Proteins are biological molecules made up of building blocks called amino acids. Proteins are essential to life, with structural, metabolic, transport, immune, signaling and regulatory functions among many other roles.

Unlike the genome (the complete set of genes within each organism), the composition of the proteome is in a constant state of flux over time and throughout the organism. Therefore, when scientists refer to the proteome, they are also sometimes referring to the proteome at a given point in time (such as the embryo versus the mature organism), or to the proteome of a particular cell type or tissue within the organism.

Proteomics is the study of the proteome—investigating how different proteins interact with each other and the roles they play within the organism.

Proteomics: Techniques

Low-throughput methods:

1. Antibody-based methods:  Techniques such as ELISA (enzyme-linked immunosorbent assay) and western blotting rely on the availability of antibodies targeted toward specific proteins or epitopes to identify proteins and quantify their expression levels.
2. Gel-based methods: Two-dimensional gel electrophoresis (2DE or 2D-PAGE), the first proteomic technique developed, uses an electric current to separate proteins in a gel based on their charge (1st dimension) and mass (2nd dimension). Differential gel electrophoresis (DIGE) is a modified form of 2DE that uses different fluorescent dyes to allow the simultaneous comparison of two to three protein samples on the same gel.
3. Chromatography-based methods: Chromatography-based methods can be used to separate and purify proteins from complex biological mixtures such as cell lysates.

High-throughput methods:

1. Analytical, functional and reverse-phase microarrays: Protein microarrays apply small amounts of sample to a “chip” for analysis (this is sometimes in the form of a glass slide with a chemically modified surface). Specific antibodies can be immobilized to the chip surface and used to capture target proteins in a complex sample.
2. Mass spectrometry-based proteomics: There are several “gel-free” methods for separating proteins, including isotope-coded affinity tag (ICAT), stable isotope labeling with amino acids in cell culture (SILAC) and isobaric tags for relative and absolute quantitation (iTRAQ). These approaches allow for both quantitation and comparative/differential proteomics.

Regards,

Angelina Matthew,

Managing Editor,

Pharmaceutical Analytical Chemistry

Email id: pharmachem@scholarlypub.com