When we were working on PheRS we noticed that our protein preps (and
crystals) had shades of color: sometimes they were pinkish and sometimes
yellowish, or even blueish (and often colorless)!
We solved the structure eventually and found a new metal-binding
microdomain previously not found in these
I agree: light yellow (straw-yellow) proteins often indicate metal-binding -
it's typically iron III. Zn salts tend to be colourless, and the Mn-pink is
too pale to be visible at protein (mM) concentrations. This can be determined
by doing flame-spectroscopy, if you don't mind destroying your
Cobalt leaching of TALON resin perhaps ?
Should be more orange type of color, but it depends on the concentration.
In any event if you shoot those crystals run a scan to find out what metal is
bound and use it for phasing if you have access to a MAD line.
Jürgen
On Nov 6, 2011, at 9:56 AM,
Hi -- has anyone had crystals that are colored in regular
(unpolarized) light? Mine are yellow, and I'm not aware of anything
in the buffer conditions that might cause this. I read online that
glutaraldehyde can turn protein crystals a golden color, but as far as
I know there isn't any
On Sat, Nov 5, 2011 at 3:02 PM, Caitlyn Claire Yeykal
cait...@uchicago.edu wrote:
Hi -- has anyone had crystals that are colored in regular (unpolarized)
light? Mine are yellow, and I'm not aware of anything in the buffer
conditions that might cause this. I read online that glutaraldehyde can
Thanks for all the replies -- there are no suggestions in the
literature or in crystallized or predicted domain structures that this
protein binds a cofactor, and, although I did purify it in insect
cells, PAGE gels and activity assays support the assertion that it's
not ferritin. Nobody
It's also possible that there's oxidation in the buffer causing the yellow
color. I'm not sure how common this is with HEPES. But I see it all the time
with MOPS. Alternatively, does the yellow color bind the column during
purification? If so, then it sounds like a co-purified flavin or
In another thread, you indicated that there were no identifiable cofactor
binding sites in your protein, so we are down to less common situations. Some
proteins are spontaneously decorated with pyridoxal on surface lysine residues.
In some cases, this has absolutely nothing to do with the
