HIGH-VALENT Cr, Mn, AND Fe SPECIES - Oxidation of Amino Acids, Peptides, and Proteins: Kinetics and Mechanism - page 300

Cr(VI)

cellular
diols

Cr(V)-diols
g = 1.979
major signal

Cr(III)
complexes
observed in
6.5 K spectra

Cr(VI)O 4 2-

dependent on
thiols and
NAD(P)H

possible ligand
exchange with
carbohydrates
NAD(P)H, etc.

Cr(V)-GS
decomposition
product
g = 1.979
second signal

Cr(V)-GSH
g = 1.996
not observed

decomposition/
ligand oxidation

Figure 6.11. General scheme for the formation of the Cr species responsible for the
ESR signals observed in BEAS-2B cells. The species associated with each signal are in
boldface type. The dashed arrows indicate possible pathways to the formation of certain
species, but the exact pathways are not known. The diagram is not meant to be inclusive
of all possible pathways or Cr species but rather is intended to relate the various species
observed in these cells (adapted from Borthiry et al. [164] with the permission of Else-
vier Inc.).

Dysregulated
DNA repair
mechanisms

Cr(VI)
exposure

Pre malig nant
Progression

Malignant
conversion

• Tissue injury
• Inflammation

Death resistance

Normal
cell

• Dysregulated survival signaling
• Transcriptional repatterning

Tumor cell

Early-stage carcinogenesis

Figure 6.12. Cellular resistance to Cr(VI)-induced death and early-stage carcinogen-
esis (adapted from Nickens et al. [129] with the permission of Elsevier Inc.).