Coupled hydrogen-bonding interactions between beta-carboline derivatives and acetic acid.

In this work, we have analysed the tendency of two beta-carboline derivatives, harmane and norharmane, in the formation of hydrogen bonds. We obtained the (1)H and (13)C NMR spectra of different mixtures of these derivatives with acetic acid (AcOH) in CDCl(3). A cyclic 1:3 complex is proposed between harmane and AcOH, while a 1:2 complex is proposed for norharmane. Chemical shifts at temperatures between 233 and 323 K were measured: lowering the temperature produces the same effect as increasing the amount of AcOH in solution. The (13)C data confirm a delocalisation of the pi electron density towards the pyridinic ring that occurs when AcOH is added.

Electrodeposition of polythiophene assisted by sonochemistry and incorporation of fluorophores in the polymeric matrix.

This work studies the effect of an ultrasonic field of 530 kHz frequency on the electrodeposition of polythiophene in an acetonitrile solution using lithium perchlorate as background electrolyte. The results obtained show an increase in the polymer mass transfer produced and a more compact and homogenous morphology of the films yielded by sonoelectrochemistry. Electrodeposition of the polymer was also carried out in the presence of the fluorophores Harmane (1-methyl-9H-pyrido[3,4-b]indole) or BCCM (9H-pyrido[3,4-b]indole-3-carboxylic acid methyl ester). Confocal microscopy measurements performed on the films synthesised in the presence of these compounds showed that the latter are embedded in the polymer when it is sonoelectrogenerated at a potential of 2.2, 2.5 or 2.8 V. Films generated in the absence of ultrasound showed no fluorescence.

Photophysical properties of methyl beta-carboline-3-carboxylate mediated by hydrogen-bonded complexes--a comparative study in different solvents.

The hydrogen bonding interactions of methyl beta-carboline-3-carboxylate (BCCM) in both ground and first singlet excited electronic states have been studied in solvents with different properties in the presence of acetic acid, a hydrogen-bonding donor/acceptor. The methyl ester substituent reduces the pyridinic nitrogen basicity of this beta-carboline derivative. This fact has let us study the hydrogen bonding interactions in a higher range of acetic acid concentrations than for other beta-carboline derivatives previously studied. Steady and non-steady photophysical studies have been carried out in two non-polar solvents, benzene and p-dioxane; and in two polar solvents, acetonitrile and dichloromethane. Six different fluorescence emissions have been isolated corresponding to the uncomplexed BCCM, the protonated species and four different complexes between BCCM and acetic acid whose structures we have tried to elucidate.

ESR-spin trapping study on the sonochemistry of liquids in the presence of oxygen. Evidence for the superoxide radical anion formation.

The sonolysis of water and some organic liquids such as ethylene glycol, methanol and chloroform in the presence of oxygen, at 20 and 475 kHz ultrasound frequencies has been investigated by the ESR-spin trapping technique. 5,5-Dimethyl-1-pyrroline-N-oxide (DMPO), 3,3,5,5-tetramethylpyrroline-N-oxide (TMPO) and N-tert-butyl-alpha-phenyl nitrone (PBN) were able to trap superoxide radical anion, generated as the result of the sonication of the organic media. The addition of superoxide dismutase (SOD) resulted in a dramatic decrease of the ESR signal intensity of the superoxide radical adduct. In addition, the thermolysis of the liquids under ultrasound was shown by ESR detection of the spin adducts of the radicals formed by homolytic fragmentation. Occasionally, the nature of the detected spin adduct was dependent on the sonication time or on the frequency of the ultrasonic radiation. Experiments carried out in the presence of 2-methyl-2-nitrosopropane (MNP) resulted in the detection of radicals originating from thermal decomposition of the spin trap, showing its lability under ultrasonic radiation.

Transition probabilities and average cross sections for the Na2 B1pi(u) --> X1sigma(g)+ system using as excitation the 4880 A Ar+ laser line.

The fluorescence spectrum of Na2 induced by the 4879.86 A line of an Argon ion laser has been analyzed with special emphasis on determination of accurate relative intensities. We have observed nineteen fluorescence series for the B1pi(u) --> X1sigma(g)+ band system. Some series are reported for the first time. The radiative transition probabilities for the observed fluorescence series were calculated using hybrid potential energy curves for the B1pi(u) and X1sigma(g)+ states constructed up to dissociation and a B-X transition dipole moment function. Radiative lifetimes for the rovibrational levels of the upper states pumped by the laser line have also been calculated. The transition probabilities and lifetimes agree with the corresponding observed measurements usually within the experimental uncertainty. From the rotational satellite structure with deltaJ' = +/- 1, +/- 2...+/- 20, for some nu''-bands of the most intense fluorescence series induced by emission from the vibrational-rotational levels: nu' = 6, J' = 43 and v' = 9, J' = 56, collision-induced transition rates and average cross sections have been obtained.

Analysis and Transition Probabilities for the Na2 B1Piu --> X1Sigma+g System Using as Excitation the 4727-Å Ar+ Laser Line.

The fluorescence spectrum of Na2 induced by the 4726.87 Å line of an Argon ion laser has been analyzed with special emphasis on determination of accurate relative intensities. This work extends previous observations on Na2 by using this excitation line. We have observed eight fluorescence series for the B1Piu --> X1Sigma+g band system corresponding to the excitation transitions v' = 9, J' = 38 <-- v" = 1, J" = 37; v' = 14, J' = 46 <-- v" = 4, J" = 47; v' = 14, J' = 81 <-- v" = 3, J" = 80; v' = 15, J' = 65 <-- v" = 4, J" = 66; v' = 12, J' = 36 <-- v" = 3, J" = 36; v' = 12, J' = 40 <-- v" = 3, J" = 39 v' = 17, J' = 45 <-- v" = 6, J' = 45 and v' = 18, J' = 63 <-- v" = 6, J" = 63. The seven latter series are reported for the first time. Optically pumped laser transitions obtained in Na2 vapor by using this excitation wavelength have been assigned. The radiative transition probabilities for the observed fluorescence series were calculated using hybrid potential energy curves for the B1Piu and X1Sigma+g states constructed up to last vibrational levels and an ab initio transition dipole moment function. Radiative lifetimes for the rovibrational levels of the upper states pumped by the laser line have also been calculated. The transition probabilities and lifetimes agree with the corresponding observed measurements, usually within the experimental uncertainty. From the rotational satellite structure with DeltaJ' = +/-1 and +/-2 of some bands, for the most intense fluorescence series, collision-induced transition rates and average cross sections have been obtained. Copyright 1998 Academic Press.

Protonation of norharmane as a sonochemical dosimeter for organic media. The effect of temperature.

The sonolysis of different organic and aqueous media in the presence of norharmane produce its protonation. This simple and reversible reaction is particularly suitable as a dosimetric reaction in order to measure the relative amount of cavitation induced by the ultrasonic irradiation in non aqueous solutions. The protonation rate increases when small amounts of chloroform are added to the solution. The frequency (20 and 475 kHz) and temperature effects on the reaction rate are also studied. Our results show that sonication of aqueous solutions at high frequency leads to a strongly oxidant medium.

Fetal and maternal amino acid concentrations during fasting in the ewe.

The present investigation was undertaken to quantitate the whole-blood amino acid concentrations of the mother and fetus over an extended period of fasting using a chronic sheep preparation. Fetal amino acid levels generally increased or remained relatively high during the fast (e.g., alanine, glycine, valine, leucine). In contrast to the situation in the fetus, most amino acids (alanine, glycine, glutamine, serine, and threonine) decreased in concentration in the ewe with fasting. Alanine levels changed most dramatically in the ewe, decreasing to less than 50% of the fed state values within 72 h of fasting. Therefore, while the supply of gluconeogenic amino acids becomes limited within the maternal circulation during fasting, levels of these amino acids remain high or increase in the fetal arterial blood.

Amino acid composition of preterm and term breast milk during early lactation.

The amino acid composition of the protein nitrogen (PN) and non-protein nitrogen (NPN) fractions of human milk obtained from mothers delivering maturely and at term was studied weekly until 44 weeks postconceptual age. Preterm milk contained significantly more total nitrogen (TN) and PN than the term milk; the NPN component was similar between the two groups. The amount of PN decreased significantly in both term and preterm milk during the first weeks of lactation (from approximately 300 mg/100 ml at day 7 to approximately 220 mg/100 ml at 8 weeks), while the level of NPN remained constant (approximately 33 mg/100 ml). The concentrations of almost all amino acids in the PN fraction also decreased during early lactation, while those in the NPN portion remained relatively constant. Glutamate (1630 microM) and taurine (398 microM) were the most plentiful amino acids found in the NPN fraction. No differences in the amino acid composition of the PN were detectable between the preterm and term group. Amino acids measured in this study accounted for 67% of the TN present. Whether the remaining 33% of the nitrogen can be attributed to nitrogen-containing substances other than amino acids and/or methodologic error is not known.

Effects of exogenous glucagon on concentrations of glucose, fructose and insulin in plasma of sheep fetus.

Exogenous glucagon infused into the fetal sheep resulted in an increase in the concentration of glucose and insulin in fetal arterial plasma without a significant change in the concentration of fructose. Lack of any significant changes in glucagon, insulin, glucose and fructose concentrations in maternal plasma suggests that the alterations in the fetus are secondary to fetal metabolic and hormonal mechanisms rather than reflecting effects of maternal metabolism.

Effect of acute nonsurgical stress on fetal and maternal plasma glucose, glucagon and insulin concentration in sheep.

The purpose of this study was to investigate the effect of nonsurgical stress on plasma glucose, insulin and glucagon in the ewe and fetus. Plasma glucose, insulin and glucagon were measured before and after a 2 min period of verbal and physical startling of much greater magnitude than that to which we ewe is exposed during routine blood drawing. Studies were completed on 5 fed ewes, 5 fasted ewes and on 4 fetuses of fasted ewes. There were no significant differences after a startling compared to the control values. Thus, there appears no need to allow the ewe a prolonged period (more than 1-2 weeks) to become accustomed to handling by humans before chronic metabolic studies involving serum glucose, insulin and glucagon are undertaken.