Assignment of imino proton spectra of yeast phenylalanine transfer ribonucleic acid

Yeast tRNAPhe has been studied by using proton NMR and nuclear Overhauser effect (NOE) with deuterium substitution. Direct NOE evidence is presented for assignment of imino resonances of 23 of 27 base pairs in this tRNA. Other indirect evidence is presented for tentative assignment of four other base pairs. Almost total assignment also has been made of the important noninternally bonded imino protons and tertiary interactions (however, G18-psi 55 remains unassigned). The most surprising result has been identification of GC11 at -13.68 ppm; this is the first time a GC base pair has been identified so far downfield. This peak (GC11) is also identified as the resonance of the unique imino proton that exchanges in a time of more than 1 day, as previously described. These identifications of imino proton resonances made it possible to reinterpret the proton solvent exchange rate data previously published on this tRNA and understand them better. The assignments of resonances should pave the way for more detailed solution study of this tRNA and its interaction with biologically relevant molecules.     

Glycerol catabolite regulation of d-cycloserine production in Streptomyces garyphalus

A fluorescent pigment was isolated from the culture fluid of Methanobacterium thermoautotrophicum strain H. This pigment was shown to be 7,8-didemethyl-8-hydroxy-5-deazariboflavin by various spectroscopic and chromatographic techniques. This compound was previously described as the FO acid hydrolysis fragment of coenzyme F₄₂₀. On the basis of the time of appearance of the pigment in the course of fermentation, it is suggested that this substance may be an over-produced biosynthetic precursor of F₄₂₀.     

Chromosome Transfer and Recombinant Formation with Deoxyribonucleic Acid Temperature-Sensitive Strains of Escherichia coli

Haploid recombinant yield is reduced in matings conducted at 42.5 C between deoxyribonucleic acid (DNA) temperature-sensitive [dna⁻(TS)] recipients unable to synthesize DNA at 42.5 C and any of the three major donor types (Hfr, F⁺, F′) of Escherichia coli. No such reduction is observed in matings conducted at 42.5 C when the dna⁻(TS) mutation is in the donor parent. Evidence is presented which indicates that chromosome transfer from donors to recipients unable to replicate DNA at 42.5 C during vegetative growth occurs at normal frequencies when the mating is conducted at 42.5 C. It is concluded that some stage in haploid recombinant formation is adversely affected in dna⁻(TS) recipients mated at the temperature restrictive for DNA synthesis.     

Regulation of Substrate Uptake in Nocardia erythropolis

The regulation of uptake of glucose (GLU), glycerol (GLY), mannitol (MTL), and succinate (SUC) has been examined in Nocardia erythropolis 305. The apparent K_m values of the uptake activities of cells subcultured in a medium with the corresponding substrate as the sole carbon source were 205, 48, 8.7, and 36 μM for GLU, GLY, MTL, and SUC, respectively. GLU and GLY uptake activities were constitutive, although there was evidence for an additional inducible component in GLY uptake. Moreover, MTL and SUC uptake activities were inducible. MTL uptake activity was markedly induced by cultivation in MTL medium and partially induced by growth in GLU medium, whereas SUC uptake was induced only by cultivation in SUC medium. SUC added to MTL medium partially repressed the formation of, or inhibited the activity of, MTL uptake. When not induced, uptake of MTL and SUC was proportional to the substrate concentration. The induced uptake of MTL and SUC and the constitutive uptake of GLU were energy dependent and carrier mediated. Uptake of GLY, constitutively or when induced, was also carrier mediated.     

Isolation of two pure polysaccharides from the hemicellulose of slash pine (Pinus elliottii)

Two pure, acidic polysaccharides have been isolated from the hemicellulose of slash pine in yields of 1–2% and 4–5%. Their properties are compared, and the structure of one of them has been investigated by methylation analysis. The results indicate that the glycan is a β-D-(1→4)-linked xylan chain with many branch points. 4-O-Methyl-D-glucopyranosyluronic acid, L-arabinofuranose, and D-xylopyranose residues occur as non-reducing end groups. The uronic acid occurs as single-unit attachments to the main chain. Some of the D-xylose residues in the polysaccharide are doubly branched. The total hemicellulose components of the wood probably represent a complex mixture of chemical types, from which the two pure fractions described above may be separated fortuitously by careful, fractional precipitation.