Degradation of 2-deoxyaldoses by alkaline hydrogen peroxide

Reaction of 2-deoxy-D-arabino-hexose, 2-deoxy-D-lyxo-hexose, and 2-deoxy-D-erythro-pentose with alkaline hydrogen peroxide in the presence of magnesium hydroxide afforded the corresponding 2-deoxyaldonic acid, the 1,4-lactone, and the 1-O-formyl derivative of the next lower alditol. The 2-deoxyaldonic acids were separated in 60–80% yields, as new, crystalline lithium salts. The 1,4-lactones were obtained under conditions that precluded intermidiate formation of the free acids: presumably, the reaction proceeded by way of an intermediate, furanosyl hydroperoxide, which was converted into the lactone by elimination of water. With an excess of alkaline hydrogen peroxide, in the absence of magnesium hydroxide, the substrates were degraded to formic acid, with concurrent decomposition of hydrogen peroxide. It is shown that decomposition of hydrogen peroxide is catalyzed by hydroperoxide anion, and that it takes place by both a chain, and a non-chain, process. The decomposition reactions afford an abundant source of hydroxyl radical capable of oxidizing a wide variety of compounds.     

Cantharidin: Novel effects on plants

Cantharidin, the active ingredient of Spanish fly, is a potentplant growth regulator. It is phytotoxic at certain concentrations,inhibits growth at other concentrations, and causes headingup response in some crops. Beans are totally immune to the actionof cantharidin. It may be a selective herbicide and a selectivemitotic inhibitor. (Received August 28, 1974; )     

Sedimentation and intrinsic viscosity behavior of PM2 bacteriophage DNA in alkaline solution

The sedimentation coefficient and intrinsic viscosity of nicked and closed circular PM2 bacteriophage DNA have been measured as a function of pH in the alkaline region. A gradual increase in the sidimentation coefficient, and a corresponding decrease in the intrinsic viscosity, are observed for the superhelical (closed) circle in the pH region from 10.5 to about 10.9. This has been tentatively interpreted in terms of the known dependence of sedimentation coefficient upon the number of superhelical turns. At slightly higher pH values, the curve passes through the minimum (sedimentation coefficient) and maximum (intrinsic viscosity) expected when the superhelical turns present at neutral pH are unwound by partial alkaline denaturation. Sedimentation studies of the relaxed (nicked) circular species have revealed the existence of DNA forms in the pH region from 11.27 to 11.37 which sediment considerably faster than the closed circle in the same pH region. These have been identified as partially denatured nicked circles, in which varying fractions of the duplex structure have undergone alkaline denaturation, but strand separation has not yet occurred. Varying fractions of a slower species, either undenatured or completely denatured nicked circles, are also observed in some of these experiments. A corresponding result is observed in the intrinsic viscosity vs. pH curve. When nicked circular PM2 DNA is exposed to various alkaline pH's, rapidly neutralized, and sedimented at neutral pH, the expected sharp transition from native to denatured (strand-separated) molecules is seen. However, a very narrow pH range is noted in which native and denatured forms coexist in a single experiment. The above experiments carried out upon the closed form also reveal a narrow pH range in which the bulk of the transition from native closed circles to the collapsed cyclic coil takes place, in acccord with an earlier study on a different DNA. This transition is shown never to be completely effected, however, as there is a fraction (7–8%)of the closed circles which renature to the native form, regardless of the alkaline pH employed. This same phenomenon was not observed in the case of artificially closed λb₂b₅c DNA circles. Possible explanations for some of the above results are discussed.     

Beam theory for rapid strain estimation in the mouse tibia compression model

Biomechanics and Modeling in Mechanobiology - The mouse tibia compression model is a leading model for studying bone’s mechanoadaptive response to load. In studying this mechanoadaptive...     

H3-cerebroside sulfate re-distribution induced by cation,opiate or phosphatidyl serine

Transfer of H³-cerebroside sulfate (CS) from aqueous phase to nonaqueous phases (heptane interface) was studied in the absence and presence of opiates, cations and phosphatidylserine. The degree of H³-CS re-distribution was dependent on the concentration of these substances used. The concentration of an opiate agonist (GPA-1657) required to increase H³-CS by 50% in the nonaqueous phase was much lower than that of its corresponding antagonist (GPA-2163) and the value for calcium was 100 times less than sodium. Opiate antagonist (GPA-2163) and phosphatidylserine inhibited the agonist induced re-distribution of H³-CS. Thus, the data seem to indicate that the distribution of H³-CS between these two phases was determined by hydrophobic-hydropholic balance of H³-CS and this balance was dependent on the counter ion pairing with CS. This finding is consistent with our previous observation that opiate agonist-CS complex was more hydrophobic than free CS of the CS-complex formed with opiate antagonist.