Strain (chemistry)

About: Strain (chemistry) is a research topic. Over the lifetime, 13139 publications have been published within this topic receiving 169821 citations.

Isogenic strain construction and gene mapping in Candida albicans.

Abstract: Genetic manipulation of Candida albicans is constrained by its diploid genome and asexual life cycle. Recessive mutations are not expressed when heterozygous and undesired mutations introduced in the course of random mutagenesis cannot be removed by genetic back-crossing. To circumvent these problems, we developed a genotypic screen that permitted identification of a heterozygous recessive mutation at the URA3 locus. The mutation was introduced by targeted mutagenesis, homologous integration of transforming DNA, to avoid introduction of extraneous mutations. The ura3 mutation was rendered homozygous by a second round of transformation resulting in a Ura- strain otherwise isogenic with the parental clinical isolate. Subsequent mutation of the Ura- strain was achieved by targeted mutagenesis using the URA3 gene as a selectable marker. URA3 selection was used repeatedly for the sequential introduction of mutations by flanking the URA3 gene with direct repeats of the Salmonella typhimurium hisG gene. Spontaneous intrachromosomal recombination between the flanking repeats excised the URA3 gene restoring a Ura- phenotype. These Ura- segregants were selected on 5-fluoroorotic acid-containing medium and used in the next round of mutagenesis. To permit the physical mapping of disrupted genes, the 18-bp recognition sequence of the endonuclease I-SceI was incorporated into the hisG repeats. Site-specific cleavage of the chromosome with I-SceI revealed the position of the integrated sequences.

Allylic 1,3-strain as a controlling factor in stereoselective transformations

Abstract: 5. Stereoselective Intermolecular Addhion Reactions to Double Bonds Controlled by Allylic 1,bStrain 5.1. Hydrogenation 5.2. Hydroboration 5.3. Epoxldation and Cycbpropanation 8. Diastereoselecthre Enolate Alkylations Controlled by Allyllc 1.3-Strain 7. Chirality Transfer in Reactions of Allylsilanes and Allylboronates 8. Nucleophilic AddRion to Double Bonds Controlled by Allylic 1.3-Strain 9. Reactions of Benzylic Systems Controlled by Allylic 1,3-Strain 10. Allylic 1 ,bStrain Control of Dlastereoselecthre Reactions InvoMng Heteroallyl Systems 10.1. 2-Azaallyl Systems 10.2. 2-Oxonlaallyl Systems 10.3. Ntrones 10.4. Other Azaallyllc Systems 10.5. Vinyl Sulfoxides 11. Conformational Control around Bonds to Three-Membered Rings Related to Allylic 1.3-Strain 12. Epilogue