| 1. |
- Amann, F., et al.
(författare)
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A search for murarregamma at the level of 10-13
- 1991
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Ingår i: Proceedings of the 25th International Conference on High Energy Physics. - 9810024347 ; , s. 1070-1071
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Konferensbidrag (refereegranskat)abstract
- The MEGA experiment, which is a search for the decay murarregamma with a branching ratio sensitivity of about 10-13, employs highly modular, fast detectors, state-of-the-art electronics, and a staged trigger with on-line filters. The detectors are contained in a 1.5-T solenoidal field produced by a superconducting magnet. Positrons are confined to the central region and are measured by a set of thin MWPCs. Photons are measured by one of four layers of pair spectrometers in the outer region. Most aspects of the design have been validated in engineering runs; data taking will begin in 1990 with much of the electron arm and one pair spectrometer layer installed.
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| 2. |
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| 3. |
- Szymanski, J. J., et al.
(författare)
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MEGA : A search for the decay mu –> e gamma
- 1994
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Ingår i: Intersections between particle and nuclear physics. Proceedings, 5th Conference, St. Petersburg, USA, May 31-June 6, 1994. ; , s. 789-792
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Konferensbidrag (refereegranskat)
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| 4. |
- Egholm, M., et al.
(författare)
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PNA HYBRIDIZES TO COMPLEMENTARY OLIGONUCLEOTIDES OBEYING THE WATSON-CRICK HYDROGEN-BONDING RULES
- 1993
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 365:6446, s. 566-568
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Tidskriftsartikel (refereegranskat)abstract
- DNA ANALOGUES are currently being intensely investigated owing to their potential as gene-targeted drugs1-3. Furthermore, their properties and interaction with DNA and RNA could provide a better understanding of the structural features of natural DNA that determine its unique chemical, biological and genetic properties3,4. We recently designed a DNA analogue, PNA, in which the backbone is structurally homomorphous with the deoxyribose backbone and consists of N-(2-aminoethyl)glycine units to which the nucleobases are attached5-9. We showed that PNA oligomers containing solely thymine and cytosine can hybridize to complementary oligonucleotides, presumably by forming Watson-Crick-Hoogsteen (PNA)2-DNA triplexes, which are much more stable than the corresponding DNA-DNA duplexes5-7, and bind to double-stranded DNA by strand displacement5,8. We report here that PNA containing all four natural nucleobases hybridizes to complementary oligonucleotides obeying the Watson-Crick base-pairing rules, and thus is a true DNA mimic in terms of base-pair recognition.
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| 5. |
- Eriksson, M., et al.
(författare)
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LOCATION OF EXCIMER-FORMING ADDUCTS OF (+)-ANTI-BENZO A PYRENE DIOL EPOXIDE IN DNA
- 1993
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 115:5, s. 1639-1644
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Tidskriftsartikel (refereegranskat)abstract
- Covalent adducts of the carcinogenic polycyclic aromatic hydrocarbon (+)-anti-benzo[a]pyrene 7,8-dihydrodiol 9,10-epoxide ((+)-anti-BPDE) in polynucleotides have been studied by fluorescence spectroscopy. The pyrenyl chromophores of the BPDE adducts, linked by the C10 atom to the exocyclic nitrogen of guanine, interact in the photoexcited state, as evidenced by excimer fluorescence. Strong BPDE excimer fluorescence is observed in the alternating poly(dGdC).poly(dGdC) sequence, whereas it is weak in the homopolymeric poly(dG).poly(dC) and in calf thymus DNA. No excimer fluorescence is observed for the BPDE adducts in poly(dAdC).poly(dGdT) or poly(dAdG).poly(dCdT). It is concluded that the formation of BPDE excimers in polynucleotides requires binding to guanines on different strands on consecutive basepairs. The experimental results are supported by graphics modeling and energy minimization of BPDE adducts in various oligonucleotide sequences. The results show that the most favorable arrangement for excimer formation of the BPDE-dG adducts is in a 5'(dCdG-BPDE).5'(dCdG-BPDE) sequence, where the pyrenyl chromophores interact in the minor groove.
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| 6. |
- Eriksson, Svante, 1957, et al.
(författare)
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BINDING OF 4',6-DIAMIDINO-2-PHENYLINDOLE (DAPI) TO AT REGIONS OF DNA - EVIDENCE FOR AN ALLOSTERIC CONFORMATIONAL CHANGE
- 1993
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 1520-4995 .- 0006-2960. ; 32:12, s. 2987-2998
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Tidskriftsartikel (refereegranskat)abstract
- The interaction of 4',6-diamidino-2-phenylindole (DAPI) with several double-helical poly- and oligonucleotides has been studied in solution using optical spectroscopic techniques: flow linear dichroism (LD), induced circular dichroism (CD), and fluorescence spectroscopy. In AT-rich sequences, where DAPI is preferentially bound, LD indicates that the molecule is edgewise inserted into the minor groove at an angle of approximately 45-degrees to the helix axis. This binding geometry is found for very low as well as quite high binding ratios. The concluded geometry is in agreement with that of the DAPI complex in a crystal with the Drew-Dickerson dodecamer, and the DAPI complex with this dodecamer in solution is verified to have an ICD spectrum similar to that of the complex with [poly(dA-dT)]2 at low binding ratios. The observation of two types of CD spectra characteristic for the binding of DAPI to DNA, and also for the interaction with [poly(dA-dT)]2, demonstrates that the first binding mode, despite its low apparent abundance (a few percent), is not due to a specific DNA site. The effect may be explained in terms of an allosteric binding such that when DAPI molecules bind contiguously to the AT sequence the conformation of the latter is changed. The new conformation, which according to LD appears to be stiffer than normal B-form DNA, is responsible for the second type of induced CD spectrum in the DAPI chromophore. Although the spectroscopic results indicate a change of DNA conformation, consistent with an allosteric binding model, they do not explicitly require any cooperativity, but accidental neighbors could also explain the data.
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| 7. |
- Graslund, A., et al.
(författare)
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DYNAMICS OF BENZO A PYRENE DIOL EPOXIDE ADDUCTS IN POLY(DG-DC) . (DG-DC) STUDIED BY SYNCHROTRON EXCITED FLUORESCENCE POLARIZATION ANISOTROPY DECAY
- 1992
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Ingår i: Biophysical Chemistry. - : Elsevier BV. - 1873-4200 .- 0301-4622. ; 44:1, s. 21-28
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Tidskriftsartikel (refereegranskat)abstract
- Time-resolved fluorescence studies have been performed on (+)-anti-7,8-dihydrodiol-9,10-epoxy-benzo[a]pyrene adducts in double-stranded poly(dG-dC) . (dG-dC). Part of the adduct population gives rise to excimer fluorescence. The heterogeneous fluorescence emission decay curves at 22-degrees-C could be resolved into three components with lifetimes: 0.4 ns, 3 ns and 24 ns for the total fluorescence (monomer and excimer emission), and 0.5 ns, 5 ns and 24 ns, respectively, for excimer emission alone. The relative amplitudes for the longer lifetimes were larger for the pure excimer population than for the mixed population. The fluorescence polarization anisotropy decay curves were resolved into two components of rotational correlation times: 0.4 ns and 25 ns for the total fluorescence and 0.3 ns and 33 ns for the excimer fluorescence. We interpret the two rotational correlation times to correspond to local motion of the adduct and segmental motion of the polynucleotide, respectively.
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| 8. |
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| 9. |
- Kim, Seog K., et al.
(författare)
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ENHANCEMENT OF BINDING RATE OF RECA PROTEIN TO DNA BY CARCINOGENIC BENZO A PYRENE DERIVATIVES AND SELECTIVE CHANGE OF ADDUCT CONFORMATION
- 1993
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Ingår i: Carcinogenesis. - : Oxford University Press (OUP). - 0143-3334 .- 1460-2180. ; 14:2, s. 311-313
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Tidskriftsartikel (refereegranskat)abstract
- The association kinetics of RecA protein from Escherichia coli to DNA is strongly enhanced if even a minor fraction of DNA bases has been modified by a carcinogenic (+)-anti metabolite of benzo[a]pyrene (BPDE). The enhancement is much smaller with the less carcinogenic (-)-anti enantiomer of BPDE suggesting the possibility that the RecA protein binds selectively to the proto-oncogenic target. Most importantly, the binding of RecA to DNA modified with the latter enantiomer is found to give rise to a reorganization of this BPDE adduct from an intercalation site into a minor groove site. This indicates that the binding mechanism of RecA is via intercalation of some amino acid moiety, a discovery that could explain the approximately 50% contour length increase of the DNA within its fibrous complex with RecA.
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| 10. |
- Kim, Seog K., et al.
(författare)
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INTERACTION OF 4',6-DIAMIDINO-2-PHENYLINDOLE (DAPI) WITH POLY D(G-C)2 AND POLY D(G-M(5)C)2 - EVIDENCE FOR MAJOR GROOVE BINDING OF A DNA PROBE
- 1993
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 115:9, s. 3441-3447
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Tidskriftsartikel (refereegranskat)abstract
- The interactions of DAPI with poly[d(G-C)2] and poly[d(G-m5C)2] are characterized by optical spectroscopic methods. DAPI is found to bind to poly[d(G-C)2] with its molecular long-axis roughly perpendicular but with its plane more parallel to the belix axis of the polynucleotide, probably being bound in a non-intercalated way in the major groove of the polynucleotide. In poly[d(G-m5C)2], DAPI is bound with its molecular plane perpendicular to the helix axis, probably partially intercalated from the major groove. The conclusions are supported by fluorescence quenching results. Together with the earlier established minor groove binding mode of DAPI in the AT regions, our results demonstrate a heterogeneous nature of the interaction of a small ligand with DNA. We conclude that the conventional classification of a ligand as being either intercalator, minor groove binder, or major groove binder may not be adequate since the mode of binding clearly depends also on the base sequence.
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