The Use of Laser Capture Microscopy in Proteomics Research – A Review

Abstract

The sequencing of the human genome began with much fanfare in 1990 with the start of the Human Genome Project. Major portions of that program have been completed since the interim draft of the human sequence was published in 2001 [1]. Scientists now turn their attention to an even more complex and arduous task, characterizing the human ‘proteome’. The term proteome was coined to describe all the proteins present in a cell, tissue, or an organism [2]. The human genome consists of roughly three billion base pairs of deoxyribonucleic acid, encoding about 30,000 genes. By means of alternative splicing of messenger RNA, these genes are thought to encode over 100,000 proteins. Yet this number only hints at the complexity of the human proteome, for each protein is modified posttranslationally, is expressed in differing amounts in different tissues under different conditions, and interacts in broad networks with other proteins to regulate the physiology of the cell and the organism overall. Thus, characterizing all these proteins and deducing their role, which is the goal of the science of ‘proteomics’, will require a number of new and innovative tools [3]. The study of proteins is not new. In fact, the field of biochemistry was built on the study of proteins functioning as enzymes. Tools from that era are constantly being adapted to further our understanding of proteins during the ‘proteomic’ era. The tools can be used alone or in combination with one another to separate, purify, and ultimately identify proteins. For instance, twodimensional gel electrophoresis (2DE) can separate a complex mixture of proteins into its constituent proteins based on their size and charge. From 3000 to 10,000 proteins can be separated into spots on a gel depending on the sensitivity of the spot detection method that is used [4]. Mass spectrometry can be used to further characterize the separated proteins, even identify specific proteins sequences based on the mass spectrum produced. Newer techniques such as surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI TOF MS) are building on older technologies to create high-throughput methods to characterize proteins in serum or in a cell [5]. A new technology that is increasingly being employed in proteomics research is laser capture microscopy.