gnm.Rd
Perform Gaussian network model (GNM) based normal mode analysis (NMA) for a protein structure.
gnm(x, ...) # S3 method for pdb gnm(x, inds = NULL, temp = 300, keep = NULL, outmodes = NULL, gamma = 1, cutoff = 8, check.connect = TRUE, ...) # S3 method for pdbs gnm(x, fit = TRUE, full = FALSE, subspace = NULL, rm.gaps = TRUE, gc.first = TRUE, ncore = NULL, ...)
x  an object of class 

...  (in 
inds  atom and xyz coordinate indices obtained from 
temp  numerical, temperature for which the amplitudes for scaling the atomic displacement vectors are calculated. Set ‘temp=NULL’ to avoid scaling. 
keep  numerical, final number of modes to be stored. Note that all subsequent analyses are limited to this subset of modes. This option is useful for very large structures and cases where memory may be limited. 
outmodes  atom indices as obtained from 
gamma  numerical, global scale of the force constant. 
cutoff  numerical, distance cutoff for pairwise interactions. 
check.connect  logical, if TRUE check chain connectivity. 
fit  logical, if TRUE Calpha coordinate based superposition is performed prior to normal mode calculations. 
full  logical, if TRUE return the complete, full structure, ‘nma’ objects. 
subspace  number of eigenvectors to store for further analysis. 
rm.gaps  logical, if TRUE obtain the hessian matrices for only atoms in the aligned positions (nongap positions in all aligned structures). Thus, gap positions are removed from output. 
gc.first  logical, if TRUE will call gc() first before mode calculation
for each structure. This is to avoid memory overload when

ncore  number of CPU cores used to do the calculation. 
Returns an object of class ‘gnm’ with the following components:
numeric vector containing the force constants corresponding to each mode.
numeric vector of atomic fluctuations.
numeric matrix with columns containing the raw eigenvectors.
numeric vector containing the raw eigenvalues.
numeric matrix of class xyz
containing the Cartesian coordinates
in which the calculation was performed.
numerical, temperature for which the amplitudes for scaling the atomic displacement vectors are calculated.
number of trivial modes.
number of Calpha atoms.
the matched call.
This function builds a Gaussian network model (an isotropic elastic network model) for Calpha atoms and performs subsequent normal mode analysis (NMA). The model employs a distance cutoff for the network construction: Atom pairs with distance falling within the cutoff have a harmonic interaction with a uniform force constant; Otherwise atoms have no interaction. Output contains N1 (N, the number of residues) nontrivial modes (i.e. the degree of freedom is N1), which can then be used to calculate atomic fluctuations and covariance.
XinQiu Yao & Lars Skjaerven
Bahar, I. et al. (1997) Folding Des. 2, 173.
gnm.pdbs
## Fetch stucture pdb < read.pdb( system.file("examples/1hel.pdb", package="bio3d") ) ## Calculate normal modes modes < gnm(pdb) ## Print modes print(modes)#> #> Call: #> gnm.pdb(x = pdb) #> #> Class: #> EnergeticModes (gnm) #> #> Number of modes: #> 129 (1 trivial) #> #> Force constants: #> Mode 2: 0.342 #> Mode 3: 0.804 #> Mode 4: 1.108 #> Mode 5: 1.277 #> Mode 6: 1.416 #> Mode 7: 1.617 #> #> + attr: force.constants, fluctuations, U, L, xyz, temp, #> triv.modes, natoms, call