decarboxylation. A Pulse Radiolysis and Product Analysis Study

1993 ◽  
Vol 48 (6) ◽  
pp. 761-770 ◽  
Author(s):  
Degui Wang ◽  
Heinz-Peter Schuchmann ◽  
Clemens von Sonntag
Keyword(s):  
Radical Cation ◽  
Pulse Radiolysis ◽  
Side Reactions ◽  
Intramolecular Electron Transfer ◽  
Oh Radical ◽  
Product Analysis ◽  
Water Elimination ◽  
Deprotonation Reaction ◽  
Type Radical ◽  
Radical Yield

Phenylamine has been oxidized by radiolytically generated hydroxyl and sulfate radicals, the ensuing intermediates and their reactions have been studied by pulse radiolysis and product analysis in the absence and presence of oxidants such as Fe(CN)63- and O2. Upon OH radical attack, hydroxycyclohexadienyl-type radicals are mainly formed while Η-abstraction reactions can be neglected. In the presence of Fe(CN)63- these radicals are for the most part oxidized to the corresponding tyrosines (80%), except for the ipso-OH-adduct radicals (≈ 20%). It is concluded that ˙OH-addition is almost random, but with a slight avoidance of the metaposition relative to the ortho-, para- and ipso-positions. Oxygen adds reversibly to the OH-adduct radicals (kf = 1.8 × 108 dm3 mol-1 s-1, kr = 5.4 × 104 s-1). In this case, tyrosine formation occurs by HO2˙-elimination. However, due to side reactions, tyrosine formation only reaches 52% of the OH radical yield. The tyrosine yield drops to 10% in the absence of an oxidant.Upon SO4˙⁻-attack, decarboxylation becomes a major process (33% of SO4˙⁻) alongside the production of tyrosines (43%). Here, with Fe(CN)63- as the oxidant the formation of p-Tyr (18.5%) and m-Tyr (16.5%) is preferred over o-Tyr formation (8.5%). It is believed that in analogy to other systems a radical cation is formed immediately upon SO4˙⁻-attack which either reacts with water under the formation of hydroxycyclohexadienyl-type (“OH-adduct”) radicals, or decarboxylates after intramolecular electron transfer. The radical cation can also arise indirectly through H+-catalysed water elimination from the ˙OH-adduct radicals. At pH 2 and a dose rate of 0.0046 Gy s-1 CO2 formation matches the OH radical yield when ˙OH is the attacking radical. Below pH 2, G(CO2) decreases with falling pH. This indicates the occurrence of another, unimolecular, pathway under these conditions competing effectively with decarboxylation. This appears to be a relatively slow deprotonation reaction of the carboxylprotonated phenylalanine radical cation which gives rise to the benzyl-type radical.

scholarly journals Direct Observation of Primary C−H Bond Oxidation by an Oxido‐Iron(IV) Porphyrin π‐Radical Cation Complex in a Fluorinated Carbon Solvent

2019 ◽  
Vol 58 (32) ◽  
pp. 10863-10866 ◽  
Author(s):  
Yuma Morimoto ◽  
Yuki Shimaoka ◽  
Yuri Ishimizu ◽  
Hiroshi Fujii ◽  
Shinobu Itoh
Keyword(s):  
Radical Cation ◽  
Direct Observation ◽  
Fluorinated Carbon ◽  
Cation Complex

Direct Observation of Intramolecular Electron Transfer from Excess Electrons in a σ-Conjugated Main Chain to a Porphyrin Side Chain in Polysilanes Having a Tetraphenylporphyrin Side Chain by the Pulse Radiolysis Technique

2002 ◽  
Vol 21 (23) ◽  
pp. 5144-5147 ◽  
Author(s):  
Yoshinori Matsui ◽  
Kazutaka Nishida ◽  
Shu Seki ◽  
Yoichi Yoshida ◽  
Seiichi Tagawa ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Direct Observation ◽  
Pulse Radiolysis ◽  
Main Chain ◽  
Side Chain ◽  
Intramolecular Electron Transfer ◽  
Excess Electrons

Direct observation of penning electrons by pulse radiolysis-microwave cavity technique

1982 ◽  
Vol 19 (3) ◽  
pp. 255-259 ◽  
Author(s):  
Yoshihiko Hatano ◽  
Yu-ichi Kimizuka ◽  
Hiroshi Shimamori
Keyword(s):  
Direct Observation ◽  
Pulse Radiolysis ◽  
Microwave Cavity

Effect of positively charged backbone groups on radical cation migration and reaction in duplex DNA

2011 ◽  
Vol 89 (3) ◽  
pp. 326-330 ◽  
Author(s):  
Sriram Kanvah ◽  
Gary B. Schuster
Keyword(s):  
Radical Cation ◽  
Dna Analysis ◽  
Duplex Dna ◽  
Charge Migration ◽  
Electron Hole ◽  
Dna Oligomers ◽  
Phosphodiester Backbone ◽  
Cation Migration ◽  
Covalently Linked ◽  
Positively Charged

A series of DNA oligomers were prepared that contain guanidinium linkages (positively charged) positioned selectively in place of and among the normal negatively charged phosphodiester backbone groups of duplex DNA. One-electron oxidation of these DNA oligomers by UV irradiation of a covalently linked anthraquinone group generates a radical cation (electron “hole”) that migrates by hopping through the DNA and is trapped at reactive sites, GG steps, to form mutated bases that are detected by strand cleavage after subsequent piperidine treatment of the irradiated DNA. Analysis of the strand cleavage pattern reveals that guanidinium substitution in these oligomers does not measurably affect the charge migration rate but it does inhibit reaction at nearby guanines.

Direct observation of the protonation of acetone ketyl radical by conductometric pulse radiolysis

1980 ◽  
Vol 84 (25) ◽  
pp. 3351-3353 ◽  
Author(s):  
Eberhard Janata ◽  
Robert H. Schuler
Keyword(s):  
Direct Observation ◽  
Pulse Radiolysis ◽  
Ketyl Radical

Synthesis and Incorporation of a Cationic Pyridinium Nucleoside Mimic in Duplex DNA:  Effect on Long-Distance Radical Cation Transport

2006 ◽  
Vol 8 (23) ◽  
pp. 5255-5258 ◽  
Author(s):  
Frank O. Onyemauwa ◽  
Gary B. Schuster
Keyword(s):  
Radical Cation ◽  
Cation Transport ◽  
Duplex Dna ◽  
Long Distance
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