Proteomics

Proteomics research defines the dynamic nature of gene expression and regulation with detailed protein profiling, protein-protein interactions, and structural biology studies. Sigma's innovative technologies and products provide an integrated approach for proteomic analysis of both native and recombinant fusion proteins

Epigenetics

Epigenetics is the study of heritable changes in gene expression without a change in DNA sequence. The best understood Epigenetic mechanism, DNA methylation, refers to the addition of a methyl group by the enzyme DNA Methyltransferase to the 5-carbon of cytosine in a CpG dinucleotide. Methylation in regulatory regions adjacent to genes generally acts to suppress gene expression and/or regulation potentially having an impact on cellular function. Once a cell has an established DNA Methylation pattern, methlyated sites are inherited by daughter cells which have important implications in cellular function. Epigenetic research has demonstrated that aberrant DNA methylation is present in several disease states including cancer, in addition to other genetic diseases. Carcinogenesis can occur when DNA methylation acts to silence tumor suppressor genes, leading to heritable alterations of these genes.

DNA Replication

DNA replication is the process of copying a double-stranded DNA molecule to form two double-stranded molecules.The process of DNA replication is a fundamental process used by all living organisms as it is the basis for biological inheritance. As each DNA strand holds the same genetic information, both strands can serve as templates for the reproduction of the opposite strand. The template strand is preserved in its entirety and the new strand is assembled from nucleotides. This process is called "semiconservative replication". The resulting double-stranded DNA molecules are identical; proofreading and error-checking mechanisms exist to ensure near perfect fidelity.
In a cell, DNA replication must happen before cell division can occur. DNA synthesis begins at specific locations in the genome, called "origins", where the two strands of DNA are separated..RNA primers attach to single stranded DNA and the enzyme DNA polymerase extends the primers to form new strands of DNA, adding nucleotides matched to the template strand. The unwinding of DNA and synthesis of new strands forms a replication fork. In addition to DNA polymerase, a number of other proteins are associated with the fork and assist in the initiation and continuation of DNA synthesis.
DNA replication can also be performed artificially, using the same enzymes used within the cell. DNA polymerases and artificial DNA primers are used to initiate DNA synthesis at known sequences in a template molecule. The polymerase chain reaction (PCR), a common laboratory technique, employs artificial synthesis in a cyclic manner to rapidly and specifically amplify a target DNA fragment from a pool of DNA.

Cloning

A major problem in biochemical research is obtaining sufficient quantities of the substance of interest. These difficulties have been largely eliminated in recent years through the development of molecular cloning techniques. The clone is a collection of identical organisms that are all replicas of a single ancestor. Methods of creating clones of desired properties, usually called genetic engineering and recombinant DNA technology, deserve much of the credit for the dramatic rise of biotechnology since the mid-70'. The main idea of molecular cloning is to insert a DNA segment of interest into an autonomously replicating DNA molecule, called acloning vector, so that the DNA segment is replicated with the vector. Such vectors could be, for instance, plasmids (circular DNAs occuring in some bacteria). Reproduction of DNA segments in appropriate hosts, results in the production of large amount of the inserted DNA segment. A DNA to be cloned is usually a fragment of a genome of interest, obtained by application of restriction enzymes. Most restriction enzymes cleave duplex DNA at specific palindromic sites, generally two fragments that have single strand ends that are complimentary with each other (known as 'sticky ends'). Therefore, a restriction fragment can be inserted into a cut made in a cloning vector by the same restriction enzyme, because the segment ends stick (chemically bond) to the loose ends of the vector. Such a recombinant DNA molecule is inserted into a fast reproducing host cell, and is duplicated in the process of the host's reproduction. The cells containing the recombinant DNA are then isolated from non-infected cells using an antibiotic substance which the original vector is resistant to .