Messages

1376

General discussions (Q&As) / Re: DNA Triple Helix Generation

« on: October 21, 2011, 07:18:38 am »

Hi Himanshu,

Fig1.png(as attachment) : ... green ribbon shows single strand DNA which is ligand to dock in double stranded DNA. In the green ribbon there is intra-molecular bonding.

Thanks for attaching a PNG image illustrating the unusual "intramolecular bonding(backbone and nitrogen bases)". It is certainly clearer than pure text description. However, it would be even better if you provide the corresponding PDB file so others can easily visualize the problematic structure.

Can we ignore those bonds?

I do not know how you generated the structure, and for what purpose, thus I cannot offer any advice in this regard. The question appears not to be directly 3DNA-related. However, the image does show that the ssDNA is in poor geometry.

Xiang-Jun

1377

General discussions (Q&As) / Re: DNA Triple Helix Generation

« on: October 20, 2011, 07:01:55 am »

Hi Himanshu,

Thanks for posting at the 3DNA forum. Just to be clear, 3DNA does not perform DNA-DNA docking or any energy calculations.

But, the ssDNA show intramolecular bonding(backbone and nitrogen bases) which is un-usual.

Could you elaborate on it? Better with a specific example.

However, 3DNA does provide the following approach for DNA triplex creation which may be useful to your project:

• Build a fiber model (e.g., #31) for Poly (U) : poly (A) : poly(U) (11-fold). Type "[mono:26cqmn7j]fiber -m[/mono:26cqmn7j]" for more info, and search the forum for related posts. Alternatively (or better), pick a related triplex structure from the PDB, or another source.
  
• Perform base mutations (using [mono:26cqmn7j][red:26cqmn7j]mutate_bases[/red:26cqmn7j][/mono:26cqmn7j]) to your specific sequence. See thread "change one base pair in a double-strand DNA structure file".

Please note that the mutated triplexes may have steric clashes (atoms too close) or longer than ideal H-bonding geometry: they are intended as initial structures for refinement using any of the available energy calculation tools.

HTH,

Xiang-Jun

1378

General discussions (Q&As) / Re: 3DNA on 64 bit Linux (Ubuntu)

« on: October 19, 2011, 12:59:01 pm »

I have a problem with running 3DNA on 64 bit Fedora. It says "can't execute the binary file" whenever I try to run any of the programs from 3DNA/bin directory. The PATH and X3DNA environmental variables are set correctly.
Is there a version of 3DNA for 64 bit Linux systems available?

Glad to know the detailed error message. With two cases, now it seems clear that the 32 bit version of 3DNA compiled in Ubuntu does not work in 64 bit machines.

Check email for download info of a 64-bit compiled version of 3DNA and report back if it work on your 64 bit Fedora.

Thanks for using 3DNA and posting in the forum.

Xiang-Jun

1379

MD simulations / Re: H-bonding information in MD analysis output

« on: October 04, 2011, 07:25:42 am »

Hi Andre,

I will try to work with the extract output and organise the data as you suggested. I guess I'm trying to make it easier to see the type of H-bond events that are occuring.

It makes sense. Over the years, 3DNA has been used in ways that are out of my original intention. As a principle, I won't add a 'feature' into 3DNA unless I fully understand it and can back it up when asked. Put another ways, feature-rich is not what 3DNA aims for, but quality is. This is where purpose-specific scripting comes into play, and such a skill is essential for a 'bioinformatican'.

I am not experienced in programing/scripting so it will be an interesting challenge. I'll post the script here if I'm successful as others may have a use for it.

We all learn from practice, and by making mistakes. I am willing to help you in the exercise: just put your script with a reproducible example here, then I (hopefully other viewers of the forum) can make suggestions. With several iterations, the problem will become clearer, and your script may well function for your needs. In retrospect, this is the most effective way to learn things, and I wish to have been guided this way. I aim to turn this forum into a 'educational' resource so that people with similar mind can share and benefit from each other's experience and contributions. I am glad that you are willing to share, which is precisely the incentive that I'd like to help you more.

Have a try, and let's see how it goes.

Xiang-Jun

1380

MD simulations / Re: H-bonding information in MD analysis output

« on: October 03, 2011, 10:19:00 pm »

Hi Andre,

This may be a process that the extract script will have to handle after 'analyze'.

As mentioned previously, I am not convinced to add such a functionality directly in the current two Ruby scripts. If you want to proceed, it is preferable (in my understanding) to start from the extracted [mono:13mhwi7u]<hbond>[/mono:13mhwi7u] parameters. A purpose-specific script is the way to go.

Let's use wastson crick pairing as our conventional H-bond information. For your GC pair example, can we extract and organsie the information so the first column is O2 - N2, second is N3 - N1, and the third is N4 - O6. If there are non-waston crick H-bonds they can be placed in the fourth and subsequent columns.

In addition to G-C pair, you also need to consider C-G pair, which by default swaps the order of atoms in H-bond output.

Do we have to specify all the non-waston crick H-bonds or can the script look for the waston crick H-bonds and place the non-waston crick H-bonds after the standard waston crick information?

It is entirely up to you, with a purpose-specific script.

HTH,

Xiang-Jun

1381

MD simulations / Re: H-bonding information in MD analysis output

« on: October 02, 2011, 09:40:40 am »

Since the H-bond information for each base pair is arranged in columns, is there a way for the script to define each column for a specific H-bond and if the bond does not exist then it will leave it blank?

The parsing script has no knowledge of any 'specific H-bond': it just takes H-bonds for each base-pair as a single unit of text string. The H-bond info is calculated with 'analyze', based on purely geometric criteria. Thus for example there can be different A-T pairs: e.g., Watson-Crick pair and Hoogsteen pair, and many other possibilities.

In the example shown in my first reply, note the first two C-G pairs:

1 C-----G  [2]  O2 - N1  2.99  N4 - O6  2.98
2 C-----G  [3]  O2 - N2  2.74  N3 - N1  2.84  N4 - O6  3.17

They are based on model #20 of the distributed PDB ensemble 'sample_md0.pdb'. Note specifically, while the 2nd C-G pair is normal with 3 H-bonds, the first C-G pair has 2 H-bonds including the unconventional 'O2 - N1  2.99'.

Overall, I cannot see a sensible, generally applicable way to "define each column for a specific H-bond".

Here is a file to show you what I mean

I realise this is just formatting however it will make life easier to have the script format the output rather than do it manually.

See above. For your example, the first column does not align. Think about all the possible base sequence and pairing patterns, what you are asking for is certainly not just a formatting matter.

0   [3]   O2 - N2   2.96   N3 - N1   3.03   N4 - O6   3.49
1   [3]   O2 - N2   3.53   N3 - N1   2.97   N4 - O6   2.75
2   [3]   O2 - N2   3.01   N3 - N1   2.78   N4 - O6   3.19
3   [3]   O2 - N2   3.17   N3 - N1   3.25   N4 - O6   3.53
4   [3]   O2 - N2   2.81   N3 - N1   2.97   N4 - O6   3.22
5   [3]   O2 - N2   2.86   N3 - N1   2.87   N4 - O6   2.86
6   [1]         N3 - N1   3.08      
7   [2]         N3 - N1   3.25   N4 - O6   2.78
8   [2]   O2 - N1   3.07         N4 - O6   3.35
9   [3]   O2 - N2   2.96   N3 - N1   2.71   N4 - O6   2.85
10   [3]   O2 - N2   3.32   N3 - N1   2.87   N4 - O6   3.09
11   [3]   O2 - N2   3   N3 - N1   2.86   N4 - O6   3.18
12   [2]         N3 - N1   3.14   N4 - O6   3.04
13   [2]   O2 - N2   2.75   N3 - N1   3.29      
14   [3]   O2 - N2   3.04   N3 - N1   3.06   N4 - O6   3.38
15   [3]   O2 - N2   2.85   N3 - N1   2.99   N4 - O6   3.21
16   [3]   O2 - N2   3.17   N3 - N1   2.93   N4 - O6   2.98      
17   [3]   O2 - N2   2.79   N3 - N1   2.74   N4 - O6   2.6      
18   [3]   O2 - N2   3.03   N3 - N1   2.78   N4 - O6   2.66      
19   [2]   O2 - N1   2.75               N3 * O6   3.32
20   [2]   O2 - N1   2.99         N4 - O6   2.98

I understand you may have a clearly defined goal in hand, and that's where application-specific scripting/programming comes into play. I may be able to help in some way if you make your case more specific.

Xiang-Jun

1382

MD simulations / Re: H-bonding information in MD analysis output

« on: September 30, 2011, 10:17:44 am »

Hi Andre,

Please check the updated post "Ruby scripts for the analysis of MD simulation trajectories". Now in v0.7, the scripts parse and extract H-bonding information you asked for, and also the overlap areas for quantifying stacking interactions.

Now I realized that I had a (solid) reason to exclude H-bond parameters in the scripts -- being variable-length text instead of float numbers (see my first reply in this thread for an example), they do not fit the pattern with other previously extracted parameters. Specifically, with N models (structures) and each M base-pairs, we have a N-by-M data matrix for each of the base-pair parameters.  For buckle, see the attached file 'buckle.tsv' (based on the distributed dataset [mono:kldkpnjg]sample_md0.pdb[/mono:kldkpnjg]. Here '[mono:kldkpnjg]tsv[/mono:kldkpnjg]' stands for tab-separated values). Now for H-bonding, the extracted data file 'hbond.tsv' looks a bit wildly -- each item has different text length and number of H-bonds. I cannot see how such information can be processed directly as with other parameters, and I'd be interested in knowing how you proceed.

Have a try, and see how it goes.

Xiang-Jun

1383

MD simulations / Re: H-bonding information in MD analysis output

« on: September 29, 2011, 07:03:12 am »

Hi Andre,

Thanks for your feedback. I will add a section of H-bond parameters (hopefully) by tomorrow, and then release an updated version of the Ruby scripts. So stay tuned, and check back the forum.

Xiang-Jun

1384

MD simulations / Re: H-bonding information in MD analysis output

« on: September 28, 2011, 07:17:37 am »

Hi Andre,

First, thanks for posting your question in the forum! The more user feedback, the merrier.

Second, you may notice that I have split your post from the thread "Ruby scripts for the analysis of MD simulation trajectories" which is too long (18 posts now), and spans two pages.  I have added a new subject line "Re: H-bonding information in MD analysis output" for the new thread.

Third, and more relevant to your question, are you referring to adding a new section for the H-bonding information? An example would be:

<hbond>
   1 C-----G  [2]  O2 - N1  2.99  N4 - O6  2.98
   2 C-----G  [3]  O2 - N2  2.74  N3 - N1  2.84  N4 - O6  3.17
   3 T-----A  [2]  N3 - N1  3.09  O4 - N6  2.86
   4 A-----T  [2]  N1 - N3  2.78  N6 - O4  3.05
   5 A-----T  [2]  N1 - N3  2.81  N6 - O4  2.76
   6 T-----A  [2]  N3 - N1  2.71  O4 - N6  3.06
   7 A-----T  [2]  N1 - N3  3.12  N6 - O4  3.12
   8 G-----C  [2]  N1 - N3  3.00  O6 - N4  2.75
   9 A-----T  [2]  N1 - N3  2.93  N6 - O4  3.12
  10 A-----T  [2]  N1 - N3  2.90  N6 - O4  2.93
  11 A-----T  [2]  N1 - N3  3.01  N6 - O4  3.05
  12 T-----A  [2]  N3 - N1  2.80  O4 - N6  3.12
</hbond>

If that's the case, then it won't be much a problem to parse and add it into the output file. Otherwise, please provide a concrete example to show exactly what you mean.

Please confirm.

Xiang-Jun

1385

General discussions (Q&As) / Re: constructing a modified sugar

« on: September 12, 2011, 08:21:52 am »

...i am successful in making the modification using chimera software which has a menu called 'Build structure'. It would be nice to have this feature incorporated in 3DNA.

Glad to hear that you are successful in making sugar modification with Chimera 'Build structure'. If that does a decent job, why should 3DNA bother to compete (recreating the wheel)? That's exactly why I asked you the question in my preview reply.

Xiang-Jun

1386

General discussions (Q&As) / Re: 3DNA on 64 bit Linux (Ubuntu)

« on: September 09, 2011, 11:19:58 pm »

Hi Fei,

I did not realize 3DNA v2.0 compiled in 32-bit Ubuntu Linux does work in a 64-bit machine. Yours is the first reported case. Any comment / experience from other users?

Anyway, check email for download link to 3DNA v2.0 compiled in Scientific Linux 6 x86_64. Do report back here if it works, or not.

Xiang-Jun

1387

General discussions (Q&As) / Re: constructing a modified sugar

« on: September 08, 2011, 05:14:02 pm »

Hi Subbu,

Thanks for posting this question. While I understand what you mean, I must say that 3DNA (in its current version) does not have direct means to get the job done. I may be able to come up with a solution after reading the publication associated with PDB id 2X2Q, check the PDB coordinates of the entry, and then play around with 3DNA to fit the bill. Obviously, this will take time.

To make this effort worthwhile, I'd ask you to perform a survey of other tools, e.g., UCSF Chimera, PyMol etc, to see if they already provide similar functionality. Of course, others viewers of this thread are more than welcome to jump in with their opinions. Hopefully, more users will get actively participated in such discussions that will help shape further development of 3DNA.

Xiang-Jun

1388

General discussions (Q&As) / Re: building a parallel stranded DNA

« on: September 07, 2011, 01:30:51 pm »

Hi,

Thanks for attaching the three PDB files -- they indeed clarify the issues.

Do you know the rationale of the no preserve option? It appears there can be many ways to rotate around the glycosidic bond to orient the base.

Xiang-Jun

1389

General discussions (Q&As) / Re: building a parallel stranded DNA

« on: September 07, 2011, 12:42:16 pm »

Hi Bala,

1) Firstly i tried by constructing the ps DNA from fiber model 31 but the structure i obtained was nt correct (in the sense the base pairs of chian A and C) were not in proper orientation. So i used the pdb structure as template to carry out mutation.

It seems that [red:27t8jes7]mutate_bases[/red:27t8jes7] serves your needs, right?

For the record, in fiber model #31, chains A and C form a parallel duplex with classic Hoogsteen A-U pairs. 3DNA has no problem in analyzing such structures. See the attached structure for an example:
[attachment=0:27t8jes7]fiber31_Hoogsteen.pdb[/attachment:27t8jes7]
[pre:27t8jes7]****************************************************************************
Structure classification:

This is a parallel duplex structure
****************************************************************************[/pre:27t8jes7]

2) I am not getting what example you need, in case if it is related to chimera software, you can refer this page. It is freely down loadable.

When you talk about the '[red:27t8jes7]swapna[/red:27t8jes7]' command with '[red:27t8jes7]preserve[/red:27t8jes7]' set to TRUE or FALSE, it would be helpful to be concrete by using examples. More specifically, you start with a structure in PDB format, and try to mutate a base to another one -- you have two results by setting '[red:27t8jes7]preserve[/red:27t8jes7]' to either TRUE or FALSE. If you attach these three PDB files, then things would be much clearer even for those who are not familiar with the UCSF chimera software.

Xiang-Jun

1390

General discussions (Q&As) / Re: 3DNA Cannot find help3dna.dat

« on: September 06, 2011, 09:58:47 pm »

Hi Sean,

It is likely that you've not properly set up 3DNA v2.0. Did you run [red:1nrkjhgd]x3dna_setup[/red:1nrkjhgd] as documented in the 2008 3DNA Nature Protocols paper?

More specifically, what's the output from running the following:

Code: [Select]

echo $X3DNABy default, if the [mono:1nrkjhgd]X3DNA[/mono:1nrkjhgd] environment variable is not set, the program will use [mono:1nrkjhgd]$HOME/X3DNA[/mono:1nrkjhgd]. That explains the error message:
[pre:1nrkjhgd]open_file </home/seanlaw/X3DNA/config/help3dna.dat> failed: No such file or directory[/pre:1nrkjhgd]
HTH,

Xiang-Jun

1391

General discussions (Q&As) / Re: building a parallel stranded DNA

« on: September 06, 2011, 12:02:13 pm »

Hi Subbu,

Kindly provide me the script 'mutate_base'. I would like to try it. I think adding it in 3DNA package would be a good option.

See my email. As I mentioned several times in the forum, it is users' feedbacks, like yours, that move the 3DNA project forward.

I would like to share one information on this regard, USCF chimera software has a command called 'swapna' with which we can just replace the base moiety. In addition it has a parameter called 'preserve' with which you can retain the glycosidic angle and position of the nitrogen forming the bond too after replacement.

But it is always better to use a script like yours when we have to do many mutations. In case your script doesnt have preserve option, could you please see if you can incorporate this preserve option in your script. I guess a similar name swap_base would be more suitable for your script.

Thanks for the info. Could you please provide an example of each? The new (ANSI C) program '[red:m67d7hlr]mutate_bases[/red:m67d7hlr]' preserves the base reference frame, and as a side effect, it retains "the glycosidic angle and position of the nitrogen forming the bond" as well.

Also can you merge all these threads so that others can view all related information in one shot. 1) Problems with mutations on DNA (Feb. 2011) 2) mutating DNA in DNA protein complex (Oct. 2007).

Excellent suggestion. I have long thought of consolidating the various source of information about 3DNA, but unable to get it done due to a lack of resources and time. This will change in the new future, so stay tuned.

Xiang-Jun

1392

General discussions (Q&As) / Re: building a parallel stranded DNA

« on: September 05, 2011, 10:53:45 pm »

Hi Subramanian,

Regarding your two questions on constructing models of parallel stranded (ps) DNA,

i) if it is possible to construct such a model using 3DNA and

3DNA does not have such a direct option. However, you may try fiber model 31 (or 32 for [red:3ckdzas2]Poly (U) : poly (A) : poly(U)[/red:3ckdzas2]), delete Us in chain B which form Watson-Crick base-pairs with As in chain A, then you get a parallel stranded Poly (U) : poly (A). You can then mutate bases to fit your needs (see below).

ii) there is an experimental structure of such ps duplex with completely different base composition, is there any way that i can use as am a template in 3DNA to model my structure.

The newly added utility program [red:3ckdzas2]mutate_bases[/red:3ckdzas2] should help. See thread "change one base pair in a double-strand DNA structure file". Please let me know if you want to have access to the program.

I may extend 3DNA's functionality to serve your specific purpose, if necessary; presumably such extension would turn out to be useful to other potential 3DNA users as well.

Xiang-Jun

1393

General discussions (Q&As) / Re: Analyzing ssDNA

« on: August 19, 2011, 09:08:53 pm »

Hi Orn,

Thanks for using 3DNA.

The error message means your ".inp" file does not match your ".pdb" file. Try:
[pre:3dmejz8w]find_pair -s your.pdb stdout[/pre:3dmejz8w]what do you get?

If that does not help solve your puzzle, please provide your ".inp" and ".pdb" files so I can check into the details.

HTH,

Xiang-Jun

1394

General discussions (Q&As) / Re: 3DNA setup at Linux

« on: August 19, 2011, 09:02:54 pm »

feixu@homestar:~/X3DNA/bin$ x3dna_setup
x3dna_setup: command not found

Try "[mono:4e0k1qpw][red:4e0k1qpw]./x3dna_setup[/red:4e0k1qpw][/mono:4e0k1qpw]". It appears that you do not have "[mono:4e0k1qpw]./[/mono:4e0k1qpw]" (your current directory) in your command search path.

HTH,

Xiang-Jun

1395

General discussions (Q&As) / Re: Creating Intercalation Site in the canonical DNA

« on: July 29, 2011, 07:48:03 pm »

Thanks for following the instructions in post "How to download 3DNA v2.0?". At this summer time, Dr. Olson may be at a meeting or on vocation. It helps to send her a follow up message, and hopefully the problem will be solved soon.

Xiang-Jun

[hr:1tj7d3n5][/hr:1tj7d3n5]PS: If things go well, future releases of 3DNA would be more easily accessible, and with 'formal' support.

1396

General discussions (Q&As) / Re: More than one helical region

« on: July 25, 2011, 09:14:48 pm »

Hi Søren,

I do not quite get what you mean. The "information about the origin (Ox, Oy, Oz) and the normal vector (Nx, Ny, Nz)" is not intended for rebuilding purpose, but for quantifying DNA curvature following Dickerson (FreeHelix, and related publications). The output file 'ref_frames.dat' contains all base pair reference frames in the original coordinate system. File 'bp_step.par' is used for rebuilding purpose, which should give an exact relative bp geometry, even with more than one helical fragment.

Or do you miss the "-c" option of "analyze"? Type [mono:12seu325]analyze -h[/mono:12seu325] for more info.

Please clarify.

Xiang-Jun

1397

General discussions (Q&As) / Re: Creating Intercalation Site in the canonical DNA

« on: July 24, 2011, 09:36:19 pm »

Hi Pooja,

Thanks for using 3DNA and writing such a thoughtful post. I think I understand your question, even though I do not have (or know of) a straight answer to it.

As you tried out, '[mono:1hmzqauk]rebuild[/mono:1hmzqauk]' with the [mono:1hmzqauk]-atomic[/mono:1hmzqauk] option does not generate proper sugar-phosphate backbone geometry for intercalated dinucleotide steps. Meanwhile, the available "complexes deposited in PDB are limited to hexanucleotide sequence and mostly the ligand intercalated in the terminal dinucleotide step." However, by combining the two, plus other utilities in 3DNA, it'd be possible to achieve approximately what you want.

You could start with a PDB complex with an intercalated dinucleotide step and then extend both ends with desired sequence in B-DNA fiber conformation. The intercalated dinucleotide can then be mutated to whatever bases you like, using [red:1hmzqauk]mutate_bp[/red:1hmzqauk] or [red:1hmzqauk]mutate_bases[/red:1hmzqauk] (see my reply to "change one base pair in a double-strand DNA structure file").

Surely, this is not an automatic process; there is no GUI-driven menu and mouse clicks to achieve 'magic'  -- you have to know what to do for each step. However, if you cannot find a better method elsewhere, 3DNA may prove useful. Please share your experience and thought. If you decide to try the 3DNA route, please provide a specific example.

HTH,

Xiang-Jun

1398

General discussions (Q&As) / Re: Problems with Ruby MD and Creating ssRNA

« on: June 09, 2011, 10:12:09 pm »

it removes the bond between 5' phosphate and the 3' OH between all the nucleotides, why has this happened and also can I fix it?

I do not get it. Please be specific, using a concrete example to illustrate your problem.

Although I am still wondering about the secondary structures, I have a number of RNA sequences (18' to 21' mers) all of which have different secondary structures according to QuickFold (http://mfold.rna.albany.edu/?q=DINAMelt/Quickfold) and am just interested to know whether it is possible with x3dna.

3DNA do not predict RNA secondary structures -- there are quite a few existing methods out there already. Given a 2nd structure, I am not aware of an automatic way to convert it into 3-dimensional coordinates; 3DNA certainly does not have such functionality. In the current issue of Nucleic Acids Research (Volume39, Issue10), there is an article titled "ModeRNA: a tool for comparative modeling of RNA 3D structure" for  comparative modeling of 3D RNA structures. You may find useful information in it.

I do believe 3DNA has the facilities/potential for RNA 3D structure modeling. If you provide details as to what you want to achieve, what you've tried and the problems you still have, I may be able to help in a more concrete way.

Xiang-Jun

1399

MD simulations / Re: Ruby scripts for the analysis of MD simulation trajector

« on: June 08, 2011, 09:36:23 pm »

Hi Henry,

Thanks for using 3DNA. I fully understand how frustrated it could be to get a new software system up and running, and you are welcome to ask any 3DNA-related questions in the forum.

The Ruby scripts may be useful if you are using AMBER for MD simulations. For building general sequence single strand RNA structures, the recent post "building a ssDNA" may help. Run also "fiber -m" to see all available fiber RNA models.

Regarding the specific problem you have with running the Ruby script '[mono:1bnxcgla][red:1bnxcgla]x3dna_md.rb[/red:1bnxcgla][/mono:1bnxcgla]':
[pre:1bnxcgla]3DNA settings error: can't execute C:/MinGW/msys/1.0/home/bshcf/X3DNA/bin/analyze[/pre:1bnxcgla]
It is likely due to line #425:
[pre:1bnxcgla]fatal("3DNA setting error: can't execute #{x}") unless File.executable?("#{x}")[/pre:1bnxcgla]
change it to (i.e., by adding [mono:1bnxcgla][red:1bnxcgla].exe[/red:1bnxcgla][/mono:1bnxcgla] at the end since you are using MinGW)
[pre:1bnxcgla]fatal("3DNA setting error: can't execute #{x}") unless File.executable?("#{x}[red:1bnxcgla].exe[/red:1bnxcgla]")[/pre:1bnxcgla]
Have a try, and report back how it goes.

Generally speaking, the best way to get started with 3DNA is by reading the 2008 3DNA Nature Protocols paper, and working out the recipes.

HTH,

Xiang-Jun
[hr:1bnxcgla][/hr:1bnxcgla]
Since this thread is becoming too long, please start a new one with a specific Subject line.

1400

General discussions (Q&As) / Re: change one base pair in a double-strand DNA structure fi

« on: June 04, 2011, 11:16:50 pm »

Hi all,

I have finally made the programs ready for distribution. There are actually two variants as detailed below for mutating bases in a nucleic acid structure while keeping the sugar-phosphate backbone untouched. Both the mutate_bp Perl script for base-pair mutations and the more generic/efficient/robust ANSI C program mutate_bases possess the neat and indeed unique feature, i.e., the mutated structures share the same base-pair/step parameters as the original structure.

• mutate_bp is a Perl script I first wrote a couple of years ago. Its usage is as follows:
  

  mutate_bp -m=bpNUM_BP input.pdb output.pdb
  
  The mutation string must be in the format of 'bpNUM_BP' where NUM is
      an integer for the base-pair to be mutated (check 'find_pair'),
      and BP is the desired base-pair. BP must be two letters from the
      set ACGTU; e.g. AT/TA/AU/UA/GC/CG for Watson-Crick pairs. Case
      does not matter (i.e., 'at' is the same as 'AT').
  
  e.g. mutate_bp -m=bp2_at 355d.pdb 355d_bp2at.pdb
         # mutate the second base-pair, G-C, to A-T in PDB entry 355d

  
  This script presumably should fulfill Chien-Ho's need, "change one base pair in a double-strand DNA structure file", as well as the two previous similar requests on this topic. Technically, the script makes (system) calls of various 3DNA (v2.0) programs (e.g., find_pair, analyze, rebuild, frame_mol etc.), and basically follows the procedures I outlined in response to "mutating DNA in DNA protein complex" (Oct. 2007).
  
  The mutate_bp Perl script is directly available for download. Simple save it to your $X3DNA/bin directory, and make sure it is executable (run chmod a+x mutate_bp if necessary). Interested users are encouraged to explore the source code and make changes as they see fit.

• mutate_bases is a standalone ANSI C program, on a par with other major 3DNA programs (e.g., find_pair, analyze, rebuild, fiber etc). As seen from the help message below, it can be used for any nucleic-acid-containing structures (DNA, RNA, or their complexes, in PDB format):
  

  Usage: mutate_bases mutinfo pdbfile outfile
     'mutinfo' can contain upto 5 fields for each mutation:
         [name=residue_name] [icode=insertion_code]
         chain=chain_id seqnum=residue_number
         mutation=residue_name
     o The five fields per mutation can be in any order or CaSe
     o Each field can be abbreviated to its first character
     o Multiple mutations are separated by ';'
     o Fields in [] (i.e., name and icode) are optional
     o Mutation info should be QUOTED to be taken as one entry
  
  Examples:
      mutate_bases 'c=a s=2 m=DA' 355d.pdb 355d_G2A.pdb
     # mutate G2 in chain A of B-DNA 355d to A
      mutate_bases 'c=a s=2 m=DA; c=B s=23 m=DT' 355d.pdb 355d_GC2AT.pdb
     # mutate base-pair G-C (C23 in chain B) to A-T
      mutate_bases 'c=A s=74 m=U' 1evv.pdb 1evv_C74U.pdb
     # mutate C74 in chain A of tRNA 1evv to U

  
  mutate_bases is designed to solve the base mutation problem in a practical sense: robust and efficient, getting its job done and then out of the way. The program can have many possible applications: in addition to perform base-pair mutations in DNA-protein complexes as mutate_bp does, mutate_bases should prove handy in providing initial structures for QM/MM/MD energy calculations, and in RNA modeling studies.
  
  While mutate_bases is now fully functional, it is not intended for general release yet. Interested users should contact me directly for access to the program (Linux, Mac OSX Intel, and MinGW-MSYS binary versions only; 3DNA v2.0 required).

As always, I welcome users feedback; any questions and comments should be posted in this forum.

Xiang-Jun