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RNALfold − manual page for RNALfold 2.4.11




RNALfold 2.4.11

calculate locally stable secondary structures of RNAs

Compute locally stable RNA secondary structure with a maximal base pair span. For a sequence of length n and a base pair span of L the algorithm uses only O(n+L*L) memory and O(n*L*L) CPU time. Thus it is practical to "scan" very large genomes for short RNA structures. Output consists of a list of secondary structure components of size <= L, one entry per line. Each output line contains the predicted local structure its energy in kcal/mol and the starting position of the local structure.
, −−help

Print help and exit


Print help, including all details and hidden options, and exit


Print help, including hidden options, and exit

−V, −−version

Print version and exit

General Options:

Below are command line options which alter the general behavior of this program

−v, −−verbose

Be verbose


−L, −−span=INT

Set the maximum allowed separation of a base pair to span. I.e. no pairs (i,j) with j−i>span will be allowed.



Do not automatically substitude nucleotide "T" with "U"


−o, −−outfile[=<filename>]

Print output to file instead of stdout

This option may be used to write all output to output files rather than printing to stdout. The default filename is "RNALfold_output.lfold" if no FASTA header precedes the input sequences and the −−auto−id feature is inactive. Otherwise, output files with the scheme "prefix.lfold" are generated, where the "prefix" is taken from the sequence id. The user may specify a single output file name for all data generated from the input by supplying an optional string as argument to this parameter. In case a file with the same filename already exists, any output of the program will be appended to it. Note: Any special characters in the filename will be replaced by the filename delimiter, hence there is no way to pass an entire directory path through this option yet. (See also the "−−filename−delim" parameter)

−i, −−infile=<filename>

Read a file instead of reading from stdin

The default behavior of RNALfold is to read input from stdin. Using this parameter the user can specify an input file name where data is read from.


Automatically generate an ID for each sequence. (default=off)

The default mode of RNALfold is to automatically determine an ID from the input sequence data if the input file format allows to do that. Sequence IDs are usually given in the FASTA header of input sequences. If this flag is active, RNALfold ignores any IDs retrieved from the input and automatically generates an ID for each sequence. This ID consists of a prefix and an increasing number. This flag can also be used to add a FASTA header to the output even if the input has none.


Prefix for automatically generated IDs (as used in output file names)


If this parameter is set, each sequence will be prefixed with the provided string. Hence, the output files will obey the following naming scheme: "prefix_xxxx.lfold" where xxxx is the sequence number. Note: Setting this parameter implies −−auto−id.


Change the delimiter between prefix and increasing number for automatically generated IDs (as used in output file names)


This parameter can be used to change the default delimiter "_" between

the prefix string and the increasing number for automatically generated ID.


Specify the number of digits of the counter in automatically generated alignment IDs.


When alignments IDs are automatically generated, they receive an increasing number, starting with 1. This number will always be left−padded by leading zeros, such that the number takes up a certain width. Using this parameter, the width can be specified to the users need. We allow numbers in the range [1:18]. This option implies −−auto−id.


Specify the first number in automatically generated alignment IDs.


When sequence IDs are automatically generated, they receive an increasing number, usually starting with 1. Using this parameter, the first number can be specified to the users requirements. Note: negative numbers are not allowed. Note: Setting this parameter implies to ignore any IDs retrieved from the input data, i.e. it activates the −−auto−id flag.


Change the delimiting character that is used

for sanitized filenames


This parameter can be used to change the delimiting character used while sanitizing filenames, i.e. replacing invalid characters. Note, that the default delimiter ALWAYS is the first character of the "ID delimiter" as supplied through the −−id−delim option. If the delimiter is a whitespace character or empty, invalid characters will be simply removed rather than substituted. Currently, we regard the following characters as illegal for use in filenames: backslash ’\’, slash ’/’, question mark ’?’, percent sign ’%’, asterisk ’*’, colon ’:’, pipe symbol ’|’, double quote ’"’, triangular brackets ’<’ and ’>’.


Use full FASTA header to create filenames


This parameter can be used to deactivate the default behavior of limiting output filenames to the first word of the sequence ID. Consider the following example: An input with FASTA header ">NM_0001 Homo Sapiens some gene" usually produces output files with the prefix "NM_0001" without the additional data available in the FASTA header, e.g. "NM_0001.lfold". With this flag set, no truncation of the output filenames is performed, i.e. output filenames receive the full FASTA header data as prefixes. Note, however, that invalid characters (such as whitespace) will be substituted by a delimiting character or simply removed, (see also the parameter option −−filename−delim).


Read additional commands from file

Commands include hard and soft constraints, but also structure motifs in hairpin and interior loops that need to be treeted differently. Furthermore, commands can be set for unstructured and structured domains.


Use SHAPE reactivity data in the folding recursions (does not work for Zuker suboptimals and stochastic backtracking yet)

−−shapeMethod=[D/Z/W] + [optional parameters]

Specify the method how to convert SHAPE

reactivity data to pseudo energy



The following methods can be used to convert SHAPE reactivities into pseudo energy contributions.

’D’: Convert by using a linear equation according to Deigan et al 2009. The calculated pseudo energies will be applied for every nucleotide involved in a stacked pair. This method is recognized by a capital ’D’ in the provided parameter, i.e.: −−shapeMethod="D" is the default setting. The slope ’m’ and the intercept ’b’ can be set to a non−default value if necessary, otherwise m=1.8 and b=−0.6. To alter these parameters, e.g. m=1.9 and b=−0.7, use a parameter string like this: −−shapeMethod="Dm1.9b−0.7". You may also provide only one of the two parameters like: −−shapeMethod="Dm1.9" or −−shapeMethod="Db−0.7".

’Z’: Convert SHAPE reactivities to pseudo energies according to Zarringhalam et al 2012. SHAPE reactivities will be converted to pairing probabilities by using linear mapping. Aberration from the observed pairing probabilities will be penalized during the folding recursion. The magnitude of the penalties can affected by adjusting the factor beta (e.g. −−shapeMethod="Zb0.8").

’W’: Apply a given vector of perturbation energies to unpaired nucleotides according to Washietl et al 2012. Perturbation vectors can be calculated by using RNApvmin.


+ [optional parameters] Specify the method used to convert SHAPE

reactivities to pairing probabilities when

using the SHAPE approach of Zarringhalam et al.


The following methods can be used to convert SHAPE reactivities into the probability for a certain nucleotide to be unpaired.

’M’: Use linear mapping according to Zarringhalam et al. ’C’: Use a cutoff−approach to divide into paired and unpaired nucleotides (e.g. "C0.25") ’S’: Skip the normalizing step since the input data already represents probabilities for being unpaired rather than raw reactivity values ’L’: Use a linear model to convert the reactivity into a probability for being unpaired (e.g. "Ls0.68i0.2" to use a slope of 0.68 and an intercept of 0.2) ’O’: Use a linear model to convert the log of the reactivity into a probability for being unpaired (e.g. "Os1.6i−2.29" to use a slope of 1.6 and an intercept of −2.29)


Select additional algorithms which should be included in the calculations. The Minimum free energy (MFE) and a structure representative are calculated in any case.

−z, −−zscore[=DOUBLE]

Activate z−score computation. An optional argument may be supplied to set the threshold Due to parsing the commandline parameters a negative value should be given immediately after "z" without spaces e.g. −z−4.9


−g, −−gquad

Incoorporate G−Quadruplex formation into the structure prediction algorithm


Model Details:
, −−temp=DOUBLE

Rescale energy parameters to a temperature of temp C. Default is 37C.

−4, −−noTetra

Do not include special tabulated stabilizing energies for tri−, tetra− and hexaloop hairpins. Mostly for testing.


−d, −−dangles=INT

How to treat "dangling end" energies for bases adjacent to helices in free ends and multi−loops


With −d1 only unpaired bases can participate in at most one dangling end. With −d2 this check is ignored, dangling energies will be added for the bases adjacent to a helix on both sides in any case; this is the default for mfe and partition function folding (−p). The option −d0 ignores dangling ends altogether (mostly for debugging). With −d3 mfe folding will allow coaxial stacking of adjacent helices in multi−loops. At the moment the implementation will not allow coaxial stacking of the two interior pairs in a loop of degree 3 and works only for mfe folding.

Note that with −d1 and −d3 only the MFE computations will be using this setting while partition function uses −d2 setting, i.e. dangling ends will be treated differently.


Produce structures without lonely pairs (helices of length 1).


For partition function folding this only disallows pairs that can only occur isolated. Other pairs may still occasionally occur as helices of length 1.


Do not allow GU pairs



Do not allow GU pairs at the end of helices


−P, −−paramFile=paramfile

Read energy parameters from paramfile, instead of using the default parameter set.

A sample parameter file should accompany your distribution. See the RNAlib documentation for details on the file format.


Allow other pairs in addition to the usual AU,GC,and GU pairs.

Its argument is a comma separated list of additionally allowed pairs. If the first character is a "−" then AB will imply that AB and BA are allowed pairs. e.g. RNALfold −nsp −GA will allow GA and AG pairs. Nonstandard pairs are given 0 stacking energy.

−e, −−energyModel=INT

Rarely used option to fold sequences from the artificial ABCD... alphabet, where A pairs B, C−D etc. Use the energy parameters for GC (−e 1) or AU (−e 2) pairs.


If you use this program in your work you might want to cite:

R. Lorenz, S.H. Bernhart, C. Hoener zu Siederdissen, H. Tafer, C. Flamm, P.F. Stadler and I.L. Hofacker (2011), "ViennaRNA Package 2.0", Algorithms for Molecular Biology: 6:26

I.L. Hofacker, W. Fontana, P.F. Stadler, S. Bonhoeffer, M. Tacker, P. Schuster (1994), "Fast Folding and Comparison of RNA Secondary Structures", Monatshefte f. Chemie: 125, pp 167-188

R. Lorenz, I.L. Hofacker, P.F. Stadler (2016), "RNA folding with hard and soft constraints", Algorithms for Molecular Biology 11:1 pp 1-13

I.L. Hofacker, B. Priwitzer, and P.F. Stadler (2004), "Prediction of Locally Stable RNA Secondary Structures for Genome-Wide Surveys", Bioinformatics: 20, pp 186-190

The energy parameters are taken from:

D.H. Mathews, M.D. Disney, D. Matthew, J.L. Childs, S.J. Schroeder, J. Susan, M. Zuker, D.H. Turner (2004), "Incorporating chemical modification constraints into a dynamic programming algorithm for prediction of RNA secondary structure", Proc. Natl. Acad. Sci. USA: 101, pp 7287-7292

D.H Turner, D.H. Mathews (2009), "NNDB: The nearest neighbor parameter database for predicting stability of nucleic acid secondary structure", Nucleic Acids Research: 38, pp 280-282


Ivo L Hofacker, Peter F Stadler, Ronny Lorenz


If in doubt our program is right, nature is at fault. Comments should be sent to


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