ISSN:0144-235X    

DOI:10.1080/01442358909353224

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The two major categories of organic solids are known to offer the present of good electrical conduction. The first group consists of charge-transfer complexes. Conductivity measurements on a large number of the charge-transfer complexes have been carried out. Among them, organic conductors (synthetic metals) and also organic superconductors have been discovered. The other group comprises single component materials; typical examples are polycyclic aromatic compounds and phthalocyanines. Their conductivities, generally speaking, are not as good as those of the charge transfer kind. We recently discovered a series of single component organic semiconductors having fairly good conductivity, which we called molecular fasteners. We also present, in this article, the experimental work on the ionization energy and carrier mobility measurements for the purpose of elucidating the conduction mechanism.

ISSN:0144-235X    

DOI:10.1080/01442358909353225

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Infrared and Raman spectroscopy is useful for studying helical conformations of polypeptides, which are determined by molecular structure parameters. Nuclear magnetic resonance spectroscopy, as well as X-ray analysis, is now established to be important for conformation studies of proteins and nucleic acids in solution. This article is mainly concerned with the conformational aspect and function regulation in protein biosynthesis. The strict recognition of transfer ribonucleic acid (tRNA) by aminoacyl-tRNA synthetase (ARS) is achieved by multi-step mutual adaptation. The conformations of ARS-bound amino acids have been elucidated by transferred nuclear Overhauser effect analysis. Aminoacyl-tRNA takes the 3′-isomeric form in the polypeptide chain elongation cycle. The regulation of codon recognition by post-transcriptional modification is achieved by conversion of the conformational characteristic of the anticodon of tRNA. The cytidine → lysidine modification of the anticodon of minor isoleucine tRNA concurrently converts the amino acid specificity and the codon specificity. As novel protein engineering, a basic strategy has been established forin vivobiosynthesis of proteins that are substituted with unnatural amino acids (alloproteins).

ISSN:0144-235X    

DOI:10.1080/01442358909353226

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

In optical-optical double resonance spectroscopy, the resonance transition from an intermediate state to a final state can be detected by a dip of the signal (fluorescence or ion) associated with the intermediate state. This method probing the signal of the intermediate state may be called ‘two-colour dip spectroscopy’. Various kinds of two-colour dip spectroscopy such as two-colour fluorescence/ion dip spectroscopy, two-colour ionization dip spectroscopy employing stimulated emission, population labelling spectroscopy and mass-selected ion dip spectroscopy with dissociation were briefly described, paying special attention to their characteristics in excitation, detection and application. They were extensively and successfully applied to jet-cooled large molecules and provided us with new useful information on the energy and dynamics of excited molecules.

ISSN:0144-235X    

DOI:10.1080/01442358909353227

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

High-resolution spectroscopic techniques, in particular microwave and infrared diode laser spectroscopy, have been applied to detect, identify and characterize transient molecules such as free radicals and molecular ions in the gas phase through the observation of their rotational, rovibrational and/or rovibronic spectra. Some recent results are discussed in detail. Kinetic spectroscopy has been developed in the infrared and microwave regions to clarify chemical and physical processes involving transient molecules; photochemical and photo-induced reactions are investigated by recording the spectra of intermediate species with this technique in real time. Two applications of spectroscopy of transient molecules are mentioned; one is detection and identification of interstellar molecules and the other is development of a means for diagnosing discharge plasmas such as those employed for making thin films of amorphous silicon.

ISSN:0144-235X    

DOI:10.1080/01442358909353228

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Studies concerning the structures of heterogeneous catalysts and those of adsorbed layers on solid surfaces have rapidly progressed in the last ten years due to the development of a variety of new experimental techniques, including extended X-ray absorption fine structure (EXAFS) spectroscopy. This paper gives a brief review of the experimental facilities in Japan for EXAFS and surface EXAFS (SEXAFS) spectroscopy by use of synchrotron radiation, EXAFS studies on catalysts and in particular those related to the structural changes of catalysts during catalytic reactions, the soft X-ray standing wave (SW) method, structural studies on sulphur adsorption on nickel crystal surfaces by means of SEXAFS and the SW method, and some recent work on the structures of adsorbed layers by other experimental techniques.

ISSN:0144-235X    

DOI:10.1080/01442358909353229

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Accurate determination of the electron-density distribution in transition metal complexes provides important information on the electronic ground state of the d electrons placed in a ligand field. The high-spin and low-spin states can be distinguished unequivocally. The degree of hybridization of the component orbitals can also be determined. If the intensity data are good enough, the wavefunction analysis can be carried out and the orbital coefficients can be obtained by a least squares method. In spite of a very small valence/total electron ratio the asphericity of 4d and 5d electrons in a ligand field can be detected. This is owing to sharp deformation density located outside of the high-density inner core region.

ISSN:0144-235X    

DOI:10.1080/01442358909353230

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor