Date: Tue, 19 Feb 2019 23:05:18 +0000
Dear colleagues,
Typically, the NOESY cross peaks from small molecule (less than 1000 Da) have opposite sign relative to diagonal peaks, so called positive cross peaks. But I observed negative cross peaks from a molecule about 650 Da (see the attached spectrum). It cannot be due to exchange since these protons are not exchangeable. Does anyone have explanation for this observation. The NOESY mixing time was set to 1 sec and temperature is 40C.
Thanks in advance.
Weidong
Dr. Weidong Hu
NMR Facility Manager
Department of Molecular Imaging and Therapy
Beckman Research Institute
1450 E. Duarte Rd., Duarte, CA 91010
Tel: 626 256 4673, Ext: 63416
Fax: 626 301 8186
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(image/jpeg attachment: negativeNOE_smallMolecule.JPG)