Hi, I've had a couple of successful cases: 1) Uranyl acetate soak to get starting phases at 6.0A combined with a gold derivative at 3.8A. Both quick soaks of about 10-20 mins in 5-10 mM on crystals less than 100 microns. 2) Mercuric chloride soak of 10 mM for 10 mins to get starting phases at 2.8A. This was sucessful after 9 attempts with different compounds (some are just different conc. of same compound), mostly in 0.5-10 mM range for 5-20 mins and a couple of Sm, Gd and Eu compounds at ~50-100 mM. Have always found Greg Petsko's original article on heavy atom derivations in methods in enzym. to be a good guiding factor to decide on what compounds to try based on amino acid info and crystallization conditions (since the pH affects binding of some compounds). Hampton's heavy atom screening kit also provides this information now. More recently, have also looked at the info. contained in (Acta Crystallogr D Biol Crystallogr. <javascript:AL_get(this, 'jour', 'Acta Crystallogr D Biol Crystallogr.');> 2005 Sep;61(Pt 9):1302-5. Epub 2005 Aug 16), heavy atom database. The most intriguing case of heavy atom derivatization that I've heard of is from one of my former colleagues who just sprinked some crystals (without any measurement) of a heavy atom compound into the drop with crystals, let is soak for a bit and collected a successful MAD data set on it.
Regards, Debanu. ________________________________ From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On Behalf Of Derek Logan Sent: Tuesday, September 25, 2007 12:13 AM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] "Quick soak" method Hi, I'd like to find out how successful the "quick soak" method for heavy atom derivatisation proposed by Radaev and Sun: Sun PD, Radaev S, Kattah M. Generating isomorphous heavy-atom derivatives by a quick-soak method. Part I: test cases. Acta Cryst. 2002. D58:1092-1098. has been in comparison to the "classical" method of longer soaks at low concentrations of heavy atom compound. The method was quite successful in our hands a few years ago but (fortunately?) it's becoming increasingly rare that we use heavy atoms. I understand that evidence will necessarily be anecdotal, but let's not let that stop us. Derek -- Derek Logan tel: +46 46 222 1443 Associate professor fax: +46 46 222 4692 Molecular Biophysics mob: +46 76 8585 707 Lund University Box 124, Lund, Sweden
