22,437 research outputs found
Sequence organization of feline leukemis virus DNA in infected cells
A restriction site map has been deduced of unintegrated and integrated FeLV viral DNA found in human RD cells after experimental infection with the Gardner-Arnstein strain of FeLV. Restriction fragments were ordered by single and double enzyme digests followed by Southern transfer (1) and hybridization with 32P-labeled viral cDNA probes. The restriction map was oriented with respect to the 5' and 3' ends of viral RNA by using a 3' specific hybridization probe. The major form of unintegrated viral DNA found was a 8.7 kb linear DNA molecule bearing a 450 bp direct long terminal redundancy (LTR) derived from both 5' and 3' viral RNA sequences. Minor, circular forms, 8.7 kb and 8.2 kb in length were also detected, the larger one probably containing two adjacent copies of the LTR and the smaller one containing one copy of the LTR. Integrated copies of FeLV are colinear with the unintegrated linear form and contain the KpnI and SmaI sites found in each LTR
Sequence-specific double-strand cleavage of DNA by penta-N-methylpyrrolecarboxamide-EDTA·Fe(II)
In the presence of O2 and 5 mM dithiothreitol, penta-N-methylpyrrolecarboxamide-EDTA·Fe(II) [P5E·Fe(II)] at 0.5 µ M cleaves pBR322 plasmid DNA (50 µ M in base pairs) on opposite strands to afford discrete DNA fragments as analyzed by agarose gel electrophoresis. High-resolution denaturing gel electrophoresis of a 32P-end-labeled 517-base-pair restriction fragment containing a major cleavage site reveals that P5E·Fe(II) cleaves 3-5 base pairs contiguous to a 6-base-pair sequence, 5'-T-T-T-T-T-A-3' (4,323-4,328 base pairs). The major binding orientation of the pentapeptide occurs with the amino terminus at the adenine side of this sequence. In the presence of 5 mM dithiothreitol, 0.01 µ M P5E·Fe(II) converts form I pBR322 DNA at 0.22 µ M plasmid (1.0 mM in base pairs) to 40% form II, indicating the cleavage reaction is catalytic, turning over a minimum of nine times. This synthetic molecule achieves double-strand cleavage of DNA (pH 7.9, 25 degrees C) at the 6-base-pair recognition level and may provide an approach to the design of "artificial restriction enzymes.
Reconstruction of Integers from Pairwise Distances
Given a set of integers, one can easily construct the set of their pairwise
distances. We consider the inverse problem: given a set of pairwise distances,
find the integer set which realizes the pairwise distance set. This problem
arises in a lot of fields in engineering and applied physics, and has
confounded researchers for over 60 years. It is one of the few fundamental
problems that are neither known to be NP-hard nor solvable by polynomial-time
algorithms. Whether unique recovery is possible also remains an open question.
In many practical applications where this problem occurs, the integer set is
naturally sparse (i.e., the integers are sufficiently spaced), a property which
has not been explored. In this work, we exploit the sparse nature of the
integer set and develop a polynomial-time algorithm which provably recovers the
set of integers (up to linear shift and reversal) from the set of their
pairwise distances with arbitrarily high probability if the sparsity is
O(n^{1/2-\eps}). Numerical simulations verify the effectiveness of the
proposed algorithm.Comment: 14 pages, 4 figures, submitted to ICASSP 201
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Double-digest RADseq loci using standard Illumina indexes improve deep and shallow phylogenetic resolution of Lophodermium, a widespread fungal endophyte of pine needles.
The phylogenetic and population genetic structure of symbiotic microorganisms may correlate with important ecological traits that can be difficult to directly measure, such as host preferences or dispersal rates. This study develops and tests a low-cost double-digest restriction site-associated DNA sequencing (ddRADseq) protocol to reveal among- and within-species genetic structure for Lophodermium, a genus of fungal endophytes whose evolutionary analyses have been limited by the scarcity of informative markers. The protocol avoids expensive barcoded adapters and incorporates universal indexes for multiplexing. We tested for reproducibility and functionality by comparing shared loci from sample replicates and assessed the effects of numbers of ambiguous sites and clustering thresholds on coverage depths, number of shared loci among samples, and phylogenetic reconstruction. Errors between technical replicates were minimal. Relaxing the quality-filtering criteria increased the mean coverage depth per locus and the number of loci recovered within a sample, but had little effect on the number of shared loci across samples. Increasing clustering threshold decreased the mean coverage depth per cluster and increased the number of loci recovered within a sample but also decreased the number of shared loci across samples, especially among distantly related species. The combination of low similarity clustering (70%) and relaxed quality-filtering (allowing up to 30 ambiguous sites per read) performed the best in phylogenetic analyses at both recent and deep genetic divergences. Hence, this method generated sufficient number of shared homologous loci to investigate the evolutionary relationships among divergent fungal lineages with small haploid genomes. The greater genetic resolution also revealed new structure within species that correlated with ecological traits, providing valuable insights into their cryptic life histories
Phase Retrieval for Sparse Signals: Uniqueness Conditions
In a variety of fields, in particular those involving imaging and optics, we
often measure signals whose phase is missing or has been irremediably
distorted. Phase retrieval attempts the recovery of the phase information of a
signal from the magnitude of its Fourier transform to enable the reconstruction
of the original signal. A fundamental question then is: "Under which conditions
can we uniquely recover the signal of interest from its measured magnitudes?"
In this paper, we assume the measured signal to be sparse. This is a natural
assumption in many applications, such as X-ray crystallography, speckle imaging
and blind channel estimation. In this work, we derive a sufficient condition
for the uniqueness of the solution of the phase retrieval (PR) problem for both
discrete and continuous domains, and for one and multi-dimensional domains.
More precisely, we show that there is a strong connection between PR and the
turnpike problem, a classic combinatorial problem. We also prove that the
existence of collisions in the autocorrelation function of the signal may
preclude the uniqueness of the solution of PR. Then, assuming the absence of
collisions, we prove that the solution is almost surely unique on 1-dimensional
domains. Finally, we extend this result to multi-dimensional signals by solving
a set of 1-dimensional problems. We show that the solution of the
multi-dimensional problem is unique when the autocorrelation function has no
collisions, significantly improving upon a previously known result.Comment: submitted to IEEE TI
PLASMD BEARING A CDNA COPY OF THE GENOME OF BOVINE VIRAL DIARRHEA VIRUS, CHIMERIC DERIVATIVES THEREOF, AND METHOD OF PRODUCING AN INFECTIOUS BOVINE WRAL DARRHEAVIRUS USING SAD PLASMID
A plasmid bearing a cDNA copy of the genome of bovine viral diarrhea virus (BVDV), chimeric derivatives of the plasmid and a method of producing an infectious bovine viral diarrhea virus using the plasmid are disclosed. The invention relates to a plasmid DNA molecule that replicates easily in E. coli and contains a sufficient portion of the genome of BVDV, cloned as cDNA, to be a suitable template to produce RNA in vitro which, upon transfection into bovine cells, gives rise to infectious BVDV. The BVDV created by the process of the invention can be engineered for use as a vector in many advantageous applications
Local De Novo Assembly of RAD Paired-End Contigs Using Short Sequencing Reads
Despite the power of massively parallel sequencing platforms, a drawback is the
short length of the sequence reads produced. We demonstrate that short reads can
be locally assembled into longer contigs using
paired-end sequencing of
restriction-site associated
DNA (RAD-PE) fragments. We use this RAD-PE contig
approach to identify single
nucleotide polymorphisms (SNPs)
and determine haplotype structure in threespine stickleback and to sequence
E. coli and stickleback genomic DNA with overlapping
contigs of several hundred nucleotides. We also demonstrate that adding a
circularization step allows the local assembly of contigs up to 5 kilobases (kb)
in length. The ease of assembly and accuracy of the individual contigs produced
from each RAD site sequence suggests RAD-PE sequencing is a useful way to
convert genome-wide short reads into individually-assembled sequences hundreds
or thousands of nucleotides long
The application of artificial intelligence techniques to a sequencing problem in the biological domain
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