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Instead of posting up all your homework questions all at once, I can point out some good resources for you. You would like info on the structure of hemoglobin: look it up in the protein databank. There you will find structures for the unbound form (PDB ID: 2hhb) and the oxygen bound form (PDB ID: 1hho) and the research papers in which these structures were published. The protein data bank can be found at http://www.rcsb.org.
You can find a lot more info at www.uniprot.org. The Uniprot accession number for the alpha subunit is P01942 and accession number for the beta subunit is P02075.
Or, as hemoglobin is such a commonly discussed protein, you can find good discussions in "Molecular Cell Biology" by Lodish and friends, a less detailed description in "Biology" by Campbell/Reece and a more detailed discussion in "Introduction to Protein Structure" by Tooze. These are all classic texts in biology and your library should have them.
If I were you, I'd start with the online resources. Happy hunting.
Esmail, go to www.rcsb.org. This is called the protein data bank and it is a searchable database of protein structures. It's what real scientists do when they want structural info on proteins.
There is a search box at the top of the page. Into that, put the PDB ID numbers I looked up for you - 1HHO for hemoglobin not bound to oxygen and 2HHB for hemoglobin which is bound to an oxygen molecule. You will have to do separate searches for both molecules.
That will give an image of the protein and some basic info about how the structure was solved. It will also give you a box with a link to the article was found. That will be the field "PubMed" followed by a number which is a link. The Protein Data Bank will also give you a number of citations for other relative articles and reviews or, if you go the PubMed way, you can get links for articles which cite the initial structural research.
You can also search on www.uniprot.org. I put the accession (i.e., reference) numbers for the protein in my response. You can also type in "hemoglobin" but be prepared to sort through the list of hits until you come up with "human." Although for general functional purposes, any old hemoglobin would probably do just as well.
After you do this, you will get all the info you want about structural levels, sequences and biologic activity you want - and links to more.
I'll even look out links to the Protein Data Bank and Uniprot for you: