REACTIVE SPECIES - Oxidation of Amino Acids, Peptides, and Proteins: Kinetics and Mechanism - page 26

in different biological oxidation and electron transfer reactions such as hydrox-
ylation, epoxidations, sulfoxodation, dehalogentation, and deamination [255,
256]. The interactions of high-valent metal ions with proteins and DNA may
lead to oxidative deterioration of biological molecules. For example, high-
valent compounds of Cr pose serious danger to biological systems and are
considered both toxic and carcinogenic (Chapter 6). The properties and reac-
tivity of Cr species are discussed in Chapter 6. Chapter 6 also highlights the
role of high-valent Cr species in carcinogenicity, genotoxicty, and cytotoxicity.
High-valent species of Mn and Fe have been reported as active intermedi-
ates in oxidation events of metalloenzymes [35, 257, 258]. Various complexes
of Mn and Fe have been synthesized to mimic biologically important processes
(Chapter 6). High-valent oxo complexes of Mn have been prepared to eluci-
date the role of Mn V -oxo species in water oxidation at the oxygen-evolving
center in photosystem II [259]. The aqueous chemistry of oxo compounds of
Mn is presented in Chapter 6. The rates of reactions between Mn(VII) and
amino acids are influenced by colloidal MnO 2 and phosphate species in solu-
tion (Chapter 6). Pathways of oxidation reactions carried out by Mn(VII) with
amino acids and aminopolycarboxylates are described in Chapter 6.
High-valent iron complexes as intermediates have been invoked in reac-
tions of heme and nonheme enzymes [260-264]. In recent years, several com-
plexes of iron(IV) and iron(V) have been synthesized as models to mimic
catalytic centers of enzymes [253, 265-270]. Properties of these complexes are
presented in Chapter 6. Rate studies have revealed that metal ions influence
the electron transfer from reductants to iron(IV) complexes (Chapter 6). A
summary of the recent work on the kinetics and products of reactions of
iron(IV) complexes with amino acids and peptides is presented in Chapter 6.

1.4 REACTIVE SPECIES IN ENVIRONMENTAL PROCESSES

1.4.1 Atmospheric Environment

Free radical species play a critical role in combustion, plasma environments,
interstellar clouds, and atmospheric chemistry [271]. Reactions of radical
species have been shown to have an adverse effect on human health and veg-
etation [272]. Species such as chlorine atoms, O 3 , • OH, and NO • can react with
inorganic and volatile organic compounds of the atmosphere [273-276]. For
example, the reaction of CO with • OH is important in combustion reactions
[271]. ROS are also formed in the reaction of O 3 with aerosol particles [277].
In recent years, reactions of NO • have also been studied. NO • radicals are
formed through the reaction of NO • with O 3 (Eq. 1.5):

O NO +

•

→ NO O

•

+ . (1.5)

3 2 3 2

Kinetic studies on the reactions of • OH and NO • radicals with a number
of 1-alkenes [CH 2 =CHR] and 2-methyl-1-alkenes [CH 2 =C(CH 3 )R], where