 The total complement of proteins present at a time in a cell or cell type is known as its <unk> , and the study of such large @-@ scale data sets defines the field of proteomics , named by analogy to the related field of genomics . Key experimental techniques in proteomics include 2D electrophoresis , which allows the separation of a large number of proteins , mass spectrometry , which allows rapid high @-@ <unk> identification of proteins and sequencing of peptides ( most often after in @-@ gel <unk> ) , protein <unk> , which allow the detection of the relative levels of a large number of proteins present in a cell , and two @-@ hybrid screening , which allows the systematic exploration of protein – protein interactions . The total complement of biologically possible such interactions is known as the <unk> . A systematic attempt to determine the structures of proteins representing every possible fold is known as structural genomics . 
