Biochemistry of Photodynamic Action - ACS Symposium Series (ACS

Chapter 6

Biochemistry of Photodynamic Action 1

2

John D. Spikes and Richard C. Straight 1

Department of Biology, University of Utah, Salt Lake City, UT 84112 Veterans Administration Medical Center and Departments of Medicine and Surgery (Laser Institute), University of Utah School of Medicine, Salt Lake City, UT 84148

Downloaded by UNIV OF ARIZONA on May 30, 2017 | http://pubs.acs.org Publication Date: May 7, 1987 | doi: 10.1021/bk-1987-0339.ch006

2

Cells and organisms are injured and killed by exposure to light in the presence of many photosensitizers. This phenomenon, which typically requires molecular oxygen, is termed photodynamic action and results from the sensitized photodegradation of essential biomolecules in cells. The major cellular targets are unsaturated lipids, proteins and nucleic acids. Photodynamic effects are mediated by photochemically generated singlet oxygen, free radicals, hydrogen peroxide and superoxide, depending on the sensitizer, the chemical nature of the molecule being photodegraded, and the reaction conditions. This paper reviews the photochemical and biochemical pathways involved in the photodynamic degradation of the major classes of susceptible biomolecules.

Organisms are v e r y s e n s i t i v e t o s h o r t e r wavelength u l t r a v i o l e t r a d i a t i o n t h a t i s absorbed e f f i c i e n t l y by e s s e n t i a l b i o m o l e c u l e s such as n u c l e i c a c i d s and p r o t e i n s . R a d i a t i o n i n the l o n g wavelength u l t r a v i o l e t - v i s i b l e range i s much l e s s h a r m f u l , i n p a r t because r e l a t i v e l y few types o f b i o m o l e c u l e s absorb a p p r e c i a b l y i n t h i s r e g i o n of the spectrum. However, i n the presence o f a p p r o p r i a t e p h o t o s e n s i t i z e r s , a l l k i n d s o f organisms, p l a n t and a n i m a l , s i n g l e c e l l e d and m u l t i c e l l u l a r , are i n j u r e d and k i l l e d by l i g h t i n t h i s range (1,2) · The h a r m f u l e f f e c t s r e s u l t from the s e n s i t i z e d p h o t o a l t e r a t i o n o f c r i t i c a l types of b i o m o l e c u l e s ; t h i s i n t u r n i n t e r f e r e s w i t h m e t a b o l i c processes and the proper f u n c t i o n of c e l l u l a r s t r u c t u r e s and o r g a n e l l e s ( c e l l membranes, m i t o c h o n d r i a , nuclei, etc.). T h i s chapter reviews the b i o c h e m i c a l changes t h a t occur i n d i f f e r e n t k i n d s o f molecules o f b i o l o g i c a l importance as a r e s u l t o f i l l u m i n a t i o n i n the presence o f p h o t o s e n s i t i z e r s . P r o b a b l y the f i r s t b i o c h e m i c a l study o f a photodynamic r e a c t i o n was t h a t o f P r o f e s s o r Hermann von Tappeiner and h i s s t u d e n t s who showed i n 1903

0097-6156/87/0339-0098$06.00/0 © 1987 American Chemical Society

Heitz and Downum; Light-Activated Pesticides ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

6.

SPIKES AND STRAIGHT

Biochemistry of Photodynamic Action

99


t h a t e o s i n s e n s i t i z e s the p h o t o i n a c t i v a t i o n of the enzymes d i a s t a s e , i n v e r t a s e and p a p a i n under a e r o b i c c o n d i t i o n s (3)· Von T a p p e i n e r c o i n e d the term "photodynamic" i n a c t i v a t i o n f o r t h i s phenomenon (^_) · Much l a t e r the i n a c t i v a t i o n was shown to r e s u l t from the s e n s i t i z e d p h o t o o x i d a t i o n of c e r t a i n amino a c i d r e s i d u e s i n the p r o t e i n s (_5) · Blum ( 4 ) , i n h i s s e m i n a l monograph "Photodynamic A c t i o n and D i s e a s e s Caused by L i g h t " , suggested t h a t the term "photodynamic a c t i o n " be c o n f i n e d to those p h o t o s e n s i t i z e d r e a c t i o n s t h a t r e q u i r e m o l e c u l a r oxygen and i n which oxygen i s consumed. Not a l l i n v e s t i g a t o r s accept t h i s d e f i n i t i o n , but f o r c o n v e n i e n c e , we w i l l use i t i n t h i s r e v i e w . A c t u a l l y , most p h o t o s e n s i t i z e d r e a c t i o n s i n v o l v i n g b i o m o l e c u l e s do r e q u i r e m o l e c u l a r oxygen. There are n o t a b l e e x c e p t i o n s , however, which cannot be covered i n t h i s r e v i e w (_1) · Comments on Photodynamic Mechanisms and

Photosensitizers

Two p r i n c i p l e mechanisms are i n v o l v e d i n photodynamic r e a c t i o n s , termed Type I and Type I I p r o c e s s e s , r e s p e c t i v e l y ( 6 - 9 ) . I n Type I r e a c t i o n s the l i g h t - e x c i t e d s e n s i t i z e r ( t y p i c a l l y i n i t s t r i p l e t s t a t e ) r e a c t s d i r e c t l y w i t h the s u b s t r a t e v i a an e l e c t r o n or hydrogen atom t r a n s f e r w i t h the p r o d u c t i o n of f r e e r a d i c a l forms of the two r e a c t a n t s . These s p e c i e s can r e a c t f u r t h e r i n a number of ways; i n the presence of oxygen the p r o d u c t s are o f t e n an o x i d i z e d form of the s u b s t r a t e and the r e g e n e r a t e d ground s t a t e of the s e n s i t i z e r . I n some r e a c t i o n s of t h i s type, s u p e r o x i d e or hydrogen p e r o x i d e i s produced which can o x i d i z e some b i o m o l e c u l e s . S e n s i t i z e r t r i p l e t i n Type I I r e a c t i o n s i n t e r a c t s by energy t r a n s f e r w i t h ground s t a t e oxygen ( w h i c h i s a t r i p l e t ) y i e l d i n g ground s t a t e s e n s i t i z e r and s i n g l e t oxygen; t h i s l a t t e r s p e c i e s i s h i g h l y e l e c t r o p h i l i c and can r e a c t w i t h many types of b i o m o l e c u l e s much more r a p i d l y than does ground s t a t e oxygen ( 6 - 9 ) . A l t h o u g h photodynamic r e a c t i o n s i n v o l v i n g b i o m o l e c u l e s sometimes appear to be s i m p l e , they more o f t e n t u r n out to be r a t h e r complex. S e v e r a l , o f t e n competing, r e a c t i o n pathways can be i n v o l v e d , depending on the s u b s t r a t e (compound being p h o t o o x i d i z e d ) , the s e n s i t i z e r , the s o l v e n t , and the r e a c t i o n c o n d i t i o n s ( r e a c t a n t c o n c e n t r a t i o n s , pH, s o l v e n t , e t c . ) . I n many cases the p r i m a r y product i s u n s t a b l e and decays v e r y r a p i d l y to secondary p r o d u c t s . A l s o , the p r i m a r y or subsequent p r o d u c t s may themselves be s u s c e p t i b l e to f u r t h e r photodynamic d e g r a d a t i o n ( 6 ) . S e v e r a l hundred compounds have been examined f o r t h e i r a b i l i t y t o s e n s i t i z e p h o t o r e a c t i o n s of b i o m o l e c u l e s . Effective p h o t o s e n s i t i z e r s f o r b i o l o g i c a l systems i n c l u d e n a t u r a l p r o d u c t s such as i r o n - f r e e p o r p h y r i n s ( c o p r o p o r p h y r i a protoporphyrin, u r o p o r p h y r i n ) , f l a v i n s such as r i b o f l a v i n and FMN, c h l o r o p h y l l and a number of o t h e r compounds found i n p l a n t s i n c l u d i n g a l k a l o i d s , extended q u i n o n e s , f u r a n o c o u m a r i n s , p o l y a c e t y l e n e s , t h l o p h e n e s , e t c . A l a r g e number of s y n t h e t i c compounds i n c l u d i n g a c r i d i n e s such as a c r i d i n e orange, a n t h r a q u i n o n e s , a z i n e dyes, many k e t o n e s , a l a r g e number of s y n t h e t i c p o r p h y r i n s , p h t h a l o c y a n i n e s , t h i a z i n e dyes such as methylene b l u e , xanthene dyes such as e o s i n and rose b e n g a l , etc. (2,10).


LIGHT-ACTIVATED PESTICIDES

100 B i o c h e m i s t r y of Photodynamic R e a c t i o n s

In S o l u t i o n


B i o m o l e c u l e s s u s c e p t i b l e to photodynamic a c t i o n i n c l u d e c e r t a i n o r g a n i c a c i d s , a l c o h o l s , amines, c a r b o h y d r a t e s , n i t r o g e n h e t e r o c y c l i c s , n u c l e i c a c i d s and c e r t a i n n u c l e i c a c i d bases, some p l a n t hormones, p r o t e i n s and c e r t a i n amino a c i d s , p y r r o l e s , s t e r o i d s , u n s a t u r a t e d l i p i d s , some v i t a m i n s , e t c . A v e r y l a r g e amount of r e s e a r c h has been done on the e f f e c t s of photodynamic treatment i n v i t r o ( i n s o l u t i o n ) on these types of b i o m o l e c u l e s , as reviewed b r i e f l y i n the f o l l o w i n g s e c t i o n s . There are s e v e r a l r e c e n t s h o r t reviews of photodynamic e f f e c t s on b i o m o l e c u l e s (1,2,7,8) and one d e t a i l e d r e v i e w (5); these may be c o n s u l t e d f o r a more i n - d e p t h i n t r o d u c t i o n t o the l i t e r a t u r e of t h i s a r e a . Photodynamic E f f e c t s on A l c o h o l s and C a r b o h y d r a t e s . A l c o h o l s and c a r b o h y d r a t e s , i n c l u d i n g s i m p l e s u g a r s , p o l y s a c c h a r i d e s such as c e l l u l o s e , and complex c a r b o h y d r a t e s such as a l g i n a t e s , h e p a r i n and h y a l u r o n i c a c i d are p h o t o o x i d i z e d s l o w l y ; anthraquinone and ketone s e n s i t i z e r s are the most e f f e c t i v e ( 5 , 6 , 1 1 ) . These r e a c t i o n s t y p i c a l l y proceed by a Type I p r o c e s s . For example, a hydrogen atom i s a b s t r a c t e d from the a l p h a - c a r b o n of a l c o h o l s ; the r e s u l t i n g a l c o h o l r a d i c a l r e a c t s w i t h oxygen, g i v i n g an aldehyde or c a r b o x y l i c a c i d f o r primary a l c o h o l s and a ketone f o r secondary a l c o h o l s (6)· H e x i t o l s are p h o t o o x i d i z e d f i r s t to the hexose and then to the c o r r e s p o n d i n g h e x o n i c a c i d . C e l l u l o s e i s p h o t o o x i d i z e d by s i m i l a r p r o c e s s e s g i v i n g damaged and weakened f i b e r s ( " p h o t o t e n d e r i n g " ) (6)· H y a l u r o n i c a c i d , a h i g h m o l e c u l a r weight g l y c o s a m i n o g l y c a n , i s a major component of the j e l l y - l i k e ground substance of animal t i s s u e s and of the v i t r e o u s humor of the eye. The v i s c o s i t y of h y a l u r o n i c a c i d s o l u t i o n s p r o g r e s s i v e l y decreases on i l l u m i n a t i o n i n the presence of photodynamic s e n s i t i z e r s ; t h i s has g e n e r a l l y been regarded as r e s u l t i n g from a f r e e r a d i c a l i n i t i a t e d s c i s s i o n of the h y a l u r o n i c a c i d c h a i n . Methylene b l u e s e n s i t i z e s a v i s c o s i t y decrease i n a r e a c t i o n a p p a r e n t l y mediated by s i n g l e t oxygen; the change i n v i s c o s i t y appears t o r e s u l t from a l t e r a t i o n s i n the t e r t i a r y s t r u c t u r e of the h y a l u r o n i c a c i d f o l l o w e d by o n l y minor d e p o l y m e r i z a t i o n ( 1 1 ) . C l e a r l y much remains t o be l e a r n e d about the mechanisms of photodynamic e f f e c t s on complex c a r b o h y d r a t e s . Photodynamic E f f e c t s on L i p i d s . The l i p i d s are a d i v e r s e group of compounds i n c l u d i n g f a t t y a c i d s , f a t s ( t r i g l y c e r i d e s of f a t t y a c i d s ) , p h o s p h o l i p i d s , s t e r o i d s and t h e i r d e r i v a t i v e s , e t c . U n s a t u r a t e d f a t t y a c i d s , and f a t s and p h o s p h o l i p i d s c o n t a i n i n g u n s a t u r a t e d f a t t y a c i d s , are s u s c e p t i b l e to photodynamic a c t i o n by both Type I and Type I I p r o c e s s e s (_5) · A l l y l i c h y d r o p e r o x i d e s are formed i n i t i a l l y i n both mechanisms; however, the k i n e t i c s of p h o t o o x i d a t i o n and the d i s t r i b u t i o n of product isomers are d i f f e r e n t i n the two c a s e s . The Type I process i s more complex, g i v i n g r i s e to a l l y l i c f r e e r a d i c a l s t h a t can r e a c t to g i v e d i f f e r e n t h y d r o p e r o x i d e s as w e l l as a l c o h o l s , epoxides and k e t o n e s . The r e a c t i o n w i t h s i n g l e t oxygen i s o f t e n much s i m p l e r , w i t h fewer p r o d u c t s being formed. P o l y u n s a t u r a t e d f a t s and p h o s p h o l i p i d s appear to be p h o t o o x i d i z e d l a r g e l y by a Type I I r e a c t i o n g i v i n g mono- and d i h y d r o p e r o x i d e s ; these i n i t i a l products can undergo dark



6.

SPIKES AND STRAIGHT


101

a u t o x i d a t i o n w i t h f u r t h e r d e g r a d a t i o n and the f o r m a t i o n of more complex m i x t u r e s of r e a c t i o n p r o d u c t s (5-7,12)* The i n i t i a l step i n the Type I I process i s an "ene" r e a c t i o n ( 1 3 ) . C h o l e s t e r o l g i v e s a c h a r a c t e r i s t i c a l l y d i f f e r e n t p a t t e r n of p r o d u c t s depending on whether i t i s p h o t o o x i d i z e d by a Type I or a Type I I p r o c e s s . A g a i n , the s i n g l e t oxygen pathway g i v e s a s i m p l e r product p a t t e r n , i . e . , almost e n t i r e l y the 5-alpha-hydroperoxide w i t h o n l y s m a l l amounts of o t h e r h y d r o p e r o x i d e s . In c o n t r a s t , i n the f r e e r a d i c a l p r o c e s s , the 7-alpha- and 7-beta-hydroperoxides are formed along w i t h a number of o t h e r p r o d u c t s ( 5 - 7 , 1 4 ) . Other s t e r o i d s can a l s o be p h o t o o x i d i z e d , i n c l u d i n g p r e d n i s o l o n e , d e o x y c o r t i c o s t e r o n e and s u b s t i t u t e d h y d r o c o r t i s o n e s . For example, they are p h o t o o x i d i z e d t o c a r b o x y l i c a c i d d e r i v a t i v e s on i l l u m i n a t i o n i n the presence of f l a v i n s ( 1 5 ) . E s t r o n e i s i r r e v e r s i b l y photobound t o p r o t e i n i n a s e n s i t i z e d r e a c t i o n ( 1 6 ) , w h i l e some c o n t r a c e p t i v e s t e r o i d s are decomposed by photodynamic treatment ( 1 7 ) . These r e a c t i o n s may account f o r the p h o t o a l l e r g y shown by some i n d i v i d u a l s u s i n g o r a l c o n t r a c e p t i v e s . Photodynamic E f f e c t s on Amino A c i d s . Of the a p p r o x i m a t e l y 20 amino a c i d s t h a t occur i n p r o t e i n s , o n l y f i v e ( c y s t e i n e , a t h i o l ; h i s t i d i n e , an i m i d a z o l e ; m e t h i o n i n e , an o r g a n i c s u l f i d e ; t r y p t o p h a n , an i n d o l e ; and t y r o s i n e , a phenol) are p h o t o o x i d i z e d r a p i d l y w i t h photodynamic s e n s i t i z e r s ; these amino a c i d s a l l have e l e c t r o n - r i c h s i d e c h a i n s ( 5 , 6 - 8 ) . The mechanisms and k i n e t i c s of amino a c i d p h o t o o x i d a t i o n depend on the amino a c i d , the s e n s i t i z e r , the s o l v e n t , the pH, e t c . (5)· W i t h e o s i n , rose b e n g a l , p r o f l a v i n and p o r p h y r i n s , c y s t e i n e i s p h o t o o x i d i z e d l a r g e l y to c y s t i n e i n a Type I I p r o c e s s ; the pH dependence of the r a t e i n d i c a t e s t h a t the unprotonated t h i o l group i s most r e a c t i v e ( 5 , 1 8 ) . The t h i o l f r e e r a d i c a l i s produced d u r i n g the h e m a t o p o r p h y r i n - s e n s i t i z e d p h o t o o x i d a t i o n of c y s t e i n e ( 1 9 ) . I n c o n t r a s t , c y s t e i n e i s p h o t o o x i d i z e d to c y s t e i c a c i d w i t h c r y s t a l v i o l e t i n what appears t o be a Type I r e a c t i o n ( 2 0 ) . H i s t i d i n e i s r a p i d l y p h o t o o x i d i z e d w i t h many s e n s i t i z e r s . The r e a c t i o n r a t e i n c r e a s e s w i t h pH i n a f a s h i o n demonstrating t h a t the unprotonated i m i d a z o l e r i n g of h i s t i d i n e i s the r e a c t i v e s i t e (5_) · H i s t i d i n e and r e l a t e d i m i d a z o l e s appear to be p h o t o o x i d i z e d by a Type I I process w i t h the f o r m a t i o n of endoperoxides; these are v e r y u n s t a b l e , and break down r a p i d l y w i t h d e s t r u c t i o n of the i m i d a z o l e r i n g and the f o r m a t i o n of a number of secondary products ( 7 , 2 1 ) . W i t h some s e n s i t i z e r s , such as rose b e n g a l , methionine i s p h o t o o x i d i z e d d i r e c t l y to methionine s u l f o x i d e by a Type I I process at low pH, or i f the amino group i s b l o c k e d . At h i g h pH w i t h the amino group f r e e , the p r i m a r y product i s dehydromethionine, which s l o w l y h y d r o l y z e s w i t h the f o r m a t i o n of methionine s u l f o x i d e i n a r a t h e r complex r e a c t i o n ( 1 8 , 2 2 ) . I n c o n t r a s t , w i t h f l a v i n and benzophenone type s e n s i t i z e r s , methionine i s deaminated and d e c a r b o x y l a t e d by a Type I r e a c t i o n t o g i v e the aldehyde, m e t h i o n a l ( 2 3 ) . T h i s can be f u r t h e r photodegraded t o y i e l d a v a r i e t y of products. Tryptophan g i v e s complex m i x t u r e s of p r o d u c t s on p h o t o o x i d a t i o n i n r e a c t i o n s t h a t depend on the s e n s i t i z e r and the r e a c t i o n c o n d i t i o n s ; some of the p r o d u c t s can be f u r t h e r p h o t o o x i d i z e d . Both



102


Type I and Type I I p r o c e s s e s can a p p a r e n t l y be i n v o l v e d . One product produced by r e a c t i o n w i t h s i n g l e t oxygen i s Nf o r m y l k y n u r e n i n e , which i t s e l f i s a good photodynamic s e n s i t i z e r (5,24,25). T y r o s i n e appears to be p h o t o o x i d i z e d by both Type I and Type I I r e a c t i o n s ; the r e a c t i o n r a t e i n c r e a s e s w i t h pH i n a manner showing t h a t the phenolate a n i o n i s the most e a s i l y p h o t o o x i d i z e d form of the m o l e c u l e . R e l a t i v e l y l i t t l e i s known of the p h o t o o x i d a t i o n p r o d u c t s , a l t h o u g h r u p t u r e of the t y r o s i n e r i n g does occur (5,6) · A r g i n i n e and l y s i n e have been r e p o r t e d to be p h o t o o x i d i z e d under some c o n d i t i o n s ( 5 ) , and the p h o t o o x i d a t i o n of p h e n y l a l a n i n e i s s e n s i t i z e d by f l a v i n e s (26,27). A l t h o u g h p r i m a r y amine groups are a p p a r e n t l y not p h o t o o x i d i z e d , the c o n c e n t r a t i o n of f r e e amino groups i n a s o l u t i o n of some amino a c i d s decreases on p h o t o o x i d a t i o n ; t h i s may r e s u l t from i n t r a - or i n t e r - m o l e c u l a r dark r e a c t i o n s between i n i t i a l o x y g e n a t i o n products and primary amino groups ( 2 8 ) . Photodynamic E f f e c t s on P r o t e i n s . With the e x c e p t i o n of h o r s e r a d i s h p e r o x i d a s e and s u p e r o x i d e d i s m u t a s e , a l l of the over 100 p r o t e i n s t h a t have been examined are s u s c e p t i b l e to photodynamic treatment ( 5^. P r o t e i n s examined i n c l u d e enzymes of a l l c a t e g o r i e s , b l o o d plasma p r o t e i n s ( a l b u m i n s , c e r u l o p l a s m l n , complement, f i b r i n o g e n , hemopexin, heraocyanin, i m m u n o g l o b u l i n s , e t c . ) , hormones ( i n s u l i n , g l u c a g o n , e t c . ) , and m i s c e l l a n e o u s p r o t e i n s such as b a c t e r i a l t o x i n s , c o l l a g e n , cytochromes, eye l e n s c r y s t a l l i n e , g l o b i n s , ovalbumin, o v o t r a n s f e r r i n , snake venom p r o t e i n s , s p e c t r i n , t u b u l i n , e t c . ( a d e t a i l e d l i s t i n g i s g i v e n i n r e f . 5) · Oxygen i s consumed i n these r e a c t i o n s ; however, l i t t l e i s known of i t s u l t i m a t e f a t e i n most c a s e s . The s i t e ( s ) of damage on the p r o t e i n molecule i s t y p i c a l l y one or more of the c y s t e i n y l , h i s t i d y l , m e t h i o n y l , t r y p t o p h y l and t y r o s y l r e s i d u e s (5)· Susceptible residues located at the s u r f a c e of p r o t e i n m o l e c u l e s w i l l tend t o be p h o t o o x i d i z e d f a s t e r than r e s i d u e s b u r i e d i n the i n t e r i o r of the p r o t e i n . I f the p r o t e i n i s c o m p l e t e l y u n f o l d e d , a l l of the s u s c e p t i b l e r e s i d u e s can be p h o t o o x i d i z e d ( 2 9 ) . In most cases p e p t i d e bonds are not broken as a r e s u l t of photodynamic treatment (5_) · Some s e l e c t i v i t y of r e s i d u e p h o t o o x i d a t i o n can be o b t a i n e d u s i n g s e n s i t i z e r s t h a t b i n d t o s p e c i f i c s i t e s on p r o t e i n molecules ( 5 , 3 0 ) . A few p r o t e i n s c o n t a i n n a t u r a l p h o t o s e n s i t i z i n g chromophores bound i n p a r t i c u l a r r e g i o n s ( 5 ) . For example, i n the case of the enzyme 6-phosphogluconate dehydrogenase, the enzyme c o f a c t o r , p y r i d o x a l , s e n s i t i z e s the photodynamic m o d i f i c a t i o n of a h i s t i d i n e r e s i d u e l o c a t e d near the p y r i d o x a l b i n d i n g s i t e of the enzyme ( 3 1 ) . A number of types of p h y s i c o c h e m i c a l changes are observed i n p h o t o d y n a m i c a l l y - t r e a t e d p r o t e i n s i n c l u d i n g a l t e r a t i o n s of a b s o r p t i o n spectrum, a g g r e g a t i o n p r o p e r t i e s , c o f a c t o r - and m e t a l binding p r o p e r t i e s , conformation, mechanical p r o p e r t i e s , o p t i c a l r o t a t i o n , s o l u b i l i t y , v i s c o s i t y , e t c . ( 5 ) . I n c r e a s e d s e n s i t i v i t y to d e n a t u r a t i o n by heat or u r e a , and i n c r e a s e d s u s c e p t i b i l i t y to d i g e s t i o n by p r o t e a s e s are o f t e n observed as a r e s u l t of the photodynamic treatment of p r o t e i n s (32) · The n a t u r e and e x t e n t of a l l of these p h y s i c o c h e m i c a l changes depends on the p r o t e i n , the s e n s i t i z e r , the r e a c t i o n c o n d i t i o n s , the degree of p h o t o o x i d a t i o n of



6.


SPIKES AND STRAIGHT

103

the p r o t e i n , e t c . (5)· I l l u m i n a t i o n of some s e n s i t i z e r - p r o t e i n c o m b i n a t i o n s r e s u l t s i n the f o r m a t i o n of c o v a l e n t s e n s i t i z e r - p r o t e i n photoadducts, presumably by Type I p r o c e s s e s ( 5 , 3 3 ) . I n some c a s e s , p r o t e i n s are c r o s s - l i n k e d by photodynamic treatment g i v i n g p r o t e i n d i m e r s , t r i m e r s , e t c . The mechanisms of c r o s s - l i n k i n g are not f u l l y u n d e r s t o o d . I n the case of s p e c t r i n , a membrane p r o t e i n from e r y t h r o c y t e s , i t has been suggested t h a t c r o s s - l i n k i n g r e s u l t s from the i n t e r a c t i o n of a p h o t o o x i d i z e d h i s t i d y l r e s i d u e on one s p e c t r i n m o l e c u l e w i t h a f r e e amino group on another s p e c t r i n m o l e c u l e (34) . The p h o t o s e n s i t i z e d c o v a l e n t c r o s s - l i n k i n g of p r o t e i n s t o DNA (35) , and the p h o t o s e n s i t i z e d c o v a l e n t c o u p l i n g of p r o t e i n s t o s m a l l m o l e c u l e s such as t r y p t o p h a n (36) a l s o o c c u r . Photodynamic treatment u s u a l l y a l t e r s or d e s t r o y s the normal b i o l o g i c a l f u n c t i o n of p r o t e i n s . For example, almost a l l enzymes l o s e t h e i r b i o c a t a l y t i c a c t i v i t y as a r e s u l t of the d e s t r u c t i o n of e s s e n t i a l amino a c i d r e s i d u e s i n the a c t i v e s i t e or b i n d i n g s i t e of the enzyme or by the a l t e r a t i o n of r e s i d u e s l o c a t e d elsewhere t h a t are n e c e s s a r y f o r the normal c a t a l y t i c conformation of the enzyme (_5). The a n t i g e n i c i t y of some p r o t e i n s as w e l l as t h e i r a b i l i t y t o r e a c t w i t h a n t i b o d i e s d i r e c t e d toward them i s d e c r e a s e d . The b i o l o g i c a l f u n c t i o n s of p e p t i d e hormones such as a n g i o t e n s i n , g l u c a g o n , i n s u l i n , e t c . are d e s t r o y e d by photodynamic t r e a t m e n t , and p r o t e i n t o x i n s from b a c t e r i a , p l a n t s and snakes are i n a c t i v a t e d (5_). Photodynamic E f f e c t s on P u r i n e s and P y r i m i d l n e s . The s e n s i t i z e d p h o t o o x i d a t i o n of b i o l o g i c a l l y important p u r i n e s and p y r i m i d l n e s , t h e i r n u c l e o s i d e s and n u c l e o t i d e s , and some r e l a t e d compounds has been examined u s i n g a number of d i f f e r e n t s e n s i t i z e r s ( 5 , 3 7 ) . In g e n e r a l , under p h y s i o l o g i c a l c o n d i t i o n s , p u r i n e s are p h o t o o x i d i z e d more r e a d i l y than p y r i m i d l n e s , and guanine and i t s d e r i v a t i v e s are more s u s c e p t i b l e than o t h e r p u r i n e s (5_). Ring s u b s t i t u e n t s on n u c l e i c a c i d bases can have a major e f f e c t on the s e n s i t i v i t y t o photooxidation. For example, w i t h hematoporphyrin, 5 - a m i n o u r a c i l and 5 - h y d r o x y u r a c i l are p h o t o o x i d i z e d v e r y much f a s t e r than 5raethyluracil ( 3 8 ) . The p h o t o o x i d a t i o n of guanine and some of the o t h e r n u c l e i c a c i d bases can o c c u r by both Type I and Type I I p r o c e s s e s , w i t h the r e l a t i v e involvement of each pathway depending on the p h o t o s e n s i t i z e r used. Rose bengal s e n s i t i z e s the p h o t o o x i d a t i o n of 3 * , 5 - d i - 0 - a c e t y l - 2 - d e o x y g u a n o s i n e l a r g e l y by a Type I I mechanism; i n c o n t r a s t , r i b o f l a v i n and benzophenone s e n s i t i z e the r e a c t i o n p r i m a r i l y by a Type I process ( 3 9 ) . R i b o f l a v i n a l s o s e n s i t i z e s the p h o t o o x i d a t i o n of 2'-deoxyguanosine by a Type I p r o c e s s ( 4 0 ) . W i t h many s e n s i t i z e r s , the r a t e of p h o t o o x i d a t i o n of guanine and i t s d e r i v a t i v e s i n c r e a s e s w i t h i n c r e a s i n g pH i n a manner i n d i c a t i n g t h a t the a n i o n i c forms of these compounds, as w i t h some amino a c i d s , are the most s e n s i t i v e t o a t t a c k . The p h o t o o x i d a t i o n r a t e s of thymine and u r a c i l a l s o i n c r e a s e w i t h pH (5)· R e l a t i v e l y l i t t l e i s known about the m e c h a n i s t i c d e t a i l s of the p h o t o o x i d a t i o n of p u r i n e s and p y r i m i d l n e s . T y p i c a l l y , complex a r r a y s of r e a c t i o n p r o d u c t s are formed t h a t are p r o b a b l y d e r i v e d from u n s t a b l e d i o x e t a n e s , endoperoxides or h y d r o p e r o x i d e s ( 7 , 2 1 ) . The methylene blue s e n s i t i z e d p h o t o o x i d a t i o n of guanosine r e s u l t s i n the u l t i m a t e p r o d u c t i o n of g u a n i d i n e , r i b o s e , r i b o s y l u r e a and u r e a f

f


104


f

,

f

( 4 1 ) . The Type I o x i d a t i o n p r o d u c t s of 3 , 5 - d i - 0 - a c e t y l - 2 deoxyguanosine i n c l u d e two anomers o f 3 , 5 - d i - 0 - a c e t y l - 2 - d e o x y e r y t h r o p e n t o f u r a n o s e p l u s s e v e r a l u n i d e n t i f i e d compounds. The predominant s i n g l e t oxygen o x i d a t i o n p r o d u c t s o f t h i s guanosine d e r i v a t i v e are N-(3,5-di-0-acetyl-2-deoxy-erythropentofuranosyl)c y a n u r i c a c i d and 9 - ( 3 , 5 - d i - 0 - a c e t y l - 2 - d e o x y - e r y t h r o p e n t o f u r a n o s y l ) 4,8-dihydro-4-hydroxy-8-oxoguanine ( 3 7 ) . The primary p h o t o o x i d a t i o n product o f u r a c i l , as determined a t v e r y low temperatures, appears t o be a v e r y u n s t a b l e h y d r o p e r o x i d e ( 4 2 ) .


1

,

,

Photodynamic E f f e c t s on N u c l e i c A c i d s . N u c l e i c a c i d s a r e p h o t o o x i d i z e d on i l l u m i n a t i o n i n the presence of a number o f d i f f e r e n t k i n d s of p h o t o s e n s i t i z e r s ; i n e s s e n t i a l l y a l l c a s e s , photodynamic treatment o f n u c l e i c a c i d s and s y n t h e t i c p o l y n u c l e o t i d e s p r e f e r e n t i a l l y d e s t r o y s guanine r e s i d u e s ( 5 , 3 7 ) . For example, i t has been shown t h a t h e m a t o p o r p h y r i n , which does n o t i n t e r c a l a t e i n t o n u c l e i c a c i d s , s p e c i f i c a l l y s e n s i t i z e s the p h o t o a l t e r a t i o n of guanine r e s i d u e s i n s i n g l e - s t r a n d e d DNA; subsequent treatment w i t h base r e s u l t s i n c h a i n breaks a t each guanine r e s i d u e . Methylene b l u e , which, l i k e o t h e r b a s i c dyes i n t e r c a l a t e s i n t o the n u c l e i c a c i d h e l i x , s p e c i f i c a l l y s e n s i t i z e s the p h o t o a l t e r a t i o n of guanine r e s i d u e s i n both s i n g l e - s t r a n d e d and d o u b l e - s t r a n d e d DNA. A l t h o u g h the hematoporphyrin r a d i c a l a n i o n i s produced i n good y i e l d on i l l u m i n a t i o n i n the presence o f DNA, i t does not i n t e r a c t w i t h the n u c l e i c a c i d . S i n g l e t oxygen appears t o be the r e a c t i v e s p e c i e s w i t h both hematoporphyrin and methylene b l u e (43) . I n c o n t r a s t , photodynamic treatment of DNA w i t h rose bengal (44) o r w i t h r i b o f l a v i n (45) generates s i n g l e - s t r a n d c h a i n b r e a k s , a p p a r e n t l y by i n t e r a c t i o n of the t r i p l e t s e n s i t i z e r s w i t h t h e n u c l e i c a c i d . S i n g l e t oxygen does not appear t o be i n v o l v e d . Superoxide and hydrogen p e r o x i d e have a l s o been suggested as being r e a c t a n t s i n the photodynamic d e g r a d a t i o n o f n u c l e i c a c i d s ( 4 6 ) . I n a d d i t i o n t o s t r a n d breakage, p h o t o d y n a m i c a l l y - t r e a t e d n u c l e i c a c i d s show c o n f o r m a t i o n a l a l t e r a t i o n s , s p e c t r a l s h i f t s , a decrease i n s o l u t i o n v i s c o s i t y and m e l t i n g temperature, and an i n c r e a s e d s u s c e p t i b i l i t y t o enzymatic d i g e s t i o n (5). Major changes i n b i o l o g i c a l a c t i v i t y a l s o o c c u r . F o r example, tobacco mosaic v i r u s RNA l o s e s i t s a b i l i t y t o i n f e c t tobacco p l a n t s , DNA t r a n s f o r m i n g p r i n c i p l e from b a c t e r i a i s d e s t r o y e d , and t r a n s f e r RNA i s i n a c t i v a t e d ; f u r t h e r , the messenger, template and t r a n s l a t i o n a l a c t i v i t i e s of n u c l e i c a c i d s a r e a l t e r e d (5,46,47). M u t a t i o n s can be produced i n b a c t e r i o p h a g e DNA by photodynamic treatment ( 4 8 ) . Photodynamic E f f e c t s on M i s c e l l a n e o u s B i o m o l e c u l e s . In addition to the major c a t e g o r i e s d e s c r i b e d above, a number of o t h e r k i n d s o f b i o m o l e c u l e s a r e s e n s i t i v e t o photodynamic a t t a c k (_1_). F o r example, ascorbic acid i s photooxidized with porphyrin s e n s i t i z e r s ; the a s c o r b a t e f r e e r a d i c a l i s produced i n the r e a c t i o n ( 4 9 ) . The p l a n t hormone, i n d o l e - 3 - a c e t i c a c i d , i s p h o t o o x i d i z e d u s i n g FMN; competing Type I and Type I I p r o c e s s e s a r e i n v o l v e d ( 5 0 ) . E o s i n Y and methylene b l u e s e n s i t i z e the p h o t o o x i d a t i o n o f a l p h a - k e t o g l u t a r i c a c i d i n a s i n g l e t oxygen mediated p r o c e s s ; s u c c i n i c a c i d and carbon d i o x i d e a r e produced i n the r e a c t i o n ( 5 1 ) . The i l l u m i n a t i o n o f p h y t o l i n the presence of rose bengal o r methylene b l u e g i v e s two



6.

SPIKES AND STRAIGHT


105

a l l y l i c h y d r o p e r o x i d e s i n a r e a c t i o n i n v o l v i n g s i n g l e t oxygen (52)· Squalene i s p h o t o o x i d i z e d w i t h c h l o r p r o m a z i n e v i a a s i n g l e t oxygen r e a c t i o n w i t h the f o r m a t i o n of p e r o x i d i z e d p r o d u c t s ( 5 3 ) . The f l a v a n o l , q u e r c e t i n , i s s l o w l y p h o t o o x i d i z e d i n a s e l f s e n s i t i z e d p r o c e s s , as w e l l as i n a r e a c t i o n s e n s i t i z e d by r i b o f l a v i n . The r a t e of the f l a v i n e - s e n s i t i z e d p h o t o o x i d a t i o n i s i n c r e a s e d 1 0 - f o l d i n the presence of EDTA i n a r e a c t i o n i n h i b i t e d by superoxide dismutase, s u g g e s t i n g t h a t the process i s mediated, at l e a s t i n p a r t , by s u p e r o x i d e ( 5 4 ) . V i t a m i n Ε ( a l p h a - t o c o p h e r o l ) r e a c t s w i t h s i n g l e t oxygen produced by photodynamic s e n s i t i z e r s by a r a p i d p h y s i c a l quenching p r o c e s s , and by a s l o w e r , i r r e v e r s i b l e r e a c t i o n t h a t g i v e s two i s o m e r i c hydroperoxydienones ( 5 5 ) . The i l l u m i n a t i o n of v i t a m i n Ε i n the presence of hematoporphyrin d e r i v a t i v e l e a d s to the uptake of oxygen and the f o r m a t i o n of the v i t a m i n Ε chromanoxyl f r e e r a d i c a l ( 5 6 ) . Photodynamic treatment of v i t a m i n B12 w i t h methylene b l u e as s e n s i t i z e r r e s u l t s i n two photooxygenated p r o d u c t s ( 5 7 ) . I l l u m i n a t i o n of n a t u r a l pheomelanin pigments and model m e l a n i n s r e s u l t s i n a slow uptake of oxygen; the r a t e i s g r e a t l y enhanced by added rose bengal i n a r e a c t i o n t h a t appears to i n v o l v e s i n g l e t oxygen, at l e a s t i n p a r t . Rose bengal a l s o s e n s i t i z e s an i n c r e a s e i n the p h o t o p r o d u c t i o n of f r e e r a d i c a l s i n melanins (58)· B i o c h e m i s t r y of Photodynamic R e a c t i o n s

i n C e l l s and

Organelles

I n f o r m a t i o n o b t a i n e d on p h o t o s e n s i t i z e d r e a c t i o n s i n s o l u t i o n s t u d i e s cannot always be a p p l i e d d i r e c t l y to s t u d i e s w i t h c e l l s . T h i s i s because c e l l s and s u b c e l l u l a r s t r u c t u r e s are nonhomogeneous, w i t h r e g i o n s t h a t d i f f e r w i d e l y i n c h e m i c a l makeup. Thus c e l l s p r o v i d e a l a r g e range of microenvironments w i t h d i f f e r e n t p h y s i c o c h e m i c a l p r o p e r t i e s . As a r e s u l t , the p h o t o s e n s i t i z i n g p r o p e r t i e s of s e n s i t i z e r s can depend on t h e i r p a r t i c u l a r c e l l u l a r environment; s i m i l a r l y the r e a c t i o n s of s u b s t r a t e s may be d i f f e r e n t i n d i f f e r e n t r e g i o n s of the c e l l . Most types of b i o m o l e c u l e s i n i n t a c t c e l l s and i n i s o l a t e d c e l l u l a r o r g a n e l l e s show the same k i n d s of b i o c h e m i c a l changes on photodynamic treatment as observed i n s o l u t i o n ( 1 , 2 ) . For example, s u s c e p t i b l e amino a c i d r e s i d u e s i n c e l l membrane p r o t e i n s are p h o t o o x i d i z e d e f f i c i e n t l y ( 1 , 5 9 ) . T h i s r e s u l t s i n the photodynamic i n a c t i v a t i o n of a number of membrane a s s o c i a t e d enzymes i n c l u d i n g glyceraldehyde-3-phosphate dehydrogenase, ATPases, a c e t y l c h o l i n e s t e r a s e , e t c . Enzymes a s s o c i a t e d w i t h m i t o c h o n d r i a , such as s u c c i n i c dehydrogenase, ATPase, and a d e n y l a t e k i n a s e are a l s o i n a c t i v a t e d e f f i c i e n t l y w i t h some s e n s i t i z e r s ( 6 0 ) ; among o t h e r e f f e c t s , t h i s may r e s u l t i n decreased l e v e l s of ATP i n t r e a t e d c e l l s , which can i n t e r f e r e w i t h a number of d i f f e r e n t c e l l u l a r a c t i v i t i e s (61) · S o l u b l e enzymes i n the c y t o s o l of the c e l l are a l s o s e n s i t i v e . I l l u m i n a t i o n of p h o t o s e n s i t i z e d c e l l membranes, e.g., red blood c e l l g h o s t s , i n the presence of p o r p h y r i n s , g i v e s a s i n g l e t oxygen-mediatd p e r o x i d a t i o n of the membrane l i p i d s ; the r a t e of p e r o x i d a t i o n i s s i g n i f i c a n t l y i n c r e a s e d by low c o n c e n t r a t i o n s of a s c o r b a t e ( 6 2 ) . The photodynamic treatment of i s o l a t e d microsomes r e s u l t s i n the p e r o x i d a t i o n of the component l i p i d s and i n the i n a c t i v a t i o n of the mixed f u n c t i o n o x i d a s e system. I l l u m i n a t i o n of


106


h e p a t i c microsomes from r a t s p r e t r e a t e d w i t h hematoporphyrin d e r i v a t i v e r e s u l t s i n a r a p i d d e s t r u c t i o n of cytochrome P-450 ( 6 3 ) . As i n s o l u t i o n , s e n s i t i z e d p h o t o c r o s s - l i n k i n g r e a c t i o n s o c c u r w i t h b i o m o l e c u l e s i n c e l l o r g a n e l l e s and i n i n t a c t c e l l s . A c t u a l l y , such r e a c t i o n s may be f a v o r e d i n c e l l s as compared to s o l u t i o n systems because of the h i g h l y o r d e r e d s t r u c t u r e of c e l l s ( 6 4 ) . DNA s t r a n d breaks occur i n murine f i b r o b l a s t c e l l s i l l u m i n a t e d i n the presence of hematoporphyrin d e r i v a t i v e ; t h i s a p p a r e n t l y r e s u l t s from the p h o t o o x i d a t i o n of guanine r e s i d u e s i n the n u c l e i c a c i d ( 6 5 ) .


Summary We now understand the i n i t i a l r e a c t i o n s i n v o l v e d i n the b i o c h e m i s t r y of photodynamic a c t i o n r e a s o n a b l y w e l l , i . e . , the p r o d u c t i o n and p r o p e r t i e s of the e x c i t e d s t a t e s o f s e n s i t i z e r s and the i n t e r a c t i o n of t r i p l e t s e n s i t i z e r s w i t h ground s t a t e oxygen to g i v e s i n g l e t oxygen. The i n t e r a c t i o n of s i n g l e t oxygen w i t h b i o m o l e c u l e s i s becoming c l e a r e r , but the r e a c t i o n s of t r i p l e t s e n s i t i z e r s w i t h b i o l o g i c a l s u b s t r a t e s v i a f r e e r a d i c a l p r o c e s s e s are more complex. Much remains to be l e a r n e d about the m e c h a n i s t i c o r g a n i c c h e m i s t r y of these r e a c t i o n s . F i n a l l y , a l t h o u g h p r o g r e s s i s being made, our u n d e r s t a n d i n g of p h o t o s e n s i t i z e d r e a c t i o n s at t h e c e l l u l a r and o r g a n i s m a l l e v e l s i s s t i l l v e r y i n c o m p l e t e . There i s much work yet to be done on the b i o c h e m i s t r y of photodynamic a c t i o n . Acknowledgments. The p r e p a r a t i o n of t h i s r e v i e w was supported i n p a r t by American Cancer S o c i e t y Grant #PDT-259A, by the V e t e r a n s A d m i n i s t r a t i o n M e d i c a l Research Program, and by the O f f i c e of N a v a l R e s e a r c h , C o n t r a c t No. N00014-88-K-0285. Literature Cited 1. 2. 3. 4. 5. 6. 7.

8.

9. 10. 11. 12.

Spikes, J.D. In Photoimmunology; Parrish, J . Α . ; Kripke, M.L.; Morison, W.L., Eds.; Plenum: New York, 1983; Chapter 2. Spikes, J.D. In The Science of Photomedicine; Regan, J . D . ; Parrish, J . Α . , Eds.; Plenum: New York, 1982; Chapter 5. Tappeiner, H. v. Ber. Deut. Chem. Ges. 1903, 36, 3035. Blum, H.F. Photodynamic Action and Diseases Caused by Light; Hafner Publishing Company: New York, 1964. Straight, R.C.; Spikes, J.D. In Singlet O ; Frimer, Α.Α., Ed.; CRC Press: Boca Raton, 1985; Vol IV, Chapter 2. Foote, C.S. In Free Radicals in Biology; Pryor, W.A., Ed.; Academic: New York, 1976; Vol II, Chapter 3. Foote, C.S. In Oxygen and Oxy-Radicals in Chemistry and Biology; Rodgers, M.A.J.; Powers, E . L . , Eds.; Academic: New York, 1981; p 425. Foote, C.S. In Porphyrin Localization and Treatment of Tumors; Doiron, D.R.; Gomer, C.J., Eds.; Alan R. Liss: New York, 1984; p 3. Laustriat, G. Biochimie 1986, 68, 771. Towers, G.H.N. Prog. Phytochem. 1980, 6, 1983. Andley, U.P.; Chakrabarti, B. Biochem. Biophys. Res. Commun. 1983, 115, 894. Terao, J.; Matsushita, S. Agric. Biol. Chem. 1981, 45, 601. 2


6. SPIKES AND STRAIGHT 13. 14. 15. 16. 17. 18.


19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39.

40. 41.


107

Frimer, Α.Α.; Stephenson, L.M. In Singlet O ; Frimer, A . A . , Ed.; CRC Press: Boca Raton, 1985; Vol II, Chapter 3. Teng, J.I.; Smith, L . L . J. Am. Chem. Soc. 1973, 95, 4060. Jasiczak, J.; Smoczkiewica, M.A. Tetrahedron Lett. 1985, 26, 5221. Sedee, A.G.J.; Beijersbergen van Henegouwen, G.M.J.; Lusthof, K . J . ; Lodder, G. Biochem. Biophys. Res. Commun. 1984, 125, 675. Sedee, Α.; Vanhenegouwen, G.B. Arch. Pharm. 1985, 318, 111. Ando, W.; Takata, T. In Singlet O ; Frimer, Α.Α., Ed.; CRC Press: Boca Raton, 1985; Vol III, Chapter 1. Buettner, G.R. FEBS Lett. 1985, 177, 295. Gennari, G.; Cauzzo, G.; Jori, G. Photochem. Photobiol. 1974, 20, 497. Wasserman, H.W.; Lipshutz, B.H. In Singlet Oxygen; Wasserman, H.W.; Murray, R.W., Eds.; Academic Press: New York, 1979; Chapter 9. Sysak, P.K.; Foote, C.S.; Ching, T-Y. Photochem. Photobiol. 1977, 26, 19. Bowen, J.R.; Yang, S.F. Photochem. Photobiol. 2975, 21, 201. George, M.V.; Bhat, V. Chem. Rev. 1979, 79, 447. Nakagawa, M.; Yokoyama, Y.; Kato, S.; Hino, T. Tetrahedron 1985, 41, 2125. Ishimitsu, S.; Fujimoto, S.; Ohara, A. Chem. Pharm. Bull. 1985, 33, 1552. Rizzuto, F.R.; Spikes, J . D . ; Coker, G.D. Photobiochem. Photobiophys. 1986, 10, 149. Straight, R.C.; Spikes, J.D. Photochem. Photobiol. 1978, 27, 565. Jori, G.; Galiazzo, G.; Tamburro, A.M; Scoffone, E. J . Biol. Chem. 1970, 245, 3375. Jori, G. An. Acad. Bras. Cien. 1973. 45, 33. Rippa, M.; Pontremoli, S. Arch. Biochem. Biophys. 1969, 103, 112. Hopkins, T.R.; Spikes, J.D. Photochem. Photobiol. 1970, 12, 175. Brandt, J. Methods Enzymol. 1977, 46, 561. Verweij, H.; Dubbleman, T.M.A.R.; Van Steveninck, J . Biochim. Biophys. Acta. 1981, 647, 87. Helene, C. In Aging, Carcinogenesis and Radiation Biology; Smith, K . C . , Ed.; Plenum Press: New York, 1976; p 149. Hemmendorf, B.; Brandt, J.; Anderson, L.-O. Biochim. Biophys. Acta. 1981, 667, 15. Cadet, J.; Berger, M.; Decarroz, C.; Wagner, J.R.; Van Lier, J . E . ; Ginot, Y.M.; Vigny, P. Biochemie 1986, 68, 813. Jori, G.; Spikes, J.D. In Topics in Photomedicine; Smith, K.C., Ed.; Plenum Press: New York, 1984; p 183. Cadet, J.; Decarroz, C.; Voituriez, L . ; Gaboriau, F . ; Vigny, P. In Oxygen Radicals in Chemistry and Biology; Bors, W.; Saran, M.; Tait, D., eds.; Walter de Gruyter: Berlin, 1984; p 485. Ennever, J . F . ; Speck, W.T. Pediatr. Res. 1981, 15, 956. Matsuura, T.; Saito, I. General Heterocyclic Chem. 1976, 4, 456. 2

2


108



42. 43.

Vickers, R.S.; Foote, S. Boll. Chim. Farm. 1970, 109, 599. Kawanishi, S.; Inoue, S.; Sano, S.; Alba, H. J . Biol. Chem. 1986, 261, 6090. 44. Peak, M.J.; Peak, J . G . ; Foote, C.S.; Krinsky, N.I. J . Photochem. 1984, 25, 309. 45. Korycka-Dahl, M.; Richardson, T. Biochim. Biophys. Acta. 1980, 610, 229. 46. Amagasa, J. Photochem. Photobiol. 1981, 33, 947. 47. Spikes, J.D.; MacKnight, M.L. In Photochemistry of Macromolecules; Reinisch, R . F . , Ed.; Plenum Press: New York, 1970; p 67. 48. Piette, J.; Calberg-Bacq, D.M.; Van de Vorst, A. Mol. Gen. Genet. 1978, 167, 95. 49. Buettner, G.R.; Need, M.J. Cancer Lett. 1985, 25, 297. 50. Miyoshi, N.; Fukuda, M.; Tomita, G. Photobiochem. Photobiophys. 1986, 11, 57. 51. Gandhi, P.; Dubey, R.; Bokadia, M.M.; Sharma, T.C. Curr. Sci. 1985, 54, 37. 52. Mihara, S.; Tateba, H. J . Org. Chem. 1986, 51, 1142. 53. Fujita, H.; Matsuo, I.; Okazaki, M.; Yuoshino, K.; Ohkido, M. Dermatol. Res. 1986, 278, 224. 54. Takahama, U. Photochem. Photobiol. 1985, 42, 89. 55. Clough, R.L.; Yee, B.G.; Foote, C.S. J . Am. Chem. Soc. 1979, 101, 683. 56. Buettner, G.R. In Primary Photo-Processes in Biology and Medicine; Bensasson, R.V.; Jori, G.; Land, E.J.; Truscott, T . G . , Eds.; Plenum: New York, 1985; p 341. 57. Kraeutler, B.; Stepanek, R. Agnew. Chem. 1985, 97, 71. 58. Sarna, T.; Menon, I . Α . ; Sealy, R.C. Photochem. Photobiol. 1985, 42, 529. 59. Moan, J.; Vistnes, A . I . Photochem. Photobiol. 1986, 44, 15. 60. Fu, N.; Yeh, S.; Chang, C.; Zhao, X.; Chang, L . Adv. Exp. Med. Biol. 1985, 193, 161. 61. Hilf, R.; Murant, R.S.; Narayanan, U.; Gibson, S.L. Cancer Res. 1986, 46, 211. 62. Girotti, A.W.: Thomas, J . P . ; Jordan, J . E . Photochem. Photobiol. 1985, 41, 267. 63. Das, M.; Dixit, R.; Mukhtar, H.; Bickers, D.R. Cancer Res. 1985, 45, 608. 64. Jori, G.; Spikes, J.D. In Oxygen and Oxy-Radicals in Chemistry and Biology; Rodgers, M.A.J.; Powers, E . L . , Eds.; Academic Press: New York, 1981; p 441. 65. Dubbelman, T.M.A.R.; Boegheim, J . P . J . ; Van Steveninck, J . In Primary Photo-Processes in Biology and Medicine; Bensasson, R.V.; Jori, G.; Land, E.J.; Truscott, T . G . , Eds.; Plenum: New York, 1985; p 397. RECEIVED February 11, 1987


Biochemistry of Photodynamic Action - ACS Symposium Series (ACS

Recommend Documents