Even today, we still try to soak existing native protein crystals with heavy atoms at the same time while SeMet substituted protein is prepared.
Nearly half of the times, we are able to solve the structure with HA (always SIRAS) before we have the SeMet protein. A recent example: Structure. 2009 Jul 15;17(7):939-51. Structure and function of an ADP-ribose-dependent transcriptional regulator of NAD metabolism. Huang N, De Ingeniis J, Galeazzi L, Mancini C, Korostelev YD, Rakhmaninova AB, Gelfand MS, Rodionov DA, Raffaelli N, Zhang H. Hong -----Original Message----- From: CCP4 bulletin board [mailto:[email protected]] On Behalf Of Ronald E Stenkamp Sent: Wednesday, June 06, 2012 10:23 AM To: [email protected] Subject: Re: [ccp4bb] Fun Question - Is multiple isomorphous replacement an obsolete technique? There were a number of labs using anomalous dispersion for phasing 40 years ago. The theory for using it dates from the 60s. And careful experimental technique allowed the structure solution of several proteins before 1980 using what would be labeled now as SIRAS. Ron On Wed, 6 Jun 2012, Dyda wrote: >> I suspect that pure MIR (without anomalous) was always a fiction. I doubt that anyone has ever used it. Heavy atoms always give >> an anomalous signal > >> Phil > > I suspect that there was a time when the anomalous signal in data sets was fictional. > Before the invent of flash freezing, systematic errors due to decay and the need > of scaling together many derivative data sets collected on multiple crystals could render > weak anomalous signal useless. Therefore MIR was needed. Also, current hardware/software > produces much better reduced data, so weak signals can become useful. > > Fred > > [32m*********************************************************************** ******** > Fred Dyda, Ph.D. Phone:301-402-4496 > Laboratory of Molecular Biology Fax: 301-496-0201 > DHHS/NIH/NIDDK e-mail:[email protected] > Bldg. 5. Room 303 > Bethesda, MD 20892-0560 URGENT message e-mail: [email protected] > Google maps coords: 39.000597, -77.102102 > http://www2.niddk.nih.gov/NIDDKLabs/IntramuralFaculty/DydaFred > **************************************************************************** ***[m >
