چكيده لاتين :
Background: Possibility to trace-label albumin with isotopes
results in information concerning its synthesis, breakdown, and
distribution in the intra and extra cellular spaces. The iodination
of albumin is a widespread procedure used in scientificstudies,
Bromine not only is more reactive and less expensive than iodine,
but bonds more easily with many elements. Therefore, it
could be a suitable tracer in labeling procedures. The present
study was designed to represent a method for labeling human
serum albumin (HSA) with stable isotope of bromine.
Methods: In the present study, the labeling of HSA by use of
stable isotope of bromine C9Br) has been sought through a series
of preliminary experiments including iodination of bovine
serum albumin (BSA) and iodination and bromination of BSA.
The experiments were basically designed according to that of
Me Conahey and Dixon in 1966. All measurements have been
obtained by inductive coupled plasma mass spectrometry
(ICPIMS). Twenty protein solutions, each having 50 mg HSA
dissolved in 10 ml of 0.05 M buffer (pH 7.0) were prepared. A
series of calculated amounts of pure bromine was added directly
to each sample. Each sample was placed in a crystallizing dish
containing crushed ice to keep the reactants cold. After dialysis
and final preparation of the samples, the intensities of bromine
in the samples were measured.
Results: Data indicated the maximum presence of bromine in
HSA samples in a ratio of 40 atoms of bromine to each mole
of HSA. After dialysis, sample analysis showed that on average,
about 65% of the bromine was really bound to the HSA
molecules. This finding indicates that about 26 atoms of bromine
were bound to each HSA molecule . Data analyzed by
simple linear regression method. Results showed that each ug
increase in dose leads to 0.002 unit increase in the mean of
mole ratio of pure bromine (Br2)/HSA (P=0.001).
Conclusion: The present study has unique specifications in
that almost all of the labeling procedures of plasma proteins
have used other elements rather than bromine and mostly radioactive
isotopes instead of stable isotopes. The present paper
showed a method for about minimum as well as maximum
bromination of HSA (0.05 atoms- 26 atoms) , within certain
limits of experimental conditions. By this method, one can
exactly determine how much bromine should be used to obtain
a certain desired mole ratio of Br2/HSA with no, or at least
minimal, alteration of protein behavior.
