scholarly journals Regiospecificty in the heterocyclization of β-oxonitriles to 5-substituted 4-oxothiazolidine derivatives

2003 ◽  
Vol 68 (4-5) ◽  
pp. 383-390 ◽  
Author(s):  
Rade Markovic ◽  
Zdravko Dzambaski ◽  
Milovan Stojanovic ◽  
Peter Steel ◽  
Marija Baranac
Keyword(s):  
Experimental Evidence ◽  
Reasonable Explanation ◽  
Theoretical Considerations ◽  
Derivatives Of

Astudy on the regiospecificity of the base-catalyzed reaction of activated ?-oxonitriles 1 with diethyl mercaptosuccinate affording the title compounds 3 is reported. Other competitive heterocyclic products, that is 4-oxo-1,3-thiazinanes 4, derivatives of tetrahydrothiophene 5 and/or thiacyclohexane 6 which on the grounds of mechanistic considerations could be formed, were not observed. Spectroscopic and experimental evidence together with theoretical considerations, provides a reasonable explanation for the observed regiospecificity.

scholarly journals Experimental evidence for friction-enhancing integumentary modifications of chameleons and associated functional and evolutionary implications

2014 ◽  
Vol 281 (1775) ◽  
pp. 20132334 ◽  
Author(s):  
Eraqi R. Khannoon ◽  
Thomas Endlein ◽  
Anthony P. Russell ◽  
Kellar Autumn
Keyword(s):  
Experimental Evidence ◽  
Frictional Coefficient ◽  
Force Transducer ◽  
Morphological Convergence ◽  
Functional Implications ◽  
Smooth Skin ◽  
Derivatives Of

The striking morphological convergence of hair-like integumentary derivatives of lizards and arthropods (spiders and insects) demonstrates the importance of such features for enhancing purchase on the locomotor substrate. These pilose structures are responsible for the unique tractive abilities of these groups of animals, enabling them to move with seeming ease on overhanging and inverted surfaces, and to traverse inclined smooth substrates. Three groups of lizards are well known for bearing adhesion-promoting setae on their digits: geckos, anoles and skinks. Similar features are also found on the ventral subdigital and distal caudal skin of chameleons. These have only recently been described in any detail, and structurally and functionally are much less well understood than are the setae of geckos and anoles. The seta-like structures of chameleons are not branched (a characteristic of many geckos), nor do they terminate in spatulate tips (which is characteristic of geckos, anoles and skinks). They are densely packed and have attenuated blunt, globose tips or broad, blade-like shafts that are flattened for much of their length. Using a force transducer, we tested the hypothesis that these structures enhance friction and demonstrate that the pilose skin has a greater frictional coefficient than does the smooth skin of these animals. Our results are consistent with friction being generated as a result of side contact of the integumentary filaments. We discuss the evolutionary and functional implications of these seta-like structures in comparison with those typical of other lizard groups and with the properties of seta-mimicking synthetic structures.

Adamantylsulfanyl- andN-Adamantylcarboxamido-Derivatives of Heterocycles and Phenoles: Synthesis, Crystal Structure, Tumor Necrosis Factor-αProduction-Enhancing Properties, and Theoretical Considerations

2004 ◽  
Vol 1 (10) ◽  
pp. 1498-1512 ◽  
Author(s):  
Jan Krzysztof Maurin ◽  
Witold Lasek ◽  
Agata Górska ◽  
Tomasz Świtaj ◽  
Anna Beata Jakubowska ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Tumor Necrosis Factor ◽  
Tumor Necrosis ◽  
Theoretical Considerations ◽  
Derivatives Of ◽  
Necrosis Factor

Mechanisms of calcium disposal from osteoclastic resorption hemivacuole

2003 ◽  
Vol 176 (1) ◽  
pp. 1-5 ◽  
Author(s):  
HK Datta ◽  
BR Horrocks
Keyword(s):  
Protein Degradation ◽  
Experimental Evidence ◽  
Matrix Protein ◽  
Degradation Products ◽  
Transcellular Transport ◽  
Osteoclastic Resorption ◽  
Osteoclast Function ◽  
Theoretical Considerations ◽  
Simple Link

One of the most remarkable but neglected aspects of osteoclast function is its unique adaptation that allows the cell to function despite its resorbing surface being exposed to extremely high levels of ambient Ca2+. Recently our studies have provided evidence of continuous transcellular Ca2+ disposal, suggesting that osteoclasts are able to prevent Ca2+ accumulation within the resorptive hemivacuole. It has also been shown that matrix protein degradation products that accumulate within the osteoclast resorptive vacuole are also undergoing transcellular transport by transcytosis. However, both experimental evidence and theoretical considerations suggest that transcellular transport of Ca2+ and matrix protein is likely to occur via distinct routes. In light of these considerations, we are able to provide convincing explanations for the apparent anomalies of osteoclast intracellular [Ca2+] responses to a variety of endocrine stimuli. The understanding of the mechanisms involved in Ca2+ handling by osteoclasts indicates the lack of a simple link between osteoclast function and changes in overall cytosolic [Ca2+].

scholarly journals The quantitative determination of glycosaminoglycans in urine with Alcian Blue 8GX

1973 ◽  
Vol 131 (2) ◽  
pp. 351-357 ◽  
Author(s):  
P. Whiteman
Keyword(s):  
Quantitative Determination ◽  
Experimental Evidence ◽  
Alcian Blue ◽  
Preceding Paper ◽  
Mgcl2 Concentration ◽  
Theoretical Considerations ◽  
Urinary Glycosaminoglycans

1. The effect of MgCl2 concentration on the interaction of Alcian Blue 8GX and glycosaminoglycans in the urine of patients with mucopolysaccharidosis was studied by using a new quantitative micro method for the measurement of Alcian Blue–glycosaminoglycan complexes. This provided a means of measuring the critical electrolyte concentrations of urinary glycosaminoglycans. 2. Theoretical considerations based on the preceding paper (Whiteman, 1973) and experimental evidence provided here show that Alcian Blue 8GX may be used for the direct quantitative determination of total urinary glycosaminoglycans. The method is simple, requires sample volumes of 50μl or less, and gives results comparable with those obtained by other more complicated methods.

Fullerenes

MRS Bulletin ◽  
1994 ◽  
Vol 19 (11) ◽  
pp. 21-21
Author(s):  
C.N.R. Rao ◽  
Eiji Ōsawa
Keyword(s):  
Metal Carbides ◽  
Personal Account ◽  
Materials Properties ◽  
Carbon Structures ◽  
Important Landmark ◽  
Carbon Molecules ◽  
Arc Evaporation ◽  
Theoretical Considerations ◽  
Derivatives Of ◽  
High Temperature Super Conductivity

Although C60 and other such molecules had been predicted earlier on the basis of theoretical considerations, the identification of these molecules by mass spectrometry in the year 1985 is an important landmark. The discovery of a ready method of preparation by arc evaporation of graphite in 1990 gave a big boost to this area of research. Today, research on carbon has undergone a renaissance and the new carbon molecules and structures probably constitute the second greatest sensation in physical science since the 1986 discovery of high-temperature super-conductivity in cuprates.These fascinating cage molecules of carbon, containing 6- and 5-membered rings, with considerable pi electron density, exhibit interesting chemical as well as materials properties. The phase transitionh of fullerenes and the electronic properties of the derivatives of C60 are indeed interesting. And, as if this were not enough, many other novel carbon structures have recently been discovered. Nanotubes are a major discovery. Closed on either end, nanotubes can be opened by mild oxidation at the reactive site at the closed end and can be filled with metals. Carbon onions made of concentric giant fullerenes constitute another interesting form of carbon. The onions have also been stuffed with metals and metal carbides. Clearly, carbon research has many surprises in store, with promising applications. It is only appropriate that the MRS Bulletin has dedicated a special issue to the new carbon structures and we are happy to serve as guest editors, presenting a wide variety of topics that convey the flavor of this fascinating field. We begin with a personal account of Buckminsterfullerene by co-guest editor Harry Kroto.

scholarly journals Energy Substrates for Neurons during Neural Activity: A Critical Review of the Astrocyte-Neuron Lactate Shuttle Hypothesis

2003 ◽  
Vol 23 (11) ◽  
pp. 1263-1281 ◽  
Author(s):  
Ching-Ping Chih ◽  
Eugene L Roberts
Keyword(s):  
Glucose Metabolism ◽  
Experimental Evidence ◽  
Neural Activity ◽  
Critical Review ◽  
Theoretical Background ◽  
Anaerobic Glycolysis ◽  
Energy Substrates ◽  
Lactate Shuttle ◽  
Theoretical Considerations ◽  
Primary Substrate

Glucose had long been thought to fuel oxidative metabolism in active neurons until the recently proposed astrocyte-neuron lactate shuttle hypothesis (ANLSH) challenged this view. According to the ANLSH, activity-induced uptake of glucose takes place predominantly in astrocytes, which metabolize glucose anaerobically. Lactate produced from anaerobic glycolysis in astrocytes is then released from astrocytes and provides the primary metabolic fuel for neurons. The conventional hypothesis asserts that glucose is the primary substrate for both neurons and astrocytes during neural activity and that lactate produced during activity is removed mainly after neural activity. The conventional hypothesis does not assign any particular fraction of glucose metabolism to the aerobic or anaerobic pathways. In this review, the authors discuss the theoretical background and critically review the experimental evidence regarding these two hypotheses. The authors conclude that the experimental evidence for the ANLSH is weak, and that existing evidence and theoretical considerations support the conventional hypothesis.

Application of mass spectrometry to the study of prototropic equilibria in 5-substituted tetrazoles in the gas phase; experimental evidence and theoretical considerations

1983 ◽  
pp. 379-383 ◽  
Author(s):  
Anna Rażyńska ◽  
Anna Tempczyk ◽  
Edmund Maliński ◽  
Janusz Szafranek ◽  
Zbigniew Grzonka ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Experimental Evidence ◽  
Gas Phase ◽  
Theoretical Considerations
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