Transferrin is the iron-transport protein found in blood. It has a molecular mas

Question

Transferrin is the iron-transport protein found in blood. It has a molecular mass of 81000 and carries two Fe3+ ions. Desferrioxamine B is potent iron chelator used to treat patient with iron overload. It has a molecular mass of 650 and can bind one Fe3+. Desferrioxamine can take iron from many sites within the body and is excreted (with its iron) through the kidneys. The molar absorptivities of these compounds are given in the following table. Both compounds are colorless (no visible absorption) in the absence of iron.

                                                               e (M-1 cm-1)                    

l (nm)                           Transferrin            Desferrioxamine

428                          3540                   2730

470                          4170                   2290       

  (a) A solution of transferrin has an absorbance of 0.463 at 470 nm in a 1.000 cm cell. Find the concentration of transferrin in mg/mL and the concentration of iron in g/mL.

(b) After addition of desferrioxamine (which dilutes the sample), the absorbance at 470 nm was 0.424 and the absorbance at 428 nm was 0.401. Calculate the fraction of iron in transferrin. Remember that transferrin binds two Fe3+ ions and desferrioxamine binds only one.

Explanation / Answer

the beer-lambert law gives

A=ecl

A=absobance

e=molar extincton coefficient

c=conc in mol/L

l=path length in /cm

a)

0.463 = 1X4170Xc

c= 1.11x10^-4 mol/l

in mg/mL=>

1110 x10^-4 mg/1000 mL= 0.11 mg/1000 ml =1.11x10^-4 mg/ml

concentration of Fe= 111.7/81000 x 1.11 x10^-4

= 1.53x10^-7 mg/ml = 1.53 x 10^-4 microg/ml

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