1. Fetal hemoglobin differs from adult hemoglobin in have two gamma chains instead of two beta chains. This change in fetal hemoglobin causes it to lose the pocket where adult hemoglobin binds to BPG. Since fetal hemoglobin can't bind BPG, it holds onto oxygen more strongly than adult hemoglobin and can thus take oxygen away from the mother's hemoglobin.
2. Sickle cell anemia is a genetic disease affecting hemoglobin in which blood cells carrying the defect assume a sickle shape under conditions of low oxygen. The disease is treated by attempting to induce adults with the disease to make fetal hemoglobin.
3. The mutated gene in sickle cell anemia acts recessively, meaning that it takes two copies to show the disease. People who are heterozygous (one copy of the gene and one normal copy) appear to have a better survival rate against malaria.
4.. X-ray crystallography is a technique for determining the 3D structure of a protein. It involves 1) formation of purified crystals of a protein out of a solution; 2) shooting of x-rays through the crystal; 3) observation of the diffraction patten by which the x-rays exit the instrument; and 4) determination of the structure of protein required to generate the pattern observed.
5. Nuclear magnetic resonance is another technique for determining protein structure. It has the advantage of studying proteins in their natural environment - water. It involves the use of high strength magnetic fields.
Protein Structure & Purification
1. To study a protein, one must purify it away from all the other proteins in a cell. Steps in the purification typically include 1) busting cells open; 2) centrifuging cellular components apart from the cytoplasm; and 3) using techniques that separate molecules by several different processes.
2. Most proteins require more than one method to be purified.
3. Techniques for protein purification often rely on the structural components of proteins. Isolation of proteins from cells requires breaking open the cells, centrifugation to remove insoluble debris, and the application of protein isolation techniques to purify desired proteins from the soluble fraction of the cells.
4. Gel exclusion chromatography is a technique for isolating proteins on the basis of their different sizes. The method uses 'beads' with uniform holes in them. The holes are openings to tunnels through the bead. Small molecules that fit into the holes travel throught the tunnels and take longer to pass through the column than large molecules that do not fit into the holes.
5. Ion exchange chromatography uses beads that don't have holes, but instead have charged molecules linked to them. Anion exchange chromatography has positive ions linked to the beads and a chloride counterion. When a solution of charged molecules pass through the column, the negative chloride ions are replaced by the negatively charged molecules, which 'stick' to the positive ions linked to the column. Cation chromatography uses negative ions linked to the beads with sodium or potassium counterions.
6. Gel electrophoresis involves gelatinous support materials (agarose - for DNA or polyacrylamide - usually for proteins) and an electric current that drags molecules through the gel. Electrodes are arranged such that the "top" or beginning of the gel is where the negative electrode is placed and the positive electrode is placed at the bottom or end of the gel. DNA is negatively charged, so it is repelled away from the top and towards the bottom of the gel. Separation is on the basis of size. Large molecules travel slowest in the gel, whereas the small molecules travel fastest. DNA fragments appear as bands on a gel and bands can be excised separately from the other bands for further manipulation.