PRE
 This is part of the isdb module

Calculates the Paramagnetic Resonance Enhancement intensity ratio between a spin label atom and a list of atoms .

The reference atom for the spin label is added with SPINLABEL, the affected atom(s) are give as numbered GROUPA1, GROUPA2, ... The additional parameters needed for the calculation are given as INEPT, the inept time, TAUC the correlation time, OMEGA, the Larmor frequency and RTWO for the relaxation time.

METAINFERENCE can be activated using DOSCORE and the other relevant keywords.

Description of components

By default this Action calculates the following quantities. These quantities can be referenced elsewhere in the input by using this Action's label followed by a dot and the name of the quantity required from the list below.

 Quantity Description score the Metainference score sigma uncertainty parameter sigmaMean uncertainty in the mean estimate acceptSigma MC acceptance for sigma values pre the # PRE

In addition the following quantities can be calculated by employing the keywords listed below

 Quantity Keyword Description acceptScale SCALEDATA MC acceptance for scale value acceptFT GENERIC MC acceptance for general metainference f tilde value weight REWEIGHT weights of the weighted average biasDer REWEIGHT derivatives with respect to the bias scale SCALEDATA scale parameter offset ADDOFFSET offset parameter ftilde GENERIC ensemble average estimator exp PREINT the # PRE experimental intensity
The atoms involved can be specified using
 SPINLABEL The atom to be used as the paramagnetic center.. For more information on how to specify lists of atoms see Groups and Virtual Atoms GROUPA the atoms involved in each of the contacts you wish to calculate. Keywords like GROUPA1, GROUPA2, GROUPA3,... should be listed and one contact will be calculated for each ATOM keyword you specify. You can use multiple instances of this keyword i.e. GROUPA1, GROUPA2, GROUPA3...
Compulsory keywords
 NOISETYPE ( default=MGAUSS ) functional form of the noise (GAUSS,MGAUSS,OUTLIERS,MOUTLIERS,GENERIC) LIKELIHOOD ( default=GAUSS ) the likelihood for the GENERIC metainference model, GAUSS or LOGN DFTILDE ( default=0.1 ) fraction of sigma_mean used to evolve ftilde SCALE0 ( default=1.0 ) initial value of the scaling factor SCALE_PRIOR ( default=FLAT ) either FLAT or GAUSSIAN OFFSET0 ( default=0.0 ) initial value of the offset OFFSET_PRIOR ( default=FLAT ) either FLAT or GAUSSIAN SIGMA0 ( default=1.0 ) initial value of the uncertainty parameter SIGMA_MIN ( default=0.0 ) minimum value of the uncertainty parameter SIGMA_MAX ( default=10. ) maximum value of the uncertainty parameter OPTSIGMAMEAN ( default=NONE ) Set to NONE/SEM to manually set sigma mean, or to estimate it on the fly WRITE_STRIDE ( default=10000 ) write the status to a file every N steps, this can be used for restart/continuation INEPT is the INEPT time (in ms). TAUC is the correlation time (in ns) for this electron-nuclear interaction. OMEGA is the Larmor frequency of the nuclear spin (in MHz).
Options
 NUMERICAL_DERIVATIVES ( default=off ) calculate the derivatives for these quantities numerically DOSCORE ( default=off ) activate metainference NOENSEMBLE ( default=off ) don't perform any replica-averaging REWEIGHT ( default=off ) simple REWEIGHT using the ARG as energy SCALEDATA ( default=off ) Set to TRUE if you want to sample a scaling factor common to all values and replicas ADDOFFSET ( default=off ) Set to TRUE if you want to sample an offset common to all values and replicas NOPBC ( default=off ) ignore the periodic boundary conditions when calculating distances NORATIO ( default=off ) Set to TRUE if you want to compute PRE without Intensity Ratio ARG the input for this action is the scalar output from one or more other actions. The particular scalars that you will use are referenced using the label of the action. If the label appears on its own then it is assumed that the Action calculates a single scalar value. The value of this scalar is thus used as the input to this new action. If * or *.* appears the scalars calculated by all the proceeding actions in the input file are taken. Some actions have multi-component outputs and each component of the output has a specific label. For example a DISTANCE action labelled dist may have three components x, y and z. To take just the x component you should use dist.x, if you wish to take all three components then use dist.*.More information on the referencing of Actions can be found in the section of the manual on the PLUMED Getting Started. Scalar values can also be referenced using POSIX regular expressions as detailed in the section on Regular Expressions. To use this feature you you must compile PLUMED with the appropriate flag. You can use multiple instances of this keyword i.e. ARG1, ARG2, ARG3... AVERAGING Stride for calculation of averaged weights and sigma_mean SCALE_MIN minimum value of the scaling factor SCALE_MAX maximum value of the scaling factor DSCALE maximum MC move of the scaling factor OFFSET_MIN minimum value of the offset OFFSET_MAX maximum value of the offset DOFFSET maximum MC move of the offset REGRES_ZERO stride for regression with zero offset DSIGMA maximum MC move of the uncertainty parameter SIGMA_MEAN0 starting value for the uncertainty in the mean estimate TEMP the system temperature - this is only needed if code doesn't pass the temperature to plumed MC_STEPS number of MC steps MC_CHUNKSIZE MC chunksize STATUS_FILE write a file with all the data useful for restart/continuation of Metainference SELECTOR name of selector NSELECT range of values for selector [0, N-1] RESTART allows per-action setting of restart (YES/NO/AUTO) RTWO The relaxation of the atom/atoms in the corresponding GROUPA of atoms. Keywords like RTWO1, RTWO2, RTWO3,... should be listed. You can use multiple instances of this keyword i.e. RTWO1, RTWO2, RTWO3... PREINT Add an experimental value for each PRE. You can use multiple instances of this keyword i.e. PREINT1, PREINT2, PREINT3...
Examples

In the following example five PRE intensities are calculated using the distance between the oxygen of the spin label and the backbone hydrogen atoms. Omega is the NMR frequency, RTWO the R2 for the hydrogen atoms, INEPT of 8 ms for the experiment and a TAUC of 1.21 ns

PRE ...
LABEL=HN_pre
INEPT=8
TAUC=1.21
OMEGA=900
SPINLABEL=1818
GROUPA1=86  RTWO1=0.0120272827
GROUPA2=177 RTWO2=0.0263953158
GROUPA3=285 RTWO3=0.0058899829
GROUPA4=335 RTWO4=0.0102072646
GROUPA5=451 RTWO5=0.0086341843
... PRE

PRINT ARG=HN_pre.* FILE=PRE.dat STRIDE=1