AMBER Archive (2008)

Subject: Re: AMBER: drawing repeated units

From: Taufik Al-Sarraj (
Date: Fri May 09 2008 - 13:10:56 CDT

thank you Ross,
I will try this, and i have no problem starting with a straight
oligomer, it would be nice to see how they fold in solution during the MD.


Ross Walker wrote:
> Hi Taufik,
>> i was wondering if there is an automatic or an easy way to draw a
>> oligomer in AMBER9. i have a an easy CH2-C(CH)(COC2OH5) unit. I would
>> like to draw an oligomer that consist of 50, 100, 150 of these units. Is
>> this possible?
> Probably the easiest way to do this is to build a single unit in leap. Call
> it residue foo or whatever and assign it head and tail atoms (equivalent to
> the C and N in amino acids). Then you can assign it atoms type and charges (
> you may have to build termini versions as well to deal with the capping -
> i.e. protonated end points. You could call these Nfoo and CFoo.
> Then once you have your units built you can have leap string them together
> for you.
> E.g. mymol = sequence { Nfoo foo foo foo Cfoo } etc.
> To build very long ones you could write a shell script that creates a simple
> leaprc script for you that you can then read back into xleap or tleap.
> Of course this will give you straight chains which you may not want so if
> you want to build some kind of bundle this may be harder and you'll probably
> need some kind of input coordinates. Or build a more complex foo unit that
> contains several units including the turns so that when leap applies the
> z-matrix for each block you end up with a bundled structure.
> Good luck,
> Ross
> /\
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> |\oss Walker
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