Rotation Translation Blocks¶
This module defines a class and a function for rotating translating blocks (RTB) calculations.

class
RTB
(name='Unknown')[source]¶ Class for Rotations and Translations of Blocks (RTB) method ([FT00]). Optional arguments permit imposing constrains along Zdirection as in imANM method described in [TL12].
[FT00] Tama F, Gadea FJ, Marques O, Sanejouand YH. Buildingblock approach for determining lowfrequency normal modes of macromolecules. Proteins 2000 41:17. [TL12] Lezon TR, Bahar I, Constraints Imposed by the Membrane Selectively Guide the Alternating Access Dynamics of the Glutamate Transporter GltPh 
addEigenpair
(vector, value=None)¶ Add eigen vector and eigen value pair(s) to the instance. If eigen value is omitted, it will be set to 1. Inverse eigenvalues are set as variances.

buildHessian
(coords, blocks, cutoff=15.0, gamma=1.0, **kwargs)¶ Build Hessian matrix for given coordinate set.
Parameters:  coords (
numpy.ndarray
) – a coordinate set or an object withgetCoords
method  blocks (list,
numpy.ndarray
) – a list or array of block identifiers  cutoff (float) – cutoff distance (Å) for pairwise interactions, default is 15.0 Å
 gamma (float) – spring constant, default is 1.0
 scale (float) – scaling factor for force constant along Zdirection, default is 1.0
 membrane_low (float) – minimum zcoordinate at which membrane scaling is applied default is 1.0
 membrane_high –
 maximum zcoordinate at which membrane scaling
 is applied. If membrane_high < membrane_low, scaling will be applied to the entire structure default is 1.0
type membrane_high: float
 coords (

buildMechStiff
(coords, n_modes=None, kbt=1.0)¶ Calculate stiffness matrix calculated using
ANM
instance. Method described in [EB08].[EB08] Eyal E., Bahar I. Toward a Molecular Understanding of the Anisotropic Response of Proteins to External Forces: Insights from Elastic Network Models. Biophys J 2008 94:342434355. Parameters:  coords (
numpy.ndarray
.) – a coordinate set or an object withgetCoords
method  n_modes (int or
None
, default is 20.) – number of nonzero eigenvalues/vectors to calculate. IfNone
is given, all modes will be calculated (3x number of atoms).
Author: Mustafa Tekpinar & Karolina MikulskaRuminska & Cihan Kaya
 coords (

calcModes
(n_modes=20, zeros=False, turbo=True)¶ Calculate normal modes. This method uses
scipy.linalg.eigh()
function to diagonalize the Hessian matrix. When Scipy is not found,numpy.linalg.eigh()
is used.Parameters:  n_modes (int or None, default is 20) – number of nonzero eigenvalues/vectors to calculate.
If
None
is given, all modes will be calculated.  zeros (bool, default is
False
) – IfTrue
, modes with zero eigenvalues will be kept.  turbo (bool, default is
True
) – Use a memory intensive, but faster way to calculate modes.
 n_modes (int or None, default is 20) – number of nonzero eigenvalues/vectors to calculate.
If

getArray
()¶ Returns a copy of eigenvectors array.

getCovariance
()¶ Returns covariance matrix. If covariance matrix is not set or yet calculated, it will be calculated using available modes.

getEigvals
()¶ Returns eigenvalues. For
PCA
andEDA
models built using coordinate data in Å, unit of eigenvalues is Å^{2}. ForANM
,GNM
, andRTB
, on the other hand, eigenvalues are in arbitrary or relative units but they correlate with stiffness of the motion along associated eigenvector.

getEigvecs
()¶ Returns a copy of eigenvectors array.

getHessian
()¶ Returns a copy of the Hessian matrix.

getMechStiffStatistic
(rangeK, minAA=0, AA='all')¶ Returns number of effective spring constant with set range of amino acids of protein structure.
AA
can be a list with a range of analysed amino acids as: [first_aa, last_aa, first_aa2, last_aa2], minAA  eliminate amino acids that are within 20aa andrangeK
is a list [minK, maxK]

getModel
()¶ Returns self.

getProjection
()¶ Returns a copy of the projection matrix.

getStiffness
()¶ Return a copy of Stiffness matrix.

getStiffnessRange
()¶ Return the range of effective spring constant.

getStiffnessRangeSel
(value, minAA=20, AA='all')¶ Returns minimum or maximum value of sping constant from mechanical stiffness calculations for residues that are within more than
min_aa
from each other.Value
should be ‘minK’ or ‘maxK’. It alow to avoid residues near each other.AA
is a number of residues from both terminus (N and C) of protein strcuture, it can beall
or int value (than first and lastAA
residues will be analysed. WithminAA=0
it can be used to search the highest/lowest values of interactions between NC terminus if protein structure has a shear, zipper or SD1disconnected mechanical clamp it is common in FnIII/Ig like domains and determines the maximum unfolding force in AFM or SMD method.

getTitle
()¶ Returns title of the model.

getVariances
()¶ Returns variances. For
PCA
andEDA
models built using coordinate data in Å, unit of variance is Å^{2}. ForANM
,GNM
, andRTB
, on the other hand, variance is the inverse of the eigenvalue, so it has arbitrary or relative units.

is3d
()¶ Returns True if model is 3dimensional.

numAtoms
()¶ Returns number of atoms.

numDOF
()¶ Returns number of degrees of freedom.

numModes
()¶ Returns number of modes in the instance (not necessarily maximum number of possible modes).

setEigens
(vectors, values=None)¶ Set eigen vectors and eigen values. If eigen values are omitted, they will be set to 1. Inverse eigenvalues are set as variances.

setHessian
(hessian)¶ Set Hessian matrix. A symmetric matrix is expected, i.e. not a lower or uppertriangular matrix.

setTitle
(title)¶ Set title of the model.
