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- Engman, Cecilia, 1974, et al.
(författare)
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DNA adopts normal B-form upon incorporation of highly fluorescent DNA base analogue tC: NMR structure and UV-Vis spectroscopy characterization
- 2004
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Ingår i: Nucleic Acids Research. - : Oxford University Press (OUP). - 1362-4962 .- 0305-1048. ; 32:17, s. 5087-95
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the highly fluorescent tricyclic cytosine base analogue (tC) on duplex DNA conformation is investigated. The duplex properties are characterized by absorbance and circular dichroism (CD) for all combinations of neighbouring bases to tC, and an NMR structure is determined for one tC-containing sequence. For the oligonucleotides with one tC incorporated instead of cytosine, the melting temperature is increased on average by 2.7 degrees C above that for the unmodified ones. CD spectra are practically identical for modified and unmodified sequences, indicating an unperturbed B-DNA conformation. The NMR structure determination of the self-complementary sequence 5'-CTC(tC)ACGTGGAG shows a DNA conformation consistent with B-form for the whole duplex. The root-mean-square distance for the nucleotides of the eight central base pairs between the 10 structures with lowest CYANA target functions and a mean structure is 0.45 +/- 0.17 A. The NMR data confirm correct base pairing for tC by the observation of both intrastrand and interstrand imino proton NOEs. Altogether, this suggests that tC works well as a cytosine analogue, i.e. it is situated in the base stack, forming hydrogen bonds with G in the complementary strand, without distorting the DNA backbone conformation. This first example of an artificial, highly fluorescent DNA base that does not perturb the DNA conformation could have valuable applications for the study of the structure and dynamics of nucleic acid systems.
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| 3. |
- Sjögren, Torsten, et al.
(författare)
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High Performance Piston Rings for Two-Stroke Marine Diesel Engines
- 2004
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Ingår i: Proceedings // 24th CIMAC World Congress on Combustion Engine Technology.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The piston ring is a key component in a marine combustion engine. High mechanical loads, relatively high temperatures and corrosive gases and liquids influence its performance in terms of sealing capacity, wear of cylinder liner and the ring itself. Base material of the ring, coating technology and ring geometry design are discussed in the article.When tailoring cast iron materials suitable as piston ring base material two parameters are of importance; the morphology of the graphite and the constituents of the matrix. To optimize the properties of the cast iron a compromise is needed to achieve a satisfactory performance of the piston rings.Daros Piston Rings AB is currently developing a second generation of chromium-ceramic coating the so called Z-chrome. The objective of this project has been to increase the maximum operating temperature of the coating and leave the other characteristics of the coating unaffected. The difference between the commercial Daros coating Tritor® and the Z-chrome is the ceramic component included in the coated layer.Insufficient conformability of piston ring and liner geometry may produce a large local cylinder wall pressure which will destroy the oil film leading to uncontrolled wear and scuffing. Lack of conformability can also produce leakage paths for the combustion gases. Therefore a correct ring shape is of utmost importance. A new design philosophy designated OPCORE® has been developed and is presented here.
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| 4. |
- Wilhelmsson, Marcus, 1974, et al.
(författare)
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Photophysical Characterization of Fluorescent DNA Base Analogue, tC
- 2003
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 107:34, s. 9094-9101
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Tidskriftsartikel (refereegranskat)abstract
- The novel fluorescent DNA cytosine base analogue 1,3-diaza-2-oxophenothiazine, tC, has previously been shown to have a remarkably preserved high quantum yield upon incorporation into a single strand of peptide nucleic acid, PNA, as well as when the latter is hybridized with a complementary DNA to form a PNA-DNA duplex. Here, we investigate fundamental photophysical properties of tC. Using fluorescence anisotropy, stretched film linear dichroism, and quantum chemical calculations, the transition moment polarizations of the lowest lying electronic states are determined. The neutral, base-pairing form of tC, having a fluorescence quantum yield of 0.2, is found to be the totally predominant species in a wide pH interval, 4-12. We show that the absorption band of tC at lowest energy, centered at 26 700 cm(-1) and well separated from the nucleobase absorption, is due to a single electronic transition polarized approximately at 35degrees from the long axis of the molecule. The 2-deoxyribonucleoside of 1,3-diaza-2-oxophenothiazine, synthesized for further incorporation into DNA, was found to display a fluorescence quantum yield nearly the same as in the form of tC that was incorporated into PNA, confirming the notion of the tC nucleoside being a probe with very promising fluorescence properties essentially invariant of environment, also upon incorporation into a DNA strand and upon hybridization.
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