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C Jeppesen

Publications and source records attributed to C Jeppesen.

28 records · Page 2Linked to original sources
PubMed1988

Photocleavage of DNA and photofootprinting of E. coli RNA polymerase bound to promoter DNA by azido-9-acridinylamines.

The long-wavelength ultraviolet (lambda approximately 420 nm) radiation induced reaction between 6-azido-2-methoxy-9-acridinylamines and supercoiled plasmid DNA results in single strand scissions and formation of covalent adducts (ratio approximately 1:10). By treating azidoacridine-photomodified DNA with piperidine at 90 degrees C, additional strand scissions are observed in a complex sequence dependent manner with an overall preference for T greater than or equal to G greater than C much greater than A. The resulting DNA fragments migrate as 5'-phosphates in polyacrylamide gels. Photofootprinting of the binding site of RNA-polymerase on promoter DNA is demonstrated with an azido-9-acridinylamino-octamethylene-9-aminoacridine. Similar experiments using 9-amino-6-azido-2-methoxyacridine indicate that this reagent recognizes changes in the DNA conformation induced by RNA polymerase binding, in relation to open complex formation.

Aminoacridines↗
PubMed1988

Adenosine-guanosine preferential photocleavage of DNA by azido-benzoyl- and diazocyclopenta-dienylcarbonyloxy derivatives of 9-aminoacridine.

The photoreactions of 9-[6-(4-azidobenzamido)hexylamino]acridine (AHA) and 9-[6-(2-diazocyclopentadienylcarbonyloxy)hexylamino]acridine (DHA) with double stranded DNA result in formation of single strand nicks and alkali labile sites (adducts) with an efficiency of 6 x 10(-3) nicks per AHA and 3 x 10(-2) nicks per DHA molecule. The alkali dependent DNA cleavage by AHA shows a pronounced A+G preference whereas that by DHA is practically sequence independent. In the presence of diacridines, however, DHA exhibits a preference for cleavage at guanosines. These DNA photocleaving reagents could be useful for DNA photofootprinting and photosequencing.

Adenosine↗
PubMed1988

Detection of intercalation-induced changes in DNA structure by reaction with diethyl pyrocarbonate or potassium permanganate. Evidence against the induction of Hoogsteen base pairing by echinomycin.

Binding of the bis-intercalators echinomycin and N,N'-di(9-acridinyl)spermidine or the mono-intercalators 9-aminoacridine and ethidium to DNA induces hypersensitivity of adenines towards reaction with diethyl pyrocarbonate. It is proposed that this hyperreactivity is due to the DNA helix unwinding and extension induced by intercalation, thereby exposing N7 in the major groove, and not as previously suggested to the formation of Hoogsteen base pairing. Hypersensitivity of thymines towards oxidation with permanganate is also induced upon binding of these drugs (especially the bis-intercalators) to DNA. This thymine hyperreactivity is both sequence- and intercalator-dependent, thereby indicating the potential of KMnO4 as a useful probe for analyzing the structure of intercalator-DNA complexes in solution.

Base Composition↗
PubMed1988

Nucleotide sequence determination and secondary structure of Xenopus U3 snRNA.

Using a combination of RNA sequencing and construction of cDNA clones followed by DNA sequencing, we have determined the primary nucleotide sequence of U3 snRNA in Xenopus laevis and Xenopus borealis. This molecule has a length of 219 nucleotides. Alignment of the Xenopus sequences with U3 snRNA sequences from other organisms reveals three evolutionarily conserved blocks. We have probed the secondary structure of U3 snRNA in intact Xenopus laevis nuclei using single-strand specific chemical reagents; primer extension was used to map the positions of chemical modification. The three blocks of conserved sequences fall within single-stranded regions, and are therefore accessible for interaction with other molecules. Models of U3 snRNA function are discussed in light of these data.

Animals↗
PubMed1988

Psoralen photofootprinting of protein-binding sites on DNA.

Using a BAL31 exonuclease assay to determine the sites of 4,5',8-trimethylpsoralen photocrosslinking in DNA we have shown that 5'-TA sites which are accessible to psoralen DNA interstrand photocrosslinking in naked DNA become inaccessible when protein, in casu, lambda-repressor E. coli or RNA polymerase are bound at their recognition DNA sequences (OR1 operator or deo1 promoter, respectively). These results show that psoralens can be used as photofootprinting reagents to study specific protein-DNA interactions.

Animals↗
PubMed1985

Ascorbic acid uptake to isolated nerve terminals and secretory granules from ox neurohypophyses.

Isolated nerve terminals (neurosecretosomes) from cow neurohypophyses accumulated radioactivity when they were incubated with L[14C]-ascorbic acid in an ionic medium dominated by NaCl. Uptake of radioactivity was saturable with ascorbic acid concentration. Replacement of Na+ with Li+ in the incubation medium or presence of ouabain inhibited the accumulation. Isolated, purified cow neurosecretory granules contained 14 +/- 2 nmol ascorbate (n = 10) per mg of protein. When such granules were incubated with L[14C]-ascorbic acid in a KCl dominated medium, they took up radioactivity slowly. The accumulation was not saturable with ascorbic acid concentration and was not influenced by the presence of Mg2+ATP.

Animals↗
PubMedDate not supplied

The computer as a laboratory for the physical chemistry of membranes.

A mini-review is given of some recent advances in the use of computer-simulation approaches to the study of physico-chemical properties of lipid bilayers and biological membranes. The simulations are based on microscopic molecular interaction models as well as random-surface models of fluid membranes. Particular emphasis is put on those properties that are controlled by the many-particle character of the lamellar membrane, i.e. correlations and fluctuations in density, composition and large-scale conformational structure. It is discussed how dynamic membrane heterogeneity arises and how it is affected by various molecular species interacting with membranes, such as cholesterol, drugs, insecticides, as well as polypeptides and integral membrane proteins. The influence of bending rigidity and osmotic-pressure gradients on large-scale membrane conformation and topology is described.

Journal Article↗