Molecular structure for microbial polysaccharides: conformation of the Klebsiella serotype K9 capsular polysaccharide

Fibre type X-ray diffraction patterns have been obtained from oriented, semicrystalline films prepared from the sodium salt form of the bacterial capsular polysaccharide of Klebsiella serotype K9. The molecule has a pentasaccharide repeating sequence, with four neutral residues in the backbone and a glucoronic acid side chain. A novel feature of the molecule is the incorporation of α-l-rhamnose residues, one 1,2 linked and two 1,3 linked in the backbone. Analysis of the X-ray diffraction results indicate an extended three-fold helical conformation with an axially projected chemical repeat of 1.377 nm. Both left and right handed helices have been examined using linked atom least squares techniques to optimize the stereochemistry while simultaneously meeting the observed helical parameters.     

Material transport within specialised ciliary shafts on Rhabdopleura zooids

Summary The surface of the Rhabdopleura zooid is ciliated. The cilia of the cephalic shield and tentacles have paddle-like swellings of the shaft. These swellings are usually about 0.6–1 m in diameter and most frequently found in the distal 1–2 m of the ciliary shaft. Others are found in other positions along the length of the cilium and it is suggested that at least some of these swellings represent material transport within the cilium.Paddle shaped cilia are probably more efficient than normal cilia in moving water and food particles. If these cilia are involved in the building of the tubular coenecium then their distribution suggests that the tentacles as well as the cephalic shield are actively involved in tube building.I should like to thank the director and staff of the Marine Biological Laboratory, Plymouth, for collecting the material and the generous loan of facilities during the preparation of the material. Mr. R. Moss provided skillful technical and photographic assistance     

Inheritance of resistance to neonatal E. coli diarrhoea in the pig: examination of the genetic system

Summary Evidence is presented that a dominant allele, S, is expressed as a receptor for K88 on the brushborder surface of the pig intestinal cell. The homozygous recessive (ss) lacks this receptor. The receptor enables K88 — positive coliforms to adhere to the gut of the piglet which they must do if they are to cause neonatal diarrhoea. The homozygous recessive is thus a disease resistant animal.A possible reason for the persistence of the dominant (susceptible) gene is given.     

Bicyclo[3,2,1]octanoid,neolignans from Aniba simulans

Six bicyclo[3,2,1]octanoid neolignans, isolated from the benzene extract of Aniba simulans Allen (Lauraceae) trunk wood, are shown to derive from two basic structures: 1-allyl-8-hydroxy-6-(3′-methoxy-4′,5′-methylenedioxyphenyl)-7-methyl-3-oxobicyclo[3,2,1]octane, substituted by 4-hydroxy, 4-hydroxy-5-methoxy, 4-methoxy or 4,5-dimethoxy groups; and 1-allyl-8-hydroxy-6-(3′-methoxy-4′,5′-methylenedioxyphenyl)-7-methyl-4-oxobicyclo[3,2,1]oct-2-ene, substituted by 3-hydroxy or 3-hydroxy-5-methoxy groups. The structural proposals are based on spectral data, interconversions synthesis of a derivative from the known (2R,3S,3aS)-3a-allyl-5-methoxy-2-(3′-methoxy,4′,5′-methylenedioxyphenyl)-3-methyl-2,3,3a,6-tetrahydro-6-oxobenzofuran.     

Ein Endemit Zyperns:Asperula cypria (Rubiaceae) und seine Verwandtschaft

Galium suberosum Sibth. etSm. belongs toAsperula sect.Thliphthisa; the taxonomic transfer and a new name are therefore necessary:Asperula cypria Ehrend. is endemic on the isle of Cyprus. Its closest affinities are withA. antalyensis Ehrend. in S.W. Anatolia.

     

Orientation of the protonmotive force in membrane vesicles of escherichia coli

Membrane vesicles of Escherichia coli can be produced by 2 different methods: lysis of intact cells by passage through a French pressure cell or by osmotic rupturing of spheroplasts. The membrane of vesicles produced by the former method is everted relative to the orientation of the inner membrane in vivo. Using NADH, D-lactate, reduced phenazine methosulfate, or ATP these vesicles produce protonmotive forces, acid and positive inside, as determined using flow dialysis to measured the distribution of the weak base methylamine and the lipophilic anion thiocyanate. The vesicles accumulate calcium using the same energy sources, most likely by a calcium/proton antiport. Calcium accumulation, therefore, is presumably indicative of a proton gradient, acid inside. The latter type of vesicle, on the other hand, exhibits D-lactate-dependent proline transport but does not accumulate calcium with D-lactate as an energy source. NADH oxidation or ATP hydrolysis, however, will drive the transport of calcium but not proline in these vesicles. Oxidation of NADH or hydrolysis of ATP simultaneous with oxidation of D-lactate does not result in either calcium or proline transport. These results suggest that the vesicles are a patchwork or mosiac, in which certain enzyme complexes have an orientation opposite to that found in vivo, resulting in the formation of electrochemical proton gradients with an orientation opposite to that found in the intact cell. Other complexes retain their original orientation, making it possible to set up simultaneous proton fluxes in both directions, causing an apparent uncoupling of energy-linked processes. That the vesicles are capable of generating protonmotive forces of the opposite polarity was demonstrated by measurements of the distribution of acetate and methylamine (to measure the ΔpH) and thiocyanate (to measure the Δψ).     

Metabolism of benzo[a]pyrene in cell suspension cultures of parsley (Petroselinum hortense,Hoffm.) and soybean (Glycine max L.)

Cell suspension cultures of parsley and soybean were incubated for 38 h with ¹⁴C-labeled benzo[a]pyrene; autoclaved cultures were used as controls. Metabolites were isolated by a sequential extraction procedure and further studied by chromatography or by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The soluble metabolites amounted to 1–2.2% in the case of parsley cells, and 19–28% in the case of soybean cells. These metabolites varied in polarity, some being soluble in organic solvent or aqueous buffer while other metabolite fractions were soluble only in hot aqueous sodium dodecylsulphate. In addition, a significant amount of an insoluble metabolite fraction was isolated from the culture fluid as well as the cellular material of soybean suspension cultures.Abbreviations BP benzo[a]pyrene - SDS sodium dodecyl sulfate - TCA trichloroacetic acid     

Effector cells which mediate antibody-dependent cell-mediated cytotoxicity. II. Ontogeny of effector activity in murine spleen.

The specificity of T cells for syngeneic target cells is directed to both antigens and products of the major histocompatibility complex (MHC) on the target cell surface. This dual requirement is best accounted for by the altered-self hypothesis, which implies that the MHC products on a cell's surface are able to form complexes with many other proteins on the surface of the same cell. To account for the ability of MHC products to bind so many different cell surface antigens we propose that interactions in general among macromolecules on the surface of a membrane may be dramatically enhanced by a purely physical effect. This effect derives from the confinement of membrane macromolecules to an effective volume which is the product of membrane surface area times d, the distance over which the center of mass of the molecules can move in a vertical direction (perpendicular to the membrane surface). Because d is very small the effective concentrations of surface molecules are extremely high and their interactions are correspondingly enhanced.     

The use of a partition locus to increase stability of tryptophan-operon-bearing plasmids in Escherichia coli

The stability of different derivatives of plasmid vectors pBR322 and pACYC184 carrying the tryptophan operon of Escherichia coli was monitored in various media. It was found that in the absence of any special selective pressure, all plasmids were lost from the culture. The stability varied depending both on the orientation of the inserted tryptophan fragment and the growth media used. The pBR322::trp+ plasmids were lost at an average frequency of 0.3 to 0.8% per cell generation, while the pACYC184::trp+ plasmid was lost at a rate higher than 5%. In all cases the whole plasmid was lost at a rate higher than 5%. In all cases the whole plasmid was lost, indicating a high stability of the plasmid::cloned DNA as such. To increase the stability of the cloning vectors, the partition locus of plasmid pSC101 was added to both the pBR322::trp+ and pACYC184::trp+ plasmids. The addition of this gene increased the replicon stability at least 3- to 10-fold, with the pBR322::trp+-par+ plasmids being the most stable. Also in this case, the stability was dependent on the plasmid type and on the growth medium. In no case was there a discoordinate loss of the antibiotic-resistance and tryptophan genes from the vectors.