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[en] Pulse and continuous wave NMR measurements are reported for protons in hydrous melts of calcium nitrate at temperatures between -4 and 120⁰C. Although measured in different temperature ranges, spin-lattice (T₁) and spin-spin (T₂) relaxation times appear to be nearly equal to each other and proportional to the self-diffusion coefficients of solute metal cations such as Cd²⁺. At temperatures near 50⁰C, mean Arrhenius coefficients Δ H/sub T₁/ (kcal/mol) are 7.9, 7.3, and 4.8, respectively, for melts containing 2.8, 4.0, and 8.0 moles of water per mole of calcium nitrate, compared to 4.6 kcal/mol for pure water. Temperature dependence of T₁ and T₂ in Ca(NO₃)₂-2.8 H₂O between -4 and 120⁰C are non-Arrhenius and can be represented by a Fulcher-type equation with a ''zero mobility temperature'' (T₀) of 225⁰K, close to the value of T₀ for solute diffusion, electrical conductance and viscosity. Resolution of the relaxation rates into correlation times for intramolecular (rotational) and intermolecular (translational) diffusional motion is discussed in terms of the Bloembergen-Purcell-Pound and more recent models for dipolar relaxation

[en] The authors have developed a method for determination of the specific activity of radio-labelled leucine by collection of the appropriate peak of the orthophthaldehyde (OPA) derivative from a C18 reversed phase HPLC column. The derivatizing reagent comprised 0.4 M OPA-0.45 M 3-mercapto-proprionic acid in MeOH combined with 1/2 vol 1M KBO₃-0.2 M Na₄EDTA or 1M KBO₃-1M K₂CO₃ immediately prior to mixing with 1 vol amino acid solution. The authors conclude that the method is more rapid than ion exchange chromatography, utilizes standard chromatographic equipment without effluent stream splitting, and is not limited in principle to essential amino acids

[en] The potassium permanganate oxidation of 2,6-di-tert-butyl-4-methylphenol(1), adsorbed on a stationary Celite phase, gives several interesting monomeric products in low yields. These products were identified primarily by ¹³C and ¹H NMR. The products of oxidation of 1 with performic acid and also with oxygen in alkaline ethanol are related and their structures and NMR spectral features are also discussed

[en] Cross polarization between dilute effectively isolated ¹³C-³¹P spin pairs provides a unique method to examine selectively the microenvironment around the phosphorus atom in organophosphorus substances. Strong oscillations occur during cross polarization between these isolated spin pairs in MAS experiments on microcrystalline powders. The oscillation frequency is proportional to the ¹³C-³¹P dipolar interaction and hence allows specific internuclear distance determinations on powder samples. Maximum carbon signal intensity and experimental simplicity are achieved in double cross polarization (DCP)/MAS ¹³C NMR experiments that impose a short T_1p on the ³¹P magnetization by ³¹P radio frequency phase modulation. This experimental stratagem suppresses cross-polarization oscillations and yields simple exponential kinetics for the transfer process. It also relaxes the tolerance on the match condition and MAS speed for cross polarization between weakly coupled dipole pairs

[en] The reactions of polycyclic aromatic hydrocarbons in molten antimony trichloride at temperatures from 80 to 175⁰C have been studied by in situ ¹H NMR and quench and separation techniques. Decomposition takes place by a complex series of hydrogen redistribution reactions whose net effect is a disproportionation of a type not previously known to occur. The reaction of anthracene (I) was studied in detail. Some of the anthracene molecules lose aryl-bound hydrogen and are condensed into larger molecules with aryl-aryl bonds such as the asymmetric bianthracenes (IV, V, and VI) and anthraaceanthrylenes (VII and VIII). The hydrogen released by these reactions is quantitatively captured by other anthracene molecules to form hydroaromatic molecules such as the 9,10-dihydro- and 1,2,3,4-tetrahydroanthracenes (II and III). The catalytic role of the solvent's Lewis acidity was demonstrated by the fact that the addition of a few mol % of a strong chloride donor reduced the reaction rates by a large factor. The reaction behavior of a group of related arenes (naphthalene, phenanthrene, chrysene, pyrene, perylene, and naphthacene) of widely varying basicity and oxidizability was also surveyed. 2 figures

[en] The effects of centrally administered beta-endorphins on glucose homeostasis in the conscious dog were studied. Intracerebroventricular administration of beta-endorphin (0.2 mg/h) caused a 70% increase in plasma glucose. The mechanism of the hyperglycemia was twofold: there was an early increase in glucose production and a late inhibition of glucose clearance. These changes are explained by marked increases in plasma epinephrine (30-fold) and norepinephrine (6-fold) that occurred during infusion of beta-endorphin. Central administration of beta-endorphin also resulted in increased levels of adrenocorticotropic hormone and cortisol. In addition there was an increase in plasma insulin but no increase in plasma glucagon. Intravenous administration of beta-endorphin did not alter glucose homeostasis. Intracerebroventricular administration of acetylated beta-endorphin did not perturb glucose kinetics or any of the hormones that changed during infusion of the unacetylated peptide. We conclude that beta-endorphin acts centrally to cause hyperglycemia by stimulating sympathetic outflow and the pituitary-adrenal axis. Acetylation of beta-endorphin abolishes the in vivo activity of the peptide

[en] Leucine (LEU) kinetics were assessed using a primed-continuous infusion of L-[1-14C]LEU in normal overnight-fasted male volunteers during a basal period and an experimental period where insulin (INS) was infused at either 0.6, 1.2, 2.5, 5.0, 10, or 20 mU.kg-1.min-1 with euglycemia maintained. Two protocols were used: subjects were allowed to develop hypoaminoacidemia or plasma essential amino acids (AA) were maintained near basal levels by frequently monitoring plasma LEU in conjunction with variable infusions of an AA solution (LEU infused = 0.41, 0.72, 0.93, 1.03, 1.31, and 1.35 mumol.kg-1.min-1 at escalating INS doses, respectively). Basal rates of LEU appearance (Ra), nonoxidative disappearance (NORd) and oxidative disappearance (OXRd) were similar in both protocols (means = 1.74, 1.40, and 0.36 mumol.kg-1.min-1, respectively). INS infusions without AA resulted in a progressive decrement in LEU Ra (14 to 45%), NORd (16-41%), and OXRd (3-56%) compared with basal values. The infusion of AA resulted in an additional reduction in endogenous Ra (P less than 0.01; approximately 100% suppression achieved at plasma INS greater than 1,000 microU/ml) and a blunting of NORd reduction (P less than 0.05) at each dose of INS. Observed differences in INS's suppression of LEU Ra between the two protocols suggests the existence of a component of whole body proteolysis that is highly dependent on circulating plasma AA. Therefore, hypoaminoacidemia associated with INS treatment would appear to blunt the responsiveness of INS's suppression of protein breakdown and in the presence of near basal plasma AA, proteolytic suppression by INS is enhanced