Very long chain fatty acids: Occurrence and biosynthesis in membrane fractions from etiolated maize coleoptiles

The endoplasmic reticulum from maize coleoptiles elongates stearoyl-CoA more effectively than the plasmalemma-enriched fraction. The alkane and very lo     

Mitochondrial DNA from Podospora anserina. II. Properties of mutant DNA and multimeric circular DNA from senescent cultures.

Summary Mitochondrial (Mt) DNA from mitochondrial mutants of race s Podospora anserina and from senescent cultures of races s and A was examined. In mutants, we observed that fewer full length circles (31 ) were present; instead, smaller circles characteristic for each mutant sudied were found. Eco Rl digestion of these mutant MtDNAs indicated that in certain mutants, although specific fragments were absent, the total molecular weight of the fragments was not much different than wild-type.The properties of senescent MtDNA was strikingly different from either wild-type or mutant Mt DNA. First, a multimeric set of circular DNA was observed for both race s and A, with a monomeric repeat size of 0.89 . These circles ranged in size from 0.89 to greater than 20 ; only one molecule out of some 200 molecules was thought to be of full length (31 ). Density gradient analysis showed that there were two density species: a majority were at the same density as wild-type (1.694 g/cm³) and a second at 1.699 g/cm³. Most of the circular molecules from MtDNA isolated by either total DNA extraction or by extraction of DNA from isolated mitochondria were contained in the heavy DNA fraction. Eco R1 enzymatic digestion indicated that the light DNA had several fragments (amounting to about 23×10⁶ daltons) missing, compared with young, wild-type MtDNA. Heavy senescent MtDNA was not cleaved by Eco R1. Analysis with Hae III restriction endonuclease showed also that light senescent MtDNA was missing certain fragments. Heavy MtDNA of average size 20×10⁶ daltons, yielded only one fragment, 2,500 bp long, by digestion with Hae III restriction endonuclease. Digestion of heavy DNA with Alu I enzyme yielded 10 fragments totalling 2,570 bp. By three criteria, electron-microscopy, Eco R1 and Hae digestion, we conclude that the heavy MtDNA isolated from senescent cultures of Podospora anserina consisted of a monomeric tandemly repeating subunit of about 2,600 bp length.These results on the properties of senescent MtDNA are discussed with regard to the published properties of the rho ^- mutation in the yeast, S. cerevisiae.     

The HLA-D system: At least two loci and four distinct phenotypic traits per haplotype. Introduction to component typing in families and population by primed lymphocyte typing

Using a number of intrafamilial PLTs raised against identical HLA haplotypes it has been possible to construct a model in an informative family defining the HLA-D region as a genetic system. This system consists of at least two regions separated by a recombination between HLA-D and GLO. In relation to the site of recombination, a minimum of one centromeric and three telomeric components can be identified per haplotype.—Fourteen PLTs raised and defined within the family were subsequently tested in a Caucasian population (n=84) and in 13 unrelated, complete families.—It is concluded that the hypothetical model proposed for the HLA-D region as a genetic system of linked loci, coding at the cell surface for associated but distinct components (at least four per haplotype), allows for typing of the components of the HLA-D system of any given haplotype. Serological typing of HLA-D components should, in the near future, provide a more convenient way of establishing component phenotypes than the present use of primed lymphocyte typing reagents. Among the components isolated, some have a high association with the classic alleles defined either by homozygous typing cells or DR serology. Others form the basis of cross-reactivity but their presence does not interfere with standard typing. Others, however, seem by their mere presence to be responsible for false assignments.—The concept of HLA-D as a genetic system clarifies many of the inconsistencies observed with a one-locus system.Research scientists from INSERM.Research Fellow from the Danish Medical Research Council.Central Blood Bank — Marseille     

Parasitic Helminths from Paraguay. I. Sobolevicanthus dlouhyi n.sp. (Cestoda,Hymenoledididae) found in Amazonetta brasiliensis Gmelin

Summary Sobolevicanthus dlouhyi n. sp. is close to S. krabbeella but differs from it firstly by the longer rostellar hooks (83–85 m instead of 56–64 m). The cirrus pouch is shorter in the new species, no longer than the width of the widest proglottis, whereas in S. krabbeella it is twice as long. ac]19810312     

The measurement of the intrinsic alkaline Bohr effect of various human haemoglobins by isoelectric focusing

We have used isoelectric focusing to measure the differences between the pI values of various normal and mutant human haemoglobins when completely deoxygenated and when fully liganded with CO. It was assumed that the ΔpI(deox.–ox.) values might correspond quantitatively to the intrinsic alkaline Bohr effect, as most of the anionic cofactors of the haemoglobin molecule are `stripped' off during the electrophoretic process. In haemoglobins known to exhibit a normal Bohr coefficient (ΔlogP₅₀/ΔpH) in solutions, the ΔpI(deox.–ox.) values are lower the higher their respective pI(ox.) values. This indicates that for any particular haemoglobin the ΔpI(deox.–ox.) value accounts for the difference in surface charges at the pH of its pI value. This was confirmed by measuring, by the direct-titration technique, the difference in pH of deoxy and fully liganded haemoglobin A₀ (α₂β₂) solutions in conditions approximating those of the isoelectric focusing, i.e. at 5°C and very low concentration of KCl. The variation of the ΔpH(deox.–ox.) curve as a function of pH (ox.) was similar to the isoelectric-focusing curve relating the variation of ΔpI(deox.–ox.) versus pI(ox.) in various haemoglobins with Bohr factor identical with that of haemoglobin A₀. In haemoglobin A₀ the ΔpI(deox.–ox.) value is 0.17 pH unit, which corresponds to a difference of 1.20 positive charges between the oxy and deoxy states of the tetrameric haemoglobin. This value compares favourably with the values of the intrinsic Bohr effect estimated in back-titration experiments. The ΔpI(deox.–ox.) values of mutant or chemically modified haemoglobins carrying an abnormality at the N- or C-terminus of the α-chains are decreased by 30% compared with the ΔpI value measured in haemoglobin A₀. When the C-terminus of the β-chains is altered, as in Hb Nancy (α₂β^{Tyr-145→Asp}₂), we observed a 70% decrease in the ΔpI value compared with that measured in haemoglobin A₀. These values are in close agreement with the estimated respective roles of the two major Bohr groups, Val-1α and His-146β, at the origin of the intrinsic alkaline Bohr effect [Kilmartin, Fogg, Luzzana & Rossi-Bernardi (1973) J. Biol. Chem. 248, 7039–7043; Perutz, Kilmartin, Nishikura, Fogg, Butler & Rollema (1980) J. Mol. Biol. 138, 649–670]. In other mutant haemoglobins it is demonstrated also that the ΔpI(deox.–ox.) value may be decreased or even suppressed when the substitution affects residues involved in the stability of the tetramer. These results support the interpretation proposed by Perutz, Kilmartin, Nishikura, Fogg, Butler & Rollema [(1980), J. Mol. Biol. 138, 649–670] for the mechanism of the alkaline Bohr effect, and also indicate that the transition between the two quaternary configurations is a prerequisite for the full expression of the alkaline Bohr effect.     

Conversion of a 24β-ethyl-25-methylene intermediate into poriferasterol by Trebouxia species

Clerosterol-[26-¹⁴C], a 24β-ethyl-25-methylene sterol [(24S)-24-ethylcholesta-5,25-dien-3β-ol], was incorporated into clionasterol and poriferasterol by cultures of the green algae Trebouxia sp. 213/3 and Trebouxia sp. 219/2. Degradation of the labelled poriferasterol showed that the ¹⁴C retained its identity and was not incorporated as a result of metabolism of the clerosterol-[26-¹⁴C] and randomisation of label. These results are consistent with the proposed production, and subsequent reduction, of a 24β-ethyl-25-methylene intermediate in 24β-ethyl sterol biosynthesis in algae of the order Chlorococcales.     

On the conformational dependence of the proton chemical shifts in nucleosides and nucleotides III. Proton chemical shifts of 5′-nucleotides as a function of different conformational parameters

The variation of the chemical shift of the protons of 5′-UMP and 5′-AMP is calculated as a function of χ_CN, ψ and ? torsion angles. The shift of H8 of 5′-AMP and H6 of 5′-UMP is found to be very sensitive to the value of χ_CN. For the anti conformations the shift of these protons is more sensitive to the value of the rotation about CS′-05′ than about C4′-CS′. For the protons of the ribose the calculations show that for the C2′-endo pucker H3′ and H2′ undergo the largest chemical shift variations when ? and ψ vary. The calculated variations are considered in relation with the role of the conformation of the nucleotides in the chemical shift variation between mono and polynucleotides and between the different helical structures of polynucleotides.     

Alcaloides du Strychnos tchibangensis

The structure of a new bisindole alkaloid has been elucidated by chemical correlation and analysis of ¹³C NMR spectra.     

The distribution of hydroxycinnamic acid amides in flowering plants

Hydroxycinnamic acid amides have been identified as the main phenolic constituents in the reproductive organs of a range of flowering plants.