Sigma-Aldrich Introduces New Vectors to Increase the Flexibility of the TargeTron Gene Knockout System

ST. LOUIS, MO, and Taufkirchen, Germany, 18th October 2005 - Sigma-Aldrich (Nasdaq: SIAL), a $1.4 billion Life Science and High Technology Company, announces the introduction of new TargeTron Vectors designed for use with the TargeTron Gene Knockout System. The new vectors enhance the capabilities and increase the flexibility of the TargeTron Gene Knockout System providing researchers with an efficient, targeted method to knock out multiple genes in prokaryotic organisms, to generate knockouts without using selection or by using removable selection, and to use the TargeTron Gene Knockout System to produce knockouts in organisms lacking a source of T7 RNA polymerase.

The TargeTron Vector pACD4K-C-loxP is a linerized E. coli expression vector containing loxP sites to facilitate the removal of the kanamycin marker. This enables the generation of multiple, site-specific knockouts in the same bacterial chromosome.

The pACD4 TargeTron Vector Set (no selectable marker) contains four linerized vectors lacking the kanamycin RAM marker. Additionally, each vector has an A, C, G, or T in the delta + 1 position. This facilitates proper base pairing of the group II intron RNA for different target site designs resulting in more efficient precursor RNA splicing to form active TargeTron RNP's. The pACD4 TargeTron Vector Set allows researchers to generate prokaryotic knockouts when selection cannot be used.

The reach of the TargeTron Gene Knockout System has been increased to an even broader range of bacterial hosts with the introduction of the pAR1219 TargeTron Vector. This vector provides a source of T7 RNA polymerase when co-transformed with TargeTron Vector pACD4K-C, included in the TargeTron Gene Knockout System (TA0100). Adding an external source of T7 RNA polymerase allows for the creation of knockouts in organisms such as Salmonella typhimurium and Shigella flexneri as well as in non-DE3 strains of E. coli.

"The launch of these new vectors greatly expands the research applications of the TargeTron system," said Keith Jolliff, Director of Global Marketing for Molecular Biology. "They also exemplify our commitment to customer service. After we launched the TargeTron Gene Knockout kit, we asked customers what they felt was needed to improve the kit and to expand the applications. These vectors are the result of Sigma listening to our customers and addressing their needs."

The TargeTron Gene Knockout System is exclusively licensed from Ingex, LLC and is expected to revolutionize functional genomics and systems biology. Used in conjunction with the three new TargeTron vectors, the TargeTron Gene Knockout System provides researchers with a more flexible tool for generating prokaryotic knockouts.

For more information on the TargeTron vectors and the TargeTron Gene Knockout System from Sigma-Aldrich, please visit us online at http://sigma-aldrich.com/targetron.

About Sigma-Aldrich:
Sigma-Aldrich (Nasdaq: SIAL) is a leading Life Science and High Technology company. The Company's biochemical and organic chemical products and kits are used in scientific and genomic research, biotechnology, pharmaceutical development, the diagnosis of disease and as key components in pharmaceutical and other high technology manufacturing. It has customers in life science companies, university and government institutions, hospitals, and in industry. Over one million scientists and technologists use its products. Sigma-Aldrich operates in 35 countries and has over 6,800 employees providing excellent service worldwide. The Company is committed to Accelerating Customers' success through leadership in Life Science, High Technology and Service. For more information, visit:
www.sigma-aldrich.com .

This release contains forward-looking statements relating to future performance, goals, strategic actions and initiatives, and similar intentions and beliefs and other statements regarding the Company's expectations, goals, beliefs, intentions and the like, which involve assumptions regarding Company operations and conditions in the markets the Company serves. The Company does not undertake any obligation to update these forward-looking statements.

Media enquiries in Europe to Northbank Communications:
Marc Egelhofer, Tel: +44 (0)1260 296505
m.egelhofer@northbankcommunications.com

At Sigma-Aldrich:
Keith Jolliff, Tel: +1-314-289-8484
Joan Suda, Tel: +1-314-286-7626