Cytochrome <i>c</i><i>−</i>Crown Ether Complexes as Supramolecular Catalysts:
Cold-Active Synzymes for Asymmetric Sulfoxide Oxidation in Methanol
Atsuko Suzumura
Dharam Paul
Hideki Sugimoto
Satoshi Shinoda
Ryan R. Julian
J. L. Beauchamp
Junji Teraoka
Hiroshi Tsukube
10.1021/ic0486567.s001
https://acs.figshare.com/articles/journal_contribution/Cytochrome_i_c_i_i_i_Crown_Ether_Complexes_as_Supramolecular_Catalysts_Cold_Active_Synzymes_for_Asymmetric_Sulfoxide_Oxidation_in_Methanol/3300100
A series of supramolecular complexes of various cytochrome <i>c</i> proteins with 18-crown-6 derivatives behave as
cold-active synzymes in the H<sub>2</sub>O<sub>2</sub> oxidation of racemic sulfoxides. This interesting behavior contrasts with native
functionality, where the employed proteins act as electron transfer carriers. ESI-MS, UV, CD, and Raman spectroscopic
characterizations reveal that four or five 18-crown-6 molecules strongly bind to the surface of the cytochrome <i>c</i>
and also that nonnatural low-spin hexacoordinate heme structures are induced in methanol. Significantly, crown
ether complexation can convert catalytically inactive biological forms to catalytically active artificial forms. Horse
heart, pigeon breast, and yeast cytochromes <i>c</i> all stereoselectively oxidize (<i>S</i>)-isomers of methyl tolyl sulfoxide
and related sulfoxides upon crown ether complexation. These supramolecular catalysts show the highest efficiency
and enantiomer selectivity at −40 °C in the H<sub>2</sub>O<sub>2</sub>-dependent sulfoxide oxidation, while oxidative decomposition of
the heme moieties predominantly occurs at room temperature. The oxidation reactivity of the employed sulfoxides
is apparently related to steric constraints and electrochemical oxidation potentials of their SO bonds. Among the
cytochrome <i>c</i> complexes, yeast cytochrome <i>c</i> demonstrates the lowest catalytic activity and degradation reactivity.
It has a significantly different protein sequence, suggesting that crown ether complexation effectively activates
heme coordination but may additionally alter the native backbone structure. The proper combination of cytochrome
<i>c</i> proteins, 18-crown-6 receptors, and external circumstances can be used to successfully generate “protein-based
supramolecular catalysts” exhibiting nonbiological reactivities.
2005-02-21 00:00:00
nonbiological reactivities
stereoselectively oxidize
supramolecular complexes
yeast cytochrome c
backbone structure
Raman spectroscopic characterizations
oxidation reactivity
Asymmetric Sulfoxide Oxidation
crown ether complexation
electrochemical oxidation potentials
sulfoxide oxidation
activates heme coordination
protein sequence
cytochrome c proteins
methyl tolyl sulfoxide
UV
behavior contrasts
yeast cytochromes c
room temperature
proteins act
steric constraints
oxidative decomposition
racemic sulfoxides
H 2 O 2
supramolecular catalysts show
degradation reactivity
cytochrome c complexes
pigeon breast
electron transfer carriers
enantiomer selectivity
cytochrome c
horse heart
H 2 O 2 oxidation
heme moieties