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Schirmer, Stefanie: Comparing forests. 2011
Inhalt
Introduction
Motivation: the RNA structure alignment problem
Introduction: RNA, a molecular contortionist
Overview of this work
Foundations and Definitions
Basic Definitions
Sequences
Graphs
Trees
Forests
Structure levels of RNA
The primary structure
RNA secondary structure
The tertiary structure
RNA secondary structure representations
Basepair representation
Vienna dot-bracket representation
Tree representation
Mountain representation
Dome representation
Circle representation
Graph representation
Other representations
Discussion
Distance measures for structure comparison
Metrics
Methods for RNA structure comparison
Basepair distances
Naive base pair metric
Hausdorff distance
Prohorov metric
Mountain metric
Discussion of the basepair metrics
Encoding as a string and alignment
Konings and Hogeweg - string encoding from mountain representation
Shapiros encoding - string encoding from coarse grained tree representation
Tree representation distance - from tree to string by counting children
Discussion of string encoding methods
Sequences with structure information, arc annotated sequences
Evans/LAPCS problem
Zhang's model
Jiang's model - A general edit distance between RNA structures
Alignment hierarchy / Alignments of RNA structures
Discussion of Arc annotated sequence methods
SCFGS/HMMs
Stochastic context-free grammars for tRNA modeling
Small subunit ribosomal RNA modeling using stochastic context-free grammars
Tree and forest comparison
Tree edit distances
Tree alignment distances
Tree edit and tree alignment
Discussion of the tree and forest comparison models
Distances between graphs
Multiple layer secondary structure comparison
A graph theoretical approach to predict common RNA secondary structure motifs including pseudoknots of unaligned sequences
Discussion of graph based methods
Strengths, weaknesses and artefacts
The forest alignment model
RNA secondary structures as forests
From tree to forest
Representing base pair information
The forest alignment
The forest alignment
Defining a forest alignment
Scoring the alignment
Computing the forest alignment
The search space of alignments for general forests
Recurrences for search space construction
Scoring
Global alignment of general forests
Defining the ranges of recursive computation: Relevant Closed Subforests
Stepping down in the recursion: Aligning a pair of CSFs
Sketching a control structure
Tabulation
Index mapping
Calculation order
Dynamic programming algorithm for global forest alignment
Global alignment of RNA forests
Dynamic programming algorithm for global alignment of RNA forests
Local alignment of general forests
Relevant CSFs for local alignment
Dynamic Programming algorithm for local alignment of general forests
Local alignment of RNA forests
Local suboptimal solutions
Small in large alignment of forests
Discussion: Role of relevant CSF pairs; edit operations for RNA
Pairwise vs. multiple forest alignment
Time and space complexity
Gaps and affine gap cost alignment
Motivation and model
The scattered alignment problem
Gaps
Gaps in sequences
Gaps in forests
Affine gap costs on sequences
Affine gap costs on forests
The search space of forest alignments with affine gap cost model
Recursive enumeration of the search space of forest alignments with affine gap costs
Tabulation
Scoring
Relevant CSF Pairs
Aligning two CSFs
CSFs of general forests
CSFs of RNA forests
Prototyping in Haskell
Developing a dynamic programming algorithm
Global forest alignment with affine gap costs
Global forest alignment of RNA with affine gap costs
Local forest alignment with affine gap costs
Multiple forest alignment with affine gap costs
Time and space complexity
Anchoring by shape abstraction
Motivation - shape anchoring
Shape abstraction
Acquiring anchors for the input forest
The anchoring
The anchored forest alignment problem
Restricted recurrences for computing alignments with a given anchoring
Time and space complexity
Discussion
Top down and bottom up alignment
Case correction for pair nodes
Constructing well-formed RNA forest alignments
The recursive subproblems of the edit operations
The recursive subproblems of the general forest edit operations
The recursive subproblems of the RNA forest alignment
The recursive subproblems of the pair replacement operation
The recursive subproblems of the pair deletion operations
The recursive subproblems of the pair insertion operations
A new well-formed RNA forest alignment algorithm
Discussion and Complexity
Updated recurrences for aligning RNA forests
Updated abstract recurrences and adjustment of the scoring functions
Discussion of the new P-node edit operations
RNAforester 2.0
Implementation
Options and command line parameters
Applications
Algorithms for RNA 2D structure prediction
Problem: from a family of sequences to a structural consensus
Plan ACstar: Improving structural alignments in the twilight zone
Results and discussion
RNAforecast as an alternative to the Sankoff algorithm
Performance of RNAforecast with RNAforester 2.0
Program evaluation
Solving the scattered alignment problem with hand tuned scores
General measurements - on Rfam
Consistency checks
Speedup measurements
Score decline with the anchoring
Benefits regarding the biological model
Conclusion