1 .TH g_hbond 1 "Mon 4 Apr 2011" "" "GROMACS suite, VERSION 4.5.4-dev-20110404-bc5695c"
3 g_hbond - computes and analyzes hydrogen bonds
5 .B VERSION 4.5.4-dev-20110404-bc5695c
9 .BI "\-s" " topol.tpr "
10 .BI "\-n" " index.ndx "
11 .BI "\-num" " hbnum.xvg "
12 .BI "\-g" " hbond.log "
13 .BI "\-ac" " hbac.xvg "
14 .BI "\-dist" " hbdist.xvg "
15 .BI "\-ang" " hbang.xvg "
16 .BI "\-hx" " hbhelix.xvg "
17 .BI "\-hbn" " hbond.ndx "
18 .BI "\-hbm" " hbmap.xpm "
19 .BI "\-don" " donor.xvg "
20 .BI "\-dan" " danum.xvg "
21 .BI "\-life" " hblife.xvg "
22 .BI "\-nhbdist" " nhbdist.xvg "
24 .BI "\-[no]version" ""
38 .BI "\-[no]contact" ""
39 .BI "\-shell" " real "
40 .BI "\-fitstart" " real "
41 .BI "\-fitstart" " real "
43 .BI "\-smooth" " real "
45 .BI "\-max_hb" " real "
47 .BI "\-geminate" " enum "
49 .BI "\-acflen" " int "
50 .BI "\-[no]normalize" ""
52 .BI "\-fitfn" " enum "
53 .BI "\-ncskip" " int "
54 .BI "\-beginfit" " real "
55 .BI "\-endfit" " real "
57 \&\fB g_hbond\fR computes and analyzes hydrogen bonds. Hydrogen bonds are
58 \&determined based on cutoffs for the angle Acceptor \- Donor \- Hydrogen
59 \&(zero is extended) and the distance Hydrogen \- Acceptor.
60 \&OH and NH groups are regarded as donors, O is an acceptor always,
61 \&N is an acceptor by default, but this can be switched using
62 \&\fB \-nitacc\fR. Dummy hydrogen atoms are assumed to be connected
63 \&to the first preceding non\-hydrogen atom.
66 \&You need to specify two groups for analysis, which must be either
67 \&identical or non\-overlapping. All hydrogen bonds between the two
68 \&groups are analyzed.
71 \&If you set \fB \-shell\fR, you will be asked for an additional index group
72 \&which should contain exactly one atom. In this case, only hydrogen
73 \&bonds between atoms within the shell distance from the one atom are
88 \&Note that the triplets need not be on separate lines.
89 \&Each atom triplet specifies a hydrogen bond to be analyzed,
90 \¬e also that no check is made for the types of atoms.
95 \&\fB \-num\fR: number of hydrogen bonds as a function of time.
97 \&\fB \-ac\fR: average over all autocorrelations of the existence
98 \&functions (either 0 or 1) of all hydrogen bonds.
100 \&\fB \-dist\fR: distance distribution of all hydrogen bonds.
102 \&\fB \-ang\fR: angle distribution of all hydrogen bonds.
104 \&\fB \-hx\fR: the number of n\-n+i hydrogen bonds as a function of time
105 \&where n and n+i stand for residue numbers and i ranges from 0 to 6.
106 \&This includes the n\-n+3, n\-n+4 and n\-n+5 hydrogen bonds associated
107 \&with helices in proteins.
109 \&\fB \-hbn\fR: all selected groups, donors, hydrogens and acceptors
110 \&for selected groups, all hydrogen bonded atoms from all groups and
111 \&all solvent atoms involved in insertion.
113 \&\fB \-hbm\fR: existence matrix for all hydrogen bonds over all
114 \&frames, this also contains information on solvent insertion
115 \&into hydrogen bonds. Ordering is identical to that in \fB \-hbn\fR
118 \&\fB \-dan\fR: write out the number of donors and acceptors analyzed for
119 \&each timeframe. This is especially useful when using \fB \-shell\fR.
121 \&\fB \-nhbdist\fR: compute the number of HBonds per hydrogen in order to
122 \&compare results to Raman Spectroscopy.
126 \&Note: options \fB \-ac\fR, \fB \-life\fR, \fB \-hbn\fR and \fB \-hbm\fR
127 \&require an amount of memory proportional to the total numbers of donors
128 \× the total number of acceptors in the selected group(s).
130 .BI "\-f" " traj.xtc"
132 Trajectory: xtc trr trj gro g96 pdb cpt
134 .BI "\-s" " topol.tpr"
136 Run input file: tpr tpb tpa
138 .BI "\-n" " index.ndx"
142 .BI "\-num" " hbnum.xvg"
146 .BI "\-g" " hbond.log"
150 .BI "\-ac" " hbac.xvg"
154 .BI "\-dist" " hbdist.xvg"
158 .BI "\-ang" " hbang.xvg"
162 .BI "\-hx" " hbhelix.xvg"
166 .BI "\-hbn" " hbond.ndx"
170 .BI "\-hbm" " hbmap.xpm"
172 X PixMap compatible matrix file
174 .BI "\-don" " donor.xvg"
178 .BI "\-dan" " danum.xvg"
182 .BI "\-life" " hblife.xvg"
186 .BI "\-nhbdist" " nhbdist.xvg"
192 Print help info and quit
194 .BI "\-[no]version" "no "
195 Print version info and quit
197 .BI "\-nice" " int" " 19"
200 .BI "\-b" " time" " 0 "
201 First frame (ps) to read from trajectory
203 .BI "\-e" " time" " 0 "
204 Last frame (ps) to read from trajectory
206 .BI "\-dt" " time" " 0 "
207 Only use frame when t MOD dt = first time (ps)
209 .BI "\-tu" " enum" " ps"
210 Time unit: \fB fs\fR, \fB ps\fR, \fB ns\fR, \fB us\fR, \fB ms\fR or \fB s\fR
212 .BI "\-xvg" " enum" " xmgrace"
213 xvg plot formatting: \fB xmgrace\fR, \fB xmgr\fR or \fB none\fR
215 .BI "\-a" " real" " 30 "
216 Cutoff angle (degrees, Acceptor \- Donor \- Hydrogen)
218 .BI "\-r" " real" " 0.35 "
219 Cutoff radius (nm, X \- Acceptor, see next option)
221 .BI "\-[no]da" "yes "
222 Use distance Donor\-Acceptor (if TRUE) or Hydrogen\-Acceptor (FALSE)
224 .BI "\-r2" " real" " 0 "
225 Second cutoff radius. Mainly useful with \fB \-contact\fR and \fB \-ac\fR
227 .BI "\-abin" " real" " 1 "
228 Binwidth angle distribution (degrees)
230 .BI "\-rbin" " real" " 0.005 "
231 Binwidth distance distribution (nm)
233 .BI "\-[no]nitacc" "yes "
234 Regard nitrogen atoms as acceptors
236 .BI "\-[no]contact" "no "
237 Do not look for hydrogen bonds, but merely for contacts within the cut\-off distance
239 .BI "\-shell" " real" " \-1 "
240 when 0, only calculate hydrogen bonds within nm shell around one particle
242 .BI "\-fitstart" " real" " 1 "
243 Time (ps) from which to start fitting the correlation functions in order to obtain the forward and backward rate constants for HB breaking and formation. With \fB \-gemfit\fR we suggest \fB \-fitstart 0\fR
245 .BI "\-fitstart" " real" " 1 "
246 Time (ps) to which to stop fitting the correlation functions in order to obtain the forward and backward rate constants for HB breaking and formation (only with \fB \-gemfit\fR)
248 .BI "\-temp" " real" " 298.15"
249 Temperature (K) for computing the Gibbs energy corresponding to HB breaking and reforming
251 .BI "\-smooth" " real" " \-1 "
252 If = 0, the tail of the ACF will be smoothed by fitting it to an exponential function: y = A exp(\-x/tau)
254 .BI "\-dump" " int" " 0"
255 Dump the first N hydrogen bond ACFs in a single \fB .xvg\fR file for debugging
257 .BI "\-max_hb" " real" " 0 "
258 Theoretical maximum number of hydrogen bonds used for normalizing HB autocorrelation function. Can be useful in case the program estimates it wrongly
260 .BI "\-[no]merge" "yes "
261 H\-bonds between the same donor and acceptor, but with different hydrogen are treated as a single H\-bond. Mainly important for the ACF.
263 .BI "\-geminate" " enum" " none"
264 Use reversible geminate recombination for the kinetics/thermodynamics calclations. See Markovitch et al., J. Chem. Phys 129, 084505 (2008) for details.: \fB none\fR, \fB dd\fR, \fB ad\fR, \fB aa\fR or \fB a4\fR
266 .BI "\-diff" " real" " \-1 "
267 Dffusion coefficient to use in the reversible geminate recombination kinetic model. If negative, then it will be fitted to the ACF along with ka and kd.
269 .BI "\-acflen" " int" " \-1"
270 Length of the ACF, default is half the number of frames
272 .BI "\-[no]normalize" "yes "
275 .BI "\-P" " enum" " 0"
276 Order of Legendre polynomial for ACF (0 indicates none): \fB 0\fR, \fB 1\fR, \fB 2\fR or \fB 3\fR
278 .BI "\-fitfn" " enum" " none"
279 Fit function: \fB none\fR, \fB exp\fR, \fB aexp\fR, \fB exp_exp\fR, \fB vac\fR, \fB exp5\fR, \fB exp7\fR, \fB exp9\fR or \fB erffit\fR
281 .BI "\-ncskip" " int" " 0"
282 Skip N points in the output file of correlation functions
284 .BI "\-beginfit" " real" " 0 "
285 Time where to begin the exponential fit of the correlation function
287 .BI "\-endfit" " real" " \-1 "
288 Time where to end the exponential fit of the correlation function, \-1 is until the end
291 \- The option \fB \-sel\fR that used to work on selected hbonds is out of order, and therefore not available for the time being.
296 More information about \fBGROMACS\fR is available at <\fIhttp://www.gromacs.org/\fR>.