There are many examples where "cross-seeding" with homologous proteins has worked, both in classical and recent work.  You should add seed-stocks from any crystals with significant homology to your routine screening experiments in the first place.

The important thing is to use random screens at first.  This has the effect of giving you new leads and also optimizing the ones that you have (plus you can control the number of crystals per drop).

See http://hamptonresearch.com/documents/ramc/RAMC2011_T11_Obmolova.pdf  (Omolova and colleagues have examples where complexes were seeded with crystals of one of the components and vice versa.)

The excellent review by Stura and co covers most of the theoretical points.  (1999). Epitaxial jumps. J. crystal growth, 196(2), 250-260.

For practical details see the original paper by D'Arcy (Acta Cryst D: 63.4 (2007): 550-554) and also our paper "Random microseeding: a theoretical and practical exploration .... " Crystal Growth & Design 11.8 (2011): 3432-3441.

also http://www.douglas.co.uk/MMS_proc.htm

Acoot, this is also the approach to use with your "cubic" crystals.  Don't think about it too much, just try it!

The only thing that I can't explain is why this random seeding method, including cross-seeding, is not more well-known.

Hope it works

Patrick



On 27 December 2013 21:03, Mark van Raaij <[log in to unmask]> wrote:
the differences are likely to be on the protein surface, and these would make the crystal contacts, i.e. it would be unlikely the protein could crystallise in the same crystal habit.
Never say never in crystallisation (i.e. try anything), but I would go for other things first like additives, different crystallisation techniques, temperatures, concentrations etc.

On 27 Dec 2013, at 20:29, Mahesh Lingaraju wrote:

> Dear all,
>
> I was wondering if it sounds logical to use the crystals from a possible structural homolog as seeds to induce nucleation ? (in terms of overall sequence, the proteins are considerably different but based on sequence alignment and structures from other related proteins, it is highly likely the protein would have the same structure.)
>
> Please comment if any of you had experience with this.
>
> Thank you
>
> Happy holidays :)
>
> Mahesh



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