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Biochemistry problem

  • 29-10-2010 11:29am
    #1
    Wailin
    Registered Users, Registered Users 2 Posts: 4,439 ✭✭✭


    Hey all,
    Im a student in DIT and am wondering can anyone help me with a biochemistry problem.:mad:!!
    In a lab experiment we had to calculate the extinction coefficient of three compounds, blue dextran, NADH and hemoglobin in 1mol/solution, 1 mg/ml solution and for 1%w/v solution.
    Take hemoglobin as an example...we had to dilute the stock solution(15ml of 0.039mM) to produce 10ml of a 0.5mg/ml solution(using saline). I was able to calculate the 1mol/solution by getting the molarity (0.5/64500) and then using the Beer-Lambert Law A=elC, which I think was right(???!!)
    But how do I calculate the extinction coefficient in 1mg/ml and 1% w/v solution? Any help would be greatly appreciated.


Comments

  • #2
    cianl1
    Closed Accounts Posts: 336 ✭✭cianl1


    You're using a spectrophotometer right? Determine the concentration of the two solutions, measure their absorbances in the spectrophotometer and rearrange the Beer-Lambert law for e. Standard stuff.


  • #3
    Wailin
    Registered Users, Registered Users 2 Posts: 4,439 ✭✭✭Wailin


    Standard stuff yes but I dont think you read my question correctly. The hemoglobin was diluted to 10ml of a 0.5mg/ml solution. In the spectrophotometer its absorbance was 2.5. So I have A=2.5, im looking for e, l is 1cm obviously but im confused as to what C is when im asked to find extinction coefficient of a 1mg/ml solution.


  • #4
    cianl1
    Closed Accounts Posts: 336 ✭✭cianl1


    Well, 1mg/ml is the same as 1g/L, so we have 10ml of a 0.5g/L solution then. Divide by the molar mass of haemoglobin which is about 64458 g/mol according to t'internet (i.e. don't be upset if your answer is a bit off) and that gives mol/L.


  • #5
    Improbable
    Registered Users, Registered Users 2 Posts: 1,576 ✭✭✭Improbable


    Wailin wrote: »
    Standard stuff yes but I dont think you read my question correctly. The hemoglobin was diluted to 10ml of a 0.5mg/ml solution. In the spectrophotometer its absorbance was 2.5. So I have A=2.5, im looking for e, l is 1cm obviously but im confused as to what C is when im asked to find extinction coefficient of a 1mg/ml solution.

    For the simplified Beer-Lambert Law, given that you know the concentrations in one form or another, all you have to do is convert them into moles per litre and use that value for C. E, the extinction coefficient is then given in Litres per mole per cm.


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