Biosynthesis of mustard oil glucosides: 3-benzylmalic acid, a precursor of 2-amino-4-phenylbutyric acid and of gluconasturtiin

1968 ◽  
Vol 46 (5) ◽  
pp. 401-405 ◽  
Author(s):  
E. W. Underhill
Keyword(s):  
High Efficiency ◽  
Mustard Oil ◽  
Nasturtium Officinale ◽  
Acid Degradation ◽  
Phenylbutyric Acid

2-Amino-4-phenylbutyric acid was isolated from Nasturtium officinale R. Br. (watercress) and identified by gas–liquid and paper chromatography.Various 14C-labelled compounds, including 3-benzylmalic-1,2-14C acid, were fed to N. officinale and their efficiencies as precursors of the aglycone moiety of gluconasturtiin and of 2-amino-4-phenylbutyric acid were determined. The efficiency of conversion of 14C from 3-benzylmalic-1,2-14C acid into gluconasturtiin aglycone was greater than that from DL-phenylalanine-2-14C or -3-14C, acetate-2-14C, shikimic-G-14C acid, and D-glucose-G-14C, but was less than that from DL-2-ammo-4-phenylbutyric-2-14C acid. Degradation of the aglycone obtained from plants fed 3-benzylmalic-1,2-14C acid revealed the tracer had been incorporated specifically into the isothiocyanate carbon and it was concluded that the acid was converted to gluconasturtiin with the loss of C-1. As was reported previously, the carboxyl carbons of acetate and phenylalanine were not incorporated into gluconasturtiin aglycone.The 14C from DL-phenylalanine-2-14C, acetate-1-14C, acetate-2-14C, and from 3-benzylmalic-1,2-14C acid was incorporated into 2-amino-4-phenylbutyric acid with high efficiency. The results support the view that 2-amino-4-phenylbutyric acid is formed from phenylalanine and acetate via 3-benzylmalic acid.

Chain Elongation of Aromatic Amino Acids: the Role of 2-Benzylmalic Acid in the Biosynthesis of a C6C4 Amino Acid and a C6C3 Mustard Oil Glucoside

1974 ◽  
Vol 52 (10) ◽  
pp. 916-921 ◽  
Author(s):  
D. Dörnemann ◽  
W. Löffelhardt ◽  
H. Kindl
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Aromatic Amino Acids ◽  
Chain Elongation ◽  
Mustard Oil ◽  
Barbarea Vulgaris ◽  
Nasturtium Officinale ◽  
A Chain ◽  
Phenylbutyric Acid

A chemical synthesis of specifically 14C-labelled 2-benzylmalic acid, hitherto unknown, was developed. 4-Phenylacetoacetate obtained by condensation of phenylacetyl chloride-1-14C with ethyl acetoacetate yielded 2-benzylmalic acid-2-14C after cyanohydrin reaction and hydrolysis.2-Benzylmalic acid-2-14C, administered to shoots of Nasturtium officinale and Barbarea vulgaris, was shown to be an efficient precursor of the aglucone moiety of the mustard oil glucoside gluconasturtiin. The incorporation of radioactivity agreed well with the values reported for incorporation of 3-benzylmalic acid, but was considerably higher than that obtained after application of L-phenylalanine-U-14C. A conversion of 2-benzylmalic acid into 3-benzylmalic acid and 2-amino-4-phenylbutyric acid could also be demonstrated. These findings provide the final evidence for a chain-lengthening mechanism leading to homologous amino acids as proposed by Underbill and Wetter in 1966.

BIOSYNTHESIS OF MUSTARD OIL GLUCOSIDES: V. FORMATION OF GLUCONASTURTIIN FROM L-γ-PHENYLBUTYRINE-C14-N15 IN WATERCRESS

1965 ◽  
Vol 43 (2) ◽  
pp. 179-187 ◽  
Author(s):  
E. W. Underbill
Keyword(s):  
Sodium Acetate ◽  
Amino Nitrogen ◽  
Competition Experiment ◽  
Mustard Oil ◽  
Side Chain ◽  
Nasturtium Officinale ◽  
A Chain ◽  
Phenylbutyric Acid

C14-Labelled compounds were fed to watercress (Nasturtium officinale R. Br.) and their efficiency as precursors of the aglycone portion of gluconasturtiin compared. Phenylalanine-2- and -3-C14 and sodium acetate-2-C14 were efficient precursors of the aglycone but neither compound was as efficient a precursor as γ-phenylbutyrine (2-amino-4-phenylbutyric acid). Approximately 40% of the C14 from γ-phenylbutyrine-2- or -3-C14 was incorporated into the aglycone side chain. Results of studies with doubly labelled L-γ-phenylbutyrine-C14-N15 show that the amino nitrogen is incorporated directly into the thioglucoside. Evidence that indicates that D-γ-phenylbutyrine is converted to its L-isomer by the plant is also presented. The results of an isotope competition experiment provide some evidence for the existence of a chain-lengthening pathway (analogous to the formation of leucine from valine) for the biosynthesis of γ-phenylbutyrine from phenylalanine and acetate in watercress.

BIOSYNTHESIS OF MUSTARD OIL GLUCOSIDES: I. ADMINISTRATION OF C14-LABELLED COMPOUNDS TO HORSERADISH, NASTURTIUM, AND WATERCRESS

1962 ◽  
Vol 40 (1) ◽  
pp. 1505-1514 ◽  
Author(s):  
E. W. Underhill ◽  
M. D. Chisholm ◽  
L. R. Wetter
Keyword(s):  
Allyl Isothiocyanate ◽  
The Other ◽  
Mustard Oil ◽  
Methyl Carbon ◽  
Nasturtium Officinale ◽  
Other Hand ◽  
Tropaeolum Majus ◽  
Armoracia Lapathifolia ◽  
Carboxyl Carbon

Biosynthetic investigations with C14-labelled compounds indicate that the aromatic isothiocyanate moieties of mustard oil glucosides obtained from garden nasturtium (Tropaeolum majus L.) and watercress (Nasturtium officinale R.Br.) are derived from phenylalanine. Similar investigations on sinigrin, the mustard oil glucoside isolated from horseradish (Armoracia lapathifolia Gilib.) demonstrate that glycine is incorporated into allyl isothiocyanate. The methyl carbon of acetate was readily incorporated into sinigrin and gluconasturtium and was found almost exclusively in the 'isothiocyanate carbon'; on the other hand the carboxyl carbon is a poor precursor of sinigrin.

BIOSYNTHESIS OF MUSTARD OIL GLUCOSIDES: VI. BIOSYNTHESIS OF GLUCOBARBARIN IN RESEDA LUTEOLA L.

1965 ◽  
Vol 43 (2) ◽  
pp. 189-198 ◽  
Author(s):  
E. W. Underhill
Keyword(s):  
Specific Activity ◽  
Mustard Oil ◽  
Keto Acid ◽  
Carbon 14 ◽  
Acid Analogue ◽  
Phenylbutyric Acid ◽  
Carboxyl Carbon

A number of C14-labelled compounds were fed to Reseda luteola L.; after a 24-hour period of metabolism, the thioglucoside aglycone (5-phenyl-2-oxazolidinethione) was isolated and its specific activity determined. In some instances the aglycone was degraded to determine the distribution of C14.DL-γ-Phenylbutyrine (2-amino-4-phenylbutyric acid) was the most efficient precursor of the aglycone, followed by phenylalanine and acetate; the carboxyl carbon of these compounds was not incorporated into the thioglucoside aglycone. Little or no randomization of C14 in the aglycone resulted from feeding DL-γ-phenylbutyrine-2- and -3-C14, DL-phenylalanine-2- and -3-C14, and acetate-2-C14. The conversion of C14 from 10 additional compounds into the aglycone was less than that from D-glucose-G-C14. Isotope competition experiments suggest that β-benzylmalic acid also may be a precursor. It appears that the C6–C3 aglycone is formed from phenylalanine and acetate via C6–C5 and C6–C4 intermediates (including γ-phenylbutyrine or its keto acid analogue) in a manner analogous to the formation of gluconasturtiin in watercress. The carbon-14 and nitrogen-15 of L-phenylalanine-G-C14-N15 and of DL-γ-phenylbutyrine-2-C14-N15 were not incorporated as a unit into the aglycone of glucobarbarin.

BIOSYNTHESIS OF MUSTARD OIL GLUCOSIDES: I. ADMINISTRATION OF C14-LABELLED COMPOUNDS TO HORSERADISH, NASTURTIUM, AND WATERCRESS

1962 ◽  
Vol 40 (11) ◽  
pp. 1505-1514 ◽  
Author(s):  
E. W. Underhill ◽  
M. D. Chisholm ◽  
L. R. Wetter
Keyword(s):  
Allyl Isothiocyanate ◽  
The Other ◽  
Mustard Oil ◽  
Methyl Carbon ◽  
Nasturtium Officinale ◽  
Other Hand ◽  
Tropaeolum Majus ◽  
Armoracia Lapathifolia ◽  
Carboxyl Carbon

Biosynthetic investigations with C14-labelled compounds indicate that the aromatic isothiocyanate moieties of mustard oil glucosides obtained from garden nasturtium (Tropaeolum majus L.) and watercress (Nasturtium officinale R.Br.) are derived from phenylalanine. Similar investigations on sinigrin, the mustard oil glucoside isolated from horseradish (Armoracia lapathifolia Gilib.) demonstrate that glycine is incorporated into allyl isothiocyanate. The methyl carbon of acetate was readily incorporated into sinigrin and gluconasturtium and was found almost exclusively in the 'isothiocyanate carbon'; on the other hand the carboxyl carbon is a poor precursor of sinigrin.

Microcalorimeters for X-Ray Spectroscopy

1988 ◽  
Vol 102 ◽  
pp. 41
Author(s):  
E. Silver ◽  
C. Hailey ◽  
S. Labov ◽  
N. Madden ◽  
D. Landis ◽  
...  
Keyword(s):  
High Resolution ◽  
High Efficiency ◽  
Thermal Response ◽  
Low Noise ◽  
High Resolution Spectroscopy ◽  
Superconducting Transition ◽  
Sapphire Substrates ◽  
Laboratory Plasmas ◽  
Adiabatic Demagnetization ◽  
Theoretical Predictions

The merits of microcalorimetry below 1°K for high resolution spectroscopy has become widely recognized on theoretical grounds. By combining the high efficiency, broadband spectral sensitivity of traditional photoelectric detectors with the high resolution capabilities characteristic of dispersive spectrometers, the microcalorimeter could potentially revolutionize spectroscopic measurements of astrophysical and laboratory plasmas. In actuality, however, the performance of prototype instruments has fallen short of theoretical predictions and practical detectors are still unavailable for use as laboratory and space-based instruments. These issues are currently being addressed by the new collaborative initiative between LLNL, LBL, U.C.I., U.C.B., and U.C.D.. Microcalorimeters of various types are being developed and tested at temperatures of 1.4, 0.3, and 0.1°K. These include monolithic devices made from NTD Germanium and composite configurations using sapphire substrates with temperature sensors fabricated from NTD Germanium, evaporative films of Germanium-Gold alloy, or material with superconducting transition edges. A new approache to low noise pulse counting electronics has been developed that allows the ultimate speed of the device to be determined solely by the detector thermal response and geometry. Our laboratory studies of the thermal and resistive properties of these and other candidate materials should enable us to characterize the pulse shape and subsequently predict the ultimate performance. We are building a compact adiabatic demagnetization refrigerator for conveniently reaching 0.1°K in the laboratory and for use in future satellite-borne missions. A description of this instrument together with results from our most recent experiments will be presented.

Imaging and diffraction modes in Scanning Transmission Electron Microscopy

1986 ◽  
Vol 44 ◽  
pp. 684-687
Author(s):  
J. M. Cowley ◽  
R. Glaisher ◽  
J. A. Lin ◽  
H.-J. Ou
Keyword(s):  
Scanning Transmission Electron Microscopy ◽  
High Efficiency ◽  
Fiber Optic ◽  
Image Intensifier ◽  
Detector System ◽  
Detector Plane ◽  
Secondary Electrons ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Special Detector

Some of the most important applications of STEM depend on the variety of imaging and diffraction made possible by the versatility of the detector system and the serial nature, of the image acquisition. A special detector system, previously described, has been added to our STEM instrument to allow us to take full advantage of this versatility. In this, the diffraction pattern in the detector plane may be formed on either of two phosphor screens, one with P47 (very fast) phosphor and the other with P20 (high efficiency) phosphor. The light from the phosphor is conveyed through a fiber-optic rod to an image intensifier and TV system and may be photographed, recorded on videotape, or stored digitally on a frame store. The P47 screen has a hole through it to allow electrons to enter a Gatan EELS spectrometer. Recently a modified SEM detector has been added so that high resolution (10Å) imaging with secondary electrons may be used in conjunction with other modes.

Influence of MBE Growth Conditions on Dislocation Densities of GaAs/Ge Epilayers Grown on Silicon Substrates

1985 ◽  
Vol 43 ◽  
pp. 364-365
Author(s):  
K.M. Hones ◽  
P. Sheldon ◽  
B.G. Yacobi ◽  
A. Mason
Keyword(s):  
High Efficiency ◽  
Lattice Mismatch ◽  
Low Cost ◽  
Growth Conditions ◽  
Nonradiative Recombination ◽  
Device Structure ◽  
Si Substrates ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Dislocation Type

There is increasing interest in growing epitaxial GaAs on Si substrates. Such a device structure would allow low-cost substrates to be used for high-efficiency cascade- junction solar cells. However, high-defect densities may result from the large lattice mismatch (∼4%) between the GaAs epilayer and the silicon substrate. These defects can act as nonradiative recombination centers that can degrade the optical and electrical properties of the epitaxially grown GaAs. For this reason, it is important to optimize epilayer growth conditions in order to minimize resulting dislocation densities. The purpose of this paper is to provide an indication of the quality of the epitaxially grown GaAs layers by using transmission electron microscopy (TEM) to examine dislocation type and density as a function of various growth conditions. In this study an intermediate Ge layer was used to avoid nucleation difficulties observed for GaAs growth directly on Si substrates. GaAs/Ge epilayers were grown by molecular beam epitaxy (MBE) on Si substrates in a manner similar to that described previously.

The use of high-resolution FESEM to study solid-state phase transformations and reactions

1994 ◽  
Vol 52 ◽  
pp. 1028-1029
Author(s):  
P. G. Kotula ◽  
D. D. Erickson ◽  
C. B. Carter
Keyword(s):  
Solid State ◽  
High Resolution ◽  
Phase Transformations ◽  
High Efficiency ◽  
Sol Gel ◽  
Quantitative Information ◽  
Solid State Reactions ◽  
Critical Dimensions ◽  
Backscattered Electrons ◽  
Backscattered Electron

High-resolution field-emission-gun scanning electron microscopy (FESEM) has recently emerged as an extremely powerful method for characterizing the micro- or nanostructure of materials. The development of high efficiency backscattered-electron detectors has increased the resolution attainable with backscattered-electrons to almost that attainable with secondary-electrons. This increased resolution allows backscattered-electron imaging to be utilized to study materials once possible only by TEM. In addition to providing quantitative information, such as critical dimensions, SEM is more statistically representative. That is, the amount of material that can be sampled with SEM for a given measurement is many orders of magnitude greater than that with TEM.In the present work, a Hitachi S-900 FESEM (operating at 5kV) equipped with a high-resolution backscattered electron detector, has been used to study the α-Fe2O3 enhanced or seeded solid-state phase transformations of sol-gel alumina and solid-state reactions in the NiO/α-Al2O3 system. In both cases, a thin-film cross-section approach has been developed to facilitate the investigation. Specifically, the FESEM allows transformed- or reaction-layer thicknesses along interfaces that are millimeters in length to be measured with a resolution of better than 10nm.

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