Re: [ccp4bb] Determining concentration of membrane protein

2014-02-16 Thread Raji Edayathumangalam
Hi Everyone, Thank you so much for your additional tips about various kits. My protein is tagged and when I cleave off the tag (a step that needs reducing agent), I will unfortunately have both detergent and reducing agent in my protein buffer. Nicolas, thanks for your word of caution. I can't

Re: [ccp4bb] Determining concentration of membrane protein

2014-02-14 Thread FOOS Nicolas
De : CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] de la part de Ho Leung Ng [h...@hawaii.edu] Envoyé : vendredi 14 février 2014 01:58 À : CCP4BB@JISCMAIL.AC.UK Objet : Re: [ccp4bb] Determining concentration of membrane protein Hi Raji, There are also some

Re: [ccp4bb] Determining concentration of membrane protein

2014-02-14 Thread FOOS Nicolas
] de la part de Niks [nik...@gmail.com] Envoyé : vendredi 14 février 2014 07:45 À : CCP4BB@JISCMAIL.AC.UK Objet : Re: [ccp4bb] Determining concentration of membrane protein Dear All, May be a stupid question. But if we take buffer with detergent as control (Blank), would not the difference in ODs

Re: [ccp4bb] Determining concentration of membrane protein

2014-02-14 Thread Patrick Loll
No, because Bradford is based on the increase in absorbance when the dye moves from a hydrophilic environment to a hydrophobic one (like the protein interior, or like the interior of a micelle). When detergents are present in excess of their CMC, the change in absorbance from partitioning into

[ccp4bb] Determining concentration of membrane protein

2014-02-13 Thread Raji Edayathumangalam
Dear CC4BBers, I am trying to figure out what is the best way to determine the protein concentration of my membrane protein. My purified membrane protein is in 20mM Tris pH 7, 150mM NaCl and 0.02% DDM (CMC of DDM=0.0076%). After reading the friendly manuals and searching online, I've learned

Re: [ccp4bb] Determining concentration of membrane protein

2014-02-13 Thread R. M. Garavito
Roger, While I agree with your list, the BCA assay does not use molybdate (as we make it from scratch with bicinchoninic acid, sodium carbonate, sodium bicarbonate, sodium tartrate, and cupric sulfate pentahydrate). For membrane proteins, I prefer the BCA assay until the protein is pure

Re: [ccp4bb] Determining concentration of membrane protein

2014-02-13 Thread Raji Edayathumangalam
Hi Everyone, Thanks very much for your helpful responses and suggestions. I will use the BCA assay. Cheers, Raji On Thu, Feb 13, 2014 at 11:27 AM, R. M. Garavito rmgarav...@gmail.comwrote: Roger, While I agree with your list, the BCA assay does not use molybdate (as we make it from

Re: [ccp4bb] Determining concentration of membrane protein

2014-02-13 Thread Ho Leung Ng
Hi Raji, There are also some proprietary stains such as the 660 nm (can't they think of a better product name?) stain from Pierce that are detergent compatible. I used this briefly with success when comparing against Abs 280 nm. Ho Ho Leung Ng University of Hawaii at Manoa Assistant

Re: [ccp4bb] Determining concentration of membrane protein

2014-02-13 Thread Niks
Dear All, May be a stupid question. But if we take buffer with detergent as control (Blank), would not the difference in ODs using any of the methods used e.g. Bradford assay, gives protein concentration? Regards Nishant On Thu, Feb 13, 2014 at 9:09 PM, Roger Rowlett rrowl...@colgate.edu wrote: