Labile System Research Articles

NMR-Verified Dearomatization of 5,7-Substituted Pyrazolo[1,5-a]pyrimidines.

Tetrahydropyrazolo[1,5-a]pyrimidine (THPP) is an attractive scaffold for designing biologically active compounds. The most obvious way to obtain such compounds is to reduce pyrazolopyrimidines with complex hydrides, because the pyrimidine ring is reduced in the preference over the pyrazole ring. The presence of substituents at positions five and seven of pyrazolo[1,5-a]pyrimidines complicates the set of reaction products but makes it more attractive for medicinal chemistry because four possible stereoisomers can be formed during reduction. However, the formation of only syn-isomers has been described in the literature. This article is the first report on the formation of anti-configured isomers along with syn-isomers in the reduction of model 5,7-dimethylpyrazolo[1,5-a]pyrimidine, which was confirmed by NMR. The bicyclic core in the syn-configuration was shown to be conformationally stable, which was used to estimate the long-range interproton distances using NOESY data. At the same time, long-range dipole-dipole interactions corresponding to a distance between protons of more than 6 Å were first registered and quantified. In turn, the bicyclic core in the trans-configuration represents a conformationally labile system. For these structures, an analysis of conformations observed in solutions was carried out. Our results indicate the significant potential of trans-configured tetrahydropyrazolo[1,5-a]pyrimidines for the development of active small molecules. While possessing structural lability due to the low energy of the conformational transition, they have the ability to adjust to the active site of the desired target.

Dynamics of protein and purine metabolism parameters of ducks by age and sex

The blood composition of poultry is a labile system that reflects the activity of metabolic processes in the organism. The study of morphological and functional changes occurring in the body of ducks in postnatal ontogenesis is an urgent area and is important for breeding birds of this species, as it serves as a scientific basis for the diagnosis and prediction of various forms of pathologies. The article presents data on the age-related dynamics of metabolic parameters of blood serum in ducks of the Cherry-Veli cross. The authors determined the content of total protein, protein fractions, uric acid, creatinine in the blood serum of ducks of both sexes at the age of 3, 6, 9, 12, 15, 18, 21, 24, 30, 36, 42, 48 weeks. In each age group, 45-50 animals were examined. There is a pronounced pattern of fluctuations in protein metabolism, depending on age and gender. It has been proven that ducks have a clear age-related dynamics of protein metabolism indicators: with age, there is an increase in the content of total protein, protein fractions (albumin, α-, β- and γ-globulins), an increase in protein metabolism in the serum of females in the pre-lay period, and also at the beginning of the productive period, which is due to the mobilization of the body for the formation of egg components. The authors found that sexual dimorphism is expressed in the content of total protein albumin, α-, β- and γ-globulins, starting from puberty (from 105-126 days of age), and fluctuations in the main indicators of purine metabolism (uric acid and creatinine) in terms of age and sex expressed slightly.

Multiple evolutionary origins and losses of tooth complexity in squamates

Teeth act as tools for acquiring and processing food, thus holding a prominent role in vertebrate evolution. In mammals, dental-dietary adaptations rely on tooth complexity variations controlled by cusp number and pattern. Complexity increase through cusp addition has dominated the diversification of mammals. However, studies of Mammalia alone cannot reveal patterns of tooth complexity conserved throughout vertebrate evolution. Here, we use morphometric and phylogenetic comparative methods across fossil and extant squamates to show they also repeatedly evolved increasingly complex teeth, but with more flexibility than mammals. Since the Late Jurassic, multiple-cusped teeth evolved over 20 times independently from a single-cusped common ancestor. Squamates frequently lost cusps and evolved varied multiple-cusped morphologies at heterogeneous rates. Tooth complexity evolved in correlation with changes in plant consumption, resulting in several major increases in speciation. Complex teeth played a critical role in vertebrate evolution outside Mammalia, with squamates exemplifying a more labile system of dental-dietary evolution.

Enclathration by Werner Hosts: Selectivity and Polymorphism

The structures of six inclusion compounds with the two isomers of methylnaphthalene and the Werner host Ni(NCS)2(4-phenylpyridine)4 were determined. We report on the polymorphism and concomitant color change of the 1-methylnapthalene clathrates and the formation of a host dimer in a 2-methylnapthalene clathrate. We investigated the selectivity of the host toward an equimolar mixture of the naphthalene isomers and found that the selectivity varies from 87% 1-methylnapthalene to 54% 1-methylnapthalene with time and increasing evaporation of cosolvent, rendering a labile system.

PROJECT MANAGEMENT AND DEVELOPMENT

Determinant systems - are systems in which the state of the system can be fully identified at any time even if the implementation of a specific control act or entry leads to a false state, which can be foreseen, then such a system is defined. Namely, the determinant system is a system whose behavior is fully known. Such systems consist of the elements between which precisely defined links exist, and their interconnections are known, so that when we know the prior state and the information processing algorithm we can predict the following state of the system. Governance with defined systems implies the existence of a specific purpose and criterion of governance. With these systems we mean real-material systems that exist in a given environment. Once determined, the timing breaks down to a small or large extent, depending on the changing environment, just as under the influence and influence of the system itself. There is no 100% defined system for this. Stochastic systems - are those in which the application of the controlling or influential action of inputs to the system transforms the known state of the system into one possible state, but not the only action. Stochastic meaning is the opposite of determination. Stochastic meaning is used when we want to mark phenomena (processes) which do not perform according to the prescribed law but contain a random character. Their prediction is based on false probability experience. In the stochastic set of systems belong composite systems, hence systems consisting of a large number of interconnected elements. Often with stochastic systems we refer to systems that cannot be described accurately in the language of mathematics either because the system has a large number of related elements unknown to us or because we know enough about the nature of the phenomena that occur. in the system itself, and therefore we cannot quantitatively describe them. Systems with stochastic behavior are thought of as systems where processes and changes in them are driven by insufficient causes for us. To govern these systems we need to know the probability of the origin of the particular state of the system in which they can be found after the implementation of the particular action (experiments).Equilibrium - is once and for all the right condition. When the system sets a state of equilibrium, then it tends to contain that state regardless of the circumstances that prevail in the surroundings. If the system with external or internal impact is removed from the equilibrium state and if it returns to equilibrium state even after the effects of those triggers are stopped, then it is a stable system. The stable system has the specified equilibrium time and does not change location and condition without the influence of external forces. Labile system - after exerting force from outside it returns to the previous state again with the help of another force. The system with large entropy does not return on its own. Label system processes usually progress and we stop them as needed. Indifferent systems - take the position and remain n and remain in it depending on the force acting on it.

Diaminehalogenoplatinum(II) complex reactions with DMSO

Abstract The platinum(II) complexes [Pt(N-N)X2] (X = Cl, Br, and I; (N-N) = 1,2-ethanediamine (en) and 1,3-propanediamine (tn)) have been synthesised; their reactions with DMSO in DMSO to substitute halogenide were followed using changing integrals of NMR-spectroscopic signals. The rate constant for [PtenCl2] was found to be 1.0*10−4 s−1 at 300 K and from kinetic runs at different temperatures the energy of activation was estimated as 82 kJ*mol−1 in this case. The rate constant depends on the size of halogenide and was found to be forty times larger for [PtenI2] than for its dichloro-analogue. In the tn-series reactions were a little faster than in the en-series. For all six [Pt(N-N)X2] complexes the solvolysis stopped at the coordination of one DMSO and the six new [Pt(N-N)DMSOX]X were isolated and characterised. Further the [PtenDMSOCl]+ was isolated as its nitrate and perchlorate. DMSO exchange reactions (in DMSO) of [PtenDMSOX]+ were found to be slightly slower than the solvolysis reactions, iodide again giving rise to the most labile system. Ion pair formation in DMSO was found to be modest to almost negligible with a formation constant of 30 M−1 in the case of [PtenDMSOCl]Cl as the largest.

Rapid access to a series of calcitriol analogues with restricted side chain conformation

The synthesis of a series of calcitriol analogues with restricted side chain conformation is described. C-22 modified calcitriol analogues have been prepared from a common intermediate, in which the labile triene system is already present.

Neutron Studies of Composites of Poly(phenylene oxide) Modified by Hybrid Star‐Shaped Fullerene‐Containing Macromolecules

SummaryFilms of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) pure and modified by the hybrid star‐shaped polymer (1; 3 and 5% wt.) consisting of fullerene C60 core with the grafted arms of polystyrene (PS) and diblock copolymer of 2‐vinylpyridine (2VP) and tert‐butyl methacrylate (TBMA) have been prepared and analyzed by small‐angle neutron scattering. The neutron studies of these dry samples and then the same polymers saturated with D‐methanol have demonstrated in pure PPO‐matrix the existence of a labile system of branched channels for solvent diffusion. Meanwhile in the composites a developed network of stable linear channels was observed. The investigations of membranes' morphology by scanning electron microscopy (SEM) have revealed the presence of micro‐sized domains in the samples in accordance with the neutron scattering data.

Analysis of metal speciation dynamics in clay minerals dispersion by stripping chronopotentiometry techniques

In aqueous systems, interactions of metal ions with colloidal interphases are considered as a key feature for analyzing trace metal speciation, mobility, lability and bioavailability. Among colloidal matters of interests, clay minerals play a major role in metal complexes formation and sorption. The aim of this study is to analyze the dynamic speciation of metal in the presence of clay as colloidal ligand. This work is achieved by means of two complementary electroanalytical techniques: Absence of Gradients and Nernstian Equilibrium Stripping (AGNES) is used for the direct determination of the free metal in solution and stripping chronopotentiometry at scanned deposition potential (SSCP) is applied for the dynamic speciation analysis. The measured response of SSCP reflects the flux properties (limiting transport or kinetic fluxes) of metallic species and allows the determination of thermodynamic constants and analytical lability features of metal complexes. In addition to that, one of the main interests of using such a technique lies in the fact that analyses are achieved in metal concentrations of environmental relevance (from millimolar to nanomolar). For anisotropic and chemically heterogeneous particles such as clay particles, this study demonstrates the possibility to obtain useful information as the determination of diffusion coefficients of particles as well as the description of dynamic behavior of metal species as a function of physicochemical conditions of the suspension. In this regard, this study shows that the sorption of cadmium by clays can be described as a chemically homogeneous and labile system along a large range of pH whereas lead sorption shows some heterogeneity aspects, while remaining SSCP-labile.

Temporal Games of Pollination in the Life Cycle of an Annual Weed: Trifolium fragiferum L.

Trifolium fragiferum L. (Fabaceae) is an ecologically successful and colonizing hermaphroditic annual weed which is found abundantly in Jammu, J&K. The plants are self-compatible and are visited by a number of insects like bees, wasps and butterflies. In the absence of insect visits, this species undergo selfing through in situ pollen germination. The species appears to have utilized different pollination mechanisms to adapt to unpredictable environment conditions with obvious advantages of reproductive assurance by forming selfed as well as crossed seeds (mixed mating). Further, this labile mating system allows a response to changing pollinator environment for the survival and natural propagation of this species.

The choice of foraging strategy as a mechanism for the coexistence of Myrmica species (Hymenoptera, Formicidae) in a multispecific ant association

The foraging behavior and some mechanisms responsible for differentiation of ecological niches were studied in five Myrmica species that frequently coexist in nature. These species were assigned to three life forms according to the preference of litter or grass cover in the course of foraging. The group foraging of Myrmica was found to be a labile communicative system, affected by the layered distribution of species and competition with closely related species. In cases when species of the same life form shared a hunting area, or when their foraging layers overlapped by over 75%, some specific hierarchical interactions were observed: the colonies of the suppressed species changed the layer of foraging or ceased to forage in groups, collecting food instead as single predators. In most cases, the prevalence-subdominance relations between the associations studied were absent.

Influence of electronic and steric effects on stability constants and electrochemical reversibility of divalent ion complexes with glycine and sarcosine: A glass electrode potentiometric, sampled direct current polarographic, virtual potentiometric, and molecular modelling study

Cd II complexes with glycine (gly) and sarcosine (sar) were studied by glass electrode potentiometry, direct current polarography, virtual potentiometry, and molecular modelling. The electrochemically reversible Cd II–glycine–OH labile system was best described by a model consisting of M(HL), ML, ML 2, ML 3, ML(OH) and ML 2(OH) (M = Cd II, L = gly) with the overall stability constants, as log β, determined to be 10.30 ± 0.05, 4.21 ± 0.03, 7.30 ± 0.05, 9.84 ± 0.04, 8.9 ± 0.1, and 10.75 ± 0.10, respectively. In case of the electrochemically quasi-reversible Cd II–sarcosine–OH labile system, only ML, ML 2 and ML 3 (M = Cd II, L = sar) were found and their stability constants, as log β, were determined to be 3.80 ± 0.03, 6.91 ± 0.07, and 8.9 ± 0.4, respectively. Stability constants for the ML complexes, the prime focus of this work, were thus established with an uncertainty smaller than 0.05 log units. The observed departure from electrochemical reversibility for the Cd–sarcosine–OH system was attributed mainly to the decrease in the transfer coefficient α. The MM2 force field, supplemented by additional parameters, reproduced the reported crystal structures of diaqua-bis(glycinato-O,N)nickel(II) and fac-tri(glycinato)-nickelate(II) very well. These parameters were used to predict structures of all possible isomers of (i) [Ni(H 2O) 4(gly)] + and [Ni(H 2O) 4(sar)] +; and (ii) [Ni(H 2O) 3(IDA)] and [Ni(H 2O) 3(MIDA)] (IDA = iminodiacetic acid, MIDA = N-methyl iminodiacetic acid) by molecular mechanics/simulated annealing methods. The change in strain energy, Δ U str, that accompanies the substitution of one ligand by another (ML + L′ → ML′ + L), was computed and a strain energy Δ U str = +0.28 kcal mol −1 for the reaction [Ni(H 2O) 4(gly)] + + sar → [Ni(H 2O) 4(sar)] + + gly was found. This predicts the monoglycine complex to be marginally more stable. By contrast, for the reaction [Ni(H 2O) 3IDA] + MIDA → [Ni(H 2O) 3MIDA] + IDA, Δ U str = −0.64 kcal mol −1, and the monoMIDA complex is predicted to be more stable. This correlates well with (i) stability constants for Cd–gly and Cd–sar reported here; and (ii) known stability constants of ML complex for glycine, sarcosine, IDA, and MIDA.

Complexation behavior of 1,1″:1′,1‴-bis(1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diyldimethyl)bisferrocene: structural determination, NMR, 57Fe Mössbauer and electrochemical measurements

The complexing behavior of 1,1″:1′,1‴-bis(1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diyldimethyl)bisferrocene ( 1) toward KPF 6 ion was studied. To gain a better understanding into the factors which determine the extent of this redox-switched bonding in the complexation of KPF 6 by 1, we carried out X-ray crystal structural determination, NMR, FAB-MS technique, cyclic voltammetry measurements, and 57Fe Mössbauer analyses. We suggest that the KPF 6 salt of 1 is not a kinetically labile system. Our studies also provide direct evidence that ferrocene crown ether displays a drop in complex stability upon oxidation.

Iododifluoromethyl alkenes [ICF 2CHCHR]: a labile system generated from 1,1-difluoro-1,3-diiodoalkanes and its trapping with nucleophiles

Treatment of 1,1-difluoro-1,3-diiodoalkanes (ICF 2CH 2CHIR 1, 1) with NEt 3 in various solvents or with KF/Al 2O 3/CH 3CN gave no alkenes (ICF 2CHCHR 1, 2), whereas with NaOH afforded α,β-unsaturated carboxylic acids, although a signal of 2 in 19 F NMR spectroscopy could be observed momentarily sometimes. However, the labile 2 can be trapped either with thiolate or phenoxide ions. The former reaction gives a mixture of CF 2CHCH(SR)R 1 and RSCF 2CHCHR 1, whereas the latter affords only ArOCF 2CHCHR 1. The nucleophilic substitution of the bromoanalogues, BrCF 2CH 2CHBrR 1 and BrCF 2CHCHR 1, has also been investigated. A mechanism involving S N2′ and an allene intermediate is proposed.

Intrapopulation and individual polymorphism of heterochromatin segments inTrillium camschatcenseKer.-Gawl.

SUMMARYThe present work reports the study of the topography and the size of the heterochromatin segments (H-segments) in the chromosomes of the plant of Trillium camschatcense Ker.-Gawl. from a Kamchatka population with the help, of a special chromosome analysis, computer program. The staining techniques used are C- banding and fluorochroming with Hoechst 33258. A high level of hereditary polymorphism as well as somatic chromosome aberrations appearing de novo has been found. The heterochromatin of Trillium camschatcense appears to be of a polymorphic labile system creating a wide variation spectrum within the population. It is postulated that it could be the onset of divergences into separate forms and the subsequent creation of new species.

Development of ischemia/reperfusion tolerance in the rat small intestine. An epithelium-independent event.

In stable organ systems, such as the heart and kidneys, an oxidant stress induces an increase in endogenous antioxidant systems resulting in an increased resistance of the tissue to a subsequent oxidant challenge. The development of this oxidant tolerance requires 1.5-6 d. The aim of the present study was to determine whether oxidant tolerance can be induced in the small intestinal mucosa, a labile system whose epithelium turns over every 2-3 d. Ischemia/reperfusion-induced epithelial barrier dysfunction of the small intestinal mucosa was monitored in Sprague-Dawley rats whose intestines had been exposed to an ischemic insult 1, 24, or 72 h previously. At 24 h, but not 1 or 72 h after the initial ischemic insult, the mucosa was more resistant to ischemia/reperfusion-induced barrier dysfunction. The antioxidant status of the mucosa was enhanced at 24 h, but not at 1 or 72 h after the initial ischemic insult. This adaptation appears to be specific for oxidants, since an initial ischemic insult imposed 24 h earlier also protected against H2O2-induced, but not acid- or ethanol-induced, barrier dysfunction. Further studies indicated that the increase in antioxidant status of the mucosa observed 24 h after the initial ischemic insult was a result of adaptational changes in the lamina propria, rather than the epithelium. In vitro studies with isolated epithelial cells also indicated that epithelial cells do not develop oxidant tolerance. We conclude that the development of oxidant tolerance in the small intestinal mucosa does not involve an active participation of the epithelial lining.

Concurrent task interference in stutterers: Dissociating hemispheric specialization and activation.

Using all four combinations of hand and foot, adult stutterers and nonstutterers performed a unimanual sequential finger tapping task together with a stimulus-contingent foot responding task. The two groups were similar in that both demonstrated more dual-task interference when using the ipsilateral than contralateral limb pairs. Contrary to a prediction based on a hypothesis that attributes stuttering to neural interference due to an ungated or unregulated activity flow between the hemispheres, stutterers did not show more interference than nonstutterers when using the contralateral limb pairs. The groups did differ, however, in terms of finger tapping interference associated with right- versus left-foot concurrent task responding. Nonstutterers showed more interference when using the left than right foot. This was interpreted in terms of the attentional demands that the foot responding task placed on a system with an inherent left-hemisphere attentional bias. The lack of a reliable difference in stutterers with respect to interference by the two feet is consistent with indications from other research that stutterers have a relatively labile system of hemispheric attention or activation. The results of the study are placed into the context of a general model of the brain mechanisms associated with stuttering.

The Rate and the Direction Parameters of Humus Transformation in Intensively Cultivated Orthic Luvisols

Summary The transformations of organic substances and soil humus are running in stages, consequently their intensity, rate and direction change. Inhibition and acceleration of the rate of the main components of mineralization and humification are closely connected with biorythm and soil organisms activity, with changes of soil moisture, temperature and aeration, with the presence of active organic compounds and humus substances. The increased amount of water soluble sugars, “non-matured” lignin and fulvic acids are an indicator of the labile system characterized by rapid course of changes and longer period of stabilization or dynamic equilibrium aquirement in the process of mineralization and humification.

ChemInform Abstract: Thermal and Photochemical C‐H Bond Reactions of Alkenes in (Tris(pyrazolyl)borato)iridium(I) Complexes.

AbstractIn the hope of obtaining a labile system from which it is possible to prepare polyhydrides an attempt is made to prepare the cyclooctene analogue of (V).

Ketoacidosis in children

Children's tendency to acetonic states (ketoacidosis) is associated with functional immaturity of the liver, increased tone of sympathetic innervation and labile nervous system. Constitutional abnormalities and dietary disturbances are of great importance in the development of the disease. The increasing frequency of ketoacidosis in children with pronounced clinical manifestations and insufficient familiarity of pediatricians with the diagnosis of this condition prompted us to study the features of ketoacidosis clinic, diagnosis and treatment in children.