Zur Biosynthese des Sinalbins, 3. Mitt.: Die Rolle von p-Cumarsäure und p-Hydroxyphenylacetaldehydoxim

Zusammenfassung Der Biosyntheseweg zu dem phenolischen C₆–C₂-Senfölglucosid Sinalbin verläuft über Shikimisäure,L-Tyrosin und p-Hydroxyphenylacetaldehydoxim. Untersuchungen anSinapis alba ergaben für das Oxim einen gegenüberL-Tyrosin um eine Größenordnung höheren Einbau. Phenylacetaldehydoxim wird in dieser Pflanze nur in Glucotropaeolin, nicht aber in die in p-Stellung hydroxylierte Verbindung übergeführt; der Hydroxylierungstyp ist somit bereits auf der Stufe der Aminosäure vorgegeben.Die von derL-Tyrosin-ammoniak-lyase katalysierte Reaktion ist reversibel. Der Übergang von p-Cumarsäure inL-Tyrosin konnte sowohl in vivo als auch mit Hilfe von gereinigten Enzymen ausSinapis alba undHordeum vulgare nachgewiesen werden. Es werden die Übergänge von Shikimisäure undL-Phenylalanin zuL-Tyrosin verglichen und die physiologische Bedeutung der verschiedenen zumL-Tyrosin führenden Wege diskutiert.

---

Biosynthesis of sinalbin, III. the role of p-coumaric acid and p-hydroxyphenylacetaldehyde oxime

The biosynthesis of sinalbin, a phenolic mustard oil glucoside with a C₆–C₂ skeleton, proceeds viaL-tyrosine and p-hydroxyphenylacetaldehyde oxime. The incorporation of the oxime was found to be more than one order of magnitude higher than that ofL-tyrosine. This transformation of the p-hydroxyphenylacetaldehyde oxime into sinalbin and S-(-D-glucopyranosyl)-p-hydroxyphenylacetothiohydroximic acid could be demonstrated in 6 weeks old plants ofSinapis alba. The finding that phenylacetaldehyde oxime was incorporated only into glucotropaeolin but not into sinalbin indicates that either the hydroxylation of the benzene ring occurs at the level of the amino acid or that the hydroxyl group comes from the cyclohexane precursors.The chemical synthesis and the physical properties of the p-hydroxyphenylacetaldehyde oxime are described. p-Hydroxyphenylacetaldehyde oxime-1-¹⁴C was obtained by condensation of p-hydroxybenzaldehyde with nitromethane-¹⁴C and by reduction of the nitrostyrene with zine—acetic acid.The conversion ofL-tyrosine into p-coumaric acid catalysed by theL-tyrosine ammonia lyase was found to be reversible. The transformation of p-coumaric acid intoL-tyrosine could be shown in detached leaves ofSinapis alba and also with purified enzyme preparations from that plant andHordeum vulgare. There are indications that three biosynthetic routes leading toL-tyrosine exist in plants. These biosynthetic pathways and their physiological significance are discussed.

     

Identification of harmful time harmonic interactions in a high power squirrel-cage traction machine

The paper offers a methodology for the identification the time harmonic interactions with a strong negative impact on the rotor of a high power induction machine. These potentially dangerous pulsating torques may be effectively reduced by carefully setting the machine’s drive control. A novel approach based on a complex finite element model and further post-processing is used. Results obtained from electromagnetic calculations in the form of pulsating torques are used as mechanical loading of a structural dynamic model. This complex model intended for rotor vibration analysis is described in brief in the mechanical part of the paper. The proposed methodology is applied to the machine used as a propulsion unit for multisystem locomotives of 1600 kW power.     

Stereoselective syntheses of heptaprenylphosphoryl β-d-arabino-and β-d-ribo-furanoses

The stereoselective syntheses of heptaprenylphosphoryl β-d-arabinofuranose and heptaprenylphosphoryl β-d-ribofuranose are described. In the synthesis of the d-arabino product, the stereoselectivity was achieved by the coupling of a suitably protected β-d-arabinofuranosyl phosphate intermediate with an activated form of heptaprenol and subsequent deprotection. In the case of the ribo-analog, the desired β-anomer could be obtained by the more convenient phosphoramidite method. The products were successfully employed in the mycobacterial epimerase assay.     

Retention of organic ligands on anionic and nonionic resins: Application to the separation and preconcentration of metal ions

Complexing resins obtained by retention of an organic compound on anionic and nonionic conventional exchangers have been reviewed. The influence of different parameters—nature of fixed ligand, kind and chemical form of the conventional resin, and pH of the aqueous solution—on characteristics and applications of this type of resin has been discussed. Results from the literature have been tabulated to simplify their presentation.     

Indican determination in urine: Application for urine determination in adulterated cow milk

A spectrophotometric procedure for the determination of indican in urine based in Jolles' reaction, modified by Bermejo-Martínez and Barrera-Ramallo, is described; and it is applied for the determination of urine in adulterated cow milk, until addition of 2% human urine is estimated.     

On vertical skew symmetric almost contact 3-structures

We consider a (2m + 3)-dimensional Riemannian manifold M(ξ _r, η^r, g ) endowed with a vertical skew symmetric almost contact 3-structure. Such manifold is foliated by 3-dimensional submanifolds of constant curvature tangent to the vertical distribution and the square of the length of the vertical structure vector field is an isoparametric function. If, in addition, M(ξ _r, η^r, g ) is endowed with an f -structure φ, M, turns out to be a framed f−CR-manifold. The fundamental 2-form Ω associated with φ is a presymplectic form. Locally, M is the Riemannian product of two totally geodesic submanifolds, where is a 2m-dimensional Kaehlerian submanifold and is a 3-dimensional submanifold of constant curvature. If M is not compact, a class of local Hamiltonians of Ω is obtained.     

Demonstration of a HeNe/CH4-based optical molecular clock

We implement a simple optical clock based on the F2(2) [P(7), v3] optical transition in methane. A single femtosecond laser's frequency comb undergoes difference frequency generation to provide an IR comb at 3.39 microm with a null carrier-envelope offset. This IR comb provides a phase-coherent link between the 88-THz optical reference and the rf repetition rate. Comparison of the repetition rate signal with a second femtosecond comb stabilized to molecular iodine shows an instability of 1.2 x 10(-13) at 1 s, limited by microwave detection of the repetition rates. The single-sideband phase noise of the microwave signal, normalized to a carrier frequency of 1 GHz, is below -93 dBc/Hz at 1-Hz offset.     

Use of enzymatic hydrolysis for the multi-element determination in mussel soft tissue by inductively coupled plasma-atomic emission spectrometry

A systematic evaluation of different variables affecting the enzymatic hydrolysis of mussel soft tissue by five enzymes, three proteases (pepsin, pancreatin and trypsin), lipase and amylase, has been carried out for the determination of trace elements (As, Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Enzymatic hydrolysis methods offers advantages such as a less species alteration, safer laboratory conditions and a less contaminant wastes. The enzymatic hydrolysis was performed in an incubation camera Boxcult with orbital and horizontal shaker. Variables affecting the enzymatic hydrolysis process were simultaneously studied by applying a Plackett-Burman design (PBD). For a confidence interval of 95%, the significant factors for all enzymes and for most of the elements were the pH, the incubation temperature and the ionic strength. These significant factors were optimized later by using a central composite design (CCD), which gave optimum conditions at pH of 1, incubation temperature of 37 °C and ionic strength fixed by sodium chloride at 0.2 M when using pepsin. For pancreatin, trypsin, lipase and amylase there were found two different optimum condition sets. The first one involves the use of a 0.5 M phosphate buffer (ionic strength), at a pH of 6 and at an incubation temperature of 37 °C, which allows the quantitative extraction of Al, Cr, Mn, Pb and Zn. The second conditions set employees a 0.1 M phosphate buffer (ionic strength), a pH of 9 and an incubation temperature at 37 °C, and it results adequate to extract As, Cd, Cu, Fe and Ni. Analytical performances, repeatability of the over-all procedure and accuracy, by analyzing DORM-1, DORM-2 and TORT-1 certified reference materials, were finally assessed for each enzyme. Good agreement with certified values has been assessed for most of the elements (As, Cd, Cr, Cu, Mn, Ni, Pb and Zn) when using trypsin, pepsin and/or pancreatin, except for Cd and Pb in DORM-1 and DORM-2 because of the certified contents in such certified reference materials are lower than the limit of detection (0.10 and 0.16 μg g⁻¹ for Cd and Pb, respectively, for the use of trypsin).