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11.
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Takahiro Makino Kimihiko Kato Hiroyuki Lyozumi Hiroe Honzawa Yoshiaki Tachiiri Mitsuo Hiramatsu † 《Photochemistry and photobiology》1996,64(6):953-956
Abstract— Ultraweak luminescence generated by sweet potato and nonpathogenic Fusarium oxysporum interactions associated with a defense response was detected by a photoncounting method using ultrahigh-sensitive photodetectors. The time-dependent intensity variation, the spectrum and the two-dimensional imaging of the ultraweak luminescence are indicative of the defense response of the sweet potato to F. oxysporum. The production of ipomeamarone as a phytoalexin means that F. oxysporum induced the defense response in the sweet potato. 相似文献
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14.
Recently studies of less stable rotational isomers became possible using a combination of low-temperature matrix-isolation infrared spectroscopy and either the high-temperature nozzle technique or irradiation with ultraviolet or near-infrared light. In this paper the infrared spectra of the less stable cis form of N-methylformamide and N-methylacetamide and their variously deuterated species were obtained in low-temperature nitrogen matrices using the high-temperature nozzle technique. The assignments of the bands due to the cis form as well as the trans form were made on the basis of normal-coordinate calculations. 相似文献
15.
Appropriately protected guanosine derivatives were successfully converted to the corresponding O6-substituted guanosine derivatives by treatment with dialkyl- or diaryl-phosphoryl halides, dialkyl- or diaryl-phosphinothioyl halides, arenesulfonyl chlorides, and trialkylsilyl chlorides. 相似文献
16.
Mitsuo Takayama Michiko Iwamura Shohaku Fuchibe 《Journal of mass spectrometry : JMS》1994,29(11):601-606
The formation of molecular ions, M+., under fast atom bombardment (FAB) conditions using a liquid matrix was examined by using a new type of synthesized compounds in which preferential M+. peaks appear in their FAB spectra. The FAB spectra were compared with the corresponding mass spectra obtained by the electron impact (EI) ionization, chemical ionization (CI) and charge-exchange ionization (CEI) methods. All of the spectra showed preferential peaks of M+. ion and a characteristic intense fragment ion peak originating from a β-fission. The FAB spectra were similar in the fragment ions appearing in the EI spectra and were very similar in the fragmentation pattern to the CEI spectra using Ar+. and Xe+. as the reagent ions. Further, the FAB spectra did not show any doubly charged ion peaks, while the 70 eV EI spectra showed the peaks of doubly charged molecular and/or fragment ions. The isobutane CI spectra of the synthesized compounds suggested that the formation of M+. ions occurred through the CE reaction with isobutane ion, C4H10+., and the CI spectra showed a marked intense fragment ion peak originating from the β-fission which seemed to occur characteristically in CEI processes. The results obtained suggested that the formation of M+. ions under matrix FAB conditions occurred mainly by CE reactions between the analytes M and matrix molecular ions B+. and/or fragment ions b+.. 相似文献
17.
Horiyama S Suwa K Yamaki M Kataoka H Katagi T Takayama M Takeuchi T 《Chemical & pharmaceutical bulletin》2002,50(7):996-1000
Hydroxylamines gradually undergo oxidation to their oximes on being dissolved in organic solvent (e.g. methanol). This phenomenon was followed by (1)H-NMR and liquid chromatography-mass spectrometry (LC-MS). The oxidation rate was estimated from the peak area observed on the mass chromatogram at the protonated molecule or fragment ion on LC-atmospheric pressure chemical ionization (APCI)-MS. The results showed that the oxidation rate of hydroxylamines depended on the solvent type. 相似文献
18.
Kon Y Ogasawara J Sakamoto K Kabuto C Kira M 《Journal of the American Chemical Society》2003,125(31):9310-9311
A silicon-containing fused bicyclic compound with a highly strained bridgehead double bond, 2,3,6,7-tetra-tert-butyl-4-(tert-butyldimethylsilyl)-5-(tert-butyldimethylsiloxy)-5-silabicyclo[3.2.0]hepta-1,3,6-triene (2), was synthesized quantitatively by the reaction of 1,2-bis-tert-butyl-4,4-bis(tert-butyldimethylsilyl)-4-silatriafulvene (3) with di-tert-butylcyclopropenone (4) at 80 degrees C. An X-ray crystallographic analysis for 2 not only confirmed a bicyclic structure having a silacyclopentadiene (silole) ring fused with a silacyclobutene ring but also the remarkable deformation around the double bonds; the sum of the bond angles around the unsaturated bridgehead carbon was 333 degrees . The strain energy of a model 5-silabicyclo[3.2.0]hepta-1,3,6-triene was calculated at the MP2/6-31+G(d,p)//B3LYP/6-31+G(d) level (30.2 kcal/mol) to be comparable to that for parent bicyclo[3.2.0]hepta-1,3,6-triene (30.7 kcal/mol). Despite the high steric strain, 2 was stable enough to be kept intact for several months in the air. The high stability is ascribed to the effective steric protection of the ring system by the bulky substituents. 相似文献
19.
Perphenylcyclopolysilanes [Si(C6H5)2]n (n = 4, 5) are reduced by potassium to radical anions. Their simple ESR spectra demonstrate, that the extra electron is confined to the inner SinC2n skeleton of the uncleaved and presumably planarized cyclopolysilanes. 相似文献
20.
Oligonucleotides containing 2-thiouridine (s2U) in place of uridine form stable RNA duplexes with complementary RNAs. Particularly, this modified nucleoside has proved to recognize highly selectively adenosine, the genuine partner, without formation of a mismatched base pair with the guanosine counterpart. In this paper, we describe new methods for the synthesis of 2-thiouridine and various 2'-O-alkyl-2-thiouridine derivatives. Oligoribonucleotides having these modified nucleoside derivatives were synthesized, and their hybridization and structural properties were studied in detail by the 1H NMR analysis of these modified nucleosides and Tm experiments of RNA duplexes with their complementary RNA strands. 相似文献