Biotin, a 244 Dalton molecule, exhibits an extraordinary binding affinity for avidin and streptavidin (Ka=1015 M-1). This high binding affinity means that proteins, particularly antibodies, are routinely labeled with biotin. The labeled proteins can now be rapidly purified with avidin and streptavidin resins or detected with streptavidin and avidin coupled to enzyme reporters, such as HRP (horseradish peroxidase.
Topics: Protein Labeling
Sputum Liquefaction: from viscous, heterogeneous mucus to equivalent, homogenous samples
Sputum processing has one main purpose; to render the viscous, heterogeneous specimen to a homogenous state (evenly distributed suspension). This homogenous suspension will be dispensed into multiple aliquots for cryopreservation, smear microscopy, gram stain, and culture. Each aliquot should be representative of the original specimen. This can be accomplished through the process of sputum liquefaction.
Topics: Sample Clean Up
Reporter Gene Assays and their applications
Reporter gene assays are paramount for study of regulation of gene expression by gene regulatory elements (cis-acting factors), transcription factors or exogenous regulators (trans-acting factors). In reporter gene assays, the activity of a reporter gene is measured. A reporter gene is joined to a target regulatory DNA sequence in an expression vector, which is then transfected into the cell type of choice. The reporter gene is transcribed and translated in the cells and its activity is measured to access the strength or function of the target regulatory DNA sequence or study effects of transcription factors or potential drugs etc.
Topics: Cytotoxicity Assays