Oxidation of nitroxide radicals by the reaction of hemoglobin with hydrogen peroxide

The ESR signal of 4-hydroxy-1-oxyl-2,2,6,6-tetramethylpiperidine in hemoglobin solution decreased drastically by the addition of hydrogen peroxide. The results of ion-exchange chromatography and sodium tetraphenylborate on the reaction solution showed an oxidation of the nitroxide radical to cation form. On the basis of the comparison of thin layer-chromatogram with the reaction products of the nitroxide radicals with HCl or Br2, the formation of 4-hydroxy-1-oxo-2,2,6,6- tetramethylpiperidinium cation was demonstrated. This result was supported by the 13C NMR measurement.     

Control of K+ conductance by cholecystokinin and Ca2+ in single pancreatic acinar cells studied by the patch-clamp technique

Summary The effect of cholecystokinin (CCK) and internal Ca²⁺ on outward K⁺ current in isolated pig pancreatic acinar cells has been investigated using the patch-clamp method for whole-cell current recording under voltage-clamp conditions. CCK (2 × 10^–10 M) applied to the bath evoked a marked increase in the outward K⁺ current associated with depolarizing voltage steps, and this effect was fully reversible and acutely dependent on the presence of external Ca²⁺. When strongly buffered Ca²⁺-EGTA solutions were used inside the cells CCK failed to evoke an effect. Increasing the internal Ca²⁺ concentration ([Ca²⁺] _i ) from 5 × 10^–10 M to 10^–7 and 5 × 10^–7 M mimicked the effect of CCK. It would appear therefore that CCK controls K⁺ conductance in the acinar cells via changes in the internal free ionized Ca²⁺ concentration.     

Characterization and immunochemistry of pyruvate dehydrogenase complex of Ascaris muscle

Pyruvate dehydrogenase complex and lipoamide dehydrogenase were purified from muscle of Ascaris lumbricoides var. suum which contains relatively a large amount of the complex. Molecular weights of three constituent enzymes of Ascaris pyruvate dehydrogenase complex were as follows; alpha- and beta-subunits of pyruvate dehydrogenase were 42,000 and 37,000, respectively, lipoate acetyltransferase was 76,000 and lipoamide dehydrogenase was 56,000. Furthermore, two unknown polypeptides having molecular weight of 46,000 and 41,000 were detected. Anti-Ascaris lipoamide dehydrogenase antibody precipitated three constituent enzymes and two unknown polypeptides, suggesting that lipoamide dehydrogenase not only binds tightly to complex, but also two unknown polypeptides bind tightly to complex.     

13C- and 1H-nmr evidence for all-cis peptide bonds in cyclic tetrapeptide cyclo(L-Pro-Sar)2

Conformations of the cyclic tetrapeptide cyclo(L -Pro-Sar)₂ in solution were studied by ¹H- and ¹³C-nmr spectrometry and model building. The nmr data provide definite evidence that this cyclic peptide exists chiefly in two conformations, namely, a C₂-symmetric conformation and an asymmetric structure. The former was demonstrated to be predominant in polar solvents (100% in Me₂SO-d₆). This structure contains all cis-peptide bond linkages and all trans′ Pro C^α?CO bonds. It represents the first cyclic tetrapeptide in which all four peptide bonds have been found in the cis-conformation. As the polarity of the solvent decreases, the population of C₂-symmetric conformers decreases (88% in CD₃CN and 65% in CDCl₃). At the same time, a minor asymmetric conformer, characterized by cis-cis-cis-trans peptide bond sequences (two cis Sar-Pro bonds, one cis Pro-Sar bond, and one trans Pro-Sar bond), is seen to increase (9% in CD₃CN and 30% in CDCl₃). A proposed predominant conformation in solution for cyclo(L -Pro-Sar)₂ was compared with a crystal structure, as reported in an accompanying paper. Both structures show striking overall similarities.     

Growth Regulation in Dwarf Barley Coleoptiles by the Minor Cell Wall Components, Galactose and Mannose

Sugar compositions of cell walls of dark-grown coleoptiles from12 barley strains, 11 of which were coleoptilar semi-dwarf strains,were analyzed on days 2 and 3 after germination. Major wallcomponents of the 12 strains were arabinose, xylose, and glucosein hemicellulose and cellulose; minor components were galactoseand mannose. The sugar content of each wall component per unit length wasnot correlated to any growth parameters calculated from a logisticequation simulating coleoptile growth, but the relative contentsof galactose and mannose in relation to the total wall sugarcontent was correlated to the growth rate on day 3 and the growthcontinuing period. These facts suggest that growth of these12 barley strains in the late growth stage is regulated by theminor wall components, galactose and mannose. ¹ Dedicated to the late Professor Joji Ashida. (Received October 12, 1982; Accepted January 12, 1983)     

Auxin-Induced Changes in the Cell Wall Xyloglucans: Effects of Auxin on the Two Different Subtractions of Xyloglucans in the Epicotyl Cell Wall of Vigna angularis

In order to study the IAA-induced modifications of the cellwall of azuki bean (Vigna angularis Ohwi et Ohashi cv. Takara)epicotyl segments, the xyloglucans were subfractionated intotwo components, i.e., 4K-U and 24K xyloglucans, which were obtainedby extraction with 4% KOH solution containing 8 M urea and 24%KOH solution, respectively. The weight-average molecular weightsof 4K-U and 24K xyloglucans were estimated to be 40 x 10⁴ and106 x 10⁴, respectively. Complete acid hydrolysis of 4K-U and24K xyloglucans gave glucose, xylose, galactose and fucose inmole % 48.3 : 33.5 : 13.8 : 4.4 and 45.3 : 30.9 : 19.6 : 4.3,respectively. Treatment of epicotyl segments with IAA (0.1 mM) caused a decreasein the amount of 24K xyloglucans and an increase in 4K-U xyloglucans,whereas the total amount of the two xyloglucans remained constant.Furthermore, IAA treatment caused a decrease in the molecularweight of 24K xyloglucans from 106 x 10⁴ to 78 x 10⁴ withoutcausing changes in their sugar compositions. With 4K-U xyloglucans,IAA caused an increase in the mole % of xylose and a decreasein the mole % of galactose and fucose. ¹ This paper is dedicated to the late Professor Joji Ashida. (Received November 26, 1982; Accepted February 7, 1983)     

Raman diagnosis of nucleic acid structure: sugar-puckering and glycosidic conformation in the guanosine moiety.

Observations of Raman spectra of various nucleic acids indicate that the guanine ring breathing frequency is sensitive to the internal rotation angle around the glycosidic bond and to the conformation of the five-membered ring of the ribose residue that is directly connected with the guanine residue in question. It is found that 682 cm-1 for C2'-endo-anti, at 665 cm-1 for C3'-endo-anti, and at 625 cm-1 for C3'-endo-syn. A DNA octamer d(GpGpApApTpTpCpC) shows, in its aqueous solution, a broad Raman band at 680 cm-1 with a tail at 670 cm-1. This fact suggests that the guanosine residues in this oligomer take primarily C2'-endo-anti conformation but an appreciable amount of fluctuation of the ribose ring structure towards C3'-endo is involved.     

Solaniol, a Toxic Metabolite of Fusarium solani

Fusarium solani M-1-1 isolated from moldy bean hulls produces T-2 toxin, diacetoxyscirpenol, and a new toxic trichothecene, solaniol, in Czapek-Dox-peptone medium.     

Small-angle X-ray scattering of pig thyroglobulin in solution (Short Communication)

Small-angle X-ray scattering measurements on native pig thyroglobulin in phosphate buffer, pH6.9, yield a radius of gyration of 6.4nm (64Å), a particle volume of approx. 1.5×10³nm³ (1.5×10⁶ų), an axial ratio of 2.2:1 (assuming an ellipsoidal shape), and a solvation of 0.63g of solvent/g of protein.