Predicting Consensus Structures from Alignment(s)

compute various properties (consensus MFE structures, partition function, Boltzmann distributed stochastic samples, ...) for RNA sequence alignments More...

Collaboration diagram for Predicting Consensus Structures from Alignment(s):

Modules
	MFE Consensus Structures for Sequence Alignment(s)
	Partition Function and Base Pair Probabilities for Sequence Alignment(s)
	Stochastic Backtracking of Consensus Structures from Sequence Alignment(s)
	Local MFE consensus structures for Sequence Alignments

Files
file	alifold.h
	compute various properties (consensus MFE structures, partition function, Boltzmann distributed stochastic samples, ...) for RNA sequence alignments

Functions
int	get_mpi (char *Alseq[], int n_seq, int length, int *mini)
	Get the mean pairwise identity in steps from ?to?(ident) More...
float **	readribosum (char *name)
	Read a ribosum or other user-defined scoring matrix.
float	energy_of_alistruct (const char **sequences, const char *structure, int n_seq, float *energy)
	Calculate the free energy of a consensus structure given a set of aligned sequences. More...
void	encode_ali_sequence (const char *sequence, short *S, short *s5, short *s3, char *ss, unsigned short *as, int circ)
	Get arrays with encoded sequence of the alignment. More...
void	alloc_sequence_arrays (const char **sequences, short ***S, short ***S5, short ***S3, unsigned short ***a2s, char ***Ss, int circ)
	Allocate memory for sequence array used to deal with aligned sequences. More...
void	free_sequence_arrays (unsigned int n_seq, short ***S, short ***S5, short ***S3, unsigned short ***a2s, char ***Ss)
	Free the memory of the sequence arrays used to deal with aligned sequences. More...
int	get_alipf_arrays (short ***S_p, short ***S5_p, short ***S3_p, unsigned short ***a2s_p, char ***Ss_p, double **qb_p, double **qm_p, double **q1k_p, double **qln_p, short **pscore)
	Get pointers to (almost) all relavant arrays used in alifold's partition function computation. More...

Variables
double	cv_fact
	This variable controls the weight of the covariance term in the energy function of alignment folding algorithms. More...
double	nc_fact
	This variable controls the magnitude of the penalty for non-compatible sequences in the covariance term of alignment folding algorithms. More...

Detailed Description

compute various properties (consensus MFE structures, partition function, Boltzmann distributed stochastic samples, ...) for RNA sequence alignments

Consensus structures can be predicted by a modified version of the fold() algorithm that takes a set of aligned sequences instead of a single sequence. The energy function consists of the mean energy averaged over the sequences, plus a covariance term that favors pairs with consistent and compensatory mutations and penalizes pairs that cannot be formed by all structures. For details see[6] and [2].

Function Documentation

int get_mpi	(	char *	Alseq[],
		int	n_seq,
		int	length,
		int *	mini
	)

Get the mean pairwise identity in steps from ?to?(ident)

Parameters

Alseq
n_seq	The number of sequences in the alignment
length	The length of the alignment
mini

Returns

The mean pairwise identity

float energy_of_alistruct	(	const char **	sequences,
		const char *	structure,
		int	n_seq,
		float *	energy
	)

Calculate the free energy of a consensus structure given a set of aligned sequences.

Parameters

sequences	The NULL terminated array of sequences
structure	The consensus structure
n_seq	The number of sequences in the alignment
energy	A pointer to an array of at least two floats that will hold the free energies (energy[0] will contain the free energy, energy[1] will be filled with the covariance energy term)

Returns

free energy in kcal/mol

void encode_ali_sequence	(	const char *	sequence,
		short *	S,
		short *	s5,
		short *	s3,
		char *	ss,
		unsigned short *	as,
		int	circ
	)

Get arrays with encoded sequence of the alignment.

this function assumes that in S, S5, s3, ss and as enough space is already allocated (size must be at least sequence length+2)

Parameters

sequence	The gapped sequence from the alignment
S	pointer to an array that holds encoded sequence
s5	pointer to an array that holds the next base 5' of alignment position i
s3	pointer to an array that holds the next base 3' of alignment position i
ss
as
circ	assume the molecules to be circular instead of linear (circ=0)

void alloc_sequence_arrays	(	const char **	sequences,
		short ***	S,
		short ***	S5,
		short ***	S3,
		unsigned short ***	a2s,
		char ***	Ss,
		int	circ
	)

Allocate memory for sequence array used to deal with aligned sequences.

Note that these arrays will also be initialized according to the sequence alignment given

See Also

free_sequence_arrays()

Parameters

sequences	The aligned sequences
S	A pointer to the array of encoded sequences
S5	A pointer to the array that contains the next 5' nucleotide of a sequence position
S3	A pointer to the array that contains the next 3' nucleotide of a sequence position
a2s	A pointer to the array that contains the alignment to sequence position mapping
Ss	A pointer to the array that contains the ungapped sequence
circ	assume the molecules to be circular instead of linear (circ=0)

void free_sequence_arrays	(	unsigned int	n_seq,
		short ***	S,
		short ***	S5,
		short ***	S3,
		unsigned short ***	a2s,
		char ***	Ss
	)

Free the memory of the sequence arrays used to deal with aligned sequences.

This function frees the memory previously allocated with alloc_sequence_arrays()

See Also

alloc_sequence_arrays()

Parameters

n_seq	The number of aligned sequences
S	A pointer to the array of encoded sequences
S5	A pointer to the array that contains the next 5' nucleotide of a sequence position
S3	A pointer to the array that contains the next 3' nucleotide of a sequence position
a2s	A pointer to the array that contains the alignment to sequence position mapping
Ss	A pointer to the array that contains the ungapped sequence

int get_alipf_arrays	(	short ***	S_p,
		short ***	S5_p,
		short ***	S3_p,
		unsigned short ***	a2s_p,
		char ***	Ss_p,
		double **	qb_p,
		double **	qm_p,
		double **	q1k_p,
		double **	qln_p,
		short **	pscore
	)

Get pointers to (almost) all relavant arrays used in alifold's partition function computation.

Note

To obtain meaningful pointers, call alipf_fold first!

See Also

pf_alifold(), alipf_circ_fold()

Parameters

S_p	A pointer to the 'S' array (integer representation of nucleotides)
S5_p	A pointer to the 'S5' array
S3_p	A pointer to the 'S3' array
a2s_p	A pointer to the pair type matrix
Ss_p	A pointer to the 'Ss' array
qb_p	A pointer to the QB matrix
qm_p	A pointer to the QM matrix
q1k_p	A pointer to the 5' slice of the Q matrix ( )
qln_p	A pointer to the 3' slice of the Q matrix ( )

Returns

Non Zero if everything went fine, 0 otherwise

Variable Documentation

double cv_fact

This variable controls the weight of the covariance term in the energy function of alignment folding algorithms.

Default is 1.

double nc_fact

This variable controls the magnitude of the penalty for non-compatible sequences in the covariance term of alignment folding algorithms.

Default is 1.