[RASMB] Hb tetramer

[Walter Stafford]

Mitra,
    It is also possible to get a slightly low f/fo (sometimes less than 
1.0)  if there is a small amount of unaccounted for self-association 
going on.
Walter

John Philo wrote:
> Mitra,
>  
> My recollection is that IHP does cause a slight compaction of the 
> structure, but I agree with Arthur that 1.08 sounds a bit low. I'm 
> wondering whether that might be because you are not using an accurate 
> vbar value. I wasn't doing AUC back in the dark ages when I worked on 
> hemoglobin, but I vaguely recall that the additivity rule for vbar may 
> not work well for heme + globin. I think you will find the 
> experimental vbar in hemoglobin AUC papers by Stuart J. Edelstein (? 
> '60s-'70s).
>  
> John
>
> ------------------------------------------------------------------------
> *From:* rasmb-bounces at rasmb.bbri.org 
> [mailto:rasmb-bounces at rasmb.bbri.org] *On Behalf Of *Arthur Rowe
> *Sent:* Wednesday, February 04, 2009 6:45 AM
> *To:* mitrana at mail.utexas.edu; rasmb at server1.bbri.org
> *Subject:* Re: [RASMB] Hb tetramer
>
>     Hi Mitra
>
>     An f/f0 value of 1.08 (±?) is low-ish, but within the ball park
>     range for 'globular' proteins. I don't imagine that 2 mM Inositol
>     would affect the (properly and fully corrected) s value.
>
>     Regards
>
>     Arthur
>
>
>     Hello All
>     Two questions, related ones -
>
>     1. Is a S20,w value of 5.01 too high for a DEOXY Hb tetramer of
>     67180  
>     Da MW? This gives a f/f0 of around 1.08. Just a reminder that
>     deoxy Hb  
>     tetramer does not dissociate to a dimer much (dissociation
>     constant ~  
>     10^-11 M).
>
>     2. can such an anomaly occur due to Hb interactions with the  
>     components of the buffer - in this case 2 mM of Inositol  
>     hexakisphosphate (IHP)?
>
>     Glad to hear any comments and/or references to papers.
>
>     Mitra
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>
>
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