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Transformation Frequency (transformation + frequency)

Distribution by Scientific Domains
Life Sciences50%

Selected Abstracts

Germ line transformation of the yellow fever mosquito, Aedes aegypti, mediated by transpositional insertion of a piggyBac vector

INSECT MOLECULAR BIOLOGY, Issue 2 2002
N. F. Lobo
Mosquito-vectored diseases such as yellow fever and dengue fever continue to have a substantial impact on human populations world-wide. Novel strategies for control of these mosquito vectored diseases can arise through the development of reliable systems for genetic manipulation of the insect vector. A piggyBac vector marked with the Drosophila melanogaster cinnabar (cn) gene was used to transform the white-eyed khw strain of Aedes aegypti. Microinjection of preblastoderm embryos resulted in four families of cinnabar transformed insects. An overall transformation frequency of 4%, with a range of 0% to as high as 13% for individual experiments, was achieved when using a heat-shock induced transposase providing helper plasmid. Southern hybridizations indicated multiple insertion events in three of four transgenic lines, while the presence of duplicated target TTAA sites at either ends of individual insertions confirmed characteristic piggyBac transposition events in these three transgenic lines. The transgenic phenotype has remained stable for more than twenty generations. The transformations effected using the piggyBac element establish the potential of this element as a germ-line transformation vector for Aedine mosquitoes. [source]

Morphology Transition of Block Copolymers under Curved Confinement

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 8 2007
Xingqing Xiao
Abstract The morphology transitions in AB diblock and ABA triblock copolymers confined between flat and curved surfaces were investigated by MC simulations. Upon variation of the extent of frustration between thickness d and bulk lamellae period L0, parallel and vertical or distorted vertical lamellar structures appear in both flat and curved confinements. With increasing curvature, the compatibility of d and L0 becomes more perturbed so that perfectly parallel lamellae are formed with increasing difficulty. Owing to the smaller L0 of ABA as compared to AB, the transformation frequency of the incompatible region of d/L0(ABA) is more notable for ABA and the corresponding transformation period is larger than that of AB. [source]

Overcoming the restriction barrier to plasmid transformation of Helicobacter pylori

MOLECULAR MICROBIOLOGY, Issue 5 2000
John P. Donahue
Helicobacter pylori strains demonstrate substantial variability in the efficiency of transformation by plasmids from Escherichia coli, and many strains are completely resistant to transformation. Among the barriers to transformation are numerous strain-specific restriction-modification systems in H. pylori. We have developed a method to protect plasmid DNA from restriction by in vitro site-specific methylation using cell-free extracts of H. pylori before transformation. In two cases, plasmid DNA treated with cell-free extracts in vitro acquired the restriction pattern characteristic of genomic DNA from the source strain. Among three strains examined in detail, the transformation frequency by treated plasmid shuttle and suicide vectors was significantly increased compared with mock-treated plasmid DNA. The results indicate that the restriction barrier in H. pylori can be largely overcome by specific DNA methylation in vitro. The approach described should significantly enhance the ability to manipulate gene function in H. pylori and other organisms that have substantial restriction barriers to transformation. [source]

Influence of genetic background on transformation and expression of Green Fluorescent Protein in Actinobacillus actinomycetemcomitans

MOLECULAR ORAL MICROBIOLOGY, Issue 5 2005
W. Teughels
Background/aims:, The development of an electro-transformation system and the construction of shuttle plasmids for Actinobacillus actinomycetemcomitans have enhanced the molecular analysis of virulence factors. However, inefficient transformation is frequently encountered. This study investigated the efficiency of electro-transformation and expression of Green Fluorescent Protein (GFP) in 12 different A. actinomycetemcomitans strains. The influence of the plasmid vector, serotype, and phenotype were the major factors taken into consideration. Material and methods:, Twelve serotyped A. actinomycetemcomitans strains were independently electro-transformed with two different Escherichia coli,A. actinomycetemcomitans shuttle plasmids (pVT1303 and pVT1304), both containing an identical ltx-GFPmut2 gene construct but a different backbone (pDMG4 and pPK1, respectively). The transformation efficiency, transformation frequency, and electro-transformation survival rate were determined by culture techniques. GFP expression was observed at the colony level by fluorescence microscopy. Results:, All strains could be transformed with both plasmids. However, major differences were observed for the transformation efficiency, transformation frequency, and electro-transformation survival rate between strains. The data demonstrated that plasmid vector, serotype, and phenotype are key players for obtaining a successful transformation. An inverted relationship between the electro-transformation survival rate and tranformation frequency was also observed. GFP expression was also influenced by phenotype, serotype and plasmid vector. Conclusions:, The serotype of A. actinomycetemcomitans has an important influence on its survival after electro-transformation and on transformation frequency. The expression of GFP is strain and plasmid vector dependent. [source]