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Cytochrome f- VIS spectrum

Nick Fisher nef at mole.bio.cam.ac.uk
Thu Jun 1 18:13:25 EST 1995

In article <D9I42K.KJL at cyf-kr.edu.pl>, ubziobro at jetta (Rafal Ziobro) wrote:

>         I have recently measured some spectra of thylakoids suspension
> ascorbate reduced- ferricyanide oxidized. As I know cytochrome f
> should have a maximum at 554 nm, but my results are slightly different.
> The maximum is shifted about 3-4 nm to higher wavelenghts.
>         Is there a reasonable explanation of this fact?
> I would appreciate any suggestion (maybe this are some ascorbate
> reducable thylakoid components visible in that region which I do not know). 
>         Thanks in advance

It sounds like you're observing the spectrum of cyt b-559 there. b6 isn't
reduced by ascorbate.  reduced b-559 has absorption maxima at 559, 530 and
429 nm (at room temp). It may be worth checking the wavelength calibration
of your monochromator too ;) Cytochrome b3 also has an alpha band at 559
nm and is ascorbate reducible, although it's very unlikely to be in your
thylakoid suspension. b3 is a curious protein and very little is known
about it. It's
water soluble and doesn't appear to be located in the chloroplast and so
is unlikely to present in your sample.

Nick Fisher
Biochemistry Dept.
Cambridge University

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