ESR STUDIES OF THE LOW TEMPERATURE IRRADIATION OF KERATIN AND ITS COMPONENT AMINO ACIDS

Abstract— The photoejection of electrons from the aromatic amino acids at 77°K by 290–340 nm radiation was found to involve both monophotonic and biphotonic processes. However, only monophotonic processes are involved when electrons are photoejected from cystine or cysteine. These electrons prefer to attach themselves to adjacent sulphur groups rather than the dielectric traps in the matrix, so that both anionic and cationic radicals are formed.
In keratin at 77°K, the disulphide anion radicals are produced by both monophotonic and biphotonic mechanisms, indicating that the electrons captured by the disulphides are photo-ejected from the aromatic amino acids. At room temperature the thiyl and aromatic radicals are produced only by monophotonic reactions.     

THE PHOTOLYSIS OF TRYPTOPHAN IN THE PRESENCE OF OXYGEN

Abstract— Quantum yields for the destruction of tryptophan by a single 500 J flash in aqueous solution have been determined over the pH range 1–13 in both air-equilibrated and nitrogen-saturated conditions. When these quantum yields are compared with the quantum yields for radical formation and photoejection of electrons, it is found that there is good agreement only for the nitrogen-saturated case. In air-equilibrated solutions of tryptophan, there is a large disparity between the measured degradation quantum yields and those for photoejection of electrons and radical formation. Oxygen, therefore, is playing a major role in the photochemical decomposition and it is proposed that the major reaction which occurs, under normal atmospheric conditions, is the reaction of the lowest triplet excited state of tryptophan with oxygen.
Preliminary photolysis-product distributions against pH are discussed, and indicate that a total of nine major products are formed in the presence of oxygen.     

青蒿素的二维核磁共振研究

报导了采用二维核磁共振技术研究青蒿素的核磁氢谱和碳谱的谱线归属,以今后为^1^3C中间体的生物转化产物提供鉴定的基础.     

INDOLE N—H BOND FISSION DURING THE PHOTOLYSIS OF TRYPTOPHAN

Abstract— –Analysis of the effect of β-carotene and benzoquinone on the decay curves of flash-induced transients in chlorophyll a solutions in pyridine and isooctane indicates that the formation of quinone radicals proceeds via a ternary complex of solvent, chlorophyll and quinone. It is suggested that the solvent is the source of electrons for this process.     

ChemInform Abstract: Molecular Structure of Gaseous Titanium Tris(tetrahydroborate), Ti(BH4) 3: Experimental Determination by Electron Diffraction and Molecular Orbital Analysis of Some Ti(BH4)3 Derivatives.

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