Oxalate. Sometimes forms when PEGs get old and begin to oxidize. That's some of the stuff that is responsible for PEG's becoming progressively more acidic as they age.
No idea if you have PEG in solution or not. Alternative - CH3-C(=O)-COOH Disordered dimethyl formamide Dimethyl acetamide (CH3)2-N-C(=O)-CH3 And so forth. Artem -----Original Message----- From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On Behalf Of Wu, Mousheng Sent: Thursday, July 26, 2007 6:35 PM To: [email protected] Subject: Re: [ccp4bb] unknown density in structure There are four molecules in the asymmetric unit. And this density is present in every molecules. -----Original Message----- From: ANA MARIA MISIC [mailto:[EMAIL PROTECTED] Sent: Thursday, July 26, 2007 5:24 PM To: Wu, Mousheng Subject: Re: [ccp4bb] unknown density in structure Hi Mousheng - Did you check to see if that falls on a special position? That can lead to a buildup of electron density, and the symmetrical shape is suspect. good luck Ana M. Misic Research Assistant Department of Biomolecular Chemistry Department of Bacteriology University of Wisconsin - Madison 420 Henry Mall, Rm 230 Madison, WI 53706 Lab Phone: (608)265-9282 Fax: (608)262-9865 ----- Original Message ----- From: "Wu, Mousheng" <[EMAIL PROTECTED]> Date: Thursday, July 26, 2007 4:21 pm Subject: [ccp4bb] unknown density in structure To: [email protected] > Hi, everyone, > > > > I am recently solving a structure at 1.8A. After I fitted all residues > into the model, I found that there was an extra density in a pocket > consisted of E, N, R and other hydrophobic residues. The density is > strong and connected like a butterfly. I checked the crystallization > condition. I can not figure out what it is. It seems that it is not from > the crystallization components. > > > > Does anyone know how to figure out what the density is? Is there any > program or database I can use to predict the potential ligand? > > Thanks. > > > > Mousheng >
