the in situ iodination reaction described in the following classic paper by
the late Paul Sigler works quite well.
Iodination of a single tyrosine in crystals of alpha-chymotrypsin.
Biochemistry. 1970 Sep 1;9(18):3609-17.
The primary purpose of my experiment (which took place 11 years ago
according to my notebook) was indeed to iodinate tyrosines, but difference
fourier analysis using calculated phases from the final refined MIR
structure to reveal the complete iodination model (out of curiosity), showed
that in addition to iodination of two tyrosines, two histidines had also
been iodinated! In retrospect, I had actually run across those peaks in my
cross-difference fourier maps but thought that they were too 'secondary' to
be included in the heavy atom model.
L-ProBE, Unit for Structural Biology
K.L. Ledeganckstraat 35
9000 Ghent, BELGIUM
office: +32-(0)9-264.51.24 ; mobile: +32-(0)472-92.85.19
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From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of
Sent: Tuesday, March 31, 2009 9:11 PM
To: [log in to unmask]
Subject: Re: [ccp4bb] Halide soaking
it worked very nice for me in 1 out of 1 case where I tried it :-).
Very well diffracting crystals (1.8 Ang), rather small protein 20
kDa, 50 %solvent content, 1 mol/ASU. 20-30 s soak in 0.5 M NaBr
resulted in 6 nice ordered sites.
It was crucial for us to collect a 3 wavelength MAD data set. A SAD
data set (using just the peak, even if with high redundancy ) was not
enough to obtain traceable electron density map, even-though
one could distinguish clearly protein boundaries and solvent channels.
On 31 Mar 2009, at 18:19, tat cheung cheng wrote:
> Hi all
> I am now trying to do bromide soaking, but i am not really sure does
> the bromide atom enter my crystal. So is there any signs that
> indicate the entry of bromide atom? e.g. does the space group, cell
> dimension change? or just nothing change, and the bromide atom just
> get in?
> Thanks very much.
> T.C. Cheng
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