Composition of mafic minerals from peralkaline potassic syenites-granite association from Bulgaria

2020 ◽  
Author(s):  
Momchil Dyulgerov
Keyword(s):  
Fluorine Content ◽  
Fluid Phase ◽  
Limited Range ◽  
Compositional Variation ◽  
Ministry Of Education ◽  
Magmatic Complex ◽  
A Site ◽  
Facial Types ◽  
Ti Content ◽  
Complex Display

<p>S</p><p>Several potassic-alkaline Variscan plutons (330 – 305 Ma) outcrop in Kraishte and Stara planina regions in Bulgaria: Lutskan, Svidnya, 7<sup>th</sup> Prestola Monastery, Buhovo-Seslavtsi, potassic syenites west of Shipka and Shipka (from west to east). These magmatic bodies have intermediate to acid compositions and evolve toward peralkaline syenites-granite residual varieties. They present a broad diversity in rock-forming mineralogy reflecting the variations of magma chemistry and conditions of crystallization. Evolution of mafic silicates in the plutons show unique features which enable to discriminate the trend of mineral evolution in each magmatic complex.</p><p>Pyroxenes from Svidnya pluton are presented in all facial types. Its compositions cover the entire spectrum from calcic to sodic varieties as pyroxenes evolve from diopside to aegirine. The clinopyroxenes from peralkaline syenite porphyries in Buhovo-Seslavtsi pluton belong to Ca-Na pyroxenes and their compositions vary from Wo<sub>25</sub>-En<sub>13</sub>-Fs<sub>13</sub>-Ac<sub>42</sub>- to Wo<sub>11</sub>-En<sub>6</sub>-Fs<sub>2</sub>-Ac<sub>65</sub>. Pyroxenes from potassic syenites west of Shipka display limited range and belong to pure diopside, whereas pyroxenes in the peralkaline dykes from Shipka pluton are aegirine-augites. Also, aegirine-augite and aegirine from Svidnya and Buhovo-Seslavtsi are enriched in Ti (TiO<sub>2</sub> up to 6.5 wt. %), while aegirine-augite from Shipka shows high Zr content (ZrO<sub>2</sub> up to 2.9 wt. %), as Ti and Zr enter pyroxene structure via Na(Mg,Fe<sup>2+</sup>)<sub>0.5</sub>(Ti, Zr)<sub>0.5</sub>Si<sub>2</sub>O<sub>6</sub> molecule.</p><p>Amphiboles from Lutskan and 7<sup>th</sup> Prestola Monastery are low temperature, reflecting their near-solidus stage of crystallization or postmagmatic reequilibration due to the circulation of deuteric fluids. Their composition is winchite - riebeckite, and winchite – barroisite, respectively. In turn, amphiboles from Svidnya complex display a narrow compositional variation from richterites to magnesio-arfvedsonite, and rarely eckermanite. Amphiboles in Buhovo-Seslavtzi complex show broad diversity in their composition as they belong to sodic-calcic and sodic groups. They evolve from ferrobaroisite, ferrowinchite to richterite and potassic-magnesio-arfvedsonite with [A]-site filled by K. Amphiboles from the potassic syenites outcropping west of Shipka are arfvedsonite, characterised with elevated Ti content (up to 4.4 wt. % TiO<sub>2</sub>).</p><p>Micas from all complexes show limited evolution. In Svidnya, Buhovo-Seslavtsi, Shipka and 7<sup>th</sup> Prestola Monastery only biotite is present. Characteristic feature of biotites from Shipka is the elevated fluorine content (up to 5 wt. % F) which coupled with presence of fluorite implies on the F-domination in the fluid phase during the crystallization of the rocks. In Lutskan and in the syenites west of Shipka micas show broad range of variation from phlogopite to biotite.</p><p> </p><p>Acknowledgements: The financial support provided by the NSF (Ministry of Education and Science of Bulgaria) through DH 14/8 project is acknowledged.</p>

Chemical variation in micas from the Cairngorm pluton, Scotland

1990 ◽  
Vol 54 (376) ◽  
pp. 355-366 ◽  
Author(s):  
T. N. Harrison
Keyword(s):  
Electron Microprobe ◽  
Fluid Phase ◽  
Primary Phase ◽  
Compositional Variation ◽  
Chemical Variation ◽  
Host Granite ◽  
Two Parameters ◽  
Ti Content ◽  
Type Substitution

AbstractElectron microprobe analyses of micas from the Cairngorm pluton in the Eastern Grampian Highlands of Scotland show extensive compositional variation in biotite, despite a lack of chemical variation in the host granite. Biotite has high Fe/(Fe + Mg) (0.6–0.85) and Alvi(0.6–2.1 a.f.u.), and enrichment trends in these two parameters are attributable to the Al-Tschermak and dioctahedral-trioctahedral substitutions, the latter becoming dominant with increasing Alvicontent. Ti content is low (0.2–0.4 a.f.u.), and is largely controlled by a Tschermak-type substitution. Biotite is also unusually rich in Mn (up to 2.57 wt. % MnO), which increases with both Alviand Fe/(Fe+Mg). F contents generally range between 0.55 and 2.05 wt.% All compositional variation in biotite can be attributed to the extensive development of a fluid phase during the late-magmatic and subsolidus evolution of the pluton. The presence of an abundant fluid phase has resulted in the alteration of biotite to muscovite, which has occurred in response to de-stabilization of the biotite as octahedralR2+cations are lost in favour of Al. Extreme build-up of this fluid phase has resulted in the crystallization of muscovite as a late, interstitial primary phase. Both primary and replacive muscovite have Fe/(Fe+Mg) > 0.50, 15–36 mol. % celadonite and <1 mol. %paragonite.

A Sensitivity Study of Reservoir Performance Using a Compositional Reservoir Simulator

1972 ◽  
Vol 12 (01) ◽  
pp. 3-12
Author(s):  
Edward T.S. Huang
Keyword(s):  
Limited Range ◽  
Measured Data ◽  
Compositional Variation ◽  
Fluid Sample ◽  
Laboratory Measurements ◽  
Reservoir Performance ◽  
Reservoir Fluid ◽  
Liquid Phases ◽  
Fluid Properties ◽  
Compositional Simulator

Abstract Simulation of isothermal fluid flow in a reservoir using a compositional simulator requires fluid properties that are functions of pressure and properties that are functions of pressure and composition. These properties, i.e., K-values, densities and viscosities of both vapor and liquid phases, are usually obtained from general correlations phases, are usually obtained from general correlations or laboratory measurements of a reservoir fluid sample during a differential-depletion experiment in a PVT cell. prediction of fluid properties of complex mixtures using existing correlations is generally subject to great uncertainties. The laboratory measured data that are generally correlated as functions of pressure have validity only over a limited range of compositional variation. The purposes of this paper were (1) to assess, using a linear compositional simulator, the error introduced into calculated reservoir performance by employing fluids with a given range of uncertainties in their physical properties; and (2) to examine the validity of using the physical data correlated in the compositional simulator as functions of pressure rather than functions of both pressure and composition. The gas cycling process was chosen for illustration because composition changes during this process are large and results are affected more than in a depletion-type process. The hypothetical reservoir fluid system considered in this study was a methane-n-butane-n-decane mixture chosen to simulate a volatile oil system. The results of this investigation show for the particular system studied that:(1)the K-values for particular system studied that:(1)the K-values for the lighter components have the most significant effect on the calculated reservoir performance; and(2)simulations using fluid properties that are equivalent to the data measured during a differential depletion experiment reliably predict reservoir performance even under conditions where significant performance even under conditions where significant variations in reservoir fluid composition occur. Introduction A number of papers have recently been published concerning the development of compositional reservoir simulators-the mathematical models that simulate isothermal flow of multiphase, multicomponent fluids in porous media considering mass transfer effects. These models, which properly describe the distribution of each individual component in both vapor and liquid phases and account for pressure and compositional dependence of K-values, phase densities and viscosities, are more rigorous than the conventional simulators. The latter assumes that the heavy component does not exist in the vapor phase. To use the compositional simulator, it is highly desirable that fluid properties, i.e., K-values, densities and viscosities, as functions of pressure and composition, be available. However, for complex reservoir fluid mixtures, this information is rarely available. These fluid properties are usually calculated from published generalized correlations or obtained from laboratory measurements of a reservoir fluid sample by performing differential depletion experiments in a PVT cell. Prediction of fluid properties of complex mixtures using existing correlations is generally subject to great uncertainty. These errors will certainly have effects on the predicted reservoir performance. These effects may predicted reservoir performance. These effects may even be amplified if all the fluid properties are calculated from correlations. Improvement of the correlation predicted data by adjusting these data to match the limited available experimental values for the system of interest can be make. Yet there is no guarantee that the adjusted data will describe reliable fluid behavior in the region away from the matched points. On the other hand, the laboratory measured data, which are expressed as functions of pressure only, have validity over a limited range of pressure only, have validity over a limited range of compositional variation. When compositions of reservoir fluids vary significantly, the reliability of applying the laboratory measured data in the numerical simulation becomes questionable. SPEJ p. 3

scholarly journals Distinct Protein Sorting and Localization to Premelanosomes, Melanosomes, and Lysosomes in Pigmented Melanocytic Cells✪

2001 ◽  
Vol 152 (4) ◽  
pp. 809-824 ◽  
Author(s):  
Graça Raposo ◽  
Danielle Tenza ◽  
Diane M. Murphy ◽  
Joanne F. Berson ◽  
Michael S. Marks
Keyword(s):  
Kinetic Analysis ◽  
Cathepsin D ◽  
Fluid Phase ◽  
Immunogold Labeling ◽  
Endosomal Compartment ◽  
Distinct Lineage ◽  
Ultrathin Cryosections ◽  
Lysosome Related Organelles ◽  
A Site ◽  
Lysosomal Proteins

Melanosomes and premelanosomes are lysosome-related organelles with a unique structure and cohort of resident proteins. We have positioned these organelles relative to endosomes and lysosomes in pigmented melanoma cells and melanocytes. Melanosome resident proteins Pmel17 and TRP1 localized to separate vesicular structures that were distinct from those enriched in lysosomal proteins. In immunogold-labeled ultrathin cryosections, Pmel17 was most enriched along the intralumenal striations of premelanosomes. Increased pigmentation was accompanied by a decrease in Pmel17 and by an increase in TRP1 in the limiting membrane. Both proteins were largely excluded from lysosomal compartments enriched in LAMP1 and cathepsin D. By kinetic analysis of fluid phase uptake and immunogold labeling, premelanosomal proteins segregated from endocytic markers within an unusual endosomal compartment. This compartment contained Pmel17, was accessed by BSA–gold after 15 min, was acidic, and displayed a cytoplasmic planar coat that contained clathrin. Our results indicate that premelanosomes and melanosomes represent a distinct lineage of organelles, separable from conventional endosomes and lysosomes within pigmented cells. Furthermore, they implicate an unusual clathrin-coated endosomal compartment as a site from which proteins destined for premelanosomes and lysosomes are sorted.

scholarly journals Size Isn’t Everything - Compositional Variation in Hybrid Organic-Inorganic Lead Halide Perovskites: Kinetically- versus Thermodynamically-controlled Synthesis

2021 ◽  
Author(s):  
Jiyu Tian ◽  
Eli Zysman-Colman ◽  
Finlay Morrison
Keyword(s):  
Solid Solution ◽  
Solid Solutions ◽  
Compositional Variation ◽  
X Ray Diffraction ◽  
Solid Solution Formation ◽  
X Ray ◽  
H Nmr ◽  
Halide Perovskites ◽  
A Site ◽  
Lead Halide

<p>The formation and study of a partial solid solution <a></a><a>Az<sub>1-<i>x</i></sub>FA<i><sub>x</sub></i>PbBr<sub>3</sub></a>, using ‘similar’ sized cations azetidinium (Az<sup>+</sup>) and formamidinium (FA<sup>+</sup>), was explored via mechanosynthesis and precipitation synthesis. The composition and lattice parameters of samples from both syntheses were analysed by <sup>1</sup>H NMR and Rietveld refinement of the powder X-ray diffraction. A clear mismatch in the composition of the perovskite was found between the precipitated samples and the corresponding solutions. Such a mismatch was not observed for samples obtained via mechanosynthesis. The discrepancy suggests products are kinetically-controlled during precipitation, compared to thermodynamically-controlled mechanosynthesis. Furthermore, the cell volume as a function of composition in both 6H (Az-rich) and 3C (FA-rich) solid solutions suggests that FA<sup>+</sup> is actually smaller than Az<sup>+</sup>, contradicting the literature. In the 3C (Az-poor) solid solutions, the extent of Az<sub>1-<i>x</i></sub>FA<i><sub>x</sub></i>PbBr<sub>3 </sub>is unexpectedly smaller than Az<sub>1-<i>x</i></sub>MA<i><sub>x</sub></i>PbBr<sub>3</sub>, again in contradiction to the expectation based on the reported cation sizes. These results indicate that other factors, as yet unidentified, must also contribute to the solid solution formation of organic-inorganic hybrid perovskites, not simply the relative sizes of the A-site cations.</p>

scholarly journals Tourmaline chemistry in the Miocene and Paleozoic granites, Central Nepal Himalaya

2004 ◽  
Vol 29 ◽  
Author(s):  
Santa Man Rai
Keyword(s):  
Fluid Phase ◽  
Compositional Variation ◽  
Nepal Himalaya ◽  
Central Nepal ◽  
Tethys Himalaya ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Augen Gneiss ◽  
Almost All ◽  
Host Rocks

Tourmalines are found in almost all the formations, from the Lesser Himalaya to the Tibetan-Tethys Himalaya. They are equally found in the Miocene and Paleozoic granites in Central Nepal. Aplite-pegmatite dykes and Miocene granite from the Higher Himalaya, Tibetan-Tethys Himalaya also contain the tourmaline. The chemical composition of tourmalines from the Miocene granite, Paleozoic granite, and aplite pegmatites is presented in schorlite (Fe)-dravite (Mg)-elbaite (Al) diagram. The tourmalines from the granites are schorlitic (rich in Fe) in composition. No compositional variation between rim and core of the tourmaline in augen gneiss of the Formation III of the Higher Himalaya could correspond to the recrystallization of the tourmaline during the Himalayan metamorphism. The tourmalines from Manaslu and Chhokang granites can be evolved from Mg rich composition in higher temperature towards the Fe rich in lower temperature during the crystallization reflected by the XFe variation. Similarly, the composition of tourmalines is found to evolve from dravite (Mg rich) in the aplite-pegmatite dykes of the Higher Himalaya to schorlite (Fe rich) and elbaite (Al) in the aplite-pegmatite dykes of the Annapurna Formation of the Tibetan-Tethys Himalaya and Manaslu granite. The aplite-pegmatite dykes intruded into the pelitic rocks contain Mg rich tourmalines while Fe rich tourmalines are found in calcareous host rocks. So, the composition of the tourmalines of aplite-pegmatites can not be controlled by the composition of host rocks, but it is indirectly controlled by the composition of fluid phase of magma.

Origin and alteration of platinum group minerals in chromite deposits of the Ulan-Sardag ophiolite

2020 ◽  
Author(s):  
Olga Kiseleva ◽  
Eugenia Airiyants ◽  
Dmitry Belyanin ◽  
Sergey Zhmodik
Keyword(s):  
Solid Solutions ◽  
Stoichiometric Composition ◽  
Fluid Phase ◽  
Mineral Chemistry ◽  
Ministry Of Education ◽  
Island Arcs ◽  
Ocean Ridges ◽  
Magmatic Stage ◽  
Eastern Sayan ◽  
Individual Grains

&lt;p&gt;Ultrabasic Ulan-Saridag massif is part of the Eastern Sayan ophiolite belts, lying between the ophiolites of the southern and northern branches. It was suggested that ophiolites of the southern branch were created in mid-oceanic ridges, and southern one &amp;#8211; in island arcs environment. Recent data indicate the formation of Ulan- Saridag ophiolites in supra-subduction conditions of ensimatic island arcs.&lt;/p&gt;&lt;p&gt;Ore podiform chromitites consist of alumochromite, chromite, and chrompicotite (first finding for this region). Cr-spinelides are divided into three groups according to geochemistry. They refer to the MORB-peridotite, supra-subduction peridotites to the complexes of Ural-Alaska type.&lt;/p&gt;&lt;p&gt;PGE mineralization in this massif is represented by Os-Ir-Ru solid solutions, native Os, Ru, laurite-erlichmanite (Ru, Os)S&lt;sub&gt;2&lt;/sub&gt;, laurite (RuS&lt;sub&gt;2&lt;/sub&gt;), irarsite (IrAsS), zaccarinite (RhNiAs).&lt;/p&gt;&lt;p&gt;Solid solutions of Os-Ir-Ru were found as idiomorphic inclusions in Cr-spinel and xenomorphic grains in intergrowths with laurite. They correspond to the early high-temperature magmatic solid-solution Os-Ir-Ru. Also, the phases (Os-Ir-Ru) of varying composition are common in the form of numerous micro - and nano-size inclusions in laurite-erlichmanite with osmium or ruthenium. Native Os&lt;sup&gt;o&lt;/sup&gt; (Os&gt; 80 wt.%) is recognized in polyphase aggregates, together with chalcocite, laurite, laurite-erlichmanite. Native Ru (Ru=93 wt.%) &amp;#8211; occur in the polyphase, together with heazlewoodite, zaccarinite, Os-Ir-Ru solid solutions. Laurite and laurite- erlichmanite RuS&lt;sub&gt;2&lt;/sub&gt; &amp;#8211; (Ru, Os)S&lt;sub&gt;2&lt;/sub&gt; are represented most widely.&lt;/p&gt;&lt;p&gt;There are two groups: 1) laurite-erlichmanite (Ru, Os)S&lt;sub&gt;2&lt;/sub&gt;; 2) laurite RuS&lt;sub&gt;2&lt;/sub&gt;- phase of variable composition. (Ru, Os)S&lt;sub&gt;2&lt;/sub&gt; rarely forming independent grains, occurring more often in multi-component aggregates, &amp;#160;together with the laurites and contains a large number of rounded and rectangular micro-inclusions of native Os, (Os-Ir), and native Ru. Laurite has the reveal &amp;#160;stoichiometric composition (Ru=61,2 wt.%, S = 38.2 wt.%). It forms individual grains in chlorite and serpentine in association with irarsite, sulfides of Ni, Cu and rims around laurite-erlichmanite.&lt;/p&gt;&lt;p&gt;Solid solutions of (Os-Ir-Ru) and laurite-erlichmanite are forming before or simultaneously with Cr- spinel in the upper mantle at T=1200&lt;sup&gt;o&lt;/sup&gt;C and P= 5-10 kbar.&lt;/p&gt;&lt;p&gt;Sulfoarsenides and arsenides of Ru, Ir, Rh, Ni are formed from the residual fluid phase at a post-magmatic stage, together with heazlewoodite. It is possible that in chromitites from Ulan-Saridag there are two generations of sulfides. 1-st PGM generation &amp;#8211; magmatic solid solutions of laurite-erlichmanite. 2 -nd generation &amp;#8211; the newly formed laurite, with primary laurite-erlichmanite or intergrowths with chalcocite, heazlewoodite and millerite confined to zones of chloritization. The predominance of &amp;#160;Os, Ru sulfides over the solid solutions of Os-Ir-Ru indicates a higher sulfur fugacity in the mantle source of Ulan-Sardag ultramafic-mafic massif. These results indicate the distinctive characteristics of PGM of Ulan-Sardag massif compared to PGM from the chromitites of the Northern and Southern branches of the ophiolites.&lt;/p&gt;&lt;p&gt;Ulan-Sardag ultrabasic massif occurred in three different geodynamic settings: mid-ocean ridges, primitive ensimatic and ensialic island arcs, subduction zone, and belongs to the Alaska type basic formation.&lt;/p&gt;&lt;p&gt;Mineral chemistry was determined at the Analytical Centre for multi-elemental and isotope research SB RAS. This work supported by RFBR grants: No. 16-05-00737a, 15-05-06950, 19-05-00764 and the Russian Ministry of Education and Science.&amp;#160;&lt;/p&gt;

Pasi ne (Down With) Class Struggle? The New History for Schools in Zimbabwe

1984 ◽  
Vol 11 ◽  
pp. 367-374
Author(s):  
I.R. Phimister
Keyword(s):  
Secondary School ◽  
Class Struggle ◽  
Fold Increase ◽  
School Enrollment ◽  
The State ◽  
Ministry Of Education ◽  
The People ◽  
The One ◽  
Primary School Pupils ◽  
A Site

The struggle by the people of Zimbabwe to overthrow Ian Smith's Rhodesian regime in the 1970s won the support and gripped the imagination of democratic peoples around the world. As the struggle intensified, so it began to move away from nationalism towards liberation. Control of the state was no longer seen as an end in itself. For the vision of a socialist Zimbabwe to become reality, the state would have to be fundamentally restructured. The pace and direction of this historic movement has lain at the center of all subsequent encounters between the advanced capitalist countries and their local class allies on the one hand, and progressive elements inside ZANU on the other. While the former have busied themselves with reversing such progress as was made during the war, the latter have tried to avoid the snares and pitfalls which infest the pragmatic roads leading away from the compromise reached at Lancaster House.Education no less than other state apparatuses has been a site of struggle between the forces of accommodation to the rule of capital and those of socialist transformation. By any measure, the expansion of Zimbabwe's educational infrastructure since independence in April 1980 has been phenomenal. Awarded some Z$408 million in 1982's Budget--a four-fold increase in little over three years--the Ministry of Education now caters for 1,903,917 primary school pupils, as opposed to 819,586 in 1979. Secondary school enrollment over the same period has climbed from 66,215 to 218,430. Equally impressive gains have been registered in the number of schools and schoolteachers.

Structural and magnetic properties of La0.72(Ca1−xSrx)0.28MnO3 (x = 0 to 1) manganites

2009 ◽  
Vol 24 (4) ◽  
pp. 1585-1589 ◽  
Author(s):  
M.P. Gutiérrez ◽  
J.H. Olivares ◽  
I. Betancourt ◽  
F. Morales
Keyword(s):  
Room Temperature ◽  
Structural Transition ◽  
Small Variation ◽  
Solid State Reaction Method ◽  
Rhombohedral Structure ◽  
Compositional Variation ◽  
Orthorhombic Structure ◽  
Entropy Variation ◽  
A Site ◽  
Marked Dependence

Polycrystalline manganites within the compositional variation La0.72(Ca1−xSrx)0.28MnO3 (x = 0, 0.25, 0.50, 0.75, 1.0) were synthesized by solid-state reaction method. An initial orthorhombic structure was observed at x = 0, with a subsequent change to rhombohedral structure for x ≥ 0.25. The Curie temperature of the compounds exhibited a marked dependence with the Sr content, with general variations between 190 K (x = 0) and 364 K (x = 1.0), while the saturation magnetization at room temperature showed a small variation between the range 0.30 and 0.38 T. The magnetocaloric effect, measured through heat capacity experiments, showed a maximum entropy variation of −2.56 J/kg · K at x = 0.25, besides a maximum adiabatic temperature variation of 1.13 K. Results are interpreted in terms of the structural transition observed and its effect on the radius of the A-site of the perovskite structure.

scholarly journals Designing a site-directory of web resources for a teacher of informatics

2019 ◽  
Vol 7 (2) ◽  
pp. 1-10
Author(s):  
Viktoriia Alekseienko ◽  
Olena Usata
Keyword(s):  
Information And Communication Technologies ◽  
Data Storage ◽  
Web Design ◽  
Information Architecture ◽  
Practical Significance ◽  
Ministry Of Education ◽  
Web Resources ◽  
Professional Activities ◽  
A Site ◽  
Structural Blocks

The article is devoted to the study of the process of creating and designing a site-catalogue of modern web resources for its usage by informatics teacher in his professional activities. Site Directory is a site that contains structured links that lead to other web resources and their short description. Web resources offer wide opportunities for a teacher and students, give access to a large array of relevant diverse information, and its rapid exchange during the lessons of computer science. The article covers the analysis of such concepts as "designing", "information architecture", "style in the design of the site". There were analyzed the draft order of the Ministry of Education and Science of Ukraine and sites that promote the preparation of teachers for lessons, get them acquainted with modern information and communication technologies in education. The general theoretical foundations of web site creation are considered: their types, structure, methods of data storage and processing. Besides, the key principles of designing web resources are described. The information architecture and its components are described in detail. The design process is described in the general sense as well as one of the stages of creating a website. Proper attention has been paid to the study of web design, its principles and features, and the user interface; its main elements, components and structural blocks and rules of their use were considered. The practical significance of this study is that it can be used for a full design a website-catalog of web resources for informatics teachers.

scholarly journals Localization of the complement-component-C3b-binding site and the cofactor activity for factor I in the 38kDa tryptic fragment of factor H

1984 ◽  
Vol 224 (2) ◽  
pp. 389-398 ◽  
Author(s):  
J Alsenz ◽  
J D Lambris ◽  
T F Schulz ◽  
M P Dierich
Keyword(s):  
Binding Site ◽  
Gel Filtration ◽  
Fluid Phase ◽  
Factor H ◽  
Tryptic Fragment ◽  
Factor I ◽  
Close Proximity ◽  
Cofactor Activity ◽  
A Site ◽  
Sepharose 4B

Trypsin treatment of human factor H (H160) [enzyme/substrate ratio 1:100 (w/w), 30 min, 37 degrees C] generated a 38 kDa (H38) and a 142 kDa (H142) fragment linked by disulphide bonds (H38/142). The fragments were purified by reduction with 2-mercapto-ethanol, gel filtration on a Sephadex G-200 column and affinity chromatography with monoclonal anti-(factor H) antibody coupled to Sepharose 4B. This monoclonal antibody bound to a site in the 38 kDa fragment. To localize the C3b binding site in factor H we used two enzyme-linked immunosorbent assays (e.l.i.s.a.). For the first test, e.l.i.s.a. plates were coated with C3b; H160, H38/142, H38 and H142 were added, and their binding was monitored by goat anti-(factor H) and peroxidase-labelled rabbit anti-goat antibodies. Only intact factor H bound to the C3b-coated plates. For the second test, e.l.i.s.a. plates were coated with comparable amounts of factor H or its fragments, and C3b was offered at several dilutions. In contrast with the results from the first assay, C3b bound to intact factor H, H38/142 and H38 but not to H142, thus characterizing H38 as the fragment carrying the C3b-binding site. To identify the fragment responsible for the cofactor activity of factor H (cleavage of fluid-phase C3b by factor I), 125I-C3b was incubated with either H38 or H142 and factor I. H142 had no cofactor activity, whereas H38 had the same cofactor function as intact H. To further investigate the relationship between the C3b-binding site and the site of factor H essential for its cofactor activity, we made use of monoclonal antibodies directed against the H38. Those antibodies inhibiting the binding of C3b to H160 also inhibited the cofactor function, whereas those without effect on the C3b binding also did not interfere with the cofactor activity. This suggests that the C3b-binding site and the site essential for the cofactor activity of factor H are both localized in the 38 kDa tryptic fragment of factor H in close proximity or are identical.

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