Enzymatic acylation of 1-alkyl-, 1-alkenyl-and 1-acyl glycero-3-phosphorylethanolamine in developing rat brain

Rat brain particulate fractions were shown to acylate [32P]1-alkyl-sn-glycero-3-phosphorylethanolamine (GPE). While the main product is 1-alkyl-2-acyl GPE, about 12 per cent of the radioactivity was also found in 1-alkenyl-2-acyl GPE. The acyl transferase activity was completely dependent on added ATP and CoA and it was localized mainly in the microsomal fraction. A comparative study of acyl transferase activities to 1-alkyl-, 1-alkenyl-, and 1-acyl GPE by crude mitochondrial fraction and microsomes of 10, 16 and 22-day-old rat brains showed a progressive increase in activity with development. In the 22-day-old rat brain the order of activity towards the three substrates is as follows: 1-acyl GPE ± 1-alkenyl GPE ± 1-alkyl GPE with a crude mitochondrial fraction and 1-acyl GPE ± 1-alkyl GPE ± 1-alkenyl GPE with microsomes.

Inhibition of cortisol-mediated induction of hepatic tryptophan-2,3-dioxygenase by norepinephrine

Norepinephrine inhibits cortisol-mediated induction of hepatic tryptophan pyrrolase in rats. During cold exposure the stabilization of this enzyme appears to occur by an interaction of corticoids and norepinephrine on the induction process.

Crystallization Kinetics and Electrical Relaxation of BaO-0.5Li(2)O-4.5B(2)O(3) Glasses

Transparent glasses in the composition BaO-0.5Li(2)O-4.5B(2)O(3) (BLBO) were fabricated via the conventional melt-quenching technique. X-ray powder diffraction combined with differential scanning calorimetric (DSC) studies carried out on the as-quenched samples confirmed their amorphous and glassy nature, respectively. The crystallization behavior of these glasses has been studied by isothermal and nonisothermal methods using DSC. Crystallization kinetic parameters were evaluated from the Johnson-Mehl-Avrami equation. The value of the Avrami exponent (n) was found to be 3.6 +/- 0.1, suggesting that the process involves three-dimensional bulk crystallization. The average value of activation energy associated with the crystallization of BLBO glasses was 317 +/- 10 kJ/mol. Transparent glass-ceramics were fabricated by controlled heat-treatment of the as-quenched glasses at 845 K/40 min. The dielectric constants for BLBO glasses and glass-ceramics in the 100 Hz-10 MHz frequency range were measured as a function of the temperature (300-925 K). The electrical relaxation and dc conductivity characteristics were rationalized using electric modulus formalism. The imaginary part of the electric modulus spectra was modeled using an approximate solution of the Kohlrausch-Williams-Watts relation. The temperature-dependent behavior of stretched exponent (beta) was discussed for the as-quenched and heat-treated BLBO glasses.

Structure of ethyl 1,2,2-tricyano-3-(4-nitrophenyl)-cyclopropane-1-carboxylate

C15HIoN404, monoclinic, P2~/c, a = 10.694(8), b = 11.743 (8), c - 12.658 (8) A, fl = 113.10 (7) °, V = 1462.1 A 3, Z = 4, O m = 1 "38, O c = 1.408 g cm -3, t,t(MoKa, ~, = 0.7107 ]~) = 0.99 cm -i, F(000) = 640. The structure was solved by direct methods and refined to an R value of 0.054 using 1398 intensity measurements. The relative magnitudes of interaction of the substituents and the extent to which a ring can accommodate interactions with substituents are discussed.

Polarized Ethylenes: Structures of (l,3-Dimethyl-2-imidazolidinylidene)malononitrile and (l,3-Dimethyl-2-perhydropyrimidinylidene)malononitrile

Crystal structures of the title compounds, (I) and (II), have been determined by three-dimensional diffraction methods. Crystals of CsHIoN 4 (I) are monoclinic, space group P21/a with Z = 4, Mr= 162, a = 7.965 (1), b = 16.232 (2), c = 7.343 (1) A, fl = 113.54 (1) °, V = 890.7 A 3, D,n = 1.218, D x = 1.208 gcm -3, g(Cu Ka, 2 = 1.5418/~) = 6.47 em -1, F(000) = 344. The crystals of C9H12N4 (II) are orthorhombic, space group P21en, with Z = 4, Mr = 176, a = 7.983 (3), b = 8.075 (2), c = 14.652 (3) ./k, V = 44.43/~3, Dm= 1.219, D x = 1.237 g cm -3, #(Mo Ka, ). = 0.7107 ,/k) = 0.868 cm -1, F(000) = 376. Both structures were solved by direct methods and refined to R = 5.8% for (I) and 5.3 % for (II). The C-C double-bond distances are 1.407 (3) in (I) and 1.429 (6)/~ in (II), appreciably longer than normal. The steric and push-pull effects result in rotation about the C=C bond, the rotation angles being 20.2 (3) in (I) and 31.5 (6) o in (II).

Stresses and Displacements under a Flexible Circular Foundation in the Presence of Friction or Adhesion

Die Vorliegende Arbeit beschäftigt sich mit den Spannungen und Verschiebungen an einem elastischen Halbraum unter einem kreisförmigen biegsamen Fundament, wenn an der Kontaktfläche vollkommenes Haften besteht. Das gemischte Randwertproblem wird mit Hilfe von Hankel-Transformationen auf duale Integralgleichungen von Titchmarsh- Typ zurückgeführt. Für die Berechnung der Spannungen und Verschiebungen werden Gaußsche Quadraturformeln benutzt. Die Ergebnisse werden mit denen verglichen, die man bei glattem Fundament erhält, und der Einfluß der Poisson-Zahl auf die Spannungen und Verschiebungen wird deutlich gemacht. Schließlich werden die Ergebnisse für den praktischen Gebrauch in Diagrammen und Tabellen zusammengefaßt.

Ethyl 2-acetyl-3-(4-chloroanilino)butanoate

The title compound, C14H18ClNO3, adopts an extended conformation, with all of the main chain torsion angles associated with the ester and amino groups trans. In the crystal, inversion dimers linked by pairs of N-H center dot center dot center dot O hydrogen bonds are observed.

Proton NMR spectra including 13C- and 77Se-satellites in organoselenium compounds oriented in the nematic phase : Part 1. The spectrum of 2,1,3-benzoselenadiazole

The vibrationally corrected structure of 2,1,3-benzoselenadiazole is derived from the proton NMR spectrum including 13C-H and 77Se-H satellites, in a nematic solvent. The results indicate considerable bond-fixation in the 6-membered ring. References

The structures of ethyl 1,2,2-tricyano-3,3-dimethylcyclopropane-1-carboxylate and ethyl 2',3,3'-tricyanocyclohexanespirocyclopropane-2'-carboxylate

The crystal and molecular structures of C ,,H,IN302 (I) and C14HIsN302 (II) have been determined by direct methods using three-dimensional X-ray diffractometer data. Crystals of (I) are orthorhombic, space group Pna21, with a = 14.662(6), b = 10.492(5), c = 7.375 (3)A, Z = 4, V = 1134.5 A 3, D O = 1.25 (by flotation), D e = 1.269 Mgm -a, g(MoKa) = 0.085 mm -1. Crystals of (II) are monoclinic, space group P21/a, with a = 7.886 (5), b = 22.011 (8), c = 8.100 (3) A, fl = 103.12 (5) °, Z = 4, V = 1369.2 A 3, D O = 1.23 (by flotation), D e = 1.255 Mg m -3, g(Mo Kct) = 0.080 mm -1. Least-squares full-matrix refinement based on 782 (I) and 1400 independent reflections (II) converged at R = 0.040 (I) and 0.042 (II). The effect of electron-withdrawing substituents on the geometry of the cyclopropane ring is discussed.

Structure of a new crystal form of 2-{[3-(trifluoromethyl)phenyl]amino}benzoic acid (flufenamic acid)

C14Ht0F3NO2, P2.Jc, a = 12.523 (4), b = 7.868(6), c = 12.874 (3)A, fl = 95.2 (2) ° , O,,, = 1.47 (4), D e = 1.47 Mg m -3, Z = 4. Final R = 0.074 for 2255 observed reflections. The carboxyl group and the phenyl ring bearing the carboxyl group are nearly coplanar whereas the two phenyl rings are inclined with respect to each other at 52.8 ° . The difference between the two polymorphs of flufenamic acid lies in the geometrical disposition of the [3-(trifluoromethyl)- phenyl]amino moiety with respect to the benzoic acid moiety. As in other fenamate structures, the carboxyl group and the imino N atom are connected through an intramolecular hydrogen bond; also, pairs of centrosymmetrically related molecules are connected through hydrogen bonds involving carboxyl groups.

Conformational effects in the hydrogenation of hemimellitic and cyclohex-1-ene-1,2,3-tricarboxylic acids

The three possible isomers of cyclohexane-1,2,3-tricarboxylic acid were synthesised and separated in order to study the regiospecificity and stereoselectivity of the α-C alkylation of their trimethyl esters. No definitive conclusions could be reached on this aspect for reasons which became apparent in the course of the work. However, the three independent methods adopted for the synthesis of the isomeric tricarboxylic acids have given dramatically different isomer compositions. The reasons are explored in this paper.

Allosteric serine hydroxymethyltransferase from monkey liver: Correlation of conformational changes caused by denaturants with the alterations in catalytic activity

The far-ultraviolet region circular dichroic spectrumof serine hydroxymethyltransferase from monkey liver showed that the protein is in an α-helical conformation. The near ultraviolet circular dichoric spectrum revealed two negative bands originating from the tertiary conformational environment of the aromatic amino acid residues. Addition of urea or guanidinium chloride perturbed the characteristic fluorescence and far ultraviolet circular dichroic spectrum of the enzyme. The decrease in (θ)222 and enzyme activity followed identical patterns with increasing concentrations of urea, whereas with guanidinium chloride, the loss of enzyme activity preceded the loss of secondary structure. 2-Chloroethanol, trifluoroethanol and sodium dodecyl sulphate enhanced the mean residue ellipticity values. In addition, sodium dodecyl sulphate also caused a perturbation of the fluorescence emission spectrum of the enzyme. Extremes of pH decreased the – (θ)222 value. Plots of –(θ)222and enzyme activity as a function of pH showed maximal values at pH 7.4-7.5. These results suggested the prevalence of "conformational flexibility" in the structure of serine hydroxymethyltransferase.

Allosteric serine hydroxymethyltransferase from monkey liver: temperature induced conformational transitions

The homogeneous serine hydroxymethyltransferase from monkey liver was optimally activate at 60°C and the Arrhenius plot for the enzyme was nonlinear with a break at 15°C. The monkey liver enzyme showed high thermal stability of 62°C, as monitored by circular dichroism at 222 nm, absorbance at 280 nm and enzyme activity. The enzyme exhibited a sharp co-operative thermal transition in the range of 50°-70° (Tm= 65°C), as monitored by circular dichroism. L-Serine protected the enzyme against both thermal inactivation and thermal disruption of the secondary structure. The homotropic interactions of tetrahydrofolate with the enzyme was abolished at high temperatures (at 70°C, the Hill coefficient value was 1.0). A plot of h values vs. assay temperature of tetrahydrofolate saturation experiments, showed the presence of an intermediate conformer with an h value of 1.7 in the temperature range of 45°-60°C. Inclusion of a heat denaturation step in the scheme employed for the purification of serine hydroxymethyltransferase resulted in the loss of cooperative interactions with tetrahydrofolate. The temperature effects on the serine hydroxylmethyltransferase, reported for the first time, lead to a better understanding of the heat induced alterations in conformation and activity for this oligomeric protein.