Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A high affinity calcium-binding protein has recently been purified from the adrenal medulla (Kuo, I.C.Y., and Coffee, C.J. (1976) J. Biol. Chem. 251, 1603-1609). This protein is closely related in its chemical and physical properties to troponin-C (TN-C) of muscle tissue. Further examination of the adrenal medulla protein indicates that the removal of calcium is accompanied by a marked change in the conformation. This change in structure is similar, if not identical, to the calcium-dependent conformational change which has been described for skeletal muscle TN-C (Murray, A.C., and Kay, C.M. (1972) Biochemistry 11, 2622). The far ultraviolet circular dichroism spectrum of native adrenal medulla calcium-binding protein (AM-CBP) shows characteristic helical ellipticity bands at 222 and 207 nm. The helical content, as estimated from these data, is between 40 and 45%. Removal of calcium is accompanied by a change in ellipticity which corresponds to a decrease from 40 to 20% in the helical content. The near-ultraviolet circular dichroism spectrum shows negative dichroic bands at 262 and 268 nm which are characteristic of phenylalanine. These bands are relatively insensitive to changes in the calcium ion concentration. Sedimentation velocity studies likewise are indicative of a calcium-dependent structural alteration. The sedimentation coefficient of the native protein was observed to be 1.89 S. Similar measurements performed in the presence of 3 mM ethylene glycol bis(beta-aminoethyl ether) N,N, N', N'-tetraacetic acid (EGTA) gave a sedimentation coefficient of 1.50 S. The molecular weight, as determined by sedimentation equilibrium studies, was 16,000 regardless of whether the measurements were made in the presence of CaCl2 or EGTA. From the elution properties of AM-CBP on Sephadex G-100, the Stokes radius was observed to be 19.8 A in the presence of calcium and 21.9 A in the presence of EGTA. All of these changes which were induced by the addition of EGTA were completely reversible by the readdition of excess CaCl2. These data suggest that the removal of calcium from AM-CBP is accompanied by a pronounced conformational change which occurs without a molecular weight change. The decreased sedimentation coefficient, the increased Stokes radius, and the reduced helical content, which are observed for the apoprotein, indicate that removal of calcium results in a transformation from a compact symmetrical structure to one that is less ordered and more asymmetrical.
 ...
PMID:Bovine adrenal medulla troponin-C. Demonstration of a calcium-dependent conformational change. 97 71

The cuticle of the gill lamina of the crayfish Astacus leptodactylus (E), mechanically isolated, was mounted in an Ussing chamber and examined for its electrical properties. The cuticle of the gill lamina obtained from exuviae had similar properties. When perfused with artificial fresh water (AFW) outside and Van Harreveld solution (VH) inside, the transcuticular potential Voi was negative with respect to the inside, and close to the equilibrium potential for Cl- (ECl-). CH3COO-, HCO3-, SO4(2-) and cations (Na+, K+, Ca2+, Mg2+ and NH4+) behaved as impermeant ions with respect to Cl-. A decrease of pH (brought about with CO2) from 8.5 to 6.0 in AFW, VH or both had no effect on the potential. The cuticle area specific conductance was 20-30 mS/cm2 when superfused with AFW outside and VH inside. The conductance decreased linearly with log [Cl-] when Cl- was replaced by CH3COO-. Rectification was obvious when internal Cl- was reduced to 5 mmol/l. The Cl- selectivity of the cuticle could also be demonstrated in perfusing the cuticle with a single salt (NaCl, KCl, CaCl2, MgCl2 or LaCl3) and in diluting that salt on one side of the preparation or in replacing Cl- by CH3COO-, SO4(2-) and HCO3-. The potential changed almost linearly with log [Cl-] and was close to ECl-. The inner face of the cuticle was found to be slightly less selective than the outer face. The relative permeabilities were calculated to be: PCl- = 1, PNa+ = 0.001, PHCO3- = 0.0006, PCH3COO- = 0.0002. The dilution of a Cl- -free salt resulted in a cationic potential. The relative permeabilities of cations (NH4+, K+, Na+, Ca2+ and Mg2+) were found to range within a factor 2. The permeability of the cuticle to HCO3-, CH3COO- and SO4(2-) was 2-5 times lower. The cuticle conductance was linearly related to the activity of the salt perfusing the two sides of the preparation at equal concentrations. The molar area specific conductance to chloride salts was 14 (mS/cm2)/(mmol/l). That of Cl- -free salts ranged from 1 to 20 (microS/cm2)/(mmol/l) depending on the salt used. It was deduced that PCl- is 2 X 10(-3) cm/s and that all the other ions tested have permeabilities of 10(-7)-10(-6) cm/s. With large intensity current pulses the cuticle exhibited rectifying properties and an asymmetrical behaviour. Increasing the pH of the perfusing solution reduced the transcuticular potential established with a Cl- gradient.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Ionic permeabilities of the gill lamina cuticle of the crayfish, Astacus leptodactylus (E). 241 Jun 7

Freeze-fracture electron microscopy was applied to study membrane morphology in a phosphatidylethanolamine-deficient E. coli strain. For growth, this strain requires millimolar concentrations of specific divalent cations like Mg2+ or Ca2+. These cations bring the bilayer to nonbilayer phase transition temperature of the lipids back to wild type levels by shifting the phase preference of cardiolipin in the membrane towards the inverted hexagonal (H(II)) phase. Under growth conditions, these cells show a bilayer based membrane with an intramembrane particle distribution as in wild type cells. Upon lowering the temperature, smooth areas are observed corresponding to gel state lipid bilayer domains. Ca2+ was used to manipulate the phase behavior of the membrane lipids in situ. Exposing the cells to Ca2+ up to 100 mM at 42 degrees C did not result in the appearance of nonbilayer structures, despite the fact that in total lipid extracts under these conditions the hexagonal H(II) phase was observed. However, the addition of a Ca2+ ionophore, which leads to exposure to Ca2+ of both faces of the plasma membrane, gives rise to formation of H(II) phase, stacked bilayer domains and blebbing upon addition of 50 mM CaCl2 at 42 degrees C. We conclude that the asymmetrical localization of divalent cations in the periplasm of this strain allows them to be functionally effective while membrane stability is maintained.
 ...
PMID:A freeze-fracture study of the membrane morphology of phosphatidylethanolamine-deficient Escherichia coli cells. 909 13

Lake Tota (Boyaca, Colombia) supplies water for human consumption, agriculture and industry for more than 500.000 people. Oxadixyl and Tebuconazole are fungicides used in onion crops in the lake catchment area. The mobility of pesticides in soil, bioavailability and transfer to other environmental compartments depend on sorption and desorption kinetics and mechanisms. An understanding of these processes is essential for transport modeling and the rational design of corrective measures against pollution. A displacement study was performed on a hand packed soil column in laboratory conditions. A pulse of 0,01 M CaCl2 solution, containing a tracer (Bromide) and the fungicides Oxadixyl y Tebuconazole, was injected. Column experiment was performed at 0.078 cmh(-1) flow rate under unsaturated conditions. Eluates were collected in flasks at constant intervals and the volumes of eluate were recorded. After rainfall simulation, the soil from the column was sliced into six successive sections (5 cm). Methanol extraction was used to determine the fungicide in each soil section. Samples were measured by HPLC. Only Oxadixyl was recovered in leachates. Unlike bromide breakthrough curve, Oxadixyl was asymmetrical, with early breakthrough and increased tailing. The percentage eluted was 96.7% after ten pore volumes. Tebuconazole showed the highest retention in the first five cm of soil layer. The results suggest that oxadyxil presents highs risk to leachate through the soil profile and that Tebuconazole is strongly absorbed in Colombian soil.
 ...
PMID:Leaching of oxadyxil and tebuconazole in Colombian soil. 2270 7

There are species differences in the regulatory system for sperm capacitation and subsequent hyperactivation between livestock and laboratory animals. In livestock spermatozoa, it is poorly understood when and how extracellular Ca(2+) is necessary for hyperactivation, although it has been demonstrated that the [Ca(2+) ]i increase is indispensable to occurrence of hyperactivation. In this study, we examined necessity of extracellular Ca(2+) for the initiation and maintenance of hyperactivation and then sought possible target molecule of Ca(2+) that was involved in hyperactivation of boar spermatozoa. Boar ejaculated spermatozoa were pre-incubated with a cell-permeable cyclic adenosine monophosphate (cAMP) analog 'cBiMPS' and without CaCl2 to induce the cAMP-triggered events including capacitation-associated changes. Subsequently, they were incubated with CaCl2 to induce hyperactivation and then used for motility assessment. Many of the spermatozoa after the incubation exhibited full-type hyperactivation which was characterized by high-amplitude and extremely asymmetrical beating of whole middle piece and principal piece. The initiation of full-type hyperactivation required the millimolar concentration of CaCl2 in the medium. However, CaCl2 of the medium was less necessary for maintenance than initiation of full-type hyperactivation, as hyperactivated spermatozoa were barely affected by the incubation with the Ca(2+) -chelating reagent. On the other hand, the pre-treatment with the inhibitor for Ca(2+) -dependent protease 'calpain 1 and 2' clearly suppressed the occurrence of CaCl2 -induced hyperactivation without influences on the percentages of motile spermatozoa. Western blotting and indirect immunofluorescence showed distribution of calpain 2 in the middle and principal pieces in which full-type hyperactivated spermatozoa exhibited extremely asymmetrical beating. On the basis of these results, we conclude that the millimolar concentration of extracellular Ca(2+) is necessary for the initiation, but not for the maintenance of full-type hyperactivation in boar spermatozoa that beforehand undergo the cAMP-triggered events including capacitation-associated changes. Moreover, we suggest possible involvement of calpain 2 in the intracellular Ca(2+) signal transduction leading to full-type hyperactivation.
 ...
PMID:Roles of extracellular Ca(2+) in the occurrence of full-type hyperactivation in boar ejaculated spermatozoa pre-incubated to induce the cAMP-triggered events. 2565 39

The development of methods to monitor manufactured nanomaterials in the environment is one of the crucial areas for the assessment of their risk. More specifically, particle size analysis is a key element, because many properties of nanomaterial are size dependent. The sizing of nanomaterials in real environments is challenging due to their heterogeneity and reactivity with other environmental components. In this study, the fractionation and characterization of a mixture of polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs) of three different sizes were investigated using asymmetrical flow field-flow fractionation (AF4) coupled with UV-Vis spectrophotometry. In particular, the effects of electrolyte composition and natural organic matter (NOM) on the particle size and stability were evaluated. The fractogram peaks (i.e., stability) of three different AgNPs decreased in the presence of both 10 mM NaCl and 10 mM CaCl2, while increased with increasing concentration of humic acid (HA). In addition, the hydrodynamic diameters of AgNPs in both electrolytes slightly increased with an increase of HA concentration, suggesting the adsorption (coating) of HA onto the particle surface. It is also interesting to note that an increase in the particle size depended on the types of electrolyte, which could be explained by the conformational characteristics of the adsorbed HA layers. Consistent these results, AgNPs suspended in lake water containing relatively high concentration of organic carbon (TOC) showed higher particle stability and larger particle size (i.e., by approximately 4 nm) than those in river water. In conclusion, the application of AF4 coupled with highly sensitive detectors could be a powerful method to characterize nanoparticles in natural waters.
 ...
PMID:Characterization of Silver Nanoparticles under Environmentally Relevant Conditions Using Asymmetrical Flow Field-Flow Fractionation (AF4). 2657 93