Product Availability Update

Promega Manufacturing and Delivery Systems continue to be fully operational during the COVID-19 outbreak. Our teams are in regular contact with suppliers and distributors worldwide and are taking all steps necessary to address both demands for diagnostic tools and reliable delivery of all products as quickly as possible. Learn more

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How do I determine the apparent molecular weight of a protein?

Some proteins migrate anomalously on SDS gels; therefore the molecular weight estimate obtained is referred to as the apparent molecular weight. When determining the apparent molecular weight of a protein, do not compare your protein of interest to prestained protein molecular weight markers. Prestained molecular weight markers will run differently than unstained proteins; use unstained protein molecular weight markers and stain the gel after electrophoresis.

LabFact #35

When expressing your protein in a cell-free system, make sure the combination of promoter and DNA conformation is appropriate. For example, the T7 RNA polymerase promoter may express better in a linearized template while the SP6 promoter transcribes better in a circular DNA.

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