Lysozyme surrogates protein extraction

Figure 14.4 Gel image of proteins extracted from a mixed carbonic anhydrase lysozyme tissue surrogate. Lane M, molecular weight marker lane 1, a 1 2 mol ratio mixture of native, non-formalin-treated carbonic anhydrase and lysozyme lane 2, mixed surrogate with 1 2 mol ratio carbonic anhydrase lysozyme, solubilized and retrieved in 20mM Tris-HCl, pH 4.0, with 2% SDS lane 3, mixed surrogate with 1 2 mol ratio carbonic anhydrase lysozyme, solubilized and retrieved in 20mM Tris-HCl, pH 6.0, with 2% SDS. Protein bands corresponding to lysozyme monomer (a), carbonic anhydrase monomer (b), and the putative lysozyme-carbonic anhydrase heterodimer (c) are indicated. For more detail, see Reference 25.

The tissue surrogates described here clearly represent a simplification of real FFPE tissues. However, they represent a useful and efficient construct for the evaluation and optimization of tissue extraction conditions for proteomic studies. More informative studies will likely be realized by using more complex tissue surrogates, which can be created by incorporating additional proteins into lysozyme solutions. Tissue surrogates comprised of up to five proteins have been successfully analyzed by MS (Fowler, unpublished data). Additionally, RNA, DNA, lipids, or carbohydrates can be added at nanomolar to millimolar concentrations to increase the complexity of the model system to better mimic whole tissue. The use of these more complex tissue surrogates should facilitate the development of protein recovery protocols optimal for proteomic investigation. 

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