Compound I Cpd

The P450 enzyme from Pseudomonas putida (P450cam or C YP101), which hydroxylates camphor to 5-exo-hydroxycamphor has been studied in detail and is regarded as a model protein for other P450s. The electron donor to P450cam is putidaredoxin, which can deliver one electron at a time. In the course of the reaction, an activated oxygen atom from the heme iron is transferred to the unactivated C H bond of the substrate. A Fe(IV)=0 porphyrin-7r-cation radical has been proposed as the key iron-oxo intermediate, compound I (Cpd I), but it has remained elusive so far in studies of the enzyme with substrate ( RH ). 

Four-valent iron centers are well known as catalytic intermediates in enzymatic heme catalysis. The catalytic cycles of, for example, catalase, peroxidase, and cytochrome P450, all have in common an intermediate that is comprised of a ferryl Fe(IV) and a further oxidation equivalent located either on the heme ring or on the protein moiety. This reaction intermediate is called compound I (cpd I) and has a system spin of 5 = 1/2 (e.g., in chloroperoxidase) or 5 = 3/2 (e.g.,... 

More recently, Shaik and co-workers used density functional theory as well as QM(DFT)/MM calculations to show a pathway from the peroxoferric intermediate (5a) via the hydroperoxoferric (5b) intermediate to compound I (6) (see Figure 7.14)." In Figure 7.16, using Shaik s terminology, the peroxoferric intermediate is labeled (1), the hydroperoxoferric intermediate is labeled (2), Cpd 0, and the ferryloxo intermediate is labeled (3), Cpd I. 

Compounds I and II have been characterized by X-ray absorption and Raman spectroscopy. Both methods demonstrated the presence of an iron(fV) 0x0 entity in both Cpds I and Cpd II, with a short Fe=0 bond of 1.6 A consistent with a ferryl structure. Although it has been suggested that the Fe—O bond distance of Cpd II was longer 1.9 A at pH 7, and 1.7 at pH 10, resonance Raman studies showed that Cpds I and II have Fe=0 vibrations of comparable frequency, at 737cm and 776cm respectively, consistent with the ferryl description. 

Compounds of the type Zr(7r-Cpd)2, Ti(Tr-Cpd)2, and Cr(CaH6)2, were found to be completely inactive with all monomers whereas a significant number of transition metal allyl compounds were found to have weak activity for ethylene polymerization. The latter results are summarized in Table I. Despite the fact that many transition metal allyl compounds are unstable above 0°C, in the presence of monomer, the metal allyl structure... 

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Aromatic compounds may be oxidized either through epoxidation or via addition of oxygen atom from Cpd I (Scheme Id). Usually, both pathways afford more stable phenols or quinones as the end product through rearrangements and/or addition of another nucleophile. Direct abstraction of an electron from aromatic moiety is viable in the presence of strong electron-donating substituents. The oxidative metabohsm of polycyclic aromatic compounds is represented by CYPlAl in humans. 

Figure 13 Plot of percent crystallinity of SEDS processed compound (Cpd I) versus its proportion in HPC mixtures. (From Ref. 46.)...

As for other peroxidases, a high-valent iron-oxo entity associated with a porphyrin 7r-radical-cation, Cpd I, is generated by the addition of hydrogen peroxide (see Scheme 3 for the catalytic cycle of LiP). This green compound (Soret band at 408 nm) has UV-visible and EPR characteristics similar to that of HRP-Cpd 1. ... 

As noted above, the subset of compounds Cpd-l,Cpd-2,Cpd-3,Cpd-4 forms a complete subgraph of the threshold graph called a clique, i.e., Tio gs o.8s- Thus, the four compounds are all hnked in the threshold CSN, while Cpd-5 is an isolated vertex as reflected by the block diagonal stmcture of the adjacency matrix in Eq. (1.57). Because of the block diagonal stmcture, each block can be treated independently of the others, a form of dimensionahty reduction. 

CPD and 2,3-DCP are chiral compounds, which occur in protein hydrolysates and foods as racemic mixtines of corresponding enantiomers (-)-(J )-3-chloropropane-l,2-diol (12-28), (-F)-(S)-3-chloropropane-l,2-diol (12-29), (i )-2,3-dichloropropan-l-ol (12-30) and (S)-2,3-dichloropropan-l-ol (12-31), respectively. 

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