Dear Madhu,

At the resolution that you mention, which is at the edge of the resolution limit for ARCIMBOLDO_LITE, and considering that you have already some information about the possible fold, I would suggest you to use our tool ARCIMBOLDO_SHREDDER, as it will derive fragments starting from your distant homolog template, and refine them against the experimental data, increasing the possibilities of convergence of your MR trial.

The current version of CCP4i1 has already an interface to ARCIMBOLDO_SHREDDER, which will be updated again in the next days, and you can use the spherical mode for your case.

Best wishes,

Claudia Millán

2017-01-02 14:34 GMT+01:00 Madhu Sudhan <[log in to unmask]>:

Dear all,

We are trying to solve a protein structure of 37KDa using molecular replacement method. Protein secondary structure indicates that it has 4-Heat repeat (α-helical hair pin) i.e. 16 α-helices. It has about 40% sequence identity with templates in PDB, using which we tried MR, but we are unable to find a solution using MOLREP, PHASER, BALBES, MRBUMP, MORDA etc.

This protein has two iron molecules also and data were collected at home source using Cu Ka radiation with 1.5418 A wavelength at 2.5 A resolution. Its highest homology PDB template is also having 16 α-helices with horseshoe shaped structure.

We are also trying to use Arcimboldo tool (in the CCP4 7.0) to find the structure solution, but it is taking a long time on our computers (8-core).

So I will be grateful if anyone can provide us suggestions

1. Any program which can provide us good working model having only α-helical content.

2. In case we know our model, how can we optimize Arcimboldo tool with our helical model (we can generate from homologous PDB)

Thanking you in advance,

Madhusudhan