12345AW
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What aspect of a stains chemistry gives it its colour?
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macpatgh-Sheldon
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Hi not an easy Q - sorry no-one has managed to help u for so long!
Let Sheldon come to your rescue!

1. pH can be a relevant chemical aspect of staining of biological specimens - eosin & methylene blue give tissues/cells their characteristic colours cos they inhibit some bacteria but also form a precipitate at low pH.
2. A common stain used in histopathology [sorry more than in microbiology] is H & E [haematoxylin + Eosin] - please google it for possibly useful info.
3. Relevant to your subject is oc the Gram stain - the purple crystal violet-iodine complex in this stain is retained by Gram +ve bacteria cos the thick peptidoglycan cell wall causes retention of the dye so the cells appear purple under the light microscope.

WHEREAS:
In Gram -ve bacteria, the dye is "leached" out of the cell, so the cell would appear colourless except that the safranin in the Gram stain affords it a red colour.
To understand the chemistry/biochemistry of why crystal violet/iodine complex is purple is outside the scope of even Sheldon

SO I KINDLY ASK randombiochemist - thank you in advance man!



4. Hydrolysis of PYR to release free naphthylamide is shown up as red by adding a drop of dimethylaminocinnamaldehyde in the detection of group A beta-haemolytic streptococci [the antibodies produced by the human immune system against this bacterium cross-react with cardiac tissue in rheumatic fever, leading some years later to valvular disease e.g. aortic stenosis].

Be safe!
M.
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12345AW
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#3
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Thank you so much!!! this really helped
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macpatgh-Sheldon
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#4
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(Original post by 12345AW)
Thank you so much!!! this really helped
My pleasure Amy Wendy OR Andy Will - thanks for the rep!
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