Radicals and Radical Ions As Intermediates of Electron Transfer Processes Through Peptides
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The Two Faces of the Guanyl Radical: Molecular Context and Behavior
molecules Review The Two Faces of the Guanyl Radical: Molecular Context and Behavior Chryssostomos Chatgilialoglu 1,2 1 ISOF, Consiglio Nazionale delle Ricerche, 40129 Bologna, Italy; [email protected]; Tel.: +39-051-6398309 2 Center of Advanced Technologies, Adam Mickiewicz University, 61-712 Pozna´n,Poland Abstract: The guanyl radical or neutral guanine radical G(-H)• results from the loss of a hydrogen atom (H•) or an electron/proton (e–/H+) couple from the guanine structures (G). The guanyl radical exists in two tautomeric forms. As the modes of formation of the two tautomers, their relationship and reactivity at the nucleoside level are subjects of intense research and are discussed in a holistic manner, including time-resolved spectroscopies, product studies, and relevant theoretical calculations. Particular attention is given to the one-electron oxidation of the GC pair and the complex mechanism of the deprotonation vs. hydration step of GC•+ pair. The role of the two G(-H)• tautomers in single- and double-stranded oligonucleotides and the G-quadruplex, the supramolecular arrangement that attracts interest for its biological consequences, are considered. The importance of biomarkers of guanine DNA damage is also addressed. Keywords: guanine; guanyl radical; tautomerism; guanine radical cation; oligonucleotides; DNA; G-quadruplex; time-resolved spectroscopies; reactive oxygen species (ROS); oxidation 1. The Guanine Sink Citation: Chatgilialoglu, C. The Two The free radical chemistry associated with guanine (Gua) and its derivatives, guano- Faces of the Guanyl Radical: sine (Guo), 2’-deoxyguanosine (dGuo), guanosine-50-monophosphate (GMP), and 20- Molecular Context and Behavior. deoxyguanosine-50-monophosphate (dGMP), is of particular interest due to its biological Molecules 2021, 26, 3511. -
New Blatter-Type Radicals from a Bench-Stable Carbene
ARTICLE Received 6 Aug 2016 | Accepted 28 Feb 2017 | Published 15 May 2017 DOI: 10.1038/ncomms15088 OPEN New Blatter-type radicals from a bench-stable carbene Jacob A. Grant1, Zhou Lu2, David E. Tucker1, Bryony M. Hockin1, Dmitry S. Yufit1, Mark A. Fox1, Ritu Kataky1, Victor Chechik2 & AnnMarie C. O’Donoghue1 Stable benzotriazinyl radicals (Blatter’s radicals) recently attracted considerable interest as building blocks for functional materials. The existing strategies to derivatize Blatter’s radicals are limited, however, and synthetic routes are complex. Here, we report that an inexpensive, commercially available, analytical reagent Nitron undergoes a previously unrecognized transformation in wet acetonitrile in the presence of air to yield a new Blatter-type radical with an amide group replacing a phenyl at the C(3)-position. This one-pot reaction of Nitron provides access to a range of previously inaccessible triazinyl radicals with excellent benchtop stabilities. Mechanistic investigation suggests that the reaction starts with a hydrolytic cleavage of the triazole ring followed by oxidative cyclization. Several derivatives of Nitron were prepared and converted into Blatter-type radicals to test the synthetic value of the new reaction. These results significantly expand the scope of using functionalized benzotriazinyls as stable radical building blocks. 1 Department of Chemistry, Durham University, South Road, Durham DH1 3LE, UK. 2 Department of Chemistry, University of York, Heslington, York YO10 5DD, UK. Correspondence and requests for materials should be addressed to V.C. (email: [email protected]) or to A.M.C.O’D. (email: [email protected]). NATURE COMMUNICATIONS | 8:15088 | DOI: 10.1038/ncomms15088 | www.nature.com/naturecommunications 1 ARTICLE NATURE COMMUNICATIONS | DOI: 10.1038/ncomms15088 1 latter’s radical 1 (Fig. -
"Radical Stability --- Thermochemical Aspects" In
Radical Stability—Thermochemical Aspects Johnny Hioe and Hendrik Zipse Department of Chemistry, LMU M¨unchen, M¨unchen, Germany 1 INTRODUCTION is quite challenging. Kinetic data, in contrast, are much more difficult to predict by theory, while the The terms “transient” and “persistent” are used determination of reaction rates can be approached frequently in the scientific literature to describe experimentally with a variety of direct or indirect the kinetic properties of open shell systems in methods, at least for sufficiently fast reactions homogeneous solution.1–5 The hydroxyl radical (see Radical Kinetics and Clocks). Theory and (HO•, 1), for example, is a transient species of experiment pair up nicely in this respect, as a central importance in atmospheric chemistry (see combination of these approaches is able to provide Atmospheric Radical Chemistry), as well as one a comprehensive picture of thermodynamic and of the most important reactive oxygen species kinetic data. (ROS) in aqueous solution, whereas the nitroxide 2,2,6,6-tetramethylpiperidine-1-oxyl, TEMPO (2)is a persistent radical stable enough to be bottled and 2 DEFINITIONS OF RADICAL STABILITY sold in bulk (Figure 1) (see Nitroxides in Synthetic Radical Chemistry). The thermodynamic stability of C-centered radicals However, despite their widespread use, these can be defined in various ways and several options terms are not too helpful for a quantitative approach are discussed in the following.6–10 One of the to radical chemistry as they do not reflect the most often used definitions is based on hydrogen influence of thermochemical driving force and transfer reactions as shown in Scheme 1 for reaction • intrinsic reaction barrier on the observed lifetime. -
Formation and Structure of Radicals from D-Ribose and 2-Deoxy- D-Ribose by Reactions with SO 4 Radicals in Aqueous Solution
Formation and Structure of Radicals from D-Ribose and 2-Deoxy- D-ribose by Reactions with SO 4 Radicals in Aqueous Solution. An in-situ Electron Spin Resonance Study Janko N. Herak Faculty of Pharmacy and Biochemistry, The University of Zagreb, Zagreb. Croatia, Yugoslavia Günter Behrens Max-Planck-Institut für Strahlenchemie. D-4330 Mülheim a.d. Ruhr, Bundesrepublik Deutschland Z. Naturforsch. 41c, 1062 — 1068 (1986); received January 31, 1986 Free Radicals, Deoxy-D-ribose, D-Ribose, Conformational Kinetics, Electron Spin Resonance ESR spectroscopy has been used to analyse the conformation of the radicals produced by the reaction of SOj with D-ribose (1),and 2-deoxy-D-ribose (6 ),at pH 1.3-5. From ribose three different types of radicals formed by H abstraction at C-l, C-2 and C-3 followed by a regio- selective a,ß-water elimination have been identified: the 2-deoxy-ribonolacton-2-yl (3), the 1-deoxy-pentopyranos-2-ulos-l-yl (4). and the 4-deoxy-pentopyranos-3-ulos-4-yl (2). Using deoxyribose two radicals of similar type, formed by H abstraction at C-3 and C-4 followed by water elimination, have been observed: the 2,4-dideoxy-3-ulos-4-yl (7) and the 2,3-dideoxy-4- ulos-3-yl (8). In addition, from both sugars an a-hydroxyalkyl radical has been identified based in part on the timing of their conformational motions: the ribos-3-yl (5) (the precursor of 2) and the 2-deoxy-ribos-l-yl (9), respectively. For radical 5 the rate constant k(e) for the water elimination and hence transformation into radical 2 was estimated. -
Intermolecular Radical Carboamination of Alkenes
Chem Soc Rev View Article Online REVIEW ARTICLE View Journal | View Issue Intermolecular radical carboamination of alkenes a ab Cite this: Chem. Soc. Rev., 2020, Heng Jiang and Armido Studer * 49,1790 Vicinal alkene carboamination is a highly efficient and practical synthetic strategy for the straightforward preparation of diverse and valuable amine derivatives starting from simple compounds. During the last decade that approach has found continuous research interests and various practical methods have been developed using transition-metal catalysis. Driven by the renaissance of synthetic radical chemistry, intermolecular radical alkene carboamination comprising a C–C bond and a C–N bond forming step has been intensively investigated recently culminating in novel strategiesandimprovedprotocolswhichcomplementexisting methodologies. Radical alkene carboamination can be achieved via three different reaction modes. Such cascades can proceed through N-radical addition to an alkene with subsequent C–C bond formation leading to 2,1-carboamination products. Alternatively,theC–CbondcanbeinstalledpriortotheC–Nbondvia initial C-radical addition to the alkene with subsequent b-amination resulting in 1,2-carboamination. The third mode Received 18th November 2019 comprises initial single electron oxidation of the alkene to the corresponding alkene radical cation that gets Creative Commons Attribution 3.0 Unported Licence. DOI: 10.1039/c9cs00692c trappedbyanN-nucleophileandthecascadeisterminatedbyradicalC–Cbondformation.Inthisreview, the three different -
Radical P-Chains in L3(2)
East Tennessee State University Digital Commons @ East Tennessee State University Electronic Theses and Dissertations Student Works 5-2001 Radical p-chains in L3(2). Donald Dewayne Belcher East Tennessee State University Follow this and additional works at: https://dc.etsu.edu/etd Part of the Physical Sciences and Mathematics Commons Recommended Citation Belcher, Donald Dewayne, "Radical p-chains in L3(2)." (2001). Electronic Theses and Dissertations. Paper 133. https://dc.etsu.edu/etd/ 133 This Thesis - Open Access is brought to you for free and open access by the Student Works at Digital Commons @ East Tennessee State University. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of Digital Commons @ East Tennessee State University. For more information, please contact [email protected]. RADICAL p-CHAINS IN L3(2) AThesis Presented to the Faculty of the Department of Mathematics East Tennessee State University In Partial Fulfillment of the Requirements for the Degree Master of Science in Mathematical Sciences by Donald D. Belcher May 2001 Committee Members Dr. Janice Huang, Chair Dr. Jeff Knisley Dr. Debra Knisley ABSTRACT RADICAL p-CHAINS IN L3(2) by Donald D. Belcher The McKay-Alperin-Dade Conjecture, which has not been finally verified, predicts the num- ber of complex irreducible characters in various p-blocks of a finite group G as an alternating sum of the numbers of characters in related p-blocks of certain subgroups of G. The sub- groups involved are the normalizers of representatives of conjugacy classes of radical p-chains of G. For this reason, it is of interest to study radical p-chains. -
1. Factor Completely 2X^4-12X^3+12X^2
1. factor completely 2x^4-12x^3+12x^2 2x2(x2 – 6x + 6) 2a. solve 2x^2=6 b. find x intercepts of f(x)=2x^2-6 type exact answers, use radicals as needed, rationalize all denominators Solutions: 3, − 3 x-intercepts: ( 3, 0), (− 3, 0) 5. use foil to find product (6x^5-7)(x^6-1) 6x11 – 7x6 – 6x5 + 7 11. state value of discriminant 18x62+10x-20=0 is there one real solution or 2 imaginary solutions or 2 real solutions? Discriminant = 1540 Equation has 2 real solutions 13. multiply (3x+5)(2x^2+4x+7) 6x3 + 22x2 + 41x + 35 14. simplify 12 over radical (-3)^12 12 12 (−3) = 3 16. multiply (-4x)^2(3x^5)^2 144x12 18. solve 5/z = 7/z-1/5 z = 10 19. find vertex, line of symmetry, the maximum OR minimum value for x, state whether is it max or min and if graph opens up or down f(x)=1/3(x+2)^2+6 Vertex is (-2, 6) Line of symmetry is x = -2 Minimum value of f(x) is 6 f(-2) = 6 is a minimum Graph opens up Graph looks like this: 22. 81a^2-121 factor binomial (9a + 11)(9a – 11) 26. use rational exponents to write x^1/2 times y^1/6 times z^1/3 as single radical expression 6 x3yz2 29. subtract simplify by collecting radical terms if possible 4 radical 32 ñ 4 radical 2 4 32 − 4 2 =12 2 32. factor completely 100a^2+160af+64f^2 4(5a + 4f)2 33. -
Radical Stability—A Theoretical Perspective
Top Curr Chem (2006) 263: 163–189 DOI 10.1007/128_028 © Springer-Verlag Berlin Heidelberg 2006 Published online: 23 February 2006 Radical Stability—A Theoretical Perspective H. Zipse Department of Chemistry and Biochemistry, LMU München, Butenandtstrasse 5–13, 81377 München, Germany [email protected] 1Introduction................................... 164 1.1 TheoreticalMethods.............................. 165 1.2 AlkylRadicalswithOneSubstituent...................... 166 1.3 MultiplySubstitutedAlkylRadicals...................... 173 1.4 TheStabilityofDelocalizedRadicals..................... 180 1.5 The Stability of σ-AlkylRadicals........................ 182 2 Heteroatom-Based Radicals .......................... 182 2.1 Nitrogen-CenteredRadicals........................... 182 2.2 Oxygen-CenteredRadicals........................... 184 3 Connecting the Scales .............................. 185 References ....................................... 186 Abstract The thermodynamic stability of radicals as defined through isodesmic hy- drogen transfer reactions has been explored at a variety of theoretical levels. Radical stabilization energies (RSEs) derived from single point calculations at the ROMP2/ 6-311+G(3df,2p)//UBecke3LYP/6-31G(d) level of theory in combination with scaled zero point vibrational energies calculated at the UBecke3LYP/6-31G(d) level have been deter- mined for a broad variety of systems. For the three radical types considered in this study (carbon-, nitrogen-, and oxygen-centered radicals) the radical stabilization energy