Gareth - sorry to be complicated, but the answer to your question
is not quite as simple as you think and that is why the molar
absorptivity of Hb is not widely given. Haem species exist in a
number of different forms, which are readily interconvertable as
they come in contact with oxygen and various other substances.
That is why haemoglobin in blood for clinical purposes is usually
measured after reaction with Drabkins solution and conversion to
cyanmethhaemoglobin, which is stable and does not interconvert. If
that's what you are interested in you'll find the molar absorptivity for
cyanmethaemoglobin on the package insert that comes with, for
example, the Boehringer haemoglobin kit.
If you wish to measure haem species in an interconvertable mixture
you need to apply the simultaneous equations given below, which
were derived by K.D. Whitburn about 20 years ago from the molar
absorptivities of haem species (J Biol Chem, but I don't have the
reference to hand) (concentrations in mmol/L):
Oxyhaemoglobin concentration = 119 (Abs 577nm - 700 nm) - 39
(Abs 630 nm - 700 nm) - 89 ( Abs 560 nm - Abs 700 nm)
Methaemoglobin = 28 (Abs 577nm - 700 nm) + 307 (Abs 700 nm -
630 nm) - 55 ( Abs 560 nm - Abs 700 nm)
Ferrylhaemoglobin = -133 (Abs 577nm - 700 nm) - 114 (Abs 700
nm - 630 nm) + 233 ( Abs 560 nm - Abs 700 nm)
If this is what you're intersted in, let me know.
Nick Miller,
London
> Can anyone tell me the molar absorption coefficient for Haemoglobin?
>
> I've looked in all the usual places (Geigi etc)
>
> Thanks
>
> Gareth
>
> Senior Clinical Biochemist
> Wrexham Maelor Hospital
> Wrexham LL13 7TD
> 01978 725345 (direct)
> 01978 366520 (fax)
>
According to Hall & Malia 1986 p 112, the millimolar absorption
coefficeient of haemoglobin is 11.0
David McPherson
[log in to unmask]
[log in to unmask]
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|