ccd2md 1.0.3

A suite of packages for the conversion of co-folding outputs into simulatable PDB files.

CCD2MD codes for conversion between cofolding outputs and simulations

CCD2MD contains several codes for the purpose of increasing the ease of cofolding outputs and simulations. CCD2MD can be installed via pip (for versions 1.0.0 and above) via

pip install CCD2MD

The paper associated with this code can be found on JCIM here. Please note that there have been updates to the code (documented below) since the release of the paper.

For full functionality, including membrane embedding please run pip install "CCD2MD[all]". Please note that this will not install gromacs, which is required for cg2at-lite/atomistic membrane embedding.

This utilises the following packages: MemPrO/MemPrOD M. Parrag and P. J. Stansfeld, ADD DETAILS. Additional details can be found in the [paper](PAPER LINK), the MemPrO GitHub, and the MemPrOD GitHub. PyPi version 0.0.9 of MemPrOD (which includes MemPrO) is required.

Vermouth-Martinize P. C. Kroon et al., "Martinize2 and Vermouth: Unified Framework for Topology Generation", arxiv: 2212.01191. Additional details can be found in the paper and the GitHub.

cg2at-lite This is a reduced version of CG2AT. CG2AT is detailed in O. N. Vickery and P. J. Stansfeld, (2021). "CG2AT2: an Enhanced Fragment-Based Approach for Serial Multi-scale Molecular Dynamics Simulations" J. Chem. Theory Comput. 17(10), 6472-6482. Additional details can be found in the paper, the CG2AT2 GitHub and the CG2AT-lite GitHub. PyPi version 0.2.3 of cg2at-lite is required.

Functions are converted using:

• ccd2at (cofolding to CHARMM)
• at2ccd (CHARMM to CCD/SMILES)
• ccd2cg (cofolding to Martini 3, where possible)
• at2cg (CHARMM to Martini 3, where possible)
• at2mem (embed CHARMM structure in membrane)
• pos2cif (structure file(s) to userCCD)

There are limitations for the ligands available for conversion to Martini 3.

Usage

Dependencies are numpy and pandas with vermouth-martinize (martinize2) required for protein conversion, MemPrO required for protein membrane embedding and gromacs (specifically pdb2gmx) required for atomistic topology generation. There may be additional requirements for vermouth-martinize, MemPrO and pdb2gmx. Environment variables for MemPrO are set locally within CCD2MD and therefore do not need to be explicitly set if only utilising these packages via CCD2MD.

Topology files are generated except for at2ccd.py and pos2cif.py

For membrane embedding, MemPrO supports parallelisim, the default number of CPUs to be used is 1. This may be set by the user in line 11 of FuncConv.py -- this will not affect any other part of the conversion. Please note that some of the lipids available in Insane4MemPrO (new lipidome version) may correspond to Martini 2 mappings, although this should not apply to those lipids convertible with CCD2MD.

ccd2at

ccd2at INPUT_FILE OUTPUT_FILE [-L] [-S <smiles> ...] [-gh <pdb2gmx>] [-mem [<membrane>]] [-C <conc>] [-mp <mempro>] [-mdef <memprod>] [-ncpu <num_cpus&;] [-at <cg2at>]

INPUT_FILE name of the file to convert - the extension must be either .cif, .pdb or .gro

OUTPUT_FILE name of the converted file. This will be written as a pdb file - with an OUTPUT_FILE_H.pdb version with added hydrogens if not membrane embedded.

Optional arguments

-L/--ligchain include ligands as their own chains - default off (binary switch). Note that this is currently incompatible with membrane insertion.

-S/--SMILES <smiles> ... indicates that some ligands have been input as SMILES strings - note that other than for POPE (see below) this requires user-defined ligand mapping. To use, list the CCDName of the ligands represented by SMILES strings in order of use (e.g. POES for a POPE smiles string, ideally should not overlap with CCD or CHARMM names). Note that when multiple of the same ligand are used this can be written either e.g. -S POES POES or -S POES 2.

-gh/--pdb2gmx overrides ALL defaults of pdb2gmx and optionally can be used pass extra arguments. This may require interactivity, and may be necessary for a starting MET. Default is topology in topol.top, OUTPUTNAME_H.pdb, TIP3P water, charmm36-ccd2md forcefield, and charged termini (excepting starting CYST or GLYM which are set to None). Only applicable if NOT embedding the system in a membrane.

Optional arguments -- membrane embedding

-mem/--membrane [<membrane>] acts as a flag to embed the system in a membrane. Optionally, it may be followed by additional arguments to be used by [Insane4MemPrO] (https://github.com/ShufflerBardOnTheEdge/MemPrO), most notably the membrane composition in the form -u POPE:7 -u POPG:2 -u CARD:1 -l POPE:7 -l POPG:2 -l CARD:1 where the numbers give the ratio of lipids, -u represents the upper leaflet and -l represents the lower leaflet. If not specified, both leaflets are pure POPC. Note that membrane embedding will lead to minor rearrangement of bound ligands.

-C/--conc <conc> passes a single number giving the concentration of NaCl in the system, where the charge is balanced.

-mp/--mempro <mempro> passes optional arguments to MemPrO. Default is 5 grid points and 15 minimisation operations

-mdef/--memprod <memprod> is an optional flag to calculate the deformation of the membrane around the protein usingMemPrOD -- if ommitted no deformations will be calculated. Optional arguments for MemPrOD will be passed after this flag, otherwise the MemPrOD defaults will be used.

-ncpu/--num_cpus passes the environment variable NUM_CPUs to MemPrO. If unset, 1 CPU will be used.

-at/--cg2at <cg2at> passes optional arguments to cg2at-lite

at2ccd

at2ccd INPUT_FILE OUTPUT_FILE [-L]

INPUT_FILE name of the file to convert - the extension must be either .cif, .pdb or .gro

OUTPUT_FILE name of the converted file. This will be written as a pdb file

Optional arguments

-L/--ligchain include ligands as their own chains - default off (binary switch)

ccd2cg

ccd2cg INPUT_FILE OUTPUT_FILE [-S <smiles> ...] [-nl] [(-E [<elastic>]) | (-G <go>)] [-M <martinize>] [-mem [<membrane>]] [-C <conc>] [-mp <mempro>] [-mdef <memprod>] [-ncpu <num_cpus&;] [-at <cg2at>]

INPUT_FILE name of the file to convert - the extension must be either .cif, .pdb or .gro

OUTPUT_FILE name of the converted file. This will be written as a pdb file

Optional arguments

-S/--SMILES <smiles> ... indicates that some ligands have been input as SMILES strings - note that other than for POPE (see below) this requires user-defined ligand mapping. To use, list the CCDName of the ligands represented by SMILES strings in order of use (e.g. POES for a POPE smiles string, ideally should not overlap with CCD or CHARMM names). Note that when multiple of the same ligand are used this can be written either e.g. -S POES POES or -S POES 2.

-nl/--newlipidome is a flag indicating that the new mappings for the Martini 3 lipidome (from DOI: 10.1021/acscentsci.5c00755) should be used.

Optional arguments -- protein coarse-graining

-E/--elastic [<elastic>] specifies that protein secondary structure should be biased using an elastic network (default). Additional options for the elastic network in martinize may be added added this flag; if omitted the defaults will be used.

-G/--go <go> specifies that protein secondary structure should be biased using a go network. Required and optional parameters should be added after this flag.

-M/--martinize <martinize> is used for any additonal optional arguments which should be passed to martinize2 for protein CG conversion.

Optional arguments -- membrane embedding

-mem/--membrane [<membrane>] acts as a flag to embed the system in a membrane. Optionally, it may be followed by the membrane composition in the form -u POPE:7 -u POPG:2 -u CARD:1 -l POPE:7 -l POPG:2 -l CARD:1 where the numbers give the ratio of lipids, -u represents the upper leaflet and -l represents the lower leaflet. If not specified, both leaflets are pure POPC.

-C/--conc <conc> passes a single number giving the concentration of NaCl in the system, where the charge is balanced.

-mp/--mempro <mempro> passes optional arguments to MemPrO. Default is 5 grid points and 15 minimisation operations

-mdef/--memprod <memprod> is an optional flag to calculate the deformation of the membrane around the protein usingMemPrOD -- if ommitted no deformations will be calculated. Optional arguments for MemPrOD will be passed after this flag, otherwise the MemPrOD defaults will be used.

-ncpu/--num_cpus passes the environment variable NUM_CPUs to MemPrO. If unset, 1 CPU will be used.

at2cg

at2cg INPUT_FILE OUTPUT_FILE [(-E [<elastic>]) | (-G <go>)] [-M <martinize>] [-mem [<membrane>]] [-C <conc>] [-mp <mempro>] [-mdef <memprod>] [-ncpu <num_cpus&;]

INPUT_FILE name of the file to convert - the extension must be either .cif, .pdb or .gro

OUTPUT_FILE name of the converted file. This will be written as a pdb file

Optional arugments

-nl/--newlipidome is a flag indicating that the new mappings for the Martini 3 lipidome (from DOI: 10.1021/acscentsci.5c00755 should be used.

Optional arguments -- protein coarse-graining

-E/--elastic [<elastic>] specifies that protein secondary structure should be biased using an elastic network (default). Additional options for the elastic network in martinize may be added added this flag; if omitted the defaults will be used.

-G/--go <go> specifies that protein secondary structure should be biased using a go network. Required and optional parameters should be added after this flag.

-M/--martinize <martinize> is used for any additonal optional arguments which should be passed to martinize2 for protein CG conversion.

Optional arguments -- membrane embedding

-mem/--membrane [<membrane>] acts as a flag to embed the system in a membrane. Optionally, it may be followed by the membrane composition in the form -u POPE:7 -u POPG:2 -u CARD:1 -l POPE:7 -l POPG:2 -l CARD:1 where the numbers give the ratio of lipids, -u represents the upper leaflet and -l represents the lower leaflet. If not specified, both leaflets are pure POPC.

-C/--conc <conc> passes a single number giving the concentration of NaCl in the system, where the charge is balanced.

-mp/--mempro <mempro> passes optional arguments to MemPrO. Default is 5 grid points and 15 minimisation operations

-mdef/--memprod <memprod> is an optional flag to calculate the deformation of the membrane around the protein usingMemPrOD -- if ommitted no deformations will be calculated. Optional arguments for MemPrOD will be passed after this flag, otherwise the MemPrOD defaults will be used.

-ncpu/--num_cpus passes the environment variable NUM_CPUs to MemPrO. If unset, 1 CPU will be used.

at2mem

at2mem INPUT_FILE OUTPUT_FILE [-M <martinize>] [-mem [<membrane>]] [-C <conc>] [-mp <mempro>] [-mdef <memprod>] [-ncpu <num_cpus&;] [-at <cg2at>]

INPUT_FILE name of the file to convert - the extension must be either .cif, .pdb or .gro

OUTPUT_FILE name of the converted file. This will be written as a pdb file

Optional arguments -- membrane embedding

-mem/--membrane [<membrane>] may be followed by the membrane composition in the form -u POPE:7 -u POPG:2 -u CARD:1 -l POPE:7 -l POPG:2 -l CARD:1 where the numbers give the ratio of lipids, -u represents the upper leaflet and -l represents the lower leaflet. If not specified, both leaflets are pure POPC. Note that membrane embedding will lead to minor rearrangement of bound ligands.

-C/--conc <conc> passes a single number giving the concentration of NaCl in the system, where the charge is balanced.

-mp/--mempro <mempro> passes optional arguments to MemPrO. Default is 5 grid points and 15 minimisation operations

-mdef/--memprod <memprod> is an optional flag to calculate the deformation of the membrane around the protein usingMemPrOD -- if ommitted no deformations will be calculated. Optional arguments for MemPrOD will be passed after this flag, otherwise the MemPrOD defaults will be used.

-ncpu/--num_cpus passes the environment variable NUM_CPUs to MemPrO. If unset, 1 CPU will be used.

-at/--cg2at <cg2at> passes optional arguments to cg2at-lite

pos2cif

pdb2cif allows for the creation of userCCD codes which can be input into AF3. When the atomic naming and orderings match that of the desired forcefield then no additional post-processing is required. Modified amino acids can also be input and the resulting CCD code manually added as a PTM for the correct location in the protein. Ligands composed of chains of multiple residues can be added, although the quality of the joins may be variable.

pos2cif [-n <ligand> ... -f <files> ...] [-r (<old> <new>) ...] [-c ((<pdb> <itp>) | <mol2>) ...] [-e <charge>] [-b <bond>] [-H] [-j <json>] [-t <title>] [-A <afvers>] [-s <seed> ...] [-d <dialect>] [-p (<protein> | (<protein N >)) ...]

Specifying ligands

-n/--names <ligand> ... gives the names of the ligands to extract from files and produce cif files for

-f/--files <files> ... gives the name of position (required) and bonding (optional) files for the ligands to be converted. Position files may be .pdb, .crd, .gro, or .mol2 with additional bonding information provided by .rtp, .rtf, or .itp files. Position files may contain information for several ligands, but should only include one copy of the ligand of interest.

-c/--covalent ((<pdb> <itp>) | <mol2>) ... gives either a .pdb and .itp file (note, that this must follow the .pdb then .itp order) or a .mol2 file for every covalently bonded ligand to be added to the system. Note that in contrast to the files for single component ligands, these files should include information for the covalently bonded ligand only.

Optional arguments

-r/--rename (<old> <new>) ... allows ligands to have a different userCCD name than in the original file. For each ligand to be renamed, old is the name in the position file, and new is the desired output name

-e/--charge <charge> is an optional cutoff for increments of the integer charge in the cif files. For each partial integer charge above the cutoff the integer charge output will be changed by 1. The default is 0.75 $e$.

-b/--bond <bond> is an optional cutoff for generating bonding information from positional information -- note that this is not utilised where bonding information is given in a bonding file. If the distance between two atoms is less than the cutoff, a bond between these atoms is output. The default is 1.4 \AA.

-H/--Hydrogens is a flag to output hydrogen position and bonding information.

json file parameters

-j/--json <json> gives the option to change the name of the json file containing the required userCCD field for AlphaFold3 inputs (default output.json). For each ligand, an additional file containing the cif data is output to NAME_output.cif)

-t/--title <title> gives the name of the system to be passed to the output json file. The default is pos2cif_system

-A/--afvers <version> gives the version number to be output in the json file. The default is 2.

-s/--seeds <model seed> ... gives the model seeds to pass to AF3 - these need not be comma separated. The default seed is 1.

-d/--dialect <dialect> gives the dialect to be output in the json file. The default is alphafold3.

-p/--protein (<protein> | (<protein> <N>)) ... allows input of FASTA protein sequence(s) for the json file. Sequences can be put in in FASTA form or in a FASTA file, numbers can be inserted to detail how many of the sequence should be added. FASTA files can contain multple sequences but each sequence must be preceeded by a protein information line starting with ">". A mixture of sequences and FASTA files may be used, a FASTA file followed by a number will input N copies of all sequences within the file.

Current ligands

Name	CCDName	CHARMMName	CGName	Note
Cardiolipin		CARD	CARD	Palmitoyl-oleoyl cardiolipin (POCL2), new lipidome mapping available
Cholesterol	CLR	CHL1	CHL1	New lipidome mapping available
DGPC		DGPC	DGPC	New lipidome mapping available
DGPE		DGPE	DGPE	New lipidome mapping available
DLPC		DLPC	DLPC	New lipidome mapping available
DLPE	WNZ	DLPE	DLPE	New lipidome mapping available
DMPC	MC3	DMPC	DMPC	New lipidome mapping available
DMPE	46E	DMPE	DMPE	New lipidome mapping available
DMPI		DMPI	DMPI	New lipidome mapping available
DMPS		DMPS	DMPS	New lipidome mapping available
DNPC		DNPC	DNPC	New lipidome mapping available
DNPE		DNPE	DNPE	New lipidome mapping available
dodecylBDmaltoside	LMT	BDDM
DOPC		DOPC	DOPC	New lipidome mapping available
DOPE		DOPE	DOPE	New lipidome mapping available
DOPS	17F	DOPS	DOPS	New lipidome mapping available
DPG3		DPG3	DPG3	Non-native in CHARMM36
DPPC	PCF	DPPC	DPPC	New lipidome mapping available
DPPE		DPPE	DPPE	New lipidome mapping available
DYPC		DYPC	DYPC	New lipidome mapping available
DYPE		DYPE	DYPE	New lipidome mapping available
laurylBMNglycol	LMN	BLMN		BLMNG in CHARMM
LIP1		LIP1	LIP1	Non-native in CHARMM36
LIP2		LIP2	LIP2	Non-native in CHARMM36
LIP3		LIP3	LIP3	Non-native in CHARMM36
LIPA		LIPA	LIPA	Non-native in CHARMM36
OBDglucopyranoside	BOG	BOG1		BOG in CHARMM36
POPI 3 phosphate		POP1	POP1	POPI13 in CHARMM36, new lipidome mapping available
POPI 3,4 bisphosphate		POP2	POP2	POPI2D in CHARMM36, new lipidome mapping available
POPI 3,4,5 trisphosphate		POP3	POP3	POPI34 in CHARMM36, new lipidome mapping available
POPI 4 phosphate		POP4	POP4	POPI14 in CHARMM36, new lipidome mapping available
POPI 5 phosphate		POP5	POP5	POPI15 in CHARMM36, new lipidome mapping available
POPI 4,5 bisphosphate		POP6	POP6	POPI24 in CHARMM36, new lipidome mapping available
POPI 3,5 bisphosphate		POP7	POP7	POPI2A in CHARMM36, new lipidome mapping available
POPA	D21	POPA	POPA	New lipidome mappi, new lipidome mapping available
POPC	POV	POPC	POPC	New lipidome mappi, new lipidome mapping available
POPE	PEV	POPE	POPE	New lipidome mappi, new lipidome mapping available
POPE_SMILES	POES	POPE	POPE	From SMILES string, new lipidome mapping available
POPG	PGW	POPG	POPG	New lipidome mapping available
POPI		POPI	POPI	New lipidome mapping available
POPS	D39	POPS	POPS	New lipidome mapping available
RAMP		RAMP	RAMP	Non-native in CHARMM36
REMP	KDL	REMP	REMP
SSM1		SSM1	SSM1	SSM in CHARMM36, new lipidome mapping available
TMM		TMM1	TMM1	Non-native in CHARMM36
TMMA		TMMA	TMMA	Non-native in CHARMM36
undecaprenyl phosphate	5TR	UNP1	UDP1
undecaprenyl pyrophosphate		UDP2	UDP2	UNDPP in CHARMM36

$\dag$ new lipidome mapping available

Post-translational Modifications

Name	CCDName	CHARMMName	CGName
CYSD		CYSD	CYSD
CYSF		CYSF	CYSF
CYSG		CYSG	CYSG
CYSP		CYSP	CYSP
CYST		CYST	CYST
GLYM		GLYM	GLYM

SMILES strings

Note any modification which does not affect the order of atoms can be made (e.g. changes to chiral centres/charges/double bonds). The name of the SMILES string must differ from the CHARMM name if wishing to utilise userCCD codes, and should not be more than 4 charaters if wishing to convert to CG. Ideally, it should also differ from utilised CCD codes.

| POPE_SMILES | POES | POPE |CCCCCCCC\C=C/CCCCCCCC(=O)O[C@H](COC(=O)CCCCCCCCCCCCCCC)COP(O)(=O)OCCN |

For issues and suggestions, please feel free to add these via GitHub or contact Kat Blow at katarina.blow[at]warwick.ac.uk