Synthesis and chemical behaviour of D-glucosyl esters of glutamic acid having the side-chain carboxyl group involved in the glycosidic linkage.

Simultaneous and stepwise deprotection of the fully benzylated D-glucosyl esters of 1-benzyl N-benzyloxycarbonyl- and N-tert-butyloxycarbonyl-L-glutamic acid (1 and 5, respectively) have been examined. Catalytic hydrogenation of 1 led to intramolecular aminolysis to give pyroglutamic acid and D-glucose, but similar treatment in the presence of trifluoroacetic acid afforded both anomers of 1-O-(L-gamma-glutamyl)-D-glucopyranose, which were characterized as trifluoroacetates (2alpha and 2beta) and converted into 2,3,4,6-tetra-O-acetyl-1-O-[1-methyl N-(acetyl)-L-glutam-5-oyl]-D-glucopyranose (4) which was also prepared by a definitive method. Hydrogenolysis of 5 gave both anomers of 1-O-[N-(tert-butyloxycarbonyl)-L-gamma-glutamyl]-D-glucopyranose (6), which, upon treatment with trifluoroacetic acid at - 10 degrees, afforded 2alpha and 2beta, respectively. The structure of 6beta was established by its conversion into 2,3,4,6-tetra-O-acetyl-1-O-[1-methyl N-(tert-butyloxycarbonyl)-L-glutam-5-oyl]-beta-D-glucopyranose (7beta), whereas similar treatment of 6alpha gave a mixture of 1,3,4,6-tetra-O-acetyl-2-O-[1-methyl N-(tert-butyloxycarbonyl)-L-glutam-5-oyl]-alpha-D-glucopyranose (9) and 7alpha. A 1 leads to 2 acyl migration occurred during esterification of the aglycon carboxyl group of 6alpha with diazomethane to give 2-O-[1-methyl N-(tert-butyloxycarbonyl)-L-glutam-5-oyl]-alpha-D-glucopyranose (8).     

The effect of temperature and crowding on midgut amylolytic activity in Tenebrio molitor adults

The effect of two constant temperatures (23°C and 28°C), mixed group (5 + 5), and isolation on the midgut amylolytic activity during adult development of Tenebrio molitor has been investigated in vitro. Higher temperatures (28°C) and mixed groups stimulate the rate of midgut amylolytic activity. After attaining the maximal level, the amylolytic activity shows fluctuations. The possible role of hormones and primer pheromones in the control of the midgut amylolytic activity in T. molitor adults is discussed.     

A combined scanning and transmission electron microscopic study and electron probe microanalysis of human pineal acervuli

Summary Untreated, decalcified and trypsinized acervuli from human pineal bodies were studied with the scanning and transmission electron microscope as well as by electron probe microanalysis. The mulberry-like acervuli are composed of a various number of spherical lobes (135–800 m) between which clustered groups of globuli (4–14 urn in diameter) are observed. The acervular lobes are very probably formed by an aggregation of these globuli. Small round particles 125–500 Å in diameter are observed on the surface of the pineal concretions. These are not influenced by either decalcification or trypsin treatment. The acervular mineral corresponds morphologically to hydroxyapatite. The electron probe microanalysis reveals the existence of calcium and phosphorus as main components of the acervuli. Small quantities of magnesium and strontium were also detected.Dedicated to Professor Berta Scharrer on the occasion of her 70th birthdayWith the technical assistance of Mr. P.A. MilliquetThe author wishes to thank Mr. Bauer and Mr. Fryder (Nestec SA, La Tour de Peilz) for the use of the Cambridge Stereoscan electron microscope and Dr. T. Jalanti (C.M.E., Lausanne) for his help with the use of the X-ray microanalyser     

Possible mechanisms of the efflux of glutamate from kidney mitochondria generated by the activity of mitochondrial glutaminase

The transport of glutamate across the inner membrane of kidney mitochondria and the influx of glutamine into the mitochondria was studied using an oxygen electrode, the swelling technique and by continous recording of the activity of the mitochondrial glutaminase by an NH₄⁺-sensitive electrode. It is well known that the enzyme is activated by inorganic phosphate and strongly inhibited by glutamate.

1. 1. Avenaciolide, Bromocresal purple and Bromothymol blue inhibited the respiration of the mitochondria almost completely in the presence of glutamate as substrate but not in the presence of glutamine. Production of aspartate during the oxidation of glutamine was not significantly inhibited by avenaciolide but it was markedly suppressed by Bomocresol purple and Bromothymol blue.

2. 2. Swelling of kidney mitochondria in an isosmotic solution of glutamine and ammonium phosphate was not inhibited by avenaciolide or Bromocresol purple indicating that these substances do not inhibit the penetration of the mitochondrial membrane by glutamine or phosphate.

3. 3. The activity of the mitochondrial glutaminase was strongly inhibited by avenaciolide or Bromocresol purple in the presence of inhibitors of respiration or an uncoupler but not in their absence. Experimental data suggest that this was caused by the inhibition of glutamate efflux. The addition of a detergent removed this inhibition.

On the basis of these observations it was concluded that two mechanisms exist which enable glutamate to leave the inner space of kidney mitochondria: (a) an electrogenic efflux coupled to the respiration-driven proton translocation and the presence of a membrane potential (positive outside) and (b) an electroneutral glutamate-hydroxyl antiporter which is inhibited by avenaciolide and which operates in both directions. Our observations do not support the existence of the electrogenic glutamine-glutamate antiporter or glutamate-aspartate exchange in the mitochondria studied.     

The application of an averaging method to intermittently modified and endogenously generated spike activities of neurons in mollusc ganglia

The averaging method was applied for the analysis of the effect of intermittent light as well as for the analysis of the spontaneous spike activities of burster neurons in Helix pomatia and Aplysia depilans ganglia. Owing to such analyses by means of which the unwanted effects of permanently present noise (i.e., irregular frequency modulation of neuron impulse activity) were diminished, the dynamics of the neurons reaction to light and the longer time effects of intermittent illumination on neurons spontancous activity could be observed. The functional characteristics of burster neurons were determined by averaging and the least squares and equalization methods. The results were presented in the table and in two average curves which are asymmetrical with a horizontal asymptote. From these data it was concluded that the dynamics of the spontaneous activity of the two burster neurons in both specia is similar. The possibilities and limitations of the method in physiological analyses are discussed.     

Correlation of <Emphasis Type="Italic">trans</Emphasis>-Lycopene Measurements by the HPLC Method with the Optothermal and Photoacoustic Signals and the Color Readings of Fresh Tomato Homogenates

The trans-lycopene content of fresh tomato homogenates was assessed by means of the laser photoacoustic spectroscopy, the laser optothermal window, micro-Raman spectroscopy, and colorimetry; none of these methods require the extraction from the product matrix prior to the analysis. The wet chemistry method (high-performance liquid chromatography) was used as the absolute quantitative method. Analytical figures of merit for all methods were compared statistically; best linear correlation was achieved for the chromaticity index a* and chroma C*.     

Model‐assisted identification of metabolic engineering strategies for Jatropha curcas lipid pathways

Efficient approaches to increase plant lipid production are necessary to meet current industrial demands for this important resource. While Jatropha curcas cell culture can be used for in vitro lipid production, scaling up the system for industrial applications requires an understanding of how growth conditions affect lipid metabolism and yield. Here we present a bottom‐up metabolic reconstruction of J. curcas supported with labeling experiments and biomass characterization under three growth conditions. We show that the metabolic model can accurately predict growth and distribution of fluxes in cell cultures and use these findings to pinpoint energy expenditures that affect lipid biosynthesis and metabolism. In addition, by using constraint‐based modeling approaches we identify network reactions whose joint manipulation optimizes lipid production. The proposed model and computational analyses provide a stepping stone for future rational optimization of other agronomically relevant traits in J. curcas.     

A new approach for activation of the kiwifruit cysteine protease for usage in in-vitro testing

Molecular Biology Reports - Actinidin (Act d 1), a highly abundant cysteine protease from kiwifruit, is one of the major contributors to the development of kiwifruit allergy. Many studies have...     

Cytotoxic activities of Hypericum perforatum L. extracts against 2D and 3D cancer cell models

Cytotechnology - Six extracts were obtained from plant species Hypericum perforatum L., collected at Samsun in Turkey. The aim of this study was to examine the mechanisms of the anticancer activity...