[icyhead]

Hi, im struggling with the following questions, especially with the units in the first question - and was hoping someone could help me out, thanks.

The enzyme quinol (bo3) oxidase [Molecular Weight 140 000Da] was isolated
from Escherichia coli and analysed for its metal composition using Atomic
Absorption Spectroscopy. Qualitative analysis indicates the presence of both
iron (Fe) and copper (Cu). Using electronic absorption spectroscopy, an
absorbance of 1.895 units is detected at 407nm typical of haem Fe. The
concentration of haem Fe in the enzyme is subsequently determined in a 1 ml
sample containing 1.4μg of enzyme.

(c) Assume Theta(407nm) = 91 000 M-1 cm-1 and the path length is 1 cm, use the
Beer-Lambert law to calculate the concentration of haem Fe in the enzyme
sample (in μM).

I know the Beer lambert law is  A=Theta*L*C
I need concentratoin so :  C=A/(Theta*L)
where Theta=91000 A = 1.895, L = 1  (not sure if cm is the standard unit)
C=1.895/(91000*1)
=0.0000208242 M/L
x10^3 to get = 0.0208242 uMol/L


d) Calculate how many haem Fe groups are present in the enzyme.
Absolutely no idea

(e) Discuss the role of the active site Fe-Cu in respiratory oxidases.
I should probably research this but if anyone can point me in the right direction that would be really helpful.

[Yggdrasil]

Hi, im struggling with the following questions, especially with the units in the first question - and was hoping someone could help me out, thanks.

The enzyme quinol (bo3) oxidase [Molecular Weight 140 000Da] was isolated
from Escherichia coli and analysed for its metal composition using Atomic
Absorption Spectroscopy. Qualitative analysis indicates the presence of both
iron (Fe) and copper (Cu). Using electronic absorption spectroscopy, an
absorbance of 1.895 units is detected at 407nm typical of haem Fe. The
concentration of haem Fe in the enzyme is subsequently determined in a 1 ml
sample containing 1.4μg of enzyme.

(c) Assume Theta(407nm) = 91 000 M-1 cm-1 and the path length is 1 cm, use the
Beer-Lambert law to calculate the concentration of haem Fe in the enzyme
sample (in μM).

I know the Beer lambert law is  A=Theta*L*C
I need concentratoin so :  C=A/(Theta*L)
where Theta=91000 A = 1.895, L = 1  (not sure if cm is the standard unit)
C=1.895/(91000*1)
=0.0000208242 M/L
x10^3 to get = 0.0208242 uMol/L

Multiplying mol/L give mmol/L not µmol/L.  But, otherwise the approach is correct.

d) Calculate how many haem Fe groups are present in the enzyme.
Absolutely no idea

First, you need to calculate the concentration of enzyme molecules in your sample.

(e) Discuss the role of the active site Fe-Cu in respiratory oxidases.
I should probably research this but if anyone can point me in the right direction that would be really helpful.

www.pubmed.gov is a good tool to search the scientific literature.  Wikipedia is also a good starting point, but you shouldn't rely on information there without confirming it from an independent source.

[icyhead]

Thanks, good to know i did the right calculations (nearly)