Proteomics is the study of protein structure and function at a large scale. The name is derived from genomics (the study of genomes) Snps differences are extrememly old and can be used to look at migration patterns. mass spectrometry is the main method of study to examine proteins proteome changes between cells and tissues unlike dna so studying it gets even more difficult. Protein called notch , which makes a b-line for nucleus mrna a recent study showed that amount of mrna in a cell does not reflect the amount of protein being made interestingly enough. Post-translational modifications simple phosphorylation: very good way of modifying protein activity. ~2% of our proteome encodes kinases (~500 proteins) serine, threonine and tyrosine are commonly phosphorylated: phosphotyrosine: sh2 domain extremely powerful signal because it calls upon other protein to cause chain reactions. St1571 aka gleevec: drug that"s a hybrid protein.