No abstract

An important specific rearrangement process in oxygenated organic compounds has been found to involve the formation of carbon monoxide. A combination of accurate mass measurement and metastable peak analysis has provided in many cases unequivocal information on the course of the fragmentation processes involved. A fairly detailed study of the fragmentation of anthraquinone has shown that fresh bonds are formed to produce the ionized forms of fluorenone and o-diphenylene; in the case of hydroxy derivatives of anthraquinone the ion CnH,+ appears to have high stability. Other compounds, mainly aromatic ethers and ketones, are discussed in a similar way and in a few cases suggestions are made regarding the nature of the transition states involved in these s ecific rearrangements. Analogously, HCN, NO and other groups are eliminated from nitrogen-containing compounds suct as the nitroanilines. The theoretical implications of such specific low energy processes are considered briefly, with reference to the quasi-equilibrium theory of mass spectra.

Inhibition of the growth of Neurospora crassa in still culture was detected at 0.05% and was complete at a level of 0.2% phenethyl alcohol (PEA). Benzyl alcohol was less inhibitory, and 3-phenyl-1-propanol and phenol were more inhibitory, than PEA; benzylamine and phenethylamine were less inhibitory than the analogous hydroxylated compounds. Inhibition by PEA was not reversed by synthetic mixtures of purines and pyrimidines or vitamins, or by casein digests, yeast extract, or nutrient broth. The germination of conidia was inhibited by PEA, but after an exposure of 8.5 hr no loss of viability was observed. The addition of PEA to growing shake cultures caused a simultaneous inhibition of growth and of the syntheses of ribonucleic and deoxyribonucleic acids and protein; the relationships of these compounds to mycelial dry weight and to one another were constant in growing mycelia, and PEA did not significantly affect these relationships. PEA partially inhibited the uptake of glucose, but severely restricted the accumulation of L-leucine, L-tryptophan, or a-aminoisobutyric acid in germinated conidia. The efflux of a-aminoisobutyric acid from germinated conidia was somewhat enhanced by PEA, but this effect was not so pronounced as the (complete) inhibition of a-aminoisobutyric acid accumulation by PEA. It is suggested that PEA affects primarily the initial influx of a-aminoisobutyric acid rather than the subsequent retention of a-aminoisobutyric acid.

No abstract

Neurospora crassa resistant to 4-methyltryptophan (4-MT) were isolated from populations of conidia exposed to ultraviolet light. In genetic crosses, 4-MT resistance behaved as a single-gene difference. Resistance to 4-MT could not be attributed to a relaxation of control of the formation or the activity of the enzymes of tryptophan biosynthesis. Growth studies involving tryptophan auxotrophs carrying the aberrant mt gene and uptake studies with normal and 4-MT-resistant strains showed that 4-MT resistance could be attributed to an inability of 4-MT-resistant strains to take up tryptophan and its methyl analogues. The mt gene is not specific for tryptophan; strains resistant to 4-MT are also resistant to ethionine, and they have a markedly reduced ability to take up serine, leucine, and a-aminoisobutyric acid. No difference was observed between strains carrying either mt allele in their ability to take up glucose; also, the uptake of anthranilic acid or of indole was not sufficiently impaired by the aberrant mt gene to prevent these tryptophan precursors from satisfying the nutritional requirement of certain tryptophan auxotrophs. The role of the mt gene in determining the permeability of N. crassa to amino acids is discussed.