31P nuclear magnetic resonance spectroscopy of lipopolysaccharides from pseudomonas aeruginosa

Intact lipopolysaccharide antigens isolated from seven different immunotypes of Pseudomonas aeruginosa have been examined by ³¹P-NMR spectroscopy. These macromolecular complexes contain phosphorus covalently attached to the carbohydrate residues present in the lipid A moiety and the ‘core’ oligosaccharide region. The spectral signals for various ortho- and pyro-phosphoric esters were observed. All phosphate groups appeared to be mono-esterified. Certain shifts characteristic for phosphate diester groups, observed in lipopolysaccharide complexes from other Gram-negative bacteria, were absent. Furthermore, no evidence was found to indicate that phosphate groups are involved in the covalent linkage of individual lipopolysaccharide complexes to form dimers or trimers.     

Dependence on lipid structure of the coil-to-helix transition of bovine myelin basic protein

In aqueous solution bovine myelin basic protein has a close-to-random coil structure that is partially transformed to helix on interaction with lipids. Circular dichroism spectra have been used to follow this conformational transition which, with phospholipids, decreases in the order phosphatidylglycerol, phosphatidic acid approximately equal to phospholipids, decreases in the order phosphatidylethanolamine. There appears to be a strong correlation between the extent of alpha-helix formation and the degree of penetration of the hydrophobic region of the bilayer, as assessed by other methods. Cholesterol mixed in bilayers with phosphatidylserine has little effect on the protein secondary structure. Although basic protein binds strongly to cerebroside and to cerebroside sulphate, two of the other major myelin lipids, the intrinsic chirality of these lipids precludes assessment of their effect on the protein conformation. No significant changes in the circular dichroism spectra accompany the protein association with either of the zwitterionic bilayer-forming lipids, phosphatidylethanolamine and phosphatidylcholine. This seems to exclude extensive penetration into bilayers of these lipids and hence to exclude appreciable hydrophobic interactions; on the other hand, it is argued that little evidence exists for ionic attractions to these lipids. The optical activity of peptides derived from the basic protein by cleavage at the 42-43 and 88-89 peptides bonds (with cathepsin D) and at the 115-116 bond (with a skatole derivative) has also been measured in an attempt to locate the helix-forming regions within the primary structure.     

Stereospecific activity of 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine and comparison of analogs in the degranulation of platelets and neutrophils

1-O-Hexadecyl-2-O-acetyl-$\text{sn}$-glycero-3-phosphocholine (platelet activating factor) stimulated the degranulation of rabbit platelets and human neutrophils, whereas the enantiomer, 3-O-hexadecyl-2-O-acetyl-$\text{sn}$-glycero-1-phosphocholine, was inactive. The analogs compared had the following relative potencies in degranulating platelets and neutrophils: 1-O-hexadecyl-2-O-acetyl-$\text{sn}$-glycero-3-phosphocholine > 1-O-hexadecyl-2-O-ethyl-$\text{sn}$-glycero-3-phosphocholine >$\text{rac}$-1-O-octadecyl-2-O-ethylglycero-3-phosphocholine = 1-O-hexadecyl-2-O-methyl-$\text{sn}$-glycero-3-phosphocholine >$\text{rac}$-1-O-dodecyl-2-O-ethyl-glycero-3-phosphocholine. The deacetylated compound, 1-O-hexadecyl-2-lyso-$\text{sn}$-glycero-3-phosphocholine, and 1-O-hexadecyl-2,2-dimethylpropanediol-3-phosphocholine were inactive. The active analogs selectively desensitized the response to each other in the neutrophils. It is suggested that these compounds may activate cells through interaction with a stereospecific receptor.     

Mutant cell lines resistant to azetidine carboxylic acid: Quantitative and qualitative differences in pyrroline-5-carboxylate synthase activity

Mutant Chinese hamster lung fibroblasts were selected that are resistant to the proline analog L-azetidine-2-carboxylic acid. Resistance in the two mutant cell lines is associated with two distinct alterations in pyrroline-5-carboxylate synthase, the enzyme that catalyzes the proline biosynthetic step leading from glutamic acid to pyrroline-5-carboxylate. In one mutant cell line, pyrroline-5-carboxylate synthase specific activity is increased 30-fold over the level in control cells. In the other mutant line, pyrroline-5-carboxylate synthase activity is not increased, but the enzyme has become insensitive to inhibition by ornithine and proline.     

Effect of amphotericin B on membranes: a spin probe study

The effect of the polyene antibiotic amphotericin B on the electron paramagnetic resonance spectra of lipid probes intercalated in model membranes was examined. When the antibiotic was added to the aqueous phase, no spectral effects occurred. However, when the antibiotic was incorporated during membrane preparation, changes in spectral parameters suggested the appearance of a new phase. The spectral changes do not necessarily corroborate the pore models proposed previously for amphotericin B in membranes. With a spin probe that partitions between water and membrane, an interaction between the amphotericin B and probe is observed. This interaction does not occur in the membrane, but in the aqueous phase, between the probe and the aggregated antibiotic. Some of the equilibria involving the antibiotic appear to be achieved slowly.     

Phosphorus-31 nuclear magnetic resonance of phosphoenzymes of sodium- and potassium-activated and of calcium-activated adenosinetriphosphatase

Prior studies identified phosphoenzyme intermediates in the turnover of sodium- and potassium-activated adenosinetriphosphatase [(Na,K)ATPase] from several sources and of the calcium-activated adenosinetriphosphatase [(Ca)-ATPase] of skeletal muscle sarcoplasmic reticulum. In both cases, the transphosphorylation is to a beta-aspartyl carboxyl group at the active site. We now report observation of a K+-sensitive phosphorylated intermediate of purified (Na,-K)ATPase from the salt gland of the duck using high-field 31P nuclear magnetic resonance. Addition of ATP to a suspension of this enzyme in the presence of Mg2+ and Na+ produced a resonance at about +17 ppm relative to 85% phosphoric acid. Addition of inorganic phosphate and Mg2+ to (Na,K)ATPase also produced a resonance at about +17 ppm which was enhanced in the presence of a saturating concentration of the inhibitor, ouabain; again, addition of K+ made this resonance disappear. These findings are consistent with earlier kinetic characterization of an acid-stable (Na,K)ATPase phosphoenzyme intermediate by 32P-labeled phosphate incorporation into a denatured precipitate of the enzyme. We attribute the +17-ppm resonance to formation of an acyl phosphate at an aspartyl residue of the catalytic site of (Na,K)ATPase. This is supported by our finding of a similar resonance at +17 ppm after phosphorylation of another membrane-bound cation transport enzyme, sarcoplasmic reticulum (Ca)ATPase, as well as by a similar resonance at about +17 ppm after phosphorylation of the model dipeptide L-seryl-L-aspartate.     

Primary and secondary autologous mixed-lymphocyte interactions in mice occur via antigens encoded by genes in the I region of the major histocompatibility complex

The antigens stimulating the autologous mixed-lymphocyte reactions (AMLR) were studied in experiments employing specific blocking antisera and through panels of secondary stimulating cells differing in the MHC. Antisera directed to the entire I region, I-A, I-EC, or A?Eα were all effective in blocking the primary AMLR. A principal role for those determinants encoded in I-A was indicated by secondary stimulation experiments. In secondary cultures, I-EC encoded determinants generated weaker responses in the absence of I-A homology.     

Studies on glycosaminoglycans of regenerating rabbit ear cartilage

Cartilage regeneration in the adult rabbit ear was examined with respect to glycosaminoglycan (GAG) synthesis at various stages of the regeneration process. Increased hyaluronic acid and chondroitin sulfate synthesis was first seen 31 days after wounding, when a metachromatic cartilage matrix could be distinguished from blastemal cells. Analysis of cartilage and the overlying skin separately showed that 90% of the labeled chondroitin sulfate was found in the cartilage being regenerated. DEAE-cellulose chromatography of GAG preparations from 35-day regenerating cartilages showed hyaluronic acid and chondroitin sulfate peaks eluting in the same position as those isolated from normal cartilages. The identity of the hyaluronic acid and chondroitin sulfate peaks was confirmed by their susceptibility to Streptomyces hyaluronidase and chondroitinase ABC, respectively. Although the degree of sulfation in normal and regenerated cartilages was similar, the ratio of chondroitin 6-sulfate to chondroitin 4-sulfate was increased in regenerated cartilages. GAG preparations from unlabeled cartilages were digested with chondroitinase ABC and the disaccharide digestive products were identified and quantitiated. Normal cartilage had a $\text{Δ}\text{Di-6S}\text{Δ}\text{Di-4S}$ ratio of 0.27; the same ratio for the regenerated cartilage was 1.58.     

Variation within teosinte. I. Numerical analysis of morphological data

Principal components analysis of 27 morphological characters for 18 accessions of teosinte and 3 accessions of maize separated teosinte into 6 phenetic groups which showed broad agreement with previous taxonomic groupings. Tests for regression suggested significant linear relationships with altitude; teosintes from higher elevations are generally more maize-like for a combination of characters. Introgression from maize may have blurred racial identities within teosinte, but variation among current teosinte accessions cannot be satisfactorily explained solely on the basis of known maize introgression. It appears instead that racial differentiation in teosinte was well established by the time of the domestication of maize. While current racial classification of teosinte is quite useful, it does not adequately reflect the amount of genetic variation, nor does it accurately portray many of the relationships within teosinte.     

Osage orange (Maclura pomifera): History and economic uses

Osage orange, a tree native to Texas, Oklahoma, and Arkansas, was planted widely in the United States as a living fence from 1850–1875. It has naturalized over much of its planted range and is an early successional species. Economically the tree has had a wide number of uses including for bows, yellow dye, and building materials. It is used for fence posts and is a potential source for a proteolytic enzyme. Its taxonomy, anatomy, morphology, chemical constitutents, medicinal uses, and toxicity are discussed in this paper and related to its economic importance.