Nanoparticles – Workhorses That Bring Tremendous Benefit

Tiny particles found in clothing, cosmetics, food, electronics or furniture enter our bodies and behave in unexpected (sometimes unwanted) ways. However, in the realm of medicine another type of particle called the nanoparticle can bring untold potential. We can load them with drugs, for example, and deliver them precisely to a diseased organ or cell. Mark Davis from the California Institute of Technology has created nanoparticles that deliver siRNA specifically into melanomas. Davis and his colleagues have not shied away from making bold claims about the therapeutic potential of their work.  They write:

“When taken together, the data presented here provide the first, to our knowledge, mechanistic evidence of RNAi in a human from an administered siRNA. Moreover, these data demonstrate the first example of dose-dependent accumulation of targeted nanoparticles in human tumours. ….These data demonstrate that RNAi can occur in a human from a systemically delivered siRNA, and that siRNA can be used as a gene-specific therapeutic.” Davis et al. 2010. Continue reading “Nanoparticles – Workhorses That Bring Tremendous Benefit”

Screening for Protein Activity Using Cell-Free Expression

The analysis of functional protein typically requires lengthy laborious cell based protein expression that can be complicated by the lack of stability or solubility of the purified protein. Cell free protein expression eliminates the requirement for cell culture thus providing quick access to the protein of interest (1).

The HaloTag® Technology provides efficient, covalent and oriented protein immobilization of the fusion protein to solid surfaces (2).

A recent publication demonstrated the feasibility of using cell free expression and the HaloTag technology to express and capture a fusion protein for the rapid screening of protein kinase activity (3). The catalytic subunit of human cAMP dependent protein kinase was expressed in a variety of cell free expression formats as a HaloTag fusion protein. The immobilized cPKA fusion protein was assayed directly on magnetic beads in the active form and was shown to be inhibited by known PKA inhibitory compounds.

Therefore this unique combination of protein expression and capture technologies can greatly facilitate the process of activity screening and characterization of potential inhibitors


  1. Zhao, K.Q. et al. (2007) Functional protein expression from a DNA based wheat germ cell-free system. J. Struc. Funct. Genomics. 8, 199-208.
  2. Los, G.V. and Wood, K. (2007) The HaloTag: A novel technology for cell imaging and protein analysis. Meth. Mol. Biol. 356, 195-208
  3. Leippe DM, Zhao KQ, Hsiao K, & Slater MR (2010). Cell-free expression of protein kinase a for rapid activity assays. Analytical chemistry insights, 5, 25-36 PMID: 20520741

How to Use the Flexi® Vectors (Part 2 of 2)

pFN24K HaloTag® CMVd3 Flexi® VectorIn previous entries, I discussed the naming convention for the many Flexi® Vectors available from Promega before addressing how to choose which vector is appropriate for your use. However, I did not cover all the Flexi® Vectors available. In fact, I saved the HaloTag® Flexi® Vectors for this final installment. Continue reading “How to Use the Flexi® Vectors (Part 2 of 2)”

Create Custom Microarrays for Your Research Needs

In the post-genome sequencing era, researchers are increasingly turning their attention to the proteins encoded within the genome. How are their synthesis, degradation and conformation regulated? Do they interact with other proteins or nucleic acids or lipids? Can these interactions be perturbed? How do changes in the coding sequence of the gene affect the proteins and their function? Like DNA microarrays, protein arrays fulfill a need for miniaturization and throughput, but immobilizing proteins in a way that preserves function and conformation is not a simple problem to solve. Continue reading “Create Custom Microarrays for Your Research Needs”