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Topic: Fluorescein rxn with Hemo and H2O2  (Read 6054 times)

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hutch1

  • Guest
Fluorescein rxn with Hemo and H2O2
« on: March 14, 2005, 09:48:21 PM »
Fluorescein (reduced by zinc) reacts with hemoglobin from trace blood smears to change forms (oxidize?) and fluoresce.  Hydrogen peroxide is also used in the process.  I cannot make sense of how the reaction all fits together.  I've searched the net with no luck.  I find sites that describe the process, but not the reaction in detail.  I have an AP chemistry student that is beating her head against the wall for an answer, but I'm too stupid (I'm her teacher) to figure out the detail.

Any help would be appreciated.  Descriptions or links to descriptions and chemical equations would be most helpful.  I'm a first time user.  Thank you.

savoy7

  • Guest
Re:Fluorescein rxn with Hemo and H2O2
« Reply #1 on: March 15, 2005, 12:37:07 AM »
I don't know if this will help -

This link describes the process - similiar to what I have done in the past -

http://www.latent-prints.com/fluorescein2.htm

it does describe both the ethanol solution tech and the aqueous solution technique

In point 5 it does describe what each reagent does.

I hope this can be some help.

savoy

hutch1

  • Guest
Re:Fluorescein rxn with Hemo and H2O2
« Reply #2 on: March 15, 2005, 09:00:35 PM »
Thanks.
I checked it out and it makes sense.  It did help me deduce a possible mechanism -- although it remains a guess that needs confirmation.  Here's my guess.  The zinc reduces the fluorescein to fluorescin (fluorescin does not fluoresce strongly under a black light), the fluorescin either binds with the hemoglobin from the blood or else only that which is in close proximity to  the blood is affected, the blood releases oxygen from the H2O2, this oxidizes the fluorescin back to the fluorescein form, and the fluorescein form produces the glow under the black light.
As you can see, there are still some fuzzy details.
I do appreciate your help with this.  Point 5 provided good information that I hadn't found anywhere else.
Thanks again.

savoy7

  • Guest
Re:Fluorescein rxn with Hemo and H2O2
« Reply #3 on: March 15, 2005, 10:44:14 PM »
Hydrogen Peroxide reacts with the catalase in the blood, releasing oxygen.

This process hasn't been worked out, but here's a paste of the possible reaction:

 The chemistry of catalase catalysis has not been precisely solved yet, but the following, which is similar to the mechanism of cytochrome c peroxidase, has been proposed. The catalytic process is thought to occur in two stages:

H2O2 + Fe(III)-E -- H2O +O=Fe(IV)-E (1)
H2O2 + O=Fe(IV)-E -- H2O + Fe(III)-E (2)

this probably confuses things, so I'll leave it at that.
savoy

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