|
|
~~~ EFFECTS OF ABSORBTION OF PHOTON ENERGY ~~~
BOND TYPES: RESULTS: EQUATIONS:
sigma scattering X--X --> X* + e- + X+
sigma anti bonding X--X --> X* + X*
pi singlet to triplet X==X <--> *X--X*
pi singlet to triplet to new sigmas *X--X* + 2Y -->
(photochemical rearrangement) Y--X--X--Y
pi photoreduction *X--X* + 2AOH -->
HX--XH + 2AO*
conjugated pi singlets to resonant triplets X==X--X==X -->
*X--X==X--X*
conjugated pi singlet to triplet to sigmas *X--X==X--X* + 2Y -->
(complex rearrangements) Y--X--X==X--X--Y
conjugated pi photoreduction *X--X==X--X* + 2AOH -->
HX--X==X--XH + 2AO*
oxygen low energy triplet to high *O--O* --> [*O--O*]
oxygen low energy triplet to singlet *O--O* --> O==O
oxygen activated dye plus triplet *X--X* + *O--O* <-->
oxygen to both singlets X==X + O==O
~~~ MECHANISMS OF SINGLET OXYGEN PRODUCTION ~~~
By Oxidation:
-OO* + Fe+++ ---> O=O + Fe++
HOOH + ClO- ---> O=O + HOH + Cl-
By Direct Photoactivation:
*OO* + hv ---> O=O
By Indirect Photoactivation Of A Dye:
X=X + hv ---> *X-X*
*X-X* + *OO* ---> X=X + O=O
~~~ ADDITION REACTIONS OF SINGLET OXYGEN ~~~
1) Endoperoxide formation /O-O\
O==O + -C==C--C==C- --> -C C-
\C=C/
2) Dioxetane formation O--O O O
O==O + -C==C- --> | | --> || + ||
H H -C--C- -C C-
H H H H
3) Lipid peroxide formation OOH
H |
O==O + -C==C--C- --> -C--C==C-
H H H H H H
4) Conversion of phenols to quinones
HO-@ + O=O --> HO-@-OO --> O=@-OOH --> O=@=O + HOH
\H \H
~~~ COMBINED OXIDATIVE EFFECTS OF UVBIT ~~~
1) Photoreduction * * H H
uv + -X==X- + 2AOH --> -X--X- + 2AOH --> -X--X- + 2(AO*)
2) Singlet oxygen production * *
uv + -X==X- + *OO* --> -X--X- + *OO* --> -X==X- + O=O
O=O + @ --> @OO --> @ + O=O
3) Dioxetane rearrangment to aldehydes
O--O
O=O + R-C==C-R' --> R-C--C-R' --> R-C=O + O=C-R'
H H H H H H
4) Lipid peroxide production and reductive removal
O=O + LH --> LOOH
2(GSH) + LOOH --> GSSG + LOH + HOH
5) Quinone production and redox cycling of quinone
O=O + HO-@ --> O=@=O + HOH
XH2 + Q + *OO* --> *XH + *QH + *OO* --> *XH + Q + HOO*
6) Theoretic cyclo-oxygenation of docosoids which trigger
synthesis of nitric oxide /O-O\
O=O + -C=C-C=C- --> -C-C=C-C-
~~~ QUENCHING OF SINGLET OXYGEN ~~~
Singlet oxygen production by dye activation:
* *
uv + -X==X- + *OO* --> -X--X- + *OO* --> -X=X- + O=O
Quenching of singlet oxygen by energy loss to pi bond:
* *
O=O + -Y==Y- --> *OO* + -Y--Y-
The more extensively conjugated a system of pi bonds,
the more active a quencher of singlet oxygen it is.
Beta-carotene is the most famous example baring eleven:
CH3 CH3 CH3 2(CH3)C-C-C-C
\ | | \ /
C=C-C=C-C=C-C=C-C=C-C=C-C=C-C=C-C=C-C=C-C=C
/ \ | | \
C-C-C-C2(CH3)2 CH3 CH3 CH3
Numerous aromatic compounds can do the same being
extensively conjugated.
~~~ HOMOLOGY AMONG ARYL AMINES ~~~
ANILINES: PABA: SULFONAMIDES:
HNH HNH HNH
| | |
C C C
// \ // \ // \
HC CH HC CH HC CH
| || | || | ||
HC CH HC CH HC CH
\\ / \\ / \\ /
C C C
| | |
R COOH O=S=O
|
HN-R
~~~ HOW SULFA DRUGS MIGHT DEFEAT THE BENEFITS
OF ULTRAVIOLET BLOOD IRRADIATION THERAPY ~~~
1) Quenching of Singlet Oxygen:
NH2-@-SO2-NHR + O=O ---> NH2-*@*-SO2-NHR + *OO*
2) Reduction of Some of the Oxidants Produced:
NH2-@-SO2-NHR + *X--X* ---> *NH-@-SO2-NHR + HX--X*
3) Imine Formation with Carbonyl Compounds:
\ \
C=O + NH2-@-SO2-NHR ---> C=N-@-SO2-NHR + HOH
/ /