[gmx-users] Embedding Protein into lipid bilayer

[khourshaeishargh at mech.sharif.ir]

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	Hi Catarina


	Thanks for your reply, I really appreciate it. you know, I complete
Justin&#39;s Tutorial, so I know what procedures I should do. but now I
want to embed 2rh1 protein into DPPC lipid bilayer  which I already
downloaded it from rcsb.com.  when I tried to use pdb2gmx  via
"gmx pdb2gmx -f 2rh1.pdb -o 2rh1_processed.gro -ignh -ter -water
spc", it says :


	

	 


	Select start terminus type for ASP-29

	 0: NH3+

	 1: NH2

	 2: None

	2

	Start terminus ASP-29: None

	Select end terminus type for LEU-342

	 0: COO-

	 1: COOH

	 2: None

	2

	End terminus LEU-342: None

	-------------------------------------------------------

	Program gmx, VERSION 5.0.5

	Source code file:
/home/ali/gromacs-5.0.5/src/gromacs/gmxpreprocess/pdb2top.cpp, line:
1091

	

	Fatal error:

	There is a dangling bond at at least one of the terminal ends. Fix your
coordinate file, add a new terminal database entry (.tdb), or select the
proper existing terminal entry.

	-------------------------------------------------------


	I found a similar question in which Justin replied it as below :


	You haven&#39;t added caps onto the input protein, you should expect to
get this error. In the tutorial, I build ACE and NH2 groups onto the
peptide to neutralize the termini. Since you haven&#39;t done this type
of modification, pdb2gmx will die because you have incomplete amides at
the ends of the chain. The "None" terminus instructs pdb2gmx to
not build additional H (in the case of NH2 or NH3+ termini) or O(H) (for
COO- and COOH). It doesn&#39;t make any chemical sense to use
"None" for non-capped protein chains.


	I don&#39;t grasp what specifically Justin meant to say. Could anyone one
please help me ? How should I naturalized the termini ?

best regards

Ali khourshaei shargh (khourshaeishargh at mech.sharif.ir)
Department of Mechanical Engineering
Sharif University of Technology, Tehran, Iran