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1.
Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
2.
Role of DNA superhelicity in partitioning of the pSC101 plasmid 总被引:24,自引:0,他引:24
Previous work has shown that a cis-acting locus (termed par for partitioning) on the pSC101 plasmid accomplishes its stable inheritance in dividing cell populations. We report here that the DNA of pSC101 derivatives lacking the par region shows a decrease in overall superhelical density as compared with DNA of wild-type pSC101. Chemicals and bacterial mutations that reduce negative DNA supercoiling increase the rate of loss of par plasmids and convert normally stable plasmids that have minimal par region deletions into unstable replicons. topA gene mutations, which increase negative DNA supercoiling, reverse the instability of partition-defective plasmids that utilize the pSC101, p15A, F, or oriC replication systems. Our observations show that the extent of negative supercoiling of plasmid DNA has major effects on the plasmid's inheritance and suggest a mechanism by which the pSC101 par region may exert its stabilizing effects. 相似文献
3.
Summary Microsomal and soluble fractions of Pleurotus pulmonarius exhibited a reduced carbon monoxide difference spectrum with P450 maxima at 448nm and 450–452nm respectively. Substrate induced Type I spectra were observed on addition of benzo(a)pyrene to both fractions. Benzo(a)pyrene hydroxylation was measured using the aryl hydrocarbon hydroxylase assay and was observed to be P450 dependent as indicated by carbon monoxide inhibition together with the substrate binding characteristics. The activity of the fractions were observed to give Km of 200mM and 660mM and Vmax of 1.25 nmol/min/nmol P450 and 0.57 nmol/min/nmol P450 for the microsomal and cytosolic fractions respectively. 相似文献
4.
Fluoride ion promoted deprotection and transesterification in nucleotide triesters. 总被引:1,自引:1,他引:0 下载免费PDF全文
Tetrabutylammonium fluoride will remove phenyl, trichloroethyl and cyanoethyl groups from nucleotides. In addition to the desired nucleotide products other results including chain cleavage, phosphofluoridates and cyanoethylated thymidine units may be obtained depending on the conditions used. Fluoride ion has been used to successfully exchange phenyl and trichloroethyl groups for methyl, ethyl and butyl groups in nucleotide triesters. This represents a rapid high yield route to a variety of phosphate esters. The synthesis of a novel nucleotide analogue in which two chains are bridged through their phosphates is described. 相似文献
5.
Fluoride ion catalyzed alkylation of purines, pyrimidines, nucleosides and nucleotides using alky halides. 总被引:1,自引:1,他引:0 下载免费PDF全文
K K Ogilvie S L Beaucage M F Gillen D Entwistle M Quilliam 《Nucleic acids research》1979,6(4):1695-1708
Alkyl halides react rapidly with purines and pyrimidines in the presence of fluoride ion. Alkylation of thymidine leads to novel dimeric nucleoside derivatives bridged through N3. Alkylation of thymidine mono and dinucleotides leads to alkylation at the base (N3) as well as diester and triester formation at the phosphate. 相似文献
6.
Conjunctivitis and blepharospasm were observed in a litter of four, 2-week-old New Zealand white rabbits. Corneal opacity and neovascularization of the cornea and entropion of the upper eyelids were observed when the rabbits were examined 10 weeks later. Conjunctival cultures of these rabbits yielded normal bacterial flora. Treatment with a steroid-antibiotic ophthalmic ointment did not alter the ocular abnormalities. Surgical correction of the entropion resulted in a complete regression of all clinical signs. 相似文献
7.
Out of Africa and back again: nested cladistic analysis of human Y chromosome variation 总被引:18,自引:3,他引:15
Hammer MF; Karafet T; Rasanayagam A; Wood ET; Altheide TK; Jenkins T; Griffiths RC; Templeton AR; Zegura SL 《Molecular biology and evolution》1998,15(4):427-441
We surveyed nine diallelic polymorphic sites on the Y chromosomes of 1,544
individuals from Africa, Asia, Europe, Oceania, and the New World.
Phylogenetic analyses of these nine sites resulted in a tree for 10
distinct Y haplotypes with a coalescence time of approximately 150,000
years. The 10 haplotypes were unevenly distributed among human populations:
5 were restricted to a particular continent, 2 were shared between Africa
and Europe, 1 was present only in the Old World, and 2 were found in all
geographic regions surveyed. The ancestral haplotype was limited to African
populations. Random permutation procedures revealed statistically
significant patterns of geographical structuring of this paternal genetic
variation. The results of a nested cladistic analysis indicated that these
geographical associations arose through a combination of processes,
including restricted, recurrent gene flow (isolation by distance) and range
expansions. We inferred that one of the oldest events in the nested
cladistic analysis was a range expansion out of Africa which resulted in
the complete replacement of Y chromosomes throughout the Old World, a
finding consistent with many versions of the Out of Africa Replacement
Model. A second and more recent range expansion brought Asian Y chromosomes
back to Africa without replacing the indigenous African male gene pool.
Thus, the previously observed high levels of Y chromosomal genetic
diversity in Africa may be due in part to bidirectional population
movements. Finally, a comparison of our results with those from nested
cladistic analyses of human mtDNA and beta-globin data revealed different
patterns of inferences for males and females concerning the relative roles
of population history (range expansions) and population structure
(recurrent gene flow), thereby adding a new sex-specific component to
models of human evolution.
相似文献
8.
Grajkowski A Cieślak J Gapeev A Schindler C Beaucage SL 《Bioconjugate chemistry》2010,21(11):2147-2152
The ribonucleoside building block, N2-isobutyryl-2'-O-propargyl-3'-O-levulinyl guanosine, was prepared from commercial N2-isobutyryl-5'-O-(4,4'-dimethoxytrityl)-2'-O-propargyl guanosine in a yield of 91%. The propargylated guanylyl(3'-5')guanosine phosphotriester was synthesized from the reaction of N2-isobutyryl-2'-O-propargyl-3'-O-levulinyl guanosine with N2-isobutyryl-5'-O-(4,4'-dimethoxytrityl)-2'-O-tert-butyldimethylsilyl-3'-O-[(2-cyanoethyl)-N,N-diisopropylaminophosphinyl] guanosine and isolated in a yield of 88% after P(III) oxidation, 3'-/5'-deprotection, and purification. The propargylated guanylyl(3'-5')guanosine phosphotriester was phosphitylated using 2-cyanoethyl tetraisopropylphosphordiamidite and 1H-tetrazole and was followed by an in situ intramolecular cyclization to give a propargylated c-di-GMP triester, which was isolated in a yield of 40% after P(III) oxidation and purification. Complete N-deacylation of the guanine bases and removal of the 2-cyanoethyl phosphate protecting groups from the propargylated c-di-GMP triester were performed by treatment with aqueous ammonia at ambient temperature. The final 2'-desilylation reaction was effected by exposure to triethylammonium trihydrofluoride affording the desired propargylated c-di-GMP diester, the purity of which exceeded 95%. Biotinylation of the propargylated c-di-GMP diester was easily accomplished through its cycloaddition reaction with a biotinylated azide derivative under click conditions to produce the biotinylated c-di-GMP conjugate of interest in an isolated yield of 62%. 相似文献
9.
JG Hansen W Gao J Dupuis GT O’Connor W Tang M Kowgier A Sood SA Gharib LJ Palmer M Fornage SR Heckbert BM Psaty SL Booth SUNLIGHT Consortium Patricia A Cassano 《Respiratory research》2015,16(1)
Background
Vitamin D is associated with lung function in cross-sectional studies, and vitamin D inadequacy is hypothesized to play a role in the pathogenesis of chronic obstructive pulmonary disease. Further data are needed to clarify the relation between vitamin D status, genetic variation in vitamin D metabolic genes, and cross-sectional and longitudinal changes in lung function in healthy adults.Methods
We estimated the association between serum 25-hydroxyvitamin D [25(OH)D] and cross-sectional forced expiratory volume in the first second (FEV1) in Framingham Heart Study (FHS) Offspring and Third Generation participants and the association between serum 25(OH)D and longitudinal change in FEV1 in Third Generation participants using linear mixed-effects models. Using a gene-based approach, we investigated the association between 241 SNPs in 6 select vitamin D metabolic genes in relation to longitudinal change in FEV1 in Offspring participants and pursued replication of these findings in a meta-analyzed set of 4 independent cohorts.Results
We found a positive cross-sectional association between 25(OH)D and FEV1 in FHS Offspring and Third Generation participants (P = 0.004). There was little or no association between 25(OH)D and longitudinal change in FEV1 in Third Generation participants (P = 0.97). In Offspring participants, the CYP2R1 gene, hypothesized to influence usual serum 25(OH)D status, was associated with longitudinal change in FEV1 (gene-based P < 0.05). The most significantly associated SNP from CYP2R1 had a consistent direction of association with FEV1 in the meta-analyzed set of replication cohorts, but the association did not reach statistical significance thresholds (P = 0.09).Conclusions
Serum 25(OH)D status was associated with cross-sectional FEV1, but not longitudinal change in FEV1. The inconsistent associations may be driven by differences in the groups studied. CYP2R1 demonstrated a gene-based association with longitudinal change in FEV1 and is a promising candidate gene for further studies.Electronic supplementary material
The online version of this article (doi:10.1186/s12931-015-0238-y) contains supplementary material, which is available to authorized users. 相似文献10.
Grajkowski A Cieślak J Kauffman JS Duff RJ Norris S Freedberg DI Beaucage SL 《Bioconjugate chemistry》2008,19(8):1696-1706
The functionalization of long chain alkylamine controlled-pore glass (CPG) with a 3-hydroxypropyl-(2-cyanoethyl)thiophosphoryl linker and its conversion to the support 7 has led to the synthesis of DNA oligonucleotides and their 3'- or (3',5')-conjugates. Indeed, CPG support 7 has been successfully employed in the synthesis of both native and fully phosphorothioated DNA 20-mers. Unlike conventional succinylated CPG supports, this distinctively functionalized support allows oligonucleotide deprotection and removal of the deprotection side products to proceed without releasing the oligonucleotide into the aqueous milieu. When freed from deprotection side products, the DNA oligonucleotide is thermolytically released from the support within 2 h under nearly neutral conditions (pH 7.2, 90 degrees C). The quality of these oligonucleotides is comparable to that of identical oligonucleotides synthesized from succinylated CPG supports in terms of shorter than full length oligonucleotide contaminants and overall yields. The versatility of the thermolytic CPG support 7 is further demonstrated by the synthesis of a DNA oligonucleotide (20-mer) and its conjugation with an azido and alkynyl groups at both 5'-and 3'-termini, respectively. The functionality of the (3',5')-heteroconjugated oligonucleotide 18 is verified by its circularization to the DNA oligonucleotide 19 under "click" chemistry conditions. 相似文献