scholarly journals Mutation of aspartic acid residues in the fructosyltransferase of Streptococcus salivarius ATCC 25975

1999 ◽  
Vol 344 (1) ◽  
pp. 259-264 ◽  
Author(s):  
Donna D. SONG ◽  
Nicholas A. JACQUES
Keyword(s):  
Emission Spectra ◽  
Activity Analysis ◽  
Published Data ◽  
Streptococcus Salivarius ◽  
Plant Family ◽  
Sucrose Hydrolysis ◽  
Structure Comparison ◽  
The One ◽  
Enzyme Intermediate ◽  
Tryptophan Emission

The site-directed mutated fructosyltransferases (Ftfs) of Streptococcus salivarius ATCC 25975, D312E, D312S, D312N and D312K were all active at 37 °C, indicating that Asp-312 present in the ‘sucrose box’ was not the nucleophilic Asp residue responsible for the formation of a covalent fructosyl-enzyme intermediate required for enzyme activity. Analysis of the kinetic constants of the purified mutated forms of the enzyme showed that Asp-312 was most likely an essential amino acid involved in determining acceptor recognition and/or stabilizing a β-turn in the protein. In contrast, when the Asp-397 of the Ftf present in the conserved triplet RDP motif of all 60 bacterial and plant family-32 glycosylhydrolases was mutated to a Ser residue, both sucrose hydrolysis and polymerization ceased. Tryptophan emission spectra confirmed that this mutation did not alter protein structure. Comparison of published data from other site-directed mutated enzymes implicated the Asp residue in the RDP motif as the one that may form a transient covalent fructosyl intermediate during the catalysis of sucrose by the Ftf of S. salivarius.

Parasites of round goby, Neogobius melanostomus, currently invading the Elbe River

2019 ◽  
Vol 48 (1) ◽  
pp. 56-65 ◽  
Author(s):  
Yuriy Kvach ◽  
Markéta Ondračková ◽  
Michal Janáč ◽  
Vadym Krasnovyd ◽  
Mária Seifertová ◽  
...  
Keyword(s):  
Round Goby ◽  
Parasite Community ◽  
Neogobius Melanostomus ◽  
Published Data ◽  
Tidal Zone ◽  
New Host ◽  
The North ◽  
Round Gobies ◽  
The Elbe River ◽  
The One

Abstract The round goby, Neogobius melanostomus, is a Ponto-Caspian fish species currently found in many parts of Europe, including the North Sea riverine deltas. The objective of this study was to examine the parasite community of fish caught in the lower Elbe (Süderelbe – tidal zone; Geesthacht – non-tidal) in Germany and compare it with published data from the upper Elbe (Ústí nad Labem) in the Czech Republic. Twelve parasite taxa were recorded in the lower Elbe, six in the Süderelbe and nine near the city of Geesthacht. Süderelbe fish were mainly infected with Angullicola crassus larvae, while gobies from Geesthacht – with glochidia and sporadically occurring Pomporhynchus laevis, and the opposite situation was observed at Ústí nad Labem. It appears that a large tidal weir at Geesthacht significantly contributes to the division of the round goby population, with the Geesthacht parasite community being more similar to that at Ústí nad Labem than the one from the Süderelbe, thus increasing the likelihood that shipping from Hamburg was the introduction vector to Ústí nad Labem. We also recorded Acanthocephalus rhinensis in the Elbe for the first time, and in a new host – the round goby. Thus, round gobies may represent a new vector for the introduction of this parasite along the Elbe.

Recursive density equivalents: an improved method for forecasting yield loss caused by mixed weed populations

2005 ◽  
Vol 143 (4) ◽  
pp. 293-298 ◽  
Author(s):  
N. HOLST
Keyword(s):  
Yield Loss ◽  
Published Data ◽  
Improved Method ◽  
Seedling Density ◽  
Weed Species ◽  
New Model ◽  
Hyperbolic Curve ◽  
Theoretical Paper ◽  
The One ◽  
Crop Weed Competition

Simple models that can forecast yield loss from weed seedling density at crop emergence are useful tools for both research and practice. In 1985 Cousens presented the rectangular hyperbolic curve as a solution to this problem for the one-weed species case (Cousens 1985a). To address the multi-weed species case, the present theoretical paper investigates two published models and develops a third model, termed ‘recursive density equivalents’. The models were analysed and evaluated based on their biological rationale and using already published data. The earlier models were both found to rely on biologically unrealistic assumptions. The new model avoided additional assumptions, providing a neutral method of summarizing the Cousens curves for many species. Recursive density equivalents were found to be additive in a more intuitive fashion than the ‘density equivalents’ introduced earlier. An over-estimation bias was found to be inherent in the earlier density equivalents model, increasing with species richness. The new model corrected for this bias when checked against one year's field data but for another year, both models over-estimated markedly. All three models were found to be too simple to accommodate all possible modes of intra- and inter-specific competition, yet the new model is an improvement, as it agrees better with the biological principles of crop-weed competition.

Coulomb's Data on Harpsichord Wire

MRS Bulletin ◽  
1992 ◽  
Vol 17 (1) ◽  
pp. 24-27 ◽  
Author(s):  
Martha Goodway ◽  
William R. Savage
Keyword(s):  
18Th Century ◽  
Published Data ◽  
Torsion Pendulum ◽  
Late 18Th Century ◽  
Baroque Music ◽  
Degree Of Confidence ◽  
The Wire ◽  
Strength And Stiffness ◽  
The One ◽  
Brass Wire

Charles-Augustin Coulomb published data on the size, strength, and stiffness of harpsichord wire available in Paris in the late 18th century which has not been cited in the literature on musical instruments despite this century's revival of baroque music and the instruments upon which it was played. During an investigation of the internal friction of several antique music wires by means of a torsion pendulum similar to the one invented by Coulomb and first described in the 1784 mémoire (Figure 1), it occurred to us to ask what Coulomb had used as the suspensions in his pendulum. His biographer, C.S. Gillmor, mentioned “harpsichord strings”, and in Coulomb's 1784 Torsion mémoire we found: J'ai pris trois fils de clavcin, tels qu'on les trouve répandus dans le commerce, roulés sur des bobines, et numerotés (“I used three harpsicord wires, such as one finds distributed in commerce, wound up on spools, and numbered”).The spools of wire recently discovered in the stand drawer of a harpsichord in France fit Coulomb's description. The instrument was built in Paris in 1732 by Antoine Vater, and the wire found with it was wound up on small wooden spools similar to spools for thread. The spool of red brass wire had a mark punched in one end and the spool of iron wire had the gauge size (No 5) written on it in ink, while the spool of yellow brass wire had neither mark nor number. Samples of the wires from these three spools, generally agreed to be of 18th century manufacture, were collected by J. Scott Odell of the Smithsonian Institution as part of a research project which he initiated into the physical properties of antique wire. With these samples in hand it was possible to measure certain of their properties and to compare these properties with those reported in Coulomb's Torsion mémoire in 1784. Since Coulomb's wire was undoubtedly of 18th century manufacture (a degree of confidence that we do not always have with collected samples), and the data were taken not long after the wire was drawn, comparison with the Vater wire allows us to detect if, during two centuries, significant changes occur in highly drawn wire.

scholarly journals Purification and enzymic properties of the fructosyltransferase of Streptococcus salivarius ATCC 25975

1999 ◽  
Vol 341 (2) ◽  
pp. 285-291 ◽  
Author(s):  
Donna D. SONG ◽  
Nicholas A. JACQUES
Keyword(s):  
Escherichia Coli ◽  
Signal Sequence ◽  
Gel Filtration ◽  
Maximum Activity ◽  
Streptococcus Salivarius ◽  
Acetobacter Diazotrophicus ◽  
E Coli ◽  
Ping Pong ◽  
Mechanism Of Catalysis ◽  
Enzyme Intermediate

The recombinant fructosyltransferase (Ftf) of Streptococcus salivarius was expressed in Escherichia coli and purified to electrophoretic homogeneity after a combination of adsorption, ion-exchange and gel-filtration chromatography. The N-terminal signal sequence of the Ftf was removed by E. coli at the same site as in its natural host. The purified Ftf exhibited maximum activity at pH 6.0 and 37 °C, was activated by Ca2+, but inhibited by the metal ions Cu2+, Zn2+, Hg2+ and Fe3+. The enzyme catalysed the transfer of the fructosyl moiety of sucrose to a number of acceptors, including water, glucose and sucrose via a Ping Pong mechanism involving a fructosyl-enzyme intermediate. While this mechanism of catalysis is utilized by the levansucrases of Bacillus subtilis and Acetobacter diazotrophicus and the values of the kinetic constants for the three enzymes are similar, sucrose was a far more efficient fructosyl-acceptor for the Ftf of S. salivarius than for the two other enzymes.

scholarly journals Professional consciousness as a factor in the regulation of the professional activity of atterneys

2018 ◽  
Vol 28 (4) ◽  
pp. 27-30
Author(s):  
O.A. Hulbs ◽  
O.V. Kobets
Keyword(s):  
Human Rights ◽  
Law Enforcement ◽  
System Analysis ◽  
Activity Analysis ◽  
Professional Activity ◽  
System Activity ◽  
Psychological Analysis ◽  
Mechanism Of Interaction ◽  
Psychological Mechanism ◽  
The One

In that article is considered the professional consciousness and its development in the activity of attorney. It was opening the psychological analysis of the special advocate’s activity. The professional consciousness of advocate is characterized like an insight intellectual subject’s model, in what from the one hand describes the sense of the law norms of society, and from another hand is formed the programs purposeful law’s executive activity. In the professional consciousness of the personality of the attorney are connected display and regulatory areas of the psyche. The psychological mechanism of interaction of the reflective (theoretical) sphere of professional consciousness with its regulatory sphere is extremely complicated, but it is revealed through the methods of system analysis. One example of the use of system-activity analysis can serve as the theory of phased formation of mental activities (P. Ya Halperin). The use of this method allows deeper to reveal the stages of development of professional consciousness of the attorney’s personality. The professional activity of an attorney is characterized by an extraordinary variety of solvable tasks. This activity is primarily related to the norms of law, and some of its types contain the following concepts: law enforcement activities, human rights activities, and so on. In that article is considered the professional consciousness and its development in the activity of attorney. It was opening the psychological analysis of the special advocate’s activity. The professional consciousness of advocate is characterized like an insight intellectual subject’s model, in what from the one hand describes the sense of the law norms of society, and from another hand is formed the programs purposeful law’s executive activity. In the professional consciousness of the personality of the attorney are connected display and regulatory areas of the psyche. The psychological mechanism of interaction of the reflective (theoretical) sphere of professional consciousness with its regulatory sphere is extremely complicated, but it is revealed through the methods of system analysis. One example of the use of system-activity analysis can serve as the theory of phased formation of mental activities (P. Ya Halperin). The use of this method allows deeper to reveal the stages of development of professional consciousness of the attorney’s personality. The professional activity of an attorney is characterized by an extraordinary variety of solvable tasks. This activity is primarily related to the norms of law, and some of its types contain the following concepts: law enforcement activities, human rights activities, and so on.

scholarly journals Синтез наноразмерных люминофоров Gd-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-:Nd-=SUP=-3+-=/SUP=- полимерно-солевым методом и исследование их основных характеристик

2021 ◽  
Vol 129 (5) ◽  
pp. 650
Author(s):  
А.С. Матросова ◽  
Н.К. Кузьменко ◽  
C.К. Евстропьев ◽  
В.А. Асеев ◽  
Д.П. Данилович ◽  
...  
Keyword(s):  
Thermal Treatment ◽  
Near Infrared ◽  
Homogeneous Solution ◽  
Emission Spectra ◽  
Electron Transition ◽  
Liquid Polymer ◽  
Electron Transitions ◽  
Luminescence Peak ◽  
The One ◽  
Average Size

The article considers the aspects of nanoscale Gd2O3:Nd3+ phosphors synthesis using the liquid polymer-salt method. Within the framework of the method, the double role of polyvinylpyrrolidone (PVP) as an organic solvent in the process of synthesis was determined. On the one hand, PVP stabilizes the process of Gd2O3 crystals formation, preventing their uncontrolled growth and aggregation. On the other hand, PVP serves as a fuel during decomposition (combustion) increasing the temperature of reaction and thus influencing the structural and emission properties of phosphors. It is shown that drying of the initial homogeneous solution containing gadolinium and neodymium salts and PVP at the room temperature for 24 hours followed by thermal treatment at the temperature of 1000 °C for 2 hours allow formation of highly luminescent Gd2O3:Nd3+ near-infrared phosphors. The crystals grown are characterized mainly by the cubic structure and an average size of 40 nm. Experimental results confirmed that the developed method is appropriate for modification of a structure of silica hollow-core antiresonant fibers with thin-film coatings based on the synthesized material and does not result in structural and phase conversion of Gd2O3 crystals. It is found out that emission spectra of nanoscale Gd2O3:Nd3+ phosphors formed by the polymer-salt method at the temperatures of 550 °C and 1000 °C are identical, as follows: 1) the shape of the luminescence peaks is the same for the two mentioned regimes of thermal treatment regardless of intensity, 2) the main luminescence peak is located near the wavelength of 1064 nm and corresponds to a 4F3/2-4I11/2 electron transition, 3) additional luminescence peaks are located close to 900 nm and 1340 nm and refer to 4F3/2-4I9/2 and 4F3/2-4I13/2 electron transitions respectively.

scholarly journals Eco Friendly Synthesis of Carbon Dot by Hydrothermal Method for Metal Ions Salt Identification

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7604
Author(s):  
Hasan Shabbir ◽  
Tomasz Tokarski ◽  
Ditta Ungor ◽  
Marek Wojnicki
Keyword(s):  
Metal Ion ◽  
Hydrothermal Reaction ◽  
Synthesis Method ◽  
Emission Spectra ◽  
Carbon Quantum Dots ◽  
Photoluminescence Properties ◽  
Step Method ◽  
Synthesis Time ◽  
One Step ◽  
The One

In this work, we report the synthesis method of carbon quantum dots (CDs) using the one-step method for fast and effective metal ion determination. Ascorbic acid was used as an inexpensive and environmentally friendly precursor. High-pressure and high-temperature reactors were used for this purpose. Microscopic characterization revealed the size of CDs was in the range of 2–6 nm and they had an ordered structure. The photoluminescence properties of the CDs depend on the process temperature, and we obtained the highest PL spectra for 6 h of hydrothermal reaction. The maximum emission spectra depend poorly on synthesis time. Further characterization shows that CDs are a good contender for sensing Fe3+ in aqueous systems and can detect concentrations up to 0.49 ppm. The emission spectra efficiency was enhanced by up to 200% with synthesis time.

Ixodes inopinatus and Ixodes ricinus (Acari: Ixodidae) Are Sympatric Ticks in North Africa

2019 ◽  
Vol 57 (3) ◽  
pp. 952-956 ◽  
Author(s):  
Hend Younsi ◽  
Wasfi Fares ◽  
Saifedine Cherni ◽  
Khalil Dachraoui ◽  
Walid Barhoumi ◽  
...  
Keyword(s):  
Ixodes Ricinus ◽  
North Africa ◽  
Morphological Characters ◽  
Published Data ◽  
Northern Tunisia ◽  
Humid Area ◽  
Ixodes Ticks ◽  
The One ◽  
Rrna Sequences ◽  
16S Rrna Sequences

Abstract In the present study, we report the sympatric occurrence of Ixodes ricinus (Linnaeus, 1758) and Ixodes inopinatus (Estrada-Peña, Nava, and Petney, 2014) in Tunisia. In total, 173 adult Ixodes ticks were collected from four sites (El Jouza, Tamra, Aïn Soltan, and Jbel Zaghouan) between February and April 2017, a period corresponding to the peak of activity of I. ricinus in North Africa. The morphological characters corresponded to both species; thus, we generated a total of 28 16S rRNA sequences and compared them with previously published data in GenBank. The two species were sympatric in Tamra, Aïn Soltan, and El Jouza, whereas collections in Jbel Zaghouan only yielded I. inopinatus. These results indicate that the two taxa are widespread in the humid area of northern Tunisia. The one tick collected in Jbel Zaghouan suggests that the distribution of at least I. inopinatus might extend to the sub-humid area. More studies are needed to fully comprehend the systematic status of the two taxonomic entities using multiple molecular markers and morphological characters; integrating these two identification methods are a necessary step toward a better understanding of the ecology and epidemiology of tick-borne diseases in Tunisia.

The relationship between optical properties and occurrence of some black tourmalines from Northern Nigeria

1971 ◽  
Vol 38 (295) ◽  
pp. 369-373 ◽  
Author(s):  
Patricia McCurry
Keyword(s):  
Close Correlation ◽  
Published Data ◽  
Northern Nigeria ◽  
Total Iron Content ◽  
Geochemical Environment ◽  
Apparent Lack ◽  
Upper Proterozoic ◽  
Lower Palaeozoic ◽  
The One ◽  
The Relationship

SummarySeventy-nine black tourmalines collected over a 12 000 km2 area of Precambrian to lower Palaeozoic rocks in northern Nigeria show a close correlation between maximum R.I., absorption colour, and occurrence in non-feldspathic micaceous schists and schorl rocks on the one hand, and in gneisses, migmatites, and feldspathic pegmatites on the other. Pleochroism is known to depend upon the total iron content and the Fe2+Fe3+ interaction. Colour variations may thus provide useful indicators of the geochemical environment during crystallization.Limited published data, supplemented by additional measurements on four tourmalines from outside the original area, suggest that similar correlations would be obtained for the rest of Nigeria.Selective processes of boron metasomatism may have been important in the association of different coloured tourmalines with feldspathic and non-feldspathic rocks, and the apparent lack of biotite in most tourmaline-rich rocks. The source of the boron probably lay within the upper Proterozoic to lower Palaeozoic metasedimentary belts with which the tourmaline is most strongly associated.

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