Procesos que Intervienen en la Retención de Arsénico en Humedales

4—

12 K

5K

succinate

200

2

002

A com parison o f th e f u l l y o x i d is e d , s u c c i n a t e redu ced , and d i t h i o n i t e redu ced sam ples w ith sam ples p o ise d a t v ario u s red o x p ot e n t i a l s pro vid e s a d d i t i o n a l i n f orm a tio n ( F i g . 4 , 1 0 a ), The f er r e d o xi n s i g n a l from a sam ple p o ise d a t low redox p ot e n t i a l (<-400 mV), had a p pro xim a te ly th e same te m p erature p r o fi l e as th e d i t h i o n i t e reduced c a s e . The f er r e d o xi n s i g n a l from a sam ple p o ise d a t approx. -200 mV, behaved s i m i l ar l y to t h e s u c c i n a te redu ced sam ple. However, a sample p o ise d a t around -80 mV had a te m p erature dependence more a kin to th e d i t h i o n i t e reduced sam ple, i . e . i t had a more r a pid r e l a x at i o n r at e th a n th e s u c c i n a te redu ced ( or -200 mV p o ise d ) sam p le, A s i m i l ar e f f ec t was s e e n to a l e s s er d eg ree i n th e b e h a v io ur of th e HiPIP c e n tr e (F i g . 4 , 1 0 b ), as t h i s s p e c i e s behaved s i m i l ar l y i n th e f u l l y o x id is e d sam ple and th e more p o si t i v e l y p o ise d redox t i tr at i o n sam ples (> +100 mV). However, when p oise d a t a p pro xim ate ly -50 mV th e te m p erature p r o fi l e , a t low er te m p erature s , shows a g r e at er sig n a l h e ig h t ( t h e r e l a x at i o n r at e i n cr e a s e s , F i g . 4 ,1 0 ) . I n c l u s i o n of some o f FR1 gz i n th e s ig n a l h e ig h t may c o n tri b u t e to th e i n cr e a s e i n s ig n a l h e ig h t a t th e s e lower te m p erature s . These phenomena ar e r e l at e d to changes i n th e s a t ur at i o n pr o p e rt i e s of th e c e n tr e (c h ar ac t eri s e d by P I/2 ) and s u g g e ste d an i n t er ac t i o n b etw een t h i s s p e c i e s , which had i t s r e l a x at i o n r at e enhanced and a second s p e c i e s , th e l a t t er i n tr o du c in g a s p i n - l a t t i c e r e l a x at i o n term (T g ). The most co m p ellin g pro p o sa l i s t h a t th e H iPIP and FR1 were enhanced by I n t er ac t i o n w ith each

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The te m p erature p r o fi l e s o f th e e . p .r , si g n a l s from membranes p oise d a t v ari o u s p o t e n t i a l s ar e shown, ( a ): th e f er r e d o xi n s i g n a l from v ari o u s sam p les. The p o t e n t i a l i s shown a d ja c e n t t o th e pr o fi l e s o f s ig n a l h e ig h t (p eak t o peak, g = 1 .9 3 ) v ersu s i n v er s e te m p erature , ( b ): th e HiPIP s i g n a l from v ario u s sam p les, th e redox p ot e n t i a l i s shown a d ja c e n t t o th e pr o fi l e s o f th e s i g n a l h e ig h t (p eak t o b a s e l i n e , G = 2 .0 1 ) v ersu s th e i n v er s e te m p erature . The e x p erim e n ta l c o n d i t i o n s were as d e scri b e d f or fi g . 4.1 a , e x c ep t r ec e i v er 5 4 g ai n was 1,0 x 10 (a ) and 5.0 x 10 ( b ) , th e pr ot e i n c o n c e n tr at i o n was 42mg/ml.

Ferredoxin