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At least 343 records · Page 19Linked to original sources
PubMed2006

Construction of a positive selection marker by a lethal gene with the amber stop codon(s) regulator.

A novel positive selection marker for Escherichia coli transformation was developed. The marker consisted of a DNA fragment encoding the C-terminal ribonuclease domain (CRD) of colicin E3 (colE3) and one or more amber stop codons between the initiation codon and the E3-CRD coding sequence. The toxicity of the marker was controlled by the suppressor activity the host cells possessed. This allowed both effective selection and propagation of the vector possessing the maker by selecting appropriate hosts from among those widely distributed: sup+ strains for selection and sup0 strains for propagation respectively. The insert DNA fragment was introduced onto the vector by replacing the marker DNA. The transformants harboring the vector with an insert grew, but those without an insert were effectively removed by the killing activity of E3-CRD encoded on the marker DNA. The marker was also successfully applied to lambda phage display vector.

Codon, Terminator↗
PubMed2000

Stability of suspension formulations of lansoprazole and omeprazole stored in amber-colored plastic oral syringes.

OBJECTIVE: To determine the stability of lansoprazole and omeprazole suspensions at ambient and refrigerated temperatures using HPLC. DESIGN: The contents of lansoprazole and omeprazole capsules were suspended in separate flasks containing sodium bicarbonate 8.4% to concentrations of 3 and 2 mg/mL, respectively. The contents of each flask were drawn into six amber-colored oral syringes, with one-half of the syringes stored at 22 degrees C (ambient) and the other half at 4 degrees C. Lansoprazole and omeprazole concentrations were determined by a stability-indicating HPLC assay at baseline and at 4, 8, 12, and 24 hours, and on days 4, 7, 14, 21, 30, 45, and 60 after mixing. Both omeprazole and lansoprazole were considered stable if they retained > or =90% of the baseline drug concentration. RESULTS: Omeprazole was stable for up to 14 days at 22 degrees C and 45 days at 4 degrees C. Lansoprazole was stable for eight hours at 22 degrees C and for 14 days at 4 degrees C. CONCLUSIONS: When compared with ambient or refrigerated storage conditions, omeprazole was stable for a longer duration than lansoprazole. Pharmacists may use these results to guide compounding and storage of proton-pump inhibitor suspensions.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed1976

[Genetic study of bacteriophage phi81. I. Isolation, study of complementation and preliminary mapping of amber-mutants of bacteriophage phi81].

123 Amber mutants of lambdoid bacteriophage phi81 are isolated and distributed into 19 complementation groups. Deletion mapping made possible to locate 5 gene groups on the genetic map of bacteriophage phi81 and to determine a region of possible location of mm' sticky ends on the prophage genetic map. A gene of phage phi81 is localized, which controls the adsorption specificity, and which functional similarity to a respective gene of phage phi80 is demonstrated.

Chromosome Mapping↗
PubMed2006

[Slurry sampling for direct determination of trace cadmium in amber by graphite furnace atomic absorption spectrometry].

A method for the direct determination of trace cadmium in amber by graphite furnace atomic absorption spectrometry (GFAAS) with slurry sampling was described. Palladium nitrate was used as a matrix modifier to eliminate the interference. Slurry stability and the influences of the matrix modifier, ashing/atomization temperature and coexistent ions on analytical signals were investigated in detail. Under the optimized experimental conditions, the detection limit of this method was 9.4 ng x g(-1) with a precision of 6.1%.

English Abstract↗
PubMed1991

Dimensional oscillation. A fast variation of energy embedding gives good results with the AMBER potential energy function.

The structure of the AMBER potential energy surface of the cyclic tetrapeptide cyclotetrasarcosyl is analyzed as a function of the dimensionality of coordinate space. It is found that the number of local energy minima decreases as the dimensionality of the space increases until some limit at which point equipotential subspaces appear. The applicability of energy embedding methods to finding global energy minima in this type of energy-conformation space is explored. Dimensional oscillation, a computationally fast variant of energy embedding is introduced and found to sample conformation space widely and to do a good job of finding global and near-global energy minima.

Computer Simulation↗
PubMed1988

Construction, expression, and function of a new yeast amber suppressor, tRNATrpA.

The number of different tRNA species in Saccharomyces cerevisiae known to be capable of suppressing termination of translation at UAG, UAA, and UGA codons is limited to those which insert tyrosine, leucine, and serine. Suppressor tRNAs that insert other amino acids, even those whose anticodons differ from the expected recognition sequences for nonsense codons by a single nucleotide, have never been identified via classical genetic analysis. We have used site-directed mutagenesis to convert the anticodon of a cloned tRNATrp gene from CCA to CTA with the expectation that this gene would produce tRNA molecules capable of interacting with the UAG terminator codon. We show that this form of the gene can be transcribed and spliced in vitro to produce mature tRNA with the expected base sequence. The putative suppressor gene has been introduced into several S. cerevisiae host strains using the centromere vector YCp19. Efficient suppression of amber mutations met8-1, tyr7-1, and lys2-801 results from the presence of the CTA form of tDNATrp. Two UAA mutants, leu2-1 and ade2-101, and the UGA marker his4-260 are not suppressed.

Bacterial Proteins↗
PubMed2001

A study of amber and copal samples using FT-Raman spectroscopy.

FT-Raman spectra were collected from fossil resins originating from a variety of geographical locations. The spectral profiles of most of the fossil resins could be related to modern resins containing diterpenoid components with predominantly labdane skeletons. The spectra collected from the fossil resin sample from Borneo differed from other fossil resins and was found to contain triterpenoid components. The differences in the spectral profile of fossil resins containing diterpenoid components are shown to relate to differences in level of maturation rather than geographical origin. FT-Raman spectra of fossil resins cannot be used to distinguish source although the degree of maturation can be used as an indicator to narrow the range of possible geographical origins.

Amber↗