(and also the BDFE) of tBu3PhOH.40 The EPR equilibration approach supplies
Author manuscript; readily available in PMC 2011 December eight.Warren et al.Pageoxidation goods are thought to play deleterious roles in a variety of illness states, which includes atherosclerosis and aging.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptThe proton-coupled redox chemistry of tyrosine (TyrOH) and related compounds has been extensively reported.128?29130131 In aqueous options, the Disorder (DAD)Laptop or computer use 3/4 p for trend N ( ) 36168 (74.0) 6262 (12.8) 6420 (13.1) DAD Prevalence ( ) 1.46 1.29 1.62 Model Pourbaix diagram shows a clear 59 mV per pH dependence for the oxidation of tyrosine below pH ten, indicative of a 1e-/ 1H+ redox couple. By way of example, the adjusted Pedulli values for BDFE(PhOH) and BDFE(2,6-tBu2PhOH) in C6H6, = 83.eight and 78.three kcal mol-1 (Table 4), agree pretty closely with our conversion of Bordwell's BDFEs in DMSO (from E?and pKa values)116 to C6H6 employing the Abraham process, 83.7 and 78.1 kcal mol-1, respectively. 5.2.three Tyrosine--Redox reactions of the amino acid tyrosine are involved in biological energy transduction, charge jir.2012.0142 transport, oxidative strain, and enzymatic catalysis.123 The 1H+/1e- oxidized form, the tyrosyl radical, has been implicated within a selection of enzymatic systems, which includes ribonucleotide reductases,109 photosystem II,106 galactose oxidase,124 prostaglandin-H-synthase125 and perhaps cytochrome c oxidase.126 In addition, tyrosineNIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptChem Rev. Author manuscript; out there in PMC 2011 December eight.Warren et al.Pageoxidation products are believed to play deleterious roles in numerous illness states, including atherosclerosis and aging.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptThe proton-coupled redox chemistry of tyrosine (TyrOH) and related compounds has been widely reported.128?29130131 In aqueous solutions, the Pourbaix diagram shows a clear 59 mV per pH dependence for the oxidation of tyrosine under pH ten, indicative of a 1e-/ 1H+ redox couple. As for phenol, above pKa(tyrosine) the redox potential does not depend on pH mainly because this can be the proton-independent TyrO?TyrO- redox couple. Other, much more detailed, discussions of aspects of proton-coupled redox chemistry of tyrosine is usually found in other contributions to this concern. As an aside, we encourage biochemical research of PCET to make use of a nomenclature that explicitly shows the proton, which include `TyrOH' for tyrosine, to prevent ambiguity. As an illustration, the usually made use of "Y? for tyrosyl radicals could refer either to neutral radical TyrO?or for the commonly high-energy radical cation TyrOH?. five.2.four -Tocopherol and Connected Phenols---Tocopherol (a main element of Vitamin E) is believed to become a important chain breaking antioxidant in biological systems. Due to the fact its discovery in 1922,132 vitamin E has received considerable interest from chemists, biologists, and clinicians, among others.110 Resulting from its insolubility in water, a number of small water soluble analogs for instance Trolox C ((?-6-hydroxy-2,5,7,8-tetramethylchromane-2carboxylic acid) and HPMC (6-hydroxy-2,2-5,7,8-pentamethylchroman) have been created (Scheme eight; see references 133 and 134). As shown in Table four, these 3 phenols show similar thermochemistry within the very same solvent. This is in very good agreement with their solution kinetic behavior and indicates that the analogs lacking the greasy phytyl tails are very good models for the redox chemistry of tocopherol.