Hi Seema, Small addition to the already abundant suggestions, if you have high solvent content or significant portion of non-observable density, you normally get higher R-free. Clement #################################################### Clement Angkawidjaja, PhD. G30 Assistant Professor ------------------------------------------------------------------------------------------- Chemistry-Biology Combined Major Program International College, Osaka University 1-30 Machikaneyama-cho Toyonaka, Osaka 560-0043, Japan http://cmp.sci.osaka-u.ac.jp/CMP/ Tel. +81-6-6850-5952 Fax +81-6-6850-5961 ------------------------------------------------------------------------------------------- Laboratory of Molecular Biotechnology Graduate School of Engineering Osaka University 2-1 Yamadaoka U1E-804 Suita, Osaka 565-0871, japan http://www.mls.eng.osaka-u.ac.jp/~bio_ext/mlsbe123/clement.html Tel/Fax +81-6-6879-4157 ####################################################