Hi Neeraj: Terese Bergfors advises several things re PEG: buy gas chromatography quality, don't mix brands/batches, store it in dark, +/- flush with nitrogen, store aliquots at -20 deg C.
Reference: Terese Bergfors (ed), Protein Crystallization: Techniques, Strategies, and Tips. A Laboratory Manual, IUL, pp. 234-5, and references therein, <http://www.iul-press.us/Books/BBT01-Crystallization/crystallization.html>.) (The book, by the way, is out of print. The 2nd edition should be out in the summer.) Sincerely Yours, Navdeep --- Navdeep Sidhu Graduate Student Department of Biochemistry University of Saskatchewan 107 Wiggins Road Saskatoon, SK, S7N5E5 Canada Phone: +1-306-966-4366 Fax: +1-306-966-4390 Email: [EMAIL PROTECTED] --- Quoting Neeraj <[EMAIL PROTECTED]>: > Hi all....i have been trying to crystallize a protein and have had some > hits with conditions having PEG in them (400 and 4000).....but everytime > i have tried to reproduce the conditions there has been a lot of > heterogeneity......and then to look for answers i delved a little deeper > into understading about the ingredients that i have been using and > discovered that PEG might actually be the culprit here.....I am using > PEG 400 and 4000 and since PEGs are inherently unstable and prone to > oxidation in the presence of oxygen by producing increased levels of > aldehydes and peroxides which reduce the pH drasticall, I feel that this > might be whats affecting the reproducibility. I was wondering if anyone > has ever encountered similar scenarios and did anything with regards to > fixing things for PEG. Any help would be greatly appreciated as i am > a little short of ideas since things do work i cant seem to reproduce > them and its very frustrating in a way. > > Thanks and i look forward to some helpful suggestions > Neeraj > > -- > Neeraj Kapoor > TPCB Graduate Fellow > Sakmar Lab/ Molecular Biology & Biochemistry > The Rockefeller University > 1230 York Avenue, RRB 510 > New York, NY 10021 > lab.1.212.327.8284:fax.7904 > mobile: 917.535.2030 > http://www.rockefeller.edu/labheads/sakmar/sakmar-lab.html >
