Editing Synthesis of LLO-s-s PEI

1. Dissolve 10 mg&nbsp; PEI1.8&nbsp; in 0.5 ml of methylene chloride.<br> 

2. Add&nbsp; 0.5 ml (N-Succinimidyl 3-(2-pyridyldithio)-propionate) (SPDP) in methylene chloride dropwise to the PEI solution.<br> 

3. React at room temperature for 6 h. <br> 

4. Remove methylene chloride under vacuum at room temperature. <br> 

5. Extract dried mixtures with 1 mL of phosphate buffer.<br> 

6. Filter through a 0.45 ÎŒm syringe filter.<br> 

7. Purify PEI pyridyldithiopropionate (PEI1.8-PDP)&nbsp; by size exclusion chromatography (Sephadex G10, 1Ã35 cm) with deionized water. <br> 

8. Determine PEI content using Cu2+ against PEI1.8 standard at 630 nm. <br> 

9. Determine the number of PDP groups per average chain of PEI.<br> 

9.1. Treatment of PEI1.8-PDP at 50 mM DTT<br> 

9.2. Purify thiolated PEI using Sephadex G10. 

9.3. Determine&nbsp; pyridine-2-thione at 343 nm (molar absorptivity=8080 cmâ1 Mâ1)<br> 

[[Category:Transfection]] [[Category:paul]]