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Sample records for alh84001 carbonate globules

  1. Hydrothermal Origin for Carbonate Globules in ALH84001 by Analogy with Similar Carbonates from Spitsbergen (Norway)

    NASA Technical Reports Server (NTRS)

    Treiman, A. H.; Amundsen, H. E. F.; Blake, D. F.; Bunch, T.

    2002-01-01

    Basalts and xenoliths from Spitsbergen (Norway) contain carbonate globules nearly identical to those in ALH84001. The Spitsbergen globules formed from hydrothermal waters by analogy, so did those in ALH84001. Additional information is contained in the original extended abstract.

  2. Modern terrestrial analogues for the carbonate globules in Martian meteorite ALH84001.

    PubMed

    Kazmierczak, Józef; Kempe, Stephan

    2003-04-01

    Modern carbonate globules, located in cracks of submerged volcanic rocks and in calcareous pinnacles in alkaline (sodic) Lake Van, Turkey, appear to be analogues for the approximately 3.9 billion-year-old carbonate globules in Martian meteorite ALH84001. These terrestrial globules have similar diameters and are chemically and mineralogically zoned. Furthermore, they display surface and etching structures similar to those described from ALH84001, which were interpreted as fossilized microbial forms. These terrestrial carbonates formed at low temperatures where Ca-rich groundwaters enter the lake. Chemical, mineralogical, microbiological, and biomolecular methods were used in an attempt to decipher the process responsible for the genesis of these structures. Although the exact mode of formation of Lake Van carbonates remains an enigma, their similarity to the Martian globules indicates that the ALH84001 carbonates may have formed in similar setting on ancient Mars. PMID:12712250

  3. Olivine and Carbonate Globules in ALH84001: A Terrestrial Analog, and Implications for Water on Mars

    NASA Technical Reports Server (NTRS)

    Treiman, A. H.

    2005-01-01

    Carbonate globules in ALH84001 are associated with small olivine grains an unexpected finding because the olivines equilibrated at high T while the carbonate is chemically zoned and unequilibrated. A possible explanation comes from a terrestrial analog on Spitsbergen (Norway), where some carbonate globules grew in cavities left by aqueous dissolution of olivine. For ALH84001, the same process may have acted, with larger olivines dissolved out and smaller ones shielded inside orthopyroxene. Carbonate would have been deposited in holes where the olivine had been. Later shocks crushed remaining void space, and mobilized feldspathic glass around the carbonates.

  4. Olivine and Carbonate Globules in ALH84001: A Terrestrial Analog, and Implications for Water on Mars

    NASA Astrophysics Data System (ADS)

    Treiman, A. H.

    2005-03-01

    Low-temperature carbonate globules in ALH84001 are found near olivine grains that equilibrated at T>800° C. Terrestrial analogs from Spitsbergen (Norway) suggest an explanation of this association; the carbonate globules may have been deposited in cavities where olivine had been dissolved out.

  5. Thermal Decomposition of Siderite-Pyrite Assemblages: Implications for Sulfide Mineralogy in Martian Meteorite ALH84001 Carbonate Globules

    NASA Astrophysics Data System (ADS)

    Golden, D. C.; Ming, D. W.; Lauer, H. V., Jr.; Morris, R. V.

    2004-03-01

    Closed system heating experiments of siderite-pyrite mixtures produce magnetite-pyrrhotite associations similar to those reported for black rims of the carbonate globules in ALH84001 Martian meteorite. These results support an inorganic formation process for magnetite and pyrrhotite in ALH84001.

  6. X-ray microprobe measurements of the chemical compositions of ALH84001 carbonate globules

    SciTech Connect

    Flynn, G.J.; Sutton, S.R.; Keller, L.P.

    2004-01-28

    We measured minor element contents of carbonate from ALH84001 and report trends in tbe Ca, V, Mn and Sr in carbonate and the associated magnetite bands. McKay et al. suggested that carbonate globules in the ALH84001 meteorite from Mars contained evidence consistent with the development of bacterial life early in the history of Mars. This result provoked an extensive study of the ALH84001 meteorite. More recently Thomas-Keprta et al. have published a study showing that the magnetite associated with carbonate rims are of the size and shape produced by terrestrial bacteria. This paper has revived interest in ALH84001. The typical ALH84001 carbonate globule consists of four regions: a core of Fe-rich carbonate, a thin magnetite-rich band, a rim of Mn-rich carbonate, and another thin magnetite-rich band. Trace element analysis of each of these phases may allow us to address several important questions about these carbonates: (1) The origin of the magnetite-rich bands in the ALH84001 carbonate globules. If the magnetites are derived from the underlying carbonate through thermal decomposition (as proposed by Golden et al.), then we expect to see 'inherited' trace elements in these magnetite bands. (2) The origin of the rim carbonate, by determining whether the carbonate in the core has the same trace elements as the rim carbonates. (3) The age of the rim carbonate. Borg et al. dated the formation of the rim carbonate using the Rb/Sr chronometer. Borg et al. performed their measurements on an aliquot of what they called a high-Rb, low-Sr carbonate separate from the rim. We previously measured the trace element contents of chips from core and rim carbonates from an ALH84001 carbonate globule using an X-Ray Microprobe on Beamline X26A at the National Synchrotron Light Source. These measurements showed the rim carbonate had a very low Rb content, with Sr>>Rb, inconsistent with the {approx}5 ppm Rb reported by Borg et al. in the sample they dated by the Rb/Sr chronometer. The

  7. Elongated prismatic magnetite crystals in ALH84001 carbonate globules: potential Martian magnetofossils.

    PubMed

    Thomas-Keprta, K L; Bazylinski, D A; Kirschvink, J L; Clemett, S J; McKay, D S; Wentworth, S J; Vali, H; Gibson, E K; Romanek, C S

    2000-12-01

    Using transmission electron microscopy (TEM), we have analyzed magnetite (Fe3O4) crystals acid-extracted from carbonate globules in Martian meteorite ALH84001. We studied 594 magnetites from ALH84001 and grouped them into three populations on the basis of morphology: 389 were irregularly shaped, 164 were elongated prisms, and 41 were whisker-like. As a possible terrestrial analog for the ALH84001 elongated prisms, we compared these magnetites with those produced by the terrestrial magnetotactic bacteria strain MV-1. By TEM again, we examined 206 magnetites recovered from strain MV-1 cells. Natural (Darwinian) selection in terrestrial magnetotactic bacteria appears to have resulted in the formation of intracellular magnetite crystals having the physical and chemical properties that optimize their magnetic moment. In this study, we describe six properties of magnetite produced by biologically controlled mechanisms (e.g., magnetotactic bacteria), properties that, collectively, are not observed in any known population of inorganic magnetites. These criteria can be used to distinguish one of the modes of origin for magnetites from samples with complex or unknown histories. Of the ALH84001 magnetites that we have examined, the elongated prismatic magnetite particles (similar to 27% of the total) are indistinguishable from the MV-1 magnetites in five of these six characteristics observed for biogenically controlled mineralization of magnetite crystals. PMID:11543573

  8. Carbonate Globules from Spitsbergen, Norway: Terrestrial Analogs of the Carbonates in Martian Meteorite ALH84001?

    NASA Technical Reports Server (NTRS)

    De, Subarnarek; Bunch, Ted; Treiman, Allan H.; Amundsen, Hans E. F.; Blake, David F.; DeVincenzi, Donald L. (Technical Monitor)

    2001-01-01

    Pleistocene volcanic centers in NW Spitsbergen, Norway host one of the world's richest occurrences of mantle xenoliths. The xenoliths comprise varieties of spinel lherzolites and pyroxenites. Some of these xenoliths (and their host basalts) contain 10-100 micrometer globules of ankedtic-magnesitic carbonates (AMC). In composition, mineralogy and petrology the AMC globules from Spitsbergen are strikingly similar to the carbonate globules in ALH84001. The AMC globules occur within interstitial quenched glass and as fracture fillings, although we have not seen replacement fabrics analogous to carbonate rosettes replacing glass in ALH84001. Siderite/ankerite forms the core of these concentrically zoned globules while rims are predominantly magnesite. Clay minerals can occasionally be found within and around the globules. Aside from the clay minerals, the principal mineralogical difference between the AMCs and the ALH84001 carbonate rosettes is the presence of concentrated zones of nanophase magnetite in the rosettes, notably absent in the AMCs. However, carbonate globules containing nanophase magnetite have been produced inorganically by hydrothermal precipitation of carbonates and subsequent heating. We heated Spitsbergen AMC at 585 C in a reducing atmosphere to determine whether magnetite could be produced. Optical micrographs of the heated Spitsbergen AMC show dark concentric zones within the AMC. High resolution SEM images of those areas reveal 150-200 nm euhedral crystals that exhibit various morphologies including octahedra and elongated prisms. EDS analyses of areas where the crystals occur contain Fe, O, and minor Si, and P. However, the probe integrates over volumes of material, which also include the surrounding matrix. We have begun TEM observations of both the heated and unheated Spitsbergen AMC to characterize the microstructures of the carbonates, establish the presence/absence of magnetite and determine the relationship of the clay minerals to the

  9. X-Ray Microprobe Measurements of the Chemical Compositions of ALH84001 Carbonate Globules

    NASA Technical Reports Server (NTRS)

    Flynn, G. J.; Sutton, S. R.; Keller, L. P.

    2002-01-01

    We measured minor element contents of carbonate from ALH84001 and report trends in the Ca, V, Mn and Sr in carbonate and the associated magnetite bands. Additional information is contained in the original extended abstract.

  10. A Morphological and Chemical Study of Carbonate Globules Contained Within Mantle Xenoliths of the Sverrefjell Volcano Spitsbergen -- Implications for ALH84001

    NASA Astrophysics Data System (ADS)

    Steele, A.; Amundsen, H. E. F.; Fries, M.; Vicenzi, E. P.; Benning, L.; Maule, J.; Mysen, B.; Toporski, J.; Schweizer, M.; Fogel, M.

    2005-03-01

    We describe raman and elemental composition of globules similar to those found in ALH84001. We appear to see direct evidence of zonation of carbonate, carbon and silicon phases within terrestrial olivine mantle xenoliths.

  11. Hydrothermal Origin for Carbonate Globules in Martian Meteorite ALH84001: A Terrestrial Analogue from Spitsbergen (Norway)

    NASA Technical Reports Server (NTRS)

    Treiman, Allan H.; Amundsen, Hans E. F.; Blake, David F.; Bunch, Ted

    2002-01-01

    Carbonate minerals in the ancient Martian meteorite ALH84001 are the only known solid phases that bear witness to the processing of volatile and biologically critical compounds (CO2, H2O) on early Mars. Similar carbonates have been found in xenoliths and their host basalts from Quaternary volcanic centers in northern Spitsbergen (Norway). These carbonates were deposited by hot (i.e., hydrothermal) waters associated with the volcanic activity. By analogy with the Spitsbergen carbonates, the ALH84001 carbonates were probably also deposited by hot water. Hydrothermal activity was probably common and widespread on Early Mars, which featured abundant basaltic rocks, water as ice or liquid, and heat from volcanos and asteroid impacts. On Earth, descendants of the earliest life forms still prefer hydrothermal environments, which are now shown to have been present on early Mars.

  12. Hydrothermal origin for carbonate globules in Martian meteorite ALH84001: a terrestrial analogue from Spitsbergen (Norway)

    NASA Astrophysics Data System (ADS)

    Treiman, Allan H.; Amundsen, Hans E. F.; Blake, David F.; Bunch, Ted

    2002-12-01

    Carbonate minerals in the ancient Martian meteorite ALH84001 are the only known solid phases that bear witness to the processing of volatile and biologically critical compounds (CO 2, H 2O) on early Mars. Similar carbonates have been found in xenoliths and their host basalts from Quaternary volcanic centers in northern Spitsbergen (Norway). These carbonates were deposited by hot (i.e., hydrothermal) waters associated with the volcanic activity. By analogy with the Spitsbergen carbonates, the ALH84001 carbonates were probably also deposited by hot water. Hydrothermal activity was probably common and widespread on Early Mars, which featured abundant basaltic rocks, water as ice or liquid, and heat from volcanos and asteroid impacts. On Earth, descendants of the earliest life forms still prefer hydrothermal environments, which are now shown to have been present on early Mars.

  13. Magnetite and Carbonate Textures in ALH84001: Experimental Insights

    NASA Technical Reports Server (NTRS)

    Koziol, Andrea M.

    2001-01-01

    Synthetic siderite and synthetic siderite-magnesite carbonates were equilibrated with hematite, magnetite, and CO2 at elevated pressure and temperature. Comparisons are made to textures seen in the carbonate globules in ALH84001. Additional information is contained in the original extended abstract.

  14. Siderite globules associated with fossil microbiota from cretaceous cavity and fracture fillings in Southern Belgium: second known terrestrial analog for the carbonate in Martian meteorite ALH84001?

    NASA Astrophysics Data System (ADS)

    Baele, Jean-Marc

    2003-02-01

    Recently discovered siderite globules from Upper Cretaceous cavity and fracture fillings in southern Belgium are described and interpreted with emphasis on the still unsolved problem of the carbonates in meteorite ALH84001, which enclose controversal evidence for ancient Martian life. The most interesting aspects of the carbonates described here are 1) their close association with fossil microbiota, 2) their environment, which is 100% sedimentary, subaerial and not hydrothermal and 3) their morphologies, some of which being similar to those in ALH84001. Although the question of the direct biological influence is not critical in this case, the biogenicity for the minerals will be discussed as a strong possibility and is not only inferred from the simple spatial (and temporal) association of the carbonates and the fossil microbiota. Morphological, textural and chemical data will be presented and interpreted as variations in fluid chemistry related to environmental changes. Although they may appear different from those in Martian meteorite and Spitzbergen xenoliths, the Cretaceous globules originated in subsurface environment which left evident traces of life in the form of fossil microbial/fungal mats. They are thus considered as an opportunity to investigate biosignatures in future research using the wide range of available techniques.

  15. High Calcium (~80mol%) Late Stage Carbonate in ALH84001

    NASA Astrophysics Data System (ADS)

    Gildea, K. J.; Holland, G.; Lyon, I. C.; Chatzitheodoridis, E.; Burgess, R.

    2006-03-01

    Brief petrological, chemical and textural description of previously undescribed high Ca late stage carbonate in Martian meteorite ALH84001. This carbonate surrounds Mg rich carbonates and rosette fragments.

  16. Focused Ion Beam Microscopy of ALH84001 Carbonate Disks

    NASA Astrophysics Data System (ADS)

    Thomas-Keprta, K. L.; Clemett, S. J.; Bazylinski, D. A.; Kirschvink, J. L.; McKay, D. S.; Vali, H.; Gibson, E. K., Jr.; Romanek, C. S.

    2005-03-01

    Our aim is to understand the mechanism(s) of formation of carbonate assemblages in ALH84001. We present here analyses by transmission electron microscopy (TEM) of carbonate thin sections produced by both focused ion beam (FIB) sectioning and ultramicrotomy.

  17. Variable Carbon Isotopes in ALH84001 Carbonates

    NASA Astrophysics Data System (ADS)

    Niles, P. B.; Leshin, L. A.; Guan, Y.

    2002-12-01

    The Martian meteorite ALH84001 contains a small amount of carbonate that was deposited from aqueous fluids on the Martian surface approximately 3.9 Ga.. McKay et al. (1996) proposed evidence for the existence of life preserved within the carbonate grains. In order to determine the nature of the ancient Martian aqueous system we have combined previously collected oxygen isotopic data with new carbon isotopic measurements performed on the Cameca 6f ion microprobe at Arizona State University. Isotopic measurements were made at high mass resolution with a spot size of 10 microns. The measured carbon isotopic values range from 29.2‰ to 64.5‰ (PDB) with an average uncertainty of +/-1.6‰ (1σ ). These data agree very well with previous acid dissolution and stepped combustion experiments which range from a δ13C of +32‰ to +41‰ . As observed with the oxygen isotopic data, the carbon isotopic composition is correlated with the chemical composition of the carbonates. This allows us to establish that the earliest (Ca-rich) carbonates had the lightest carbon isotopic composition while the latest forming (Mg-rich) carbonates had the heaviest carbon isotopic composition. The large range of carbon isotopic compositions measured in this study cannot be explained by previously proposed models. Temperature change or a Rayleigh distillation process caused by progressive carbonate precipitation are insufficient to create the observed carbon isotopic compositions. Furthermore, processes such as evaporation or photosynthesis will not produce large carbon isotopic variations due to rapid isotopic equilibration with the atmosphere. We propose two possible models for the formation of the ALH84001 carbonates consistent with the isotopic data collected thus far. Carbonates could have formed from an evolving system where the carbon and oxygen isotopic composition of the carbonates reflects a mixing between magmatic hydrothermal fluids and fluids in equilibrium with an isotopically

  18. Kinetic model of carbonate dissolution in Martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Kopp, R. E.; Humayun, M.

    2003-09-01

    The magnetites and sulfides located in the rims of carbonate globules in the Martian meteorite ALH84001 have been claimed as evidence of past life on Mars. Here, we consider the possibility that the rims were formed by dissolution and reprecipitation of the primary carbonate by the action of water. To estimate the rate of these solution-precipitation reactions, a kinetic model of magnesite-siderite carbonate dissolution was applied and used to examine the physicochemical conditions under which these rims might have formed. The results indicate that the formation of the rims could have taken place in < 50 yr of exposure to small amounts of aqueous fluids at ambient temperatures. Plausible conditions pertaining to reactions under a hypothetical ancient Martian atmosphere (1 bar CO 2), the modern Martian atmosphere (8 mbar CO 2), and the present terrestrial atmosphere (0.35 mbar CO 2) were explored to constrain the site of the process. The results indicated that such reactions likely occurred under the latter two conditions. The possibility of Antarctic weathering must be entertained, which, if correct, would imply that the plausibly biogenic minerals (single-domain magnetite of characteristic morphology and sulfide) reported from the rims may be the products of terrestrial microbial activity. This model is discussed in terms of the available isotope data and found to be compatible with the formation of ALH84001 rims. Particularly, anticorrelated variations of radiocarbon with δ 13C indicate that carbonate in ALH84001 was affected by solution-precipitation reactions immediately after its initial fall (˜13,000 yr ago) and then again during its recent exposure prior to collection.

  19. Modeling the Chemical Composition of the Fluid that Formed the ALH84001 Carbonates

    NASA Astrophysics Data System (ADS)

    Niles, P. B.; Leshin, L.

    2005-12-01

    The character of aqueous systems on Mars can provide us with important information regarding the history of water and the possibilities for the presence of life on Mars. Evidence of these aqueous systems has been preserved in carbonates found in the martian meteorite ALH84001 whose crystallization age of 4.5 Ga indicates that it has experienced almost all of Mars' history. In addition, the 3.9 Ga age of the carbonates places their formation at a critical time that has been argued to have been `warm and wet' by many studies. The carbonates in the ALH84001 meteorite provide the best opportunity, among all of the martian meteorites, to understand the details of an ancient aqueous system on Mars. Their unique chemical, isotopic and mineralogical composition provides the opportunity to make conclusive statements about the geological conditions in which they formed including the temperature, association with the atmosphere, chemistry of the fluids, and the presence or absence of life. This study uses an empirical model to understand the attributes of the formation fluid based on the unique chemical compositions of the carbonates. This requires the assumption that the ALH84001 carbonate globules formed from a single fluid whose chemical composition changed due to the precipitation of carbonates more calcium rich than the overall fluid composition. The model consists of a simple stepwise stoichiometric calculation of the precipitation of the ALH84001 carbonates from a hypothetical solution. From extensive measurements of the chemical composition of the globules and their abundance in the rock, one can calculate the total amount of magnesium, calcium, and iron removed from the formation fluid as the carbonates precipitated. The unique zoned nature of the ALH84001 carbonates provides a real constraint on the possible fluid compositions consistent with their precipitation. Our results indicate that the fluid that formed the ALH84001 carbonates had an Mg/Ca ratio that was

  20. Cryogenic Calcite — A Morphologic and Isotopic Analog to the ALH84001 Carbonates

    NASA Astrophysics Data System (ADS)

    Niles, P. B.; Leshin, L. A.; Socki, R. A.; Guan, Y.; Ming, D. W.; Gibson, E. K.

    2004-03-01

    Experimentally produced cryogenic carbonates are strong morphologic analogs to the ALH84001 carbonates, in addition ion microprobe measurements reveal variations in delta-^13C similar to, but not as large as, the variations observed in ALH84001 carbonates.

  1. Biogenic Magnetite in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Bazylinski, Dennis; Wentworth, Susan J.; McKay, David S.; Kirschvink, Joseph L.; Clemett, Simon J.; Bell, Mary Sue; Golden, D. C.

    1999-01-01

    Fine-grained magnetite (Fe3O4) in martian meteorite ALH84001, generally less than 200 microns in size, is located primarily in the rims that surround the carbonate globules. There are two populations of ALH84001 magnets, which are likely formed at low temperature by inorganic and biogenic processes. Nearly 27/o of ALH84001 magnetite particles. also called elongated prisms, have characteristics which make them uniquely identifiable as biological precipitates.

  2. Biogenic Magnetite in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Bazylinski, Dennis; Wentworth, Susan J.; McKay, David S.; Kirschvink, Joseph L.; Clemett, SImon J.; Bell, Mary Sue; Golden, D. C.; Gibson, Everett K., Jr.

    1999-01-01

    Fine-grained magnetite (Fe3O4) in martian meteorite ALH84001, generally less than 200 nm in size, is located primarily in the rims that surround the carbonate globules. There are two populations of ALH84001 magnetites, which are likely formed at low temperature by inorganic and biogenic processes. Nearly 27% of ALH84001 magnetite particles, also called elongated prisms, have characteristics which make them uniquely identifiable as biological precipitates. Additional information is contained in the original extended abstract.

  3. Focused Ion Beam Microscopy of ALH84001 Carbonate Disks

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Bazylinski, Dennis A.; Kirschvink, Joseph L.; McKay, David S.; Vali, Hojatollah; Gibson, Everett K., Jr.; Romanek, Christopher S.

    2005-01-01

    Our aim is to understand the mechanism(s) of formation of carbonate assemblages in ALH84001. A prerequisite is that a detailed characterization of the chemical and physical properties of the carbonate be established. We present here analyses by transmission electron microscopy (TEM) of carbonate thin sections produced by both focused ion beam (FIB) sectioning and ultramicrotomy. Our results suggest that the formation of ALH84001 carbonate assemblages were produced by considerably more complex process(es) than simple aqueous precipitation followed by partial thermal decomposition as proposed by other investigators [e.g., 1-3].

  4. Paleomagnetic evidence of a low-temperature origin of carbonate in the Martian meteorite ALH84001.

    PubMed

    Kirschvink, J L; Maine, A T; Vali, H

    1997-03-14

    Indirect evidence for life on Mars has been reported from the study of meteorite ALH84001. The formation temperature of the carbonates is controversial; some estimates suggest 20 degrees to 80 degrees C, whereas others exceed 650 degrees C. Paleomagnetism can be used to distinguish between these possibilities because heating can remagnetize ferrimagnetic minerals. Study of two adjacent pyroxene grains from the crushed zone of ALH84001 shows that each possesses a stable natural remanent magnetization (NRM), implying that Mars had a substantial magnetic field when the grains cooled. However, NRM directions from these particles differ, implying that the meteorite has not been heated significantly since the formation of the internal crushed zone about 4 billion years ago. The carbonate globules postdate this brecciation, and thus formed at low temperatures. PMID:9054354

  5. Statistical Analyses Comparing Prismatic Magnetite Crystals in ALH84001 Carbonate Globules with those from the Terrestrial Magnetotactic Bacteria Strain MV-1

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Bazylinski, Dennis A.; Kirschvink, Joseph L.; McKay, David S.; Wentworth, Susan J.; Vali, H.; Gibson, Everett K.

    2000-01-01

    Here we use rigorous mathematical modeling to compare ALH84001 prismatic magnetites with those produced by terrestrial magnetotactic bacteria, MV-1. We find that this subset of the Martian magnetites appears to be statistically indistinguishable from those of MV-1.

  6. Leachates formed carbonates in ALH84001 and on early Mars

    NASA Astrophysics Data System (ADS)

    Melwani Daswani, M.; Grady, M. M.; Schwenzer, S. P.; Wright, I. P.

    2013-09-01

    Evidence abounds for liquid water existing on Mars prior to the late heavy bombardment (LHB) ~3.9 Ga ago and physicochemically interacting with rocks to form distinct geomorphological landforms and mineralogical alteration products (e.g. [3, 4, 8, 14]). ALH84001, the oldest (~4.5-4.1 Ga [11, 13]) known martian meteorite, contains secondary carbonate minerals formed on Mars ~3.9-4.0 Ga ago [5], roughly contemporaneous to the LHB. Recent isotopic evidence supports their formation at low temperature (~18 °C [9]) and also by fluids derived from aqueous weathering in the Noachian/Phyllosian, due to the elevated 87Sr/86Sr ratios in the carbonates and bulk rock of ALH84001 [1].

  7. Petrological evidence for shock melting of carbonates in the martian meteorite ALH84001.

    PubMed

    Scott, E R; Yamaguchi, A; Krot, A N

    1997-05-22

    The meteorite ALH84001--a shocked igneous rock of probable martian origin-contains chemically and isotopically heterogeneous carbonate globules, associated with which are organic and inorganic structures that have been interpreted as possible fossil remains of ancient martian biota. A critical assumption underlying this suggestion is that the carbonates formed from low-temperature fluids penetrating the cracks and voids of the host rock. Here we report petrological studies of ALH84001 which investigate the effects of shock on the various mineralogical components of the rock. We find that carbonate, plagioclase and silica were melted and partly redistributed by the same shock event responsible for the intense local crushing of pyroxene in the meteorite. Texture and compositional data show that, during the period of shock decompression, monomineralic melts were injected into pyroxene fractures that were subsequently cooled and resealed within seconds. Our results therefore suggest that the carbonates in ALH84001 could not have formed at low temperatures, but instead crystallized from shock-melted material; this conclusion weakens significantly the arguments that these carbonates could host the fossilized remnants of biogenic activity. PMID:9163421

  8. Oxygen isotopic constraints on the genesis of carbonates from Martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Leshin, Laurie A.; McKeegan, Kevin D.; Harvey, Ralph P.

    1997-03-01

    With a crystallization age of 4.5 Ga, ALH84001 is unique among the Martian meteorites. It is also the only Martian meteorite that contains an appreciable amount of carbonate, and significantly, this carbonate occurs without associated secondary hydrated minerals. Moreover, McKay et al. (1996) have suggested that ALH84001 contains evidence of past Martian life in the form of nanofossils, biogenic minerals, and polycyclic aromatic hydrocarbons. The presence of carbonate in ALH84001 is especially significant. The early Martian environment is thought to have been more hospitable to life than todays cold, dry climate. In order to better assess the true delta-O-18 values, as well as the isotopic diversity and complexity of the ALH84001 carbonates, direct measurements of the oxygen and carbon isotopic compositions of individual carbonate phases are needed. Here we report in situ analyses of delta-O-18 values in carbonates from two polished thin sections of ALH84001.

  9. The Origin of Magnetite Crystals in ALH84001 Carbonate Disks

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Clemett, S. J.; Wentworth, S. J.; McKay, D. S.; Gibson, E. K., Jr.

    2012-01-01

    Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks believed to have formed approx 3.9 Ga ago at beginning of the Noachian epoch. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of magnetite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. We have sought to resolve between these hypotheses through the detailed characterized of the compositional and structural relationships between the carbonate disks, their associated magnetites and the orthopyroxene matrix in which they are embedded. Comparison of these results with experimental thermal decomposition studies of sideritic carbonates conducted under a range of heating scenarios suggests that the magnetite nanocrystals in the ALH84001 carbonate disks are not the products of thermal decomposition.

  10. New Insights into the Origin of Magnetite Crystals in ALH84001 Carbonate Disks

    NASA Astrophysics Data System (ADS)

    Thomas-Keprta, K. L.; Clemett, S. J.; Wentworth, S. J.; McKay, D. S.; Gibson, E. K.

    2010-04-01

    Comparison of new TEM results with decomposition studies of sideritic carbonates conducted under a range of heating scenarios suggests that the magnetite nanocrystals in ALH 84001 carbonate disks are not the products of thermal decomposition.

  11. The age of the carbonates in martian meteorite ALH84001.

    PubMed

    Borg, L E; Connelly, J N; Nyquist, L E; Shih, C Y; Wiesmann, H; Reese, Y

    1999-10-01

    The age of secondary carbonate mineralization in the martian meteorite ALH84001 was determined to be 3.90 +/- 0.04 billion years by rubidium-strontium (Rb-Sr) dating and 4.04 +/- 0.10 billion years by lead-lead (Pb-Pb) dating. The Rb-Sr and Pb-Pb isochrons are defined by leachates of a mixture of high-graded carbonate (visually estimated as approximately 5 percent), whitlockite (trace), and orthopyroxene (approximately 95 percent). The carbonate formation age is contemporaneous with a period in martian history when the surface is thought to have had flowing water, but also was undergoing heavy bombardment by meteorites. Therefore, this age does not distinguish between aqueous and impact origins for the carbonates. PMID:10506566

  12. The age of the carbonates in martian meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Borg, L. E.; Connelly, J. N.; Nyquist, L. E.; Shih, C. Y.; Wiesmann, H.; Reese, Y.

    1999-01-01

    The age of secondary carbonate mineralization in the martian meteorite ALH84001 was determined to be 3.90 +/- 0.04 billion years by rubidium-strontium (Rb-Sr) dating and 4.04 +/- 0.10 billion years by lead-lead (Pb-Pb) dating. The Rb-Sr and Pb-Pb isochrons are defined by leachates of a mixture of high-graded carbonate (visually estimated as approximately 5 percent), whitlockite (trace), and orthopyroxene (approximately 95 percent). The carbonate formation age is contemporaneous with a period in martian history when the surface is thought to have had flowing water, but also was undergoing heavy bombardment by meteorites. Therefore, this age does not distinguish between aqueous and impact origins for the carbonates.

  13. Formation of "Chemically Pure" Magnetite from Mg-Fe-Carbonates Implications for the Exclusively Inorganic Origin of Magnetite and Sulfides in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Ming, Douglas W.; Lauer, H. V., Jr.; Morris, R. V.; Trieman, A. H.; McKay, G. A.

    2006-01-01

    Magnetite and sulfides in the black rims of carbonate globules in Martian meteorite ALH84001 have been studied extensively because of the claim by McKay et al. that they are biogenic in origin. However, exclusively inorganic (abiotic) processes are able to account for the occurrence of carbonate-sulfide-magnetite assemblages in the meteorite. We have previously precipitated chemically zoned and sulfide-bearing carbonate globules analogous to those in ALH84001 (at less than or equal to 150 C) from multiple fluxes of variable-composition Ca-Mg-Fe-CO2-S-H2O solutions. Brief heating of precipitated globules to approx. 470 C produced magnetite and pyrrhotite within the globules by thermal decomposition of siderite and pyrite, respectively. We have also shown that morphology of magnetite formed by inorganic thermal decomposition of Fe-rich carbonate is similar to the morphology of so-called biogenic magnetite in the carbonate globules of ALH84001. Magnetite crystals in the rims of carbonate globules in ALH84001 are chemically pure [Note: "Chemically pure" is defined here as magnetite with Mg at levels comparable or lower than Mg detected by [8] in ALH84001 magnetite]. A debate continues on whether or not chemically pure magnetite can form by the thermal decomposition of mixed Mg-Fe-carbonates that have formed under abiotic conditions. Thomas-Keprta et al. argue that it is not possible to form Mg-free magnetite from Mg-Fe-carbonate based on thermodynamic data. We previously suggested that chemically pure magnetite could form by the thermal decomposition of relatively pure siderite in the outer rims of the globules. Mg-Fe-carbonates may also thermally decompose under conditions conducive for formation of chemically pure magnetite. In this paper we show through laboratory experiments that chemically pure magnetite can form by an inorganic process from mixed Mg-Fe-carbonates.

  14. A Comprehensive Imaging and Raman Spectroscopy Study of ALH84001 and a Terrestrial Analogue from Svalbard

    NASA Astrophysics Data System (ADS)

    Steele, A.; Fries, M.; Amundsen, H. E. F.; Mysen, B.; Fogel, M.; Schweizer, M.; Boctor, N. Z.

    2006-03-01

    We have undertaken a comprehensive Raman microprobe study of a depth profile of ALH84001 and a terrestrial analogue. We find that ALH84001 globules contain hematite as well as magnetite. Macromolecular carbon is always associated with magnetite both in the carbonates and in the bulk matrix.

  15. Submicron Magnetite Grains and Carbon Compounds in Martian Meteorite ALH84001: Inorganic, Abiotic Formation by Shock and Thermal Metamorphism

    NASA Astrophysics Data System (ADS)

    Treiman, Allan H.

    2003-06-01

    Purported biogenic features of the ALH84001 Martian meteorite (the carbonate globules, their submicron magnetite grains, and organic matter) have reasonable inorganic origins, and a comprehensive hypothesis is offered here. The carbonate globules were deposited from hydrothermal water, without biological mediation. Thereafter, ALH84001 was affected by an impact shock event, which raised its temperature nearly instantaneously to 500-700K, and induced iron-rich carbonate in the globules to decompose to magnetite and other minerals. The rapidity of the temperature increase caused magnetite grains to nucleate in abundance; hence individual crystals were very small. Nucleation and growth of magnetite crystals were fastest along edges and faces of the precursor carbonate grains, forcing the magnetite grains to be platy or elongated, including the "truncated hexa-octahedra" shape. ALH84001 had formed at some depth within Mars where the lithostatic pressure was significantly above that of Mars' surface. Also, because the rock was at depth, the impact heat dissipated slowly. During this interval, magnetite crystals approached chemical equilibria with surrounding minerals and gas. Their composition, nearly pure Fe3O4, reflects those of equilibria; elements that substitute into magnetite are either absent from iron-rich carbonate (e.g., Ti, Al, Cr), or partitioned into other minerals during magnetite formation (Mg, Mn). Many microstructural imperfections in the magnetite grains would have annealed out as the rock cooled. In this post-shock thermal regime, carbon-bearing gas from the decomposition of iron carbonates reacted with water in the rock (or from its surroundings) to produce organic matter via Fischer-Tropschlike reactions. Formation of such organic compounds like polycyclic aromatic hydrocarbons would have been catalyzed by the magnetite (formation of graphite, the thermochemically stable phase, would be kinetically hindered).

  16. Submicron magnetite grains and carbon compounds in Martian meteorite ALH84001: inorganic, abiotic formation by shock and thermal metamorphism.

    PubMed

    Treiman, Allan H

    2003-01-01

    Purported biogenic features of the ALH84001 Martian meteorite (the carbonate globules, their submicron magnetite grains, and organic matter) have reasonable inorganic origins, and a comprehensive hypothesis is offered here. The carbonate globules were deposited from hydrothermal water, without biological mediation. Thereafter, ALH84001 was affected by an impact shock event, which raised its temperature nearly instantaneously to 500-700K, and induced iron-rich carbonate in the globules to decompose to magnetite and other minerals. The rapidity of the temperature increase caused magnetite grains to nucleate in abundance; hence individual crystals were very small. Nucleation and growth of magnetite crystals were fastest along edges and faces of the precursor carbonate grains, forcing the magnetite grains to be platy or elongated, including the "truncated hexa-octahedra" shape. ALH84001 had formed at some depth within Mars where the lithostatic pressure was significantly above that of Mars' surface. Also, because the rock was at depth, the impact heat dissipated slowly. During this interval, magnetite crystals approached chemical equilibria with surrounding minerals and gas. Their composition, nearly pure Fe(3)O(4), reflects those of equilibria; elements that substitute into magnetite are either absent from iron-rich carbonate (e.g., Ti, Al, Cr), or partitioned into other minerals during magnetite formation (Mg, Mn). Many microstructural imperfections in the magnetite grains would have annealed out as the rock cooled. In this post-shock thermal regime, carbon-bearing gas from the decomposition of iron carbonates reacted with water in the rock (or from its surroundings) to produce organic matter via Fischer-Tropschlike reactions. Formation of such organic compounds like polycyclic aromatic hydrocarbons would have been catalyzed by the magnetite (formation of graphite, the thermochemically stable phase, would be kinetically hindered). PMID:14577885

  17. The temperature of formation of carbonate in Martian meteorite ALH84001: constraints from cation diffusion

    SciTech Connect

    Hutcheon, I D; Kent, A; Phinney, D L; Ryerson, F J

    1999-08-13

    An important test of the hypothesis that Martian meteorite ALH84001 contains fossil remnants of an ancient Martian biota is the thermal history of the carbonate rosettes associated with the proposed biomarkers. If carbonates formed at temperatures over {approximately} 110 C (the limit for terrestrial life), it is unlikely that these minerals are associated with a terrestrial-like biota.

  18. Evaluation of the formation environment of the carbonates in Martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Niles, Paul Breckenridge

    The carbonates in martian meteorite ALH84001 preserve a record of aqueous processes on Mars at 3.9 Ga, and have been suggested to contain signatures of ancient martian life. The conditions of the carbonate formation environment are critical for understanding possible evidence for life on Mars, the history of water on Mars, and the evolution of the martian atmosphere. However, the formation environment of the ALH84001 carbonates continues to be controversial. New isotopic analyses of the ALH84001 carbonates, laboratory experiments, and geochemical modeling performed in this study provide quantitative constraints on the formation environment of the ALH84001 carbonates. Microscale carbon isotope analyses of ALH84001 carbonates reveal variable d 13 C values ranging from +27[per thousand] to +64[per thousand] that are correlated with carbonate chemical compositions. Isotopic analyses of synthetic hydrothermal carbonates with chemical compositions similar to the ALH84001 carbonates do not show similar isotope compositions, correlations, or trends. Combined with earlier oxygen isotope analyses, these data are inconsistent with formation of the carbonates in previously proposed environments, and indicate that the carbonates formed in a short period of time (hours or days) from a low temperature, dynamic aqueous system. A combination of empirical and equilibrium thermodynamic modeling reveals that the precipitating fluids were Mg- and CO 2 -rich, and probably formed through low temperature (<100°C) leaching of rocks with similar compositions to ALH84001. Prior to precipitating the carbonates, the fluids must have had an Mg/Ca ratio greater than ~4 and an Fe/Ca ratio greater than ~1. Three new hypotheses are proposed that involve low temperature (<100°C), dynamic aqueous processes: the carbonates formed (1) in a sublacustrine spring environment during the mixing of two fluids derived from separate chemical and isotopic reservoirs; (2) from high pH fluids that were exposed

  19. Origin of carbonate-magnetite-sulfide assemblages in Martian meteorite ALH84001.

    PubMed

    Scott, E R

    1999-02-25

    A review of the mineralogical, isotopic, and chemical properties of the carbonates and associated submicrometer iron oxides and sulfides in Martian meteorite ALH84001 provides minimal evidence for microbial activity. Some magnetites resemble those formed by magnetotactic microorganisms but cubic crystals <50 nm in size and elongated grains <25 nm long are too small to be single-domain magnets and are probably abiogenic. Magnetites with shapes that are clearly unique to magnetotactic bacteria appear to be absent in ALH84001. Magnetosomes have not been reported in plutonic rocks and are unlikely to have been transported in fluids through fractures and uniformly deposited where abiogenic magnetite was forming epitaxially on carbonate. Submicrometer sulfides and magnetites probably formed during shock heating. Carbonates have correlated variations in Ca, Mg, and 18O/16O, magnetite-rich rims, and they appear to be embedded in pyroxene and plagiociase glass. Carbonates with these features have not been identified in carbonaceous chondrites and terrestrial rocks, suggesting that the ALH84001 carbonates have a unique origin. Carbonates and hydrated minerals in ALH84001, like secondary phases in other Martian meteorites, have O and H isotopic ratios favoring formation from fluids that exchanged with the Martian atmosphere. I propose that carbonates originally formed in ALH84001 from aqueous fluids and were subsequently shock heated and vaporized. The original carbonates were probably dolomite-magnesite-siderite assemblages that formed in pores at interstitial sites with minor sulfate, chloride, and phyllosilicates. These phases, like many other volatile-rich phases in Martian meteorites, may have formed as evaporate deposits from intermittent floods. PMID:11542931

  20. Reassessment of the "Life on Mars" Hypothesis: Origin of Carbonate-Magnetite Assemblages in Martian Meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Thomas-Keprta, K. L.; Clemett, S. J.; McKay, D. S.; Gibson, E. K.; Wentworth, S. J.; Fei Corporation

    2007-07-01

    We present here the most detailed and comprehensive TEM analyses of the ALH84001 carbonate disks yet obtained. The results indicate that the disks show a subtle complexity that is incompatible with current "simple purely inorganic processes."

  1. Petrography and bulk chemistry of Martian orthopyroxenite ALH84001: implications for the origin of secondary carbonates.

    PubMed

    Gleason, J D; Kring, D A; Hill, D H; Boynton, W V

    1997-08-01

    New petrologic and bulk geochemical data for the SNC-related (Martian) meteorite ALH84001 suggest a relatively simple igneous history overprinted by complex shock and hydrothermal processes. ALH84001 is an igneous orthopyroxene cumulate containing penetrative shock deformation textures and a few percent secondary extraterrestrial carbonates. Rare earth element (REE) patterns for several splits of the meteorite reveal substantial heterogeneity in REE abundances and significant fractionation of the REEs between crushed and uncrushed domains within the meteorite. Complex zoning in carbonates indicates nonequilibrium processes were involved in their formation, suggesting that CO2-rich fluids of variable composition infiltrated the rock while on Mars. We interpret petrographic textures to be consistent with an inorganic origin for the carbonate involving dissolution-replacement reactions between CO2-charged fluids and feldspathic glass in the meteorite. Carbonate formation clearly postdated processes that last redistributed the REE in the meteorite. PMID:11540477

  2. Coordinated In Situ Nanosims Analyses of H-C-O Isotopes in ALH 84001 Carbonates

    NASA Technical Reports Server (NTRS)

    Usui, T.; Alexander, C. M. O'D.; Wang, J.; Simon, J. I.; Jones, J. H.

    2016-01-01

    The surface geology and geomorphology of Mars indicate that it was once warm enough to maintain a large body of liquid water on its surface, though such a warm environment might have been transient. This study reports the hydrogen, carbon, and oxygen isotope compositions of the ancient atmosphere/hydrosphere of Mars based on in situ ion microprobe analyses of approximately 4 Ga-old carbonates in Allan Hills (ALH) 84001. The ALH 84001 carbonates are the most promising targets because they are thought to have formed from fluid that was closely associated with the Noachian atmosphere. While there are a number of carbon and oxygen isotope studies of the ALH 84001 carbonates, in situ hydrogen isotope analyses of these carbonates are limited and were reported more than a decade ago. Well-documented coordinated in situ analyses of carbon, oxygen and hydrogen isotopes provide an internally consistent dataset that can be used to constrain the nature of the Noachian atmosphere/hydrosphere and may eventually shed light on the hypothesis of ancient watery Mars.

  3. Microdistributions of Rb and Sr in ALH84001 carbonates: Chronological implications for secondary alteration on Mars

    SciTech Connect

    Wadhwa, M.; Sutton, S.R.; Flynn, G.J.

    2005-04-22

    Concentrations of Rb and Sr were analyzed on the micron-scale in various compositional zones of the ALH84001 carbonates. Implications of the measured Rb/Sr ratios for the chronology of these carbonates are discussed. ALH84001 is unique among the Martian meteorites in that it has an ancient crystallization age of {approx}4.5 Ga defined by Sm-Nd isotope systematics. Another aspect that differentiates this Martian meteorite from the others is the presence of Ca-Fe-Mg carbonates (modal abundance {approx}1%) that are thought to have been precipitated during alteration in a near-surface environment. Precise age dating of these carbonates is important since it could provide constraints on the timing of surficial secondary alteration processes on Mars. However, this has been a challenging problem owing to the relatively small abundance of the carbonates in ALH84001 and because these carbonates are difficult to separate from the other minerals in the rock by physical and chemical means. Previous investigations have attempted to separate the carbonates by leaching of carbonate-rich mineral fractions. The single 'bulk carbonate' fraction analyzed by Wadhwa and Lugmair was characterized by a low {sup 87}Rb/{sup 86}Sr ratio of {approx}0.05, the lowest of any mineral in ALH84001, and the corresponding Rb-Sr age estimate ({approx}1.39 Ga) was dependent on the assumption of isotopic equilibrium between the carbonates and plagioclase. As pointed out by Borg et al., such an assumption may not be assured and, therefore, they obtained multiple carbonate-rich leachates with a range of {sup 87}Rb/{sup 86}Sr ratios (0.12-2.62) from which they estimated an age of {approx}3.9 Ga. Although these authors performed painstaking chemical characterization to determine contributions in the leachates from minerals such as phosphates and silicates, it is nevertheless difficult to positively rule out contributions from other as yet unidentified phases. Therefore, the goal of the present

  4. Petrologic evidence for low-temperature, possibly flood evaporitic origin of carbonates in the ALH84001 meteorite.

    PubMed

    Warren, P H

    1998-07-25

    High-temperature models for origin of the carbonates in Martian meteorite ALH84001 are implausible. The impact metasomatism model, invoking reaction between CO2 rich fluid and the host orthopyroxenite, requires conversion of olivine into orthopyroxene, yet olivine in ALH84001 shows no depletion in carbonate-rich areas; or else conversion of orthopyroxene into silica, which should have yielded a higher silica/carbonate ratio. The impact melt model implies that the fracture-linked carbonates, as products of melt injection, should appear as continuous planar veins, but in many areas they do not. Both vapor deposition and impact melting seem inconsistent with the zoned poikilotopic texture of many large carbonates. The popular hydrothermal model is inconsistent with the virtual absence of secondary hydrated silicates in ALH84001. Prior brecciation should have facilitated alteration. Hydrothermal fluids would be warm, and rate of hydration of mafic silicates obeys an Arrhenius law, at least up to approximately 100 degrees C. Most important, hydrothermal episodes tend to last for many years. Many areas of the ancient Martian crust show evidence for massive flooding. I propose that the carbonates formed as evaporite deposits from floodwaters that percolated through the fractures of ALH84001, but only briefly, as evaporation and groundwater flow caused the water table to quickly recede beneath the level of this rock during the later stages of the flood episode. The setting might have been a layer of megaregolith beneath a surface catchment of pooled floodwater, analogous to a playa lake. Carbonate precipitation would occur in response to evaporative concentration of the water. To explain the scarcity of sulfates in ALH84001, the water table must be assumed to recede quickly relative to the rate of evaporation. During the period when ALH84001 was above the water table, evaporation would have slowed, as the evaporation front passed beneath the surface of the debris layer

  5. The Hydrological Cycle on Mars as Inferred from the Multi O-isotopic Composition of Carbonates in ALH84001

    NASA Astrophysics Data System (ADS)

    Shaheen, R.; Niles, P. B.; Chong, K.; Thiemens, M. H.

    2011-12-01

    Carbonate minerals provide valuable record of the atmosphere in which they are formed. This work utilizes C and O triple isotopic compositions of the carbonate minerals found in ALH84001 to explore the interaction between atmosphere-hydrosphere and lithosphere. The origin of carbonates found in the Martian meteorite ALH84001 (<1%) is heavily debated with low temperature aqueous precipitation, biogenic production, evaporative processes, high temperature reactions, and impact induced melting and reprecipitation are all candidate processes. These carbonates are heterogeneous chemically (Mg, Ca and Fe-Mn rich) and isotopically (δ13CPDB = +27 to 46 %; δ18OVSMOW = +9.5 to 20.6%) on micrometer scales. Our stepped phosphoric acid dissolution experiments released CO2 from multiple phases of Martian carbonate in the rock (12h acid digestion at 25o C for Ca rich phase and 3h acid digestion at 150oC for Mg rich phase). Both Ca and Mg rich phases showed 0.7% excess 17O (Δ17O = δ17O - 0.52δ18O) in contrast to terrestrial carbonate minerals formed by surficial weathering of the meteorite with no oxygen isotopic anomaly Δ17O ≈ 0 (one hour acid digestion at 25o C). The newly identified Ca-rich carbonate phase is 18O enriched (δ18O = +25%) in contrast to all of the other Ca-rich carbonates previously described. It also contains excess 17O (Δ17O = 0.7%) indicating incorporation of oxygen from an atmospheric source of Martian origin. These oxygen isotope characteristics differentiate this phase from the more commonly described carbonate globules or rosettes and suggest formation from separate aqueous event. This is confirmed by the carbon isotope composition of this new carbonate phase (δ13C= +20%) which differs from the other Martian carbonates in the meteorite and from terrestrial sources. This difference may be an evidence of the long term evolution of carbon isotopes in the atmosphere of Mars. The discovery of highly enriched (O isotopes) Ca-rich phase of Martian

  6. Microscale carbon isotope variability in ALH84001 carbonates and a discussion of possible formation environments

    NASA Astrophysics Data System (ADS)

    Niles, P. B.; Leshin, L. A.; Guan, Y.

    2005-06-01

    The carbonates in martian meteorite ALH84001 preserve a record of aqueous processes on Mars at 3.9 Ga, and have been suggested to contain signatures of ancient martian life. The conditions of the carbonate formation environment are critical for understanding possible evidence for life on Mars, the history of water on Mars, and the evolution of the martian atmosphere. Despite numerous studies of petrographic relationships, microscale oxygen isotope compositions, microscale chemical compositions, and other minerals associated with the carbonates, formation models remain relatively unconstrained. Microscale carbon isotope analyses of ALH84001 carbonates reveal variable δ 13C values ranging from +27 to +64 ‰. The isotopic compositions are correlated with chemical composition and extent of crystallization such that the Mg-poor, early-formed carbonates are relatively 13C depleted and the Mg-rich, later forming carbonates, are 13C enriched. These data are inconsistent with many of the previously proposed environments for carbonate formation, and a new set of hypotheses are proposed. Specifically, two new models that account for the data involve low temperature (<100°C) aqueous processes: (1) the carbonates formed during mixing of two fluids derived from separate chemical and isotopic reservoirs; or (2) the carbonates formed from high pH fluids that are exposed to a CO 2-rich atmosphere and precipitate carbonate, similar to high pH springs on Earth.

  7. New Insights into the Origin of Magnetite Crystals in ALH84001 Carbonate Disks

    NASA Technical Reports Server (NTRS)

    Thomas-Keptra, Katie L.; Clemett, S. J.; Wentworth S. J.; Mckay, D. S.; Gibson, E. K., Jr.

    2010-01-01

    Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks believed to have formed approx.3.9 Ga ago at beginning of the Noachian epoch. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose ori gins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of magnetite and carbonate may be unrelated: that is, from the perspective of the carbonate the magnetite is allochthonous. We have sought to resolve between these hypotheses through the detailed characterized of the compositional and structural relationships between the carbonate disks, their associated magnetites and the orthopyroxene matrix in which they are embedded [1]. Comparison of these results with experimental thermal decomposition studies of sideritic carbonates conducted under a range of heating scenarios suggests that the magnetite nanocrystals in the ALH84001 carbonate disks are not the products of thermal decomposition.

  8. Carbonate formation events in ALH 84001 trace the evolution of the Martian atmosphere

    PubMed Central

    Shaheen, Robina; Niles, Paul B.; Chong, Kenneth; Corrigan, Catherine M.; Thiemens, Mark H.

    2015-01-01

    Carbonate minerals provide critical information for defining atmosphere–hydrosphere interactions. Carbonate minerals in the Martian meteorite ALH 84001 have been dated to ∼3.9 Ga, and both C and O-triple isotopes can be used to decipher the planet’s climate history. Here we report Δ17O, δ18O, and δ13C data of ALH 84001 of at least two varieties of carbonates, using a stepped acid dissolution technique paired with ion microprobe analyses to specifically target carbonates from distinct formation events and constrain the Martian atmosphere–hydrosphere–geosphere interactions and surficial aqueous alterations. These results indicate the presence of a Ca-rich carbonate phase enriched in 18O that formed sometime after the primary aqueous event at 3.9 Ga. The phases showed excess 17O (0.7‰) that captured the atmosphere–regolith chemical reservoir transfer, as well as CO2, O3, and H2O isotopic interactions at the time of formation of each specific carbonate. The carbon isotopes preserved in the Ca-rich carbonate phase indicate that the Noachian atmosphere of Mars was substantially depleted in 13C compared with the modern atmosphere. PMID:25535348

  9. The Carbonates in ALH 84001 Record the Evolution of the Martian Atmosphere Through Multiple Formation Events

    NASA Technical Reports Server (NTRS)

    Shaheen, R.; Niles, P. B.; Corrgan, C.

    2012-01-01

    Current Martian conditions restrict the presence of liquid water due to low temperatures (approx 210K), a thin atmosphere (approx 7mb), and intense UV radiation. However, past conditions on Mars may have been different with the possibility that the ancient Martian climate was warm and wet with a dense CO2 atmosphere. The cycling of carbon on Mars through atmospheric CO2 and carbonate minerals is critical for deciphering its climate history. In particular stable isotopes contained in carbonates can provide information of their origin and formation environment as well as possibly hinting at the composition of global reservoirs such as atmospheric CO2. Martian meteorite ALH 84001 contains widely studied carbonate rosettes that have been dated to approx. 3.9 Ga and have been used to interpret climatic conditions present at that time. However, there is mount-ing evidence for multiple episodes of carbonate formation in ALH 84001 with potentially distinct isotopic compositions. This study seeks to tease out these different carbonate assemblages using stepped phosphoric acid dissolution and analysis of carbon and triple oxygen stable isotopes. In addition, we report SIMS analyses of the delta O-18 several petrographically unusual carbonate phases in the meteorite.

  10. Carbonate formation events in ALH 84001 trace the evolution of the Martian atmosphere.

    PubMed

    Shaheen, Robina; Niles, Paul B; Chong, Kenneth; Corrigan, Catherine M; Thiemens, Mark H

    2015-01-13

    Carbonate minerals provide critical information for defining atmosphere-hydrosphere interactions. Carbonate minerals in the Martian meteorite ALH 84001 have been dated to ∼ 3.9 Ga, and both C and O-triple isotopes can be used to decipher the planet's climate history. Here we report Δ(17)O, δ(18)O, and δ(13)C data of ALH 84001 of at least two varieties of carbonates, using a stepped acid dissolution technique paired with ion microprobe analyses to specifically target carbonates from distinct formation events and constrain the Martian atmosphere-hydrosphere-geosphere interactions and surficial aqueous alterations. These results indicate the presence of a Ca-rich carbonate phase enriched in (18)O that formed sometime after the primary aqueous event at 3.9 Ga. The phases showed excess (17)O (0.7‰) that captured the atmosphere-regolith chemical reservoir transfer, as well as CO2, O3, and H2O isotopic interactions at the time of formation of each specific carbonate. The carbon isotopes preserved in the Ca-rich carbonate phase indicate that the Noachian atmosphere of Mars was substantially depleted in (13)C compared with the modern atmosphere. PMID:25535348

  11. Origin of Magnetite Crystals in Martian Meteorite ALH84001 Carbonate Disks

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K.L.; Clemett, S.J.; McKay, D.S.; Gibson, E. K.; Wentworth, S. J.

    2010-01-01

    Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks which are believed to have precipitated approx.3.9 Ga ago at beginning of the Noachian epoch. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these Fe3O4 are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of Fe3O4 and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. We have sought to resolve between these hypotheses through the detailed characterized of the compositional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded [1]. We focus this discussion on the composition of ALH84001 magnetites and then compare these observations with those from our thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios.

  12. New insights into the origin of magnetite crystals in ALH84001 carbonate disks

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Clemett, S. J.; Wentworth, S. J.; McKay, D. S.; Gibson, E. K.

    2009-01-01

    Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks which are believed to have precipitated approximately 3.9 Ga ago at beginning of the Noachian epoch. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these Fe3O4 are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of Fe3O4 and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. We have sought to resolve between these hypotheses through the detailed characterized of the compositional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded. We focus this discussion on the composition of ALH84001 magnetites and then compare these observations with those from experimental thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios.

  13. Carbonates in ALH 84001: Part of the Story of Water on Mars

    NASA Astrophysics Data System (ADS)

    Corrigan, C. M.

    2004-07-01

    Carbonate-rich regions in ALH 84001 are complicated. There are familiar forms of carbonate as well as fascinating textural forms previously unreported including carbonate rosettes, planiform "slab" carbonates, distinct "post-slab" magnesium carbonates (magnesite), and carbonates interstitial to feldspathic glass and orthopyroxene. Slab carbonates reveal portions of the carbonate growth sequence not seen in the rosettes and suggest that initial nucleating compositions were rich in calcium. They formed in two major stages. The first stage involved growth of the rosettes and slab carbonates. This step was controlled by the rate of crystal nucleation, how fast the ingredients were delivered to the growing crystals, and how much fluid was available. Cosmochemists call this type of growth "kinetically controlled." Next, an alteration event formed the magnesite-siderite (iron carbonate) layers on the exterior surfaces of the carbonate. Post-slab magnesite, intimately associated with silica glass, is compositionally similar to the magnesite in these secondary exterior layers, but represents a later generation of carbonate growth. Formation of feldspathic glasses had little or no thermal effect on carbonates, as indicated by the lack of thermal decomposition or any compositional changes associated with glass/carbonate contacts. The carbonates tell an important story about water in the ancient crust of Mars. The presence of numerous, distinct generations of carbonate formation and relatively clear fracture chronology within carbonate further suggest that interactions between ALH 84001 and the crustal fluids of Mars were discontinuous and occurred only a few times over its 4.5 Ga history. The reactivation and remobilization of fluids (causing events such as formation of magnesite-siderite-magnesite layers and precipitation of post-slab magnesite) and the fracturing within the rock were almost certainly driven by impacts. The evidence for punctuated, impact-driven interaction

  14. Cryogenic Calcite: A Morphologic and Isotopic Analog to the ALH84001 Carbonates

    NASA Technical Reports Server (NTRS)

    Niles, P. B.; Leshin, L. A.; Socki, R. A.; Guan, Y.; Ming, D. W.; Gibson, E. K.

    2004-01-01

    Martian meteorite ALH84001 carbonates preserve large and variable microscale isotopic compositions, which in some way reflect their formation environment. These measurements show large variations (>20%) in the carbon and oxygen isotopic compositions of the carbonates on a 10-20 micron scale that are correlated with chemical composition. However, the utilization of these data sets for interpreting the formation conditions of the carbonates is complex due to lack of suitable terrestrial analogs and the difficulty of modeling under non-equilibrium conditions. Thus, the mechanisms and processes are largely unknown that create and preserve large microscale isotopic variations in carbonate minerals. Experimental tests of the possible environments and mechanisms that lead to large microscale isotopic variations can help address these concerns. One possible mechanism for creating large carbon isotopic variations in carbonates involves the freezing of water. Carbonates precipitate during extensive CO2 degassing that occurs during the freezing process as the fluid s decreasing volume drives CO2 out. This rapid CO2 degassing results in a kinetic isotopic fractionation where the CO2 gas has a much lighter isotopic composition causing an enrichment of 13C in the remaining dissolved bicarbonate. This study seeks to determine the suitability of cryogenically formed carbonates as analogs to ALH84001 carbonates. Specifically, our objective is to determine how accurately models using equilibrium fractionation factors approximate the isotopic compositions of cryogenically precipitated carbonates. This includes determining the accuracy of applying equilibrium fractionation factors during a kinetic process, and determining how isotopic variations in the fluid are preserved in microscale variations in the precipitated carbonates.

  15. ALH84001: The Key to Unlocking Secrets About Mars-15 Years and Counting

    NASA Technical Reports Server (NTRS)

    Gibson, Everett K.; McKay, D. S.; Thomas-Keprta, K. L.; Clemett, S. J.

    2011-01-01

    From the December 27, 1984 discovery of ALH84001, and its subsequent identification as a sample of Mars in 1993, mystery and debate has surrounded the meteorite [1]. With the realization that the ALH84001 sample was a orthopyroxenite and one of the oldest SNC meteorites (approx.4.09 Ga) [2] available to study, important and critical information about the Martian hydrosphere and atmosphere along with the early history and evolution of the planet could be obtained by studying the unique carbonate globules (approx.3.9 Ga) in the sample [3]. The initial work showed the carbonate globules were deposited within fractures and cracks in the host-orthopyroxene by low-temperature aqueous fluids [4]. Ideas that the carbonates were formed at temperatures [5] approaching 800 C were ruled out by later experiments [6]. The 1996 announcement by McKay et al. [7] that ALH84001 contained features which could be interpreted as having a biogenic origin generated considerable excitement and criticism. The NASA Administrator Dan Golden said the 1996 ALH84001 announcement saved NASAs Mars planetary exploration program and injected $6 billion dollars over five years into the scientific research and analysis efforts [8]. All of the original four lines of evidence for possible biogenic features within ALH84001 offered by McKay et al. have withstood the test of time. Criticism has been directed at the interpretation of the 1996 analytical data. Research has expanded to other SNC meteorites. Despite the numerous attacks on the ideas, the debate continues after 15 years. The 2009 paper by Thomas-Keprta et al. [9] on the origins of a suite of magnetites within the ALH84001 has offered strong arguments that some of the magnetites can only be formed by biogenic processes and not from thermal decomposition or shock events which happened to the meteorite. NASA s Astrobiology Institute was formed from the foundation laid by the ALH84001 hypothesis of finding life beyond the Earth. The strong

  16. Atmosphere-surface interactions on Mars: delta 17O measurements of carbonate from ALH 84001.

    PubMed

    Farquhar, J; Thiemens, M H; Jackson, T

    1998-06-01

    Oxygen isotope measurements of carbonate from martian meteorite ALH 84001 (delta18O = 18.3 +/- 0.4 per mil, delta17O = 10.3 +/- 0.2 per mil, and Delta17O = 0.8 +/- 0.05 per mil) are fractionated with respect to those of silicate minerals. These measurements support the existence of two oxygen isotope reservoirs (the atmosphere and the silicate planet) on Mars at the time of carbonate growth. The cause of the atmospheric oxygen isotope anomaly may be exchange between CO2 and O(1D) produced by the photodecomposition of ozone. Atmospheric oxygen isotope compositions may be transferred to carbonate minerals by CO2-H2O exchange and mineral growth. A sink of 17O-depleted oxygen, as required by mass balance, may exist in the planetary regolith. PMID:9616116

  17. Ancient Life on Mars: Application of New Paleomagnetic and Rock Magnetism Techniques to Test the Origin of Magnetites in ALH84001 Carbonates

    NASA Astrophysics Data System (ADS)

    Buz, J.; Kirschvink, J. L.; Kobayashi, A.; Thomas-Keprta, K. L.; Clemett, S. J.

    2014-07-01

    The use of new ultra-high resolution scanning superconducting magnetic microscopes enables us to conduct paleomagnetic and rock magnetism tests which distinguish between formation hypotheses for magnetites found within the ALH84001 carbonates.

  18. Raman Mapping of Carbonates in ALH84001 Martian Meteorite

    NASA Technical Reports Server (NTRS)

    Bell, M. S.; McHone, J.; Kudryavtsev, A.; McKay, D. S.

    2000-01-01

    Raman mapping is utilized to constrain the spatial distribution of fine scale shock effects previously reported from TEM studies. These effects include residual oxides from the formation of magnetite in carbonate and incipient amorphous silica and orthopyroxene.

  19. Covariant C and O Isotope Trends in Some Terrestrial Carbonates and ALH 84001: Possible Linkage Through Similar Formation Processes

    NASA Technical Reports Server (NTRS)

    Volk, Kathryn E.; Niles, Paul B.; Socki, Richard A.

    2011-01-01

    Carbonate minerals found on the surface of Mars and in martian meteorites indicate that liquid water has played a significant role in the planet's history. These findings have raised questions regarding the history of the martian hydrosphere and atmosphere as well as the possibility of life. Sunset Crater, Arizona is a dry environment with relatively high evaporation and brief periods of precipitation. This environment resembles Mars and may make Sunset Crater a good analog to martian carbonates. In this study we sought to identify discrete micro-scale isotopic variation within the carbonate crusts in Sunset Crater to see if they resembled the micro-scale isotope variation found in ALH 84001 carbonates. Sunset Crater carbonate formation may be used as a martian analog and ultimately provide insight into carbonate formation in ALH 84001.

  20. A possible high-temperature origin for the carbonates in the martian meteorite ALH84001.

    PubMed

    Harvey, R P; McSween, H Y

    1996-07-01

    The meteorite Allan Hills (ALH) 84001, commonly accepted to be of martian origin, is unique among known martian meteorites in containing abundant, zoned, pre-terrestrial carbonate minerals. Previous studies of the oxygen isotope compositions of these minerals have suggested that they precipitated from a low-temperature (0-80 degrees C) aqueous fluid in the martian crust--perhaps in a near-surface hydrothermal system. Here we report analyses of the major-element compositions of the carbonates, which provide an independent constraint on the composition and temperature of the fluid from which they formed. We argue that the most likely explanation for the observed compositions, and for the absence of co-existing hydrons minerals, is that the carbonates were formed by reactions between hot (> 650 degrees C), CO2-rich fluids and the ultramatic host rock during an impact event. Impact processes on the martian surface can produce both the hot, CO2-rich fluid (by volatilization of surface carbonates or other CO2 sources) and--by brecciation--the condults through which it flowed. Impact metasomatism is also consistent with the observed oxygen isotope disequillbrium, sequence of mineral formation, and carbonate mineral zoning, reflecting carbonate formation during rapid cooling from high temperatures rather than prolonged exposure to low-temperature fluids. PMID:8657303

  1. Nanophase Magnetite and Pyrrhotite in ALH84001 Martian Meteorite: Evidence for an Abiotic Origin

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Lauer, H. V., Jr. III; Ming, D. W.; Morris, R. V.

    2006-01-01

    The nanophase magnetite crystals in the black rims of pancake-shaped carbonate globules of the Martian meteorite ALH84001 have been studied extensively because of the claim by McKay et al.that they are biogenic in origin. A subpopulation of these magnetite crystals are reported to conform to a unique elongated shape called "truncated hexa-octahedral" or "THO" by Thomas-Keprta et al. They claim these THO magnetite crystals can only be produced by living bacteria thus forming a biomarker in the meteorite. In contrast, thermal decomposition of Fe-rich carbonate has been suggested as an alternate hypothesis for the elongated magnetite formation in ALH84001 carbonates. The experimental and observational evidence for the inorganic formation of nanophase magnetite and pyrrhotite in ALH84001 by decomposition of Fe-rich carbonate in the presence of pyrite are provided.

  2. Carbon- and Sulfur-bearing Minerals in the Martian Meteorite ALH 84001

    NASA Astrophysics Data System (ADS)

    Romanek, C. S.; Thomas, K. L.; Gibson, E. K., Jr.; McKay, D. S.; Socki, R. A.

    1995-09-01

    Unusual carbonate minerals in ALH 84001 [1] provide insights into surficial processes that may have occurred on Mars, but despite detailed geochemical studies [2-4] carbonate petrogenesis has yet to be fully-characterized. High-resolution TEM and SEM analyses were performed on C- and S-bearing mineral grains to better constrain the nature and timing of carbonate mineralization events. Morphological elements: C- and S-bearing minerals in ALH 84001 commonly occur as spheroidal aggregates or fine-grained vug-filling structures. Spheroids are either orange or black, ~150 micrometers (+/- 50 micrometers) in diameter and highly-flattened (10-30 micrometers thick). Orange spheroids have limpid amber-colored cores and white to translucent mantles which are sometimes bound by thin black rims (< 10 micrometers). When viewed under cathodoluminescence, cores are non-luminescent while mantles luminesce a uniform bright-orange color. Black spheroids are less frequently observed; while they are similar in dimension to the orange spheroids they are chemically more heterogeneous. Black irregular aggregates fill residual pore-space between mineral grains. These structures are comprised of extremely fine-grained (< 2 micrometers) material that occasionally forms lenticular stringers up to 50 micrometers in length. Chemistry and Mineralogy: Small grains (30 micrometers dia.) were removed from C- and S-bearing aggregates, microtomed (~100 nm thick) and examined by TEM for imaging, electron diffraction, and elemental analysis. The orange spheroids have cores composed of Fe-Mg-Ca carbonate, with the centers having the highest concentration of Fe (45 mol%) and Ca (15 mol%). The concentration of Mg increases outward to almost pure MgCO3. TEM results support previous analyses of carbonate chemistry [1-4] and clearly indicate that a wide range of Mg-Fe-Ca solid solution exists in carbonate at a scale of ~10 nm. White mantles of the orange spheroids are composed of nearly pure MgCO3 (<5 mol

  3. Sulfide isotopic compositions in shergottites and ALH84001, and possible implications for life on Mars

    SciTech Connect

    Greenwood, J.P.; McSween, H.Y. Jr.; Riciputi, L.R.

    1997-10-01

    The shergottite and ALH84001 meteorites hold keys for understanding geologic and possibly biologic processes on Mars. Recently, it has been proposed that carbonates in ALH84001, and the Fe-sulfides they contain, are products of extraterrestrial biogenic activity. Here we report ion microprobe analyses of sulfides in shergottites and ALH84001. The sulfur isotope ratios of igneous pyrrhotites in shergottites (mean {delta}{sup 34}S{sub CDT}: Shergotty = -0.4{per_thousand}, Zagami = +2.7{per_thousand}, EETA79001A = 1.9{per_thousand}, EETA79001B = -1.7{per_thousand}, LEW88516 = -1.9{per_thousand}, QUE94201 = +0.8{per_thousand}) are similar to those of terrestrial ocean-floor basalts, suggesting that the sulfur isotopic composition of the Martian mantle may be similar to that of the mantle of the Earth. The sulfur isotopic systematics of ALH84001 sulfides are distinct from the shergottites. Measured sulfur isotope ratios of eight pyrite grains ({delta}{sup 34}S{sub CDT} = +2.0 to +7.3{per_thousand}) in crushed zones confirm previously reported analyses of isotopically heavy sulfides and are indistinguishable from an Fe-sulfide zone within a carbonate globule ({delta}{sup 34}S{sub CDT} = +6.0{per_thousand}). Analyses of synthesized, fine-grained mixtures of sulfide, carbonate, and magnetite indicate than the measured sulfur isotope ratio is independent of the presence of carbonate and magnetite in the sputtered volume, confirming the accuracy of the analysis of the fine-grained sulfide in the carbonate globule. Terrestrial biogenic sulfate reduction typically results in light isotopic enrichments. The similarity of {delta}{sup 34}S values of the sulfides in ALH84001 imply that the Fe-sulfide zones within ALH84001 carbonates are probably not the result of bacterial reduction of sulfate. 38 refs., 3 figs., 1 tab.

  4. A Petrographic History of Martian Meteorite ALH84001: Two Shocks and an Ancient Age

    NASA Technical Reports Server (NTRS)

    Treiman, Allan H.

    1995-01-01

    ALH84001 is an igneous meteorite, an orthopyroxenite of martian origin. It contains petrographic evidence of two shock metamorphic events, separated by thermal and chemical events. The evidence for two shock events suggests that ALH84001 is ancient and perhaps a sample of the martian highlands. From petrography and mineral chemistry, the history of ALH84001 must include: crystallization from magma, a first shock (impact) metamorphism, thermal metamorphism, low-temperature chemical alteration, and a second shock (impact) metamorphism. Originally, ALH84001 was igneous, an orthopyroxene-chromite cumulate. In the first shock event, the igneous rock was cut by melt-breccia or cataclastic veinlets, now bands of equigranular fine-grained pyroxene and other minerals (crush zones). Intact fragments of the cumulate were fractured and strained (now converted to polygonized zones). The subsequent thermal metamorphism (possibly related to the first shock) annealed the melt-breccia or cataclastic veinlets to their present granoblastic texture and permitted chemical homogenization of all mineral species present. The temperature of metamorphism was at least 875 C, based on mineral thermometers. Next, Mg-Fe-Ca carbonates and pyrite replaced plagioclase in both clasts and granular bands, producing ellipsoidal carbonate globules with sub-micron scale compositional stratigraphy, repeated identically in all globules, The second shock event produced microfault offsets of carbonate stratigraphy and other mineral contacts, radial fractures around chromite and maskelynite, and strain birefringence in pyroxene. Maskelynite could not have been preserved from the first shock event, because it would have crystallized back to plagioclase. The martian source area for ALH84001 must permit this complex, multiple impact history. Very few craters on young igneous surfaces are on or near earlier impact features. It is more likely that ALH84001 was ejected from an old igneous unit (Hesperian or

  5. Biomarkers in ALH84001???

    NASA Technical Reports Server (NTRS)

    Treiman, Allen H.

    1999-01-01

    D. McKay and colleagues suggested that four sets of features in ALH84001 were biomarkers, signs of an ancient martian biota that once inhabited the meteorite. Subsequent work has not validated their hypothesis; each suggested biomarker has been found to be ambiguous or immaterial. Nor has their hypothesis been disproved. Rather, it is now one of many hypotheses about the alteration of ALH84001. Additional information is contained in the original extended abstract.

  6. Evidence for exclusively inorganic formation of magnetite in Martian meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Ming, D. W.; Morris, R. V.; Brearley, A. J.; Lauer, H. V., Jr.; Treiman, A. H.; Zolensky, M. E.; Schwandt, C. S.; Lofgren, G. E.

    2004-01-01

    Magnetite crystals produced by terrestrial magnetotactic bacterium MV-1 are elongated on a [111] crystallographic axis, in a so-called truncated hexa-Octahedral shape. This morphology has been proposed to constitute a biomarker (i.e., formed only in biogenic processes). A subpopulation of magnetite crystals associated with carbonate globules in Martian meteorite ALH84001 is reported to have this morphology, and the observation has been taken as evidence for biological activity on Mars. In this study, we present evidence for the exclusively inorganic origin of [111]-elongated magnetite crystals in ALH84001. We report three-dimensional(3-D) morphologies for approx.1000 magnetite crystals extracted from: (1) thermal decomposition products of Fe-rich carbonate produced by inorganic hydrothermal precipitation in laboratory experiments; (2) carbonate globules in Martian meteoriteeALH84001; and (3) cells of magnetotactic bacterial strain MV-1. The 3-D morphologies were derived by fitting 3-D shape models to two-dimensional bright-field transmission-electron microscope (TEAM) images obtained at a series of viewing angles. The view down the {110} axes closest to the [111] elongation axis of magnetite crystals ([111]x{110) not equal to 0) provides a 2-D projection that uniquely discriminates among the three [111]-elongated magnetite morphologies found in these samples: [111]-elongated truncated hexaoctahedron ([111]-THO), [111]-elongated cubo-octahedron ([111]-ECO), and [111]-elongated simple octahedron ([111]-ESO). All [111] -elongated morphologies are present in the three types of sample, but in different proportions. In the ALH84001 Martian meteorite and in our inorganic laboratory products, the most common [111]-elongated magnetite crystal morphology is [111]-ECO. In contrast, the most common morphology for magnetotactic bacterial strain MV-1 is [111]-THO. These results show that: (1) the morphology of [111]-elongated magnetite crystals associated with the carbonate

  7. Origin of magnetite crystals in Martian meteorite ALH84001 carbonate disks

    NASA Astrophysics Data System (ADS)

    Thomas-Keprta, Kathie; Clemett, Simon; McKay, David; Gibson, Everett; Wentworth, Susan

    The Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks. These carbonate disks are believed to have precipitated 3.9 Ga ago at beginning of the Noachian epoch on Mars during which both the oldest extant Martian surfaces were formed, and perhaps the earliest global oceans. In-timately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate [1,2]. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate [3,4]. Alternatively, the origins of magnetite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. For example, the magnetites might have already been present in the aqueous fluids from which the carbonates were believed to have been deposited. We have sought to resolve between these hypotheses through the detailed characterization of the compositional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded. Extensive use of focused ion beam milling techniques has been utilized for sample preparation. We then compared our ob-servations with those from experimental thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios. We conclude that the vast majority of the nanocrystal magnetites present in the carbonate disks could not have formed by any of the currently proposed thermal decomposition scenarios. Instead, we find there is considerable evidence in support of an alternative allochthonous origin for the magnetite unrelated to any shock or thermal processing of the carbonates [5]. [1] McKay et al. (1996) Science 273, 924-930. [2] Thomas-Keprta et al. (2001) Proc. Natl. Acad. Sci. 98, 2164

  8. Morphological Evidence for an Exclusively Inorganic Origin for Magnetite in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Ming, D. W.; Morris, R. V.; Brearley, A. J.; Lauer, H. V., Jr.; Treiman, A.; Zolensky, M. E.; Schwandt, C. S.; Lofgren, G. E.; McKay, G. A.

    2003-01-01

    The origin of magnetite crystals in Martian Meteorite ALH84001 is the focus of a debate about the possibility of past (and present) life on Mars. McKay et al. originally suggested that some of the magnetite crystals associated with carbonate globules in Martian Meteorite ALH84001 are biogenic in ori-gin, because they are single magnetic domain, free of crystalline defects, chemically pure, and coexist with other metastable phases in apparent disequilibrium. Thomas-Keprta et al. reported that a subpopulation of magnetite crystals (approx. 25%) associated with carbonate globules in ALH84001 and magnetite crystals produced by magnetotactic bacterial strain MV-1 have similar morphologies with crystal elongation along the [111] crystallographic axis that they describe as "truncated hexa-octahedral" ([111-THO]) magnetite. Along with several other properties, the [111]-THO morphology has been proposed to constitute a biomarker (i.e., formed only in biogenic processes), so that the presence of [111]-THO magnetite in ALH84001 may be evidence for past life on Mars.

  9. Truncated Hexa-Octahedral Magnetite Crystals in Martian Meteorite ALH84001: Evidence of Biogenic Activity on Early Mars

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K.; Clemett, S. J.; Schwartz, C.; McIntosh, J. R.; Bazylinski, D. A.; Kirschvink, J.; McKay, D. S.; Gibson, E. K.; Vali, H.; Romanek, C. S.

    2004-01-01

    The landmark paper by McKay et al. [1] cited four lines of evidence associated with the Martian meteorite ALH84001 to support the hypothesis that life existed on Mars approximately 4 Ga ago. Now, more than five years later, attention has focused on the ALH84001 magnetite grains embedded within carbonate globules in the ALH84001 meteorite. We have suggested that up to approx.25% of the ALH84001 magnetite crystals are products of biological activity [e.g., 2]. The remaining magnetites lack sufficient characteristics to constrain their origin. The papers of Thomas Keprta et al. were criticized arguing that the three dimensional structure of ALH84001 magnetite crystals can only be unambiguously determined using electron tomographic techniques. Clemett et al. [3] confirmed that magnetites produced by magnetotactic bacteria strain MV-I display a truncated hexa-octahedral geometry using electron tomography and validated the use of the multi-tilt classical transmission microscopy technique used by [2]. Recently the geometry of the purported martian biogenic magnetites was shown be identical to that for MV-1 magnetites using electron tomography [6].

  10. Low-temperature carbonate concretions in the Martian meteorite ALH84001: evidence from stable isotopes and mineralogy.

    PubMed

    Valley, J W; Eiler, J M; Graham, C M; Gibson, E K; Romanek, C S; Stolper, E M

    1997-03-14

    The martian meteorite ALH84001 contains small, disk-shaped concretions of carbonate with concentric chemical and mineralogical zonation. Oxygen isotope compositions of these concretions, measured by ion microprobe, range from delta18O = +9.5 to +20.5 per thousand. Most of the core of one concretion is homogeneous (16.7 +/- 1.2 per thousand) and over 5 per thousand higher in delta18O than a second concretion. Orthopyroxene that hosts the secondary carbonates is isotopically homogeneous (delta18O = 4.6 +/- 1.2 per thousand). Secondary SiO2 has delta18O = 20.4 per thousand. Carbon isotope ratios measured from the core of one concretion average delta13C = 46 +/- 8 per thousand, consistent with formation on Mars. The isotopic variations and mineral compositions offer no evidence for high temperature (>650 degrees C) carbonate precipitation and suggest non-equilibrium processes at low temperatures (< approximately 300 degrees C). PMID:9054355

  11. ALH84001: The Key to Unlocking Secrets About Mars-15 Years and Counting

    NASA Technical Reports Server (NTRS)

    Gibson, Everett K.

    2011-01-01

    From the December 27, 1984 discovery of ALH84001, and its subsequent identification as a sample of Mars in 1993, mystery and debate has surrounded the meteorite. With the realization that the ALH84001 sample was a orthopyroxenite and one of the oldest SNC meteorites (4.09 Ga) available to study, important and critical information about the Martian hydrosphere and atmosphere along with the early history and evolution of the planet could be obtained by studying the unique carbonate globules (3.9 Ga) in the sample. The initial work showed the carbonate globules were deposited within fractures and cracks in the host-orthopyroxene by low-temperature aqueous fluids. Ideas that the carbonates were formed at temperatures approaching 800oC were ruled out by later experiments. The 1996 announcement by McKay et al. that ALH84001 contained features which could be interpreted as having a biogenic origin generated considerable excitement and criticism. The NASA Administrator Dan Golden said the 1996 ALH84001 announcement saved NASA s Mars planetary exploration program and injected $6 billion dollars over five years into the scientific research and analysis efforts. All of the original four lines of evidence for possible biogenic features within ALH84001 offered by McKay et al. have withstood the test of time. Criticism has been directed at the interpretation of the 1996 analytical data. Research has expanded to other SNC meteorites. Despite the numerous attacks on the ideas, the debate continues after 15 years. The 2009 paper by Thomas-Keprta et al. on the origins of a suite of magnetites within the ALH84001 has offered strong arguments that some of the magnetites can only be formed by biogenic processes and not from thermal decomposition or shock events which happened to the meteorite. NASA s Astrobiology Institute was formed from the foundation laid by the ALH84001 hypothesis of finding life beyond the Earth. The strong astrobiology outreach programs have expanded because of

  12. Stable Isotope Enrichment of Carbonate from the Martian Meteorite ALH84001: Test of a Hypothesis at Wright Valley, Antarctica

    NASA Astrophysics Data System (ADS)

    Socki, R. A.; Gibson, E. K., Jr.; Romanek, C. S.

    1995-09-01

    We report here the stable isotope composition of carbonate measured from a suite of desert soils from the Dry Valleys of Antarctica [1] to determine the 13C enrichments attributed to cryogenic freezing in terrestrial environments. These data are then used to gauge whether cryogenic freezing is a viable aqueous process that can produce extreme 13C enrichments observed in Martian carbonates (e.g., ALH 84001 [2]). Analyses of ALH 84001 have shown that the delta^(13)C of carbonate is the most-positive yet recorded for an SNC meteorite (ca. 42 per mil)[2]. The source of carbon is thought to be Martian atmospheric CO2, which has been recycled through an aqueous medium into the solid phase. The delta^(13)C of the carbonate is consistent with a precipitation temperature below ~300 degrees C [3], assuming the delta^(13)C of Martian CO2 lies somewhere between 26 and 46 per mil [4, 5]. An equilibrium temperature of formation near 0 degrees C is difficult to reconcile if the atmospheric source of carbon is <26 per mil, despite the fact that equilbrium isotope enrichments are large at this temperature (12-14 per mil) [6-8]. Low delta^(13)C for atmospheric CO2 is only compatible with high delta^(13)C for carbonate when non-equilibrium processes are the primary mechanism of isotopic fractionation. An inorganic surficial process known to enrich carbonate by >15 per mil over ambient atmospheric CO2 is cryogenic freezing [9]. Carbonate-bearing soils from Wright Valley, Antarctica were studied as a terrestrial analog to the carbonates in ALH 84001 to characterize isotopic "fingerprints" associated with cryogenic freezing. delta^(13)C and delta^(18)O carbonate values from Prospect Mesa Soil Pit range from +0.89 per mil to -20.46 per mil (PDB) within the "permanently frozen zone" (below 0.4 m), and +4.20 per mil to -11.87 per mil at the surface. The most enriched 13C and 18O tend to occur at the surface where seasonal variations in temperature or precipitation have imposed cyclical

  13. Stable Isotope Enrichment of Carbonate from the Martian Meteorite ALH84001: Test of a Hypothesis at Wright Valley, Antarctica

    NASA Astrophysics Data System (ADS)

    Socki, R. A.; Gibson, E. K., Jr.; Romanek, C. S.

    1995-09-01

    We report here the stable isotope composition of carbonate measured from a suite of desert soils from the Dry Valleys of Antarctica [1] to determine the 13C enrichments attributed to cryogenic freezing in terrestrial environments. These data are then used to gauge whether cryogenic freezing is a viable aqueous process that can produce extreme 13C enrichments observed in Martian carbonates (e.g., ALH 84001 [2]). Analyses of ALH 84001 have shown that the delta^(13)C of carbonate is the most-positive yet recorded for an SNC meteorite (ca. 42 per mil)[2]. The source of carbon is thought to be Martian atmospheric CO2, which has been recycled through an aqueous medium into the solid phase. The delta^(13)C of the carbonate is consistent with a precipitation temperature below ~300 degrees C [3], assuming the delta^(13)C of Martian CO2 lies somewhere between 26 and 46 per mil [4, 5]. An equilibrium temperature of formation near 0 degrees C is difficult to reconcile if the atmospheric source of carbon is <26 per mil, despite the fact that equilbrium isotope enrichments are large at this temperature (12-14 per mil) [6-8]. Low delta^(13)C for atmospheric CO2 is only compatible with high delta^(13)C for carbonate when non-equilibrium processes are the primary mechanism of isotopic fractionation. An inorganic surficial process known to enrich carbonate by >15 per mil over ambient atmospheric CO2 is cryogenic freezing [9]. Carbonate-bearing soils from Wright Valley, Antarctica were studied as a terrestrial analog to the carbonates in ALH 84001 to characterize isotopic "fingerprints" associated with cryogenic freezing. delta^(13)C and delta^(18)O carbonate values from Prospect Mesa Soil Pit range from +0.89 per mil to -20.46 per mil (PDB) within the "permanently frozen zone" (below 0.4 m), and +4.20 per mil to -11.87 per mil at the surface. The most enriched 13C and 18O tend to occur at the surface where seasonal variations in temperature or precipitation have imposed cyclical

  14. Low-temperature carbonate concretions in the martian meteorite ALH84001: Evidence from stable isotopes and mineralogy

    SciTech Connect

    Valley, J.W.; Eiler, J.M.; Stolper, E.M.

    1997-03-14

    The martian meteorite ALH84001 contains small, disk-shaped concentrations of carbonate with concentric chemical and mineralogical zonation. Oxygen isotope compositions of these concretions, measured by ion microprobe, range from {delta}{sup 18}O = +9.5 to +20.5{per_thousand}. Most of the core of one concretion is homogeneous (16.7 {+-} 1.2{per_thousand}) and over 5{per_thousand} higher in ({delta}{sup 18}O = 4.6 {+-} 1.2{per_thousand}). Secondary SiO{sub 2} has {delta}{sup 18}O = 20.4{per_thousand}. Carbon isotope ratios measured from the core of one concretion average {delta}{sup 13}C = 46 {+-} 8{per_thousand}, consistent with formation on Mars. The isotopic variations and mineral compositions offer no evidence for high temperature (>650{degrees}C) carbonate precipitation and suggest non-equilibrium processes at low temperatures (<{approximately} 300{degrees}C). 44 refs., 3 figs., 1 tab.

  15. Originof magnetite in martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Scott, E.; Fuller, M.

    2003-04-01

    The magnetization of ALH84001 is predominantly carried by single domain magnetite, which is found in association with carbonate. The magnetite is found in topotactic relationship with the carbonate in regions of iron rich carbonate, whereas in magnesium richer areas periclase is found. The magnetite formed from the carbonate by thermal decomposition of siderite at elevated temperature in a major impact event at about 4.0 Gyr. Chromite is also present in large amounts, but it is predominantly paramagnetic at room temperature with a Neel point close to 100^oK. Carbonate with associated magnetite is also found in the martian meteorite Nakhla. Experiments and theory show that siderite is a major product of percolation and evaporation of brines generated under pressures of more than 0.1bar of carbon dioxide. This is the preferred explanation for the carbonate in nakhla, as well as in ALH84001. Thermal decomposition of siderite may result from deep burial, magmatic heat sources, or as in the case of ALH84001, impact heating.

  16. Formation of Carbonate Minerals in Martian Meteorite ALH 84001 from Cool Water Near the Surface of Mars

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    2011-12-01

    Carbonate minerals in the Allan Hills 84001 meteorite are important because they ought to contain information about the chemistry and temperature of the water they formed in. They are also an important part of testing the idea that the meteorite contains evidence of past life on Mars. Hypotheses for the origin of the carbonates are impressively varied. A key test of the ideas is to determine the temperature at which the carbonates formed. Estimates up to now range from a bit below freezing to 700 oC, too big a range to test anything! To address the problem Itay Halevy, Woodward Fischer, and John Eiler (Caltech) used an approach that involves "clumped" isotope thermometry, which makes comparisons among different isotopic compositions of extracted CO2. This allowed the investigators to use the isotopic abundances of both carbon and oxygen. The results indicate that the carbonates formed at 18 ± 4 oC from a shallow subsurface (upper few meters to tens of meters) pool of water that was gradually evaporating. The wet episode did not last long, leading Halevy and his colleagues to conclude that the environment may have been too transient for life to have emerged here from scratch. On the other hand, if life already existed on the Martian surface this wet near-surface environment would have provided a happy home. An impact blasted the Martian home of ALH 84001, causing a transient heating event, perhaps disturbing the isotopic record...or perhaps not because the event was so short. In any case, the clumped isotope thermometry approach seems to have given a good measurement of the temperature at which the carbonate minerals formed.

  17. Search for Past Life on Mars: Possible Relict Biogenic Activity in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    McKay, David S.; Gibson, Everett K., Jr.; Thomas-Keprta, Kathie L.; Vali, Hojatollah; Romanek, Christopher S.; Clemett, Simon J.; Chillier, Xavier D. F.; Maechling, Claude R.; Zare, Richard N.

    1996-01-01

    Fresh fracture surfaces of the martian meteorite ALH84001 contain abundant polycyclic aromatic hydrocarbons (PAHs). These fresh fracture surfaces also display carbonate globules. Contamination studies suggest the PAHs are indigenous to the meteorite. High resolution scanning and transmission electron microscopy study of surface textures and internal structures of selected carbonate globules show that the globules contain fine-grained, secondary phases of single-domain magnetite and Fe-monosulfides. The carbonate globules are similar in texture and size to some terrestrial bacterially induced carbonate precipitates. Although inorganic formation is possible, formation of the globules by biogenic processes could explain many of the observed features including the PAHs. The PAHs, the carbonate globules, and their associated secondary mineral phases and textures could thus be fossil remains of a past martian biota.

  18. Search for past life on Mars: possible relic biogenic activity in martian meteorite ALH84001.

    PubMed

    McKay, D S; Gibson, E K; Thomas-Keprta, K L; Vali, H; Romanek, C S; Clemett, S J; Chillier, X D; Maechling, C R; Zare, R N

    1996-08-16

    Fresh fracture surfaces of the martian meteorite ALH84001 contain abundant polycyclic aromatic hydrocarbons (PAHs). These fresh fracture surfaces also display carbonate globules. Contamination studies suggest that the PAHs are indigenous to the meteorite. High-resolution scanning and transmission electron microscopy study of surface textures and internal structures of selected carbonate globules show that the globules contain fine-grained, secondary phases of single-domain magnetite and Fe-sulfides. The carbonate globules are similar in texture and size to some terrestrial bacterially induced carbonate precipitates. Although inorganic formation is possible, formation of the globules by biogenic processes could explain many of the observed features, including the PAHs. The PAHs, the carbonate globules, and their associated secondary mineral phases and textures could thus be fossil remains of a past martian biota. PMID:8688069

  19. Thermal Decomposition of an Impure (Roxbury) Siderite: Relevance to the Presence of Chemically Pure Magnetite Crystals in ALH84001 Carbonate Disks

    NASA Technical Reports Server (NTRS)

    McKay, D.S.; Gibson, E.K.; Thomas-Keprta, K.L.; Clemett, S.J.; Wentworth, S.J.

    2009-01-01

    The question of the origin of nanophase magnetite in Martian meteorite ALH84001 has been widely debated for nearly a decade. Golden et al. have reported producing nearly chemically pure magnetite from thermal decomposition of chemically impure siderite [(Fe, Mg, Mn)CO3]. This claim is significant for three reasons: first, it has been argued that chemically pure magnetite present in the carbonate disks in Martian meteorite ALH84001 could have formed by the thermal decomposition of the impure carbonate matrix in which they are embedded; second, the chemical purity of magnetite has been previously used to identify biogenic magnetite; and, third, previous studies of thermal decomposition of impure (Mg,Ca,Mn)-siderites, which have been investigated under a wide variety of conditions by numerous researchers, invariably yields a mixed metal oxide phase as the product and not chemically pure magnetite. The explanation for this observation is that these siderites all possess the same crystallographic structure (Calcite; R3c) so solid solutions between these carbonates are readily formed and can be viewed on an atomic scale as two chemically different but structurally similar lattices.

  20. Magnetic tests for magnetosome chains in Martian meteorite ALH84001.

    PubMed

    Weiss, Benjamin P; Kim, Soon Sam; Kirschvink, Joseph L; Kopp, Robert E; Sankaran, Mohan; Kobayashi, Atsuko; Komeili, Arash

    2004-06-01

    Transmission electron microscopy studies have been used to argue that magnetite crystals in carbonate from Martian meteorite ALH84001 have a composition and morphology indistinguishable from that of magnetotactic bacteria. It has even been claimed from scanning electron microscopy imaging that some ALH84001 magnetite crystals are aligned in chains. Alignment of magnetosomes in chains is perhaps the most distinctive of the six crystallographic properties thought to be collectively unique to magnetofossils. Here we use three rock magnetic techniques, low-temperature cycling, the Moskowitz test, and ferromagnetic resonance, to sense the bulk composition and crystallography of millions of ALH84001 magnetite crystals. The magnetic data demonstrate that although the magnetite is unusually pure and fine-grained in a manner similar to terrestrial magnetofossils, most or all of the crystals are not arranged in chains. PMID:15155900

  1. Magnetic tests for magnetosome chains in Martian meteorite ALH84001

    PubMed Central

    Weiss, Benjamin P.; Kim, Soon Sam; Kirschvink, Joseph L.; Kopp, Robert E.; Sankaran, Mohan; Kobayashi, Atsuko; Komeili, Arash

    2004-01-01

    Transmission electron microscopy studies have been used to argue that magnetite crystals in carbonate from Martian meteorite ALH84001 have a composition and morphology indistinguishable from that of magnetotactic bacteria. It has even been claimed from scanning electron microscopy imaging that some ALH84001 magnetite crystals are aligned in chains. Alignment of magnetosomes in chains is perhaps the most distinctive of the six crystallographic properties thought to be collectively unique to magnetofossils. Here we use three rock magnetic techniques, low-temperature cycling, the Moskowitz test, and ferromagnetic resonance, to sense the bulk composition and crystallography of millions of ALH84001 magnetite crystals. The magnetic data demonstrate that although the magnetite is unusually pure and fine-grained in a manner similar to terrestrial magnetofossils, most or all of the crystals are not arranged in chains. PMID:15155900

  2. Magnetic tests for magnetosome chains in Martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Weiss, Benjamin P.; Kim, Soon Sam; Kirschvink, Joseph L.; Kopp, Robert E.; Sankaran, Mohan; Kobayashi, Atsuko; Komeili, Arash

    2004-06-01

    Transmission electron microscopy studies have been used to argue that magnetite crystals in carbonate from Martian meteorite ALH84001have a composition and morphology indistinguishable from that of magnetotactic bacteria. It has even been claimed from scanning electron microscopy imaging that some ALH84001magnetite crystals are aligned in chains. Alignment of magnetosomes in chains is perhaps the most distinctive of the six crystallographic properties thought to be collectively unique to magnetofossils. Here we use three rock magnetic techniques, low-temperature cycling, the Moskowitz test, and ferromagnetic resonance, to sense the bulk composition and crystallography of millions of ALH84001magnetite crystals. The magnetic data demonstrate that although the magnetite is unusually pure and fine-grained in a manner similar to terrestrial magnetofossils, most or all of the crystals are not arranged in chains.

  3. Covariant C and O Isotope Trends in Arctic Carbonate Crusts and ALH 84001: Potential Biomarker or Indicator of Cryogenic Formation Environment?

    NASA Technical Reports Server (NTRS)

    Socki, Richard A.; Niles, Paul B.; Blake, Weston; Leveille, Richard

    2009-01-01

    This work seeks to use the chemical, isotopic, and mineralogical characteristics of secondary carbonate minerals produced during brief aqueous events to identify the conditions of the aqueous environment in which they formed. Liquid water near the surface of Mars is subject to either rapid freezing and/or evaporation. These processes are also active on Earth, and produce secondary minerals that have complex chemical, mineralogical, and isotopic textures and compositions that can include covariant relationships between Delta C-13 (sub VPDB) and delta O-18 (sub VSMOW). The extremely well studied four billion year old carbonates preserved in martian meteorite ALH 84001 also show covariant delta C-13 and delta O-18 compositions, but these variations are manifested on a micro-scale in a single thin section while the variation observed so far in terrestrial carbonates is seen between different hand samples.

  4. Paleomagnetic record of Martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Antretter, Maria; Fuller, Mike; Scott, Edward; Jackson, Mike; Moskowitz, Bruce; Solheid, Peter

    2003-06-01

    The natural remanent magnetization (NRM) of the Martian meteorite ALH84001 is predominantly carried by fine magnetite, which is found in association with carbonate. The magnetite is in epitaxial and topotactic relation with the carbonate and formed from the carbonate in the major impact event at 4.0 Ga. The NRM will therefore record this field. The local preferential crystallographic and shape alignment of the magnetite defines local easy directions of magnetization may account for the observed inhomogeneity of the NRM on a microscopic scale. Normalizing the intensity of the NRM by the saturation isothermal remanence (IRMs) then gives an estimate for the 4.0 Ga Martian field one order smaller than the present geomagnetic field. Such a field is unlikely to be strong enough to generate the high-intensity Martian magnetic anomalies. ALH 84001 in its pristine state as an orthopyroxenite is not a plausible source rock for the Martian anomalies because its magnetite was not formed until the 4.0 Ga event.

  5. Magnetic Tests For Magnetosome Chains In Martian Meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Weiss, B. P.; Kim, S.; Kirschvink, J. L.; Sankaran, M.; Kobayashi, A.; Komeili, A.

    2003-12-01

    Transmission electron microscopy studies have been used to argue that magnetites in carbonates from Martian meteorite ALH84001 have a composition and morphology indistinguishable from that of magnetotactic bacteria and their magnetofossils (1). It has even been claimed from scanning electron microscopy imaging that some ALH84001 magnetites are aligned in chains (2). If true, this would provide dramatic support for the magnetofossil hypothesis because alignment in chains is perhaps the most distinctive of the six crystallographic properties thought to be collectively unique to magnetosomes. The leading alternative hypothesis is that the ALH84001 magnetites are the inorganic products of shock-heating of the carbonates (3, 4). Here we use three rock magnetic techniques-low-temperature cycling, the Moskowitz test (5), and ferromagnetic resonance (FMR)-to demonstrate that most or all of the magnetites in ALH84001 are unusually pure and fine-grained but are not arranged in magnetosome chains. 1. K. L. Thomas-Keprta et al., Geochim. Cosmochim. Acta 64, 4049-4081 (2000). 2. I. E. Friedmann, J. Wierzchos, C. Ascaso, M. Winklhofer, Proc. Natl. Acad. Sci. USA 98, 2176-2181 (2001). 3. D. C. Golden et al., Am. Mineral. 83, 370-375 (2001). 4. D. J. Barber, E. R. D. Scott, Proc. Natl. Acad. Sci. USA 99, 6556-6561 (2002). 5. B. M. Moskowitz, R. B. Frankel, D. A. Bazylinski, Earth Planet. Sci. Lett. 120, 283-300 (1993).

  6. Thermal Decomposition of an Impure (Roxbury) Siderite: Relevance to the Presence of Chemically Pure Magnetite Crystals in ALH84001 Carbonate Disks

    NASA Astrophysics Data System (ADS)

    Thomas-Keprta, K. L.; Clemett, S. J.; McKay, D. S.; Gibson, E. K.; Wentworth, S. J.

    2009-03-01

    Thermal decomposition of Roxbury siderite resulted in the formation of impure (Mg,Mn)-ferrites. These findings, which are supported by kinetic and thermodynamic equilibrium modeling studies, are in stark contrast to the chemically pure ALH 84001 magnetite.

  7. Truncated hexa-octahedral magnetite crystals in ALH84001: presumptive biosignatures

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Clemett, S. J.; Bazylinski, D. A.; Kirschvink, J. L.; McKay, D. S.; Wentworth, S. J.; Vali, H.; Gibson, E. K. Jr; McKay, M. F.; Romanek, C. S.

    2001-01-01

    McKay et al. [(1996) Science 273, 924-930] suggested that carbonate globules in the meteorite ALH84001 contained the fossil remains of Martian microbes. We have characterized a subpopulation of magnetite (Fe(3)O(4)) crystals present in abundance within the Fe-rich rims of these carbonate globules. We find these Martian magnetites to be both chemically and physically identical to terrestrial, biogenically precipitated, intracellular magnetites produced by magnetotactic bacteria strain MV-1. Specifically, both magnetite populations are single-domain and chemically pure, and exhibit a unique crystal habit we describe as truncated hexa-octahedral. There are no known reports of inorganic processes to explain the observation of truncated hexa-octahedral magnetites in a terrestrial sample. In bacteria strain MV-1 their presence is therefore likely a product of Natural Selection. Unless there is an unknown and unexplained inorganic process on Mars that is conspicuously absent on the Earth and forms truncated hexa-octahedral magnetites, we suggest that these magnetite crystals in the Martian meteorite ALH84001 were likely produced by a biogenic process. As such, these crystals are interpreted as Martian magnetofossils and constitute evidence of the oldest life yet found.

  8. Truncated hexa-octahedral magnetite crystals in ALH84001: Presumptive biosignatures

    PubMed Central

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Bazylinski, Dennis A.; Kirschvink, Joseph L.; McKay, David S.; Wentworth, Susan J.; Vali, Hojatollah; Gibson, Everett K.; McKay, Mary Fae; Romanek, Christopher S.

    2001-01-01

    McKay et al. [(1996) Science 273, 924–930] suggested that carbonate globules in the meteorite ALH84001 contained the fossil remains of Martian microbes. We have characterized a subpopulation of magnetite (Fe3O4) crystals present in abundance within the Fe-rich rims of these carbonate globules. We find these Martian magnetites to be both chemically and physically identical to terrestrial, biogenically precipitated, intracellular magnetites produced by magnetotactic bacteria strain MV-1. Specifically, both magnetite populations are single-domain and chemically pure, and exhibit a unique crystal habit we describe as truncated hexa-octahedral. There are no known reports of inorganic processes to explain the observation of truncated hexa-octahedral magnetites in a terrestrial sample. In bacteria strain MV-1 their presence is therefore likely a product of Natural Selection. Unless there is an unknown and unexplained inorganic process on Mars that is conspicuously absent on the Earth and forms truncated hexa-octahedral magnetites, we suggest that these magnetite crystals in the Martian meteorite ALH84001 were likely produced by a biogenic process. As such, these crystals are interpreted as Martian magnetofossils and constitute evidence of the oldest life yet found. PMID:11226210

  9. Truncated hexa-octahedral magnetite crystals in ALH84001: presumptive biosignatures.

    PubMed

    Thomas-Keprta, K L; Clemett, S J; Bazylinski, D A; Kirschvink, J L; McKay, D S; Wentworth, S J; Vali, H; Gibson, E K; McKay, M F; Romanek, C S

    2001-02-27

    McKay et al. [(1996) Science 273, 924-930] suggested that carbonate globules in the meteorite ALH84001 contained the fossil remains of Martian microbes. We have characterized a subpopulation of magnetite (Fe(3)O(4)) crystals present in abundance within the Fe-rich rims of these carbonate globules. We find these Martian magnetites to be both chemically and physically identical to terrestrial, biogenically precipitated, intracellular magnetites produced by magnetotactic bacteria strain MV-1. Specifically, both magnetite populations are single-domain and chemically pure, and exhibit a unique crystal habit we describe as truncated hexa-octahedral. There are no known reports of inorganic processes to explain the observation of truncated hexa-octahedral magnetites in a terrestrial sample. In bacteria strain MV-1 their presence is therefore likely a product of Natural Selection. Unless there is an unknown and unexplained inorganic process on Mars that is conspicuously absent on the Earth and forms truncated hexa-octahedral magnetites, we suggest that these magnetite crystals in the Martian meteorite ALH84001 were likely produced by a biogenic process. As such, these crystals are interpreted as Martian magnetofossils and constitute evidence of the oldest life yet found. PMID:11226210

  10. Cryogenic Origin for Mars Analog Carbonates in the Bockfjord Volcanic Complex Svalbard (Norway)

    NASA Technical Reports Server (NTRS)

    Amundsen, H. E. F.; Benning, L.; Blake, D. F.; Fogel, M.; Ming, D.; Skidmore, M.; Steele, A.

    2011-01-01

    The Sverrefjell and Sigurdfjell eruptive centers in the Bockfjord Volcanic Complex (BVC) on Svalbard (Norway) formed by subglacial eruptions ca. 1 Ma ago. These eruptive centers carry ubiquitous magnesian carbonate deposits including dolomitemagnesite globules similar to those in the Martian meteorite ALH84001. Carbonates in mantle xenoliths are dominated by ALH84001 type carbonate globules that formed during quenching of CO2-rich mantle fluids. Lava hosted carbonates include ALH84001 type carbonate globules occurring throughout lava vesicles and microfractures and massive carbonate deposits associated with vertical volcanic vents. Massive carbonates include < or equal 5 cm thick magnesite deposits protruding downwards into clear blue ice within volcanic vents and carbonate cemented lava breccias associated with volcanic vents. Carbonate cements comprise layered deposits of calcite, dolomite, huntite, magnesite and aragonite associated with ALH84001 type carbonate globules lining lava vesicles. Combined Mossbauer, XRD and VNIR data show that breccia carbonate cements at Sverrefjell are analog to Comanche carbonates at Gusev crater.

  11. Biomimetic Properties of Minerals and the Search for Life in the Martian Meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Martel, Jan; Young, David; Peng, Hsin-Hsin; Wu, Cheng-Yeu; Young, John D.

    2012-05-01

    The existence of extraterrestrial life was heralded by controversial claims made in 1996 that the Martian meteorite ALH84001 harbored relics of ancient microorganisms. We review here the accumulated evidence for and against past extraterrestrial life in this Martian meteorite. The main pro-life arguments—the presence of polycyclic aromatic hydrocarbons, magnetite crystals, carbonate globules, and structures resembling terrestrial life-forms known as nanobacteria—can be deemed ambiguous at best. Although these criteria are compatible with living processes, each one of them can be explained by nonliving chemical processes. By undergoing amorphous-to-crystalline transformations and binding to multiple substrates, including other ions and simple organic compounds, minerals—especially those containing carbonate—have been shown to display biomimetic properties, producing forms that resemble bacteria. This simple and down-to-earth explanation can account fully for the existence of mineral entities resembling putative nano- and microorganisms that have been described not only in the ALH84001 meteorite but also in the human body.

  12. Mars Life? - Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    1996-01-01

    This 4.5 billion-year-old rock, labeled meteorite ALH84001, is believed to have once been a part of Mars and to contain fossil evidence that primitive life may have existed on Mars more than 3.6 billion years ago. The rock is a portion of a meteorite that was dislodged from Mars by a huge impact about 16 million years ago and that fell to Earth in Antarctica 13,000 years ago. The meteorite was found in Allan Hills ice field, Antarctica, by an annual expedition of the National Science Foundation's Antarctic Meteorite Program in 1984. It is preserved for study at the Johnson Space Center's Meteorite Processing Laboratory in Houston.

  13. Geochemical evidence for mixing of three components in martian orthopyroxenite ALH 84001. [Abstract only

    NASA Technical Reports Server (NTRS)

    Mittlefehldt, D. W.; Lindstrom, M. M.

    1994-01-01

    ALH 84001, a ferroan martian orthopyroxenite, originally consisted of three petrographically defined components: a cumulus assemblage of orthopyroxene + chromite, a trapped melt assemblage of orthopyroxene(?) + chromite + maskelynite + apatite + augite +/- pyrite, and a metasomatic assemblage of carbonate +/- pyrite. We present the results of Instrumental Neutron Activation Analysis (INAA) study of five bulk samples of ALH 84001, combined with Scanning Ion Mass Spectrometer (SIMS) data on the orthopyroxene, in order to attempt to set limits on the geochemical characteristics of the latter two components, and therefore on the petrogenesis of ALH 84001. The INAA data support the petrographic observations, suggesting that there are at least three components in ALH 84001. We will assume that each of the three geochemically required components can be equated with one of the petrographically observed components. Both trapped melt and metasomatic components in ALH 84001 have higher Na than orthopyroxene based on compositions of maskelynite, apatite, and carbonate. For the metasomatic component, we will assume its Na content is that of carbonate, while for a trapped melt component, we will use a typical Na content inferred for martian meteorite parent melts, approximately 1 wt% Na2O. Under these assumptions, we can set limits on the Light Rare Earth Elements/Heavy Rare Earth Elements (LREE/HREE) ratios of the components, and use this information to compare the petrogenesis of ALH 84001 with other martian meteorites. The above calculations assume that the bulk samples are representative of different portions of ALH 84001. We will also evaluate the possible heterogeneous distribution of mineral phases in the bulk samples as the cause of compositional heterogeneity in our samples.

  14. A search for endogenous amino acids in martian meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Bada, J. L.; Glavin, D. P.; McDonald, G. D.; Becker, L.

    1998-01-01

    Trace amounts of glycine, serine, and alanine were detected in the carbonate component of the martian meteorite ALH84001 by high-performance liquid chromatography. The detected amino acids were not uniformly distributed in the carbonate component and ranged in concentration from 0.1 to 7 parts per million. Although the detected alanine consists primarily of the L enantiomer, low concentrations (<0.1 parts per million) of endogenous D-alanine may be present in the ALH84001 carbonates. The amino acids present in this sample of ALH84001 appear to be terrestrial in origin and similar to those in Allan Hills ice, although the possibility cannot be ruled out that minute amounts of some amino acids such as D-alanine are preserved in the meteorite.

  15. A search for endogenous amino acids in martian meteorite ALH84001.

    PubMed

    Bada, J L; Glavin, D P; McDonald, G D; Becker, L

    1998-01-16

    Trace amounts of glycine, serine, and alanine were detected in the carbonate component of the martian meteorite ALH84001 by high-performance liquid chromatography. The detected amino acids were not uniformly distributed in the carbonate component and ranged in concentration from 0.1 to 7 parts per million. Although the detected alanine consists primarily of the L enantiomer, low concentrations (<0.1 parts per million) of endogenous D-alanine may be present in the ALH84001 carbonates. The amino acids present in this sample of ALH84001 appear to be terrestrial in origin and similar to those in Allan Hills ice, although the possibility cannot be ruled out that minute amounts of some amino acids such as D-alanine are preserved in the meteorite. PMID:9430583

  16. Mars Life? - Orange-colored Carbonate Mineral Globules

    NASA Technical Reports Server (NTRS)

    1996-01-01

    This photograph shows orange-colored carbonate mineral globules found in a meteorite, called ALH84001, believed to have once been a part of Mars. These carbonate minerals in the meteorite are believed to have been formed on Mars more than 3.6 billion years ago. Their structure and chemistry suggest that they may have been formed with the assistance of primitive, bacteria-like living organisms. A two-year investigation by a NASA research team found organic molecules, mineral features characteristic of biological activity and possible microscopic fossils inside of carbonate minerals such as these in the meteorite.

  17. The origin of organic matter in the Martian meteorite ALH84001.

    PubMed

    Becker, L; Popp, B; Rust, T; Bada, J L

    1999-03-30

    Stable carbon isotope measurements of the organic matter associated with the carbonate globules and the bulk matrix material in the ALH84001 Martian meteorite indicate that two distinct sources are present in the sample. The delta 13C values for the organic matter associated with the carbonate globules averaged -26% and is attributed to terrestrial contamination. In contrast, the delta 13C values for the organic matter associated with the bulk matrix material yielded a value of -15%. The only common sources of carbon on the Earth that yield similar delta 13C values, other then some diagenetically altered marine carbonates, are C4 plants. A delta 13C value of -15%, on the other hand, is consistent with a kerogen-like component, the most ubiquitous form of organic matter found in carbonaceous chondrites such as the Murchison meteorite. Examination of the carbonate globules and bulk matrix material using laser desorption mass spectrometry (LDMS) indicates the presence of a high molecular weight organic component which appears to be extraterrestrial in origin, possibly derived from the exogenous delivery, of meteoritic or cometary debris to the surface of Mars. PMID:11542930

  18. The origin of organic matter in the Martian meteorite ALH84001.

    PubMed

    Becker, L; Popp, B; Rust, T; Bada, J L

    1999-01-01

    Stable carbon isotope measurements of the organic matter associated with the carbonate globules and the bulk matrix material in the ALH84001 Martian meteorite indicate that two distinct sources are present in the sample. The delta 13C values for the organic matter associated with the carbonate globules averaged -26% and is attributed to terrestrial contamination. In contrast, the delta 13C values for the organic matter associated with the bulk matrix material yielded a value of -15%. The only common carbon sources on the Earth that yield similar delta 13C values, other then some diagenetically altered marine carbonates, are C4 plants. A delta 13C value of -15%, on the other hand, is consistent with a kerogen-like component, the most ubiquitous form of organic matter found in carbonaceous chondrites such as the Murchison meteorite. Examination of the carbonate globules and bulk matrix material using laser desorption mass spectrometry (LDMS) indicates the presence of a high molecular weight organic component which appears to be extraterrestrial in origin, possibly derived from the exogenous delivery of meteoritic or cometary debris to the surface of Mars. PMID:11543335

  19. A Non-Biological Origin for the Nanophase Magnetite Grains in ALH84001: Experimental Results

    NASA Technical Reports Server (NTRS)

    Koziol, Andrea M.; Brearley, Adrian J.

    2002-01-01

    We subjected siderite-magnesite carbonates to a short-lived thermal pulse. Individual magnetite grains that formed are 10 to 20 nm in size and randomly oriented. Shape and size distribution of these grains appear similar to those seen in ALH84001. Additional information is contained in the original extended abstract.

  20. Structural and morphological anomalies in magnetosomes: possible biogenic origin for magnetite in ALH84001.

    PubMed

    Taylor, A P; Barry, J C; Webb, R I

    2001-01-01

    We report biogenic magnetite whiskers, with axial ratios of 6 : 1, elongated in the [1 1 1], [1 1 2] and [1 0 0] directions, resembling the magnetite whiskers detected in the Martian meteorite ALH84001 by Bradley et al., and interpreted by those authors as evidence of vapour-phase (abiogenic) growth. Magnetosomal whiskers with extended defects consistent with screw dislocations and magnetosomes resembling flattened twinned platelets, as well as other twinning phenomena and other structural defects, are also reported here. Magnetosomes with teardrop-shaped, cuboidal, irregular and jagged structures similar to those detected in ALH84001 by McKay et al., coprecipitation of magnetite possibly with amorphous calcium carbonate, coprecipitation of magnetite possibly with amorphous silica, the incorporation of titanium in volutin inclusions and disoriented arrays of magnetosomes are also described. These observations demonstrate that the structures of the magnetite particles in ALH84001, their spatial arrangement and coprecipitation with carbonates and proximity to silicates are consistent with being biogenic. Electron-beam-induced flash-melting of magnetosomes produced numerous screw dislocations in the [1 1 1], [1 0 0], and [1 1 0] lattice planes and induced fusion of platelets. From this, the lack of screw dislocations reported in the magnetite particles in ALH84001 (McKay et al., and Bradley et al.) indicates that they have a low-temperature origin. PMID:11136443

  1. ALH84001, a cumulate orthopyroxenite member of the Martian meteorite clan

    NASA Technical Reports Server (NTRS)

    Mittlefehldt, David W.

    1994-01-01

    ALH84001, originally classified as a diogenite, is a coarse-grained, cataclastic, orthopyroxenite meteorite related to the martian (SNC) meteorites. The orthopyroxene is relatively uniform in composition, with a mean composition of Wo3.3En69.4Fs27.3. Minor phases are euhedral to subhedral chromite and interstitial maskelynite, An31.1Ab63.2Or5.7, with accessory augite, Wo42.2En45.1Fs12.7, apatite, pyrite and carbonates, Cc11.5Mg58.0Sd29.4Rd1.1. The pyroxenes and chromites in ALH84001 are similar in composition to these phases in EETA79001 lithology a megacrysts but are more homogeneous. Maskelynite is similar in composition to feldspars in the nakhlites and Chassigny. Two generations of carbonates are present, early (pre-shock) strongly zoned carbonates and late (post-shock) carbonates. The high Ca content of both types of carbonates indicates that they were formed at moderately high temperature, possibly approximately 700 C. ALH84001 has a slightly LREE-depleted pattern with La 0.67x and Lu 1.85x CI abundances and with a negative Eu anomaly (Eu/Sm 0.56x CI). The uniform pyroxene composition is unusual for martian meteorites, and suggests that ALH84001 cooled more slowly than did the shergottites, nakhlites of Chassigny. The nearly monomineralic composition, coarse-grain size, homogeneous orthopyroxene and chromite compositions, the interstitial maskelynite and apatite, and the REE pattern suggest that ALH84001 is a cumulate orthopyroxenite containing minor trapped, intercumulus material.

  2. Isotope Geochemistry of Possible Terrestrial Analogue for Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Mojzsis, Stephen J.

    2000-01-01

    We have studied the microdomain oxygen and carbon isotopic compositions by SIMS of complex carbonate rosettes from spinel therzolite xenoliths, hosted by nepheline basanite, from the island of Spitsbergen (Norway). The Quaternary volcanic rocks containing the xenoliths erupted into a high Arctic environment and through relatively thick continental crust containing carbonate rocks. We have attempted to constrain the sources of the carbonates in these rocks by combined O-18/O-16 and C-13/C-12 ratio measurements in 25 micron diameter spots of the carbonate and compare them to previous work based primarily on trace-element distributions. The origin of these carbonates can be interpreted in terms of either contamination by carbonate country rock during ascent of the xenoliths in the host basalt, or more probably by hydrothermal processes after emplacement. The isotopic composition of these carbonates from a combined delta.18O(sub SMOW) and delta.13C(sub PDB) standpoint precludes a primary origin of these minerals from the mantle. Here a description is given of the analysis procedure, standardization of the carbonates, major element compositions of the carbonates measured by electron microprobe, and their correlated C and O isotope compositions as measured by ion microprobe. Since these carbonate rosettes may represent a terrestrial analogue to the carbonate "globules" found in the martian meteorite ALH84001 interpretations for the origin of the features found in the Spitsbergen may be of interest in constraining the origin of these carbonate minerals on Mars.

  3. Magnetite-Magnesioferrite Phase Relations and Application to ALH84001

    NASA Technical Reports Server (NTRS)

    Koziol, Andrea M.

    2003-01-01

    Oxygen fugacity (fO2) is an important factor in planetary formation and evolution. Certain minerals or assemblages of minerals are stable only under certain fO2 conditions (at a constant T and P) and can be recorders of ambient fO2 during geologic processes. The best estimate of oxygen fugacity from mineral assemblages has implications, from large-scale models of planetary evolution to interpretation of single meteorites. For example, redox conditions are part of the discussion of the origin and history of shergottites, basaltic rocks in meteorites from Mars [1-4]. In addition oxygen fugacity may be an important factor to consider in the interpretation of the carbonate and magnetite assemblages seen in ALH84001 [5].

  4. Experimental Shock Decomposition of Siderite and the Origin of Magnetite in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Bell, Mary Sue

    2007-01-01

    Shock recovery experiments to determine whether magnetite could be produced by the decomposition of iron-carbonate were initiated. Naturally occurring siderite was first characterized by electron microprobe (EMP), transmission electron microscopy (TEM), Mossbauer spectroscopy, and magnetic susceptibility measurements to be sure that the starting material did not contain detectable magnetite. Samples were shocked in tungsten-alloy holders (W=90%, Ni=6%, Cu=4%) to further insure that any iron phases in the shock products were contributed by the siderite rather than the sample holder. Each sample was shocked to a specific pressure between 30 to 49 GPa. Previously reported results of TEM analyses on 49 GPa experiments indicated the presence of nano-phase spinel-structured iron oxide. Transformation of siderite to magnetite as characterized by TEM was found in the 49 GPa shock experiment. Compositions of most magnetites are greater than 50% Fe sup(+2) in the octahedral site of the inverse spinel structure. Magnetites produced in shock experiments display the same range of single-domain, superparamagnetic sizes (approx. 50 100 nm), compositions (100% magnetite to 80% magnetite-20% magnesioferrite), and morphologies (equant, elongated, euhedral to subhedral) as magnetites synthesized by Golden et al. (2001) or magnetites grown naturally by MV1 magnetotactic bacteria, and as the magnetites in Martian meteorite ALH84001. Fritz et al. (2005) previously concluded that ALH84001 experienced approx. 32 GPa pressure and a resultant thermal pulse of approx. 100 - 110 C. However, ALH84001 contains evidence of local temperature excursions high enough to 1 melt feldspar, pyroxene, and a silica-rich phase. This 49 GPa experiment demonstrates that magnetite can be produced by the shock decomposition of siderite as a result of local heating to greater than 470 C. Therefore, magnetite in the rims of carbonates in Martian meteorite ALH84001 could be a product of shock devolatilization of

  5. Metamorphic Origin of Sub-Micron Magnetite Crystals in ALH 84001: Re-Evaluation of Equilibria, Thermochemistry, and Experiments

    NASA Astrophysics Data System (ADS)

    Treiman, A. H.; Essene, E. J.

    2010-04-01

    Treiman (1993) suggested that magnetite grains in ALH 84001 formed by decomposition of Fe-carbonate after a major impact event. Criticisms of this work (Thomas-Keprta et al.. 2009) lack merit, and demonstrate some pitfalls in the search for signs of extraterrestrial life.

  6. Metamorphic Origin of Sub-Micron Magnetite Crystals in ALH 84001: Reevaluation of Equilibria, Thermochemistry, and Experiments

    NASA Astrophysics Data System (ADS)

    Treiman, A. H.; Essene, E. J.

    2010-03-01

    Magnetite grains in ALH 84001, cited as evidence of martian life, could have formed abiotically by thermal decomposition of Fe-rich carbonates. Thomas-Keprta et al. (2009) criticize this abiotic hypothesis; their criticisms lack merit and do not disprove the hypothesis.

  7. High Resolution Chemical Study of ALH84001

    NASA Technical Reports Server (NTRS)

    Conrad, Pamela G.; Douglas, Susanne; Kuhlman, Kimberly R.

    2001-01-01

    We have studied the chemistry of a sample of the SNC meteorite ALH84001 using an environmental scanning electron microscope (ESEM) with an energy dispersive chemical analytical detector and a focused ion beam secondary ion mass spectrometer (FIB-SIMS). Here we present the chemical data, both spectra and images, from two techniques that do not require sample preparation with a conductive coating, thus eliminating the possibility of preparation-induced textural artifacts. The FIB-SIMS instrument includes a column optimized for SEM with a quadrupole type mass spectrometer. Its spatial and spectral resolution are 20 nm and 0.4 AMU, respectively. The spatial resolution of the ESEM for chemical analysis is about 100 nm. Limits of detection for both instruments are mass dependent. Both the ESEM and the FIB-SIMS instrument revealed contrasting surficial features; crumbled, weathered appearance of the matrix in some regions as well as a rather ubiquitous presence of euhedral halite crystals, often associated with cracks or holes in the surface of the rock. Other halogen elements present in the vicinity of the NaCl crystals include K and Br. In this report, elemental inventories are shown as mass spectra and as X-ray maps.

  8. Magnetofossils in Terrestrial Samples and Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    ThomasKeptra, Kathie L.; Clemett, Simon J.; Bazylinski, Dennis A.; Kirschvink, Joseph L.

    2001-01-01

    Here we compare magnetite crystals produced by terrestrial magnetotactic bacteria strain MV-1 with a subpopulation of magnetites from ALH84001. We find both to be chemically and physically identical-specifically, both are single-domain, chemically pure, and exhibit an unusual crystal habit we describe as truncated hexa-octahedral. On Earth such truncated hexa-octahedral magnetites are only known to be produced by magnetotactic bacteria. We suggest that the observation of truncated hexa-octahedral magnetites in ALH84001 are both consistent with, and in the absence of terrestrial inorganic analogs, likely formed by biogenic processes. Additional information is contained in the original extended abstract.

  9. A mild, near-surface aqueous environment on Noachian Mars preserved in ALH84001

    NASA Astrophysics Data System (ADS)

    Halevy, I.; Fischer, W. W.; Eiler, J. M.

    2011-12-01

    Despite widespread evidence for liquid water at the surface of Mars during parts of the Noachian epoch, the temperature of early aqueous environments has been impossible to establish, raising questions of whether Mars' surface was ever warmer than today. This has hindered insight into aqueous alteration processes, which, on the basis of orbital spectroscopy, appear to have been prevalent on Noachian Mars. It is important to understand such processes, as they link the observed secondary mineral assemblages to interactions between primary igneous silicates and the surface environment (atmosphere-hydrosphere). We have addressed this problem by determining the precipitation temperatures of secondary carbonate minerals preserved in the oldest known sample of Mars' crust-the meteorite Allan Hills 84001 (ALH84001). Using carbonate 'clumped' isotope thermometry we have found that the carbonates in ALH84001, which are 3.9-4.0 billion years old, formed at a temperature of ~18±4°C. With temperature known, we used the carbon and oxygen isotopic composition of the carbonates, as constrained by both our measurements and previous acid digestion and ion microprobe studies, to develop a model for their formation process and environment. The observed isotopic variation is best explained by carbonate precipitation out of a gradually evaporating, shallow subsurface aqueous solution (e.g. a regolith aquifer) at near-constant temperatures. Furthermore, on the basis of the isotopic composition of the earliest precipitated carbonates in ALH84001, the volatiles from which they formed (H2O and CO2) came not from depth, but from the early Martian surface. The occurrence of carbonates in other SNC meteorites and as a minor component of Martian dust implies that environments analogous to the one we studied may have been important in generating some of the observed secondary mineral assemblages by interaction between Mars' igneous crust and its atmosphere-hydrosphere.

  10. Determination of the Three-Dimensional Morphology of ALH84001 and Biogenic MV-1 Magnetite: Comparison of Results from Electron Tomography and Classical Transmission Electron Microscopy

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Schwartz, Cindy; Morphew, Mary; McIntosh, J. Richard; Bazylinski, Dennis A.; Kirschvink, Joseph L.; Wentworth, Susan J.; McKay, David S.; Vali, Hojatollah

    2004-01-01

    Dated at approximately 3.9 billion years of age, carbonate disks, found within fractures of the host rock of Martian meteorite ALH84001, have been interpreted as secondary minerals that formed at low temperature in an aqueous medium. Heterogeneously distributed within these disks are magnetite nanocrystals that are of Martian origin. Approximately one quarter of these magnetites have morphological and chemical similarities to magnetite particles produced by magnetotactic bacteria strain MV-1, which are ubiquitous in aquatic habitats on Earth. Moreover, these types of magnetite particles are not known or expected to be produced by abiotic means either through geological processes or synthetically in the laboratory. The remaining three quarters of the ALH84001 magnetites are likely products of multiple processes including, but not limited to, precipitation from a hydrothermal fluid, thermal decomposition of the carbonate matrix in which they are embedded, and extracellular formation by dissimilatory Fe-reducing bacteria. We have proposed that the origins of magnetites in ALH84001 can be best explained as the products of multiple processes, one of which is biological. Recently the three-dimensional (3-D) external morphology of the purported biogenic fraction of the ALH84001 magnetites has been the subject of considerable debate. We report here the 3-D geometry of biogenic magnetite crystals extracted from MV-1 and of those extracted from ALH84001 carbonate disks using a combination of high resolution classical and tomographic transmission electron microscopy (TEM). We focus on answering the following questions: (1) which technique provides adequate information to deduce the 3-D external crystal morphology?; and, (2) what is the precise 3-D geometry of the ALH84001 and MV-1 magnetites?

  11. Origins of magnetite nanocrystals in Martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Thomas-Keprta, K. L.; Clemett, S. J.; McKay, D. S.; Gibson, E. K.; Wentworth, S. J.

    2009-11-01

    The Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks. These carbonate disks are believed to have precipitated 3.9 Ga ago at beginning of the Noachian epoch on Mars during which both the oldest extant Martian surfaces were formed, and perhaps the earliest global oceans. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe 3O 4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of magnetite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. For example, the magnetites might have already been present in the aqueous fluids from which the carbonates were believed to have been deposited. We have sought to resolve between these hypotheses through the detailed characterization of the compositional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded. Extensive use of focused ion beam milling techniques has been utilized for sample preparation. We then compared our observations with those from experimental thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios. We conclude that the vast majority of the nanocrystal magnetites present in the carbonate disks could not have formed by any of the currently proposed thermal decomposition scenarios. Instead, we find there is considerable evidence in support of an alternative allochthonous origin for the magnetite unrelated to any shock or thermal processing of the carbonates.

  12. Origins of Magnetite Nanocrystals in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Mckay, David S.; Gibson, Everett K.; Wentworth, Susan J.

    2009-01-01

    The Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks. These carbonate disks are believed to have precipitated 3.9 Ga ago at beginning of the Noachian epoch on Mars during which both the oldest extant Martian surfaces were formed, and perhaps the earliest global oceans. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of mag- netite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. For example, the magnetites might have already been present in the aqueous fluids from which the carbonates were believed to have been deposited. We have sought to resolve between these hypotheses through the detailed characterized of the compo- sitional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded. Extensive use of focused ion beam milling techniques has been utilized for sample preparation. We then compared our observations with those from experimental thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios. We conclude that the vast majority of the nanocrystal magnetites present in the car- bonate disks could not have formed by any of the currently proposed thermal decomposition scenarios. Instead, we find there is considerable evidence in support of an alternative allochthonous origin for the magnetite unrelated to any shock or thermal processing of the carbonates.

  13. Did an Impact Make the Mysterious Microscopic Magnetite Crystals in ALH 84001?

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    2007-10-01

    Fervent debate swirls around microscopic crystals of magnetite (Fe3O4) in Martian meteorite ALH 84001. Some investigators suggest that the crystals are evidence of past life on Mars, citing magnetite crystals of similar chemical compositions and sizes made by magnetotactic bacteria on Earth. Others cite assorted experiments and observations to argue that the important little crystals formed entirely by non-biological processes, hence say nothing about life on Mars. One of those processes is the decomposition of iron carbonate (the mineral siderite), which occurs in ALH 84001. Researchers argue that heating this mineral causes it to decompose into magnetite and CO2 gas. Experiments showing this were done by heating siderite and observing that it decomposed and formed magnetite, but nobody had shock-heated siderite to see if magnetite crystals formed. (Shock is a rapid, strong rise and fall in pressure. It happens under many circumstances, including meteorite impacts.) The lack of shock experiments has been solved by Mary Sue Bell (University of Houston and Jacobs Engineering). She experimentally shocked samples of siderite at the Experimental Impact Laboratory at the Johnson Space Center. She shows that magnetite crystals of the right size and composition formed when samples were shocked to 49 GPa (about 500,000 times the pressure at the Earth's surface). This is more evidence for a non-biological origin for the magnetite crystals in ALH 84001 and is consistent with what we know about the impact history of the rock. There seems to be growing evidence against a biological origin, but don't expect these results to completely settle the debate!

  14. Polycyclic Aromatic Hydrocarbons in the Martian (SNC) Meteorite ALH 84001: Hydrocarbons from Mars, Terrestrial Contaminants, or Both?

    NASA Astrophysics Data System (ADS)

    Thomas, K. L.; Clemett, S. J.; Romanek, C. S.; Macheling, C. R.; Gibson, E. K.; McKay, D. S.; Score, R.; Zare, R. N.

    1995-09-01

    Previous work has shown that pre-terrestrial polycyclic aromatic hydrocarbons (PAHs) exist in interplanetary dust particles (IDPs) and certain meteorites [1-3]. We previously reported the first observation of PAHs in the newest member of the SNC group, Allan Hills 84001 [4] and determined that particular types of organic compounds are indigenous to ALH 84001 because they are associated with certain mineralogical features [4]. We also analyzed two diogenites from Antarctica: one showed no evidence for aromatic hydrocarbons while the other contained PAHs with the same major peaks as those in ALH 84001[4]. PAHs in the diogenite meteorite are not associated with mineral features on the analyzed surface and the most abundant PAHs in the diogenite are lower by a factor of 3 than those in ALH 84001. Furthermore, ALH 84001 contains a number of minor PAHs not found in the diogenite or typical terrestrial soils [4]. In this study we are analyzing a more complete group of Antarctic and non-Antarctic meteorites, including SNCs, to determine: (1) PAHs abundance and diversity in Antarctic meteorites and (2) the contribution of PAHs in SNCs from martian and, possibly, terrestrial sources. ALH 84001 is an unusual orthopyroxenite which contains abundant carbonate spheroids which are ~100-200 micrometers in diameter and range in composition from magnesite to ferroan magnesite [5-7]. These spheroids are not the result of terrestrial contamination: oxygen isotopic compositions indicate that the carbonates probably precipitated from a low-temperature fluid within the martian crust [5] and carbon isotopic abundances are consistent with martian atmospheric CO2 as the carbon source [5]. PAHs may coexist with other low-temperature carbon-bearing phases in a subsurface martian environment. Samples: We are analyzing freshly-fractured meteorite samples, or chips, which have been extracted from the internal regions of the following meteorites: ALH 84001 (crush and uncrush zones), EETA79001

  15. Record of fluid-rock interactions on Mars from the meteorite ALH84001.

    PubMed

    Romanek, C S; Grady, M M; Wright, I P; Mittlefehldt, D W; Socki, R A; Pillinger, C T; Gibson, E K

    1994-12-15

    Allan Hills (ALH) 84001 is the most recently recognized member of a suite of meteorites--the SNCs--that almost certainly originated on Mars. Several factors distinguish ALH84001 from the other SNC meteorites. Preliminary studies suggest that it may be older than other martian meteorites. Moreover, it contains abundant, zoned domains of calcium-iron-magnesium carbonate that are indigenous to the sample and thus may hold important clues regarding near-surface processes on Mars and the evolution of the martian atmosphere. We report here analyses of the carbon and oxygen stable-isotope compositions of the carbonates that place constraints on their formation conditions. Our results imply the presence of at least two chemically distinct carbonates--one Ca,Fe-rich, the other Mg-rich--that are enriched in 13C relative to terrestrial carbonates (delta 13C approximately +41/1000), consistent with martian atmospheric CO2 as the carbon source. The oxygen isotope compositions of the carbonates indicate that they precipitated from a low-temperature fluid in the martian crust. Combined with textural and bulk geochemical considerations, the isotope data suggest that carbonate deposition took place in an open-system environment in which the ambient temperature fluctuated. PMID:7990956

  16. Formation of "Chemically Pure" Magnetite from Mg-Fe-Carbontes: Implications for Exclusively Inorganic Origin of Magnetite and Sulfides in Martian Meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Golden, D. C.; Ming, D. W.; Lauer, H. V., Jr.; Morris, R. V.; Treiman, A. H.; McKay, G. A.

    2006-03-01

    Pure (Mg-free) magnetite was synthesized by heating Mg-Fe-carbonate at 350°C in the presence of pyrite in an evacuated sealed glass tube. The Mg-free magnetite in the black rims of ALH84001 may have formed by a similar inorganic abiotic process from Mg-Fe-carbonates.

  17. Spectroscopic properties of Martian meteorite ALH84001 and identification of minerals and organic species

    NASA Astrophysics Data System (ADS)

    Bishop, J. L.; Pieters, C. M.; Hiroi, T.

    1997-03-01

    Chemical and mineralogical analyses of the Martian meteorite ALH84001 have shown that it contains primarily orthopyroxene, which differentiates it from other Martian meteorites. Detailed spectroscopic analyses of multiple chip surfaces and a particulate sample of ALH84001 are presented here. The IR spectra of the chip and powder samples exhibit features characteristic of several minerals. The 5-25-micron spectra of ALH84001 are especially difficult to interpret because of multiple mineral components and particle size variations.

  18. Determination of the Three-Dimensional Morphology of ALH84001 and Biogenic MV-1 Magnetite: Comparison of Results from Electron Tomography and Classical Transmission Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Thomas-Keprta, K. L.; Clemett, S. J.; Schwartz, C.; Morphew, M.; McIntosh, J. R.; Bazylinski, D. A.; Kirschvink, J. L.; Wentworth, S. J.; McKay, D. S.; Vali, H.; Gibson, E. K., Jr.; Romanek, C. S.

    2004-03-01

    Up to ~25% of magnetites embedded in ALH84001 carbonate disks have morphological and chemical similarities to biogenic MV-1 magnetites. We have proposed that these Martian magnetites can be best explained as the diverse products of biogenic and inorganic processes that operated on early Mars.

  19. Search for Unique Organic Biomarkers in ALH84001

    NASA Technical Reports Server (NTRS)

    Zare, Richard N.

    1999-01-01

    Four goals were outlined for this project. These were: [1] to reproduce the measurement of polycyclic aromatic hydrocarbons (PAHS) in ALH84001 with both a higher spatial resolution and sensitivity than has been previously reported; [2] to extend such measurements to include other members of the Martian SNC (Shergotties, Nahklites, and Chassigny) meteorite clan, in particular the Antarctic Martian meteorite EETA79001; [3] to address issues of potential organic contamination, because at present very little is known about the effect of terrestrial weathering in the Antarctic environment as it pertains to perturbing an indigenous organic distribution within a meteoritic matrix; and [4] to diversify the range of organic compounds studied to include species that can serve as unique biological markers - "molecular fossils" - derived from once living organisms. In order to achieve this, three specific goals were outlined for the funding period 06/01/97 to 02/28/98. They were: [1] to investigate the effects of terrestrial weathering and organic contamination of meteoritic samples collected from Antarctica; [2] to reproduce and extend upon the measurements of PAHs in ALH84001 with the aim of establishing or refuting the indigeneity of these species; and [3] to extend the analysis of organic compounds in ALH84001 and EETA79001 to address compounds that are considered to be more biologically relevant than PAHS. All three were successfully accomplished, as detailed in the previous performance report. In brief, however, the results achieved were to establish that the PAHs found in ALH84001 were indigenous and not due to contamination, and to determine that a novel and sensitive technique in meteoritic work, capillary zone electrophoresis (CE), could indeed detect amino acids, a potential class of biomarker.

  20. Magnetite whiskers and platelets in the ALH84001 Martian meteorite: evidence of vapor phase growth.

    PubMed

    Bradley, J P; Harvey, R P; McSween, H Y

    1996-01-01

    Nanometer-sized magnetite crystals associated with carbonates in fracture zones within Martian meteorite ALH84001 have been examined using analytical transmission electron microscopy. Some of the crystals exhibit distinctive morphologies: filamentary rods and ribbon, and platelets. The rods and ribbons are elongated along the crystallographic [100] and [111] directions. Some of the rods contain microstructural defects indicating that they grew by spiral growth about screw dislocations. Platelets are flattened along the [100] and [110] directions. These unique morphologies and microstructures constrain the growth conditions of magnetite. The whiskers and platelets most likely formed in the temperature range 500-800 degrees C by direct condensation from a vapor or precipitation from a supercritical fluid, and their properties are inconsistent with a biogenic origin. PMID:11541129

  1. LU-HF Age and Isotope Systematics of ALH84001

    NASA Technical Reports Server (NTRS)

    Righter, M.; Lapen, T. J.; Brandon, A. D.; Beard, B. L.; Shafer, J. T.; Peslier, A. H.

    2009-01-01

    Allan Hills (ALH) 84001 is an orthopyroxenite that is unique among the Martian meteorites in having the oldest inferred crystallization age (approx..4.5 to 4.0 Gyr) [e.g., 1-6 and references therein 7]. Its ancient origin makes this stone a critical constraint on early history of Mars, in particular the evolution of different planetary crust and mantle reservoirs. However, because there is significant variability in reported crystallization ages, determination of initial isotope compositions is imprecise making assessment of planetary reservoirs difficult. Here we report a new Lu-Hf mineral isochron age, initial Hf-176/Hf-177 isotope composition, and inferred Martian mantle source compositions for ALH84001 that place constraints on longlived source reservoirs for the enriched shergottite suite of Martian meteorites including Shergotty, Zagami, NWA4468, NWA856, RBT04262, LAR06319, and Los Angeles. Sm-Nd isotope analyses are under way for the same mineral aliquots analyzed for Lu-Hf. The Lu-Hf system was utilized because Lu and Hf are both lithophile and refractory and are not easily redistributed during short-lived thermal pulses associated with shock metamorphism. Moreover, chromite has relatively modest Hf concentrations with very low Lu/Hf ratios [9] yielding tight constraints on initial Hf-176/Hf-177 isotope compositions

  2. Truncated Hexa-Octahedral Magnetites: Biosignatures in Terrestrial Samples and Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Bazylinski, Dennis A.; Kirschvink, Joseph L.; McKay, David S.; Wentworth, Susan J.; Vali, H.; Gibson, Everett K.

    2001-01-01

    We suggest that the observation of truncated hexa-octahedral magnetites in ALH84001 are both consistent with, and in the absence of terrestrial inorganic analogs, likely formed by biogenic processes. Additional information is contained in the original extended abstract.

  3. Evidence for the extraterrestrial origin of polycyclic aromatic hydrocarbons in the Martian meteorite ALH84001.

    PubMed

    Clemett, S J; Dulay, M T; Gillette, J S; Chillier, X D; Mahajan, T B; Zare, R N

    1998-01-01

    Possible sources of terrestrial contamination are considered for the observation of polycyclic aromatic hydrocarbons (PAHs) in the Martian meteorite ALH84001. Contamination is concluded to be negligible. PMID:9809015

  4. Geochemistry of the Martian meteorite ALH84001, revisited

    NASA Astrophysics Data System (ADS)

    Barrat, Jean-Alix; Bollinger, Claire

    2010-04-01

    Major and trace element abundances were determined on powders prepared from four distinct chips from Allan Hills (ALH) 84001 to constrain the bulk rock composition, and to assess the trace element abundances of orthopyroxenes and phosphates. Our new determinations were used to evaluate the composition of the parental melt of this stone. An unrealistic light rare earth element (REE)-enriched parental melt is calculated from the composition of the orthopyroxene and relevant equilibrium partition coefficients. The involvement of a small amount of trapped melt and subsolidus reequilibrations between orthopyroxene and the interstitial phases can account for this discrepancy. A parental melt that displays a trace element pattern (REE, Zr, and Hf) that closely resembles enriched shergottites such as Zagami or Los Angeles is calculated if these effects are taken into account. These results suggest that some shergottitic melts were already erupted on Mars during the Noachian.

  5. Pre-4.0 billion year weathering on Mars constrained by Rb-Sr geochronology on meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Beard, Brian L.; Ludois, James M.; Lapen, Thomas J.; Johnson, Clark M.

    2013-01-01

    The timing and nature of aqueous alteration of meteorite ALH84001 has important implications for the history of water on early Mars, the evolution of the Martian atmosphere, and the potential for early Mars habitability. Rubidium-Sr isotope analyses of mineral separates from igneous-textured and carbonate-rich aliquots of Martian meteorite ALH84001 constrain the age of alteration and the source of fluids. The carbonate-rich aliquot defines a precise Rb-Sr isochron between maskelynite, orthopyroxene, and chromite of 3952±22 Ma, and this is interpreted to represent a shock resetting event that was broadly coeval with carbonate precipitation. Carbonate, bulk rock, and multi-mineral separates all have high 87Sr/86Sr ratios that can only have been produced by alteration via a fluid derived through interaction with high Rb/Sr phyllosilicates that were produced prior to 3950 Ma. These data confirm that the source of Sr in the fluids was previously altered crustal rock, consistent with fluids that underwent low-temperature water-rock interaction (Eiler et al., 2002; Halvey et al., 2011). These results therefore provide evidence for wet, clay-rich conditions on the surface of Mars prior to ˜4.2 Ga.

  6. Spectroscopic analysis of Martian meteorite ALH 84001 powder and applications for spectral identification of minerals and other soil components on Mars

    NASA Astrophysics Data System (ADS)

    Bishop, Janice L.; Pieters, Carle M.; Hiroi, Takahiro; Mustard, John F.

    1998-07-01

    Spectroscopic measurement and analysis of Martian meteorites provide important information about the mineralogy of Mars, as well as necessary ground-truths for deconvolving remote sensing spectra of the Martian surface rocks. The spectroscopic properties of particulate ALH 84001 from 0.3 to 25 (m correctly identify low-Ca-pyroxene as the dominant mineralogy. Absorption bands due to electronic transitions of ferrous iron are observed at 0.94 and 1.97 (m that are typical for low-Ca-pyroxene. A strong, broad water band is observed near 3 (m that is characteristic of the water band typically associated with pyroxenes. Weaker features near 4.8, 5.2 and 6.2 (m are characteristic of particulate low-Ca-pyroxene, and can be readily distinguished from the features due to high-Ca-pyroxene and other silicate minerals. The reflectance minimum occurs near 8.6 (m for the ALH 84001 powder, which is more consistent with high-Ca-pyroxene and augite than low-Ca-pyroxene. The dominant mid-IR spectral features for the ALH 84001 powder are observed near 9 and 19.5 (m; however, there are multiple features in this region. These mid-IR features are generally characteristic of low-Ca-pyroxene, but cannot be explained by low-Ca-pyroxene alone. Spectral features from 2.5-5 (m are typically associated with water, organics and carbonates and have been studied in spectra of the ALH 84001, split 92 powder and ALH 84001, splits 92 and 271 chip surfaces. Weak features have been identified near 3.5 and 4 (m that are assigned to organic material and carbonates. Another feature is observed at 4.27 (m in many surface spots and in the powder, but has not yet been uniquely identified. Spectroscopic identification of minor organic and carbonate components in this probable piece of Mars suggests that detection of small amounts of organics and carbonates in the Martian surface regolith would also be possible using visible-infrared hyperspectral analyses. Laboratory spectroscopic analysis of Martian

  7. Hydrogeological Interpretation of Candidate Origin Sites for Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Gulick, Virginia C.; McKay, Chris; Cuzzi, Jeffrey N. (Technical Monitor)

    1996-01-01

    Barlow (this meeting) has identified two potential source craters for the martian meteorite ALH84001. The craters are at 11.7 deg S, 243.3 deg W (Mare Tyrrhenum site) and 14.0 deg S, 343.5 deg W (Sinus Sabaeus site). As noted by Barlow, both craters lie in the heavily cratered terrain (HCT) and are adjacent to fluvial valleys, Here I explore the fluvial history of these areas based upon the surrounding valley morphology. The most prominent valley network at the Sabaeus site is Evros Vallis. This wide, flat-floored valley is approximately 600 km long with an average width of 2.5 km and a depth of 220 m. The eroded volume of the entire Evros network is approximately 6 x 10(exp 11) cc. This is typical for networks located in the heavily cratered terrain (e.g. Warrego and Parana Valles). Evros is also an isolated valley system. No similar networks are found in the surrounding terrain. Thus it is unlikely that Evros formed as a result of widespread rainfall. A localized water source, such as discharge of a hydrothermal system or localized melting of snowfall, seems more consistent Previous modeling has demonstrated that only hydrothermal systems associated with high permeability subsurfaces can discharge sufficient water to form a valley network. The bulk of the discharge from such systems is consequently low temperature, slightly heated water Precipitation of calcium carbonate by low temperature fluids is consistent with most interpretations of the geochemistry of ALH84001. Available imagery at the Tyrrhenum site is of lesser quality. While eroded units of the HCT are nearby, there are no comparable well developed valley networks at this site. Erosion is instead manifested predominantly as gullies on slopes. This style of erosion suggests that water was not present at this site for the length of time as at the more integrated Sabaeus site. The superposition of fluidized ejecta blankets suggests however that ground water or ground ice was still present at this locality

  8. High-temperature Mars-to-Earth transfer of meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Min, Kyoungwon; Reiners, Peter W.

    2007-08-01

    Martian meteorites provide crucial insights into Martian evolution and interplanetary mass transfer, including the potential for exogenesis. ALH84001 is the oldest Martian meteorite discovered so far, and has been used to derive important conclusions about Martian surface temperatures and very low-temperature Mars-to-Earth transfer. To better constrain the thermal evolution and shock metamorphic history of ALH84001, we applied (U-Th)/He thermochronometry to single grains of phosphate (merrillite) from ALH84001. The (U-Th)/He ages of individual phosphate grains in ALH84001 range from 60 Ma to 1.8 Ga, with a weighted mean of ~830 Ma. This broad age distribution reflects multiple diffusion domains, and requires a relatively high-temperature resetting event younger than ˜ 60 Ma. These new data are combined with the published whole-rock (maskelynite as a main Ar reservoir) 40Ar/ 39Ar age spectra which show 5-8% fractional loss of radiogenic 40Ar since 4.0 Ga. He diffusion in both terrestrial and extraterrestrial apatite has a significantly higher activation energy (138 ˜ 184 kJ/mol) than Ar diffusion in maskelynite (75 kJ/mol), leading to an important "kinetic crossover" in fractional loss contours for these systems. Taken together, the phosphate (U-Th)/He and whole-rock 40Ar/ 39Ar ages require both very low surface temperatures on Mars, and one or more short-lived, high-temperature, shock events after 4.0 Ga. We suggest that the last shock event occurred with ejection of ALH84001 from Mars, and reached a peak temperature of approximately 400 °C. These results undermine the proposed low-temperature ejection hypothesis for ALH84001, but support long-lived extremely cold Martian surface temperatures.

  9. Rock Magnetic and Ferromagnetic Resonance Tests of Biogenic Magnetite in ALH84001

    NASA Technical Reports Server (NTRS)

    Kirschvink, J. L.; Kim, S.; Weiss, B. P.; Shannon, D. M.; Kobayashi, A. K.

    2002-01-01

    Three separate rock magnetic and ferromagnetic resonance tests support the hypothesis that between 25 and 50% of the fine-grained magnetite in the Martian meteorite ALH84001 was formed via biological processes. Additional information is contained in the original extended abstract.

  10. Low-Temperature Thermal History of Martian Meteorite ALH84001 from (U-Th)/He Thermochronometry

    NASA Astrophysics Data System (ADS)

    Min, K.; Reiners, P. W.

    2005-03-01

    Single grain (U-Th)/He ages from ALH84001 are interpreted either by (1) a single intense (maximum temperature of ~430 ºC) shock event at 15 Ma, or (2) stronger shock at sometime between (0.3-0.7) Ga and 15 Ma, followed by a minor shock at 15 Ma.

  11. [Pros and cons for Martian life: scientific debate on ALH84001].

    PubMed

    Yamashita, M

    1997-03-01

    Scientific debate related to possible martian life is summarized in this article. Even there is no firm conclusion yet to convince the existence of life on Mars, intensive studies on the meteorite ALH84001 have invoked many valuable findings. PMID:11540351

  12. A Hypothesis for the Abiotic and Non-Martian Origins of Putative Signs of Ancient Martian Life in ALH84001

    NASA Technical Reports Server (NTRS)

    Treiman, Allan H.

    2001-01-01

    Putative evidence of martian life in ALH84001 can be explained by abiotic and non-martian processes consistent with the meteorite's geological history. Additional information is contained in the original extended abstract.

  13. High-Temperature Mars-to-Earth Transfer of Meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Min, K.; Reiners, P. W.

    2006-12-01

    Mars is thought to have experienced intense volcanism, impact cratering and fluvial resurfacing during its first ~1.5 Byr, followed by a less-energetic, colder period. Rare meteoritic samples of the Martian crust provide some of the only direct evidence by which to test and develop models of the paleoenvironmental evolution of the planet, its potential habitability by life, and the process of interplanetary mass transport. Thermal histories of Martian meteorites provide crucial evidence bearing not only on long-term, ambient near-surface conditions on Mars, but also on whether meteoroids can be ejected from their large parent bodies without significant heating, a favorable condition for exogenesis (including panspermia) hypotheses. One of the best samples to address these issues is Martian meteorite ALH84001, because it has the oldest crystallization age of ~4.5 Ga, is thought to have resided near the surface since ~4.0 Ga, and has been suggested to have experienced no significant heating during or after its ejection from Mars at 15 Ma. To better constrain the thermal evolution and shock metamorphic history of ALH84001, we applied (U-Th)/He thermochronometry to single grains of merrillite and chlorapatite from ALH84001. The (U-Th)/He ages of individual phosphate grains in ALH84001 range from 60 Ma to 1.8 Ga, with a weighted mean of ~830 Ma. This broad age distribution reflects multiple diffusion domains, and requires a relatively high-temperature resetting event younger than ~60 Ma. These new data are combined with the published whole-rock (maskelynite as a main Ar reservoir) 40Ar/39Ar age spectra which show 5-8 % fractional loss of 40Ar since 4.0 Ga. He diffusion in both terrestrial and extraterrestrial apatite has a significantly higher activation energy (138 ~ 184 kJ/mol) than Ar diffusion in maskelynite (75 kJ/mol), leading to an important "kinetic crossover" in fractional loss contours for these systems. Taken together, the phosphate (U-Th)/He and maskelynite

  14. Atomic force microscopy imaging of fragments from the Martian meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Steele, A.; Goddard, D.; Beech, I. B.; Tapper, R. C.; Stapleton, D.; Smith, J. R.

    1998-01-01

    A combination of scanning electron microscopy (SEM) and environmental scanning electron microscopy (ESEM) techniques, as well as atomic force microscopy (AFM) methods has been used to study fragments of the Martian meteorite ALH84001. Images of the same areas on the meteorite were obtained prior to and following gold/palladium coating by mapping the surface of the fragment using ESEM coupled with energy-dispersive X-ray analysis. Viewing of the fragments demonstrated the presence of structures, previously described as nanofossils by McKay et al. (Search for past life on Mars--possible relic biogenic activity in martian meteorite ALH84001. Science, 1996, pp. 924-930) of NASA who used SEM imaging of gold-coated meteorite samples. Careful imaging of the fragments revealed that the observed structures were not an artefact introduced by the coating procedure.

  15. Atomic force microscopy imaging of fragments from the Martian meteorite ALH84001.

    PubMed

    Steele, A; Goddard, D; Beech, I B; Tapper, R C; Stapleton, D; Smith, J R

    1998-01-01

    A combination of scanning electron microscopy (SEM) and environmental scanning electron microscopy (ESEM) techniques, as well as atomic force microscopy (AFM) methods has been used to study fragments of the Martian meteorite ALH84001. Images of the same areas on the meteorite were obtained prior to and following gold/palladium coating by mapping the surface of the fragment using ESEM coupled with energy-dispersive X-ray analysis. Viewing of the fragments demonstrated the presence of structures, previously described as nanofossils by McKay et al. (Search for past life on Mars--possible relic biogenic activity in martian meteorite ALH84001. Science, 1996, pp. 924-930) of NASA who used SEM imaging of gold-coated meteorite samples. Careful imaging of the fragments revealed that the observed structures were not an artefact introduced by the coating procedure. PMID:11541278

  16. Ar-Ar chronology of the Martian meteorite ALH84001: evidence for the timing of the early bombardment of Mars.

    PubMed

    Turner, G; Knott, S F; Ash, R D; Gilmour, J D

    1997-09-01

    ALH84001, a cataclastic cumulate orthopyroxenite meteorite from Mars, has been dated by Ar-Ar stepped heating and laser probe methods. Both methods give ages close to 3,900 Ma. The age calculated is dependent on assumptions made about 39Ar recoil effects and on whether significant quantities of 40Ar from the Martian atmosphere are trapped in the meteorite. If, as suggested by xenon and nitrogen isotope studies, Martian atmospheric argon is present, then it must reside predominantly in the K-rich phase maskelynite. Independently determined 129Xe abundances in the maskelynite can be used to place limits on the concentration of the atmospheric 40Ar. These indicate a reduction of around 80 Ma to ages calculated on the assumption that no Martian atmosphere is present. After this correction, the nominal ages obtained are: 3940 +/- 50, 3870 +/- 80, and 3970 +/- 100 Ma. by stepped heating, and 3900 +/- 90 Ma by laser probe (1 sigma statistical errors), giving a weighted mean value of 3,920 Ma. Ambiguities in the interpretation of 39Ar recoil effects and in the contribution of Martian atmospheric 40Ar lead to uncertainties in the Ar-Ar age which are difficult to quantify, but we suggest that the true value lies somewhere between 4,050 and 3,800 Ma. This age probably dates a period of annealing of the meteorite subsequent to the shock event which gave it its cataclastic texture. The experiments provide the first evidence of an event occurring on Mars coincident with the time of the late heavy bombardment of the Moon and may reflect a similar period of bombardment in the Southern Highlands of Mars. Whether the age determined bears any relationship to the time of carbonate deposition in ALH84001 is not known. Such a link depends on whether the temperature associated with the metasomatic activity was sufficient to cause argon loss from the maskelynite and/or whether the metasomatism and metamorphism were linked in time through a common heat source. PMID:11541217

  17. Bacterial mineralization patterns in basaltic aquifers: implications for possible life in martian meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; McKay, D. S.; Wentworth, S. J.; Stevens, T. O.; Taunton, A. E.; Allen, C. C.; Coleman, A.; Gibson, E. K. Jr; Romanek, C. S.

    1998-01-01

    To explore the formation and preservation of biogenic features in igneous rocks, we have examined the organisms in experimental basaltic microcosms using scanning and transmission electron microscopy. Four types of microorganisms were recognized on the basis of size, morphology, and chemical composition. Some of the organisms mineralized rapidly, whereas others show no evidence of mineralization. Many mineralized cells are hollow and do not contain evidence of microstructure. Filaments, either attached or no longer attached to organisms, are common. Unattached filaments are mineralized and are most likely bacterial appendages (e.g., prosthecae). Features similar in size and morphology to unattached, mineralized filaments are recognized in martian meteorite ALH84001.

  18. Bacterial mineralization patterns in basaltic aquifers: Implications for possible life in Martian meteorite ALH84001

    SciTech Connect

    Thomas-Keprta, K.L.; Wentworth, S.J.; Allen, C.C.; McKay, D.S.; Gibson, E.K. Jr.; Stevens, T.O.; Taunton, A.E.; Coleman, A.; Romanek, C.S.

    1998-11-01

    To explore the formation and preservation of biogenic features in igneous rocks, the authors have examined the organisms in experimental basaltic microcosms using scanning and transmission electron microscopy. Four types of microorganisms were recognized on the basis of size, morphology, and chemical composition. Some of the organisms mineralized rapidly, whereas others show no evidence of mineralization. Many mineralized cells are hollow and do not contain evidence of microstructure. Filaments, either attached or no longer attached to organisms, are common. Unattached filaments are mineralized and are most likely bacterial appendages (e.g., prosthecae). Features similar in size and morphology to unattached, mineralized filaments are recognized in martial meteorite ALH84001.

  19. A low temperature transfer of ALH84001 from Mars to Earth.

    PubMed

    Weiss, B P; Kirschvink, J L; Baudenbacher, F J; Vali, H; Peters, N T; Macdonald, F A; Wikswo, J P

    2000-10-27

    The ejection of material from Mars is thought to be caused by large impacts that would heat much of the ejecta to high temperatures. Images of the magnetic field of martian meteorite ALH84001 reveal a spatially heterogeneous pattern of magnetization associated with fractures and rock fragments. Heating the meteorite to 40 degrees C reduces the intensity of some magnetic features, indicating that the interior of the rock has not been above this temperature since before its ejection from the surface of Mars. Because this temperature cannot sterilize most bacteria or eukarya, these data support the hypothesis that meteorites could transfer life between planets in the solar system. PMID:11052940

  20. A Low Temperature Transfer of ALH84001 from Mars to Earth

    NASA Astrophysics Data System (ADS)

    Weiss, Benjamin P.; Kirschvink, Joseph L.; Baudenbacher, Franz J.; Vali, Hojatollah; Peters, Nick T.; Macdonald, Francis A.; Wikswo, John P.

    2000-10-01

    The ejection of material from Mars is thought to be caused by large impacts that would heat much of the ejecta to high temperatures. Images of the magnetic field of martian meteorite ALH84001 reveal a spatially heterogeneous pattern of magnetization associated with fractures and rock fragments. Heating the meteorite to 40°C reduces the intensity of some magnetic features, indicating that the interior of the rock has not been above this temperature since before its ejection from the surface of Mars. Because this temperature cannot sterilize most bacteria or eukarya, these data support the hypothesis that meteorites could transfer life between planets in the solar system.

  1. Bacterial mineralization patterns in basaltic aquifers: implications for possible life in martian meteorite ALH84001.

    PubMed

    Thomas-Keprta, K L; McKay, D S; Wentworth, S J; Stevens, T O; Taunton, A E; Allen, C C; Coleman, A; Gibson, E K; Romanek, C S

    1998-11-01

    To explore the formation and preservation of biogenic features in igneous rocks, we have examined the organisms in experimental basaltic microcosms using scanning and transmission electron microscopy. Four types of microorganisms were recognized on the basis of size, morphology, and chemical composition. Some of the organisms mineralized rapidly, whereas others show no evidence of mineralization. Many mineralized cells are hollow and do not contain evidence of microstructure. Filaments, either attached or no longer attached to organisms, are common. Unattached filaments are mineralized and are most likely bacterial appendages (e.g., prosthecae). Features similar in size and morphology to unattached, mineralized filaments are recognized in martian meteorite ALH84001. PMID:11541429

  2. Chains of magnetite crystals in the meteorite ALH84001: Evidence of biological origin

    PubMed Central

    Friedmann, E. Imre; Wierzchos, Jacek; Ascaso, Carmen; Winklhofer, Michael

    2001-01-01

    The presence of magnetite crystal chains, considered missing evidence for the biological origin of magnetite in ALH84001 [Thomas-Keprta, K. L., Bazylinski, D. A., Kirschvink, J. L., Clemett, S. J., McKay, D. S., Wentworth, S. J., Vali, H., Gibson, E. K., Jr., & Romanek, C. S. (2000) Geochim. Cosmochim. Acta 64, 4049–4081], is demonstrated by high-power stereo backscattered scanning electron microscopy. Five characteristics of such chains (uniform crystal size and shape within chains, gaps between crystals, orientation of elongated crystals along the chain axis, flexibility of chains, and a halo that is a possible remnant of a membrane around chains), observed or inferred to be present in magnetotactic bacteria but incompatible with a nonbiological origin, are shown to be present. Although it is unlikely that magnetotactic bacteria were ever alive in ALH84001, decomposed remains of such organisms could have been deposited in cracks in the rock while it was still on the surface on Mars. PMID:11226212

  3. Chains of magnetite crystals in the meteorite ALH84001: evidence of biological origin.

    PubMed

    Friedmann, E I; Wierzchos, J; Ascaso, C; Winklhofer, M

    2001-02-27

    The presence of magnetite crystal chains, considered missing evidence for the biological origin of magnetite in ALH84001 [Thomas-Keprta, K. L., Bazylinski, D. A., Kirschvink, J. L., Clemett, S. J., McKay, D. S., Wentworth, S. J., Vali, H., Gibson, E. K., Jr., & Romanek, C. S. (2000) Geochim. Cosmochim. Acta 64, 4049-4081], is demonstrated by high-power stereo backscattered scanning electron microscopy. Five characteristics of such chains (uniform crystal size and shape within chains, gaps between crystals, orientation of elongated crystals along the chain axis, flexibility of chains, and a halo that is a possible remnant of a membrane around chains), observed or inferred to be present in magnetotactic bacteria but incompatible with a nonbiological origin, are shown to be present. Although it is unlikely that magnetotactic bacteria were ever alive in ALH84001, decomposed remains of such organisms could have been deposited in cracks in the rock while it was still on the surface on Mars. PMID:11226212

  4. Magnetite Formation from Thermal Decomposition of Siderite: Implications for Inorganic Magnetite Formation in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Morris, RIchard V.

    2002-01-01

    A biogenic mechanism for formation of a subpopulation magnetite in Martian meteorite ALH84001 has been suggested [McKay et al., 1996; Thomas-Keprta, et al., 2000]. We are developing experimental evidence for an alternating working hypothesis, that the subpopulation was produced inorganically by the thermal decomposition of siderite [Golden et al., 2000].

  5. Constraints on the Thermal History of Martian Meteorites ALH84001 and MIL03346 by Single Crystal XRD, Electron Microprobe and Mössbauer Analyses of Ortho- and Clinopyroxene

    NASA Astrophysics Data System (ADS)

    Domeneghetti, M. C.; Fioretti, A. M.; Cámara, F.; Carraro, A.; McCammon, C.; Tazzoli, V.

    2007-07-01

    Constraints on the thermal history of meteorites can be established by estimating the Fe2+-Mg order degree in their pyroxene using single-crystal XRD. We present here the data obtained on martian meteorites ALH84001 and MIL03346.

  6. Micro-Spectroscopy as a Tool for Detecting Micron-Scale Mineral Variations Across a Rock Surface: An Example Using a Thin Section of Martian Meteorite ALH 84001

    NASA Astrophysics Data System (ADS)

    Dalton, J. B.; Bishop, J. L.

    2003-03-01

    Visible and near-infrared spectra of a portion of martian meteorite ALH84001 were acquired using a high resolution imaging microscope to investigate imaging spectroscopy for mineral detection at small scales.

  7. A Younger Age for ALH84001 and Its Geochemical Link to Shergottite Sources in Mars

    NASA Astrophysics Data System (ADS)

    Lapen, T. J.; Righter, M.; Brandon, A. D.; Debaille, V.; Beard, B. L.; Shafer, J. T.; Peslier, A. H.

    2010-04-01

    Martian meteorite ALH84001 (ALH) is the oldest known igneous rock from Mars and has been used to constrain its early history. Lutetium-hafnium (Lu-Hf) isotope data for ALH indicate an igneous age of 4.091 ± 0.030 billion years, nearly coeval with an interval of heavy bombardment and cessation of the martian core dynamo and magnetic field. The calculated Lu/Hf and Sm/Nd (samarium/neodymium) ratios of the ALH parental magma source indicate that it must have undergone extensive igneous processing associated with the crystallization of a deep magma ocean. This same mantle source region also produced the shergottite magmas (dated 150 to 570 million years ago), possibly indicating uniform igneous processes in Mars for nearly 4 billion years.

  8. A younger age for ALH84001 and its geochemical link to shergottite sources in Mars.

    PubMed

    Lapen, T J; Righter, M; Brandon, A D; Debaille, V; Beard, B L; Shafer, J T; Peslier, A H

    2010-04-16

    Martian meteorite ALH84001 (ALH) is the oldest known igneous rock from Mars and has been used to constrain its early history. Lutetium-hafnium (Lu-Hf) isotope data for ALH indicate an igneous age of 4.091 +/- 0.030 billion years, nearly coeval with an interval of heavy bombardment and cessation of the martian core dynamo and magnetic field. The calculated Lu/Hf and Sm/Nd (samarium/neodymium) ratios of the ALH parental magma source indicate that it must have undergone extensive igneous processing associated with the crystallization of a deep magma ocean. This same mantle source region also produced the shergottite magmas (dated 150 to 570 million years ago), possibly indicating uniform igneous processes in Mars for nearly 4 billion years. PMID:20395507

  9. Three-Dimensional Morphological Analysis of ALH84001 Magnetite Using Electron Tomography

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Shimmin, Joel; Morphew, Mary; McIntosh, J. Richard; Bazylinski, Dennis A.; Kirschvink, Joseph L.; Wentworth, Susan J.; McKay, David S.; Vali, Hojatollah

    2003-01-01

    We report here the crystal morphologies of MV-1 and ALH84001 magnetites as calculated by back-projection using electron tomography. In the present study, we used a 300 keV TEM with a field emission gun (Tecnai F-30 from FEI Inc.), equipped with a 2048 x 2048 pixel CCD camera from Gatan Inc. to image magnetite crystals over tilt ranges of approx. +/- 72 deg in 2 deg tilt intervals. The images were aligned for back-projection, either manually, or through the use of fiducial 5 nm Au spheres affixed to the specimen prior to microscopy. Three-dimensional (3-D) reconstructions were computed using weighted back-projection of the tilted views. The tomograms were viewed and analyzed as a series of slices 1.0 nm thick, taken parallel to the specimen-supporting grid, using the IMOD software package. The shape of each magnetite crystal was determined by defining the external contour of a given magnetite in each slice and assembling a stack of these contours in 3-D. To aid in visualization, the stacked contour array was reduced to an optimal mesh by Delaunay triangulation. The surface normal to each of the triangles in the mesh was calculated and the triangle faces colored according to the orientation of that surface normal relative to the principal crystallographic axis of magnetite. Green surfaces correspond to {111} orientations, blue surfaces to {100} orientations, and red surfaces to {110} orientations. Triangles whose surface normal did not correspond to one of the principal axes were colored gray. Within the experimental and numerical uncertainties of the deconvolution, the tomographic reconstruction of both MV-1 and ALH84001 magnetites are equivalent and correspond to a truncated hexa-octahedral morphology.

  10. Study of a possible magnetite biosignature in Martian meteorite ALH84001: Implications for the biological toxicology of Mars

    NASA Astrophysics Data System (ADS)

    Thomas-Keprta, Kathie Louise

    "Why do we have such a longstanding fascination with Mars? Very simply put, it's about life. The search for life elsewhere in our Solar System has been a major driver for exploring Mars, pretty much since we began seriously looking at that planet."1 The major objective of this work is to describe signs of possible life, that is biosignatures, in rocks from Mars if indeed they are present. Biosignatures are specific identifiable properties that result from living things; they may be implanted in the environment and may persist even if the living thing is no longer present. Over 100 mineral biosignatures have been discussed in the literature; however, only one, magnetite, is addressed by this study. Magnetite is found in many rock types on earth and in meteorites. Previous studies of terrestrial magnetite have used few properties, such as size and chemical composition, to determine one of the modes of origins for magnetite (e.g., biogenic, inorganic). This study has established a rigorous set of six criteria for the identification of intracellularly precipitated biogenic magnetite. These criteria have been applied to a subpopulation of magnetites embedded within carbonates in Martian meteorite ALH84001. These magnetites are found to be chemically and physically indistinguishable from those produced by magnetotactic bacteria strain MV-1, hence, they were likely formed by biogenic processes on ancient Mars. These criteria may be also used to distinguish origins for magnetites from terrestrial samples with complex or unknown histories. The presence of purported past life on early Mars suggests that, if life once began it may still exist today, possibly in oases in the Martian subsurface. Future manned missions should consider potential hazards of an extant biological environment(s) on Mars. 1 Quote attributed to Jack Farmer of Arizona State University in discussing NASA's program of Mars Exploration (see "Deciphering Mars: Follow the Water," Astrobiology Magazine Sept

  11. Siderophile Trace Elements in ALH 84001 and Other Achondrites: A Temporal Increase of Oxygen Fugacity in the Martian Mantle?

    NASA Astrophysics Data System (ADS)

    Warren, P. H.; Kallemeyn, G. W.

    1995-09-01

    We have employed neutron activation, including radiochemical NAA, to investigate SNC/martian meteorites ALH 77005, ALH 84001 and LEW 88516, along with 15 eucrites. Our data for 10 manifestly monomict eucrites confirm previous indications [e.g., 1] that compositionally pristine eucrites are generally extremely siderophile-poor, although for several of the most extremely siderophile-depleted eucrites we find slight enhancements in Re/Os (Figure). Our RNAA data are the first for highly siderophile elements in polymict eucrites, and show a broad similarity with lunar polymict breccias. In general, our data (e.g., Ga/Al = 4.3x10^-4) confirm SNC affinity [2] for ALH84001. However, siderophile concentrations are, by SNC standards, extraordinarily low: Ni = 5.8 micrograms/g and (in pg/g) Au = 9.4, Ir = 80, Os = 10.2, and Re = 1.66+/-0.25(1-s); Ge (1080 ng/g) is typical for SNCs. Like terrestrial basalts [1], other SNCs have relatively constant Re, ranging from 28 (Lafayette [3]) to 102 pg/g (ALH 77005) among seven analyzed meteorites of various types, in which Os ranges from <2.3 to 4400 pg/g. A plot of Os vs. Re/Os (Figure) shows that ALH 84001 has 23x lower Re than expected for a young SNC of similar Os content. On Earth, Re generally behaves as a mildly incompatible element, whereas Os behaves as a strongly compatible element. A plausible explanation for this divergence [1] is that Re is more prone to enter higher oxidation states, such as Re^4+, which would tend to behave like W^4+. This model is consistent with the Os-like behavior of Re in the highly reduced lunar and eucritic environments, and Birck and Allegre [1] interpret the typically intermediate Re contents of SNCs as suggestive of origin from a mantle source region at intermediate fO(sub)2 (they also considered, but rejected, an implausible "contamination" model). Extended to ALH 84001, this model implies that the mantle source was at a substantially (roughly 1.7 log(sub)10 units) lower fO2 than the analogous

  12. FTIR Analysis of Water in Pyroxene and Plagioclase in ALH 84001 and Nakhlites

    NASA Technical Reports Server (NTRS)

    Peslier, A. H.; Cintala, M. J.; Montes, R.; Cardenas, F.

    2016-01-01

    with crustal reservoirs or hydrothermal fluids. Here, nominally anhydrous minerals (pyroxene, olivine, plagioclase, or maskelynite) in orthopyroxenite ALH 84001 and selected nakhlites are analyzed for water and major elements, in order to determine 1) whether they contain any water; 2) if they do, what controls its distribution (crystallization, degassing, hydrothermal or impact processes); and 3) if any of these measurements can be used to infer the water contents of the parent magma and their mantle sources. A shock-reverberation experiment was also performed on terrestrial orthopyroxenes (opx) to simulate the heavily shocked conditions of ALH 84001 (> 31 GPa [17]).

  13. A Single Grain U-Pb and Pb-Pb Dating and D/H Ratios of the Phosphate Mineral in ALH84001

    NASA Astrophysics Data System (ADS)

    Koike, M.; Ota, Y.; Takahata, N.; Sano, Y.; Sugiura, N.

    2012-12-01

    There are many studies that determine U-Pb and Pb-Pb ages of phosphates in Martian meteorites. Phosphate minerals such as an apatite (Ca5(PO4)3[OH, F, Cl]) and a whitlockite (Ca9 [Mg, Fe2+] (PO4)6 PO3OH) contain water in the form of OH, which provides us hydrogen isotopic information. The goal of this study is to obtain a crystallization age and hydrogen isotopic distributions of each grain and to relate them to the surface evolution of Mars. ALH84001 is known to be about 4 billion years old [1]. Its carbonates and maskelynite showed high D/H ratios with large deviations, which indicates large fractionation at early Mars surface [2]. Due to small grain sizes and limited spatial resolutions of measurements, previous studies used several grains for one age or one series of isotopic distributions. Here we determined single grain ages and D/H ratios using NanoSIMS with a high spatial resolution. A thin section of ALH84001 was polished and carbon-coated. The section was then observed by SEM-EDS to locate phosphate minerals. A large phosphate grain (>100μm) was found and analyzed by NanoSIMS. A ~10nA O- primary ion beam (with spot diameter of ~20μm) was used for U-Pb and Pb-Pb measurements and a ~1nA (spot diameter of <10μm) was for D/H ratio measurements. An apatite from a Prairie Lake circular complex, PRAP, with a known age (1156 Ma; [3]) was used as a standard for U-Pb. The D/H ratio and the water content of an apatite from Morocco were measured by conventional methods to use as a D/H standard. 238U-206Pb isochron, 207Pb-206Pb isochron, and total U-Pb isochron age, a regression line in 3-D space (238U/206Pb-207Pb/206Pb-204Pb/206Pb) showed a consistent age ~4 Ga. The ages obtained in this study were also consistent with previous U-Pb dating within experimental errors. D/H ratios in the same grain showed high values and a considerable deviation, which seems to be due to mixing of terrestrial water. References: [1] Terada K. et al. 2003 Meteoritics & Planet. Sci. 38

  14. Nitrogen and Argon in ALH 84001 Revisited: Unravelling a Martian Atmospheric Component

    NASA Astrophysics Data System (ADS)

    Grady, M. M.; Wright, I. P.; Pillinger, C. T.

    1996-03-01

    We have measured nitrogen and argon released simultaneously upon combustion of two samples of ALH 84001 (A84). Both nitrogen and argon appeared to be heterogeneously distributed in the rock: one sample liberated very little gas above blank levels, whereas the second sample, selected because it contained abundant material from the "crush zones", was rich in both species. Using the ^40Ar/^14N ratio and delta ^15N of the gas liberated above 700 degrees C from this second sample, an attempt has been made to calculate the relative quantities of adsorbed terrestrial gases and trapped martian atmospheric species. Following from this, excess ^40Ar attributed to radiogenic production from potassium decay can be used to determine a K-Ar age of the sample. We calculate that ~17.5% of the total ^40Ar is indigenous to the sample. Assuming that the trapped component would have a ^40Ar/^14N ratio equivalent to that in the present-day martian atmosphere (~0.33), then there is a small excess of ^40Ar (amounting to about 1.5% of the total ^40Ar). Taking a reasonable estimate of the potassium abundance (100-200 ppm) implies that A84 has a K-Ar age of ~0.76-1.28 Gyr, which is much younger than ages determined in previous studies and using other methods.

  15. Ion microprobe measurements of 18O/ 16O ratios of phosphate minerals in the Martian meteorites ALH84001 and Los Angeles

    NASA Astrophysics Data System (ADS)

    Greenwood, James P.; Blake, Ruth E.; Coath, Christopher D.

    2003-06-01

    Oxygen isotope ratios of merrillite and chlorapatite in the Martian meteorites ALH84001 and Los Angeles have been measured by ion microprobe in multicollector mode. δ 18O values of phosphate minerals measured in situ range from ˜3 to 6‰, and are similar to Martian meteorite whole-rock values, as well as the δ 18O of igneous phosphate on Earth. These results suggest that the primary, abiotic, igneous phosphate reservoir on Mars is similar in oxygen isotopic composition to the basaltic phosphate reservoir on Earth. This is an important first step in the characterization of Martian phosphate reservoirs for the use of δ 18O of phosphate minerals as a biomarker for life on Mars. Cumulative textural, major-element, and isotopic evidence presented here suggest a primary, igneous origin for the phosphates in Los Angeles and ALH84001; textural and chemical evidence suggests that phosphates in ALH84001 were subsequently shock-melted in a later event.

  16. Implications of noble gases in a recently recognized Martian meteorite (ALH84001) for the degassing history of Mars

    NASA Technical Reports Server (NTRS)

    Swindle, T. D.

    1994-01-01

    For terrestrial planets, atmospheric compositions are not static, but evolve with time, in part due to degassing of the interior. Unfortunately, the evolution is slow enough that it is usually not observable on human timescales, or even on the timescales of rocks that preserve samples of Earth's ancient atmosphere. Preliminary results on a recently recognized Martian meteorite, ALH84001, indicate that it is a very old rock, and has a relatively high noble gas content suggestive of atmospheric incorporation, but with an isotopic composition slightly inconsistent with currently known Martian reservoirs. Hence, this rock may provide a sample of ancient Martian atmosphere, which can be used to test models of volatile evolution (in particular, degassing) on Mars. ALH84001 is a cumulate orthopyroxenite. Although originally classified as a diogenite, its oxygen isotopes, and several chemical and petrographic features, strong suggest that it is, like the SNC meteorites, Martian. A Sm-Nd crystallization age of 4.5 Ga has been reported. The meteorite is rich in noble gases, compared to most SNC's. In many respects the noble gases are typical of SNC meteorites. However, there are some subtle differences. In particular, the Xe isotopes in SNC meteorites can be explained as a mixture of Martian atmospheric Xe (as represented by glass in EETA 79001), the Xe in the dunite Chassigny (usually assumed to be representative of the Martian interior, and with lower (129)Xe/(132)Xe, (134)Xe/(132)Xe and (136)Xe/(132)Xe ratios), and later additions from known processes like fission, spallation and terrestrial contamination. The isotopic composition of ALH84001 is inconsistent (at greater than 2-3 sigma) with any mixture of those components. Even if no accumulation of fission Xe during the age of the rock is assumed, there is too little (136)Xe and (134)Xe for the amount of (129)Xe measured.

  17. The search for terrestrial nanobacteria as possible analogs for purported Martian nanofossils in the Martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Thomas-Keprta, Kathie L.; Wentworth, Susan J.; McKay, David S.; Stevens, Todd O.; Golden, D. C.; Allen, Carlton C.; Gibson, E. K.

    1997-03-01

    Basalts from the Columbia River (CRB) are studied in order to examine the igneous rock types similar to the main lithology of ALH84001. High resolution SEM and TEM are used to examine Columbia River surfaces for microorganisms in situ and those extracted from the basalt surface. Philips XL 40 field emission gun SEM microscope observations show the presence of small, nanometer-scale coccoid (spheroidal) bacteria on DC-06 and DB-11. It is suggested that these forms may be nanobacteria or appendages of bacteria from CRB samples. Another possibility is that they may be dwarf bacteria.

  18. Carbonate and Magnetite Parageneses as Monitors of Carbon Dioxide and Oxygen Fugacity

    NASA Technical Reports Server (NTRS)

    Koziol, Andrea M.

    2000-01-01

    The stable coexistence of siderite with other key minerals, such as graphite or magnetite, is only possible under certain restrictive conditions of CO2 and O2 fugacity. Carbonate parageneses in Mars meteorite ALH 84001 are analyzed.

  19. Organic Carbon Exists in Mars Meteorites: Where is it on the Martian Surface?

    NASA Technical Reports Server (NTRS)

    McKay, D. S.; Clemett, S. J.; Gibson, E. K., Jr.; Thomas-Keprta, K. L.; Wentworth, S. J.

    2010-01-01

    The search for organic carbon on Mars has been a major challenge. The first attempt was the Viking GC-MS in situ experiment which gave inconclusive results at two sites oil. After the discovery that the SNC meteorites were from Mars, reported C isotopic compositional information which suggested a reduced C component present in the Martian meteorites reported the presence of reduced C components (i.e., polycyclic aromatic hydrocarbons) associated with the carbonate globules in ALH84001. Jull et al. noted in Nakhla there was acid insoluble C component present with more than 75% of its C lacking any C-14, which is modern-day terrestrial carbon. This C fraction was believed to be either indigenous martian or ancient meteoritic carbon. Fisk et al. have shown textural evidence along with C-enriched areas within fractures in Nakhla and ALH84001. Westall et al. have shown the presence of a large irregular fragment of organic material completely embedded within a chip of ALH84001. Interior samples from the Naklnla SNC made available by the British Museum of Natural History, were analyzed. Petrographic examination of Nakhla showed evidence of fractures (approx.0.5 microns wide) filled with dark brown to black dendritic material with characteristics similar to those observed by. Iddingsite is also present along fractures in olivine. Fracture filling and dendritic material was examined by SEM-EDX, TEM-EDX, Focused Electron Beam microscopy, Laser Raman Spectroscopy, Nano-SIMS Ion Micro-probe, and Stepped-Combustion Static Mass Spectrometry. Observations from the first three techniques are discussed.

  20. Identification of carbonate-rich outcrops on Mars by the Spirit rover.

    PubMed

    Morris, Richard V; Ruff, Steven W; Gellert, Ralf; Ming, Douglas W; Arvidson, Raymond E; Clark, Benton C; Golden, D C; Siebach, Kirsten; Klingelhöfer, Göstar; Schröder, Christian; Fleischer, Iris; Yen, Albert S; Squyres, Steven W

    2010-07-23

    Decades of speculation about a warmer, wetter Mars climate in the planet's first billion years postulate a denser CO2-rich atmosphere than at present. Such an atmosphere should have led to the formation of outcrops rich in carbonate minerals, for which evidence has been sparse. Using the Mars Exploration Rover Spirit, we have now identified outcrops rich in magnesium-iron carbonate (16 to 34 weight percent) in the Columbia Hills of Gusev crater. Its composition approximates the average composition of the carbonate globules in martian meteorite ALH 84001. The Gusev carbonate probably precipitated from carbonate-bearing solutions under hydrothermal conditions at near-neutral pH in association with volcanic activity during the Noachian era. PMID:20522738

  1. Reduced Martian Carbon: Evidence from Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Gibson, Everett K.; McKay, David S.; Thomas-Keprta, Kathie L.; Clemett, SImon J.; Pillinger, COlin T.; Wright, Ian P.; Verchovsky, A. P.

    2010-01-01

    Identification of indigenous reduced carbon species on Mars has been a challenge since the first hypotheses about life on Mars were proposed. Ranging from the early astronomical measurements to analyses of samples from the Martian surface in the form of Martian meteorites. The first direct attempt to analyze the carbon species on the surface was in 1976 with the Viking GC-MS in-situ experiment which gave inconclusive results at two sites on Mars [1]. With the recognition in 1983 that samples of the Martian surface were already present on Earth in the form of Martian meteorites by Bogard and Johnson [2] new opportunities became available for direct study of Mars's samples in te rlraesbtrioalratories. Carbon isotopic compositional information suggested a reduced carbon component was present in the Martian meteorites [3-5]. Polycyclic aromatic hydrocarbons associated with carbonate globules in ALH84001 were later identified [6,7]. Jull et al [8] noted that an insoluble component was present within Nakhla and more than 75% of its C lacked any 14C, which is modern-day carbon contaminant. This carbon fraction was believed to be either indigenous (i..e. Martian) or ancient meteoritic carbon phase. Within the fractures of Nakhla and ALH84001, Fisk et al [9,10] identified reduced carbon-enriched areas. Gibson et al. [11] using a combination of NanoSIMS, Focused Electron microscopy, Laser Raman Spectroscopy and Stepped-Combustion Static Mass Spectrometry analyses the presence of possible indigenous reduced carbon components within the 1.3 Ga old Nakhla.

  2. Carbonate Cements from the Sverrefjell and Sigurdfjell Volcanoes, Svalbard Norway: Analogs for Martian Carbonates

    NASA Technical Reports Server (NTRS)

    Blake, D. F.; Treiman, A. H.; Morris, R.; Bish, D.; Amundsen, H.E.F.; Steele, A.

    2011-01-01

    The Sverrefjell and Sigurdfjell volcanic complexes erupted at 1Ma on Svalbard, Norway. Sverrefjell is a cone of cinders, pillow lavas and dikes; Sigurdfjell is elongate in outcrop and may represent a fissure eruption [1]. The lavas of both volcanos were volatile rich. The volcanos erupted under ice and were subsequently dissected by glaciation (glacial eratics are present on most of Sverrefjell, even on its summit). Eruption beneath an ice sheet is inferred, based on the presence of pillow lavas from near sea level to 1000 m above sea level. Sverrefjell contains the largest fraction of ultramafic xenoliths of any volcanic complex in the world, in places accounting for as much as 50% of the volume of the outcrop. The Sverrefjell and Sigurdfell volcanos contain carbonate cements of several varieties: (1) Amundsen [2] reported Mg-Fe-rich carbonate in sub-mm globules in basalts and ultramafic xenoliths from the volcanos. These globules are the best terrestrial analogs to the carbonate globules in the Mars meteorite ALH84001 [3]. (2) Thick (1-3 cm) coatings of carbonate cement drape the walls of vertical volcanic pipes or conduits on the flanks and near the present summit of Sverrefjell. Similar occurrences are found on Sigurdfjell. (3) Breccia-filled pipes or vents occur on Sverrefjell and Siggurdfjell in which the breccia fragments are cemented by carbonate. The fragments themselves commonly contain carbonate globules similar to those found in the basalts and ultramafic xenoliths.

  3. Bulk and stable isotopic compositions of carbonate minerals in Martian meteorite Allan Hills 84001: no proof of high formation temperature.

    PubMed

    Treiman, A H; Romanek, C S

    1998-07-01

    Understanding the origin of carbonate minerals in the Martian meteorite Allan Hills (ALH) 84001 is crucial to evaluating the hypothesis that they contain traces of ancient Martian life. Using arguments based on chemical equilibria among carbonates and fluids, an origin at >650 degrees C (inimical to life) has been proposed. However, the bulk and stable isotopic compositions of the carbonate minerals are open to multiple interpretations and so lend no particular support to a high-temperature origin. Other methods (possibly less direct) will have to be used to determine the formation temperature of the carbonates in ALH84001. PMID:11543073

  4. Bulk and Stable Isotopic Compositions of Carbonate Minerals in Martian Meteorite Allan Hills 84001: No Proof of High Formation Temperature

    NASA Technical Reports Server (NTRS)

    Treiman, Allan H.; Romanek, Christopher S.

    1998-01-01

    Understanding the origin of carbonate minerals in the Martian meteorite Allan Hills (ALH) 84001 is crucial to evaluating the hypothesis that they contain traces of ancient Martian life. Using arguments based on chemical equilibria among carbonates and fluids, an origin at greater than 650 C (inimical to life) has been proposed. However, the bulk and stable isotopic compositions of the carbonate minerals are open to multiple interpretations and so lend no particular support to a high-temperature origin. Other methods (possibly less direct) will have to be used to determine the formation temperature of the carbonates in ALH 84001.

  5. Stable Isotope Composition of Carbonates Formed in Low-Temperature Terrestrial Environments as Martian Analogs

    NASA Astrophysics Data System (ADS)

    Socki, R. A.; Gibson, E. K., Jr.; Perry, E. C., Jr.; Galindo, C.; Golden, D. C.; Ming, D. W.; McKay, G. A.

    2004-03-01

    We report the C and O isotope composition of carbonate minerals that formed in two low-temperature environments. Results show an overall depletion of ^18O and ^13C as a function of the extent of meteoric diagenesis. These data are used as analogs to carbonates that have been found in ALH84001.

  6. Analysis of Arctic Carbonates Profiles by Raman Spectroscopy using Exomars Raman Laser Spectrometer

    NASA Astrophysics Data System (ADS)

    Sansano, A.; López, G.; Medina, J.; Rull, F.

    2011-10-01

    This work details the analysis performed by Raman spectroscopy on carbonate samples from the Svalbard Islands (Norway) in the Arctic. This place is considered a potential Martian analog because the carbonate formation show close similarities with the formation in ALH84001 meteorite. The results obtained illustrate the performances of the Raman instrument included in the Exomars (ESA) mission.

  7. Discovery of Carbonate-Rich Outcrops in the Gusev Crater Columbia Hills by the MER Rover Spirit

    NASA Technical Reports Server (NTRS)

    Morris, Richard V.; Ruff, Steven W.; Gellert, Ralf; Ming, Douglas W.; Arvidson, Raymond E.; Clark, Benton C.; Golden, Dadi C.; Siebach, Kirsten L.; Klingelhoefer, Goestar; Schroeder, Christian; Fleischer, Iris; Yen, Albert S.; Squyres, Steven W.

    2010-01-01

    The chemical composition, global abundance, distribution, and formation pathways of carbonates are central to understanding aqueous processes, climate, and habitability of early Mars. The Mars Exploration Rover (MER) Spirit analyzed a series of olivine-rich outcrops while descending from the summit region of Husband Hill into the Inner Basin of the Columbia Hills of Gusev Crater to the eastern edge of the El Dorado ripple field in late 2005. Reanalysis of Spirit s mineralogical data from the Moessbauer Spectrometer (MB) and the Miniature Thermal Emission Spectrometer (Mini-TES) and chemical data from the Alpha Particle X-Ray Spectrometer (APXS) in 2010, coupled with new laboratory data for carbonate-bearing samples, lead to identification of carbonate in one of the outcrops (Comanche) [Morris, R.V., et al., Science, 329, 421-424]. The carbonate is rich in magnesium and iron (Mc62Sd25Cc11Rh2, assuming all Ca and Mn is associated with the carbonate) and is a major component of the Comanche outcrops (16 to 34 wt.%). The mineralogical, chemical, and abundance data are constrained in multiple, mutually consistent ways by the MER analyses. For example, a low-Ca carbonate is required by the MB and APXS data and is consistent with Mini-TES data. Three spectral features attributable to fundamental infrared vibrational modes of low-Ca carbonate are present in the Mini-TES spectra of Comanche outcrops. The average composition of Comanche carbonate approximates the average composition of the carbonate globules in Martian meteorite ALH 84001. Analogy with ALH 84001, terrestrial, and synthetic carbonate globules suggests that Comanche carbonate precipitated from aqueous solutions under hydrothermal conditions at near neutral pH in association with volcanic activity during the Noachian era. Comanche outcrop morphology suggests they are remnants of a larger carbonate-bearing formation that evolved in ultramafic rock and then preferentially eroded by a combination of aeolian

  8. Characterization of Spitsbergen Disks by Transmission Electron Microscopy and Raman Spectroscopy

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Clemett, S. J.; Le, L.; Ross, K.; McKay, David S.; Gibson, E. K., Jr.

    2010-01-01

    'Carbonate disks' found in the fractures and pores spaces of peridotite xenoliths and basalts from the island of Spitsbergen in the Norwegian Svalbard archipelago have been suggested to be "The best (and best documented) terrestrial analogs for the [Martian meteorite] ALH84001 carbonate globules ..." Previous studies have indicated that Spitsbergen carbonates show broadly comparable internal layering and mineral compositions to ALH84001 carbonate-magnetite disks. We report here for the first time, the detailed mineral characterization of Spitsbergen carbonates and their spatial relationship to the host mineral assemblages in the xenolith, using high resolution TEM (as used previously for ALH84001 carbonate disks). These studies were conducted in concert with complementary Raman and SEM analysis of the same samples. Our results indicate that there are significant chemical and physical differences between the disks in Spitsbergen and the carbonates present in ALH84001.

  9. The role of vaterite and aragonite in the formation of pseudo-biogenic carbonate structures: implications for Martian exobiology.

    PubMed

    Vecht, A; Ireland, T G

    2000-08-01

    A simple synthesis of various forms of calcium carbonate with spherical and 'floral' morphologies is reported. Vaterite formation occurs at approximately 25 degrees C, aragonite at approximately 70 degrees C and calcite at about approximately 80 degrees C. These are produced when CO2 is reacted with an aqueous solution of calcium chloride in the presence of ammonia. These conditions may have existed at the surface of Mars in the past, leading us to conclude that such mineral formations may be common there. Although the initial phases are modified over time with changing temperature and pressure conditions, they still influence the final morphology of the carbonates observed. A comparison of these structures with those found in the Martian meteorite ALH84001 suggests, but does not confirm, a non-biogenic origin for the ALH84001 carbonates. PMID:11543352

  10. A Terrestrial Analogue from Spitsbergen (Svalbard, Norway) for the Comanche Carbonate at Gusev Crater, Mars

    NASA Technical Reports Server (NTRS)

    Morris, Richard V.; Blake, D. F.; Bish, D.; Ming, Douglas W.; Agresti, D. G.; Treiman, A. H.; Steele, A.; Amundsen, H. E. F.

    2011-01-01

    Carbonate occurs at the Comanche outcrops in Gusev Crater on the basis of analyses made by the Mars Exploration Rover Spirit [1]. Taken together, mineralogical data from Spirit's Moessbauer (MB) and Mini-TES spectrometer and chemical data from the APXS spectrometer show that Comanche carbonate has an Mg-Fe-rich bulk chemical composition, is present at high concentrations, and is distributed throughout the outcrop and not just at the MB and APXS analysis location. The granular outcrop texture and the observation that it appears to be resistant to weathering compared with surrounding material [1] imply that the carbonate may be present as a cement. A hydrothermal origin for the Comanche carbonate was inferred by analogy with laboratory experiments and with a carbonate occurrence within the Bockfjord volcanic complex on the island Spitsbergen (Svalbard, Norway) [1]. The laboratory carbonates, synthesized by precipitation from hydrothermal solutions, have (MB) parameters and average bulk chemical compositions that are characteristic of Comanche carbonate. The connection to Comanche carbonate is only through chemical data for certain occurrences of Spitsbergen carbonates. In fact, the common average bulk chemical composition for these Spitsbergen carbonates, the synthetic carbonates, the Comanche carbonate, and also the carbonate globules found in martian meteorite ALH84001 is a chemical constraint consistent with a hydrothermal formation process for all the carbonates [e.g., 1-3]. We develop here a link between MB data for the Comanche carbonate from MER and MB data for certain Spitsbergen carbonate occurrences from laboratory measurements. We also obtained visible and near- IR spectra on Spitsbergen carbonates for comparison with martian carbonate detections made on the basis of CRISM spectral data, e.g., in Nili Fossae [4].

  11. Field Characterization of the Mineralogy and Organic Chemistry of Carbonates from the 2010 Arctic Mars Analog Svalbard Expedition by Evolved Gas Analysis

    NASA Technical Reports Server (NTRS)

    McAdam, A. C.; Ten Kate, I. L.; Stern, J. C.; Mahaffy, P. R.; Blake, D. F.; Morris, R. V.; Steele, A.; Amundson, H. E. F.

    2011-01-01

    The 2010 Arctic Mars Analog Svalbard Expedition (AMASE) investigated two geologic settings using methodologies and techniques being developed or considered for future Mars missions, such as the Mars Science Laboratory (MSL), ExoMars, and Mars Sample Return. The Sample Analysis at Mars (SAM) [1] instrument suite, which will be on MSL, consists of a quadrupole mass spectrometer (QMS), a gas chromatograph (GC), and a tunable laser mass spectrometer (TLS); all will be applied to analyze gases created by pyrolysis of samples. During AMASE, a Hiden Evolved Gas Analysis-Mass Spectrometer (EGA-MS) system represented the EGA-MS capability of SAM. Another MSL instrument, CheMin, will use x-ray diffraction (XRD) and x-ray fluorescence (XRF) to perform quantitative mineralogical characterization of samples [e.g., 2]. Field-portable versions of CheMin were used during AMASE. AMASE 2010 focused on two sites that represented biotic and abiotic analogs. The abiotic site was the basaltic Sigurdfjell vent complex, which contains Mars-analog carbonate cements including carbonate globules which are excellent analogs for the globules in the ALH84001 martian meteorite [e.g., 3, 4]. The biotic site was the Knorringfjell fossil methane seep, which featured carbonates precipitated in a methane-supported chemosynthetic community [5]. This contribution focuses on EGA-MS analyses of samples from each site, with mineralogy comparisons to CheMin team results. The results give insight into organic content and organic-mineral associations, as well as some constraints on the minerals present.

  12. Mineral Biomarkers in Martian Meteorite Allan Hills 84001?

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Bazylinski, D. A.; Wentworth, S. J.; McKay, D. S.; Golden, D. C.; Gibson, E. K., Jr.; Romanek, C. S.

    1998-01-01

    The occurrence of fine-grained magnetite in the Fe-rich rims surrounding carbonate globules in the martian meteorite ALH84001, originally described in , have been proposed as fossil remains of primitive martian organisms. Here we report observations on size and shape distributions of magnetites from ALH84001 and compare them to biogenic and inorganic magnetite crystals of terrestrial origin. While some magnetite morphology is not unequivocally diagnostic for its biogenicity, such as cubodial forms of magnetite, which are common in inorganically formed magnetites, other morphologies of magnetite (parallel-epiped or elongated prismatic and arrowhead forms) are more likely signatures of biogenic activity. Some ALH 84001 magnetite particles described below have unique morphology and length-to-width ratios that are indistinguishable from a variety of terrestrial biogenic magnetite and distinct from all known inorganic forms of magnetite.

  13. Possible Evidence for Life in ALH84001

    NASA Technical Reports Server (NTRS)

    McKay, David; Gibson, Everett K., Jr.; Thomas-Keprta, Kathie

    1999-01-01

    Since our original paper Science in August 1996, considerable new data has appeared from laboratories throughout the world, and our own team has had a chance to examine the sample in greater detail. The following summary touches on our original data and interpretation, and points out new data from us and from other groups, and the resulting changes and refinements in interpretations which we have made during the past three years.

  14. Possible Evidence for Life in ALH84001

    NASA Technical Reports Server (NTRS)

    McKay, David; Gibson, Everett; Thomas-Keprta, Kathie

    1999-01-01

    Since our original paper in Science in August 1996, considerable new data has appeared from laboratories throughout the world, and our own team has had a chance to examine the sample in greater detail. The following summary touches on our original data and interpretation, and points out new data from us and from other groups, and the resulting changes and refinements in interpretations which we have made during the past three years. Additional information is contained in the original extended abstract.

  15. Rare Potassium-Bearing Mica in Allan Hills 84001: Additional Constraints on Carbonate Formation

    NASA Technical Reports Server (NTRS)

    Brearley, A. J.

    1998-01-01

    There have been presented several intriguing observations suggesting evidence of fossil life in martian orthopyroxenite ALH 84001. These exciting and controversial observations have stimulated extensive debate over the origin and history of ALH 84001, but many issues still remain unresolved. Among the most important is the question of the temperature at which the carbonates, which host the putative microfossils, formed. Oxygen- isotopic data, while showing that the carbonates are generally out of isotopic equilibria with the host rock, cannot constrain their temperature of formation. Both low- and high-temperature scenarios are plausible depending on whether carbonate growth occurred in an open or closed system. Petrographic arguments have generally been used to support a high-temperature origin but these appear to be suspect because they assume equilibrium between carbonate compositions that are not in contact. Some observations appear to be consistent with shock mobilization and growth from immiscible silicate-carbonate melts at high temperatures. Proponents of a low-temperature origin for the carbonates are hampered by the fact that there is currently no evidence of hydrous phases that would indicate low temperatures and the presence of a hydrous fluid during the formation of the carbonates. However, the absence of hydrous phases does not rule out carbonate formation at low temperatures, because the carbonate forming fluids may have been extremely CO2 rich, such that hydrous phases would not have been stabilized. In this study, I have carried out additional Transmission electron microscopy (TEM) studies of ALH-84001 and have found evidence of very rare phyllosilicates, which appear to be convincingly of pre-terrestrial origin. At present these observations are limited to one occurrence: further studies are in progress to determine if the phyllosilicates are more widespread.

  16. Effect of Carbonic Anhydrase II in Molten Globule State on Physical Properties of Dimyristoylphosphatidylcholine Liposome

    NASA Astrophysics Data System (ADS)

    Sakai, Hiroko; Tanaka, Michiko; Imai, Kenichiro; Sonoyama, Masashi; Mitaku, Shigeki

    2001-05-01

    Ultrasonic relaxation measurement was employed for confirmation of the interaction between dimyristoylphosphatidylcholine (DMPC) membrane and a soluble protein, carbonic anhydrase II (CA II). The enhancement of the fluctuation of DMPC membrane structure was observed in the presence of CA II under acidic condition, pH 3.6-4, indicating the interaction between DMPC and CA II@. The pyrene fluorescence spectrum of CA II solution clearly showed that this protein adopted an unfolding intermediate called the molten globule state under the low pH condition, in which CA II interacted with DMPC@. However, CA II in the molten globule state did not cause membrane lysis in contrast to the high lytic activity of α-lactalbumin on DMPC liposomes.

  17. Chemical and Isotopic Study of Lab-formed Carbonates Under Cryogenic and Hydrothermal Conditions

    NASA Technical Reports Server (NTRS)

    Niles, P. B.; Leshin, L. A.; Socki, R. A.; Guan, Y.; Golden, D. C.; Ming, D. W.; Gibson, E. K.

    2004-01-01

    Aqueous environments on early Mars were probably relatively short-lived and localized, as evidenced by the lack of abundant secondary minerals detected by the TES instrument. In order to better understand the aqueous history of early Mars we need to be able to interpret the evidence preserved in secondary minerals formed during these aqueous events. Carbonate minerals, in particular, are important secondary minerals for interpreting past aqueous environments as illustrated by the carbonates preserved in ALH84001. Carbonates formed in short-lived, dynamic aqueous events often preserve kinetic rather than equilibrium chemical and isotopic processes, and predicting the behavior of such systems is facilitated by empirical data.

  18. Modeling Chemical and Isotopic Variations in Lab Formed Hydrothermal Carbonates

    NASA Technical Reports Server (NTRS)

    Niles, P. B.; Leshin, L. A.; Golden, D. C.; Socki, R. A.; Guan, Y.; Ming, D. W.

    2005-01-01

    Chemical and mineralogical data (e.g. [1]) from Mars suggest that the history of liquid water on the planet was more sporadic in nature than long-lived. The non-equilibrium chemical and isotopic compositions of the carbonates preserved in the martian meteorite ALH84001 are direct evidence of ancient secondary minerals that have not undergone significant diagenesis or stabilization processes typical of long-lived aqueous systems on Earth. Thus secondary minerals and sediments on Mars may primarily record the characteristics of the aqueous environment in which they formed without being significantly overprinted by subsequent diagenetic processes during burial.

  19. Polycyclic aromatic hydrocarbons (PAHs) in Antarctic Martian meteorites, carbonaceous chondrites, and polar ice.

    PubMed

    Becker, L; Glavin, D P; Bada, J L

    1997-01-01

    Recent analyses of the carbonate globules present in the Martian meteorite ALH84001 have detected polycyclic aromatic hydrocarbons (PAHs) at the ppm level (McKay et al., 1996). The distribution of PAHs observed in ALH84001 was interpreted as being inconsistent with a terrestrial origin and were claimed to be indigenous to the meteorite, perhaps derived from an ancient martian biota. We have examined PAHs in the Antarctic shergottite EETA79001, which is also considered to be from Mars, as well as several Antarctic carbonaceous chondrites. We have found that many of the same PAHs detected in the ALH84001 carbonate globules are present in Antarctic carbonaceous chondrites and in both the matrix and carbonate (druse) component of EETA79001. We also investigated PAHs in polar ice and found that carbonate is an effective scavenger of PAHs in ice meltwater. Moreover, the distribution of PAHs in the carbonate extract of Antarctic Allan Hills ice is remarkably similar to that found in both EETA79001 and ALH84001. The reported presence of L-amino acids of apparent terrestrial origin in the EETA79001 druse material (McDonald and Bada, 1995) suggests that this meteorite is contaminated with terrestrial organics probably derived from Antarctic ice meltwater that had percolated through the meteorite. Our data suggests that the PAHs observed in both ALH84001 and EETA79001 are derived from either the exogenous delivery of organics to Mars or extraterrestrial and terrestrial PAHs present in the ice meltwater or, more likely, from a mixture of these sources. It would appear that PAHs are not useful biomarkers in the search for extinct or extant life on Mars. PMID:11541466

  20. Polycyclic aromatic hydrocarbons (PAHs) in Antarctic Martian meteorites, carbonaceous chondrites, and polar ice

    SciTech Connect

    Becker, L. |; Glavin, D.P.; Bada, J.L.

    1997-01-01

    Recent analyses of the carbonate globules present in the Martian meteorite ALH84001 have detected polycyclic aromatic hydrocarbons (PAHs) at the ppm level. The distribution of PAHs observed in ALH84001 was interpreted as being inconsistent with a terrestrial origin and were claimed to be indigenous to the meteorite, perhaps derived from an ancient martian biota. We have examined PAHs in the Antarctic shergottite EETA79001, which is also considered to be from Mars, as well as several Antarctic carbonaceous chondrites. We have found that many of the same PAHs detected in the ALH84001 carbonate globules are present in Antarctic carbonaceous chondrites and in both the matrix and carbonate (druse) component of EETA79001. We also investigated PAHs in polar ice and found that carbonate is an effective scavenger of PAHs in ice meltwater. Moreover, the distribution of PAHs in the carbonate extract of Antarctic Allan Hills ice is remarkably similar to that found in both EETA79001 and ALH84001. The reported presence of L-amino acids of apparent terrestrial origin in the EETA79001 druse material suggests that this meteorite is contaminated with terrestrial organics probably derived from Antarctic ice meltwater that had percolated through the meteorite. Our data suggests that the PAHs observed in both ALH84001 and EETA79001 are derived from either the exogenous delivery of organics to Mars or extraterrestrial and terrestrial PAHs present in the ice meltwater or, more likely, from a mixture of these sources. It would appear that PAHs are not useful biomarkers in the search for extinct or extant life on Mars. 33 refs., 3 figs., 1 tab.

  1. Analysis of Siderite Thermal Decomposition by Differential Scanning Calorimetry

    NASA Technical Reports Server (NTRS)

    Bell, M. S.; Lin, I.-C.; McKay, D. S.

    2000-01-01

    Characterization of carbonate devolitilization has important implications for atmospheric interactions and climatic effects related to large meteorite impacts in platform sediments. On a smaller scale, meteorites contain carbonates which have witnessed shock metamorphic events and may record pressure/temperature histories of impact(s). ALH84001 meteorite contains zoned Ca-Mg-Fe-carbonates which formed on Mars. Magnetite crystals are found in the rims and cores of these carbonates and some are associated with void spaces leading to the suggestion by Brearley et al. that the crystals were produced by thermal decomposition of the carbonate at high temperature, possibly by incipient shock melting or devolitilization. Golden et al. recently synthesized spherical Mg-Fe-Ca-carbonates from solution under mild hydrothermal conditions that have similar carbonate compositional zoning to those of ALH84001. They have shown experimental evidence that the carbonate-sulfide-magnetite assemblage in ALH84001 can result from a multistep inorganic process involving heating possibly due to shock events. Experimental shock studies on calcium carbonate prove its stability to approx. 60 GPa, well in excess of the approx. 45 GPa peak pressures indicated by other shock features in ALH84001. In addition, Raman spectroscopy of carbonate globules in ALH84001 indicates no presence of CaO and MgO. Such oxide phases should be found associated with the magnetites in voids if these magnetites are high temperature shock products, the voids resulting from devolitilization of CO2 from calcium or magnesium carbonate. However, if the starting material was siderite (FeCO3), thermal breakdown of the ALH84001 carbonate at 470 C would produce iron oxide + CO2. As no documentation of shock effects in siderite exists, we have begun shock experiments to determine whether or not magnetite is produced by the decomposition of siderite within the < 45GPa pressure window and by the resultant thermal pulse to approx

  2. Organic Carbon Exists in Mars Meteorites: where is it on the Martian Surface?

    NASA Astrophysics Data System (ADS)

    McKay, David; Clemett, Simon; Gibson, Everett; Thomas-Keprta, Kathie; Wentworth, Susan

    The search for organic carbon on Mars has been a major challenge. The first attempt was the Viking GC-MS in situ experiment which gave inconclusive results at two sites on Mars [1]. After the discovery that the SNC meteorites were from Mars [2], [3-5] reported C isotopic compositional information which suggested a reduced C component present in the Martian meteorites. [6 7] reported the presence of reduced C components (i.e., polycyclic aromatic hydrocarbons) associated with the carbonate globules in ALH84001. Jull et al. [8] noted in Nakhla there was an acid insoluble C component present with more than 75% of its C lacking any 14 C, which is modern-day terrestrial carbon. This C fraction was believed to be either indigenous martian or ancient meteoritic carbon. Fisk et al. [9, 10] have shown textural evidence along with C-enriched areas within fractures in Nakhla and ALH84001. Westall et al. [11] have shown the presence of a large irregular fragment of organic material completely embedded within a chip of ALH84001. Interior samples from the Nakhla SNC made available by the British Museum of Natural His-tory, were analyzed. Petrographic examination [12] of Nakhla showed evidence of fractures ( 0.5 m wide) filled with dark brown to black dendritic material with characteristics similar to those observed by [10]. Iddingsite is also present along fractures in olivine. Fracture filling and dendritic material was examined by SEM-EDX, TEM-EDX, Focused Electron Beam mi-croscopy, Laser Raman Spectroscopy, Nano-SIMS Ion Micro-probe, and Stepped-Combustion Static Mass Spectrometry. Observations from the first three techniques are discussed in [12 and 13]. Nano-SIMS Ion Microprobe studies of the C-bearing fractures, containing the optically dark dendritic material, show direct correlation between C- and CN- abundances. Ion abun-dances for epoxy are distinct from those of the dendritic material[12] . Laser Raman Spectrometry was utilized to examine the optically dark dendritic

  3. Organic Carbon Exists in Mars Meteorites: where is it on the Martian Surface?

    NASA Astrophysics Data System (ADS)

    McKay, David; Clemett, Simon; Gibson, Everett; Thomas-Keprta, Kathie; Wentworth, Susan

    The search for organic carbon on Mars has been a major challenge. The first attempt was the Viking GC-MS in situ experiment which gave inconclusive results at two sites on Mars [1]. After the discovery that the SNC meteorites were from Mars [2], [3-5] reported C isotopic compositional information which suggested a reduced C component present in the Martian meteorites. [6 7] reported the presence of reduced C components (i.e., polycyclic aromatic hydrocarbons) associated with the carbonate globules in ALH84001. Jull et al. [8] noted in Nakhla there was an acid insoluble C component present with more than 75% of its C lacking any 14 C, which is modern-day terrestrial carbon. This C fraction was believed to be either indigenous martian or ancient meteoritic carbon. Fisk et al. [9, 10] have shown textural evidence along with C-enriched areas within fractures in Nakhla and ALH84001. Westall et al. [11] have shown the presence of a large irregular fragment of organic material completely embedded within a chip of ALH84001. Interior samples from the Nakhla SNC made available by the British Museum of Natural His-tory, were analyzed. Petrographic examination [12] of Nakhla showed evidence of fractures ( 0.5 m wide) filled with dark brown to black dendritic material with characteristics similar to those observed by [10]. Iddingsite is also present along fractures in olivine. Fracture filling and dendritic material was examined by SEM-EDX, TEM-EDX, Focused Electron Beam mi-croscopy, Laser Raman Spectroscopy, Nano-SIMS Ion Micro-probe, and Stepped-Combustion Static Mass Spectrometry. Observations from the first three techniques are discussed in [12 and 13]. Nano-SIMS Ion Microprobe studies of the C-bearing fractures, containing the optically dark dendritic material, show direct correlation between C- and CN- abundances. Ion abun-dances for epoxy are distinct from those of the dendritic material[12] . Laser Raman Spectrometry was utilized to examine the optically dark dendritic

  4. Contribution of Organic Material to the Stable Isotope Composition of Some Terrestrial Carbonates as Analogs for Martian Processes

    NASA Technical Reports Server (NTRS)

    Socki, Richard A.; Gibson, Everett K., Jr.; Bissada, K. K.

    2005-01-01

    Understanding the isotopic geochemistry of terrestrial carbonate formation is essential to understanding the evolution of the Martian atmosphere, hydrosphere, and potential biosphere. Carbonate minerals, in particular, are important secondary minerals for interpreting past aqueous environments, as illustrated by the carbonates present in ALH84001 [1]. Models for the history of Mars suggest that the planet was warmer, wetter, and possessed a greater atmospheric pressure within the first billion years as compared to present conditions [2],[3],[4], and likely had an active hydrologic cycle. Morse and Marion [5] point out that associated with this hydrologic cycle would be the active chemical weathering of silicate minerals and thus consumption of atmospheric CO2 and deposition of carbonate and silica. It is during this warmer and wetter period of Martian history that surface and/or near-surface conditions would be most favorable for harboring possible microbiological life. Carbonates within ALH84001 offer evidence that fluids were present at 3.9 Gy on Mars [6]. A more through understanding of the effects of aqueous weathering and the potential contribution of organic compounds on the isotopic composition of Martian carbonate minerals can be gained by studying some terrestrial occurrences of carbonate rocks.

  5. Carbonates in the Martian meteorite Allan Hills 84001 formed at 18 ± 4 °C in a near-surface aqueous environment

    PubMed Central

    Halevy, Itay; Fischer, Woodward W.; Eiler, John M.

    2011-01-01

    Despite evidence for liquid water at the surface of Mars during the Noachian epoch, the temperature of early aqueous environments has been impossible to establish, raising questions of whether the surface of Mars was ever warmer than today. We address this problem by determining the precipitation temperature of secondary carbonate minerals preserved in the oldest known sample of Mars’ crust—the approximately 4.1 billion-year-old meteorite Allan Hills 84001 (ALH84001). The formation environment of these carbonates, which are constrained to be slightly younger than the crystallization age of the rock (i.e., 3.9 to 4.0 billion years), has been poorly understood, hindering insight into the hydrologic and carbon cycles of earliest Mars. Using “clumped” isotope thermometry we find that the carbonates in ALH84001 precipitated at a temperature of approximately 18 °C, with water and carbon dioxide derived from the ancient Martian atmosphere. Furthermore, covarying carbonate carbon and oxygen isotope ratios are constrained to have formed at constant, low temperatures, pointing to deposition from a gradually evaporating, subsurface water body—likely a shallow aquifer (meters to tens of meters below the surface). Despite the mild temperatures, the apparently ephemeral nature of water in this environment leaves open the question of its habitability. PMID:21969543

  6. Carbonates in the Martian meteorite Allan Hills 84001 formed at 18 +/- 4 degrees C in a near-surface aqueous environment.

    PubMed

    Halevy, Itay; Fischer, Woodward W; Eiler, John M

    2011-10-11

    Despite evidence for liquid water at the surface of Mars during the Noachian epoch, the temperature of early aqueous environments has been impossible to establish, raising questions of whether the surface of Mars was ever warmer than today. We address this problem by determining the precipitation temperature of secondary carbonate minerals preserved in the oldest known sample of Mars' crust--the approximately 4.1 billion-year-old meteorite Allan Hills 84001 (ALH84001). The formation environment of these carbonates, which are constrained to be slightly younger than the crystallization age of the rock (i.e., 3.9 to 4.0 billion years), has been poorly understood, hindering insight into the hydrologic and carbon cycles of earliest Mars. Using "clumped" isotope thermometry we find that the carbonates in ALH84001 precipitated at a temperature of approximately 18 °C, with water and carbon dioxide derived from the ancient Martian atmosphere. Furthermore, covarying carbonate carbon and oxygen isotope ratios are constrained to have formed at constant, low temperatures, pointing to deposition from a gradually evaporating, subsurface water body--likely a shallow aquifer (meters to tens of meters below the surface). Despite the mild temperatures, the apparently ephemeral nature of water in this environment leaves open the question of its habitability. PMID:21969543

  7. My favorite Martians: NASA uncovers evidence of ancient life on Mars.

    PubMed

    Dasch, P; Kross, J

    1996-01-01

    The possibility of life on Mars is explored through the recently found meteorite ALH84001. Thought to have left Mars 16 million years ago, the meteorite was found on an Antarctic ice shelf in 1984. Carbonate globules were found containing microfossils and unusual mineral compounds. NASA researchers believe they have found single-celled fossils resembling nanobacteria fossils found on Earth, but caution that much more research is required. PMID:11539593

  8. Nature of Reduced Carbon in Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Gibson, Everett K., Jr.; McKay, D. S.; Thomas-Keprta, K. L.; Clemett, S. J.; White, L. M.

    2012-01-01

    Martian meteorites provide important information on the nature of reduced carbon components present on Mars throughout its history. The first in situ analyses for carbon on the surface of Mars by the Viking landers yielded disappointing results. With the recognition of Martian meteorites on Earth, investigations have shown carbon-bearing phases exist on Mars. Studies have yielded presence of reduced carbon, carbonates and inferred graphitic carbon phases. Samples ranging in age from the first approximately 4 Ga of Mars history [e.g. ALH84001] to nakhlites with a crystallization age of 1.3 Ga [e.g. Nakhla] with aqueous alteration processes occurring 0.5-0.7 Ga after crystallizaton. Shergottites demonstrate formation ages around 165-500 Ma with younger aqueous alterations events. Only a limited number of the Martian meteorites do not show evidence of significance terrestrial alterations. Selected areas within ALH84001, Nakhla, Yamato 000593 and possibly Tissint are suitable for study of their indigenous reduced carbon bearing phases. Nakhla possesses discrete, well-defined carbonaceous phases present within iddingsite alteration zones. Based upon both isotopic measurements and analysis of Nakhla's organic phases the presence of pre-terrestrial organics is now recognized. The reduced carbon-bearing phases appear to have been deposited during preterrestrial aqueous alteration events that produced clays. In addition, the microcrystalline layers of Nakhla's iddingsite have discrete units of salt crystals suggestive of evaporation processes. While we can only speculate on the origin of these unique carbonaceous structures, we note that the significance of such observations is that it may allow us to understand the role of Martian carbon as seen in the Martian meteorites with obvious implications for astrobiology and the pre-biotic evolution of Mars. In any case, our observations strongly suggest that reduced organic carbon exists as micrometer- size, discrete structures

  9. The History of Allan Hills 84001 Revised: Multiple Shock Events

    NASA Technical Reports Server (NTRS)

    Treiman, Allan H.

    1998-01-01

    The geologic history of Martian meteorite Allan Hills (ALH) 84001 is more complex than previously recognized, with evidence for four or five crater-forming impacts onto Mars. This history of repeated deformation and shock metamorphism appears to weaken some arguments that have been offered for and against the hypothesis of ancient Martian life in ALH 84001. Allan Hills 84001 formed originally from basaltic magma. Its first impact event (I1) is inferred from the deformation (D1) that produced the granular-textured bands ("crush zones") that transect the original igneous fabric. Deformation D1 is characterized by intense shear and may represent excavation or rebound flow of rock beneath a large impact crater. An intense thermal metamorphism followed D1 and may be related to it. The next impact (I2) produced fractures, (Fr2) in which carbonate "pancakes" were deposited and produced feldspathic glass from some of the igneous feldspars and silica. After I2, carbonate pancakes and globules were deposited in Fr2 fractures and replaced feldspathic glass and possibly crystalline silicates. Next, feldspars, feldspathic glass, and possibly some carbonates were mobilized and melted in the third impact (I3). Microfaulting, intense fracturing, and shear are also associated with 13. In the fourth impact (I4), the rock was fractured and deformed without significant heating, which permitted remnant magnetization directions to vary across fracture surfaces. Finally, ALH 84001 was ejected from Mars in event I5, which could be identical to I4. This history of multiple impacts is consistent with the photogeology of the Martian highlands and may help resolve some apparent contradictions among recent results on ALH 84001. For example, the submicron rounded magnetite grains in the carbonate globules could be contemporaneous with carbonate deposition, whereas the elongate magnetite grains, epitaxial on carbonates, could be ascribed to vapor-phase deposition during I3.

  10. Life on Mars, Where do we stand after seven years of investigations.

    NASA Astrophysics Data System (ADS)

    Gibson, E.

    2003-04-01

    The question "Is there life on Mars?" is one of the most challenging questions for the scientific community to answer. Until documented samples are returned to Earth from Mars by space probes, the only samples available for study are twenty-six undocumented, randomly selected Martian samples delivered to Earth. Martian meteorites offer a unique opportunity to study near-surface samples from Mars. Martian meteorites of widely differing ages (ALH84001 - crystallization age of 4.5 Gy. with 3.9 Gy. old carbonates; Nakhla D crystallization age of 1.3 Gy. and clays of possibly 600-700 Ma. years age; and Shergotty D 165 Ma. crystallization age) contain evidence of water produced alteration products (hydrates, clays, sulfates, carbonates, halites, etc.). ALH84001 and Nakhla has been shown to contain indigenous reduced carbon compounds with isotopic compositions which are not products of terrestrial contaminants. Unique magnetite biomarkers are found within the ALH84001 low-temperature carbonate globules and display six unique properties of magnetites produced by the reference MV-1 magnetosome bacteria. Recently, the three-dimensional morphologies of the magnetites from both MV-1 magnetosome bacteria and the "biogenic" population of magnetites within the carbonates of ALH84001 have been show to be crystallographically equivalent. The determination that the properties of both MV-1 and ALH84001 magnetites are essentially identical provides further support for our interpretation that these Martian magnetites were produced by similar biogenic processes on Mars. To date, all of the models presented utilizing thermal decomposition of iron-rich carbonates to produce magnetites within ALH84001's carbonates fail to produce the unique properties of the biogenic magnetites. In addition, morphological structures are present within the three Martian meteorites which are identical to fossilized bacteria. Despite more than seven years of extensive research by the scientific community, the

  11. Origin of Carbonate in Martian Meteorite Allan Hills 84001

    NASA Astrophysics Data System (ADS)

    Scott, E. R. D.; Krot, A. N.

    1998-01-01

    A significant argument advanced by McKay et al., in favor of a biogenic origin of the carbonates in ALH 84001 was that abiogenic origins - both low and high temperature - appeared to be less plausible. However, subsequent shock studies have suggested that impact heating may have modified carbonates. We inferred that plagioclase glass and rare silica grains formed from impact melts, and Raman spectroscopy confirmed that plagiociase had been melted at greater than 1200C, suggesting shock pressures exceeded 35-45 GPa. Morphological similarities between grains of plagioclase glass and irregularly shaped carbonates in fractures and the occurrence of intermixed grains in fractures suggested that carbonates may also have been shock heated so that a CO2-rich fluid was injected into cooler-fractured pyroxene during shock decompression causing crystallization in seconds.

  12. Negative δ 18O values in Allan Hills 84001 carbonate: Possible evidence for water precipitation on mars

    NASA Astrophysics Data System (ADS)

    Holland, G.; Saxton, J. M.; Lyon, I. C.; Turner, G.

    2005-03-01

    The Martian meteorite ALH84001 contains ˜1% by weight of carbonate formed by secondary processes on the Martian surface or in the shallow subsurface. The major form of this carbonate is chemically and isotopically zoned rosettes which have been well documented elsewhere. This study concentrates upon carbonate regions ˜200 μm across which possess previously unobserved magnesium rich inner cores, interpreted here as rosette fragments, surrounded by a later stage cement containing rare Ca-rich carbonates (up to Ca 81Mg 07Fe 04Mn 07) intimately associated with feldspar. High spatial resolution ion probe analyses of Ca-rich carbonate surrounding rosette fragments have δ 18O V-SMOW values as low as -10 ‰. These values are not compatible with deposition from a global Martian atmosphere invoked to explain ALH84001 rosettes. The range of δ 18O values are also incompatible with a fluid that has equilibrated with the Martian crust at high temperature or from remobilisation of carbonate of rosette isotopic composition. At Martian atmospheric temperatures, the small CO 2(gas)-CO 2(ice) fractionation makes meteoric CO 2 an unlikely source for -10 ‰ carbonates. In contrast, closed system Rayleigh fractionation of H 2O can generate δ 18O H2O -30 ‰, as observed at high latitudes on Earth. We suggest that atmospheric transport and precipitation of H 2O in a similar fashion to that on Earth provides a source of suitably 18O depleted water for generation of carbonate with δ 18O V-SMOW = -10 ‰.

  13. Ion Microprobe Measurements of Carbon Isotopes in Martian Phosphates: Insights into the Martian Mantle

    NASA Astrophysics Data System (ADS)

    Goreva, J. S.; Leshin, L. A.; Guan, Y.

    2003-03-01

    In-situ measurements of C in the phosphates from meteorites Los Angeles, Zagami, QUE94201 and ALH84001 predict isotopically light martian magmatic C, heavier than previous estimates yet significantly lighter than the terrestrial value.

  14. Rubidium-Strontium Formation Age of Allan Hills 84001 Carbonates

    NASA Technical Reports Server (NTRS)

    Borg, L. E.; Nyquist, L. E.; Shih, C.-Y.; Weismann, H.; Reese, Y.; Connelly, J. N.

    1998-01-01

    Our preferred age for the formation of carbonates in the martian meteorite ALH 84001 is 3.90 plus or minus 0.04 Ga for Lambda (Rubidium 87) equals 0.01402 Ga (exp -1), or 3.85 plus or minus 0.04 Ga for Lambda (Rubidium 87) = 0.0142 Ga(exponent -1). This age is determined by a three-point Rb-Sr isochron defined by leachates of high-graded carbonate-rich material. Major cation and especially phosphorous analyses of the leachates permit contributions from igneous whitlockite to be recognized for low-acidity leachates, and the corresponding data are omitted from the isochron. Data for the two highest acidity leachates plot close to the preferred isochron, but are omitted because we believe they contain contributions leached from the pyroxene substrate on which most of the carbonates are found. Nevertheless, the isochron age for all five highest-acidity leachates is 3.94 plus or minus 0.04 Ga, and is within error of the age obtained for the more restricted data set. All leachates used to define the isochron have major cation compositions that are singular to those obtained by microprobe analyses of the carbonate rosettes and are consistent with progressive digestion of the carbonates according to their composition. The age thus obtained for the carbonates is about 600 m.y. younger than the crystalization age of ALH 84001 determined by Sm-Nd analyses but is within error limits of the age of impact metamorphism inferred from the Rb-Sr and Ar-Ar systematics of silicates. which yield ages of 3.85 plus or minus 0.05 Ga and 4.05- 3.80 Ga to 4.3-3.8 Ga, respectively. Similarities between the carbonate crystallization age and the age of impact metamorphism as determined by Ar-Ar and Rb-Sr suggest that the carbonate formation is impact-related. Nevertheless, both high and low- temperature scenarios for the origin of the carbonates are possible.

  15. Detection of carbonates in dust shells around evolved stars.

    PubMed

    Kemper, F; Jäger, C; Waters, L B F M; Henning, Th; Molster, F J; Barlow, M J; Lim, T; de Koter, A

    2002-01-17

    Carbonates on large Solar System bodies like Earth and Mars (the latter represented by the meteorite ALH84001) form through the weathering of silicates in a watery (CO3)2- solution. The presence of carbonates in interplanetary dust particles and asteroids (again, represented by meteorites) is not completely understood, but has been attributed to aqueous alteration on a large parent body, which was subsequently shattered into smaller pieces. Despite efforts, the presence of carbonates outside the Solar System has hitherto not been established. Here we report the discovery of the carbonates calcite and dolomite in the dust shells of evolved stars, where the conditions are too primitive for the formation of large parent bodies with liquid water. These carbonates, therefore, are not formed by aqueous alteration, but perhaps through processes on the surfaces of dust or ice grains or gas phase condensation. The presence of carbonates which did not form by aqueous alteration suggests that some of the carbonates found in Solar System bodies no longer provide direct evidence that liquid water was present on large parent bodies early in the history of the Solar System. PMID:11797000

  16. The provenance and formation of reduced carbon phases on Mars from the study of Martian meteorites.

    NASA Astrophysics Data System (ADS)

    Steele, A.; McCubbin, F. M.; Fries, M.

    2015-12-01

    Organic carbon compounds are essential building blocks of terrestrial life, so the occurrence and origin (biotic or abiotic) of organic compounds on Mars is of great significance. Indeed, the question of Martian organic matter is among the highest priority targets for robotic spacecraft missions in the next decade includ- ing the Mars Science Laboratory and Mars 2020. Sev- eral Martian meteorites contain organic carbon (i.e., macromolecular reduced carbon-rich material, not nec- essarily related to biota), but there is little agreement on its origins. Initial hypotheses for the origin of this organic carbon included: terrestrial contamination; chondritic meteoritic input; thermal decomposition of Martian carbonate minerals; direct precipitation from cooling aqueous fluids; and the remains of ancient Martian biota. We report on results from the analysis of 14 martian meteorites and show the distribution of organic phases throughout the samples analyzed. We will present formation scearios for each of the types of organic matter discovered. These studies when combined show 4 possible pools of reduced carbon on Mars. 1) impact generated graphite in the Tissint meteorite, 2) secondary hydrothermal generated graphite in ALH 84001, 3) primary igneous reduced carbon in 12 Martian meteorites associated with spinel inclusions in olivine and pyroxene 4) and potentially primary hydrothermally formed organic carbon / nitrogen containing organic species in the maskelynite phases of the Tissint meteorite. These studies show that Mars has produced reduced carbon / organic carbon via several mechanisms and reveal that the building blocks of life, if not life itself, are present on Mars.

  17. Carbonate Globules in Columbia River Basalt The Search for Life in Terrestrial Subsurface Environments as Possible Martian Analogs

    NASA Technical Reports Server (NTRS)

    Starke, V.; McKay, D. S.; Wentworth, S. J.; ThomasKeprta, K. L.

    2002-01-01

    Basalts from the Columbia River (CRB) Plateau contain minor amounts of carbonates of unknown origins. We have examined the petrology and chemistry of the CRB carbonates to elucidate the modes of formation. This study is directly relevant to meteorites and future samples returned from Mars. Additional information is contained in the original extended abstract.

  18. Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars.

    PubMed

    Shaheen, R; Abramian, A; Horn, J; Dominguez, G; Sullivan, R; Thiemens, Mark H

    2010-11-23

    The debate of life on Mars centers around the source of the globular, micrometer-sized mineral carbonates in the ALH84001 meteorite; consequently, the identification of Martian processes that form carbonates is critical. This paper reports a previously undescribed carbonate formation process that occurs on Earth and, likely, on Mars. We identified micrometer-sized carbonates in terrestrial aerosols that possess excess (17)O (0.4-3.9‰). The unique O-isotopic composition mechanistically describes the atmospheric heterogeneous chemical reaction on aerosol surfaces. Concomitant laboratory experiments define the transfer of ozone isotopic anomaly to carbonates via hydrogen peroxide formation when O(3) reacts with surface adsorbed water. This previously unidentified chemical reaction scenario provides an explanation for production of the isotopically anomalous carbonates found in the SNC (shergottites, nakhlaites, chassignites) Martian meteorites and terrestrial atmospheric carbonates. The anomalous hydrogen peroxide formed on the aerosol surfaces may transfer its O-isotopic signature to the water reservoir, thus producing mass independently fractionated secondary mineral evaporites. The formation of peroxide via heterogeneous chemistry on aerosol surfaces also reveals a previously undescribed oxidative process of utility in understanding ozone and oxygen chemistry, both on Mars and Earth. PMID:21059939

  19. Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars

    PubMed Central

    Shaheen, R.; Abramian, A.; Horn, J.; Dominguez, G.; Sullivan, R.; Thiemens, Mark H.

    2010-01-01

    The debate of life on Mars centers around the source of the globular, micrometer-sized mineral carbonates in the ALH84001 meteorite; consequently, the identification of Martian processes that form carbonates is critical. This paper reports a previously undescribed carbonate formation process that occurs on Earth and, likely, on Mars. We identified micrometer-sized carbonates in terrestrial aerosols that possess excess 17O (0.4–3.9‰). The unique O-isotopic composition mechanistically describes the atmospheric heterogeneous chemical reaction on aerosol surfaces. Concomitant laboratory experiments define the transfer of ozone isotopic anomaly to carbonates via hydrogen peroxide formation when O3 reacts with surface adsorbed water. This previously unidentified chemical reaction scenario provides an explanation for production of the isotopically anomalous carbonates found in the SNC (shergottites, nakhlaites, chassignites) Martian meteorites and terrestrial atmospheric carbonates. The anomalous hydrogen peroxide formed on the aerosol surfaces may transfer its O-isotopic signature to the water reservoir, thus producing mass independently fractionated secondary mineral evaporites. The formation of peroxide via heterogeneous chemistry on aerosol surfaces also reveals a previously undescribed oxidative process of utility in understanding ozone and oxygen chemistry, both on Mars and Earth. PMID:21059939

  20. Isotope Variations in Terrestrial Carbonates and Thermal Springs as Biomarkers: Analogs for Martian Processes

    NASA Technical Reports Server (NTRS)

    Socki, Richard A.; Gibson, Everett K., Jr.; Bissada, K. K.

    2006-01-01

    Stable isotope measurements of carbonate minerals contained within ALH84001 [1] suggest that fluids were present at 3.9 Gy on Mars [2, 3, 4, 5]. Both oxygen and carbon isotopes provide independent means of deciphering paleoenvironmental conditions at the time of carbonate mineral precipitation. In terrestrial carbonate rocks oxygen isotopes not only indicate the paleotemperature of the precipitating fluid, but also provide clues to environmental conditions that affected the fluid chemistry. Carbon isotopes, on the other hand, can indicate the presence or absence of organic compounds during precipitation (i.e. biogenically vs. thermogenically-generated methane), thus serving as a potential biomarker. We have undertaken a study of micro scale stable isotope variations measured in some terrestrial carbonates and the influence of organic compounds associated with the formation of these carbonates. Preliminary results indicate that isotope variations occur within narrow and discrete intervals, providing clues to paleoenvironmental conditions that include both biological and non-biological activity. These results carry implications for deciphering Martian isotope data and therefore potential biological prospecting on the planet Mars. Recently, Fourier Transform Spectrometer observations have detected methane occurring in the Martian atmosphere [6] that could be attributed to a possible biogenic source. Indeed, Mars Express has detected the presence of methane in the Martian atmosphere [7], with evidence indicating that methane abundances are greatest above those basins with high water concentrations.

  1. Microbial extremophiles in evolutionary aspect

    NASA Astrophysics Data System (ADS)

    Pikuta, Elena V.; Hoover, Richard B.

    2007-09-01

    The microflora of the cryosphere of planet Earth provides the best analogs for life forms that might be found in the permafrost or polar ice caps of Mars, near the surface of the cometary nuclei, or in the liquid water beneath the ice crusts of icy moons of Jupiter and Saturn. For astrobiology the focus on the study alkaliphilic microorganisms was enhanced by the findings of abundant carbonates and carbonate globules rimmed with possibly biogenic magnetites in association with the putative microfossils in the ALH84001 meteorite. Although the ALH84001 "nanofossils" were too small and simple to be unambiguously recognized as biogenic, they stimulated Astrobiology research and studies of microbial extremophiles and biomarkers in ancient rocks and meteorites. Recent studies of CI and CM carbonaceous meteorites have resulted in the detection of the well-preserved mineralized remains of coccoidal and filamentous microorganisms in cyanobacterial mats. Energy Dispersive X-ray Analysis has shown anomalous biogenic element ratios clearly indicating they are not recent biological contaminants. This paper reviews microbial extremophiles in context of their significance to Astrobiology and the evolution of life. Extremophilic microorganisms on Earth are models for life that might endure high radiation environments in the ice near the surface of comets or on the icy moons of Jupiter and Saturn and in the seafloor deep beneath the icy crusts of Europa and Enceladus.

  2. Microbial Extremophiles in Evolutionary Aspect

    NASA Technical Reports Server (NTRS)

    Pikuta, Elena V.; Hoover, Richard B.

    2007-01-01

    The microflora of the cryosphere of planet Earth provides the best analogs for life forms that might be found in the permafrost or polar ice caps of Mars, near the surface of the cometary nuclei, or in the liquid water beneath the ice crusts of icy moons of Jupiter and Saturn. For astrobiology the focus on the study alkaliphilic microorganisms was enhanced by the findings of abundant carbonates and carbonate globules rimmed with possibly biogenic magnetites in association with the putative microfossils in the ALH84001 meteorite. Although the ALH84001 "nanofossils" were to small and simple to be unambiguously recognized as biogenic, they stimulated Astrobiology research and studies of microbial extremophiles and biomarkers in ancient rocks and meteorites. Recent studies of CI and CM carbonaceous meteorites have resulted in the detection of the well-preserved mineralized remains of coccoidal and" filamentous microorganisms in cyanobacterial mats. Energy Dispersive X-ray Analysis has shown anomalous biogenic element ratios clearly indicating they are not recent biological contaminants. This paper reviews microbial extremophiles in context of their significance to Astrobiology and the evolution of life. Extremophilic microorganisms on Earth are models for life that might endure high radiation environments in the ice near the surface of comets or on the icy moons of Jupiter and Saturn and in the seafloor deep beneath the icy crusts of Europa and Enceladus.

  3. Formation of magnetite and iron-rich carbonates by thermophilic iron-reducing bacteria

    SciTech Connect

    Zhang, C.; Liu, S.; Roh, Y.; Cole, D.; Phelps, T.; Vali, H.; Kirschvink, J.L.; Onsttot, T.; McKay, D.

    1997-06-01

    Laboratory experiments were performed to study the formation of iron minerals by a thermophilic (45 to 75 C) fermentative iron-reducing bacterial culture (TOR39) obtained from the deep subsurface. Using amorphous Fe(III) oxyhydroxide as an electron acceptor and glucose as an electron donor, TOR39 produced magnetite and iron-rich carbonates at conditions consistent, on a thermodynamic basis, with Eh ({minus}200 mV to {minus}415 mV) and pH (6.2 to 7.7) values determined for these experiments. Analyses of the precipitating solid phases by X-ray diffraction showed that the starting amorphous Fe(III) oxyhydroxide was nearly completely converted to magnetite and Fe-rich carbonate after 20 days of incubation. Increasing bicarbonate concentration in the chemical milieu resulted in increased proportions of siderite relative to magnetite and the addition of MgCl{sub 2} caused the formation of magnesium-rich carbonate in addition to siderite. The results suggest that the TOR39 bacterial culture may have the capacity to form magnetite and iron-rich carbonates in a variety of geochemical conditions. These results may have significant implications for studying the past biogenic activities in the Martian meteorite ALH84001.

  4. Formation of magnetite and iron-rich carbonates by thermophilic iron-reducing bacteria

    NASA Astrophysics Data System (ADS)

    Zhang, Chuanlun; Vali, Hojatollah; Liu, Shi; Roh, Yul; Cole, Dave; Kirschvink, Joseph L.; Onstott, Tullis C.; McKay, David S.; Phelps, Tommy J.

    1997-07-01

    Laboratory experiments were performed to study the formation of iron minerals by a thermophilic (45 - 75 degree(s)C) fermentative iron-reducing bacterial culture (TOR39) obtained from the deep subsurface. Using amorphous Fe(III) oxyhydroxide as an electron acceptor and glucose as an electron donor, TOR39 produced magnetite and iron-rich carbonates at conditions consistent, on a thermodynamic basis, with Eh (-200 mV to -415 mV) and pH (6.2 to 7.7) values determined for these experiments. Analyses of the precipitating solid phases by X-ray diffraction showed that the starting amorphous Fe(III) oxyhydroxide was nearly completely converted to magnetite and Fe-rich carbonate after 20 days of incubation. Increasing bicarbonate concentration in the chemical milieu resulted in increased proportions of siderite relative to magnetite and the addition of MgCl2 caused the formation of magnesium-rich carbonate in addition to siderite. The results suggest that the TOR39 bacterial culture may have the capacity to form magnetite and iron-rich carbonates in a variety of geochemical conditions. These results may have significant implications for studying the past biogenic activities in the Martian meteorite ALH84001.

  5. Radial systems of dark globules

    SciTech Connect

    Gyul'budagyn, A.L.

    1986-03-01

    The author gives examples of radial systems consisting of dark globules and ''elephant trunks''. Besides already known systems, which contain hot stars at their center, data are given on three radial systems of a new kind, at the center of which there are stars of spectral types later than B. Data are given on 32 globules of radial systems of the association Cep OB2. On the basis of the observational data, it is concluded that at least some of the isolated Bok globules derive from elephant trunks and dark globules forming radial systems around hot stars. It is also suggested that the two molecular clouds situated near the Rosette nebula and possessing velocities differing by ca 20 km/sec from the velocity of the nebula could have been ejected in opposite directions from the center of the nebula. One of these clouds consists of dark globules forming the radial system of the Rosette nebula.

  6. Searching for traces of life associated with carbonates in martian meteorites

    NASA Astrophysics Data System (ADS)

    Lepot, K.; Kearsley, A. T.; Chater, R. J.; McPhail, D. J.

    Martian meteorites provide an obvious starting point for the search for evidence of life on Mars. Peculiar structures shown by electron microscopy of fragments from the Antarctic meteorite ALH84001 have been reported to demonstrate shapes and a size distribution similar to those of cultured terrestrial nanobacteria. However, the association of these putative fossil forms with bacteria is only morphological, and no traces of undisputed biological organic matter have yet been demonstrated in close association with these structures. Similar, and larger, apparent microbial fossils have been found within samples of the Martian basaltic shergottite meteorite Los Angeles 001 (LA 001). Here they are associated with calcium carbonate deposition, known from isotopic studies to be terrestrial in origin, and also with silica-bearing globular encrustations, reminiscent of biofilm. This association is typical of bacterially-mediated mineral precipitation, which may occur directly on bacterial cells or on their surroundings. We have used analytical electron microscopy to locate and document possible bacterial shapes in LA 001, prior to Focussed Ion Beam cross-sectioning and Secondary Ion Mass Spectrometry of the internal sections revealed. We intend to compare the morphology and composition of internal structures to those of bacteria preserved in terrestrial carbonate stromatolites, siliceous sinters and abiotic precipitates, in order to determine whether major element compositional variation, isotopic and trace element partitioning can be used to reliably fingerprint bacterial activity as responsible for the meteoritic structures.

  7. Anomalous Diffusion in Fractal Globules

    NASA Astrophysics Data System (ADS)

    Tamm, M. V.; Nazarov, L. I.; Gavrilov, A. A.; Chertovich, A. V.

    2015-05-01

    The fractal globule state is a popular model for describing chromatin packing in eukaryotic nuclei. Here we provide a scaling theory and dissipative particle dynamics computer simulation for the thermal motion of monomers in the fractal globule state. Simulations starting from different entanglement-free initial states show good convergence which provides evidence supporting the existence of a unique metastable fractal globule state. We show monomer motion in this state to be subdiffusive described by ⟨X2(t )⟩˜tαF with αF close to 0.4. This result is in good agreement with existing experimental data on the chromatin dynamics, which makes an additional argument in support of the fractal globule model of chromatin packing.

  8. Chains of Magnetite Crystals in the Meteorite ALH84001: Evidence of Biological Origin

    NASA Technical Reports Server (NTRS)

    Friedmann, E. I.; Wierzchos, J.; Ascaso, C.; Winklhofer, M.

    2001-01-01

    The presence of magnetite crystal chains, missing evidence for their biological origin, as well as five morphological characteristics incompatible with a nonbiological origin are demonstrated by high-power stereo backscattered scanning electron microscopy. Additional information is contained in the original extended abstract.

  9. Discovery of Biological Structures in the Tissint Mars Meteorite

    NASA Astrophysics Data System (ADS)

    Wallis, J.; Wickramasinghe, N. C.; Wallis, Daryl; Miyake, Nori; Wallis, Max; Di Gregorio, Barry; Mufti, Shirwan Al

    2012-03-01

    Preliminary SEM/EDAX studies of the Tissint meteorite shows projections of interior spherical globules rich in C and O. Such concentrations of carbonaceous material in a matrix of mineral grains poses a mystery if biological processes are excluded. They are consistent with remnants of biological structures, thus supporting earlier similar claims for the Mars meteorite ALH84001..

  10. Experimental Shock Decomposition of Siderite to Magnetite

    NASA Technical Reports Server (NTRS)

    Bell, M. S.; Golden, D. C.; Zolensky, M. E.

    2005-01-01

    The debate about fossil life on Mars includes the origin of magnetites of specific sizes and habits in the siderite-rich portions of the carbonate spheres in ALH 84001 [1,2]. Specifically [2] were able to demonstrate that inorganic synthesis of these compositionally zoned spheres from aqueous solutions of variable ion-concentrations is possible. They further demonstrated the formation of magnetite from siderite upon heating at 550 C under a Mars-like CO2-rich atmosphere according to 3FeCO3 = Fe3O4 + 2CO2 + CO [3] and they postulated that the carbonates in ALH 84001 were heated to these temperatures by some shock event. The average shock pressure for ALH 84001, substantially based on the refractive index of diaplectic feldspar glasses [3,4,5] is some 35-40 GPa and associated temperatures are some 300-400 C [4]. However, some of the feldspar is melted [5], requiring local deviations from this average as high as 45-50 GPa. Indeed, [5] observes the carbonates in ALH 84001 to be melted locally, requiring pressures in excess of 60 GPa and temperatures > 600 C. Combining these shock studies with the above inorganic synthesis of zoned carbonates it seems possible to produce the ALH 84001 magnetites by the shock-induced decomposition of siderite.

  11. Isotopic evidence for a terrestrial source of organic compounds found in martian meteorites Allan Hills 84001 and Elephant Moraine 79001.

    PubMed

    Jull, A J; Courtney, C; Jeffrey, D A; Beck, J W

    1998-01-16

    Stepped-heating experiments on martian meteorites Allan Hills 84001 (ALH84001) and Elephant Moraine 79001 (EETA79001) revealed low-temperature (200 to 430 degrees Celsius) fractions with a carbon isotopic composition delta13C between -22 and -33 per mil and a carbon-14 content that is 40 to 60 percent of that of modern terrestrial carbon, consistent with a terrestrial origin for most of the organic material. Intermediate-temperature (400 to 600 degrees Celsius) carbonate-rich fractions of ALH84001 have delta13C of +32 to +40 per mil with a low carbon-14 content, consistent with an extraterrestrial origin, whereas some of the carbonate fraction of EETA79001 is terrestrial. In addition, ALH84001 contains a small preterrestrial carbon component of unknown origin that combusts at intermediate temperatures. This component is likely a residual acid-insoluble carbonate or a more refractory organic phase. PMID:9430584

  12. The challenge of remote exploration for extraterrestrial fossil life

    NASA Astrophysics Data System (ADS)

    Benoit, Paul H.; Taunton, Anne E.

    1997-07-01

    The discovery of possible fossils of nanobacteria in a meteorite from Mars is both an exciting development and a considerably challenge for future work. The meteorite bearing the possible fossils, ALH84001, has been on Earth for over ten thousand years, and thus the possibility that the `fossils' are terrestrial contamination must be considered. We suggest that the only way to fully resolve the issue of possible martian life is to study directly- sampled pieces of Mars, either using in situ instrumentation or via sample return. The small size of the possible fossils, and their relatively low abundance in bulk rock samples make in situ analysis difficult and indirect. We suggest that addressing the issue of ancient life on Mars will require sample return, probably assisted by in situ screening by landers/rovers. Our study of ALH84001 confirms the observation of McKay et al. of the existence of `fossils' in ALH84001, and we find that they are highly abundant on all the carbonate nodules we examined. Examination of lunar meteorites and two other martian meteorites, with terrestrial and laboratory histories very similar to that of ALH84001, shows that nano-`fossils' are absent, suggesting that the features in ALH84001 are probably not terrestrial contamination.

  13. Biomarkers in Carbonate Thermal Springs: Implications for Mars

    NASA Technical Reports Server (NTRS)

    Allen, C. C.; Kivett, S. J.; McKay, D. S.

    1998-01-01

    Evidence of possible relict biogenic activity has been reported in carbonate inclusions within martian meteorite ALH 84001. The initial evidence included ovoid and elongated forms 50 - 500 nanometers in length, morphologically similar to but significantly smaller than many terrestrial microbes. More recently, thin structures resembling the remains of organic biofilms have been reported in the same meteorite. Carbonates have also been discussed in the context of Mars sample return missions. Thermal spring deposits have often been cited as prime locations for exobiological exploration. By analogy to Earth, specialized microbes may have existed in the heated, mineralized waters, and precipitates of carbonate and/or silica from these waters may have trapped and preserved evidence of life. Since the geological interactions that produce thermal springs can be recognized in orbital imagery, directed searches for microfossils in such deposits are deemed possible. We are engaged in a study of the signatures produced by contemporary biogenic activity (biomarkers) in carbonate thermal springs. We are examining the microbes that live in such environments and the preservation of microbial forms, biofilms, and petrographic fabrics indicative of life in thermal spring mineral deposits. This work is part of a much more extensive study to refine the appropriate tools, techniques, and approaches to seek evidence of life in a range of planetary samples. A deeper understanding of biological signatures will prepare us for the detailed search for life on Mars and eventually on other planets. Overall. the study of biomarkers in rocks and soils will provide insight into the evolution of life because such signatures are a record of how life interacts with its environment, how it adapts to changing conditions, and how life can influence geology and climate.

  14. Olivine in Martian Meteorite Allan Hills 84001: Evidence for a High-Temperature Origin and Implications for Signs of Life

    NASA Technical Reports Server (NTRS)

    Shearer, C. K.; Leshin, L. A.; Adcock, C. T.

    1999-01-01

    Olivine from Martian meteorite Allan Hills (ALH) 84001 occurs as clusters within orthopyroxene adjacent to fractures containing disrupted carbonate globules and feldspathic shock glass. The inclusions are irregular in shape and range in size from approx. 40 microns to submicrometer. Some of the inclusions are elongate and boudinage-like. The olivine grains are in sharp contact with the enclosing orthopyroxene and often contain small inclusions of chromite The olivine exhibits a very limited range of composition from Fo(sub 65) to Fo(sub 66) (n = 25). The delta(sup 18)O values of the olivine and orthopyroxene analyzed by ion microprobe range from +4.3 to +5.3% and are indistinguishable from each other within analytical uncertainty. The mineral chemistries, O-isotopic data, and textural relationships indicate that the olivine inclusions were produced at a temperature greater than 800 C. It is unlikely that the olivines formed during the same event that gave rise to the carbonates in ALH 84001, which have more elevated and variable delta(sup 18)O values, and were probably formed from fluids that were not in isotopic equilibrium with the orthopyroxene or olivine The reactions most likely instrumental in the formation of olivine could be either the dehydration of hydrous silicates that formed during carbonate precipitation or the reduction of orthopyroxene and spinel If the olivine was formed by either reaction during a postcarbonate beating event, the implications are profound with regards to the interpretations of McKay et al. Due to the low diffusion rates in carbonates, this rapid, high-temperature event would have resulted in the preservation of the fine-scale carbonate zoning' while partially devolatilizing select carbonate compositions on a submicrometer scale. This may have resulted in the formation of the minute magnetite grains that McKay et al attributed to biogenic activity.

  15. Observation and Analysis of In Situ Carbonaceous Matter in Naklha. Part 2

    NASA Technical Reports Server (NTRS)

    Gibson, E. K., Jr.; Clemett, S. J.; Thomas-Kerpta, K. L.; McKay, D. S.; Wentworth, S. J.; Robert, F.; Verchovsky, A. B.; Wright, I. P.; Pillinger, C. T.; Rice, T.; VanLeer, B.

    2006-01-01

    The search for indigenous carbon components on Mars has been a challenge. The first attempt was the Viking GC-MS in situ experiment which gave inconclusive results at two sites on Mars [1]. After the discovery that the SNC meteorites were from Mars [2], [3-5] reported C isotopic compositional information which suggested a reduced C component present in the martian meteorites. [6 & 7] reported the presence of reduced C components (i.e., polycyclic aromatic hydrocarbons) associated with the carbonate globules in ALH84001. Jull et al. [8] noted in Nakhla there was an acid insoluble C component present with more than 75% of its C lacking any C-14, which is modern-day carbon. This C fraction was believed to be either indigenous martian or ancient meteoritic carbon. Fisk et al. [9, 10] have shown textural evidence along with C-enriched areas within fractures in Nakhla and ALH84001. To further understand the nature of possible indigenous reduced C components, we have carried out a variety of measurements on martian meteorites. For this presentation we will discuss only the Nakhla results. Interior samples from the Nakhla SNC meteorite, recently made available by the British Museum of Natural History, were analyzed. Petrographic examination [11, McKay et al., this volume] of Nakhla showed evidence of fractures (approx.0.5 micron wide) filled with dark brown to black dendritic material [Fig. 1] with characteristics similar to those observed by [10]. Iddingsite is also present along fractures in olivine. Fracture filling and dendritic material was examined by SEM-EDX, TEM-EDX, Focused Electron Beam microscopy, Laser Raman Spectroscopy, Nano-SIMS Ion Micro-probe, and Stepped-Combustion Static Mass Spectrometry.

  16. Organic Compounds in Martian Meteorites May Be Terrestrial Contaminants

    NASA Astrophysics Data System (ADS)

    Jull, A. J. T.

    1998-02-01

    In 1996, David McKay and coworkers reported evidence suggesting the possibility of fossils in the Martian meteorite ALH84001 (see PSRD article "Life on Mars"). This work has stimulated much discussion as to the nature and origin of organic material in ALH84001, another Martian meteorite, EET79001, and other Martian meteorites in general. My colleagues C. Courtney, D. A. Jeffrey, and J. W. Beck and I have been investigating the origin of the organic compounds by measuring the abundances of the isotopes of carbon (C) using accelerator mass spectrometry (AMS). Important clues to the origin of the organic material can be obtained from the amounts of 14C (frequently nicknamed radiocarbon) and the relative amounts of 13C and 12C. Our analyses indicate that at least 80% of the organic material in ALH84001 is from Earth, not Mars, casting doubt on the hypothesis the meteorite contains a record of fossil life on Mars.

  17. Presolar Organic Globules in Astromaterials

    NASA Technical Reports Server (NTRS)

    Nakamura-Messenger, K.; Messenger, S.; Keller, L. P.; Clemett, S. J.

    2012-01-01

    Presolar grains were identified in meteorite residues 20 years ago based on their exotic isotopic compositions [1]. Their study has provide new insights into stellar evolution and the first view of the original building blocks of the solar system. Organic matter in meteorites and IDPs is highly enriched in D/H and N-15/N-14 at micron scales, possibly due to presolar organic grains [2-4]. These anomalies are ascribed to the partial preservation of presolar cold molecular cloud material. Identifying the carriers of these anomalies and elucidating their physical and chemical properties may give new views of interstellar chemistry and better understanding of the original components of the protosolar disk. However, identifying the carriers has been hampered by their small size and the inability to chemically isolate them. Thanks to major advances in nano-scale analytical techniques and advanced sample preparation, we were able to show that in the Tagish Lake meteorite, the principle carriers of these isotopic anomalies are sub-microns, hollow organic globules [5]. The organic globules likely formed by photochemical processing of organic ices in a cold molecular cloud or the outermost regions of the protosolar disk [5]. Organic globules with similar physical, chemical, and isotopic properties are also recently found from Bells CM2 carbonaceous chondrite, in IDPs [6] and in the comet Wild-2 samples returned by Stardust [7]. These results support the view that microscopic organic grains were widespread constituents of the protoplanetary disk. Their exotic isotopic compositions trace their origins to the outermost portions of the protosolar disk or a presolar cold molecular cloud.

  18. Lunar and Planetary Science XXXV: Astrobiology

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The presentations in this session are: 1. A Prototype Life Detection Chip 2. The Geology of Atlantis Basin, Mars, and Its Astrobiological Interest 3. Collecting Bacteria Together with Aerosols in the Martian Atmosphere by the FOELDIX Experimental Instrument Developed with a Nutrient Detector Pattern: Model Measurements of Effectivity 4. 2D and 3D X-ray Imaging of Microorganisms in Meteorites Using Complexity Analysis to Distinguish Field Images of Stromatoloids from Surrounding Rock Matrix in 3.45 Ga Strelley Pool Chert, Western Australia 4. Characterization of Two Isolates from Andean Lakes in Bolivia Short Time Scale Evolution of Microbiolites in Rapidly Receding Altiplanic Lakes: Learning How to Recognize Changing Signatures of Life 5. The Effect of Salts on Electrospray Ionization of Amino Acids in the Negative Mode 6. Determination of Aromatic Ring Number Using Multi-Channel Deep UV Native Fluorescence 7. Microbial D/H Fractionation in Extraterrestrial Materials: Application to Micrometeorites and Mars 8. Carbon Isotope Characteristics of Spring-fed Iron-precipitating Microbial Mats 9. Amino Acid Survival Under Ambient Martian Surface UV Lighting Extraction of Organic Molecules from Terrestrial Material: Quantitative Yields from Heat and Water Extractions 10. Laboratory Detection and Analysis of Organic Compounds in Rocks Using HPLC and XRD Methods 11. Thermal Decomposition of Siderite-Pyrite Assemblages: Implications for Sulfide Mineralogy in Martian Meteorite ALH84001 Carbonate Globules 12. Determination of the Three-Dimensional Morphology of ALH84001 and Biogenic MV-1 Magnetite: Comparison of Results from Electron Tomography and Classical Transmission Electron Microscopy 13. On the Possibility of a Crypto-Biotic Crust on Mars Based on Northern and Southern Ringed Polar Dune Spots 14. Comparative Planetology of the Terrestrial Inner Planets: Implications for Astrobiology 15. A Possible Europa Exobiology 16. A Possible Biogeochemical Model for Titan

  19. Workshop on the Issue Martian Meteorites: Where do we Stand and Where are we Going?

    NASA Technical Reports Server (NTRS)

    1998-01-01

    The presentations in this workshop discuss the composition of Martian meteorites. Many of the talks were on a specific meteorite, i.e., Allan Hills 84001 (ALH84001). The discovery earlier of carbonates in ALH84001 lead some researchers to suggest that there was evidence of martian life. Other possible explanations for this phenomena are given. Other papers discuss methods to sterilize martian samples, the existence of water on Mars, the facilities of the Meteorite Processing Laboratory at Johnson Space Center, comparative analyses of geologic processes and the gathering of meteorites.

  20. A nitrogen and argon stable isotope study of Allan Hills 84001: implications for the evolution of the Martian atmosphere.

    PubMed

    Grady, M M; Wright, I P; Pillinger, C T

    1998-07-01

    The abundances and isotopic compositions of N and Ar have been measured by stepped combustion of the Allan Hills 84001 (ALH 84001) Martian orthopyroxenite. Material described as shocked is N-poor ([N] approximately 0.34 ppm; delta 15N approximately +23%); although during stepped combustion, 15N-enriched N (delta 15N approximately +143%) is released in a narrow temperature interval between 700 degrees C and 800 degrees C (along with 13C-enriched C (delta 13C approximately +19%) and 40Ar). Cosmogenic species are found to be negligible at this temperature; thus, the isotopically heavy component is identified, in part, as Martian atmospheric gas trapped relatively recently in the history of ALH84001. The N and Ar data show that ALH84001 contains species from the Martian lithosphere, a component interpreted as ancient trapped atmosphere (in addition to the modern atmospheric species), and excess 40Ar from K decay. Deconvolution of radiogenic 40Ar from other Ar components, on the basis of end-member 36Ar/14N and 40Ar/36Ar ratios, has enabled calculation of a K-Ar age for ALH 84001 as 3.5-4.6 Ga, depending on assumed K abundance. If the component believed to be Martian palaeoatmosphere was introduced to ALH 84001 at the time the K-Ar age was set, then the composition of the atmosphere at this time is constrained to: delta 15N > or = +200%, 40Ar/36Ar < or = 3000 and 36Ar/14N > or = 17 x 10(-5). In terms of the petrogenetic history of the meteorite, ALH 84001 crystallised soon after differentiation of the planet, may have been shocked and thermally metamorphosed in an early period of bombardment, and then subjected to a second event. This later process did not reset the K-Ar system but perhaps was responsible for introducing (recent) atmospheric gases into ALH 84001; and it might mark the time at which ALH 84001 suffered fluid alteration resulting in the formation of the plagioclase and carbonate mineral assemblages. PMID:11543078

  1. On the stability of fractal globules.

    PubMed

    Schram, Raoul D; Barkema, Gerard T; Schiessel, Helmut

    2013-06-14

    The fractal globule, a self-similar compact polymer conformation where the chain is spatially segregated on all length scales, has been proposed to result from a sudden polymer collapse. This state has gained renewed interest as one of the prime candidates for the non-entangled states of DNA molecules inside cell nuclei. Here, we present Monte Carlo simulations of collapsing polymers. We find through studying polymers of lengths between 500 and 8000 that a chain collapses into a globule, which is neither fractal, nor as entangled as an equilibrium globule. To demonstrate that the non-fractalness of the conformation is not just the result of the collapse dynamics, we study in addition the dynamics of polymers that start from fractal globule configurations. Also in this case the chain moves quickly to the weakly entangled globule where the polymer is well mixed. After a much longer time the chain entangles reach its equilibrium conformation, the molten globule. We find that the fractal globule is a highly unstable conformation that only exists in the presence of extra constraints such as cross-links. PMID:23781815

  2. Magnetic Field Maps of Quiescent BOK Globules

    NASA Astrophysics Data System (ADS)

    Kane, Brian D.; Clemens, Dan P.

    1994-12-01

    We present magnetic field maps of 12 starless Bok Globules. Maps were constructed from polarimetric V-band images taken with a computer-controlled CCD camera with a fast shutter and a bidirectional charge-shifting capability. The linear polarization of stars in the globule field has been determined by repeated use of imaging through a polaroid filter, shifting the charge up by many times the stellar PSF, reimaging through an orthogonal polaroid filter, then shifting the charge back down to its starting point. Between one and five CCD fields-of-view were necessary to map each globule, and up to 50 stars in each FOV had detectable polarizations. This globule sample exhibits a variety of magnetic field patterns, including uniform fields with dispersion less than 10(deg) , overlapping fields with two distinct directions, and cometary extensions.

  3. Structural energetics of the molten globule state.

    PubMed

    Haynie, D T; Freire, E

    1993-06-01

    Certain partly ordered protein conformations, commonly called "molten globule states," are widely believed to represent protein folding intermediates. Recent structural studies of molten globule states of different proteins have revealed features which appear to be general in scope. The emerging consensus is that these partly ordered forms exhibit a high content of secondary structure, considerable compactness, nonspecific tertiary structure, and significant structural flexibility. These characteristics may be used to define a general state of protein folding called "the molten globule state," which is structurally and thermodynamically distinct from both the native state and the denatured state. Despite extensive knowledge of structural features of a few molten globule states, a cogent thermodynamic argument for their stability has not yet been advanced. The prevailing opinion of the last decade was that there is little or no enthalpy difference or heat capacity difference between the molten globule state and the unfolded state. This view, however, appears to be at variance with the existing database of protein structural energetics and with recent estimates of the energetics of denaturation of alpha-lactalbumin, cytochrome c, apomyoglobin, and T4 lysozyme. We discuss these four proteins at length. The results of structural studies, together with the existing thermodynamic values for fundamental interactions in proteins, provide the foundation for a structural thermodynamic framework which can account for the observed behavior of molten globule states. Within this framework, we analyze the physical basis for both the high stability of several molten globule states and the low probability of other potential folding intermediates. Additionally, we consider, in terms of reduced enthalpy changes and disrupted cooperative interactions, the thermodynamic basis for the apparent absence of a thermally induced, cooperative unfolding transition for some molten globule

  4. [Meteoritics and mineralogy on possible ancient Martian life].

    PubMed

    Tsuchiyama, A

    1996-12-01

    Possible relic biogenic activity in martian meteorite ALH84001 was proposed by McKay et al. (Science, 273, 924-930, 1996). This ancient meteorite of 4.5 billion years old contains abundant carbonates as secondary minerals precipitated from a fluid on the martian surface. They showed the following lines of evidence for the ancient life; (1) unique mineral compositions and biominerals, (2) polycyclic aromatic hydrocarbons (PAHs) in association with the carbonates, and (3) unique structures and morphologies typical of nanobacteria or microfossils. This review is divided into two parts; one is on the martian meteorites in general and ALH84001, which has many features unlike other martian meteorites, and the other is on mineralogical (biomineralogical) and geochemical features of the carbonates and microfossil-like structures. There is little doubt that ALH84001 is from Mars as well as eleven other SNC meteorites. However, the mineralogical and biomineralogical evidence for martian bacteria given by McKay et al. (1996) is controversial, and could be formed by non-biogenic processes. Thus, further study of ALH84001 and other martian meteorites is required. We also need to consider the future Mars mission especially sample return mission. PMID:11540347

  5. High-Resolution Multiple Sulfur Isotope Studies of Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Mojzsis, S. J.

    2000-01-01

    Sensitive, high resolution measurements of S-32, S-31, and S-34 in individual pyrite grains in martian meteorite ALH84001 by an in situ ion microprobe multi-collection technique reveal mass-independent anomalies in Delta.S-33 (Delta.S-33 = delta.S-33 - 0.516delta.S-34) in addition to the lowest 634S found in an extraterrestrial material. Low delta.S-34 values in two pyrite grains intimately associated with carbonate in ALH84001 can be explained by the sensitivity of sulfur to fractionations in the geologic environment. Anomalies in Delta.S-33 recorded in ALH84001 pyrites probably formed by gas-phase reactions in the early martian atmosphere (>4 Ga). The discovery of clearly resolvable Delta-S33 anomalies in 2 of 12 ALH84001 pyrites analyzed in their petrographic context in thin section, is considered strong evidence for crust-atmosphere exchange and the global cycling of volatile sulfur species on early Mars. These results corroborate previous measurements by Farquhar and co-workers who used a different technique that measures that bulk Delta.S-33 values of martian meteorites. These independent techniques, and their results, suggest that sulfur affected by mass-independent fractionation is common on Mars.

  6. About iron globules formed at cooling of iron-contained plasma

    NASA Astrophysics Data System (ADS)

    Bulina, N. V.; Gromyko, A. I.; Bondarenko, G. V.; Marachevsky, A. V.; Chekanova, L. A.; Prokof'ev, D. E.; Churilov, G. N.

    2006-12-01

    This paper is devoted to the investigation of iron globules that are formed during cooling of the iron-carbon-helium plasma and as a result of destruction of a natural ball lightning. Scanning electron microscopy, X-ray fluorescence, X-ray diffraction, and ferromagnetic resonance investigations were carried out. The magnetization values of the samplers were determined.

  7. ORIGIN OF ORGANIC GLOBULES IN METEORITES: LABORATORY SIMULATION USING AROMATIC HYDROCARBONS

    SciTech Connect

    Saito, Midori; Kimura, Yuki

    2009-10-01

    Analogs of organic hollow globules, which have been found in carbonaceous chondrite meteorites and interplanetary dust particles, were synthesized in our laboratory from benzene and anthracene using plasma. Our results suggest that organic globules could be made from aromatic rings in circumstellar envelopes around evolved stars. The hollow interior could be formed by coagulation of vacancies, formed by electronic excitation and/or knock-out of carbon atoms following irradiation by plasma particles such as protons and He{sup +} ions. This experimental result suggests that organic globules are possibly the final products in the evolution of carbonaceous matter from acetylene and benzene to polycyclic aromatic hydrocarbons in ejecta gas from evolved stars.

  8. Organic Globules from the Cold Far Reaches of the Proto-Solar Disk

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    2007-01-01

    Keiko Nakamura-Messenger and colleagues at the NASA Johnson Space Center in Houston, Texas, studied minute globules of organic material in the Taglish Lake carbonaceous chondrite. This meteorite was collected soon after it fell, so is fresh and likely to be uncontaminated with terrestrial organic compounds. Using microanalytical techniques the NASA team found that the globules had hydrogen and nitrogen isotopic compositions consistent with chemical reactions at strikingly frigid temperatures, only 10 to 20 K (-253 to -263 degrees C). Temperatures that low occur in cold, interstellar molecular clouds like the one that collapsed to form the Solar System or in the outermost part of the disk surrounding the Sun when it was forming. These organic globules might represent the type of prebiotic carbon compounds that were delivered to young Earth.

  9. Carbonates in Martian Meteorites - A Reappraisal

    NASA Astrophysics Data System (ADS)

    Grady, M. M.; Wright, I. P.; Douglas, C.; Pillinger, C. T.

    1995-09-01

    The occurrence of carbonates in martian meteorites was first established after acid dissolution and stepped combustion analyses of whole-rock Nakhla [1]. The release of CO2 after a 24 hr. reaction with 100% H3PO4 at 25 degrees C was taken to imply that the carbonate mineral present was calcite, a proposal subsequently confirmed by petrographic examination [2]. The isotopic composition of the carbon comprising the calcite was enriched in 13C (isotopically heavy) with delta^(l3)C ~ +12 per mil. An extended period of acid attack, also at 25 degrees C, released small quantities of even more 13C-enriched CO2 (delta^(13)C ~ +49 per mil), but the isotopic data were considered uncertain, and thus little significance was attached to the result, beyond the suggestion that some carbonate was perhaps dolomite or iron-bearing. Now, however, following the analysis of Fe-Mg-rich carbonates in ALH 84001 [3-5], it is apparent that previously-reported data might underestimate the abundance and delta^(13)C of carbonates in SNCs [6], and that a much higher proportion might occur as siderite or dolomite end-members. Iron- and magnesium-rich carbonates are only partially attacked at 25 degrees C, even after extended exposure to H3PO4 [7]. Given that the delta^(13)C of carbonates in SNCs has been used to deduce both environmental conditions on Mars [4, 6], and the evolution of the martian atmosphere [8], it is desirable that correct delta^(l3)c values are known. We have undertaken a reappraisal of the chemical and isotopic composition of carbonates in martian meteorites, by a programme of high resolution stepped combustion analyses and high temperature (75 degrees C) acid dissolution . Carbonates in most martian meteorites are extremely fine-grained. and therefore not easv to identify by traditional optical microscopic methods; it is not possible to determine readily the mineralogical composition of the grains. Comparison of combustion data from SNCs with that from pure materials allows

  10. Dark Globule in IC 1396 (IRAC)

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site] Click on image for larger view of inset

    NASA's Spitzer Space Telescope image of a glowing stellar nursery provides a spectacular contrast to the opaque cloud seen in visible light (inset). The Elephant's Trunk Nebula is an elongated dark globule within the emission nebula IC 1396 in the constellation of Cepheus. Located at a distance of 2,450 light-years, the globule is a condensation of dense gas that is barely surviving the strong ionizing radiation from a nearby massive star. The globule is being compressed by the surrounding ionized gas. The dark globule is seen in silhouette at visible-light wavelengths, backlit by the illumination of a bright star located to the left of the field of view.

    The Spitzer Space Telescope pierces through the obscuration to reveal the birth of new protostars, or embryonic stars, and previously unseen young stars. The infrared image was obtained by Spitzer's infrared array camera. The image is a four-color composite of invisible light, showing emissions from wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8.0 microns (red). The filamentary appearance of the globule results from the sculpting effects of competing physical processes. The winds from a massive star, located to the left of the image, produce a dense circular rim comprising the 'head' of the globule and a swept-back tail of gas.

    A pair of young stars (LkHa 349 and LkHa 349c) that formed from the dense gas has cleared a spherical cavity within the globule head. While one of these stars is significantly fainter than the other in the visible-light image, they are of comparable brightness in the infrared Spitzer image. This implies the presence of a thick and dusty disc around LkHa 349c. Such circumstellar discs are the precursors of planetary systems. They are much thicker in the early stages of stellar formation when the placental planet-forming material (gas and dust) is still

  11. Evidence for Ancient Martian Life

    NASA Technical Reports Server (NTRS)

    Gibson, Everett K., Jr.

    1999-01-01

    Three SNC meteorites ranging in age from 4.5 Ga. to 1.3 Ga. to 165 m.y. contain features suggestive, of past biogenic activity on Mars. Because we do not know what past martian life looks like or its physical or chemical properties, the only tools or criteria which the scientific community have to evaluate evidence of past life is to use evidence for early life on earth. There are features within ALH8400 I's carbonate globules and the pre-terrestrial aqueous alteration phases of Nakhla and Shergotty which have been interpreted as possible evidence for past life on early Mars. Eight criteria have been established for the recognition of past life within terrestrial geologic samples. They are: (a) geologic context; (b) sample's age and stratigraphic location (c) cellular morphology; (d) colonies; (e) biominerals; (f) stable isotope patterns unique to biology; (g) organic biomarkers; (h) indigenous features to the sample. For general acceptance of past life, essentially most or all of these criteria must be met. Studies have shown conclusively that the reduced carbon components in ALH84001 and Nakhla are indigenous to the meteorites and are not terrestrial contaminants Based on carbon isotopic compositions and mineralogical morphologies, there is no question or disagreement that the carbonate globules or embedded magnetites in ALH84001 and the pre-terrestrial aqueous alteration products in Nakhla and Shergotty were formed on Mars. Possible microfossil structures and some reduced carbon components in the carbonates and pre-terrestrial aqueous alteration products are, therefore, almost certainly indigenous, but other possible evidence for life (e.g. amino acids) may be a result of terrestrial contamination Our hypothesis of possible early life on Mars was presented in August 1996. Today, we believe it stands stronger than when originally presented. To date, no fatal strikes have been made to any of our original four lines of evidence. While details of the hypothesis are

  12. Formation and Evolution of Cometary Globules

    NASA Astrophysics Data System (ADS)

    Lefloch, Bertrand

    1994-06-01

    We have conducted a detailed study both numerical and analytical of Cometary Globules (CGs), related to their possible mechanism of formation. CGs are small dense clouds commonly found in the vicinity of O--B stars in HII regions; they consist of a dense head, surrounded by a bright rim, prolonged by a diffuse tail. Recent surveys have shown that CGs are active sites of star formation. One of the models advanced to explain the formation and the evolution of CGs is the ``Radiation-Driven Implosion''(RDI): the UV flux of the O--B association ionizes the external layers of the cloud. The ionised gas expands freely into the interstellar medium while an ionization front preceded by a shock propagates into the cloud. We have built a 2-D radiative hydrodynamical code based on the piece-wise linear method. The equations of radiative transfer are solved using the "on-the-spot" approximation. The equation of state P = P(ρ,x), where x is the ionised fraction per atom, couples the equations of hydrodynamics and radiation. Gravity is neglected. We have shown that photo-ionisation alone can account for the formation and evolution of CGs. For physical parameters typical of H II regions, RDI is a two-stage process: a brief collapse phase (~105 yrs, 10% of the cloud life) followed by a transient phase during which the cloud undergoes a series of radial expansions and re-compressions, leading to the commonly observed cometary phase. The collapse phase is characterised by a double kinematic emission component, the second component being associated with shocked gas. In the cometary phase, the globule is in a quasi-hydrostatic equilibrium and has no remarkable spectroscopic signature. This phase lasts a few 105 to 106 yrs. The results of numerical simulations were confirmed by a simple analytic model and extended to the case of a non-thermal support. It appears that small- and large-scale instabilities, Rayleigh-Taylor like, similar to the surface corrugations observed in CGs of the

  13. Tracing the evolutionary stage of Bok globules: CCS and NH3

    NASA Astrophysics Data System (ADS)

    Marka, C.; Schreyer, K.; Launhardt, R.; Semenov, D. A.; Henning, Th.

    2012-01-01

    Aims: We investigate a previously proposed correlation between the chemical properties and the physical evolutionary stage of isolated low-mass star-forming regions. The NNH3/NCCS abundance ratio has been proposed to be a potentially useful indicator of the evolutionary stage of cloud cores, and we study its applicability for isolated Bok globules. Methods: We searched for CCS(21-10) emission in 42 Bok globules both with and without signs of current star formation. A set of NH3 measurements was compiled from measurements available in the literature and from our own observations. The abundance ratio of both molecules is discussed with respect to the evolutionary stage of the objects and in the context of chemical models. Results: We determine the NNH3/NCCS ratio for 18 Bok globules and find that it is moderately high and roughly similar across all evolutionary stages from starless and prestellar cores towards internally heated cores harboring protostars of Class 0, Class I, or later. We do not find any Bok globules with extremely high CCS abundances analogous to carbon-chain producing regions in dark cloud cores. The observed range of NNH3/NCCS implies that all of the observed Bok globules are in a relatively evolved chemical state. Based on observations obtained with the 100-m telescope of the MPIfR (Max-Planck-Institut für Radioastronomie) at Effelsberg and the 64-m Parkes radio telescope. The Parkes radio telescope is part of the Australia Telescope National Facility which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.

  14. Interactions between milk fat globules and green tea catechins.

    PubMed

    Rashidinejad, Ali; Birch, E John; Everett, David W

    2016-05-15

    The determination of putative chemical interactions between the milk fat globule membrane and green tea catechins provided useful information about the role of milk fat globules (MFGs) in high-fat dairy systems, such as cheese, and containing bioactive compounds, such as tea catechins. Catechins from green tea (125-1,000 ppm), including (+)-catechin, (-)-epigallocatechin gallate, and green tea extract were added to washed MFGs to examine possible interactions. The addition of catechins gave a significant change in the size and ζ-potential of MFGs. The recovery of different catechins from the milk fat globule suspensions was found to vary, suggesting selective association with the milk fat globule membranes. The interactions were further investigated using transmission electron microscopy and Fourier transform infra-red spectroscopy. It is suggested that catechins are localised in association with milk fat globule membrane domains as they contain both hydrophobic and hydrophilic moieties with potential points of molecular interaction. PMID:26775981

  15. The three-dimensional folding of the α-globin gene domain reveals formation of chromatin globules.

    PubMed

    Baù, Davide; Sanyal, Amartya; Lajoie, Bryan R; Capriotti, Emidio; Byron, Meg; Lawrence, Jeanne B; Dekker, Job; Marti-Renom, Marc A

    2011-01-01

    We developed a general approach that combines chromosome conformation capture carbon copy (5C) with the Integrated Modeling Platform (IMP) to generate high-resolution three-dimensional models of chromatin at the megabase scale. We applied this approach to the ENm008 domain on human chromosome 16, containing the α-globin locus, which is expressed in K562 cells and silenced in lymphoblastoid cells (GM12878). The models accurately reproduce the known looping interactions between the α-globin genes and their distal regulatory elements. Further, we find using our approach that the domain folds into a single globular conformation in GM12878 cells, whereas two globules are formed in K562 cells. The central cores of these globules are enriched for transcribed genes, whereas nontranscribed chromatin is more peripheral. We propose that globule formation represents a higher-order folding state related to clustering of transcribed genes around shared transcription machineries, as previously observed by microscopy. PMID:21131981

  16. The Macrostructure of Milk Lipids: The Fat Globules.

    PubMed

    Martini, Mina; Salari, Federica; Altomonte, Iolanda

    2016-05-18

    The aim of this review article is to summarize the information available related to milk fat globules (MFGs) in order to highlight their contribution to the nutritional and technological characteristics of milk and dairy products. The macrostructure of milk lipids is composed of globules made up of triglycerides with different melting points, enveloped by a biological membrane from the mammary epithelial cell. In milks of different animal species, there are different-sized MFGs, ranging from diameters of less than 0.2 μm to a maximum of 15 μm. The average diameter and the number of globules are affected by endogenous, physiological, and exogenous factors. The size of the globules in turn affects the qualitative characteristics of milk and cheese. In addition, the average diameter of the globules and their surface that is exposed to the digestive system affect fat digestibility in different ways. Finally, the components of the MFG membranes have been shown to take part in the secretion process of globules and to have a beneficial effect on human health. In conclusion, by acting on factors influencing the dimensions of the fat globules and by increasing the content of the milk membrane could help adapt milk production to specific consumer targets and improve milk nutritional properties. PMID:24915408

  17. Fractal Globules: A New Approach to Artificial Molecular Machines

    PubMed Central

    Avetisov, Vladik A.; Ivanov, Viktor A.; Meshkov, Dmitry A.; Nechaev, Sergei K.

    2014-01-01

    The over-damped relaxation of elastic networks constructed by contact maps of hierarchically folded fractal (crumpled) polymer globules was investigated in detail. It was found that the relaxation dynamics of an anisotropic fractal globule is very similar to the behavior of biological molecular machines like motor proteins. When it is perturbed, the system quickly relaxes to a low-dimensional manifold, M, with a large basin of attraction and then slowly approaches equilibrium, not escaping M. Taking these properties into account, it is suggested that fractal globules, even those made by synthetic polymers, are artificial molecular machines that can transform perturbations into directed quasimechanical motion along a defined path. PMID:25418305

  18. Fractal globules: a new approach to artificial molecular machines.

    PubMed

    Avetisov, Vladik A; Ivanov, Viktor A; Meshkov, Dmitry A; Nechaev, Sergei K

    2014-11-18

    The over-damped relaxation of elastic networks constructed by contact maps of hierarchically folded fractal (crumpled) polymer globules was investigated in detail. It was found that the relaxation dynamics of an anisotropic fractal globule is very similar to the behavior of biological molecular machines like motor proteins. When it is perturbed, the system quickly relaxes to a low-dimensional manifold, M, with a large basin of attraction and then slowly approaches equilibrium, not escaping M. Taking these properties into account, it is suggested that fractal globules, even those made by synthetic polymers, are artificial molecular machines that can transform perturbations into directed quasimechanical motion along a defined path. PMID:25418305

  19. Magnetosomal matrix: ultrafine structure may template biomineralization of magnetosomes.

    PubMed

    Taylor, A P; Barry, J C

    2004-02-01

    The organic matrix surrounding bullet-shaped, cubo-octahedral, D-shaped, irregular arrowhead-shaped, and truncated hexa-octahedral magnetosomes was analysed in a variety of uncultured magnetotactic bacteria. The matrix was examined using low- (80 kV) and intermediate- (400 kV) voltage TEM. It encapsulated magnetosomes in dehydrated cells, ultraviolet-B-irradiated dehydrated cells and stained resin-embedded fixed cells, so the apparent structure of the matrix does not appear to be an artefact of specimen preparation. High-resolution images revealed lattice fringes in the matrix surrounding magnetite and greigite magnetosomes that were aligned with lattice fringes in the encapsulated magnetosomes. In all except one case, the lattice fringes had widths equal to or twice the width of the corresponding lattice fringes in the magnetosomes. The lattice fringes in the matrix were aligned with the [311], [220], [331], [111] and [391] related lattice planes of magnetite and the [222] lattice plane of greigite. An unidentified material, possibly an iron hydroxide, was detected in two immature magnetosomes containing magnetite. The unidentified phase had a structure similar to that of the matrix as it contained [311], [220] and [111] lattice fringes, which indicates that the matrix acts as a template for the spatially controlled biomineralization of the unidentified phase, which itself transforms into magnetite. The unidentified phase was thus called pre-magnetite. The presence of the magnetosomal matrix explains all of the five properties of the biosignature of the magnetosomal chain proposed previously by Friedmann et al. and supports their claim that some of the magnetite particles in the carbonate globules in the Martian meteorite ALH84001 are biogenic. Two new morphologies of magnetite magnetosomes are also reported here (i.e. tooth-shaped and hexa-octahedral magnetosomes). Tooth-shaped magnetite magnetosomes elongated in the [110] direction are reported, and are distinct

  20. Magnetic field dispersion in the neighbourhood of Bok Globules

    NASA Astrophysics Data System (ADS)

    Rodrigues, C. V.; Magalhães, V. de S.; Vilas-Boas, J. W.; Racca, G.; Pereyra, A.

    2014-08-01

    We performed an observational study of the relation between the interstellar magnetic field alignment and star formation in twenty (20) sky regions containing Bok Globules. The presence of young stellar objects in the globules is verified by a search of infrared sources with spectral energy distribution compatible with a pre main-sequence star. The interstellar magnetic field direction is mapped using optical polarimetry. These maps are used to estimate the dispersion of the interstellar magnetic field direction in each region from a Gaussian fit, σ B . In addition to the Gaussian dispersion, we propose a new parameter, η, to measure the magnetic field alignment that does not rely on any function fitting. Statistical tests show that the dispersion of the magnetic field direction is different in star forming globules relative to quiescent globules. Specifically, the less organised magnetic fields occur in regions having young stellar objects.

  1. Molten globules, entropy-driven conformational change and protein folding.

    PubMed

    Baldwin, Robert L; Rose, George D

    2013-02-01

    The exquisite side chain close-packing in the protein core and at binding interfaces has prompted a conviction that packing selectivity is the primary mechanism for molecular recognition in folding and/or binding reactions. Contrary to this view, molten globule proteins can adopt native topology and bind targets tightly and specifically in the absence of side chain close-packing. The molten globule is a highly dynamic form with native-like secondary structure and a loose protein core that admits solvent. The related (but still controversial) dry molten globule is an expanded form of the native protein with largely intact topology but a tighter protein core that excludes solvent. Neither form retains side chain close-packing, and therefore both structure and function must result from other factors, assuming that the reality of the dry molten globule is accepted. This simplifying realization calls for a re-evaluation of established models. PMID:23237704

  2. No `nanofossils' in martian meteorite

    NASA Astrophysics Data System (ADS)

    Bradley, J. P.; Harvey, R. P.; McSween, H. Y.; Gibson, Everett; Thomas-Keprta, Kathie; Vali, H.

    1997-12-01

    Elongated, segmented forms found on fracture surfaces within the martian meteorite ALH84001 have been proposed to be martian `nanofossils', even though they appear too small to be fossilized bacteria. We have examined similar forms and find that the majority are (non-biological) lamellar growth steps on pyroxene and carbonate crystals. Their segmented surface microstructures are laboratory artefacts resulting from the deposition of conductive heavy-metal coatings.

  3. Sulfur isotopic systematics in alteration assemblages in martian meteorite Allan Hills 84001

    SciTech Connect

    Shearer, C.K.; Layne, G.D.; Papike, J.J.; Spilde, M.N.

    1996-08-01

    ALH84001 is a coarse-grained, clastic orthopyroxenite meteorite related to the SNC meteorite group (shergottites, nakhlites, Chassigny). Superimposed upon the orthopyroxene-dominant igneous mineral assemblage is a hydrothermal signature. This hydrothermal overprint consists of carbonate assemblages occurring in spheroidal aggregates and fine-grained carbonate-sulfide vug-filling. The sulfide in this assemblage has been identified as pyrite, an unusual sulfide in meteorites. Previously, Burgess et al. (1989) reported a bulk {delta} {sup 34}S for a SNC group meteorite (Shergotty) of -0.5 {+-} 1.5%. Here, we report the first martian {delta} {sup 34}S values from individual sulfide grains. Using newly developed ion microprobe techniques, we were able to determine {delta} {sup 34}S of the pyrite in ALH84001 with a 1 {alpha} precision of better than {+-}0.5%. The {delta} {sup 34}S values for the pyrite range from +4.8 to +7.8%. Within the stated uncertainties, the pyrite from ALH84001 exhibits a real variability in {delta} {sup 34}S in this alteration assemblage. In addition, these sulfides are demonstrably enriched in {sup 34}S relative to Canon Diablo troilite and sulfides from most other meteorites. This signature implies that the planetary body represented by ALH 84001 experienced processes capable of fractionating sulphur isotopes and that hydrothermal conditions changed during pyrite precipitation (T, pH, fluid composition, etc.). These new data are not consistent with the pyrite recording either biogenic activity or atmospheric fractionation of sulphur through nonthermal escape mechanisms or oxidation processes. This study also demonstrates the usefulness of ion microprobe measurements of sulphur isotopes in constraining conditions on other planetary bodies.

  4. Field Emission Gun Scanning Electron (FEGSEM) and Transmission Electron (TEM) Microscopy of Phyllosilicates in Martian Meteorites ALH84001, Nakhla, and Shergotty

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Wentworth, Susan J.; McKay, David S.; Gibson, Everett K.

    2000-01-01

    Here we document the occurrence of phyllosilicates and alteration phases in three martian meteorites, suggest formation conditions required for phyllosilicate formation and speculate on the extent of fluid:rock interactions during the past history of Mars.

  5. Two Types of Radial Systems of Dark Globules

    NASA Astrophysics Data System (ADS)

    Gyulbudaghian, A. L.; Mendez, R. A.

    2016-06-01

    We present results of survey of ESO/SRC plates of Southern Hemisphere for discovering new radial systems of dark globules. During the survey 16 new type 1 radial systems and 6 type 2 radial systems were found, it means that the number of known radial systems was almost doubled. In the centers of type 1 radial systems are situated O-B2 type stars, in the centers of type 2 radial systems there are no early type stars. An attempt was done to give interpretation to groups of submm starless condensations as radial systems of dark globules, situated behind thick dark clouds, that is why these globules are seen only in submm wavelengths.

  6. Scaling of a collapsed polymer globule in two dimensions.

    PubMed

    Baiesi, Marco; Orlandini, Enzo; Stella, Attilio L

    2006-02-01

    Extensive Monte Carlo data analysis gives clear evidence that collapsed linear polymers in two dimensions fall in the universality class of athermal, dense self-avoiding walks, as conjectured by Duplantier [Phys. Rev. Lett. 71, 4274 (1993)].10.1103/PhysRevLett.71.4274 However, the boundary of the globule has self-affine roughness and does not determine the anticipated nonzero topological boundary contribution to entropic exponents. Scaling corrections are due to subleading contributions to the partition function corresponding to polymer configurations with one end located on the globule-solvent interface. PMID:16486799

  7. Subfractionation of eyespot apparatuses from the green alga Spermatozopsis similis: isolation and characterization of eyespot globules.

    PubMed

    Renninger, S; Backendorf, E; Kreimer, G

    2001-05-01

    Despite the well-characterized function of the green-algal eyespot apparatus as a combined absorption/reflection screen for the photoreceptor for phototaxis, little is known about the proteins involved in the formation of this complex organelle. We therefore purified the carotenoid-rich lipid globules, which are the most conspicuous component of the eyespot sensu strictu from Spermatozopsis similis Preisig et Melkonian. Electron microscopy and an average carotenoid:chlorophyll ratio of 51, confirmed the high purity of the fraction. The diameter of isolated globules (approx. 112 nm) fell within their in vivo range (90-120 nm). Absorption spectra in aqueous media peaked at 535 nm. The predominant carotenoids were beta/psi-, beta, beta- and delta-carotene. Freeze-fracture studies with cells and whole-mount electron microscopy of isolated globules demonstrated regularly arranged particles at the globule surface. Sodium dodecyl sulfate polyacrylamide gel electrophresis revealed specific enrichment of 10 tightly bound major proteins and several minor proteins with the globules. Proteases were used to analyze their topology and function. Upon treatment with thermolysin, globules were released from a fraction enriched in isolated eyespot apparatuses. Major proteins of these globules, and those treated with thermolysin after isolation, were identical. However, the purified proteins were sensitive to thermolysin, indicating that domains of them are normally hidden in the globule matrix. In contrast, pronase degraded all globule-associated proteins in situ. These globules were not stable and easily fused, whereas thermolysin-treated globules were relatively stable. Lipase did not affect globule stability. These results indicate that the five thermolysin-resistant proteins (apparent Mr values: 56, 52, 32, 29, 27 kDa) are close to the surface and might be crucial for globule stabilization, whereas the thermolysin-accessible proteins are probably involved in globule/globule

  8. Observations of formaldehyde absorption in the region of NGC 2264 and other Bok globules

    NASA Technical Reports Server (NTRS)

    Rickard, L. J.; Palmer, P.; Buhl, D.; Zuckerman, B.

    1977-01-01

    The paper reports observations of 6-cm H2CO absorption over an extended region surrounding the globule in NGC 2264 and toward the globules B68, B72, B133, B134, B227, B238, and B335. The lines observed from the globules are similar to those seen in more extended dark clouds. It is inferred that physical conditions are similar in the two types of region. Negative results for several other globules are reported.

  9. ISO Observations of Starless Bok Globules: Usually No Embedded Stars

    NASA Technical Reports Server (NTRS)

    Clemens, D.; Byrne, A.; Yun, J.; Kane, B.

    1996-01-01

    We have used ISOCAM to search the cores of a sample of small Bok globules previously classified to be mostly starless based on analysis of IRAS data. The ISO observations at 6.75microns (LW2 filter) and 14.5microns (LW3 filter) were sufficiently deep to enable detection of any low-mass hydrogen burning star or young stellar object (YSO) embedded in these globules. Of the 20 Bok globules observed by ISOCAM to date, we have reduced the data for 14. Of these, 13 show no evidence for faint red (S(sub v)(LW3) greater than S(sub v)(LW2)) stars missed by IRAS. One (CB68) does show the first mid-infrared detection of the very cool IRAS source toward this cloud, and may be a Class I or 0 YSO. We conclude, based on these new ISO observations, that Bok globules which have no IRAS sources are in general bona fide starless molecular clouds.

  10. Molecular Composition of Carbonaceous Globules in the Bells (CM2) Chondrite

    NASA Technical Reports Server (NTRS)

    Clemett, S. J.; Nakamura-Messenger, K.; Thomas-Keprta, K. L.; Robinson, G.-A.; Mckay, D. S.

    2009-01-01

    Some meteorites and IDPs contain micron-size carbonaceous globules that are associated with significant H and/or N isotopic anomalies. This has been interpreted as indicating that such globules may contain at least partial preserved organic species formed in the outer reaches of the proto-solar disk or the presolar cold molecular cloud. Owing to their small sizes, relatively little is known about their chemical compositions. Here we present in situ measurements of aromatic molecular species in organic globules from the Bells (CM2) chondrite by microprobe two-step laser mass spectrometry. This meteorite was chosen for study because we have previously found this meteorite to contain high abundances of globules that often occur in clusters. The Bells (CM2) globules are also noteworthy for having particularly high enrichments in H-2. and N-15. In this study, we identified individual globules and clusters of globules using native UV fluorescence.

  11. Martian paleomagnetism with the SQUID microscope

    NASA Astrophysics Data System (ADS)

    Weiss, Benjamin Paul

    Rocks should preserve natural remanent magnetizations with stable directional and intensity information at levels ˜1000 times below that of the noise level on today's best moment magnetometers. The superconducting quantum interference device (SQUID) Microscope is a new, high-resolution magnetometer that can now detect such weak signals. It maps the magnetic fields above samples with a spatial resolution of <100 mum and a moment sensitivity of <10 -15 Am2. It therefore provides data with a resolution directly comparable with that of other common petrographic techniques. This thesis describes applications of SQUID microscopy to a variety of problems in the planetary sciences. A SQUID microscope paleomagnetic conglomerate test demonstrates that ALH84001 has been cooler than ˜40°C since before its ejection from the surface of Mars at 15 Ma. Because this temperature cannot sterilize most bacteria or eukarya, these data support the hypothesis that meteorites could transfer life between planets in the solar system. These and other data on panspermia demand a re-evaluation of the long-held assumption that terrestrial life evolved in isolation on Earth. Subsequent magnetic and textural studies of the meteorite show that 4 Ga ALH84001 carbonates containing magnetite and pyrrhotite carry a stable natural remanent magnetization. 40Ar/39Ar thermochronology demonstrates that this magnetization originated at 3.9--4.1 Ga on Mars. This magnetization is the oldest known for a planetary rock, and its strong intensity suggests that Mars had generated a geodynamo at or before 4 Ga. The intensity of the field that magnetized ALH84001 was roughly within an order of magnitude of that at the surface of the present-day Earth, sufficient for magnetotaxis by the bacteria whose magnetofossils have been reported in ALH84001 and possibly for the production of the strong crustal anomalies. 40Ar/39Ar thermochronology calculations also provide an explanation for why ALH84001 contains a sample of

  12. Facilitated diffusion of proteins through crumpled fractal DNA globules

    NASA Astrophysics Data System (ADS)

    Smrek, Jan; Grosberg, Alexander Y.

    2015-07-01

    We explore how the specific fractal globule conformation, found for the chromatin fiber of higher eukaryotes and topologically constrained dense polymers, affects the facilitated diffusion of proteins in this environment. Using scaling arguments and supporting Monte Carlo simulations, we relate DNA looping probability distribution, fractal dimension, and protein nonspecific affinity for the DNA to the effective diffusion parameters of the proteins. We explicitly consider correlations between subsequent readsorption events of the proteins, and we find that facilitated diffusion is faster for the crumpled globule conformation with high intersegmental surface dimension than in the case of dense fractal conformations with smooth surfaces. As a byproduct, we obtain an expression for the macroscopic conductivity of a hypothetic material consisting of conducting fractal nanowires immersed in a weakly conducting medium.

  13. X-ray absorption spectroscopy of bacterial sulfur globules

    SciTech Connect

    George, Graham N.

    2002-08-01

    Sulfur K-edge X-ray absorption spectroscopy is a powerful in situ probe of sulfur biochemistry in intact cells and tissues. Under favorable circumstances the technique can provide quantitative information on the chemical identify of the sulfur species that are present in a sample. Prange et al. have recently reported an X-ray absorption spectroscopic study of bacterial sulfur storage globules. Unfortunately there are substantial problems with the experimental technique employed that, they contend, lead to completely erroneous conclusions. In the more recent of their two papers Prange et al. employed a curve-fitting method similar to that used by us (for more than 10 years). In essence, the method employs simply fitting a linear combination of the spectra of standard compounds to that of the unknown, in this case cultures of bacterial cells. This type of analysis can provide quantitative estimates of the individual sulfur types in the sample, but is critically dependent upon the choice of reference spectra. Prange et al. deduce substantial differences between the chemical forms of sulfur stored in the globules of different organisms; they conclude that the globules of Beggiatoa alba and Thiomargarita namibiensis contain cyclo-octasulfur (S{sub 8}), while those of other organisms contain polythionates (Acidithiobacillus ferrooxidans) and polymeric sulfur (e.g. Allochromatium vinosum). This is in contradiction with an earlier study, in which they found that sulfur in all globule species examined resembled that expected for various sized spherical particles of S{sub 8}. The discrepancy is due to an experimental artefact in the work of Prange et al. arising from their choice of transmittance detection, which is also discussed.

  14. Is the Molten Globule a Third Phase of Proteins?

    NASA Astrophysics Data System (ADS)

    Pande, Vijay S.; Rokhsar, Daniel S.

    1998-02-01

    The equilibrium properties of proteins are studied by Monte Carlo simulation of two simplified models of protein-like heteropolymers. These models emphasize the polymeric entropy of the fluctuating polypeptide chain. Our calculations suggest a generic phase diagram that contains a thermodynamically distinct ``molten globule'' state in addition to a rigid native state and a nontrivial unfolded state. The roles of side-chain packing and loop entropy are discussed.

  15. Structure and dynamics of the Bok globule B335

    NASA Technical Reports Server (NTRS)

    Frerking, M. A.; Langer, W. D.; Wilson, R. W.

    1985-01-01

    CO maps of the Bok globule B335 are presented and used to derive its density profile, mass distribution, and rotational velocity structure. It is found that the cloud is in nearly hydrostatic equilibrium with a density profile that varies roughly as r to the -1 in the core and r to the -3 in the envelope. The observed rotation is unimportant in the force balance at the present stage of evolution.

  16. Anticariogenic and phytochemical evaluation of Eucalyptus globules Labill.

    PubMed Central

    Ishnava, Kalpesh B.; Chauhan, Jenabhai B.; Barad, Mahesh B.

    2012-01-01

    In the present study, in vitro anticariogenic potential of ethyl acetate, hexane and methanol and aqueous extracts of plant leaves of Eucalyptus globules Labill. were evaluated by using four cariogenic bacteria, Lactobacillus acidophilus, Lactobacillus casei, Staphylococcus aureus and Streptococcus mutans. Agar well diffusion method and minimum inhibitory concentration (MIC) were used for this purpose. The ethyl acetate extracted fraction of plant leaves showed good inhibitory effects against all selected bacteria. In Eucalyptus globules, hexane and ethyl acetate extracts found highly effective against, Lactobacillus acidophilus with MIC value of 0.031 and 0.062 mg/mL, respectively. Qualitative phytochemical investigation of above extracts showed the presence of alkaloids, phenolic compounds, steroids, cardiac glycosides and terpenes. Based on the MIC value and bioautography, ethyl acetate of plant leaf was selected for further study. Further investigation on the structure elucidation of the bioactive compound using IR, GC-MS and NMR techniques revealed the presence of alpha-farnesene, a sesquiterpene. Eucalyptus globules plant leaf extracts have great potential as anticariogenic agents that may be useful in the treatment of oral disease. PMID:23961222

  17. PIG (partially ionized globule) anatomy - Density and temperature structure of the bright-rimmed globule IC 1396E

    NASA Technical Reports Server (NTRS)

    Serabyn, E.; Guesten, R.; Mundy, L.

    1993-01-01

    The density and temperature structure of the bright-rimmed cometary globule IC 1396E is estimated, and the possibility that recent internal star formation was triggered by the ionization front in its southern surface is assessed. On the basis of NH3 data, gas temperatures in the globule are found to increase outward from the center, from a minimum of 17 K in its tail to a maximum of 26 K on the surface most directly facing the stars ionizing IC 1396. On the basis of a microturbulent radiative transfer code to model the radial dependence of the CS line intensities, and also the intensities of the optically thin 2-1 and 5-4 lines toward the cloud center, a radial density dependence of r exp -1.55 to r exp -1.75 is found.

  18. 2009 Arctic Mars Analogue Svalbard Expedition (AMASE) Evolved Gas Studies

    NASA Astrophysics Data System (ADS)

    Mahaffy, P. R.; McAdam, A.; Eigenbrode, J.; Steele, A.

    2009-12-01

    The Arctic Mars Analogue Svalbard Expedition (AMASE) continued its multi-year campaign in August 2009 to study selected sedimentary and igneous environments in this geological diverse archipelago using a variety of measurement techniques and protocols that are candidates for future Mars missions. The X-ray diffraction mineralogical and evolved gas analysis (EGA) employed during the AMASE-2009 campaign closely mimicked similar experiments that are planned for the 2011 Mars Science Laboratory (MSL). Field instruments similar to those under development for the ESA ExoMars or other rover missions provided imaging, spectroscopic, and subsurface sounding data. A variety of microbiology and field life detection techniques rounded out the AMASE-2009 analytical tools. The evolved gas mass spectrometer utilized on AMASE-2009 was designed to model elements of the Sample Analysis at Mars (SAM) suite of instruments on MSL. Powdered rock samples were heated from ambient to 1000 C in a helium stream and evolved gases continuously analyzed by a mass spectrometer. A continued focus of AMASE-2009 was analysis of carbonates from the Spitsbergen Sverrefjell volcano [1]. The similarity of macromolecular carbon (MMC) associated with magnetite in carbonate globules found in an ice cave in Sverrefjell to those studied in the Mars meteorite ALH84001 has been a motivation for their intensive study. The MMC associated with these carbonates appears to have been formed abiotically [2] following the eruption of the Sverrefjell volcano into glacial ice. The AMASE-2008 EGA studies of microsampled carbonate layers are described and the ability and limitations of these in situ tools to distinguish biomarkers. [1] H. Amundsen, Nature 327, 692-695 (1987). [2] A. Steele et al., Meteoritics and Planetary Science 42, 1549-1566 (2007) Acknowledgement: Support of this work is from the NASA ASTEP program with A. Steele AMASE PI and H. Amundsen Expedition lead.

  19. The formation of elephant-trunk globules in the Rosette nebula: CO observations

    SciTech Connect

    Schneps, M.H.; Ho, P.T.P.; Barrett, A.H.

    1980-08-15

    The prominent elephant-trunk globules in the northwest quadrant of the Rosette nebula have been observed in the microwave lines of CO and /sup 13/CO (J=1..-->..0). The CO emission closely follows the optical outline of the obscuring material and leaves little doubt that the emission is associated with the globules. The physical characteristics derived are typical of those observed in other dust globules which are not necessarily associated with H II regions.

  20. Presolar Organic Globules in Tagish Lake Meteorite, and other Astromaterials

    NASA Technical Reports Server (NTRS)

    Nakamura-Messenger, K.; Messenger, S.; Keller, L. P.; Clemett, S. J.; Zolensky, M. E.

    2009-01-01

    Presolar grains were identified in meteorite residues 20 years ago based on their exotic isotopic compositions. Their study has provide new insights into stellar evolution and the first view of the original building blocks of the solar system. Organic matter in meteorites and IDPs is highly enriched in D/H and N-15/N-14 at micrometer scales, possibly due to presolar organic grains. These anomalies are ascribed to the partial preservation of presolar cold molecular cloud material. Identifying the carriers of these anomalies and elucidating their physical and chemical properties may give new views of interstellar chemistry and better understanding of the original components of the protosolar disk. However, identifying the carriers has been hampered by their small size and the inability to chemically isolate them. Thanks to immediate careful collection of Tagish Lake meteorite specimen, as well as major advances in nano-scale analytical techniques and advanced sample preparation, we were able to show that in the Tagish Lake meteorite, the principle carriers of these isotopic anomalies are sub-micrometer, hollow organic globules. The organic globules likely formed by photochemical processing of organic ices in a cold molecular cloud or the outermost regions of the protosolar disk. Organic globules with similar physical, chemical, and isotopic properties are also recently found from Bells CM2 carbonaceous chondrite, in IDPs and in the comet Wild-2 samples returned by Stardust. These results support the view that microscopic organic grains were widespread constituents of the protoplanetary disk. Their exotic isotopic compositions trace their origins to the outermost portions of the protosolar disk or a presolar cold molecular cloud.

  1. In situ observation of D-rich carbonaceous globules embedded in NWA 801 CR2 chondrite

    NASA Astrophysics Data System (ADS)

    Hashiguchi, Minako; Kobayashi, Sachio; Yurimoto, Hisayoshi

    2013-12-01

    Eighty-five D-rich carbonaceous particles were identified in the matrix of the NWA 801 CR2 chondrite using isotope microscopy. The occurrence of 67 D-rich carbonaceous particles was characterized using secondary electron microscopy combined with X-ray elemental mapping. The close association of H and C, and D-enrichment suggests that the D-rich carbonaceous particles correspond to organic matter. The D-rich organic particles were scattered ubiquitously throughout the matrix at a concentration of approximately 660 ppm. The morphology of the D-rich carbonaceous particles is globular up to about 1 μm in diameter and is classified into four types: ring globules, round globules, irregular-shaped globules, and globule aggregates. The ring globules are ring-shaped organic matter containing silicate and/or oxide, with or without a void in the center. This is the first report of silicate and oxide grains surrounded by D-rich organic matter. The globule aggregates are composed of several D-rich organic globules mixed with silicates. Morphology of ring globules is very similar to core-mantle grain produced in the molecular cloud or in the outer solar nebula inferring by astronomy, suggesting that the organic globules have formed by UV photolysis in the ice mantle. Silicates or oxides attached to D-rich organic globules are the first observation among chondrites so far and may be unique nature of CR2 chondrites. The hydrogen isotopic compositions of the ring globules, round globules, irregular-shaped globules, and globule aggregates are δD = 3000-4800, 2900-8100, 2700-11,000, and 2500-11,000‰, respectively. Variations of D/H ratio of these organic globules seemed to be attributed to variations of D/H ratio of the organic radicals or differences of content of the D-rich organic radicals. There are no significant differences in the hydrogen isotopic compositions among the four types of D-rich carbonaceous matter. The D-enrichments suggest that these organic globules have

  2. Isolation of a novel oil globule protein from the green alga Haematococcus pluvialis (Chlorophyceae).

    PubMed

    Peled, Ehud; Leu, Stefan; Zarka, Aliza; Weiss, Meira; Pick, Uri; Khozin-Goldberg, Inna; Boussiba, Sammy

    2011-09-01

    Cytoplasmic oil globules of Haematococcus pluvialis (Chlorophyceae) were isolated and analyzed for pigments, lipids and proteins. Astaxanthin appeared to be the only pigment deposited in the globules. Triacyglycerols were the main lipids (more than 90% of total fatty acids) in both the cell-free extract and in the oil globules. Lipid profile analysis of the oil globules showed that relative to the cell-free extract, they were enriched with extraplastidial lipids. A fatty acids profile revealed that the major fatty acids in the isolated globules were oleic acid (18:1) and linoleic acid (18:2). Protein extracts from the globules revealed seven enriched protein bands, all of which were possible globule-associated proteins. A major 33-kDa globule protein was partially sequenced by MS/MS analysis, and degenerate DNA primers were prepared and utilized to clone its encoding gene from cDNA extracted from cells grown in a nitrogen depleted medium under high light. The sequence of this 275-amino acid protein, termed the Haematococcus Oil Globule Protein (HOGP), revealed partial homology with a Chlamydomonas reinhardtii oil globule protein and with undefined proteins from other green algae. The HOGP transcript was barely detectable in vegetative cells, but its level increased by more than 100 fold within 12 h of exposure to nitrogen depletion/high light conditions, which induced oil accumulation. HOGP is the first oil-globule-associated protein to be identified in H. pluvialis, and it is a member of a novel gene family that may be unique to green microalgae. PMID:21732215

  3. Electrochemical evidence on the molten globule conformation of cytochrome c.

    PubMed

    Pineda, T; Sevilla, J M; Román, A J; Blázquez, M

    1997-12-01

    To explore a new approach for characterizing the molten globule conformation, cyclic voltammetric studies of salt induced transitions at acidic pH of cyt c have been carried out. The use of modified electrodes has made the observation of direct electrochemistry in native cyt c possible. However, most of these electrodes do not show reversible responses at acidic pH, due to the fact that, for this system, a deprotonated electrode surface is needed. In these studies, we have used a 6-mercaptopurine and cysteine-modified gold electrodes which are effective for direct rapid electron transfer to cyt c, even in acid solutions. The change in the absorption bands of cyt c are used to monitor the conformational states and, hence, to compare the voltammetric results. Under the experimental conditions where the A state of cyt c is obtained, a reversible voltammetric signal is observed. The midpoint peak potentials are found to be very close to the formal potential of native cyt c. Results are discussed in terms of a cooperative two-state transition between the acid unfolded and the globular acidic states of cyt c. This finding establishes, for the first time, the similarity of both the native and the molten globule-like conformations in terms of its redox properties. PMID:9434113

  4. Magnetic fields around BOK globules: CCD polarimetry of CB 4

    NASA Astrophysics Data System (ADS)

    Kane, Brian D.; Clemens, Dan P.; Leach, Robert W.; Barvainis, Richard

    1995-05-01

    The small Bok globule CB 4 was probed using a CCD imaging polarimeter in order to create a detailed map of the magnetic field associated with this cloud. Stars as faint as 17th mag at V band were measured polarimetrically with uncertainties less than 1%. Sky transmission variations were minimized via a system of synchronous polaroid rotation and bidirectional charge shifting. In all, 80 stars behind the periphery of the globule were accurately analyzed polarimetrically. The large-scale (1-2 pc) magnetic field direction around CB 4 was found to be very uniform (P.A. = 63.3 deg +/- 1.1 deg). Double-Gaussian fitting of the polarization position angle histogram gave a dispersion of 10 deg about the primary field direction. Possible field-line compression was found inward of approximately 0.2 pc from the cloud center. No appreciable twisting of field lines was found. By plotting stellar separations against differences of polarization angles, CB 4 was found to have a magnetic field decorrelation length of approximately 0.1 pc, similar to the size of the visually opaque cire, but much smaller than the size of the bright optical rim or CO half-power contour of approximately 0.5 pc. The magnetic field decorrelation length may be related to a characteristic transient clumping size, or perhaps even to clumps of a more permanent nature.

  5. A Two Micron All Sky Survey Analysis of the Stability of Southern Bok Globules

    NASA Astrophysics Data System (ADS)

    Racca, Germán A.; Vilas-Boas, José W. S.; de la Reza, Ramiro

    2009-10-01

    We used near-infrared Two Micron All Sky Survey data to construct visual extinction maps of a sample of Southern Bok globules utilizing the NICE method. We derived radial extinction profiles of dense cores identified in the globules and analyzed their stability against gravitational collapse with isothermal Bonnor-Ebert spheres. The frequency distribution of the stability parameter (ξmax) of these cores shows that a large number of them are located in stable states, followed by an abrupt decrease of cores in unstable states. This decrease is steeper for globules with associated IRAS point sources than for starless globules. Moreover, globules in stable states have a Bonnor-Ebert temperature of T = 15 ± 6 K, while the group of critical plus unstable globules has a different temperature of T = 10 ± 3 K. Distances were estimated to all the globules studied in this work and the spectral class of the IRAS sources was calculated. No variations were found in the stability parameters of the cores and the spectral class of their associated IRAS sources. On the basis of 13CO J = 1 - 0 molecular line observations, we identified and modeled a blue-asymmetric line profile toward a globule of the sample, obtaining an upper limit infall speed of 0.25 km s-1. Based on a Ph.D. thesis made at Observatório Nacional, Rio de Janeiro, Brazil.

  6. Isolation and Characterization of Carotenoid-rich Lipid Globules from Peridinium foliaceum.

    PubMed

    Withers, N W; Haxo, F T

    1978-07-01

    Carotenoid-rich oil globules were isolated from the cytoplasm of the binucleate dinoflagellate, Peridinium foliaceum. These orange globules were collected from ruptured cells by ultracentrifugation on a sucrose density gradient, and checked for purity by electron microscopy. The osmiophilic globules were assayed for lipid (including pigment) and protein content. The lipid to protein ratio was 1.39:1, with a calculated density of the globules of 1.05 grams per cubic centimeter. The lipids were composed of hydrocarbon, wax ester (phytyl ester), triglyceride, and polar (no phospholipid) fractions. The biochemical composition indicated that the globules function as a reservoir of energy-rich components in the cell. Microspectrophotometric observations were consistent with pigment analyses which demonstrated that the globules were carotenoid-rich. In addition to beta-carotene, gamma-carotene, and canthaxanthin, the carotenogenic precursors: phytoene, phytofluence, zeta-carotene and beta-zeacarotene were isolated from the globules. Corrected fluorescence maxima of phytoene and phytofluene in hexane were recorded at 340 and 490 nanometers, respectively. Carotenes constituted 3.3% of the total oil globule lipid. The possibility of an extraplastidic carotenogenic enzyme system in P. foliaceum is discussed. PMID:16660464

  7. Star Formation in the Cometary Globule Ori I-2

    NASA Astrophysics Data System (ADS)

    Mookerjea, Bhaswati; Sandell, Göran

    2009-11-01

    We investigate the young stellar population in and near the cometary globule Ori I-2. The analysis is based on deep Nordic Optical Telescope R-band and Hα images, JCMT SCUBA 450 and 850 μm images combined with near-infrared Two Micron All Sky Survey (2MASS) photometry and mid-infrared archival Spitzer images obtained with the Infrared Array Camera (IRAC; 3.6, 4.5, 5.8, and 8 μm), and MIPS (24 and 70 μm) instruments. We identify a total of 125 sources within the 5'×5' region imaged by the IRAC. Of these sources, 87 are detected in the R-band image and 51 are detected in the 2MASS. The detailed physical properties of the sources are explored using a combination of near/mid-infrared color-color diagrams, graybody fitting of spectral energy distributions (SEDs) and an online SED fitting tool that uses a library of two-dimensional radiation transfer based accretion models of young stellar objects with disks. Ori I-2 shows clear evidence of triggered star formation with four young low-luminosity pre-main-sequence (PMS) stars embedded in the globule. At least two, possibly as many as four, additional low-mass PMS objects were discovered in the field which are probably part of the young σ Orionis cluster. Among the PMS stars which have formed in the globule, MIR-54 is a young, deeply embedded Class 0/I object; MIR-51 and 52 are young Class II sources, while MIR-89 is a more evolved, heavily extincted Class II object with its apparent colors mimicking a Class 0/I object. The Class 0/I object MIR-54 coincides with a previously known IRAS source and is a strong submillimeter source. It is most likely the source for the molecular outflow and the large parsec-scale Herbig-Haro (HH) flow. However, the nearby Class II source, MIR-52, which is strong a Hα emission line star, also appears to drive an outflow approximately aligned with the outflow from MIR-54, and because of the proximity of the two outflows, either star could contribute. MIR-89 appears to excite a low

  8. The Environment and Magnetic Field of Cometary Globule CG30

    NASA Astrophysics Data System (ADS)

    Hickel, Gabriel R.; Vilas-Boas, José W. S.

    2005-09-01

    In this work, we combine observations of optical linear polarization (R band), IRAS far-infrared images and radio molecular lines to investigate the cometary globule CG30 (at IRAS Vela Shell). CG30 shows Herbig-Haro objects, molecular outflows, hosts a very young binary star and has a star formation efficiency of about 6% to 17%. Its magnetic field is important to support the CG structure and shows evidence of torsion and compression of the field lines. The quadrupolar outflow of the binary star affects the temperature of the molecular gas, and changes the degree of polarization of the dust grains in the environment of CG30. This work is based on observations collected at LNA/CNPq, Brazil and SEST/ESO, Chile.

  9. Lunar and Planetary Science XXXVI, Part 19

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Patera? 24) Mars Polar Cap Edges Tracked over 3 Full Mars Years; 25) Elemental Abundance in Presolar SiC: Comparing Grains Separated by Acid Residue and Gently Separation Procedures; 26) First Results from the Descent Imager/Spectral Radiometer (DISR) Experiment on the Huygens Entry Probe of Titan; 27) Minor Element Behavior of Pallasite Olivine: Understanding Pallasite Thermal History and Chronology; 28) Canonical Anorthite in a Grosnaja Forsterite-bearing CAI; 29) Experimental Evidence for Condensation of 'Astrophysical' Carbonate; 30) Distribution and Classification of Multiple Coronae on Venus; 31) Recognition of Rayed Craters on Mars in THEMIS Thermal Infrared Imagery: Implications for Martian Meteorite Source Regions; 32) Geochemical Modeling of Evaporites on Mars: Insight from Meridiani Planum; 33) Hadean Crustal Processes Revealed from Oxygen Isotopes and U-Th-Pb Depth Profiling of Pre-4.0 Ga Detrital Zircons from Western Australia; 34) On Modeling the Seepage of Water into the Martian Subsurface; 35) Martial Gullies and Groundwater: A Series of Unfortunate Exceptions; 36) Olivine and Carbonate Globules in ALH84001: A Terrestrial Analog, and Implications for Water on Mars; 37) A Reevaluation of Mass Movements Within the Valles Marineris Region of Mars Using MOLA and MOC Data; 38) Evidence of Hydrated 109P/Swift-Tuttle Meteoroids from Meteor Spectroscopy; 39) Cr-54 Anomalies in the Solar System: Their Extent and Origin; 40) Reevaluation of the Mn-53-Cr-53 Systematic in the Basaltic Achondrites; 41) Effective Liquid Metal-Silicate Mixing Upon Shock by Power-Law Droplet Size Scaling in Richtmyer-Meshkov Like Perturbations; 42) Post-Impact Deformation of Impact Craters: Towards a Better Understanding Through the Study of Mjolnir Crater; 43) Cutting Silica Aerogel for Particle Extraction; 44) Liquid Hydrocarbons on Titan's Surface? How Cassini ISS Observations Fit into the Story (So Far); and 45) Mesoscale Simulations of Polar Circulations: Late Spring to Late Summe

  10. Effect of coil-globule transition on the single-chain crystallization.

    PubMed

    Wang, Mao-Xiang

    2013-05-30

    The folding process of a single chain including coil-globule transition and crystallization has been investigated through dynamic Monte Carlo simulations. The results based upon ensemble averaging illustrated three distinct states: coil, molten globule, and globule states. Furthermore, the crystallization process from these collapsed states demonstrated various characteristics and it also verified the thermodynamic partitions. The isothermal crystallization in the three states showed the folding rates, and the final crystallite morphologies strongly depended on the collapsed states. Especially, the onset temperature of crystallization in the intermediate molten globule state demonstrated the strongest sensitivity to the solvent qualities in the three different states. Moreover, the crystallization in this intermediate state illustrated a two-step folding mechanism with the prior dense core serving as a precursor to induce the subsequent crystallization. Our observations would help in understanding the thermodynamics and kinetics of phase transition of a single macromolecule. Possible relations to the protein folding were also discussed. PMID:23646890

  11. Formation of Metal and Silicate Globules in Gujba: A New Bencubbin-like Meteorite Fall

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.; Kallemeyn, Gregory W.; Wasson, John T.; Clayton, Robert N.; Mayeda, Toshiko; Grady, Monica; Verchovsky, Alexander B.; Eugster, Otto; Lorenzetti, Silvio

    2006-01-01

    Gujba is a coarse-grained meteorite fall composed of 41 vol% large kamacite globules, 20 vol% large light-colored silicate globules with cryptocrystalline, barred pyroxene and barred olivine textures, 39 vol% dark-colored, silicate-rich matrix, and rare refractory inclusions. Gujba resembles Bencubbin and Weatherford in texture, oxygen-isotopic composition and in having high bulk delta N-15 values (approximately +685%0). The He-3 cosmic-ray exposure age of Gujba (26 +/- 7 Ma) is essentially identical to that of Bencubbin, suggesting that they were both reduced to meter-size fragments in the same parent-body collision. The Gujba metal globules exhibit metal-troilite quench textures and vary in their abundances of troilite and volatile siderophile elements. We suggest that the metal globules formed as liquid droplets either via condensation in an impact-generated vapor plume or by evaporation of preexisting metal particles in a plume. The lower the abundance of volatile elements in the metal globules, the higher the globule quench temperature. We infer that the large silicate globules also formed from completely molten droplets; their low volatile-element abundances indicate that they also formed at high temperatures, probably by processes analogous to those that formed the metal globules. The coarse-grained Bencubbin-Weatherford-Gujba meteorites may represent a depositional component from the vapor cloud enriched in coarse and dense particles. A second class of Bencubbin-like meteorites (represented by Hammadah a1 Hamra 237 and QUE 94411) may be a finer fraction derived from the same vapor cloud

  12. Catalogue of dark nebulae and globules for galactic longitudes 240 to 360 degrees

    NASA Astrophysics Data System (ADS)

    Feitzinger, J. V.; Stuewe, J. A.

    1984-11-01

    A catalogue of dark nebulae and globules has been compiled from a study of the ESO (B) and SRC-J Sky Atlas for galactic longitudes 240° < l11 < 360°. This catalogue closes the great southern gap open since the work of Lynds (l962) for the northern hemisphere. The catalogue (with cross-references) contains positions, sizes, opacities and the van den Bergh (1972) classification on the filamentary morphology of 489 dark clouds and 331 globules.

  13. Mars Life? - Microscopic Tube-like Structures

    NASA Technical Reports Server (NTRS)

    1996-01-01

    This high-resolution scanning electron microscope image shows an unusual tube-like structural form that is less than 1/100th the width of a human hair in size found in meteorite ALH84001, a meteorite believed to be of Martian origin. Although this structure is not part of the research published in the Aug. 16 issue of the journal Science, it is located in a similar carbonate glob in the meteorite. This structure will be the subject of future investigations that could confirm whether or not it is fossil evidence of primitive life on Mars 3.6 billion years ago.

  14. Possible oriented transition of multiple-emulsion globules with asymmetric internal structures in a microfluidic constriction

    NASA Astrophysics Data System (ADS)

    Wang, Jingtao; Li, Xiaoduan; Wang, Xiaoyong; Guan, Jing

    2014-05-01

    When a globule with a complete symmetry (such as simple spherical droplets and concentric double emulsions) is transiting in a constriction tube, there is only one pattern of the transition. However, for a multiple-emulsion globule with asymmetric internal structures, there are many possible patterns with different pressure drops Δp due to various initial orientations of the inner droplets. In this paper, a boundary integral method developed recently is employed to investigate numerically the possible oriented transition of a globule with two unequal inner droplets in an axisymmetric microfluidic constriction. The transition is driven by an axisymmetric Poiseuille flow with a fixed volume flow rate, and the rheological behaviors of the globule are observed carefully. When the big inner droplet is initially located in the front of the globule, the maximum pressure drop during the transition is always lower than that when it is initially placed in the rear. Thus, a tropism—whereby a globule more easily gets through the constriction when its bigger inner droplet locates in its front initially—might exist, in which the orientating stimulus is the required pressure drops. The physical explanation of this phenomenon has also been analyzed in this paper.

  15. Visualization of Microbial Biomarkers by Scanning Electron Microscopy

    NASA Technical Reports Server (NTRS)

    Wainwright, Norman R.; Allen, Carlton C.; Child, Alice

    2001-01-01

    We are developing tools to link the biochemical structure of selected biomarkers with putative biogenic structures observed in mineralized samples. The detection of evidence of life on Mars and other planets will rely on methods that can discriminate compounds formed exclusively by living organisms. While biogenic compounds, such as amino acids and nucleotides have been discovered in extraterrestrial sources, such as meteorites and comets, their formation can be explained by abiotic means. The formation of cellular structures, or more elaborate organic molecules, such as complex lipids, proteins or nucleic acids, however, is strongly correlated to the presence of even the most primitive life processes. Recent evidence lends support to the hypothesis that life may have once existed on Mars. Carbonate globules and ppm concentrations of polycyclic aromatic hydrocarbons (PAHs) have been described in ALH84001, a meteorite originating from Mars ejecta captured by Earth over 13,000 years ago. The localized high concentration of PAHs that follow an increasing gradient from the intact fusion crust towards the interior corresponds to microgram quantities of hydrocarbon. Even though ALH84001 and other similar meteorites have withstood the forces capable of ejecting rock through Mars' escape velocity, upon entering Earth's atmosphere, their core temperatures are likely not to have been raised significantly, as evidenced by the survival of remanent magnetic signatures. Ideal biomarkers of ancient or modern biological life would include molecules that are (or were) pervasive and highly resistant to degradation. Also, requisite methods of detection should be simple, extremely sensitive and broadly inclusive (NASA SP-530). Lipopolysaccharide (LPS), peptidoglycan or pseudopeptidoglycan and beta-glucan are microbial cell wall components which together cover the entire microbial spectrum of eubacteria, archea and fungi. They are all remarkably resistant to thermal degradation

  16. Astrobiological Significance of Microbial Extremophiles

    NASA Technical Reports Server (NTRS)

    Pikuta, Elena V.; Hoover, Richard B.

    2007-01-01

    The microflora of the cryosphere of planet Earth provides the best analogs for life forms that might be found in the permafrost or polar ice caps of Mars, near the surface of the cometary nuclei, or in the liquid water beneath and the ice crusts of icy moons of Jupiter and Saturn. The importance of study alkaliphilic microorganisms for astrobiology was enhanced by the findings of abundant carbonates and carbonate globules rimmed with possibly biogenic magnetites in association with the putative microfossils in the ALH84001 meteorite. Although the ALH84001 "nanofossils" were to small and simple to be unambiguously recognized as biogenic, they stimulated Astrobiology research and studies of microbial extremophiles and biomarkers in ancient rocks and meteorites. Recent studies of CI and CM carbonaceous meteorites have resulted in the detection of the well-preserved mineralized remains of coccoidal and filamentous microorganisms in cyanobacterial mats. Energy Dispersive X-ray Analysis has shown anomalous biogenic element ratios clearly indicating they are not recent biological contaminants. This paper reviews microbial extremophiles in context of their significance to Astrobiology. The study of halophilic microorganisms was started from work with saline soils and lakes, and one of the record of good growth for Haloferax mediterranei was shown at 30 percent NaC1. Although alkali-tolerant nitrifying bacteria had previously been reported, the first described alkaliphilic microorganism was the bacterium Streptococcus faecalis. Halophilic and alkaliphilic forms are relevant to conditions that might be found in closed impact basins and craters on Mars filled with evaporite deposits. The first obligately acidophilic bacterium described was Acidithiobacillus ferrooxydans (formally Thiobacillus ferrooxidans). Later thermophilic lithotrophic acidophiles were found, and the hyperacidophilic moderately thermophilic species of the genus Picrophilus were found to grow at negative p

  17. Isolated milk fat globules as substrate for lipoprotein lipase: study of factors relevant to spontaneous lipolysis in milk

    SciTech Connect

    Sundheim, G.; Bengtsson-Olivecrona, G.

    1987-03-01

    Fat globules isolated from normal and from spontaneous milk samples were compared as substrates for purified lipoprotein lipase. Only slight differences were observed. Fat globules isolated from fresh warm milk were almost resistant to lipolysis. This included globules from milk prone to spontaneous lipolysis. Cooling made the globules accessible to rapid lipolysis even if they were from normal milk. Rewarming the fat globules did not reverse the process. Maximum rate of lipolysis (after rewarming) required fat globules be stored at 10/sup 0/C or below for 5 to 10 h. Lipolysis at 4/sup 0/C usually started after a lag time of 3 to 5 h, but with fat globules from spontaneous milk the lag time was shorter. Fat globules isolated from cold milk were a poor substrate at 4/sup 0/C but were lipolyzed when warmed. When /sup 125/I-labeled lipase was added to fresh warm milk, some of the lipase bound to the milk fat globules but it caused little lipolysis. Binding increased after cooling, as did lipolysis. Both binding of lipase and lipolysis were impeded by the presence of skim milk. Another way to make fat globules isolated from fresh warm milk susceptible to lipolysis was to treat them with chemicals known to remove proteins.

  18. An abiotic origin for hydrocarbons in the Allan Hills 84001 martian meteorite through cooling of magmatic and impact-generated gases

    NASA Technical Reports Server (NTRS)

    Shock, E. L.

    2000-01-01

    Thermodynamic calculations of metastable equilibria were used to evaluate the potential for abiotic synthesis of aliphatic and polycyclic aromatic hydrocarbons (PAHs) in the martian meteorite Allan Hills (ALH) 84001. The calculations show that PAHs and normal alkanes could form metastably from CO, CO2, and H2 below approximately 250-300 degrees C during rapid cooling of trapped magmatic or impact-generated gases. Depending on temperature, bulk composition, and oxidation-reduction conditions, PAHs and normal alkanes can form simultaneously or separately. Moreover, PAHs can form at lower H/C ratios, higher CO/CO2 ratios, and higher temperatures than normal alkanes. Dry conditions with H/C ratios less than approximately 0.01-0.001 together with high CO/CO2 ratios also favor the formation of unalkylated PAHs. The observed abundance of PAHs, their low alkylation, and a variable but high aromatic to aliphatic ratio in ALH 84001 all correspond to low H/C and high CO/CO2 ratios in magmatic and impact gases and can be used to deduce spatial variations of these ratios. Some hydrocarbons could have been formed from trapped magmatic gases, especially if the cooling was fast enough to prevent reequilibration. We propose that subsequent impact heating(s) in ALH 84001 could have led to dissociation of ferrous carbonates to yield fine-grain magnetite, formation of a CO-rich local gas phase, reduction of water vapor to H2, reequilibration of the trapped magmatic gases, aromatization of hydrocarbons formed previously, and overprinting of the synthesis from magmatic gases, if any. Rapid cooling and high-temperature quenching of CO-, H2-rich impact gases could have led to magnetite-catalyzed hydrocarbon synthesis.

  19. An abiotic origin for hydrocarbons in the Allan Hills 84001 martian meteorite through cooling of magmatic and impact-generated gases.

    PubMed

    Zolotov MYu; Shock, E L

    2000-05-01

    Thermodynamic calculations of metastable equilibria were used to evaluate the potential for abiotic synthesis of aliphatic and polycyclic aromatic hydrocarbons (PAHs) in the martian meteorite Allan Hills (ALH) 84001. The calculations show that PAHs and normal alkanes could form metastably from CO, CO2, and H2 below approximately 250-300 degrees C during rapid cooling of trapped magmatic or impact-generated gases. Depending on temperature, bulk composition, and oxidation-reduction conditions, PAHs and normal alkanes can form simultaneously or separately. Moreover, PAHs can form at lower H/C ratios, higher CO/CO2 ratios, and higher temperatures than normal alkanes. Dry conditions with H/C ratios less than approximately 0.01-0.001 together with high CO/CO2 ratios also favor the formation of unalkylated PAHs. The observed abundance of PAHs, their low alkylation, and a variable but high aromatic to aliphatic ratio in ALH 84001 all correspond to low H/C and high CO/CO2 ratios in magmatic and impact gases and can be used to deduce spatial variations of these ratios. Some hydrocarbons could have been formed from trapped magmatic gases, especially if the cooling was fast enough to prevent reequilibration. We propose that subsequent impact heating(s) in ALH 84001 could have led to dissociation of ferrous carbonates to yield fine-grain magnetite, formation of a CO-rich local gas phase, reduction of water vapor to H2, reequilibration of the trapped magmatic gases, aromatization of hydrocarbons formed previously, and overprinting of the synthesis from magmatic gases, if any. Rapid cooling and high-temperature quenching of CO-, H2-rich impact gases could have led to magnetite-catalyzed hydrocarbon synthesis. PMID:11543519

  20. Redefining the dry molten globule state of proteins.

    PubMed

    Neumaier, Sabine; Kiefhaber, Thomas

    2014-06-26

    Dynamics and function of proteins are governed by the structural and energetic properties of the different states they adopt and the barriers separating them. In earlier work, native-state triplet-triplet energy transfer (TTET) on the villin headpiece subdomain (HP35) revealed an equilibrium between a locked native state and an unlocked native state, which are structurally similar but have different dynamic properties. The locked state is restricted to low amplitude motions, whereas the unlocked state shows increased conformational flexibility and undergoes local unfolding reactions. This classified the unlocked state as a dry molten globule (DMG), which was proposed to represent an expanded native state with loosened side-chain interactions and a solvent-shielded core. To test whether the unlocked state of HP35 is actually expanded compared to the locked state, we performed high-pressure TTET measurements. Increasing pressure shifts the equilibrium from the locked toward the unlocked state, with a small negative reaction volume for unlocking (ΔV(0)=-1.6±0.5cm(3)/mol). Therefore, rather than being expanded, the unlocked state represents an alternatively packed, compact state, demonstrating that native proteins can exist in several compact folded states, an observation with implications for protein function. The transition state for unlocking/locking, in contrast, has a largely increased volume relative to the locked and unlocked state, with respective activation volumes of 7.1±0.4cm(3)/mol and 8.7±0.9cm(3)/mol, indicating an expansion of the protein during the locking/unlocking transition. The presented results demonstrate the existence of both compact, low-energy and expanded, high-energy DMGs, prompting a broader definition of this state. PMID:24792909

  1. Contribution of osmotic changes to disintegrative globulization of single cortical fibers isolated from rat lens.

    PubMed

    Wang, L F; Dhir, P; Bhatnagar, A; Srivastava, S K

    1997-08-01

    In this study the contribution of osmotic changes to disintegrative globulization of lens cortical fibers was examined. Single fiber cells were isolated by trypsinization of adult rat lens cortex, and morphological changes elicited by exposure to different external solutions were monitored optically. The survival of the fiber-shaped cells was analysed in accordance with the Weibull distribution. Changes in [Ca2+]i were measured using the fluorescent calcium-sensitive dye-Fluo-3. Exposure of isolated fiber cells to Ringer's solution (containing 2 mm Ca2+) led to an exponential increase in [Ca2+]i with a time constant of 10.2+/-0.8 min, and caused disintegrative globulization in 25+/-4 min (=Tg). The process of globulization as well as the rate of increase in [Ca2+]i was delayed by removing Cl- ions from the external media. Globulization was also delayed by adding 20% bovine serum albumin (Tg=107+/-3 min) or chloride channel inhibitors 5, nitro-2-(3-phenylpropylamino) benzoate (NPPB), dideoxyforskolin, niflumic acid, and tamoxifen. When the fiber cells were suspended in isotonic (280 mm sucrose) HEPES-sucrose (HS) or HEPES-EDTA-sucrose (HES) solution, no globulization was observed for an observation time of 120 min. However, exposure to hypotonic (180 mm) HES solution led to disintegration of fiber cells in 75+/-7 min. Disintegration of the fiber induced by hypotonic HES solution could be delayed by either 0. 05 mm leupeptin (Tg=97+/-6 min) or by pre-loading the fibers with BAPTA (Tg=100+/-4 min). Inhibition of membrane calcium transport by 0.5 mm La3+ had no effect on Tg in hypotonic HES. Addition of 2 mm Ca2+ to HES solution accelerated globulization, and Tg was 57+/-4, 69+/-5 and 102+/-6 min for hypo-, iso- and hyper- tonic solutions, respectively. Transient exposure to calcium also accelerated disintegrative globulization of fiber cells exposed subsequently to HES solution. These results suggest that in ionic media, part of the calcium influx in isolated fiber

  2. Formation of domain-swapped oligomer of cytochrome C from its molten globule state oligomer.

    PubMed

    Deshpande, Megha Subhash; Parui, Partha Pratim; Kamikubo, Hironari; Yamanaka, Masaru; Nagao, Satoshi; Komori, Hirofumi; Kataoka, Mikio; Higuchi, Yoshiki; Hirota, Shun

    2014-07-22

    Many proteins, including cytochrome c (cyt c), have been shown to form domain-swapped oligomers, but the factors governing the oligomerization process remain unrevealed. We obtained oligomers of cyt c by refolding cyt c from its acid molten globule state to neutral pH state under high protein and ion concentrations. The amount of oligomeric cyt c obtained depended on the nature of the anion (chaotropic or kosmotropic) in the solution: ClO4(-) (oligomers, 11% ± 2% (heme unit)), SCN(-) (10% ± 2%), I(-) (6% ± 2%), NO3(-) (3% ± 1%), Br(-) (2% ± 1%), Cl(-) (2% ± 1%), and SO4(2-) (3% ± 1%) for refolding of 2 mM cyt c (anion concentration 125 mM). Dimeric cyt c obtained by refolding from the molten globule state exhibited a domain-swapped structure, in which the C-terminal α-helices were exchanged between protomers. According to small-angle X-ray scattering measurements, approximately 25% of the cyt c molecules were dimerized in the molten globule state containing 125 mM ClO4(-). These results indicate that a certain amount of molten globule state oligomers of cyt c convert to domain-swapped oligomers during refolding and that the intermolecular interactions necessary for domain swapping are present in the molten globule state. PMID:24981551

  3. Signatures in magnetites formed by (Ca,Mg,Fe)CO3 thermal decomposition: Terrestrial and extraterrestrial implications

    NASA Astrophysics Data System (ADS)

    Jimenez-Lopez, Concepcion; Rodriguez-Navarro, Carlos; Rodriguez-Navarro, Alejandro; Perez-Gonzalez, Teresa; Bazylinski, Dennis A.; Lauer, Howard V.; Romanek, Christopher S.

    2012-06-01

    It has never been demonstrated whether magnetite synthesized through the heat-dependent decomposition of carbonate precursors retains the chemical and structural features of the carbonates. In this study, synthetic (Ca,Mg,Fe)CO3 was thermally decomposed by heating from 25 to 700 °C under 1 atm CO2, and by in situ exposure under vacuum to the electron beam of a transmission electron microscope. In both cases, the decomposition of the carbonate was topotactic and resulted in porous pseudomorphs composed of oriented aggregates of magnetite nanocrystals. Both calcium and magnesium were incorporated into nanophase magnetite, forming (Ca,Mg)-magnetites and (Ca,Mg)-ferrites when these elements were present in the parent material, thus preserving the chemical signature of the precursor. These results show that magnetites synthesized in this way acquire a chemical and structural inheritance from their carbonate precursor that indicates how they were produced. These results are not only important in the determination of the origin of chemically-impure, oriented nanophase magnetite crystals in general, but they also provide important insights into the origin of the large, euhedral, chemically-pure, [111]-elongated magnetites found within Ca-, Mg- and Fe-rich carbonates of the Martian meteorite ALH84001. Based on our experimental results, the chemically-pure magnetites within ALH84001 cannot be genetically related to the Ca-, Mg- and Fe-rich carbonate matrix within which they are embedded, and an alternative explanation for their occurrence is warranted.

  4. Individual subunits of bacterial luciferase are molten globules and interact with molecular chaperones.

    PubMed Central

    Flynn, G C; Beckers, C J; Baase, W A; Dahlquist, F W

    1993-01-01

    We have studied the assembly of a large heterodimeric protein, bacterial luciferase, by mixing purified subunits expressed separately in bacteria. The individual subunits alpha and beta contain much (66% and 50%, respectively) of the alpha-helix content of the native heterodimer as measured by circular dichroism, yet the alpha subunit lacks observable tertiary structure as measured by NMR. These results are consistent with the alpha subunit existing in a molten globule or collapsed form prior to assembly. The molecular chaperone GroEL binds reversibly to both subunits prior to assembly. Since these observations were obtained under physiological conditions, we propose that the molten globule exists as a stable form during folding or assembly in the cell. Either the molten globule form of the subunits is an authentic folding intermediate or it is in rapid equilibrium with one. GroEL may function by facilitating assembly through stabilization of these incompletely folded subunits. Images Fig. 4 PMID:7902573

  5. [Milk fat globules, as determinants of the nutritional and biological value of goat milk].

    PubMed

    Skidan, I N; Gulyaev, A E; Kaznacheev, K S

    2015-01-01

    This review summarizes the most complete information on such fundamentally important quality parameters of goat milk as the cellular composition of somatic cells and the structure of cytoplasmic debris in milk. It also focuses on the characterization of an essential component of the energetic value and nutritional content of milk--milk fat globules and milk fat globule membranes. The survey also clarifies some of the terms and meanings of physiological processes associated with the formation of the milk of various ruminants and breast milk. PMID:26841561

  6. Polymers in crowded environment under stretching force: Globule-coil transitions.

    PubMed

    Blavatska, Viktoria; Janke, Wolfhard

    2009-11-01

    We study flexible polymer macromolecules in a crowded (porous) environment, modeling them as self-attracting self-avoiding walks on site-diluted percolative lattices in space dimensions d=2,3 . The influence of stretching force on the polymer folding and the properties of globule-coil transitions are analyzed. Applying the pruned-enriched Rosenbluth chain-growth method, we estimate the transition temperature TTheta between collapsed and extended polymer configurations and construct the phase diagrams of the globule-coil coexistence when varying temperature and stretching force. The transition to a completely stretched state, caused by applying force, is discussed as well. PMID:20364999

  7. Polymers in crowded environment under stretching force: Globule-coil transitions

    NASA Astrophysics Data System (ADS)

    Blavatska, Viktoria; Janke, Wolfhard

    2009-11-01

    We study flexible polymer macromolecules in a crowded (porous) environment, modeling them as self-attracting self-avoiding walks on site-diluted percolative lattices in space dimensions d=2,3 . The influence of stretching force on the polymer folding and the properties of globule-coil transitions are analyzed. Applying the pruned-enriched Rosenbluth chain-growth method, we estimate the transition temperature TΘ between collapsed and extended polymer configurations and construct the phase diagrams of the globule-coil coexistence when varying temperature and stretching force. The transition to a completely stretched state, caused by applying force, is discussed as well.

  8. Dark cloud and globule distribution for galactic longitudes 230 to 360 degrees

    NASA Astrophysics Data System (ADS)

    Feitzinger, J. V.; Stuewe, J. A.

    1984-11-01

    A catalogue of dark nebulae and globules has been compiled from a study of the ESO-B and SRC-J sky atlas for galactic longitudes 230° < l < 360°. This catalogue closes the great southern gap open since the work of Lynds (1962). The authors have listed 489 dark nebulae and 311 globules. The catalogue contains positions, sizes, opacities and the van den Bergh classification (1972) on the filamentary morphology of dark clouds. The authors present statistics concerning the northern and southern distributions and sizes of the nebulae.

  9. Dark Cloud and Globule Distribution for Galactic Longitudes 230 to 360 Degrees

    NASA Technical Reports Server (NTRS)

    Feitzinger, J. V.; Stuewe, J. A.

    1984-01-01

    A catalogue of dark nebulae and globules was compiled from a study of the ESO-B and SRC-J sky atlas for galactic longitudes 230 deg 1 360 deg. This catalogue closes the great southern gap open since the work of Lynds (1962). Listed were 489 dark nebulae and 311 globules. The catalogue contains positions, sizes, opacities, and the van den Bergh classification on the filamentary morphology of dark clouds. Statistics are presented concerning the northern and southern distributions and sizes of the nebulae.

  10. Coil-globule transition of a single short polymer chain: an exact enumeration study.

    PubMed

    Ponmurugan, M; Narasimhan, S L; Krishna, P S R; Murthy, K P N

    2007-04-14

    The authors present an exact enumeration study of short self-avoiding walks in two as well as in three dimensions that addresses the question, "what is the shortest walk for which the existence of all the three scaling regimes--coil, globule, and the theta--could be demonstrated." Even though they could easily demonstrate the coil and the globule phase from free energy considerations, they could demonstrate the existence of a theta temperature only by using a scaling form for the distribution of gyration radius. That even such short walks have a scaling behavior is an unexpected result of this work. PMID:17444742

  11. Thermodynamic analysis of ANS binding to partially unfolded α-lactalbumin: correlation of endothermic to exothermic changeover with formation of authentic molten globules.

    PubMed

    Kim, Ki Hyung; Yun, Soi; Mok, K H; Lee, E K

    2016-09-01

    A fluorescent reporter, 8-anilino-1-naphthalene sulfonic acid (ANS), can serve as a reference molecule for conformational transition of a protein because its aromatic carbons have strong affinity with hydrophobic cores of partially unfolded molten globules. Using a typical calcium-binding protein, bovine α-lactalbumin (BLA), as a model protein, we compared the ANS binding thermodynamics to the decalcified (10 mM EDTA treated) apo-BLA at two representative temperatures: 20 and 40 °C. This is because the authentic molten globule is known to form more heavily at an elevated temperature such as 40 °C. Isothermal titration calorimetry experiments revealed that the BLA-ANS interactions at both temperatures were entropy-driven, and the dissociation constants were similar on the order of 10(-4)  M, but there was a dramatic changeover in the binding thermodynamics from endothermic at 20 °C to exothermic at 40 °C. We believe that the higher subpopulation of authentic molten globules at 40 °C than 20 °C would be responsible for the results, which also indicate that weak binding is sufficient to alter the ANS binding mechanisms. We expect that the thermodynamic properties obtained from this study would serve as a useful reference for investigating the binding of other hydrophobic ligands such as oleic acid to apo-BLA, because oleic acid is known to have tumor-selective cytotoxicity when complexed with partially unfolded α-lactalbumin. Copyright © 2016 John Wiley & Sons, Ltd. PMID:27060481

  12. Developmental changes in the milk fat globule membrane proteome during the transition from colostrum to milk

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Shotgun Proteomics, using amine-reactive isobaric tags (iTRAQ) was used to quantify protein changes in milk fat globule membranes (MFGM) that were isolated from day 1 colostrum and compared to MFGM from day 7 milk. Eight Holstein cows were randomly assigned to 2 groups of 4 cow sample pools for a s...

  13. Infrared study of new star cluster candidates associated to dusty globules

    NASA Astrophysics Data System (ADS)

    Soto King, P.; Barbá, R.; Roman-Lopes, A.; Jaque, M.; Firpo, V.; Nilo, J. L.; Soto, M.; Minniti, D.

    2014-10-01

    We present results from a study of a sample of small star clusters associated to dusty globules and bright-rimmed clouds that have been observed under ESO/Chile public infrared survey Vista Variables in the Vía Láctea (VVV). In this short communication, we analyse the near-infrared properties of a set of four small clusters candidates associated to dark clouds. This sample of clusters associated to dusty globules are selected from the new VVV stellar cluster candidates developed by members of La Serena VVV Group (Barbá et al. 2014). Firstly, we are producing color-color and color-magnitude diagrams for both, cluster candidates and surrounding areas for comparison through PSF photometry. The cluster positions are determined from the morphology on the images and also from the comparison of the observed luminosity function for the cluster candidates and the surrounding star fields. Now, we are working in the procedures to establish the full sample of clusters to be analyzed and methods for subtraction of the star field contamination. These clusters associated to dusty globules are simple laboratories to study the star formation relatively free of the influence of large star-forming regions and populous clusters, and they will be compared with those clusters associated to bright-rimmed globules, which are influenced by the energetic action of nearby O and B massive stars.

  14. Developmental changes in milk fat globule membrane proteome expression during the transition from colostrum to milk

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Shotgun Proteomics, using amine-reactive isobaric tags (iTRAQ) was used to quantify protein changes in milk fat globule membranes (MFGM) that were isolated from day 1 colostrum and compared to MFGM from day 7 milk. Eight Holstein cows were randomly assigned to 2 groups of 4 cow sample pools for a s...

  15. Molten globule state of tear lipocalin: ANS binding restores tertiary interactions.

    PubMed

    Gasymov, Oktay K; Abduragimov, Adil R; Glasgow, Ben J

    2007-06-01

    Tear lipocalin (TL) may stabilize the lipid layer of tears through a molten globule state triggered by low pH. EPR spectroscopy with site-directed spin labeling, revealed the side chain mobility of residues on the G-strand of TL in a molten globule state; the G-strand retains beta-sheet structure. All of the side chains of G-strand residues become more loosely packed, especially residues 96-99. In contrast, the highly mobile side chain of residue 95 on the F-G loop, becomes tightly packed. ANS binding to TL in a molten globule state reestablishes tight packing around side chains that are oriented both inside and outside of the barrel. Unlike RBP and BLG; TL has no disulfide bond between G- and H-strands. It is likely that the central beta-sheet in the molten globule state of lipocalins is stabilized by its interactions with the main alpha-helix, rather than the interstrand disulfide bond. PMID:17434452

  16. Molten Globule State of Tear Lipocalin: ANS Binding Restores Tertiary Interactions

    PubMed Central

    Gasymov, Oktay K.; Abduragimov, Adil R.; Glasgow, Ben J.

    2007-01-01

    Tear lipocalin (TL) may stabilize the lipid layer of tears through a molten globule state triggered by low pH. EPR spectroscopy with site directed spin labeling, revealed the side chain mobility of residues on the G-strand of TL in a molten globule state; the G-strand retains β-sheet structure. All of the side chains of G strand residues become more loosely packed, especially residues 96–99. In contrast, the highly mobile side chain of residue 95 on the F-G loop, becomes tightly packed. ANS binding to TL in a molten globule state reestablishes tight packing around side chains that are oriented both inside and outside of the barrel. Unlike RBP and BLG; TL has no disulfide bond between G and H strands. It is likely that the central β-sheet in the molten globule state of lipocalins is stabilized by its interactions with the main α-helix, rather than the interstrand disulfide bond. PMID:17434452

  17. Molten globule state of tear lipocalin: ANS binding restores tertiary interactions

    SciTech Connect

    Gasymov, Oktay K.; Abduragimov, Adil R.; Glasgow, Ben J. . E-mail: bglasgow@mednet.ucla.edu

    2007-06-01

    Tear lipocalin (TL) may stabilize the lipid layer of tears through a molten globule state triggered by low pH. EPR spectroscopy with site-directed spin labeling, revealed the side chain mobility of residues on the G-strand of TL in a molten globule state; the G-strand retains {beta}-sheet structure. All of the side chains of G-strand residues become more loosely packed, especially residues 96-99. In contrast, the highly mobile side chain of residue 95 on the F-G loop, becomes tightly packed. ANS binding to TL in a molten globule state reestablishes tight packing around side chains that are oriented both inside and outside of the barrel. Unlike RBP and BLG; TL has no disulfide bond between G- and H-strands. It is likely that the central {beta}-sheet in the molten globule state of lipocalins is stabilized by its interactions with the main {alpha}-helix, rather than the interstrand disulfide bond.

  18. Coil–globule transition of a polymer involved in excluded-volume interactions with macromolecules

    SciTech Connect

    Odagiri, Kenta; Seki, Kazuhiko

    2015-10-07

    Polymers adopt extended coil and compact globule states according to the balance between entropy and interaction energies. The transition of a polymer between an extended coil state and compact globule state can be induced by changing thermodynamic force such as temperature to alter the energy/entropy balance. Previously, this transition was theoretically studied by taking into account the excluded-volume interaction between monomers of a polymer chain using the partition function. For binary mixtures of a long polymer and short polymers, the coil-globule transition can be induced by changing the concentration of the shorter polymers. Here, we investigate the transition caused by short polymers by generalizing the partition function of the long polymer to include the excluded-volume effect of short polymers. The coil-globule transition is studied as a function of the concentration of mixed polymers by systematically varying Flory’s χ-parameters. We show that the transition is caused by the interplay between the excluded-volume interaction and the dispersion state of short polymers in the solvent. We also reveal that the same results can be obtained by combining the mixing entropy and elastic energy if the volume of a long polymer is properly defined.

  19. Lipid globules on the plastid surface in Iris tepal epidermis cells during tepal maturation and senescence.

    PubMed

    van Doorn, Wouter G; Prisa, Domenico

    2014-11-15

    Epidermis cells in the outer tepals of Iris flowers (Iris×hollandica, cv. Blue Magic) start programmed cell death (PCD) prior to floral opening. The tepals show visible senescence symptoms three days after full opening. Visible senescence coincides with collapse (death) of the upper epidermis cells. In these cells, electron-dense particles (plastoglobuli), membranes, and oil bodies were observed in the plastid interior. Electron-dense globules similar to plastoglobuli, thus apparently mainly consisting of lipids, were found on the plastid surface, from before flower opening until cell death. Such electron-dense globules were also present in the cytosol. The size of some of the globules on the plastid surface increased with time. The globules are likely involved in transfer of lipidic/proteinaceous material from the plastid to the cytosol. As the plastids contained ample oil bodies, up to the time of cell death, cell death was likely not due to lack of reserves. Mitochondrial ultrastructure also remained the same until cell death. The role of mitochondria in PCD is discussed. PMID:25213705

  20. Polymer globule with fractal properties caused by intramolecular nanostructuring and spatial constrains.

    PubMed

    Glagoleva, Anna A; Vasilevskaya, Valentina V; Khokhlov, Alexei R

    2016-06-21

    By means of computer simulation, we studied macromolecules composed of N dumbbell amphiphilic monomer units with attractive pendant groups. In poor solvents, these macromolecules form spherical globules that are dense in the case of short chains (the gyration radius RG∼N(1/3)), or hollow inside and obey the RG∼N(1/2) law when the macromolecules are sufficiently long. Due to the specific intramolecular nanostructuring, the vesicle-like globules of long amphiphilic macromolecules posses some properties of fractal globules, by which they (i) could demonstrate the same scaling statistics for the entire macromolecule and for short subchains with m monomer units and (ii) possess a specific territorial structure. Within a narrow slit, the globule loses its inner cavity, takes a disk-like shape and scales as N(1/2) for much shorter macromolecules. However, the field of end-to-end distance r(m) ∼m(1/2) dependence for subchains becomes visibly smaller. The results obtained were compared with the homopolymer case. PMID:27198966

  1. Solubilization methods and reference 2-DE map of cow milk fat globules.

    PubMed

    Bianchi, Laura; Puglia, Michele; Landi, Claudia; Matteoni, Silvia; Perini, Daniele; Armini, Alessandro; Verani, Margherita; Trombetta, Claudia; Soldani, Patrizia; Roncada, Paola; Greppi, Gianfranco; Pallini, Vitaliano; Bini, Luca

    2009-07-21

    Milk fat globules (MFGs) are secretory vesicles assembled and secreted by mammary epithelial cells during lactation. They consist of fat globules surrounded by a lipid bilayer membrane which is derived from the apical membrane of the lactating cells. MFGs contain, besides lipids, proteins from the apical plasma membrane and from the cytoplasmatic material. Their peculiar vesicle nature makes them a suitable and easily available source of biological material in monitoring the physiopathological state of the mammary gland. Unfortunately, the conspicuous lipidic component of MFGs consistently limits protein extraction and purification for MFG proteomic investigations. This work deals with the development of a suitable procedure for protein extraction from the cow MFGs in order to qualitatively and quantitatively improve 2-D electropherograms of the MFG. MFGs were purified from raw milk by centrifugation and then delipidated/precipitated. The resulting protein pellets were solubilised using four different 2-D SDS PAGE compatible lysis buffers. Applied methodological procedures for protein extraction and evaluation of the resulting 2-D protein-pattern are presented and discussed. Using these procedures a reference 2-D map of cow milk fat globules is also reported. The majority of the obtained identifications was represented by proteins involved in lipid synthesis or in fat globule secretion. PMID:19111954

  2. Effect of galactose on acid induced molten globule state of Soybean Agglutinin: Biophysical approach

    NASA Astrophysics Data System (ADS)

    Alam, Parvez; Naseem, Farha; Abdelhameed, Ali Saber; Khan, Rizwan Hasan

    2015-11-01

    In the present study the formation of molten globule-like unfolding intermediate Soybean Agglutinin (SBA) in acidic pH range has been established with the help of acrylamide quenching, intrinsic fluorescence, ANS fluorescence measurement, far UV CD and dynamic light scattering measurement. A marked increase in ANS fluorescence was observed at pH 2.2. Ksv of acrylamide quenching was found to be higher at pH 2.2 than that of native SBA at pH 7. Far UV CD spectra of pH induced state suggest that SBA shows significant retention of secondary structure closure to native. Hydrodynamic radius of SBA at pH 2.2 was found be more as compared to native state and also in other pH induced states. Further we checked the effect of galactose on the molten globule state of SBA. This study suggests that SBA exist as molten globule at pH 2.2 and this study will help in acid induced molten globule state of other proteins.

  3. The Role of CO2 in Aqueous Alteration of Ultra-Mafic Rocks and the Formation of MF-,FE-Rich Aqueous Solutons on Early Mars

    NASA Technical Reports Server (NTRS)

    Niles, Paul B.; Yu, M.; Zolotov, M. Yu.; Leshin, L. A.

    2006-01-01

    An adequate understanding of water on Mars that moves beyond the simplistic "warmwet" vs. "cold-dry" dichotomy must include strong constraints on the variables: water/rock ratio, time, temperature, and chemical composition. By constraining these variables first on local, then regional and global scales we will be capable of precisely targeting landed missions to definitively understand the history of water on Mars and the possible existence of life. Data from remote sensing of Mars, landed missions, and martian meteorites indicate that secondary minerals formed from aqueous fluids on Mars are predominately Fe- and Mg-rich. The unique Mg-, Fe-rich carbonates in the ALH 84001 meteorite provide an excellent opportunity to provide strong constraints on an Fe-, Mg-rich aqueous system on early Mars. This work seeks to use the unusual chemical compositions of the ALH 84001 carbonates as a constraint for the composition of their formation fluid. These constraints can be used to better understand aqueous processes at a critical time in martian history.

  4. Aqueous Chemical Modeling of Sedimentation on Early Mars with Application to Surface-Atmosphere Evolution

    NASA Technical Reports Server (NTRS)

    Catling, David C.

    2004-01-01

    This project was to investigate models for aqueous sedimentation on early Mars from fluid evaporation. Results focused on three specific areas: (1) First, a fluid evaporation model incorporating iron minerals was developed to compute the evaporation of a likely solution on early Mars derived from the weathering of mafic rock. (2) Second, the fluid evaporation model was applied to salts within Martian meteorites, specifically salts in the nakhlites and ALH84001. Evaporation models were found to be consistent with the mineralogy of salt assemblages-anhydrite, gypsum, Fe-Mg-Ca carbonates, halite, clays-- and the concentric chemical fractionation of Ca-to Mg-rich carbonate rosettes in ALH84001. We made progress in further developing our models of fluid concentration by contributing to updating the FREZCHEM model. (3) Third, theoretical investigation was done to determine the thermodynamics and kinetics involved in the formation of gray, crystalline hematite. This mineral, of probable ancient aqueous origin, has been observed in several areas on the surface of Mars by the Thermal Emission Spectrometer on Mars Global Surveyor. The "Opportunity" Mars Exploration Rover has also detected gray hematite at its landing site in Meridiani Planum. We investigated how gray hematite can be formed via atmospheric oxidation, aqueous precipitation and subsequent diagenesis, or hydrothermal processes. We also studied the geomorphology of the Aram Chaos hematite region using Mars Orbiter Camera (MOC) images.

  5. Milk quality and automatic milking: fat globule size, natural creaming, and lipolysis.

    PubMed

    Abeni, F; Degano, L; Calza, F; Giangiacomo, R; Pirlo, G

    2005-10-01

    Thirty-eight Italian Friesian first-lactation cows were allocated to 2 groups to evaluate the effect of 1) an automatic milking system (AMS) vs. milking in a milking parlor (MP) on milk fat characteristics; and 2) milking interval (< or =480, 481 to 600, 601 to 720, and >720 min) on the same variables. Milk fat was analyzed for content (% vol/vol), natural creaming (% of fat), and free fatty acids (FFA, mEq/100 g of fat). Distribution of milk fat globule size was evaluated to calculate average fat globule diameter (d(1)), volume-surface average diameter (d(32)), specific globule surface area, and mean interglobular distance. Milk yield was recorded to calculate hourly milk and milk fat yield. Milking system had no effect on milk yield, milk fat content, and hourly milk fat yield. Milk from AMS had less natural creaming and more FFA content than milk from MP. Fat globule size, globular surface area, and interglobular distance were not affected by milking system per se. Afternoon MP milkings had more fat content and hourly milk fat yield than AMS milkings when milking interval was >480 min. Milk fat FFA content was greater in AMS milkings when milking interval was < or =480 min than in milkings from MP and from AMS when milking interval was >600 min. Milking interval did not affect fat globule size, expressed as d32. Results from this experiment indicate a limited effect of AMS per se on milk fat quality; a more important factor seems to be the increase in milking frequency, generally associated with AMS. PMID:16162526

  6. A novel infant milk formula concept: Mimicking the human milk fat globule structure.

    PubMed

    Gallier, Sophie; Vocking, Karin; Post, Jan Andries; Van De Heijning, Bert; Acton, Dennis; Van Der Beek, Eline M; Van Baalen, Ton

    2015-12-01

    Human milk (HM) provides all nutrients to support an optimal growth and development of the neonate. The composition and structure of HM lipids, the most important energy provider, have an impact on the digestion, uptake and metabolism of lipids. In HM, the lipids are present in the form of dispersed fat globules: large fat droplets enveloped by a phospholipid membrane. Currently, infant milk formula (Control IMF) contains small fat droplets primarily coated by proteins. Recently, a novel IMF concept (Concept IMF) was developed with a different lipid architecture, Nuturis(®), comprising large fat droplets with a phospholipid coating. Confocal laser scanning microscopy (CLSM), with appropriate fluorescent probes, and transmission electron microscopy were used to determine and compare the interfacial composition and structure of HM fat globules, Concept IMF fat droplets and Control IMF fat droplets. The presence of a trilayer-structured HM fat globule membrane, composed of phospholipids, proteins, glycoproteins and cholesterol, was confirmed; in addition exosome-like vesicles are observed within cytoplasmic crescents. The Control IMF fat droplets had a thick protein-only interface. The Concept IMF fat droplets showed a very thin interface composed of a mixture of phospholipids, proteins and cholesterol. Furthermore, the Concept IMF contained fragments of milk fat globule membrane, which has been suggested to have potential biological functions in infants. By mimicking more closely the structure and composition of HM fat globules, this novel IMF concept with Nuturis(®) may have metabolic and digestive properties that are more similar to HM compared to Control IMF. PMID:26432620

  7. Illuminating the off-pathway nature of the molten globule folding intermediate of an α-β parallel protein.

    PubMed

    Lindhoud, Simon; Westphal, Adrie H; Borst, Jan Willem; van Mierlo, Carlo P M

    2012-01-01

    Partially folded protein species transiently form during folding of most proteins. Often, these species are molten globules, which may be on- or off-pathway to the native state. Molten globules are ensembles of interconverting protein conformers that have a substantial amount of secondary structure, but lack virtually all tertiary side-chain packing characteristics of natively folded proteins. Due to solvent-exposed hydrophobic groups, molten globules are prone to aggregation, which can have detrimental effects on organisms. The molten globule observed during folding of the 179-residue apoflavodoxin from Azotobacter vinelandii is off-pathway, as it has to unfold before native protein can form. Here, we study folding of apoflavodoxin and characterize its molten globule using fluorescence spectroscopy and Förster Resonance Energy Transfer (FRET). Apoflavodoxin is site-specifically labeled with fluorescent donor and acceptor dyes, utilizing dye-inaccessibility of Cys69 in cofactor-bound protein. Donor (i.e., Alexa Fluor 488) is covalently attached to Cys69 in all apoflavodoxin variants used. Acceptor (i.e., Alexa Fluor 568) is coupled to Cys1, Cys131 and Cys178, respectively. Our FRET data show that apoflavodoxin's molten globule forms in a non-cooperative manner and that its N-terminal 69 residues fold last. In addition, striking conformational differences between molten globule and native protein are revealed, because the inter-label distances sampled in the 111-residue C-terminal segment of the molten globule are shorter than observed for native apoflavodoxin. Thus, FRET sheds light on the off-pathway nature of the molten globule during folding of an α-β parallel protein. PMID:23029219

  8. A Short, Critical Evaluation of Proposed Signs of Ancient Martian

    NASA Astrophysics Data System (ADS)

    Treiman, Allan

    Unambiguous identification of fossil traces of life (terrestrial or extraterrestrial) can be difficult or impossible. For instance, many shapes in the 0.1 - 10 micron size range can form biologically or abiotically. Published images of such shapes in ALH84001 have been Rorschach tests of our preconceptions: biologists tend to see biological influences; inorganic chemists or petrolgists see abiotic processes. Similarly, many complex carbon compounds can also form from biologic or abiotic precursors; some see degraded biological matter, other see organic syntheses. In this light, W. Schopf's checklist of characteristics for microfossils has not provided an answer to whether there are traces of ancient martian life in ALH84001; members of D. McKay's research group claim to have satisfied all these criteria, yet few biologists or meteoriticists have been convinced. The job of the exobiologist has been complicated greatly by recent recognition of life in nearly all low-T environments on Earth. If all our terrestrial systems are influenced by biology, how can we recognize a sterile system?

  9. Immunocytochemical Evidence for Golgi Vesicle Involvement in Milk Fat Globule Secretion.

    PubMed

    Wooding, F B Peter; Sargeant, Timothy J

    2015-12-01

    The exact mechanism of secretion of the milk fat globule (MFG) from the mammary secretory cell is still controversial. We have previously suggested close involvement of Golgi vesicles in this process. This paper provides direct immunocytochemical evidence that butyrophilin is present in the Golgi stack and vesicles in ovine and caprine mammary glands. We suggest that it is the butyrophilin in the Golgi vesicle membrane that forms the specific association with the adipophilin on the lipid surface in the cytoplasm. Exocytosis of the associated Golgi vesicle will then initiate the process of MFG secretion. Further exocytosis of associated Golgi vesicles will continue and complete the process. Areas of the plasmalemma that have butyrophilin delivered by previous non-lipid associated Golgi exocytoses may also contribute to the process of forming the milk fat globule membrane (MFGM). PMID:26374828

  10. Optical Coherence Tomography Findings in Anterior Chamber Ointment Globule after Phacoemulsification.

    PubMed

    Mansour, Ahmad M; Haddad, Randa S; Salti, Haytham I; Habbal, Zuhair

    2015-01-01

    We present 2 cases of anterior chamber ointment with evidence of progressive endothelial cell loss. In both cases, an anterior segment optical coherence tomography (OCT) was similar to an OCT of a tobramycin-dexamethasone ointment placed on a pen tip. An anterior segment OCT also demonstrated the direct contact of the globule with the corneal endothelium. A gas chromatography/mass spectrometry analysis documented the similarity to tobramycin-dexamethasone ointment in 1 case. Anterior segment OCT can help in confirming the diagnosis. Corneal endothelial injury is a continuous process, and its clinical manifestation is related to the size of the globule, the initial endothelium count, and the duration of ointment contact, which is related to supine positioning. It is advisable to avoid ointments in the immediate postoperative period, especially in corneal wounds larger than 3 mm. PMID:26955351

  11. Optical Coherence Tomography Findings in Anterior Chamber Ointment Globule after Phacoemulsification

    PubMed Central

    Mansour, Ahmad M.; Haddad, Randa S.; Salti, Haytham I.; Habbal, Zuhair

    2015-01-01

    We present 2 cases of anterior chamber ointment with evidence of progressive endothelial cell loss. In both cases, an anterior segment optical coherence tomography (OCT) was similar to an OCT of a tobramycin-dexamethasone ointment placed on a pen tip. An anterior segment OCT also demonstrated the direct contact of the globule with the corneal endothelium. A gas chromatography/mass spectrometry analysis documented the similarity to tobramycin-dexamethasone ointment in 1 case. Anterior segment OCT can help in confirming the diagnosis. Corneal endothelial injury is a continuous process, and its clinical manifestation is related to the size of the globule, the initial endothelium count, and the duration of ointment contact, which is related to supine positioning. It is advisable to avoid ointments in the immediate postoperative period, especially in corneal wounds larger than 3 mm. PMID:26955351

  12. Coil-globule transition of a single semiflexible chain in slitlike confinement

    PubMed Central

    Dai, Liang; Renner, C. Benjamin; Yan, Jie; Doyle, Patrick S.

    2015-01-01

    Single polymer chains undergo a phase transition from coiled conformations to globular conformations as the effective attraction between monomers becomes strong enough. In this work, we investigated the coil-globule transition of a semiflexible chain confined between two parallel plates, i.e. a slit, using the lattice model and Pruned-enriched Rosenbluth method (PERM) algorithm. We find that as the slit height decreases, the critical attraction for the coil-globule transition changes non-monotonically due to the competition of the confinement free energies of the coiled and globular states. In wide (narrow) slits, the coiled state experiences more (less) confinement free energy, and hence the transition becomes easier (more difficult). In addition, we find that the transition becomes less sharp with the decreasing slit height. Here, the sharpness refers to the sensitivity of thermodynamic quantities when varying the attraction around the critical value. The relevant experiments can be performed for DNA condensation in microfluidic devices. PMID:26679086

  13. Histochemical and biochemical observations on milk-fat-globule membranes from several mammalian species.

    PubMed

    Welsch, U; Schumacher, U; Buchheim, W; Schinko, I; Jenness, P; Patton, S

    1990-01-01

    A specific secretory product of the lactating mammary gland are triglyceride fat globules which are enveloped by a very complex membrane, the milk fat globule membrane (MFGM). In different mammalian species (man, rhesus monkey, horse, goat, sheep, cow, grey seal, camel, alpaka) the glycoproteins of this membrane have been analyzed by gel electrophoresis, Western blotting and lectin histochemistry. A remarkable intra- and interspecific variability of these glycoproteins has been detected pointing to so far unknown physiological adaptions, which may play a role in the intestine of the new born. High molecular weight glycoproteins, with a very high degree of glycosilation have been found only in primates, horse and camel; the MFGMs of the true ruminants (cow, sheep, goat) are characterized by specific glycoproteins of a lower molecular weight range. PMID:2091048

  14. Far-infrared detection of low-luminosity star formation in the Bok globule B335

    NASA Technical Reports Server (NTRS)

    Davidson, J. A.; Harper, D. A.; Pernic, R.; Jaffe, D. T.; Low, F. J.; Keene, J.; Hildebrand, R. H.; Loewenstein, R. F.

    1983-01-01

    Measurements of far-infrared intensities in the Bok globule B335, made with higher spatial and spectral resolution than two earlier studies, are described. The NASA 3-m Infrared Telescope Facility was used in February 1981 and the Kuiper Airborne Observatory 0.9-m telescope was used in October 1981 and August 1982 for the observations. The far-infrared source in B335 was revealed to be more compact than previously assumed, ruling out the interstellar radiation field as the dominant heat source. The new far-infrared size, luminosity, and temperature derived suggest that these may be the first observations of low-mass star formation embedded deeply within a Bok globule. The far-infrared source does not have a near-infrared or radio continuum counterpart. High angular resolution at submillimeter wavelengths will be critical in further studies of low-mass star formation.

  15. Coil-globule transition of a single semiflexible chain in slitlike confinement

    NASA Astrophysics Data System (ADS)

    Dai, Liang; Renner, C. Benjamin; Yan, Jie; Doyle, Patrick S.

    2015-12-01

    Single polymer chains undergo a phase transition from coiled conformations to globular conformations as the effective attraction between monomers becomes strong enough. In this work, we investigated the coil-globule transition of a semiflexible chain confined between two parallel plates, i.e. a slit, using the lattice model and Pruned-enriched Rosenbluth method (PERM) algorithm. We find that as the slit height decreases, the critical attraction for the coil-globule transition changes non-monotonically due to the competition of the confinement free energies of the coiled and globular states. In wide (narrow) slits, the coiled state experiences more (less) confinement free energy, and hence the transition becomes easier (more difficult). In addition, we find that the transition becomes less sharp with the decreasing slit height. Here, the sharpness refers to the sensitivity of thermodynamic quantities when varying the attraction around the critical value. The relevant experiments can be performed for DNA condensation in microfluidic devices.

  16. Comparative proteomics of milk fat globule membrane in different species reveals variations in lactation and nutrition.

    PubMed

    Lu, Jing; Wang, Xinyu; Zhang, Weiqing; Liu, Lu; Pang, Xiaoyang; Zhang, Shuwen; Lv, Jiaping

    2016-04-01

    In present study, 312, 554, 175 and 143 proteins were identified and quantified by label-free quantitative proteomics in human, cow, goat and yak milk fat globule membrane (MFGM), respectively. Fifty proteins involved in vesicle mediate transport and milk fat globule secretion were conserved among species. Moreover, proteins involved in lipid synthesis and secretion (xanthine dehydrogenase/oxidase, stomatin and CD36), showed different expression pattern and the host defense proteins exhibited various profiles within species. Notably, the content and activity of lipid catabolic enzymes were significantly higher in human MFGM, which could be indicative of the superior fat utilization in breast fed infants. Our findings unraveled the significant differences in protein composition of human milk and conventionally used substitutes of it. The in-depth study of lipid metabolic enzymes in human MFGM will probably contribute to the improvement of the fat utilization through modulation of lipid catabolic enzymes in infant formula. PMID:26593540

  17. A protective effect of milk fat globule EGF factor VIII (MFG-E8) on the spontaneous fusion of milk fat globules in breast milk.

    PubMed

    Yasueda, Takehiko; Oshima, Kenzi; Nakatani, Hajime; Tabuchi, Kanji; Nadano, Daita; Matsuda, Tsukasa

    2015-07-01

    Lipid droplets synthesized in mammary epithelial cells are secreted into breast milk by the budding-off mechanism. The milk lipids, termed mik fat globules (MFGs), are surrounded with the cell plasma membrane and contain various membrane proteins, including milk fat globule epidermal growth factor (EGF)-factor VIII (MFG-E8), on their surface. We report here that the MFGs in the milk of MFG-E8-deficient mice fused each other and turned into abnormally large size of lipid droplets within ∼48 h after being secreted into mammary alveolar lumen in situ or being incubated at 37°C in vitro. This biophysical degeneration of MFGs in the MFG-E8-deficient milk was efficiently rescued in vitro by adding the milk serum of wild-type mice, isolated MFG-E8 or annexin V. Moreover, addition of ethylenediaminetetraacetic acid (30 mM) also protected the MFG fusion remarkably in vitro. In addition, bovine MFGs also fused each other when isolated from milk serum, and the fusion was inhibited by adding isolated MFG-E8 or mouse milk serum, but not the milk serum of MFG-E8-deficient mice. MFG-E8 in breast milk may mask the phosphatidylserine exposed on the surface of MFGs with time after secretion and thereby suppress the membrane fusion among MFGs resulting in the enlargement of MFGs in the breast milk. PMID:25661589

  18. Milk Fat Content and DGAT1 Genotype Determine Lipid Composition of the Milk Fat Globule Membrane

    PubMed Central

    Argov-Argaman, Nurit; Mida, Kfir; Cohen, Bat-Chen; Visker, Marleen; Hettinga, Kasper

    2013-01-01

    During secretion of milk fat globules, triacylglycerol (TAG) droplets are enveloped by a phospholipid (PL) trilayer. Globule size has been found to be related to polar lipid composition and fat content, and milk fat content and fatty acid composition have been associated with the diacylglycerol acyltransferase 1 (DGAT1) K232A polymorphism; however, the association between the DGAT1 polymorphism and fat globule size and polar lipid composition has not been studied. The ratio between polar and neutral lipids as well as the composition of the polar lipids in milk has industrial as well as nutritional and health implications. Understanding phenotypic and genotypic factors influencing these parameters could contribute to improving milk lipid composition for dairy products. The focus of the present study was to determine the effect of both fat content and DGAT1 polymorphism on PL/TAG ratio, as a marker for milk fat globule size, and detailed PL composition. Milk samples were selected from 200 cows such that there were equal numbers of samples for the different fat contents as well as per DGAT1 genotype. Samples were analyzed for neutral and polar lipid concentration and composition. PL/TAG ratio was significantly associated with both fat content and DGAT1 genotype. Phosphatidylinositol and phosphatidylserine concentrations were associated with fat content*DGAT1 genotype with a stronger association for the AA than the KK genotype. Sphingomyelin concentration tended to interact with fat content*DGAT1 genotype. Phosphatidylethanolamine (PE) concentration showed a biphasic response to fat content, suggesting that multiple biological processes influence its concentration. These results provide a new direction for controlling polar lipid concentration and composition in milk through selective breeding of cows. PMID:23874734

  19. Photopolarimetric study of three selected Bok globule (CB56, CB60 and CB69)

    NASA Astrophysics Data System (ADS)

    Chakraborty, Arindwam; Sekhar Das, Himadri; Paul, Dipankar

    2015-08-01

    Bok globules are small isolated dark cloud with a simple structure, when seen through optical wavelengths they looks like a dark patch surrounded by some bright foreground stars. Because of their isolated location and simple structure, they are ideal laboratories, to study in detail the process of low-mass star formation. Aligned dust grains in the interstellar medium (ISM) and the Bok globule polarize the radiation through dichroic extinction. Magnetic fields plays a vital roles in interstellar processes and star formation, and the polarization that results from grain alignment provides the means to study magnetic fields. The relative role played by the magnetic field and the turbulence in cloud formation and evolution in different stages of star formation is quite interesting matter of study. In this paper we will present a combined study of polarization and extinction (Av) of observed background field stars of CB56, CB60 and CB69. We have mapped the local magnetic fields of these globules in V-band by estimating the value of linear polarization of background stars and hence created respective polarization maps. Background field stars are used to probe polarization efficiency (defined as pv/Av) in the quiescent regions of these dark clouds as a function of visual extinction. Our study indicates that the interstellar dust grains alignment decreases with the increase in extinction. This type of study help us in studying the direct interplay between protostellar collapse, fragmentation and magnetic fields.

  20. [Lipid Composition of Different Breeds of Milk Fat Globules by Confocal Raman Microscopy].

    PubMed

    Luo, Jie; Wang, Zi-wei; Song, Jun-hong; Pang, Rui-peng; Ren, Fa-zheng

    2016-01-01

    Different breeds of cows affect the form of fat exist in dairy products and the final functionality, which depended mainly on the composition of the milk fat globules(MFG). However, the relationship between the composition and breeds has not been illuminated. In our study, differences in the lipid content and fatty acid composition of native bovine, buffalo and yak MFG were investigated by confocal Raman spectroscopy. The research offers the possibility of acquisition and analysis of the Raman signal without disruption of the structure of fat globule. The results showed that yak MFG had a higher ratio of band intensities at 2 885/2 850 cm(-1), indicating yak MFG tend to have a triglyceride core in a fluid state with a milk fat globule membrane in a crystalline state. The buffalo and yak MFG had a higher level of unsaturation compared to bovine MFG, shown by a higher ratio of band intensities at 1 655/1 744 cm(-1). The results indicate that small MFG of buffalo is more unsaturated than yak, while the large MFG of buffalo is less unsaturated than the yak. Thus, selective use of cream with yak MFG would allow a harder and more costly churning process but lead to a softer butter. Buffalo milk which contains larger MFG is more suitable for cream and MFG membrane separation. PMID:27228754

  1. Influence of the oil globule fraction on the release rate profiles from multiple W/O/W emulsions.

    PubMed

    Bonnet, Marie; Cansell, Maud; Placin, Frédéric; Monteil, Julien; Anton, Marc; Leal-Calderon, Fernando

    2010-06-15

    Water-in-oil-in-water (W/O/W) double emulsions were prepared and the kinetics of release of magnesium ions from the internal to the external water phase was investigated as a function of the formulation and the globule volume fraction. All the emulsions were formulated using the same surface-active species (polyglycerol polyricinoleate and sodium caseinate). Also, the internal droplet and oil globule diameters were almost identical for all the systems. Two types of W/O/W emulsions were prepared based either on a synthetic oil (miglyol) or on an edible oil (olive oil). The globule volume fraction varied from 11% to 72%. At constant temperature (T=25 degrees C) and irrespective of the oil type, the percentage of magnesium released was lowered by increasing the globule fraction. In all cases, magnesium leakage occurred without film rupturing (no coalescence). Thus, the experimental data were interpreted within the frame of a model based on diffusion. The rate of release was determined by the permeation coefficient of magnesium across the oil phase and by the binding (chelation) of magnesium by caseinate molecules. The data could be adequately fitted by considering a time-dependant permeation coefficient. The better retention of magnesium at high globule fractions could account for two distinct phenomena: (i) the reduction of the relative volume of the outer phase, and (ii) the attenuation of the permeation coefficient over time induced by interfacial magnesium binding, all the more important than the globule fraction increased. PMID:20207114

  2. Pillars and globules at the edges of H ii regions. Confronting Herschel observations and numerical simulations

    NASA Astrophysics Data System (ADS)

    Tremblin, P.; Minier, V.; Schneider, N.; Audit, E.; Hill, T.; Didelon, P.; Peretto, N.; Arzoumanian, D.; Motte, F.; Zavagno, A.; Bontemps, S.; Anderson, L. D.; André, Ph.; Bernard, J. P.; Csengeri, T.; Di Francesco, J.; Elia, D.; Hennemann, M.; Könyves, V.; Marston, A. P.; Nguyen Luong, Q.; Rivera-Ingraham, A.; Roussel, H.; Sousbie, T.; Spinoglio, L.; White, G. J.; Williams, J.

    2013-12-01

    Context. Herschel far-infrared imaging observations have revealed the density structure of the interface between H ii regions and molecular clouds in great detail. In particular, pillars and globules are present in many high-mass star-forming regions, such as the Eagle nebula (M 16) and the Rosette molecular cloud, and understanding their origin will help characterize triggered star formation. Aims: The formation mechanisms of these structures are still being debated. The initial morphology of the molecular cloud and its turbulent state are key parameters since they generate deformations and curvatures of the shell during the expansion of the H ii region. Recent numerical simulations have shown how pillars can arise from the collapse of the shell in on itself and how globules can be formed from the interplay of the turbulent molecular cloud and the ionization from massive stars. The goal here is to test this scenario through recent observations of two massive star-forming regions, M 16 and the Rosette molecular cloud. Methods: First, the column density structure of the interface between molecular clouds and associated H ii regions was characterized using column density maps obtained from far-infrared imaging of the Herschel HOBYS key programme. Then, the DisPerSe algorithm was used on these maps to detect the compressed layers around the ionized gas and pillars in different evolutionary states. Column density profiles were constructed. Finally, their velocity structure was investigated using CO data, and all observational signatures were tested against some distinct diagnostics established from simulations. Results: The column density profiles have revealed the importance of compression at the edge of the ionized gas. The velocity properties of the structures, i.e. pillars and globules, are very close to what we predict from the numerical simulations. We have identified a good candidate of a nascent pillar in the Rosette molecular cloud that presents the velocity

  3. Morphology of globules and cenospheres in heavy fuel oil burner experiments

    SciTech Connect

    Kwack, E.Y.; Shakkottai, P.; Massier, P.F.; Back, L.H. )

    1992-04-01

    Number 6 fuel oil was heated, sprayed, and burned in an enclosure using a small commercial oil burner. Samples of residues that emerged from the flame were collected at various locations outside the flame and observed by a scanning electron microscope. Porous cenospheres, larger globules (of size 80 {mu}m to 200 {mu}m) that resemble soap bubbles formed from the very viscous liquid residue, and unburned oil drops were the types of particle collected. This paper reports on the qualitative relationships of the morphology of these particles to the temperature history to which they were subjected were made.

  4. Triggered star-formation in the bright rimmed globule IC1396A

    NASA Astrophysics Data System (ADS)

    Patel, Nimesh A.; Sicilia-Aguilar, Aurora; Goldsmith, Paul

    2015-01-01

    IC1396 is a well known HII region and molecular cloud complex surrounding the Trumpler 37 cluster of OB stars in the Cepheus OB2 association. The dense, elephant trunk shaped globules in this region typically show bright rims facing the central exciting O6 star HD~206267. This region, at a distance of 870 pc, is an excellent astrophysical laboratory for studying the feedback effects of massive stars on neighboring molecular clouds. Triggered star formation occurs when dense cores (which would otherwise remain stable) are compressed and made unstable by the sustained energy input from the OB association. Observationally it remains challenging to prove whether the onset of star-formation in such globules is triggered or spontaneous.Using the Submillimeter Array (SMA), we observed IC1396 globule A (Pottasch 1958 nomenclature), targeting four newly discovered protostars from recent Herschel PACS observations. Here we present 230 GHz molecular line (CO, 13CO, C18O, N2D+ and H2CO) and continuum results for the source IC1396A-PACS-1 (Sicilia-Aguilar et al. 2014). This is a Class 0 source very close to the edge of the ionization front and Herschel observations show this to be a most promisingcase of triggered star-formation. The SMA 230 GHz continuum source has a flux density of 280 mJy. We estimate a dust mass of about 0.1 Msun in this source which appears very compact in our 5" beam. CO, 13CO and C18O emission is largely resolved out by the interferometer and will require combined imaging with single-dish observations. (We have a parallel ongoing study being carried out with the IRAM 30m telescope). SMA N2D+ emission peaks on the continuum sourceand is partially resolved. H2CO emission appears to avoid the peak of continuum and N2D+, suggesting depletion. Both the morphology and kinematics in H2CO emission are indicative of internal disturbance, away from the PDR region into the globule.

  5. The dynamics of the biological membrane surrounding the buffalo milk fat globule investigated as a function of temperature.

    PubMed

    Nguyen, Hanh T H; Madec, Marie-Noëlle; Ong, Lydia; Kentish, Sandra E; Gras, Sally L; Lopez, Christelle

    2016-08-01

    The biological membrane surrounding fat globules in milk (the MFGM) is poorly understood, despite its importance in digestion and in determining the properties of fat globules. In this study, in situ structural investigations of buffalo MFGM were performed as a function of temperature (4-60°C), using confocal microscopy. We demonstrate that temperature and rate of temperature change affected the lipid domains formed in the MFGM with the lateral segregation (i) of high Tm lipids and cholesterol in a Lo phase for both TTm and (ii) of high Tm lipids in a gel phase for Tglobules during processing and digestion. PMID:26988511

  6. LOOKING INTO THE HEARTS OF BOK GLOBULES: MILLIMETER AND SUBMILLIMETER CONTINUUM IMAGES OF ISOLATED STAR-FORMING CORES

    SciTech Connect

    Launhardt, R.; Henning, Th.; Khanzadyan, T.; Schmalzl, M.; Wolf, S.; Nutter, D.; Ward-Thompson, D.; Bourke, T. L.; Zylka, R.

    2010-05-15

    We present the results of a comprehensive infrared, submillimeter, and millimeter continuum emission study of isolated low-mass star-forming cores in 32 Bok globules, with the aim to investigate the process of star formation in these regions. The submillimeter and millimeter dust continuum emission maps together with the spectral energy distributions are used to model and derive the physical properties of the star-forming cores, such as luminosities, sizes, masses, densities, etc. Comparisons with ground-based near-infrared and space-based mid- and far-infrared images from Spitzer are used to reveal the stellar content of the Bok globules, association of embedded young stellar objects (YSOs) with the submillimeter dust cores, and the evolutionary stages of the individual sources. Submillimeter dust continuum emission was detected in 26 out of the 32 globule cores observed. For 18 globules with detected (sub)millimeter cores, we derive evolutionary stages and physical parameters of the embedded sources. We identify nine starless cores, most of which are presumably prestellar, nine Class 0 protostars, and twelve Class I YSOs. Specific source properties like bolometric temperature, core size, and central densities are discussed as a function of evolutionary stage. We find that at least two thirds (16 out of 24) of the star-forming globules studied here show evidence of forming multiple stars on scales between 1000 and 50,000 AU. However, we also find that most of these small prototstar and star groups are comprised of sources with different evolutionary stages, suggesting a picture of slow and sequential star formation in isolated globules.

  7. Ribosomal Protein P2 from apicomplexan parasite Toxoplasma gondii is intrinsically a molten globule.

    PubMed

    Mishra, Pushpa; Choudhary, Sinjan; Hosur, Ramakrishna V

    2015-01-01

    Toxoplasma gondii is an apicomplexan parasite, which causes toxoplasmosis. Toxoplasma P2 (TgP2) is a ribosomal protein and exists as supramolecular assembly with other proteins in the ribosome. It is also shown that TgP2 is involved in some extra ribosomal functions. However, till date the protein has evaded structural characterization by any of the known techniques. In this background, we report here a systematic study using a variety of biophysical techniques and NMR, under different conditions of pH and temperature, and deduce that TgP2 consists of only helices and unstructured regions, is a monomer at low pH but forms multimers at higher pH, and has intrinsically a molten globule structure. The C-terminal half is flexible and the helices are concentrated in the N-terminal half of the chain. The dynamism inherent to the molten globule structure may have functional implications for its extra-ribosomal functions. which is contrast to that of human P2. PMID:25866913

  8. N-15-Rich Organic Globules in a Cluster IDP and the Bells CM2 Chondrite

    NASA Technical Reports Server (NTRS)

    Messenger, S.; Nakamura-Messenger, K.; Keller, Lindsay P.

    2008-01-01

    Organic matter in primitive meteorites and chondritic porous interplanetary dust particles (CP IDPs) is commonly enriched in D/H and 15N/14N relative to terrestrial values [1-3]. These anomalies are ascribed to the partial preservation of presolar cold molecular cloud material [1]. Some meteorites and IDPs contain m-size inclusions with extreme H and N isotopic anomalies [2-4], possibly due to preserved pristine primordial organic grains. We recently showed that the in the Tagish Lake meteorite, the principle carriers of these anomalies are sub- m, hollow organic globules [5]. The globules likely formed by photochemical processing of organic ices in a cold molecular cloud or the outermost regions of the protosolar disk [5]. We proposed that similar materials should be common among primitive meteorites, IDPs, and comets. Similar objects have been observed in organic extracts of carbonaceous chondrites [6-8], however their N and H isotopic compositions are generally unknown. Bulk H and N isotopic compositions may indicate which meteorites best preserve interstellar organic compounds. Thus, we selected the Bells CM2 carbonaceous chondrites for study based on its large bulk 15N (+335 %) and D (+990 %) [9].

  9. Existence of molten globule state in homocysteine-induced protein covalent modifications.

    PubMed

    Kumar, Tarun; Sharma, Gurumayum Suraj; Singh, Laishram Rajendrakumar

    2014-01-01

    Homocysteine thiolactone is a toxic metabolite produced from homocysteine by amino-acyl t-RNA synthetase in error editing reaction. The basic cause of toxicity of homocysteine thiolactone is believed to be due to the adduct formation with lysine residues (known as protein N-homocysteinylation) leading to protein aggregation and loss of enzyme function. There was no data available until now that showed the effect of homocysteine thiolactone on the native state structural changes that led to aggregate formation. In the present study we have investigated the time dependent structural changes due to homocysteine thiolactone induced modifications on three different proteins having different physico-chemical properties (cytochrome-c, lysozyme and alpha lactalbumin). We discovered that N-homocysteinylation leads to the formation of molten globule state--an important protein folding intermediate in the protein folding pathway. We also found that the formation of the molten globule state might be responsible for the appearance of aggregate formation. The study indicates the importance of protein folding intermediate state in eliciting the homocysteine thiolactone toxicity. PMID:25405350

  10. On urea's ability to stabilize the globule state of poly(N-isopropylacrylamide).

    PubMed

    Pica, Andrea; Graziano, Giuseppe

    2016-06-01

    Experimental measurements have shown that urea decreases the temperature of the coil-to-globule collapse transition of poly(N-isopropylacrylamide), whereas tetramethylurea increases the collapse temperature [J. Am. Chem. Soc., 2009, 131, 9304]. These data indicate that urea is a stabilizing agent of the globule state in contrast to its denaturing action towards globular proteins. The effect of urea and tetramethylurea on the conformational stability of poly(N-isopropylacrylamide) is investigated by means of the theoretical approach developed to explain the existence of cold denaturation [Phys. Chem. Chem. Phys., 2010, 12, 14245; Phys. Chem. Chem. Phys., 2014, 16, 21755], and already used to rationalize the effect of sodium salts on the collapse temperature [Phys. Chem. Chem. Phys., 2015, 17, 27750]. It is necessary to take into account the delicate trade-off between the increase in the magnitude of the solvent-excluded volume effect caused by urea and tetramethylurea addition to water, and the increase in the magnitude of the energetic interactions among the poly(N-isopropylacrylamide) surface and water and co-solvent molecules. PMID:27171496

  11. Thermodynamic and structural properties of the acid molten globule state of horse cytochrome C.

    PubMed

    Nakamura, Shigeyoshi; Seki, Yasutaka; Katoh, Etsuko; Kidokoro, Shun-ichi

    2011-04-19

    To understand the stabilization, folding, and functional mechanisms of proteins, it is very important to understand the structural and thermodynamic properties of the molten globule state. In this study, the global structure of the acid molten globule state, which we call MG1, of horse cytochrome c at low pH and high salt concentrations was evaluated by solution X-ray scattering (SXS), dynamic light scattering, and circular dichroism measurements. MG1 was globular and slightly (3%) larger than the native state, N. Calorimetric methods, such as differential scanning calorimetry and isothermal acid-titration calorimetry, were used to evaluate the thermodynamic parameters in the transitions of N to MG1 and MG1 to denatured state D of horse cytochrome c. The heat capacity change, ΔC(p), in the N-to-MG1 transition was determined to be 2.56 kJ K(-1) mol(-1), indicating the increase in the level of hydration in the MG1 state. Moreover, the intermediate state on the thermal N-to-D transition of horse cytochrome c at pH 4 under low-salt conditions showed the same structural and thermodynamic properties of the MG1 state in both SXS and calorimetric measurements. The Gibbs free energy changes (ΔG) for the N-to-MG1 and N-to-D transitions at 15 °C were 10.9 and 42.2 kJ mol(-1), respectively. PMID:21388230

  12. Fitting a Turbulent Cloud Model to CO Observations of Starless Bok Globules

    NASA Astrophysics Data System (ADS)

    Hegmann, M.; Hengel, C.; Röllig, M.; Kegel, W. H.

    We present observations of five starless Bok globules in transitions of 12CO (J=2-1 and {J=3-2}), 13CO (J=2-1), and C18O (J=2-1) which have been obtained at the Heinrich-Hertz-Telescope. For an analysis of the data we use the model of Kegel et al. (see e.g. Piehler & Kegel 1995, A&A 297, 841; Hegmann & Kegel 2000, A&A 359, 405) which describes an isothermal sphere stabilized by turbulent and thermal pressure. This approach deals with the full NLTE radiative transfer problem and accounts for a turbulent velocity field with finite correlation length. By a comparison of observed and calculated line profiles we are able not only to determine the kinetic temperature, hydrogen density and CO coloumn density of the globules, but also to study the properties of the turbulent velocity field, i.e. the variance of its one-point-distribution and its correlation length. We consider our model to be an alternative tool for the evaluation of molecular lines emitted by molecular clouds. The model assumptions are certainly closer to reality than the assumptions behind the standard evaluation models, as for example the LVG model. Our current study shows that that the results obtained from our model can differ significantly from those obtained from a LVG analysis.

  13. Data from proteomic characterization and comparison of mammalian milk fat globule proteomes by iTRAQ analysis.

    PubMed

    Yang, Yongxin; Zheng, Nan; Zhao, Xiaowei; Zhang, Yangdong; Han, Rongwei; Ma, Lu; Zhao, Shengguo; Li, Songli; Guo, Tongjun; Wang, Jiaqi

    2015-06-01

    Milk fat globules memebrane (MFGM)-enriched proteomes from Holstein, Jersey, yak, buffalo, goat, camel, horse, and human were extracted and identified by an iTRAQ quantification proteomic approach. Proteomes data were analyzed by bioinformatic and multivariate statistical analysis and used to present the characteristic traits of the MFGM proteins among the studied mammals. The data of this study are also related to the research article "Proteomic characterization and comparison of mammalian milk fat globule proteomes by iTRAQ analysis" in the Journal of Proteomics [1]. PMID:26217709

  14. [Study of circulating fatty globules by filtration of the serum in primary osteonecrosis of the femoral head].

    PubMed

    Roux, H; Serratrice, G; Vovan, L; Savidan-Imbert

    1979-12-01

    The authors carried out in a group of 21 aseptic osteonecroses of the femoral head, a study of circulating fatty globules using a filtering technique on a millipore filter. 7 of these patients showed a normal lipid count, 10 had isolated increases of the prebetalipoproteins, 2 had a type IV hyperlipemia, 1 a type III hyperlipemia, and 1 a global hypolipemia. In all cases, no fatty globules were found. Decreases in the level of triglycerides and prebetalipoproteins were noted after filtering but the differences were not significant. These observations do not add support to the theory of fatty microembolism of aseptic osteonecrosis of the femoral head. PMID:531470

  15. The influence of casein haplotype on morphometric characteristics of fat globules and fatty acid composition of milk in Italian Holstein cows.

    PubMed

    Perna, Annamaria; Intaglietta, Immacolata; Simonetti, Amalia; Gambacorta, Emilio

    2016-04-01

    The aim of this work was to investigate the effect of casein haplotypes (αS1-, β-, and κ-caseins) on morphometric characteristics of fat globules and fatty acid composition of Italian Holstein milk. Casein haplotypes were determined by isoelectric focusing; milk fat globule size was measured by using a fluorescence microscope; and fatty acid profile was determined by gas chromatography. Casein haplotype significantly affected the fat globule size, the percentage incidence of each globule size class on total measured milk fat globules, and fatty acid composition. A higher incidence of smaller milk fat globules was associated with the BB-A(2)A(2)-BB genotype (αS1-, β-, and κ-casein haplotypes, respectively), whereas small globules were not detected in BB-A(2)A(1)-AA milk, but that milk had the highest percentage of large globules. A higher content of monounsaturated fatty acids was associated with the BB-A(2)A(2)-AB genotype, whereas higher contents of conjugated linoleic acid and docosahexaenoic acid were detected in BB-A(1)A(1)-AA milk. Our results indicate that casein haplotype could affect fat characteristics and, therefore, the nutritional and technological quality of milk. PMID:26874415

  16. Evidence for a Noachian-Aged Ephemeral Lake in Gusev Crater, Mars

    NASA Technical Reports Server (NTRS)

    Ruff, S. W.; Niles, P. B.; Alfano, F.; Clarke, A. B.

    2014-01-01

    Gusev crater was selected as the landing site for the Spirit rover because of the likelihood that it contained an ancient lake. Although outcrops rich in Mg-Fe carbonate dubbed Comanche were discovered in the Noachian-aged Columbia Hills, they were inferred to result from volcanic hydrothermal activity. Spirit encountered other mineral and chemical indicators of aqueous activity, but none was recognized as definitive evidence for a former lake in part because none was associated with obvious lacustrine sedimentary deposits. However, water discharge into Martian crater basins like Gusev may have been episodic, producing only small amounts of sediment and shallow ephemeral lakes. Evaporative precipitation from such water bodies has been suggested as a way of producing the Mg- and Fe-rich carbonates found in ALH84001 and carbonates and salts in some nakhlites a hypothesis we examine for the Comanche carbonate.

  17. Coupled Evolution of the Martian Atmosphere and Crust Through Geologic Time

    NASA Astrophysics Data System (ADS)

    Hutchins, Kevin Sean

    1998-09-01

    This dissertation investigates the coupled evolution of the Martian atmosphere and crust throughout geologic time and the implications for Martian sample analysis and exobiology. Abundant geological and atmospheric evidence suggests that Mars has changed significantly throughout time. Removal of volatiles from the atmosphere may have been the trigger for the dramatic transition from that scenario to the present cold, harsh climate. Previous modeling work has shown that loss to space enriches the residual atmosphere in the heavier isotopes. Furthermore, stable isotope measurements from secondary mineral deposits within the Martian meteorites indicate exchange with an isotopically-enriched atmosphere. To investigate the Martian climate history, we developed an atmospheric evolution model for argon and neon considering a mass balance between the mantle, atmosphere, and loss to space by sputtering. Sputtering loss is particularly relevant for noble gases which have few mechanisms of escape. Due to substantial loss, our model is only capable of explaining <25% and <2.5% of the atmospheric abundance of argon and neon, respectively. Thus, sources of volatiles are required in addition to volcanic outgassing. We examined the impact of a Martian paleomagnetic field on sputtering loss. A strong magnetic field could limit sputtering loss by deflecting the solar wind around the upper atmosphere. We found that a magnetic field that persists until 1-2 Ga could affect the loss of light noble gases from the atmosphere. Nonetheless, our model predicts additional sources to balance the atmospheric volatile budgets. Therefore, we investigated outgassing from the Martian crust via groundwater circulation. We found that a crustal reservoir 5-25 km thick could satisfy the atmospheric argon budget. Recently, putative evidence of life has been purported for the Martian meteorite ALH84001. We examined the stable isotope measurements from carbonate and organic deposits found in ALH84001. Due

  18. Removal of milk fat globules from whey protein concentrate 34% to prepare clear and heat-stable protein dispersions.

    PubMed

    Liu, Gang; Zhong, Qixin

    2014-10-01

    Whey protein concentrates (WPC) are low-cost protein ingredients, but their application in transparent ready-to-drink beverages is limited due to turbidity caused by fat globules and heat instability. In this work, fat globules were removed from WPC 34% (WPC-34) to prepare heat-stable ingredients via the Maillard reaction. The removal of fat globules by acid precipitation and centrifugation was observed to be the most complete at pH 4.0, and the loss of protein was caused by micrometer-sized fat globules and protein aggregates. Spray-dried powder prepared from the transparent supernatant was glycated at 130°C for 20 and 30min or 60°C for 24 and 48h. The 2 groups of samples had comparable heat stability and degree of glycation, evaluated by free amino content and analytical ultracentrifugation, but high-temperature, short-time treatment reduced the color formation during glycation. Therefore, WPC-34 can be processed for application in transparent beverages. PMID:25108870

  19. Comparative proteomics of milk fat globule membrane in goat colostrum and mature milk.

    PubMed

    Lu, Jing; Liu, Lu; Pang, Xiaoyang; Zhang, Shuwen; Jia, Zhenhu; Ma, Changlu; Zhao, Lili; Lv, Jiaping

    2016-10-15

    As an important nutrient source in large area of world, the composition and nutritional value of goat milk are not well deliberated. Detailed annotation of protein composition is essential to address the physiological and nutritional value of goat milk. In the present study, 423 colostrum and mature goat milk fat globule membrane (MFGM) proteins were identified. The abundance of 189 proteins was significantly different between colostrums and mature milk MFGM. The acute phase proteins were higher in colostrums MFGM than those in mature milk MFGM which protected newborns at the beginning of life. Proteins related to synthesis and secretion were conserved through lactation to ensure the milk production. Of note, long term depression (LTD) proteins were observed in colostrum and mature milk MFGM. Milk LTD proteins could be potential biomarkers for diagnosis of lactation related depressive syndromes and should be taken into considerations of their effects on newborns. PMID:27173528

  20. Radiation-MHD Simulations of Pillars and Globules in HII Regions

    NASA Astrophysics Data System (ADS)

    Mackey, J.

    2012-07-01

    Implicit and explicit raytracing-photoionisation algorithms have been implemented in the author's radiation-magnetohydrodynamics code. The algorithms are described briefly and their efficiency and parallel scaling are investigated. The implicit algorithm is more efficient for calculations where ionisation fronts have very supersonic velocities, and the explicit algorithm is favoured in the opposite limit because of its better parallel scaling. The implicit method is used to investigate the effects of initially uniform magnetic fields on the formation and evolution of dense pillars and cometary globules at the boundaries of HII regions. It is shown that for weak and medium field strengths an initially perpendicular field is swept into alignment with the pillar during its dynamical evolution, matching magnetic field observations of the ‘Pillars of Creation’ in M16. A strong perpendicular magnetic field remains in its initial configuration and also confines the photoevaporation flow into a bar-shaped, dense, ionised ribbon which partially shields the ionisation front.

  1. Role of milk fat globule-epidermal growth factor 8 in osteoimmunology.

    PubMed

    Sinningen, Kathrin; Thiele, Sylvia; Hofbauer, Lorenz C; Rauner, Martina

    2016-01-01

    Milk fat globule-epidermal growth factor 8 (MFG-E8) is a glycoprotein that is abundantly expressed in various tissues and has a pivotal role in the phagocytic clearance of apoptotic cells. However, MFG-E8 has also gained significant attention because of its wide range of functions in autoimmunity, inflammation and tissue homeostasis. More recently, MFG-E8 has been identified as a critical regulator of bone homeostasis, being expressed in both, osteoblasts and osteoclasts. In addition, it was shown that MFG-E8 fulfils an active role in modulating inflammatory processes, suggesting an anti-inflammatory role of MFG-E8 and proposing it as a novel therapeutic target for inflammatory diseases. This concise review focusses on the expression and regulation of MFG-E8 in the context of inflammatory bone diseases, highlights its role in the pathophysiology of osteoimmune diseases and discusses the therapeutic potential of MFG-E8. PMID:27579162

  2. Coexistence of coil and globule domains within a single confined DNA chain

    PubMed Central

    Sung, Baeckkyoung; Leforestier, Amélie; Livolant, Françoise

    2016-01-01

    The highly charged DNA chain may be either in an extended conformation, the coil, or condensed into a highly dense and ordered structure, the toroid. The transition, also called collapse of the chain, can be triggered in different ways, for example by changing the ionic conditions of the solution. We observe individual DNA molecules one by one, kept separated and confined inside a protein shell (the envelope of a bacterial virus, 80 nm in diameter). For subcritical concentrations of spermine (4+), part of the DNA is condensed and organized in a toroid and the other part of the chain remains uncondensed around. Two states coexist along the same DNA chain. These ‘hairy’ globules are imaged by cryo-electron microscopy. We describe the global conformation of the chain and the local ordering of DNA segments inside the toroid. PMID:26704970

  3. Properties of Protostars in the Elephant Trunk in the Globule IC 1396A

    NASA Astrophysics Data System (ADS)

    Reach, William T.; Faied, Dohy; Rho, Jeonghee; Boogert, Adwin; Tappe, Achim; Jarrett, Thomas H.; Morris, Patrick; Cambrésy, Laurent; Palla, Francesco; Valdettaro, Riccardo

    2009-01-01

    Extremely red objects, identified in the early Spitzer Space Telescope observations of the bright-rimmed globule IC 1396A and photometrically classified as Class I protostars and Class II T Tauri stars based on their mid-infrared (mid-IR) colors, were spectroscopically observed at 5.5-38 μm (Spitzer Infrared Spectrograph), at the 22 GHz water maser frequency (National Radio Astronomy Observatory Green Bank Telescope), and in the optical (Palomar Hale 5 m) to confirm their nature and further elucidate their properties. The sources photometrically identified as Class I, including IC 1396A:α, γ, δ, epsilon, and ζ, are confirmed as objects dominated by accretion luminosity from dense envelopes, with accretion rates 1-10 × 10-6 M sun yr-1 and present stellar masses 0.1-2 M sun. The Class I sources have extremely red continua, still rising at 38 μm, with a deep silicate absorption at 9-11 μm, weaker silicate absorption around 18 μm, and weak ice features including CO2 at 15.2 μm and H2O at 6 μm. The ice/silicate absorption ratio in the envelope is exceptionally low for the IC 1396A protostars, compared to those in nearby star-forming regions, suggesting that the envelope chemistry is altered by the radiation field or globule pressure. Only one 22 GHz water maser was detected in IC 1396A; it is coincident with a faint mid-IR source, offset from near the luminous Class I protostar IC 1396A:γ. The maser source, IC 1396A:γ b , has luminosity less than 0.1 L sun, the first H2O maser from such a low-luminosity object. Two near-infrared (NIR) H2 knots on opposite sides of IC 1396A:γ reveal a jet, with an axis clearly distinct from the H2O maser of IC 1396A:γ b . The objects photometrically classified as Class II, including IC 1396A:β, θ, Two Micron All Sky Survey (2MASS)J 21364964+5722270, 2MASSJ 21362507+5727502, LkHα 349c, Tr 37 11-2146, and Tr 37 11-2037, are confirmed as stars with warm, luminous disks, with a silicate emission feature at 9-11 μm, and

  4. Clinical Benefits of Milk Fat Globule Membranes for Infants and Children.

    PubMed

    Hernell, Olle; Timby, Niklas; Domellöf, Magnus; Lönnerdal, Bo

    2016-06-01

    The milk fat globule membrane (MFGM) in breast milk contains many bioactive components. Infant formulas traditionally have been devoid of the MFGM fraction, but dairy technology now has made the addition of bovine MFGM technically feasible. We identified 6 double-blinded randomized controlled trials exploring the effects of MFGM supplementation on the diets of infants or children. Results suggest that supplementation is safe and indicate positive effects on both neurodevelopment and defense against infections. MFGM supplementation of infant formula may narrow the gap in cognitive performance and infection rates between breastfed and formula-fed infants. Because of the small number of studies and the heterogeneity of interventions, more high-quality double-blinded randomized controlled trials are needed, with well characterized and clearly defined MFGM fractions, before firm conclusions on the effects of MFGM supplementation on the health and development of infants can be drawn. PMID:27234413

  5. Short communication: Milk fat globule membrane as a potential delivery system for liposoluble nutrients.

    PubMed

    Bezelgues, J-B; Morgan, F; Palomo, G; Crosset-Perrotin, L; Ducret, P

    2009-06-01

    A soft physical process was used to extract and purified bovine milk fat globule membrane (MFGM) fractions on a pilot scale. Oil-in-water emulsions enriched with alpha-tocopherol and lycopene were then prepared and stabilized with the extracted MFGM fraction and conventional milk protein concentrates (i.e., whey proteins, caseinate). A protocol of in vitro digestion was set up to evaluate the bioaccessibility of the tocopherol and lycopene in the different emulsions. Bioaccessibility was defined as the capacity of liposoluble compounds to be transferred into mixed micelles formed during the digestion process. Results showed that the accumulation of the tocopherol and lycopene into mixed micelles in MFGM-stabilized emulsions was around 2-fold greater than in emulsions stabilized with conventional milk proteins. This result confirms the potential use of MFGM-enriched ingredients as delivery systems of liposoluble nutrients in food formulations. PMID:19447983

  6. Capturing molten globule state of α-lactalbumin through constant pH molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Nicholus; Rani, Pooja; Biswas, Parbati

    2013-03-01

    The recently developed methods of constant pH molecular dynamics directly captures the correlation between protonation and conformation to probe protein structure, function, and dynamics. In this work, we investigate the effect of pH on the conformational properties of the protein human α-lactalbumin. Constant pH simulations at both acidic and alkaline medium indicate the formation of the molten globule state, which is in accordance with the previous experimental observations (especially, in acidic medium). The size of the protein measured by its radius of gyration (RG) exhibits a marked increase in both acidic and alkaline medium, which matches with the corresponding experimentally observed value of RG found in the molten globule. The probability of native contacts is also considerably reduced at acidic and basic pH as compared to that of native structure crystallized at neutral pH. The mean fractal dimension D2 of the protein records a sharp increase in basic medium as compared to those in neutral and acidic solutions implying a significant pH induced conformational change. The mean square fluctuations of all residues of the entire protein are found to increase by several folds in both acidic and basic medium, which may be correlated with the normalized solvent accessibility of the residues indicating role of solvent accessible surface area on protein internal dynamics. The helices comprising the α-domain of the protein are moderately preserved in the acidic and alkaline pH. However, the β-sheet structures present in the β-domain are completely disrupted in both acidic as well as basic pH.

  7. Differential role of molten globule and protein folding in distinguishing unique features of botulinum neurotoxin.

    PubMed

    Kumar, Raj; Kukreja, Roshan V; Cai, Shuowei; Singh, Bal R

    2014-06-01

    Botulinum neurotoxins (BoNTs) are proteins of great interest not only because of their extreme toxicity but also paradoxically for their therapeutic applications. All the known serotypes (A-G) have varying degrees of longevity and potency inside the neuronal cell. Differential chemical modifications such as phosphorylation and ubiquitination have been suggested as possible mechanisms for their longevity, but the molecular basis of the longevity remains unclear. Since the endopeptidase domain (light chain; LC) of toxin apparently survives inside the neuronal cells for months, it is important to examine the structural features of this domain to understand its resistance to intracellular degradation. Published crystal structures (both botulinum neurotoxins and endopeptidase domain) have not provided adequate explanation for the intracellular longevity of the domain. Structural features obtained from spectroscopic analysis of LCA and LCB were similar, and a PRIME (PReImminent Molten Globule Enzyme) conformation appears to be responsible for their optimal enzymatic activity at 37°C. LCE, on the other hand, was although optimally active at 37°C, but its active conformation differed from the PRIME conformation of LCA and LCB. This study establishes and confirms our earlier finding that an optimally active conformation of these proteins in the form of PRIME exists for the most poisonous poison, botulinum neurotoxin. There are substantial variations in the structural and functional characteristics of these active molten globule related structures among the three BoNT endopeptidases examined. These differential conformations of LCs are important in understanding the fundamental structural features of proteins, and their possible connection to intracellular longevity could provide significant clues for devising new countermeasures and effective therapeutics. PMID:24568862

  8. The protein and lipid composition of the membrane of milk fat globules depends on their size.

    PubMed

    Lu, Jing; Argov-Argaman, Nurit; Anggrek, Jeni; Boeren, Sjef; van Hooijdonk, Toon; Vervoort, Jacques; Hettinga, Kasper Arthur

    2016-06-01

    In bovine milk, fat globules (MFG) have a heterogeneous size distribution with diameters ranging from 0.1 to 15 µm. Although efforts have been made to explain differences in lipid composition, little is known about the protein composition of MFG membranes (MFGM) in different sizes of MFG. In this study, protein and lipid analyses were combined to study MFG formation and secretion. Two different sized MFG fractions (7.6±0.9 µm and 3.3±1.2 µm) were obtained by centrifugation. The protein composition of MFGM in the large and small MFG fractions was compared using mass-spectrometry-based proteomics techniques. The lipid composition and fatty acid composition of MFG was determined using HPLC-evaporative light-scattering detector and gas chromatography, respectively. Two frequently studied proteins in lipid droplet biogenesis, perilipin-2 and TIP47, were increased in the large and small MFG fractions, respectively. In the large MFG fraction, besides perilipin-2, cytoplasmic vesicle proteins (heat shock proteins, 14-3-3 proteins, and Rabs), microfilaments and intermediate filament-related proteins (actin and vimentin), host defense proteins (cathelicidins), and phosphatidylinositol were higher in concentration. On the other hand, cholesterol synthesis enzymes [lanosterol synthase and sterol-4-α-carboxylate 3-dehydrogenase (decarboxylating)], cholesterol, unsaturated fatty acids, and phosphatidylethanolamine were, besides TIP47, higher in concentration in the small MFG fraction. These results suggest that vesicle proteins, microfilaments and intermediate filaments, cholesterol, and specific phospholipids play an important role in lipid droplet growth, secretion, or both. The observations from this study clearly demonstrated the difference in protein and lipid composition between small and large MFG fractions. Studying the role of these components in more detail in future experiments may lead to a better understanding of fat globule formation and secretion. PMID

  9. Theoretical study of solvent effects on the coil-globule transition

    NASA Astrophysics Data System (ADS)

    Polson, James M.; Opps, Sheldon B.; Abou Risk, Nicholas

    2009-06-01

    The coil-globule transition of a polymer in a solvent has been studied using Monte Carlo simulations of a single chain subject to intramolecular interactions as well as a solvent-mediated effective potential. This solvation potential was calculated using several different theoretical approaches for two simple polymer/solvent models, each employing hard-sphere chains and hard-sphere solvent particles as well as attractive square-well potentials between some interaction sites. For each model, collapse is driven by variation in a parameter which changes the energy mismatch between monomers and solvent particles. The solvation potentials were calculated using two fundamentally different methodologies, each designed to predict the conformational behavior of polymers in solution: (1) the polymer reference interaction site model (PRISM) theory and (2) a many-body solvation potential (MBSP) based on scaled particle theory introduced by Grayce [J. Chem. Phys. 106, 5171 (1997)]. For the PRISM calculations, two well-studied solvation monomer-monomer pair potentials were employed, each distinguished by the closure relation used in its derivation: (i) a hypernetted-chain (HNC)-type potential and (ii) a Percus-Yevick (PY)-type potential. The theoretical predictions were each compared to results obtained from explicit-solvent discontinuous molecular dynamics simulations on the same polymer/solvent model systems [J. Chem. Phys. 125, 194904 (2006)]. In each case, the variation in the coil-globule transition properties with solvent density is mostly qualitatively correct, though the quantitative agreement between the theory and prediction is typically poor. The HNC-type potential yields results that are more qualitatively consistent with simulation. The conformational behavior of the polymer upon collapse predicted by the MBSP approach is quantitatively correct for low and moderate solvent densities but is increasingly less accurate for higher densities. At high solvent densities

  10. Isotope ratios of H, C, and O in CO2 and H2O of the martian atmosphere.

    PubMed

    Webster, Chris R; Mahaffy, Paul R; Flesch, Gregory J; Niles, Paul B; Jones, John H; Leshin, Laurie A; Atreya, Sushil K; Stern, Jennifer C; Christensen, Lance E; Owen, Tobias; Franz, Heather; Pepin, Robert O; Steele, Andrew; Achilles, Cherie; Agard, Christophe; Alves Verdasca, José Alexandre; Anderson, Robert; Anderson, Ryan; Archer, Doug; Armiens-Aparicio, Carlos; Arvidson, Ray; Atlaskin, Evgeny; Aubrey, Andrew; Baker, Burt; Baker, Michael; Balic-Zunic, Tonci; Baratoux, David; Baroukh, Julien; Barraclough, Bruce; Bean, Keri; Beegle, Luther; Behar, Alberto; Bell, James; Bender, Steve; Benna, Mehdi; Bentz, Jennifer; Berger, Gilles; Berger, Jeff; Berman, Daniel; Bish, David; Blake, David F; Blanco Avalos, Juan J; Blaney, Diana; Blank, Jen; Blau, Hannah; Bleacher, Lora; Boehm, Eckart; Botta, Oliver; Böttcher, Stephan; Boucher, Thomas; Bower, Hannah; Boyd, Nick; Boynton, Bill; Breves, Elly; Bridges, John; Bridges, Nathan; Brinckerhoff, William; Brinza, David; Bristow, Thomas; Brunet, Claude; Brunner, Anna; Brunner, Will; Buch, Arnaud; Bullock, Mark; Burmeister, Sönke; Cabane, Michel; Calef, Fred; Cameron, James; Campbell, John; Cantor, Bruce; Caplinger, Michael; Caride Rodríguez, Javier; Carmosino, Marco; Carrasco Blázquez, Isaías; Charpentier, Antoine; Chipera, Steve; Choi, David; Clark, Benton; Clegg, Sam; Cleghorn, Timothy; Cloutis, Ed; Cody, George; Coll, Patrice; Conrad, Pamela; Coscia, David; Cousin, Agnès; Cremers, David; Crisp, Joy; Cros, Alain; Cucinotta, Frank; d'Uston, Claude; Davis, Scott; Day, Mackenzie; de la Torre Juarez, Manuel; DeFlores, Lauren; DeLapp, Dorothea; DeMarines, Julia; DesMarais, David; Dietrich, William; Dingler, Robert; Donny, Christophe; Downs, Bob; Drake, Darrell; Dromart, Gilles; Dupont, Audrey; Duston, Brian; Dworkin, Jason; Dyar, M Darby; Edgar, Lauren; Edgett, Kenneth; Edwards, Christopher; Edwards, Laurence; Ehlmann, Bethany; Ehresmann, Bent; Eigenbrode, Jen; Elliott, Beverley; Elliott, Harvey; Ewing, Ryan; Fabre, Cécile; Fairén, Alberto; Farley, Ken; Farmer, Jack; Fassett, Caleb; Favot, Laurent; Fay, Donald; Fedosov, Fedor; Feldman, Jason; Feldman, Sabrina; Fisk, Marty; Fitzgibbon, Mike; Floyd, Melissa; Flückiger, Lorenzo; Forni, Olivier; Fraeman, Abby; Francis, Raymond; François, Pascaline; Freissinet, Caroline; French, Katherine Louise; Frydenvang, Jens; Gaboriaud, Alain; Gailhanou, Marc; Garvin, James; Gasnault, Olivier; Geffroy, Claude; Gellert, Ralf; Genzer, Maria; Glavin, Daniel; Godber, Austin; Goesmann, Fred; Goetz, Walter; Golovin, Dmitry; Gómez Gómez, Felipe; Gómez-Elvira, Javier; Gondet, Brigitte; Gordon, Suzanne; Gorevan, Stephen; Grant, John; Griffes, Jennifer; Grinspoon, David; Grotzinger, John; Guillemot, Philippe; Guo, Jingnan; Gupta, Sanjeev; Guzewich, Scott; Haberle, Robert; Halleaux, Douglas; Hallet, Bernard; Hamilton, Vicky; Hardgrove, Craig; Harker, David; Harpold, Daniel; Harri, Ari-Matti; Harshman, Karl; Hassler, Donald; Haukka, Harri; Hayes, Alex; Herkenhoff, Ken; Herrera, Paul; Hettrich, Sebastian; Heydari, Ezat; Hipkin, Victoria; Hoehler, Tori; Hollingsworth, Jeff; Hudgins, Judy; Huntress, Wesley; Hurowitz, Joel; Hviid, Stubbe; Iagnemma, Karl; Indyk, Steve; Israël, Guy; Jackson, Ryan; Jacob, Samantha; Jakosky, Bruce; Jensen, Elsa; Jensen, Jaqueline Kløvgaard; Johnson, Jeffrey; Johnson, Micah; Johnstone, Steve; Jones, Andrea; Joseph, Jonathan; Jun, Insoo; Kah, Linda; Kahanpää, Henrik; Kahre, Melinda; Karpushkina, Natalya; Kasprzak, Wayne; Kauhanen, Janne; Keely, Leslie; Kemppinen, Osku; Keymeulen, Didier; Kim, Myung-Hee; Kinch, Kjartan; King, Penny; Kirkland, Laurel; Kocurek, Gary; Koefoed, Asmus; Köhler, Jan; Kortmann, Onno; Kozyrev, Alexander; Krezoski, Jill; Krysak, Daniel; Kuzmin, Ruslan; Lacour, Jean Luc; Lafaille, Vivian; Langevin, Yves; Lanza, Nina; Lasue, Jeremie; Le Mouélic, Stéphane; Lee, Ella Mae; Lee, Qiu-Mei; Lees, David; Lefavor, Matthew; Lemmon, Mark; Lepinette Malvitte, Alain; Léveillé, Richard; Lewin-Carpintier, Éric; Lewis, Kevin; Li, Shuai; Lipkaman, Leslie; Little, Cynthia; Litvak, Maxim; Lorigny, Eric; Lugmair, Guenter; Lundberg, Angela; Lyness, Eric; Madsen, Morten; Maki, Justin; Malakhov, Alexey; Malespin, Charles; Malin, Michael; Mangold, Nicolas; Manhes, Gérard; Manning, Heidi; Marchand, Geneviève; Marín Jiménez, Mercedes; Martín García, César; Martin, Dave; Martin, Mildred; Martínez-Frías, Jesús; Martín-Soler, Javier; Martín-Torres, F Javier; Mauchien, Patrick; Maurice, Sylvestre; McAdam, Amy; McCartney, Elaina; McConnochie, Timothy; McCullough, Emily; McEwan, Ian; McKay, Christopher; McLennan, Scott; McNair, Sean

    2013-07-19

    Stable isotope ratios of H, C, and O are powerful indicators of a wide variety of planetary geophysical processes, and for Mars they reveal the record of loss of its atmosphere and subsequent interactions with its surface such as carbonate formation. We report in situ measurements of the isotopic ratios of D/H and (18)O/(16)O in water and (13)C/(12)C, (18)O/(16)O, (17)O/(16)O, and (13)C(18)O/(12)C(16)O in carbon dioxide, made in the martian atmosphere at Gale Crater from the Curiosity rover using the Sample Analysis at Mars (SAM)'s tunable laser spectrometer (TLS). Comparison between our measurements in the modern atmosphere and those of martian meteorites such as ALH 84001 implies that the martian reservoirs of CO2 and H2O were largely established ~4 billion years ago, but that atmospheric loss or surface interaction may be still ongoing. PMID:23869013

  11. Evidence for life in a martian meteorite?

    PubMed

    McSween, H Y

    1997-07-01

    The controversial hypothesis that the ALH84001 meteorite contains relics of ancient martian life has spurred new findings, but the question has not yet been resolved. Organic matter probably results, at least in part, from terrestrial contamination by Antarctic ice meltwater. The origin of nanophase magnetites and sulfides, suggested, on the basis of their sizes and morphologies, to be biogenic remains contested, as does the formation temperature of the carbonates that contain all of the cited evidence for life. The reported nonfossils may be magnetite whiskers and platelets, probably grown from a vapor. New observations, such as the possible presence of biofilms and shock metamorphic effects in the carbonates, have not yet been evaluated. Regardless of the ultimate conclusion, this controversy continues to help define strategies and sharpen tools that will be required for a Mars exploration program focused on the search for life. PMID:11541665

  12. Globules and pillars in Cygnus X. I. Herschel far-infrared imaging of the Cygnus OB2 environment

    NASA Astrophysics Data System (ADS)

    Schneider, N.; Bontemps, S.; Motte, F.; Blazere, A.; André, Ph.; Anderson, L. D.; Arzoumanian, D.; Comerón, F.; Didelon, P.; Di Francesco, J.; Duarte-Cabral, A.; Guarcello, M. G.; Hennemann, M.; Hill, T.; Könyves, V.; Marston, A.; Minier, V.; Rygl, K. L. J.; Röllig, M.; Roy, A.; Spinoglio, L.; Tremblin, P.; White, G. J.; Wright, N. J.

    2016-06-01

    The radiative feedback of massive stars on molecular clouds creates pillars, globules and other features at the interface between the H II region and molecular cloud. Optical and near-infrared observations from the ground as well as with the Hubble or Spitzer satellites have revealed numerous examples of such cloud structures. We present here Herschel far-infrared observations between 70 μm and 500 μm of the immediate environment of the rich Cygnus OB2 association, performed within the Herschel imaging survey of OB Young Stellar objects (HOBYS) program. All of the observed irradiated structures were detected based on their appearance at 70 μm, and have been classified as pillars, globules, evaporating gasous globules (EGGs), proplyd-like objects, and condensations. From the 70 μm and 160 μm flux maps, we derive the local far-ultraviolet (FUV) field on the photon dominated surfaces. In parallel, we use a census of the O-stars to estimate the overall FUV-field, that is 103-104 G0 (Habing field) close to the central OB cluster (within 10 pc) and decreases down to a few tens G0, in a distance of 50 pc. From a spectral energy distribution (SED) fit to the four longest Herschel wavelengths, we determine column density and temperature maps and derive masses, volume densities and surface densities for these structures. We find that the morphological classification corresponds to distinct physical properties. Pillars and globules are massive (~500 M⊙) and large (equivalent radius r ~ 0.6 pc) structures, corresponding to what is defined as "clumps" for molecular clouds. EGGs and proplyd-likeobjects are smaller (r ~ 0.1 and 0.2 pc) and less massive (~10 and ~30 M⊙). Cloud condensations are small (~0.1 pc), have an average mass of 35 M⊙, are dense (~6 × 104 cm-3), and can thus be described as molecular cloud "cores". All pillars and globules are oriented toward the Cyg OB2 association center and have the longest estimated photoevaporation lifetimes, a few million

  13. Breakdown of interlocking domains may contribute to formation of membranous globules and lens opacity in ephrin-A5(-/-) mice.

    PubMed

    Biswas, Sondip; Son, Alexander; Yu, Qili; Zhou, Renping; Lo, Woo-Kuen

    2016-04-01

    Ephrin-A5, a ligand of the Eph family of receptor tyrosine kinases, plays a key role in lens fiber cell packing and cell-cell adhesion, with approximately 87% of ephrin-A5(-/-) mice develop nuclear cataracts. Here, we investigated the extensive formation of light-scattering globules associated with breakdown of interlocking protrusions during lens opacification in ephrin-A5(-/-) mice. Lenses from wild-type (WT) and ephrin-A5(-/-) mice between 2 and 21 weeks old were studied with light and electron microscopy, immunofluorescence labeling, freeze-fracture TEM and filipin cytochemistry for membrane cholesterol detection. Lens opacities with various densities were first observed in ephrin-A5(-/-) mice at around 60 days old. Dense cataracts in the mutant lenses were seen primarily in the nuclear region surrounded by transparent cortices from all eyes examined. We confirmed that a majority of nuclear cataracts were dislocated posteriorly and ruptured the thinner posterior lens capsule. SEM analysis indicated that numerous interlocking protrusions and wavy ridge-and-valley membrane surfaces in deep cortical and nuclear fibers did not cause lens opacity in both transparent ephrin-A5(-/-) and WT mice. In contrast, abundant isolated membranous globules of approximately 1000 nm in size were distributed randomly along the intact fiber cells during early stage of all ephrin-A5(-/-) cataracts examined. A further examination using both SEM and TEM revealed that isolated globules were generated from the disintegrated interlocking protrusions originally located along the corners of hexagonal fiber cells. Freeze-fracture TEM further revealed the association of square-array aquaporin junctions with both isolated globules and interlocking membrane domains. This study reports for the first time that disrupted interlocking protrusions are the source of numerous large membranous globules that contribute to light scattering and nuclear cataracts in the ephrin-A5(-/-) mice. Our results

  14. Formation of meteorite hydrocarbons from thermal decomposition of siderite (FeCO 3)

    NASA Astrophysics Data System (ADS)

    McCollom, Thomas M.

    2003-01-01

    Thermal decomposition of siderite has been proposed as a source of magnetite in martian meteorites. Laboratory experiments were conducted to evaluate the possibility that this process might also result in abiotic synthesis of organic compounds. Siderite decomposition in the presence of water vapor at 300°C generated a variety of organic products dominated by alkylated and hydroxylated aromatic compounds. The results suggest that formation of magnetite by thermal decomposition of siderite on the precursor rock of the martian meteorite ALH84001 would have been accompanied by formation of organic compounds and may represent a source of extraterrestrial organic matter in the meteorite and on Mars. The results also suggest that thermal decomposition of siderite during metamorphism could account for some of the reduced carbon observed in metasedimentary rocks from the early Earth.

  15. Scanning Electron Microscopy Investigation of a Sample Depth Profile Through the Martian Meteorite Nakhla

    NASA Technical Reports Server (NTRS)

    Toporski, Jan; Steele, Andrew; Westall, Frances; McKay, David S.

    2000-01-01

    The ongoing scientific debate as to whether or not the Martian meteorite ALH84001 contained evidence of possible biogenic activities showed the need to establish consistent methods to ascertain the origin of such evidence. To distinguish between terrestrial organic material/microbial contaminants and possible indigenous microbiota within meteorites is therefore crucial. With this in mind a depth profile consisting of four samples from a new sample allocation of Martian meteorite Nakhla was investigated using scanning electron microscopy (SEM) and energy dispersive X-ray analysis. SEM imaging of freshly broken fractured chips revealed structures strongly recent terrestrial microorganisms, in some cases showing evidence of active growth. This conclusion was supported by EDX analysis, which showed the presence of carbon associated with these structures, we concluded that these structures represent recent terrestrial contaminants rather than structures indigenous to the meteorite. Page

  16. Peering Through a Martian Veil: ALHA84001 Sm-Nd Age Revisited

    NASA Technical Reports Server (NTRS)

    Nyquist, Laurence E.; Shih, Chi-Yu

    2013-01-01

    The ancient Martian orthopyroxenite ALH84001experienced a complex history of impact and aqueous alteration events. Here we summarize Sm-147-Nd-143 and Sm-146-Nd-142 analyses performed at JSC. Further, using REE data, we model the REE abundance pattern of the basaltic magma parental to ALH84001 cumulus orthopyroxene. We find the Sm-146-Nd-142 isotopic data to be consistent with isotopic evolution in material having the modeled Sm/Nd ratio from a time very close to the planet's formation to igneous crystallization of ALH84001 as inferred from the Sm-Nd studies.

  17. In vivo digestion of bovine milk fat globules: effect of processing and interfacial structural changes. II. Upper digestive tract digestion.

    PubMed

    Gallier, Sophie; Zhu, Xiang Q; Rutherfurd, Shane M; Ye, Aiqian; Moughan, Paul J; Singh, Harjinder

    2013-12-01

    The aim of this research was to study the effect of milk processing on the in vivo upper digestive tract digestion of milk fat globules. Fasted rats were serially gavaged over a 5h period with cream from raw, pasteurised, or pasteurised and homogenised milk. Only a few intact dietary proteins and peptides were present in the small intestinal digesta. Significantly (P<0.05) more longer chain (C≥10) fatty acids were present in the digesta of rats gavaged with raw (448 mg g(-1) digesta dry matter (DDM)) and homogenised creams (528 mg g(-1) DDM), as compared to pasteurised and homogenised cream (249 mg g(-1) DDM). Microscopy techniques were used to investigate the structural changes during digestion. Liquid-crystalline lamellar phases surrounding the fat globules, fatty acid soap crystals and lipid-mucin interactions were evident in all small intestinal digesta. Overall, the pasteurised and homogenised cream appeared to be digested to a greater extent. PMID:23871080

  18. Redox proteomics of fat globules unveils broad protein lactosylation and compositional changes in milk samples subjected to various technological procedures.

    PubMed

    Arena, Simona; Renzone, Giovanni; Novi, Gianfranco; Scaloni, Andrea

    2011-10-19

    The Maillard reaction between lactose and proteins occurs during thermal treatment of milk and lactosylated β-lactoglobulin, α-lactalbumin and caseins have widely been used to monitor the quality of dairy products. We recently demonstrated that a number of other whey milk proteins essential for nutrient delivery, defense against bacteria/virus and cellular proliferation become lactosylated during milk processing. The extent of their modification is associated with the harshness of product manufacturing. Since fat globule proteins are also highly important for the health-beneficial properties of milk, an evaluation of their lactosylation is crucial for a complete understanding of aliment nutritional characteristics. This is more important when milk is the unique dietary source, as in the infant diet. To this purpose, a sequential proteomic procedure involving an optimized milk fat globule (MFG) preparation/electrophoretic resolution, shot-gun analysis of gel portions for protein identification, selective trapping of lactosylated peptides by phenylboronate chromatography and their analysis by nanoLC-ESI-electron transfer dissociation (ETD) tandem MS was used for systematic characterization of fat globule proteins in milk samples subjected to various manufacturing procedures. Significant MFG protein compositional changes were observed between samples, highlighting the progressive adsorption of caseins and whey proteins on the fat globule surface as result of the technological process used. A significant lactosylation of MFG proteins was observed in ultra-high temperature sterilized and powdered for infant nutrition milk preparations, which well paralleled with the harshness of thermal treatment. Globally, this study allowed the identification of novel 157 non-redundant modification sites and 35 MFG proteins never reported so far as being lactosylated, in addition to the 153 ones ascertained here as present on other 21 MFG-adsorbed proteins whose nature was already

  19. Detection of Bacterial Magnetofossils with Ferromagnetic Resonance and Rock Magnetic Techniques

    NASA Astrophysics Data System (ADS)

    Kirschvink, J. L.; Kim, S.; Weiss, B.

    2001-12-01

    Intracellular biomineralization of magnetite is a biochemical process used by members of the Bacteria, Protist, and Animal kingdoms, and the fossil remains of this process on Earth (termed magnetofossils) have been documented in sediments as old as the ~2 Byr Gunflint Chert. Magnetofossils 4 Byr old have also been reported from carbonates in the Martian meteorite ALH84001; if this interpretation is correct, they represent the oldest evidence for life yet found. Past techniques for identification of bacterial magnetofossils have relied on the use of particle extraction and high-resolution electron microscopy (HRTEM). Because these techniques are time-consuming and fairly complex, they are not appropriate for screening large volumes of sediments on Earth and could not be used remotely on a Martian lander. For this reason, we have been testing a variety of ferromagnetic resonance and low-temperature rock magnetic techniques to determine if they are capable of identifying correctly rock samples known to contain abundant magnetofossils. An instrument capable of making such a determination, if deployed on the Martian surface, could be extraordinarily valuable for selecting samples for return to Earth. Several features of the ferromagnetic resonance (FMR) spectra have signatures only displayed by pure samples of magnetite from the magnetotactic bacteria, and from samples known to contain abundant magnetofossils. These unique features apparently arise from the elongated shape and narrow size distribution of the single-domain magnetite produced by these bacteria. Preliminary results from ALH84001 carbonates also have these features. We are also currently obtaining FMR spectra and low-temperature rock magnetic data on samples of Archean and Early Proterozoic sediments from Australia to search for older evidence of intracellular magnetite biomineralization on Earth.

  20. Les transfusions de globules rouges chez le nouveau-né : Des directives révisées

    PubMed Central

    2002-01-01

    En général, depuis dix ans, les professionnels de la santé qui soignent des nouveau-nés à haut risque dans des unités de soins intensifs néonatals sont plus restrictifs dans leur utilisation de transfusions de globules rouges. Le présent énoncé est conçu pour ceux qui soignent des nouveau-nés à haut risque (des prématurés aux nouveau-nés d’un mois). Il vise à fournir des directives pour réduire l’incidence d’anémie chez les nourrissons prématurés et à terme, à repérer des stratégies pour réduire le besoin de transfusions de globules rouges et à limiter l’exposition à des donneurs au sein de cette population. Des recommandations portant sur les transfusions de globules rouges sont incluses.

  1. Evidence for close side-chain packing in an early protein folding intermediate previously assumed to be a molten globule.

    PubMed

    Rosen, Laura E; Connell, Katelyn B; Marqusee, Susan

    2014-10-14

    The molten globule, a conformational ensemble with significant secondary structure but only loosely packed tertiary structure, has been suggested to be a ubiquitous intermediate in protein folding. However, it is difficult to assess the tertiary packing of transiently populated species to evaluate this hypothesis. Escherichia coli RNase H is known to populate an intermediate before the rate-limiting barrier to folding that has long been thought to be a molten globule. We investigated this hypothesis by making mimics of the intermediate that are the ground-state conformation at equilibrium, using two approaches: a truncation to generate a fragment mimic of the intermediate, and selective destabilization of the native state using point mutations. Spectroscopic characterization and the response of the mimics to further mutation are consistent with studies on the transient kinetic intermediate, indicating that they model the early intermediate. Both mimics fold cooperatively and exhibit NMR spectra indicative of a closely packed conformation, in contrast to the hypothesis of molten tertiary packing. This result is important for understanding the nature of the subsequent rate-limiting barrier to folding and has implications for the assumption that many other proteins populate molten globule folding intermediates. PMID:25258414

  2. Identification of Escherichia coli F4ac-binding proteins in porcine milk fat globule membrane.

    PubMed

    Novakovic, Predrag; Huang, Yanyun Y; Lockerbie, Betty; Shahriar, Farshid; Kelly, John; Gordon, John R; Middleton, Dorothy M; Loewen, Matthew E; Kidney, Beverly A; Simko, Elemir

    2015-04-01

    F4ac-positive enterotoxigenic Escherichia coli (ETEC) must attach to the intestinal mucosa to cause diarrhea in piglets. Prevention of bacterial attachment to the intestinal mucosa is the most effective defense against ETEC-induced diarrhea. Porcine milk fat globule membranes (MFGM) were shown to be able to inhibit attachment of ETEC to the intestinal brush border; however, the specific components of porcine MFGM that inhibited attachment of ETEC to enterocytes were not identified. Accordingly, the purpose of this study was to identify F4ac-binding MFGM proteins by overlay Western blot and affinity chromatography. The proteome of porcine MFGM was characterized and the following F4ac-binding proteins were detected by overlay Western blot and affinity chromatography: lactadherin, butyrophilin, adipophilin, acyl-CoA synthetase 3, and fatty acid-binding protein 3. The biological function of these proteins was not investigated but it is possible that their interaction with F4ac fimbria interferes with bacterial attachment and colonization. PMID:25852227

  3. Phagocytosis mechanism of apoptotic granulosa cells regulated by milk-fat globule-EGF factor 8.

    PubMed

    Naka, Mayumi; Kusakabe, Ken; Takeshita, Ai; Nakagawa, Hiroshi; Ito, Yuko; Shibata, Masa-Aki; Otsuki, Yoshinori

    2009-09-01

    In the process of ovary sexual maturation, most immature ovarian follicles degrade into atretic follicles accompanied by apoptosis in granulosa cells. Macrophages can recognize apoptotic cells through specific binding with phosphatidylserine (PS), exposed on the surface of apoptotic cells, which is mediated by milk-fat globule-EGF factor 8 (MFG-E8). In the present research, we examined the involvement of the MFG-E8-dependent phagocytosis system in the atretic follicles of developing mouse ovaries. The number of atretic follicles and DNA-fragmented granulosa cells significantly increased in B6C3F1 mice during 2 to 6 weeks. Chromatin-condensed granulosa cells were engulfed by macrophages, which existed in the stroma or atretic follicles, or by neighboring normal granulosa cells. MFG-E8 mRNA increased in ovaries during 2 to 6 weeks, and immunoreactivity of MFG-E8 was detected at the surface of apoptotic cells existing around the antrum. Immunoelectron microscopic study revealed MFG-E8-positive signals on the membrane of apoptotic cells near macrophages, but apoptotic cells engulfed by neighboring granulosa cells showed few signals. Anti-Fas antibody elevated the annexin-V-positive reaction in isolated granulosa cells from 3-week-old mouse ovaries. MFG-E8 seems to act on the phagocytosis of apoptotic granulosa cells via macrophages and contribute to the regression process of atretic follicles. PMID:19784740

  4. A model of the molten globule state from molecular dynamics simulations.

    PubMed Central

    Daggett, V; Levitt, M

    1992-01-01

    It is generally accepted that a protein's primary sequence determines its three-dimensional structure. It has proved difficult, however, to obtain detailed structural information about the actual protein folding process and intermediate states. We present the results of molecular dynamics simulations of the unfolding of reduced bovine pancreatic trypsin inhibitor. The resulting partially "denatured" state was compact but expanded relative to the native state (11-25%); the expansion was not caused by an influx of water molecules. The structures were mobile, with overall secondary structure contents comparable to those of the native protein. The protein experienced relatively local unfolding, with the largest changes in the structure occurring in the loop regions. A hydrophobic core was maintained although packing of the side chains was compromised. The properties displayed in the simulation are consistent with unfolding to a molten globule state. Our simulations provide an in-depth view of this state and details of water-protein interactions that cannot yet be obtained experimentally. Images PMID:1594623

  5. Identification of Escherichia coli F4ac-binding proteins in porcine milk fat globule membrane

    PubMed Central

    Novakovic, Predrag; Huang, Yanyun Y.; Lockerbie, Betty; Shahriar, Farshid; Kelly, John; Gordon, John R.; Middleton, Dorothy M.; Loewen, Matthew E.; Kidney, Beverly A.; Simko, Elemir

    2015-01-01

    F4ac-positive enterotoxigenic Escherichia coli (ETEC) must attach to the intestinal mucosa to cause diarrhea in piglets. Prevention of bacterial attachment to the intestinal mucosa is the most effective defense against ETEC-induced diarrhea. Porcine milk fat globule membranes (MFGM) were shown to be able to inhibit attachment of ETEC to the intestinal brush border; however, the specific components of porcine MFGM that inhibited attachment of ETEC to enterocytes were not identified. Accordingly, the purpose of this study was to identify F4ac-binding MFGM proteins by overlay Western blot and affinity chromatography. The proteome of porcine MFGM was characterized and the following F4ac-binding proteins were detected by overlay Western blot and affinity chromatography: lactadherin, butyrophilin, adipophilin, acyl-CoA synthetase 3, and fatty acid-binding protein 3. The biological function of these proteins was not investigated but it is possible that their interaction with F4ac fimbria interferes with bacterial attachment and colonization. PMID:25852227

  6. Polyol-induced molten globule of cytochrome c: an evidence for stabilization by hydrophobic interaction.

    PubMed

    Kamiyama, T; Sadahide, Y; Nogusa, Y; Gekko, K

    1999-09-14

    To address the contribution of hydrophobic interaction to the stability of molten globule (MG) of proteins, the effects of various polyols (ethylene glycol, glycerol, erythritol, xylitol, sorbitol, and inositol) on the structure of acid-unfolded horse cytochrome c were examined at pH 2, by means of circular dichroism (CD), partial specific volume, adiabatic compressibility, and differential scanning calorimetry (DSC). Addition of polyols induced the characteristic CD spectra of MG, the effect being enhanced with an increase in their concentration and chain length (the number of OH groups) of polyols except for ethylene glycol. The free energy change of MG formation by sorbitol was comparable with those for the salt-induced MG formation but the heat capacity change was negligibly small. The partial specific volume did not change within the experimental error but the adiabatic compressibility largely increased by MG formation. The sorbitol-induced MG showed a highly cooperative DSC thermogram with a large heat capacity change in comparison with the salt-induced one. These results demonstrate that polyols can stabilize the MG state of this protein through the enhanced hydrophobic interaction overcoming the electrostatic repulsion between charged residues. The stabilizing mechanism and structure of MG state induced by polyols were discussed in terms of the preferential solvent interactions and osmotic pressure of the medium, in comparison with the salt-induced one. PMID:10556558

  7. Rise of the Helix from a Collapsed Globule during the Folding of Monellin.

    PubMed

    Goluguri, Rama Reddy; Udgaonkar, Jayant B

    2015-09-01

    Early kinetic intermediates observed during the folding of many proteins are invariably compact and appear to possess some secondary structure. Consequently, it has been difficult to understand whether compaction drives secondary structure formation or secondary structure formation facilitates compaction during folding. In this study of the folding of single-chain monellin, it is shown that a kinetic molten globule (MG) is populated at 2 ms of folding. Far-UV circular dichroism (CD) measurements show that the kinetic MG is devoid of any helical structure even under the most stabilizing folding conditions. Multisite fluorescence resonance energy transfer (FRET) measurements show that the kinetic MG is compact with different segments having contracted to different extents. It is shown that the sequence segment that goes on to form the sole helix in the native protein is fully collapsed in the kinetic MG. This segment expands to accommodate the helix as the kinetic MG folds further to the native state, while other segments of the protein contract. Helix formation starting from the kinetic MG is shown to occur in multiple kinetic steps, whether measured by far-UV CD or by FRET. PMID:26258844

  8. Gradual Folding of an Off-Pathway Molten Globule Detected at the Single-Molecule Level.

    PubMed

    Lindhoud, Simon; Pirchi, Menahem; Westphal, Adrie H; Haran, Gilad; van Mierlo, Carlo P M

    2015-09-25

    Molten globules (MGs) are compact, partially folded intermediates that are transiently present during folding of many proteins. These intermediates reside on or off the folding pathway to native protein. Conformational evolution during folding of off-pathway MGs is largely unexplored. Here, we characterize the denaturant-dependent structure of apoflavodoxin's off-pathway MG. Using single-molecule fluorescence resonance energy transfer (smFRET), we follow conversion of unfolded species into MG down to denaturant concentrations that favor formation of native protein. Under strongly denaturing conditions, fluorescence resonance energy transfer histograms show a single peak, arising from unfolded protein. The smFRET efficiency distribution shifts to higher value upon decreasing denaturant concentration because the MG folds. Strikingly, upon approaching native conditions, the fluorescence resonance energy transfer efficiency of the MG rises above that of native protein. Thus, smFRET exposes the misfolded nature of apoflavodoxin's off-pathway MG. We show that conversion of unfolded into MG protein is a gradual, second-order-like process that simultaneously involves separate regions within the polypeptide. PMID:26163276

  9. ARE LARGE, COMETARY-SHAPED PROPLYDS REALLY (FREE-FLOATING) EVAPORATING GAS GLOBULES?

    SciTech Connect

    Sahai, R.; Guesten, R.; Morris, M. R.

    2012-12-20

    We report the detection of strong and compact molecular line emission (in the CO J = 3-2, 4-3, 6-5, 7-6, {sup 13}CO J = 3-2, HCN, and HCO{sup +} J = 4-3 transitions) from a cometary-shaped object (Carina-frEGG1) in the Carina star-forming region (SFR) previously classified as a photoevaporating protoplanetary disk (proplyd). We derive a molecular mass of 0.35 M{sub Sun} for Carina-frEGG1, which shows that it is not a proplyd, but belongs to a class of free-floating evaporating gas globules (frEGGs) recently found in the Cygnus SFR by Sahai et al. Archival adaptive optics near-IR (Ks) images show a central hourglass-shaped nebula. The derived source luminosity (about 8-18 L{sub Sun }), the hourglass morphology, and the presence of collimated jets seen in Hubble Space Telescope images imply the presence of a jet-driving, young, low-mass star deeply embedded in the dust inside Carina-frEGG1. Our results suggest that the true nature of many or most such cometary-shaped objects seen in massive SFRs and previously labeled as proplyds has been misunderstood, and that these are really frEGGs.

  10. The sources of water in Martian meteorites: clues from hydrogen isotopes

    NASA Astrophysics Data System (ADS)

    Boctor, N. Z.; Alexander, C. M. O.'D.; Wang, J.; Hauri, E.

    2003-10-01

    H isotope measurements of carbonate, phosphate, feldspathic and mafic glasses, and post-stishovite silica phase in the shergottites Zagami, Shergotty, SaU 005, DaG 476, ALHA 77005 and EETA 79001, as well as in Chassigny and ALH 84001, show that all these phases contain deuterium-enriched water of extraterrestrial origin. The minerals and glasses analyzed may contain an initial primary hydrogen component, but their isotopic composition was modified to varying degrees by three different processes: interaction with a fractionated exchangeable water reservoir on Mars, hydrogen devolatilization by impact melting, and terrestrial contamination. Positive correlations between δD and water abundance in feldspathic glass and post-stishovite silica in Zagami, Shergotty, and SaU 005 is indicative of mixing of a high δD component (3000-4000‰) and a less abundant, low δD component (˜0‰). The high δD component is primarily derived from the Martian exchangable reservoir, but may also have been influenced by isotopic fractionation associated with shock-induced hydrogen loss. The low δD component is either a terrestrial contaminant or a primary "magmatic" component. The negative correlation between δD and water abundances in mafic and feldspathic glasses in ALH 84001, ALHA 77005, and EETA 79001 is consistent with the addition of a low δD terrestrial contaminant to a less abundant high-deuterium Martian component. The low δD of magmatic glass in melt inclusions suggests that the δD of Martian parent magma was low and that the initial H isotope signature of Mars may be similar to that of Earth.

  11. Milk fat globule E-8 and interleukin 17 in systemic lupus erythematosus: partners in crime?

    PubMed Central

    Elgengehy, Fatema; Niazy, Marwa; Ghoneim, Shada

    2016-01-01

    Objectives Systemic lupus erythematosus (SLE) is a multi-factorial, autoimmune disease with a wide array of manifestations. The pro-inflammatory cytokine interleukin (IL)-17 has been implicated in the inflammatory response and tissue damage in SLE; however, its correlation with disease activity is still questionable. Meanwhile, efficient clearance of apoptotic cells is required for immune tolerance. An abnormally low or high level of milk fat globule (MFG-E8) can result in impaired apoptotic cell clearance and the subsequent autoimmune response. In this study, we endeavoured to compare the levels of MFG-E8 and IL-17 in SLE patients and healthy controls and to reveal the alleged association of these levels with SLE disease activity. Material and methods Serum samples from 57 SLE patients and 30 healthy control subjects were examined for quantitation of MFG-E8 and IL-17 levels using ELISA. Systemic lupus erythematosus disease activity was calculated using the SLE Disease Activity Index (SLEDAI). Clinical manifestations and laboratory findings of the patients were also recorded. Results We report that serum MFG-E8 levels were significantly elevated in the sera of SLE patients compared to healthy controls (p-value = 0.019). Likewise, IL-17 levels were higher in SLE patients (p-value < 0.001). A positive correlation was revealed between MFG-E8 level and proteinuria. Surprisingly, there was a poor correlation between disease activity and the levels of either IL-17 or MFG-E8. Conclusions Although serum MFG-E8 and IL-17 levels were higher in SLE patients than in normal controls, our results indicate that they cannot accurately reflect the disease activity. Meanwhile, further studies are needed to assess MFG-E8 and IL-17 as potential therapeutic targets in SLE patients. PMID:27407263

  12. Molten Globule of Hemoglobin Proceeds into Aggregates and Advanced Glycated End Products

    PubMed Central

    Iram, Afshin; Alam, Tauqeer; Khan, Javed M.; Khan, Taqi A.; Khan, Rizwan H.; Naeem, Aabgeena

    2013-01-01

    Conformational alterations of bovine hemoglobin (Hb) upon sequential addition of glyoxal over a range of 0–90% v/v were investigated. At 20% v/v glyoxal, molten globule (MG) state of Hb was observed by altered tryptophan fluorescence, high ANS binding, existence of intact heme, native-like secondary structure as depicted by far-UV circular dichroism (CD) and ATR-FTIR spectra as well as loss in tertiary structure as confirmed by near-UV CD spectra. In addition, size exclusion chromatography analysis depicted that MG state at 20% v/v glyoxal corresponded to expanded pre-dissociated dimers. Aggregates of Hb were detected at 70% v/v glyoxal. These aggregates of Hb had altered tryptophan environment, low ANS binding, exposed heme, increased β-sheet secondary structure, loss in tertiary structure, enhanced thioflavin T (ThT) fluorescence and red shifted Congo Red (CR) absorbance. On incubating Hb with 30% v/v glyoxal for 0–20 days, advanced glycation end products (AGEs) were detected on day 20. These AGEs were characterised by enhanced tryptophan fluorescence at 450 nm, exposure of heme, increase in intermolecular β-sheets, enhanced ThT fluorescence and red shift in CR absorbance. Comet assay revealed aggregates and AGEs to be genotoxic in nature. Scanning electron microscopy confirmed the amorphous structure of aggregates and branched fibrils of AGEs. The transformation of α-helix to β-sheet usually alters the normal protein to amyloidogenic resulting in a variety of protein conformational disorders such as diabetes, prion and Huntington's. PMID:23991043

  13. Improved Flat-Fielding for Crowded Field Imaging Polarimetry: The Star Forming BOK Globule B335

    NASA Astrophysics Data System (ADS)

    Wright, J.; Ilardi, P.; Clemens, D.

    1996-05-01

    In order to achieve a qualitative improvement in descriptions of the magnetic fields associated with small, dense molecular clouds, traced via background starlight polarization, a CCD-based imaging polarimeter was built and operated. This instrument simultaneously measured the linear polarizations of 25 - 50 stars per 5 arcminute CCD frame (Clemens and Leach 1987, Optical Engineering, 29, 923). The instrument consisted of a rotating polaroid in front of a quarter-wave plate, broadband V filter, and a TI 800 x 800 pixel CCD. The observing mode involved polarization chopping and dual direction CCD charge shifting, resulting in images which contained two stellar objects for each star. However, decoupling of the flat-field response of the CCD from the shifted-and-added images is not trivial. One solution was to ignore the flat-field step and proceed to photometric and then polarimetric analysis of the star light, as was performed by Kane in his dissertation (1995, Boston University). Revisiting the flat-fielding problem, we have developed a new approach which borrows from techniques employed in ground-based infrared astronomy. In this method, we analyze the shape of the stellar background (sky) imaged onto the CCD, via comparison with dome flats, to develop a detailed sky model. Subtraction of this sky model from the raw images leaves sky corrected stellar images. Stellar pair matching and classification is used to extract the individual stellar PSFs for direct flat field correction before performing photometry. This detailed analysis results in lower random and systematic errors than our previous method. In this poster, we present the polarimetric map deduced from the light of stars behind the periphery of the star forming globule B335, and compare the polarimetric limits obtained using our two methods.

  14. Milk fat globule is an alternative to mammary epithelial cells for gene expression analysis in buffalo.

    PubMed

    Chen, Qiuming; Wu, Yanjun; Zhang, Mingyuan; Xu, Wenwen; Guo, Xiaoping; Yan, Xueyu; Deng, Haiying; Jiang, Qinyang; Yang, Xiurong; Lan, Ganqiu; Guo, Yafen; Qin, Guangsheng; Jiang, Hesheng

    2016-05-01

    Owing to the difficulty in obtaining mammary gland tissue from lactating animals, it is difficult to test the expression levels of genes in mammary gland. The aim of the current study was to identify if milk fat globule (MFG) in buffalo milk was an alternative to mammary gland (MG) and milk somatic cell (MSC) for gene expression analysis. Six buffalos in late lactation were selected to collect MFG and MSC, and then MG was obtained by surgery. MFG was stained with acridine orange to successfully visualise RNA and several cytoplasmic crescents in MFG. The total RNA in MFG was successfully isolated and the integrity was assessed by agarose gel electrophoresis. We analysed the cellular components in MFG, MG and MSC through testing the expression of cell-specific genes by qRT-PCR. The results showed that adipocyte-specific gene (AdipoQ) and leucocyte-specific genes (CD43, CSF1 and IL1α) in MFG were not detected, whereas epithelial cell marker genes (Keratin 8 and Keratin 18) in MFG were higher than in MSC and lower than in MG, fibroblast marker gene (vimentin) in MFG was significantly lower than in MG and MSC, milk protein genes (LALBA, BLG and CSN2) and milk fat synthesis-related genes (ACC, BTN1A1, FABP3 and FAS) in MFG were higher than in MG and MSC. In conclusion, the total RNA in MFG mainly derives from mammary epithelial cells and can be used to study the functional gene expression of mammary epithelial cells. PMID:27032540

  15. Study of magnetic field geometry and extinction in Bok globule CB130

    NASA Astrophysics Data System (ADS)

    Chakraborty, A.; Das, H. S.

    2016-09-01

    We trace the peripheral magnetic field structure of Bok globule CB130 by estimating the linear polarization of its field stars in the R band. The magnetic field orientation sampled by these stars, aligned on average among themselves, and the polarization produced within the cloud has a different direction from that of Galactic plane with an offset of 53°. The offset between minor axis and the mean magnetic field of CB130 is found to be 80°. The estimated strength of the magnetic field in the plane-of-the-sky is ˜116±19 μG. We constructed the visual extinction map using the Near Infrared Color Excess (NICE) method to see the dust distribution around CB130. Contours of Herschel (Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA) SPIRE 500 μm dust continuum emission map of this cloud is over-plotted on the visual extinction map, which shows that the regions having higher optical extinction correspond to higher densities of dust. Three distinct high dust density cores (named as C1, C2, and C3) are identified in the extinction map. It is observed that the cores C1 and C3 are located close to two previously known cores CB130-1 and CB130-2, respectively. Estimates of visual extinction of some moderately obscured stars of CB130 are made utilizing near-infrared photometry. It is observed that there is a feeble dependence of polarization on extinction, and the polarization efficiency (defined as p/AV) of the dust grains decreases with the increase in extinction.

  16. Comparative Proteomics of Milk Fat Globule Membrane Proteins from Transgenic Cloned Cattle

    PubMed Central

    Wang, Jianwu; Zhang, Ran; Guo, Chengdong; Yu, Tian; Li, Ning

    2014-01-01

    The use of transgenic livestock is providing new methods for obtaining pharmaceutically useful proteins. However, the protein expression profiles of the transgenic animals, including expression of milk fat globule membrane (MFGM) proteins, have not been well characterized. In this study, we compared the MFGM protein expression profile of the colostrum and mature milk from three lines of transgenic cloned (TC) cattle, i.e., expressing recombinant human α-lactalbumin (TC-LA), lactoferrin (TC-LF) or lysozyme (TC-LZ) in the mammary gland, with those from cloned non-transgenic (C) and conventionally bred normal animals (N). We identified 1, 225 proteins in milk MFGM, 166 of which were specifically expressed only in the TC-LA group, 265 only in the TC-LF group, and 184 only in the TC-LZ group. There were 43 proteins expressed only in the transgenic cloned animals, but the concentrations of these proteins were below the detection limit of silver staining. Functional analysis also showed that the 43 proteins had no obvious influence on the bovine mammary gland. Quantitative comparison revealed that MFGM proteins were up- or down-regulated more than twofold in the TC and C groups compared to N group: 126 in colostrum and 77 in mature milk of the TC-LA group; 157 in colostrum and 222 in mature milk of the TC-LF group; 49 in colostrum and 98 in mature milk of the TC-LZ group; 98 in colostrum and 132 in mature milk in the C group. These up- and down-regulated proteins in the transgenic animals were not associated with a particular biological function or pathway, which appears that expression of certain exogenous proteins has no general deleterious effects on the cattle mammary gland. PMID:25133402

  17. Mars as the Parent Body for the CI Carbonaceous Chondrites: Confirmation of Early Mars Biology

    NASA Astrophysics Data System (ADS)

    Brandenburg, J. E.

    2003-07-01

    Mounting evidence suggests that CI Carbonaceaous Chondrites belong in the Mars meteorite family. They thus represent samples, like ALH84001, of the Noachian surface environment, and are rich in organic matter, suggesting a living environment.

  18. The Microbiological Contamination of Meteorites: A Null Hypothesis

    NASA Technical Reports Server (NTRS)

    Steele, A.; Toporski, J. K. W.; Westall, F. W.; Thomas-Keprta, K.; Gibson, E. K.; Avci, R.; Whitby, C.; McKay, D. S.; Griffin, C.

    2000-01-01

    Using 4 different techniques we have studied 9 meteorites including the Martian meteorites ALH84001 and Nakhla for terrestrial contamination in all 9 we have found evidence of terrestrial microorganisms.

  19. Secretion of three enzymes for fatty acid synthesis into mouse milk in association with fat globules, and rapid decrease of the secreted enzymes by treatment with rapamycin.

    PubMed

    Moriya, Hitomi; Uchida, Kana; Okajima, Tetsuya; Matsuda, Tsukasa; Nadano, Daita

    2011-04-01

    The mammary epithelium produces numerous lipid droplets during lactation and secretes them in plasma membrane-enclosed vesicles known as milk fat globules. The biogenesis of such fat globules is considered to provide a model for clarifying the mechanisms of lipogenesis in mammals. In the present study, we identified acetyl coenzyme A carboxylase, ATP citrate lyase, and fatty acid synthase in mouse milk. Fractionation of milk showed that these three enzymes were located predominantly in milk fat globules. The three enzymes were resistant to trypsin digestion without Triton X-100, indicating that they were not located on the outer surface of the globules and thus associated with the precursors of the globules before secretion. When a low dose of rapamycin, an inhibitor of the mammalian target of rapamycin (mTOR), was injected into lactating mice, the levels of the three enzymes in milk were decreased within 3h after injection. Since the protein levels of the three enzymes in tissues were not obviously altered by this short-term treatment, known transcriptional control by mTOR signaling was unlikely to account for this decrease in their levels in milk. Our findings suggest a new, putatively mTOR-dependent localization of the three enzymes for de novo lipogenesis. PMID:21281598

  20. A molten globule intermediate of the Von Willebrand Factor A1 domain firmly tethers platelets under shear flow

    PubMed Central

    Tischer, Alexander; Madde, Pranathi; Blancas-Mejia, Luis. M.; Auton, Matthew

    2014-01-01

    Clinical mutations in patients diagnosed with Type 2A von Willebrand disease (vWD) have been identified that break the single disulfide bond linking N- and C-termini in the vWF A1 domain. We have modeled the effect of these mutations on the disulfide-bonded structure of A1 by reducing and carboxy-amidating these cysteines. Solution biophysical studies show that loss of this disulfide bond induces a molten globule conformational state lacking global tertiary structure but retaining residual secondary structure. The conformational dependence of platelet adhesion to these native and molten globule states of A1 is quantitatively compared using real-time high-speed video microscopy analysis of platelet translocation dynamics under shear flow in a parallel plate micro-fluidic flow chamber. While normal platelets translocating on surface-captured native A1 domain retain the catch-bond character of pause times that increase as a function of shear rate at low shear and decrease as a function of shear rate at high shear, platelets that interact with A1 lacking the disulfide bond remain stably attached and do not translocate. Based on these findings, we propose that the shear stress-sensitive regulation of the A1-GPIb interaction is due to folding the tertiary structure of this domain. Removal of the tertiary structure by disrupting the disulfide bond destroys this regulatory mechanism resulting in high-strength interactions between platelets and vWF A1 that are dependent only on residual secondary structure elements present in the molten globule conformation. PMID:24265179

  1. A molten globule intermediate of the von Willebrand factor A1 domain firmly tethers platelets under shear flow.

    PubMed

    Tischer, Alexander; Madde, Pranathi; Blancas-Mejia, Luis M; Auton, Matthew

    2014-05-01

    Clinical mutations in patients diagnosed with Type 2A von Willebrand disease (VWD) have been identified that break the single disulfide bond linking N- and C-termini in the vWF A1 domain. We have modeled the effect of these mutations on the disulfide-bonded structure of A1 by reducing and carboxy-amidating these cysteines. Solution biophysical studies show that loss of this disulfide bond induces a molten globule conformational state lacking global tertiary structure but retaining residual secondary structure. The conformational dependence of platelet adhesion to these native and molten globule states of A1 is quantitatively compared using real-time high-speed video microscopy analysis of platelet translocation dynamics under shear flow in a parallel plate microfluidic flow chamber. While normal platelets translocating on surface-captured native A1 domain retain the catch-bond character of pause times that increase as a function of shear rate at low shear and decrease as a function of shear rate at high shear, platelets that interact with A1 lacking the disulfide bond remain stably attached and do not translocate. Based on these findings, we propose that the shear stress-sensitive regulation of the A1-GPIb interaction is due to folding the tertiary structure of this domain. Removal of the tertiary structure by disrupting the disulfide bond destroys this regulatory mechanism resulting in high-strength interactions between platelets and vWF A1 that are dependent only on residual secondary structure elements present in the molten globule conformation. PMID:24265179

  2. Characterization of molten globule PopB in absence and presence of its chaperone PcrH.

    PubMed

    Dey, Supratim; Basu, Abhishek; Datta, Saumen

    2012-06-01

    The TTSS encoding "translocator operon" of Pseudomonas aeruginosa consists of a major translocator protein PopB, minor translocator protein PopD and their cognate chaperone PcrH. Far-UV CD spectra and secondary structure prediction servers predict an α-helical model for PopB, PcrH and PopB-PcrH complex. PopB itself forms a single species of higher order oligomer (15 mer) as seen from AUC, but in complex with PcrH, both monomeric (1:1) and oligomeric form exist. PopB has large solvent-exposed hydrophobic patches and exists as an unordered molten globule in its native state, but on forming complex with PcrH it gets transformed into an ordered molten globule. Tryptophan fluorescence spectrum indicates that PopB interacts with the first TPR region of dimeric PcrH to form a stable PopB-PcrH complex that has a partial rigid structure with a large hydrodynamic radius and few tertiary contacts. The pH-dependent studies of PopB, PcrH and complex by ANS fluorescence, urea induced unfolding and thermal denaturation experiments prove that PcrH not only provides structural support to the ordered molten globule PopB in complex but also undergoes conformational change to assist PopB to pass through the needle complex of TTSS and form pores in the host cell membrane. ITC experiments show a strong affinity (K(d) ~ 0.37 μM) of PopB for PcrH at pH 7.8, which reduces to ~0.68 μM at pH 5.8. PcrH also loses its rigid tertiary structure at pH 5 and attains a molten globule conformation. This indicates that the decrease in pH releases PopB molecules and thus triggers the TTSS activation mechanism for the formation of a functional translocon. PMID:22585368

  3. Magnetism and the putative early Martian life

    NASA Astrophysics Data System (ADS)

    Rochette, P.

    2001-08-01

    A short critical review is provided on three questions linking magnetism and the putative early Mars life. Was there a large internal Martian magnetic field, during which period, and is it a requisite for life? What is the origin of the paleomagnetic signal of Martian meteorites, including ALH84001? What is the present credibility of the case for fossil bacterial magnetite grains in ALH84001?

  4. Mechanistic Insight into the Reactivation of BCAII Enzyme from Denatured and Molten Globule States by Eukaryotic Ribosomes and Domain V rRNAs.

    PubMed

    Chakraborty, Biprashekhar; Bhakta, Sayan; Sengupta, Jayati

    2016-01-01

    In all life forms, decoding of messenger-RNA into polypeptide chain is accomplished by the ribosome. Several protein chaperones are known to bind at the exit of ribosomal tunnel to ensure proper folding of the nascent chain by inhibiting their premature folding in the densely crowded environment of the cell. However, accumulating evidence suggests that ribosome may play a chaperone role in protein folding events in vitro. Ribosome-mediated folding of denatured proteins by prokaryotic ribosomes has been studied extensively. The RNA-assisted chaperone activity of the prokaryotic ribosome has been attributed to the domain V, a span of 23S rRNA at the intersubunit side of the large subunit encompassing the Peptidyl Transferase Centre. Evidently, this functional property of ribosome is unrelated to the nascent chain protein folding at the exit of the ribosomal tunnel. Here, we seek to scrutinize whether this unique function is conserved in a primitive kinetoplastid group of eukaryotic species Leishmania donovani where the ribosome structure possesses distinct additional features and appears markedly different compared to other higher eukaryotic ribosomes. Bovine Carbonic Anhydrase II (BCAII) enzyme was considered as the model protein. Our results manifest that domain V of the large subunit rRNA of Leishmania ribosomes preserves chaperone activity suggesting that ribosome-mediated protein folding is, indeed, a conserved phenomenon. Further, we aimed to investigate the mechanism underpinning the ribosome-assisted protein reactivation process. Interestingly, the surface plasmon resonance binding analyses exhibit that rRNA guides productive folding by directly interacting with molten globule-like states of the protein. In contrast, native protein shows no notable affinity to the rRNA. Thus, our study not only confirms conserved, RNA-mediated chaperoning role of ribosome but also provides crucial insight into the mechanism of the process. PMID:27099964

  5. Mechanistic Insight into the Reactivation of BCAII Enzyme from Denatured and Molten Globule States by Eukaryotic Ribosomes and Domain V rRNAs

    PubMed Central

    Chakraborty, Biprashekhar; Bhakta, Sayan; Sengupta, Jayati

    2016-01-01

    In all life forms, decoding of messenger-RNA into polypeptide chain is accomplished by the ribosome. Several protein chaperones are known to bind at the exit of ribosomal tunnel to ensure proper folding of the nascent chain by inhibiting their premature folding in the densely crowded environment of the cell. However, accumulating evidence suggests that ribosome may play a chaperone role in protein folding events in vitro. Ribosome-mediated folding of denatured proteins by prokaryotic ribosomes has been studied extensively. The RNA-assisted chaperone activity of the prokaryotic ribosome has been attributed to the domain V, a span of 23S rRNA at the intersubunit side of the large subunit encompassing the Peptidyl Transferase Centre. Evidently, this functional property of ribosome is unrelated to the nascent chain protein folding at the exit of the ribosomal tunnel. Here, we seek to scrutinize whether this unique function is conserved in a primitive kinetoplastid group of eukaryotic species Leishmania donovani where the ribosome structure possesses distinct additional features and appears markedly different compared to other higher eukaryotic ribosomes. Bovine Carbonic Anhydrase II (BCAII) enzyme was considered as the model protein. Our results manifest that domain V of the large subunit rRNA of Leishmania ribosomes preserves chaperone activity suggesting that ribosome-mediated protein folding is, indeed, a conserved phenomenon. Further, we aimed to investigate the mechanism underpinning the ribosome-assisted protein reactivation process. Interestingly, the surface plasmon resonance binding analyses exhibit that rRNA guides productive folding by directly interacting with molten globule-like states of the protein. In contrast, native protein shows no notable affinity to the rRNA. Thus, our study not only confirms conserved, RNA-mediated chaperoning role of ribosome but also provides crucial insight into the mechanism of the process. PMID:27099964

  6. Comparison of Milk Fat Globule Membrane (MFGM) Proteins of Chianina and Holstein Cattle Breed Milk Samples Through Proteomics Methods

    PubMed Central

    Murgiano, Leonardo; Timperio, Anna Maria; Zolla, Lello; Bongiorni, Silvia; Valentini, Alessio; Pariset, Lorraine

    2009-01-01

    Identification of proteins involved in milk production is important to understand the biology of lactation. Many studies have advanced the understanding of mammary function and milk secretion, but the critical molecular mechanisms implicated in milk fat secretion is still incomplete. Milk Fat Globules are secreted from the apical surface of the mammary cells, surrounded by a thin membrane bilayer, the Milk Fat Globule Membrane (MFGM), formed by proteins which have been suggested to be cholesterolemia-lowering factors, inhibitors of cancer cell growth, vitamin binders, bactericidal, suppressors of multiple sclerosis. Using a proteomic approach, we compared MFGM from milk samples of individuals belonging to two different cattle breeds, Chianina and Holstein, representative of selection for milk and meat traits, respectively. We were able to isolate some of the major MFGM proteins in the examined samples and to identify differences between the protein fractions of the two breeds. We detected differences in the amount of proteins linked to mammary gland development and lipid droplets formation, as well as host defence mechanisms. We have shown that proteomics is a suitable, unbiased method for the study of milk fractions proteins and a powerful tool in nutritional genomics. PMID:22253986

  7. Macromolecular Crowding Modifies the Impact of Specific Hofmeister Ions on the Coil-Globule Transition of PNIPAM.

    PubMed

    Sakota, Kenji; Tabata, Daiki; Sekiya, Hiroshi

    2015-08-13

    Macromolecular crowding alters many biological processes ranging from protein folding and enzyme reactions in vivo to the precipitation and crystallization of proteins in vitro. Herein, we have investigated the effect of specific monovalent Hofmeister salts (NaH2PO4, NaF, NaCl, NaClO4, and NaSCN) on the coil-globule transition of poly(N-isopropylacrylamide) (PNIPAM) in a crowded macromolecular environment as a model for understanding the specific-ion effect on the solubility and stability of proteins in a crowded macromolecular environment. It was found that although the salts (NaH2PO4, NaF, and NaCl) and the macromolecular crowder (polyethylene glycol) lowered the transition temperature almost independently, the macromolecular crowder had a great impact on the transition temperature in the case of the chaotropes (NaClO4 and NaSCN). The electrostatic repulsion between the chaotropic anions (ClO4(-) or SCN(-)) adsorbed on PNIPAM may reduce the entropic gain of water associated with the excluded volume effect, leading to an increase in the transition temperature, especially in the crowded environment. Furthermore, the affinity of the chaotropic anions for PNIPAM becomes small in the crowded environment, leading to further modification of the transition temperature. Thus, we have revealed that macromolecular crowding alters the effect of specific Hofmeister ions on the coil-globule transition of PNIPAM. PMID:26215482

  8. Microsecond Rearrangements of Hydrophobic Clusters in an Initially Collapsed Globule Prime Structure Formation during the Folding of a Small Protein.

    PubMed

    Goluguri, Rama Reddy; Udgaonkar, Jayant B

    2016-07-31

    Determining how polypeptide chain collapse initiates structure formation during protein folding is a long standing goal. It has been challenging to characterize experimentally the dynamics of the polypeptide chain, which lead to the formation of a compact kinetic molten globule (MG) in about a millisecond. In this study, the sub-millisecond events that occur early during the folding of monellin from the guanidine hydrochloride-unfolded state have been characterized using multiple fluorescence and fluorescence resonance energy transfer probes. The kinetic MG is shown to form in a noncooperative manner from the unfolded (U) state as a result of at least three different processes happening during the first millisecond of folding. Initial chain compaction completes within the first 37μs, and further compaction occurs only after structure formation commences at a few milliseconds of folding. The transient nonnative and native-like hydrophobic clusters with side chains of certain residues buried form during the initial chain collapse and the nonnative clusters quickly disassemble. Subsequently, partial chain desolvation occurs, leading to the formation of a kinetic MG. The initial chain compaction and subsequent chain rearrangement appear to be barrierless processes. The two structural rearrangements within the collapsed globule appear to prime the protein for the actual folding transition. PMID:27370109

  9. X-Ray Absorption Spectroscopy as a Probe of Microbial Sulfur Biochemistry: the Nature of Bacterial Sulfur Globules Revisited ▿

    PubMed Central

    George, Graham N.; Gnida, Manuel; Bazylinski, Dennis A.; Prince, Roger C.; Pickering, Ingrid J.

    2008-01-01

    The chemical nature of the sulfur in bacterial sulfur globules has been the subject of controversy for a number of years. Sulfur K-edge X-ray absorption spectroscopy (XAS) is a powerful technique for probing the chemical forms of sulfur in situ, but two groups have used it with very different conclusions. The root of the controversy lies with the different detection strategies used by the two groups, which result in very different spectra. This paper seeks to resolve the controversy. We experimentally demonstrate that the use of transmittance detection for sulfur K-edge XAS measurements is highly prone to spectroscopic distortions and that much of the published work on sulfur bacteria is very likely based on distorted data. We also demonstrate that all three detection methods used for X-ray absorption experiments yield essentially identical spectra when the measurements are carried out under conditions where no experimental distortions are expected. Finally, we turn to the original question—the chemical nature of bacterial sulfur. We examine isolated sulfur globules of Allochromatium vinosum and intact cells of a strain of magnetotactic coccus and show that XAS indicates the presence of a chemical form of sulfur resembling S8. PMID:18676668

  10. The Pb isotopic evolution of the Martian mantle constrained by initial Pb in Martian meteorites

    NASA Astrophysics Data System (ADS)

    Bellucci, J. J.; Nemchin, A. A.; Whitehouse, M. J.; Snape, J. F.; Bland, P.; Benedix, G. K.

    2015-12-01

    The Pb isotopic compositions of maskelynite and pyroxene grains were measured in ALH84001 and three enriched shergottites (Zagami, Roberts Massif 04262, and Larkman Nunatuk 12011) by secondary ion mass spectrometry. A maskelynite-pyroxene isochron for ALH84001 defines a crystallization age of 4089 ± 73 Ma (2σ). The initial Pb isotopic composition of each meteorite was measured in multiple maskelynite grains. ALH84001 has the least radiogenic initial Pb isotopic composition of any Martian meteorite measured to date (i.e., 206Pb/204Pb = 10.07 ± 0.17, 2σ). Assuming an age of reservoir formation for ALH84001 and the enriched shergottites of 4513 Ma, a two-stage Pb isotopic model has been constructed. This model links ALH84001 and the enriched shergottites by their similar μ value (238U/204Pb) of 4.1-4.6 from 4.51 Ga to 4.1 Ga and 0.17 Ga, respectively. The model employed here is dependent on a chondritic μ value (~1.2) from 4567 to 4513 Ma, which implies that core segregation had little to no effect on the μ value(s) of the Martian mantle. The proposed Pb isotopic model here can be used to calculate ages that are in agreement with Rb-Sr, Lu-Hf, and Sm-Nd ages previously determined in the meteorites and confirm the young (~170 Ma) ages of the enriched shergottites and ancient, >4 Ga, age of ALH84001.

  11. Bovine milk proteome: Quantitative changes in normal milk exosomes, milk fat globule membranes and whey proteomes resulting from Staphylococcus aureus mastitis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of milk protein composition/expression in healthy cows and cows with mastitis will provide information important for the dairy food industry, mammary biology and immune function in the mammary gland. To facilitate maximum protein discovery, milk was fractioned into whey, milk fat globule ...

  12. Star formation, structure, and formation mechanism of cometary globules: near-infrared observations of CG 1 and CG 2

    NASA Astrophysics Data System (ADS)

    Mäkelä, M. M.; Haikala, L. K.

    2013-02-01

    Context. Cometary globule (CG) 1 and CG 2 are "classic" cometary globules in the Gum Nebula. They have compact heads and long dusty tails that point away from the centre of the Gum Nebula. Aims: We study the structure of CG 1 and CG 2 and the star formation in them to find clues to the CG formation mechanism. The two possible CG formation mechanisms, radiation-driven implosion (RDI) and a supernova blast wave, produce a characteristic mass distribution where the major part of the mass is situated in either the head (RDI) or the tail (supernova blast). Methods: CG 1 and CG 2 were imaged in the near infrared (NIR) JsHKs bands. NIR photometry was used to locate NIR excess objects and to create visual extinction maps of the CGs. The AV maps allow us to analyse the large-scale structure of CG 1 and CG 2. Archival images from the WISE and Spitzer satellites and HIRES-processed IRAS images were used to study the globule's small-scale structure. Fits were made to the spectral energy distribution plots of the NIR-excess stars to estimate their age and mass. Results: In addition to the previously known CG 1 IRS 1 we discovered three new NIR-excess objects in IR imaging, two in CG 1 and one in CG 2. CG 2 IRS 1 is the first detection of star formation in CG 2. The objects are young low-mass stars. CG 1 IRS 1 is probably a class I protostar in the head of CG 1. CG 1 IRS 1 drives a bipolar outflow, which is very weak in CO, but the cavity walls are seen in reflected light in our NIR and in the Spitzer 3.6 and 4.5 μm images. Strong emission from excited polycyclic aromatic hydrocarbon particles and very small grains were detected in the CG 1 tail. The total mass of CG 1 in the observed area is 41.9 M⊙ of which 16.8 M⊙ lies in the head. For CG 2 these values are 31.0 M⊙ total and 19.1 M⊙ in the head. The observed mass distribution does not offer a firm conclusion for the formation mechanism of the two CGs: CG 1 is in too evolved a state, and in CG 2 part of the globule

  13. Physical properties and formation of MCLD 126.6+24.5 : a dense cometary shape globule at high-Galactic latitude

    NASA Astrophysics Data System (ADS)

    Ristorcelli, Isabelle; Rivera-Ingraham, Alana; Juvela, Mika; Falgarone, Edith; Pelkonen, Veli-Matti; Pagani, Laurent; Ysard, Nathalie; Montier, Ludovic; Montillaud, Julien; Marshall, Douglas; Bernard, Jean-Philippe

    2015-08-01

    The high-latitude molecular clouds are mostly gravitationally unbound and an interesting question to be investigated is how dense cores can form in such tenuous, diffuse environment, and what is their ability to form stars. Are these dense cores forming from random fluctuations in a turbulent medium, or is their formation triggered by external mechanisms ?We present here a detailed analysis of the dense high-latitude clump MCLD 126.6+24.5 observed with PACS and SPIRE as part of the Herschel Key-Program ‘Galactic Cold Cores’, a follow-up of Planck detections. The clump lies in a tenuous high-latitude cloud, located at the border of the Polaris Flare, a large molecular cirrus cloud in the direction of the north celestial pole, at an estimated distance of 150 pc. Its cometary globule shape appears similar to what is usually found in globules in active star formation regions, although this nebula is far from any such region.The column density distribution derived from the Herschel data shows a very sharp edge and narrow transition between the diffuse medium and the molecular part of the cloud. This remarkable feature could be the signature of a shocked-compression flow from its southern side, likely associated with the North Celestial Pole HI loop. Cold cores are found embedded inside the globule, with temperatures down to 10K. We also analyse the properties of its 2 main filaments (including a pillar-like structure). We present their main characteristics, both in terms of dust and gas physical properties, combining the Herschel data with IRAM maps of 13CO and C18O. We compare the overall properties of the globule and its structure with predictions from MHD simulations in order to investigate the origin of this intriguing cometary shape globule found in high-galactic latitude diffuse environment.

  14. 1-Anilino-8-Naphthalene Sulfonate (ANS) Is Not a Desirable Probe for Determining the Molten Globule State of Chymopapain

    PubMed Central

    Qadeer, Atiyatul; Rabbani, Gulam; Zaidi, Nida; Ahmad, Ejaz; Khan, Javed M.; Khan, Rizwan H.

    2012-01-01

    The molten globule (MG) state of proteins is widely detected through binding with 1-anilino-8-naphthalene sulphonate (ANS), a fluorescent dye. This strategy is based upon the assumption that when in molten globule state, the exposed hydrophobic clusters of protein are readily bound by the nonpolar anilino-naphthalene moiety of ANS molecules which then produce brilliant fluorescence. In this work, we explored the acid-induced unfolding pathway of chymopapain, a cysteine proteases from Carica papaya, by monitoring the conformational changes over a pH range 1.0–7.4 by circular dichroism, intrinsic fluorescence, ANS binding, acrylamide quenching, isothermal titration calorimetry (ITC) and dynamic light scattering (DLS). The spectroscopic measurements showed that although maximum ANS fluorescence intensity was observed at pH 1.0, however protein exhibited ∼80% loss of secondary structure which does not comply with the characteristics of a typical MG-state. In contrast at pH 1.5, chymopapain retains substantial amount of secondary structure, disrupted side chain interactions, increased hydrodynamic radii and nearly 30-fold increase in ANS fluorescence with respect to the native state, indicating that MG-state exists at pH 1.5 and not at pH 1.0. ITC measurements revealed that ANS molecules bound to chymopapain via hydrophobic interaction were more at pH 1.5 than at pH 1.0. However, a large number of ANS molecules were also involved in electrostatic interaction with protein at pH 1.0 which, together with hydrophobically interacted molecules, may be responsible for maximum ANS fluorescence. We conclude that maximum ANS-fluorescence alone may not be the criteria for determining the MG of chymopapain. Hence a comprehensive structural analysis of the intermediate is essentially required. PMID:23209794

  15. Expression, purification, and characterization of recombinant human and murine milk fat globule-epidermal growth factor-factor 8.

    PubMed

    Castellanos, Erick R; Ciferri, Claudio; Phung, Wilson; Sandoval, Wendy; Matsumoto, Marissa L

    2016-08-01

    Milk fat globule-epidermal growth factor-factor 8 (MFG-E8), as its name suggests, is a major glycoprotein component of milk fat globules secreted by the mammary epithelium. Although its role in milk fat production is unclear, MFG-E8 has been shown to act as a bridge linking apoptotic cells to phagocytes for removal of these dying cells. MFG-E8 is capable of bridging these two very different cell types via interactions through both its epidermal growth factor (EGF)-like domain(s) and its lectin-type C domains. The EGF-like domain interacts with αVβ3 and αVβ5 integrins on the surface of phagocytes, whereas the C domains bind phosphatidylserine found on the surface of apoptotic cells. In an attempt to purify full-length, recombinant MFG-E8 expressed in either insect cells or CHO cells, we find that it is highly aggregated. Systematic truncation of the domain architecture of MFG-E8 indicates that the C domains are mainly responsible for the aggregation propensity. Addition of Triton X-100 to the conditioned cell culture media allowed partial recovery of non-aggregated, full-length MFG-E8. A more comprehensive detergent screen identified CHAPS as a stabilizer of MFG-E8 and allowed purification of a significant portion of non-aggregated, full-length protein. The CHAPS-stabilized recombinant MFG-E8 retained its natural ability to bind both αVβ3 and αVβ5 integrins and phosphatidylserine suggesting that it is properly folded and active. Herein we describe an efficient purification method for production of non-aggregated, full-length MFG-E8. PMID:27102803

  16. 1-Anilino-8-naphthalene sulfonate (ANS) is not a desirable probe for determining the molten globule state of chymopapain.

    PubMed

    Qadeer, Atiyatul; Rabbani, Gulam; Zaidi, Nida; Ahmad, Ejaz; Khan, Javed M; Khan, Rizwan H

    2012-01-01

    The molten globule (MG) state of proteins is widely detected through binding with 1-anilino-8-naphthalene sulphonate (ANS), a fluorescent dye. This strategy is based upon the assumption that when in molten globule state, the exposed hydrophobic clusters of protein are readily bound by the nonpolar anilino-naphthalene moiety of ANS molecules which then produce brilliant fluorescence. In this work, we explored the acid-induced unfolding pathway of chymopapain, a cysteine proteases from Carica papaya, by monitoring the conformational changes over a pH range 1.0-7.4 by circular dichroism, intrinsic fluorescence, ANS binding, acrylamide quenching, isothermal titration calorimetry (ITC) and dynamic light scattering (DLS). The spectroscopic measurements showed that although maximum ANS fluorescence intensity was observed at pH 1.0, however protein exhibited ∼80% loss of secondary structure which does not comply with the characteristics of a typical MG-state. In contrast at pH 1.5, chymopapain retains substantial amount of secondary structure, disrupted side chain interactions, increased hydrodynamic radii and nearly 30-fold increase in ANS fluorescence with respect to the native state, indicating that MG-state exists at pH 1.5 and not at pH 1.0. ITC measurements revealed that ANS molecules bound to chymopapain via hydrophobic interaction were more at pH 1.5 than at pH 1.0. However, a large number of ANS molecules were also involved in electrostatic interaction with protein at pH 1.0 which, together with hydrophobically interacted molecules, may be responsible for maximum ANS fluorescence. We conclude that maximum ANS-fluorescence alone may not be the criteria for determining the MG of chymopapain. Hence a comprehensive structural analysis of the intermediate is essentially required. PMID:23209794

  17. Identification of major milk fat globule membrane proteins from pony mare milk highlights the molecular diversity of lactadherin across species.

    PubMed

    Cebo, C; Rebours, E; Henry, C; Makhzami, S; Cosette, P; Martin, P

    2012-03-01

    Although several studies have been devoted to the colloidal and soluble protein fractions of mare milk (caseins and whey proteins), to date little is known about the milk fat globule membrane (MFGM) protein fraction from mare milk. The objective of this study was thus to describe MFGM proteins from Equidae milk and to compare those proteins to already described MFGM proteins from cow and goat milk. Major MFGM proteins (namely, xanthine oxidase, butyrophilin, lactadherin, and adipophilin) already described in cow or goat milk were identified in mare milk using mass spectrometry. However, species-specific peculiarities were observed for 2 MFGM proteins: butyrophilin and lactadherin. A highly glycosylated 70-kDa protein was characterized for equine butyrophilin, whereas proteins of 64 and 67 kDa were characterized for cow and goat butyrophilin, respectively. Prominent differences across species were highlighted for lactadherin. Indeed, whereas 1 or 2 polypeptide chains were identified, respectively, by peptide mass fingerprinting matrix-assisted laser desorption/ionization-time of flight analysis for caprine and bovine lactadherin, 4 isoforms (60, 57, 48, and 45 kDa) for lactadherin from mare milk were identified by 10% sodium dodecyl sulfate-PAGE. Polymerase chain reaction experiments on lactadherin transcripts isolated from milk fat globules revealed the existence of 2 distinct lactadherin transcripts in the horse mammary gland. Cloning and sequencing of both transcripts encoding lactadherin showed an alternative use of a cryptic splice site located at the end of intron 5 of the equine lactadherin-encoding gene. This event results in the occurrence of an additional alanine (A) residue in the protein that disrupts a putative atypical N-glycosylation site (VNGC/VNAGC) described in human lactadherin. Liquid chromatography coupled with tandem mass spectrometry analyses confirmed the existence of both lactadherin variants in mare MFGM. We show here that lactadherin from

  18. Determination of the physical parameters of Bok-globules by means of a stochastical radiative transfer method

    NASA Astrophysics Data System (ADS)

    Hengel, C.; Hegmann, M.; Röllig, M.; Kegel, W. H.

    During the last years, one of the key projects of the Astrophysics group at the University of Frankfurt was the theoretical examination of the influence of turbulence and density fluctuations on the formation of interstellar molecular lines, especially CO lines (Albrecht & Kegel 1987, Kegel et al. 1993, Piehler & Kegel 1995, Hegmann 1999). Based on an approach by G. Traving and collaborators (cf. Gail et al. 1974), a numerical code has been developed to deal with the NLTE problem in an isothermal spherical cloud being stabelized by turbulent and thermal pressure, considering the turbulent velocity field to be stochastic. Our model has been primarily constructed to achieve theoretical insight in the fundamental mechanisms of line formation under more realistic conditions. In view of the stage of development, the model has actually reached, we seriously think of it as an alternative tool for the evaluation of molecular lines emitted by molecular clouds, especially as the model assumptions are certainly closer to reality than the assumptions behind the standard evaluation methods such as e. g. LVG analysis. The objects the physics of which we believe to be closest to our model assumptions are starless Bok globules. We thus have performed observations at the HHT, where we have collected data of five Bok globules in the CO(2-1), CO(3-2), 13CO(2-1) and C18O(2-1) lines. In my contribution I will adress the question, if and how the physical parameters derived by our analysis of the observational data (central H2 density, temperature, correlation length of the turbulent velocity field, and mean square turbulent velocity) differ from the results of an LVG analysis (they do!) and what these findings imply from a physical point of view as well as from a critical viewpoint on the practice of data evaluation. I will talk about problems of our model at its current stage and possible consequences for an improvement of the model, and I will finally give an outlook, how, with

  19. Alteration Assemblages in Martian Meteorites: Implications for Near-Surface Processes

    NASA Astrophysics Data System (ADS)

    Bridges, J. C.; Catling, D. C.; Saxton, J. M.; Swindle, T. D.; Lyon, I. C.; Grady, M. M.

    2001-04-01

    The SNC (Shergotty-Nakhla-Chassigny) meteorites have recorded interactions between martian crustal fluids and the parent igneous rocks. The resultant secondary minerals - which comprise up to ~1 vol.% of the meteorites - provide information about the timing and nature of hydrous activity and atmospheric processes on Mars. We suggest that the most plausible models for secondary mineral formation involve the evaporation of low temperature (25 - 150 °C) brines. This is consistent with the simple mineralogy of these assemblages - Fe-Mg-Ca carbonates, anhydrite, gypsum, halite, clays - and the chemical fractionation of Ca-to Mg-rich carbonate in ALH84001 "rosettes". Longer-lived, and higher temperature, hydrothermal systems would have caused more silicate alteration than is seen and probably more complex mineral assemblages. Experimental and phase equilibria data on carbonate compositions similar to those present in the SNCs imply low temperatures of formation with cooling taking place over a short period of time (e.g. days). The ALH84001 carbonate also probably shows the effects of partial vapourisation and dehydration related to an impact event post-dating the initial precipitation. This shock event may have led to the formation of sulphide and some magnetite in the Fe-rich outer parts of the rosettes. Radiometric dating (K-Ar, Rb-Sr) of the secondary mineral assemblages in one of the nakhlites (Lafayette) suggests that they formed between 0 and 670 Myr, and certainly long after the crystallisation of the host igneous rocks. Crystallisation of ALH84001 carbonate took place 0.5 Gyr after the parent rock. These age ranges and the other research on these assemblages suggest that environmental conditions conducive to near-surface liquid water have been present on Mars periodically over the last ~1 Gyr. This fluid activity cannot have been continuous over geological time because in that case much more silicate alteration would have taken place in the meteorite parent

  20. A statistical theory of coil-to-globule-to-coil transition of a polymer chain in a mixture of good solvents

    NASA Astrophysics Data System (ADS)

    Budkov, Yu. A.; Kolesnikov, A. L.; Kalikin, N. N.; Kiselev, M. G.

    2016-05-01

    We present an off-lattice statistical model of a single polymer chain in mixed-solvent media. Taking into account the polymer conformational entropy, renormalization of solvent composition near the polymer backbone, the universal intermolecular excluded-volume and van der Waals interactions within the self-consistent field theory, the reentrant coil-to-globule-to-coil transition (co-nonsolvency) has been described in this paper. For convenience we split the system volume in two parts: the volume occupied by the polymer chain and the volume of bulk solution. Considering the equilibrium between two sub-volumes, the polymer solvation free energy as a function of radius of gyration and co-solvent mole fraction within internal polymer volume has been obtained. Minimizing the free energy of solvation with respect to its arguments, we show two qulitatively different regimes of co-nonsolvency. Namely, at sufficiently high temperature the reentrant coil-to-globule-to-coil transition proceeds smoothly. On the contrary, when the temperature drops below a certain threshold value a coil-globule transition occurs in the regime of first-order phase transition, i.e., discontinuous changes of the radius of gyration and the local co-solvent mole fraction near the polymer backbone. We show that, when the collapse of the polymer chain takes place, the entropy and enthalpy contributions to the solvation free energy of the globule strongly grow. From the first principles of statistical thermodynamics we confirm earlier speculations based on the MD simulations results that the co-nonsolvency is the essentially enthalpic-entropic effect and is caused by enthalpy-entropy compensation. We show that the temperature dependences of the solution heat capacity change due to the solvation of the polymer chain are in qualitative agreement with the differential scanning calorimetry data for PNIPAM in aqueous methanol.

  1. Rod-to-Globule Transition of pDNA/PEG-Poly(l-Lysine) Polyplex Micelles Induced by a Collapsed Balance Between DNA Rigidity and PEG Crowdedness.

    PubMed

    Tockary, Theofilus A; Osada, Kensuke; Motoda, Yusuke; Hiki, Shigehiro; Chen, Qixian; Takeda, Kaori M; Dirisala, Anjaneyulu; Osawa, Shigehito; Kataoka, Kazunori

    2016-03-01

    The role of poly(ethylene-glycol) (PEG) in rod-shaped polyplex micelle structures, having a characteristic core of folded plasmid DNA (pDNA) and a shell of tethered PEG chains, is investigated using PEG-detachable polyplex micelles. Rod shapes undergo change to compacted globule shapes by removal of PEG from polyplex micelles prepared from block copolymer with acid-labile linkage between PEG and poly(l-lysine) (PLys) through exposure to acidic milieu. This structural change supports the previous investigation on the rod shapes that PEG shell prevents the DNA structure from being globule shaped as the most favored structure in minimizing surface area. Noteworthy, despite the PEG is continuously depleted, the structural change does not occur in gradual shortening manner but the rod shapes keep their length unchanged and abruptly transform into globule shapes. Analysis of PEG density reveals the transition occurred when tethered PEG of rod shapes has decreased to a critical crowdedness, i.e., discontacted with neighboring PEG, which eventually illuminates another contribution, rigidity of DNA packaged as bundle in the rod shapes, in addition to the steric repulsion of PEG, in sustaining rod shapes. This investigation affirms significant role of PEG and also DNA rigidity as bundle in the formation of rod-shaped structures enduring the quest of compaction of charge-neutralized DNA in the polyplex micelles. PMID:26426541

  2. Characterization of sub-nanosecond dynamics of the molten globule state of α-lactalbumin using quasielastic neutron scattering and molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Tarek, Mounir; Neumann, Dan A.; Tobias, Douglas J.

    2003-08-01

    The dynamics of α-lactalbumin in the native and molten globule states in solution was investigated using quasielastic neutron scattering and molecular dynamics simulations. We generated 2 nanosecond molecular dynamics trajectories at 300 K of α-lactalbumin solvated in a water box in the native state, and a putative member of the ensemble of conformations of the molten globule state generated by simulation at high temperature. Overall the agreement between the measured and calculated dynamical structure factors is good. Preliminary analysis of the simulated dynamics of the molten globule state revealed a strong heterogeneity of motions along the protein backbone, with larger amplitudes in the regions of the protein that unfold, mainly the β-sheet region. The results presented here demonstrate the utility of using a combination of neutron scattering measurements and molecular dynamics simulations to characterize and quantify, in a sequence-specific fashion, the differences in dynamics between the native and partially folded states of proteins on the time scale (˜100 ps) and length scale (a few to tens of Å) probed by current neutron spectrometers.

  3. Detecting cold H2 globules in the outer Galactic disc by microlensing towards the Maffei 1 elliptical

    NASA Astrophysics Data System (ADS)

    Fux, R.

    2005-02-01

    A candidate source of dark matter in spiral galaxies is cold molecular hydrogen globules with a condensed central core and a disc-like space distribution probably similar to that of neutral hydrogen. This paper shows that the H2 cores are sufficiently compact and massive to be detected by microlensing in the outer Galactic disc and that the Maffei 1 elliptical galaxy, at a distance of 3 Mpc and Galactic latitude b=-0.6°, offers an ideal target for such an experiment. The microlensing optical depth of H2 cores along the line of sight to this galaxy is estimated to τ˜ 0.7× 10-6 if most of the dark mass in the Milky Way resides in such cores, and the typical event timescale to ⪉ 1 day. Detection rates are computed both in the classical and pixel lensing approaches in the I- and K-bands, and for a representative selection of existing observing facilities. In the more efficient pixel lensing case, two 10-h observing runs, separated in time by at least several days, should yield of the order of 10 positive detections at the 5σ level using ground-based 8 m-class telescopes in the K-band or the Hubble Space Telescope ACS camera in the I-band, and the corresponding fraction of events with timescale measurable to an accuracy better than 50% amounts to about 9% and 4% respectively for these observing alternatives.

  4. Short communication: Annatto in Cheddar cheese-derived whey protein concentrate is primarily associated with milk fat globule membrane.

    PubMed

    Zhu, D; Damodaran, S

    2012-02-01

    The yellow color of Cheddar cheese whey arises from a residual amount of annatto that partitions into the whey during Cheddar cheese manufacture. Bleaching of the color using hydrogen peroxide or benzoyl peroxide is often a prerequisite to produce an acceptable neutral-colored whey protein concentrate and isolate. However, the use of these strong oxidizing agents often generates off-flavors as a result of lipid oxidation and results in loss of nutritive value due to protein oxidation. The objective of this study was to determine the extent of partitioning of annatto between protein, milk fat globule membrane (MFGM), and aqueous (serum) phases of cheese whey so that a simple method can be developed to remove annatto from cheese whey. The MFGM was separated from Cheddar cheese whey using a recently developed novel method. Quantitative analysis of the distribution of annatto in the fat-free whey protein isolate (WPI), the MFGM fractions, and the serum phase revealed that annatto was not bound to the protein fraction but was mostly distributed between the serum phase and the MFGM fraction. The results showed that a colorless WPI or whey protein concentrate could be produced from Cheddar cheese whey by separation of MFGM from the whey, followed by diafiltration. This approach will negate the need for using bleaching agents. PMID:22281326

  5. Comparison of emulsifying properties of milk fat globule membrane materials isolated from different dairy by-products.

    PubMed

    Phan, T T Q; Le, T T; Van der Meeren, P; Dewettinck, K

    2014-01-01

    Emulsifying properties of milk fat globule membrane (MFGM) materials isolated from reconstituted buttermilk (BM; i.e., BM-MFGM) and BM whey (i.e., whey-MFGM), individually or in mixtures with BM powder (BMP) were compared with those of a commercial dairy ingredient (Lacprodan PL-20; Arla Foods Ingredients Group P/S, Viby, Denmark), a material rich in milk polar lipids and proteins. The particle size distribution, viscosity, interfacial protein, and polar lipids load of oil-in-water emulsions prepared using soybean oil were examined. Pronounced droplet aggregation was observed with emulsions stabilized with whey-MFGM or with a mixture of whey-MFGM and BMP. No aggregation was observed for emulsions stabilized with BM-MFGM, Lacprodan PL-20, or a mixture of BM-MFGM and BMP. The surface protein load and polar lipids load were lowest in emulsions with BM-MFGM. The highest protein load and polar lipids load were observed for emulsions made with a mixture of whey-MFGM and BMP. The differences in composition of MFGM materials, such as in whey proteins, caseins, MFGM-specific proteins, polar lipids, minerals, and especially their possible interactions determine their emulsifying properties. PMID:24913653

  6. Stat3 controls cell death during mammary gland involution by regulating uptake of milk fat globules and lysosomal membrane permeabilization

    PubMed Central

    Resemann, Henrike K.; Ramos-Montoya, Antonio; Skepper, Jeremy; Watson, Christine J.

    2014-01-01

    We have previously demonstrated that Stat3 regulates lysosomal mediated-programmed cell death (LM-PCD) during mouse mammary gland involution in vivo. However, the mechanism that controls the release of lysosomal cathepsins to initiate cell death in this context has not been elucidated. We show here that Stat3 regulates the formation of large lysosomal vacuoles that contain triglyceride. Furthermore, we demonstrate that milk fat globules (MFGs) are toxic to epithelial cells and that, when applied to purified lysosomes, the MFG hydrolysate oleic acid potently induces lysosomal leakiness. Additionally, uptake of secreted MFGs coated in butyrophilin 1A1 is diminished in Stat3 ablated mammary glands while loss of the phagocytosis bridging molecule MFG-E8 results in reduced leakage of cathepsins in vivo. We propose that Stat3 regulates LM-PCD in mouse mammary gland by switching cellular function from secretion to uptake of MFGs. Thereafter, perturbation of lysosomal vesicle membranes by high levels of free fatty acids results in controlled leakage of cathepsins culminating in cell death. PMID:25283994

  7. Pulsed electric field processing preserves the antiproliferative activity of the milk fat globule membrane on colon carcinoma cells.

    PubMed

    Xu, S; Walkling-Ribeiro, M; Griffiths, M W; Corredig, M

    2015-05-01

    The present work evaluated the effect of processing on the antiproliferative activities of milk fat globule membrane (MFGM) extracts. The antiproliferative activity on human adenocarcinoma HT-29 cells of untreated MFGM extracts were compared with those extracted from pasteurized cream, thermally treated cream, or cream subjected to pulsed electrical field (PEF) processing. The PEF with a 37 kV/cm field strength applied for 1,705μs at 50 and 65°C was applied to untreated cream collected from a local dairy. Heating at 50 or 65°C for 3min (the passage time in the PEF chamber) was also tested to evaluate the heating effect during PEF treatments. The MFGM extracted from pasteurized cream did not show an antiproliferative activity. On the other hand, isolates from PEF-treated cream showed activity similar to that of untreated samples. It was also shown that PEF induced interactions between β-lactoglobulin and MFGM proteins at 65°C, whereas the phospholipid composition remained unaltered. This work demonstrates the potential of PEF not only a means to produce a microbiologically safe product, but also as a process preserving the biofunctionality of the MFGM. PMID:25726115

  8. Effect of hydrostatic pressure on conformational changes of canine milk lysozyme between the native, molten globule, and unfolded states.

    PubMed

    Watanabe, Masahiro; Aizawa, Tomoyasu; Demura, Makoto; Nitta, Katsutoshi

    2004-11-01

    The effect of pressure on the unfolding of the native (N) and molten globule (MG) state of canine milk lysozyme (CML) was examined using ultraviolet (UV) spectroscopy at pH 4.5 and 2.0, respectively. It appeared that the thermally induced unfolding was promoted by the increase of pressure from atmospheric to 100 MPa, which indicates that both the N and MG states of CML unfolded with the decrease of the partial molar volume change (DeltaV). The volume changes needed for unfolding were estimated from the free energy change vs. pressure plots, and these volume changes became less negative from 20 to 60 degrees C. The DeltaV values at 25 degrees C were obtained for the N-MG (-46 cm3/mol) and MG-unfolded-state (U) transition (-40 cm3/mol). With regards to the MG-U transition, this value is contrastive to that of bovine alpha-lactalbumin (BLA) (0.9 cm3/mol), which is homologous to CML. Previous studies revealed that the MG state of CML was significantly more stable, and closer to the N state in structure, than that of BLA. In contrast to the swollen hydrophobic core of the MG state of BLA, our results suggest that the MG state of CML possesses a tightly packed hydrophobic core into which water molecules cannot penetrate. PMID:15488764

  9. Sub-Micrometer-Scale Mapping of Magnetite Crystals and Sulfur Globules in Magnetotactic Bacteria Using Confocal Raman Micro-Spectrometry

    PubMed Central

    Eder, Stephan H. K.; Gigler, Alexander M.; Hanzlik, Marianne; Winklhofer, Michael

    2014-01-01

    The ferrimagnetic mineral magnetite is biomineralized by magnetotactic microorganisms and a diverse range of animals. Here we demonstrate that confocal Raman microscopy can be used to visualize chains of magnetite crystals in magnetotactic bacteria, even though magnetite is a poor Raman scatterer and in bacteria occurs in typical grain sizes of only 35–120 nm, well below the diffraction-limited optical resolution. When using long integration times together with low laser power (<0.25 mW) to prevent laser induced damage of magnetite, we can identify and map magnetite by its characteristic Raman spectrum (303, 535, 665 ) against a large autofluorescence background in our natural magnetotactic bacteria samples. While greigite (cubic ; Raman lines of 253 and 351 ) is often found in the Deltaproteobacteria class, it is not present in our samples. In intracellular sulfur globules of Candidatus Magnetobacterium bavaricum (Nitrospirae), we identified the sole presence of cyclo-octasulfur (: 151, 219, 467 ), using green (532 nm), red (638 nm) and near-infrared excitation (785 nm). The Raman-spectra of phosphorous-rich intracellular accumulations point to orthophosphate in magnetic vibrios and to polyphosphate in magnetic cocci. Under green excitation, the cell envelopes are dominated by the resonant Raman lines of the heme cofactor of the b or c-type cytochrome, which can be used as a strong marker for label-free live-cell imaging of bacterial cytoplasmic membranes, as well as an indicator for the redox state. PMID:25233081

  10. Altered concentrate to forage ratio in cows ration enhanced bioproduction of specific size subpopulation of milk fat globules.

    PubMed

    Mesilati-Stahy, Ronit; Moallem, Uzi; Magen, Yogev; Argov-Argaman, Nurit

    2015-07-15

    The mechanism underlying the shift in milk-fat-globule (MFG) mean diameter upon changing the concentrate-to-forage ratio in dairy cow rations was investigated. Cows were fed high-concentrate low-forage (HCLF) or high-forage low-concentrate (LCHF) rations for 4 weeks. Mean diameter of MFG, determined in raw whole milk, was 0.4 μm larger in the LCHF-fed vs. HCLF-fed group. The main compositional differences between treatments were found in a specific MFG subgroup with the diameter of 3.3 μm (F1), with higher capric, lauric, myristic and lower oleic acid concentrations in HCLF vs. LCHF milk. Similarly, lipid concentration differences between treatments were only found in F1, with higher triglyceride and phosphatidylethanolamine, and lower sphingomyelin concentrations in LCHF vs. HCLF milk. The higher MFG mean diameter in whole raw LCHF milk might therefore be attributed to increased secretion of F1-group MFG, while fat content and composition in the other MFG size groups remains unchanged. PMID:25722155

  11. Formations of Bacteria-like Textures by dynamic reactions in Meteorite and Syntheses

    NASA Astrophysics Data System (ADS)

    Miura, Y.

    2009-05-01

    1. Introduction Spherule texture can be formed in dynamic reaction during meteoritic impact in air. However, there are no reports on nano-bacteria-like (i.e. spherule-chained) textures with iron (and Nickel) oxides (with chlorine) in composition and micro-texture with 100nm order [1] in meteorite and synthetic experiment. The purpose of the present study is to elucidate spherule-chained texture with micro-texture of 100nm in order found in the Kuga iron meteorite, Iwakuni, Yamaguchi, Japan, and its first artificial synthesis in laboratory. 2. Two textures in the Kuga meteorite: The Kuga iron meteorite found in Kuga, Iwakuni, Yamaguchi, Japan reveals spherule-chained texture with Fe, Ni-rich composition with 10μm in size, where each spherule contained "long micro-texture in 100nm in size"[1,2]. The complex texture of flow and chained shapes can be found only in the fusion crust of the meteorite formed by quenched and random processes with vapor-melting process in air of the Earth. The FE-ASEM with EDX analyses by an in-situ observation indicate that the matrix of the spherule-chained texture with Fe, Ni, O-rich (with minor Cl) composition is carbon-rich composition formed by impact reactions in air. 3. Comparison with Martian meteorite Remnant of life in ocean can be found by mineralized fossil, which can be found in the Martian meteorite ALH84001 as bacteria-like chained texture of magnetite in composition (in 100nm order) around carbonate spherules [3]. Similarity of bacteria-like texture of the ALH84001 compared with the Kuga meteorites in this study are composition of Fe-rich, C-bearing, and chained texture of small size replaced by Fe and O-rich composition in air. Major difference of these textures is no carbonates minerals in the Kuga meteorite at dynamic reaction in air [1, 2, 3]. 4. First synthesis of bacteria- like akaganeite: A bacteria-like texture with Fe oxides (with minor chlorine as akaganeite-like compositions) is synthesized by chlorine and water

  12. The Geologic History of Mars: An Astrobiology Perspective

    NASA Technical Reports Server (NTRS)

    Gibson, Everett K.; Westall, Frances; McKay, David S.; Thomas-Keprta, Kathie; Socki, Richard A.

    2000-01-01

    Fourteen SNC meteorites contain information which must be incorporated with recent spaceflight data for developing Mars' geologic history. SNCs have crystallization ages of 4500 to 160 m.y. Tle oldest meteorite ALH84001 contains information on the Noachian period of Mars' history. There are no meteorites from the Hesperian period and the remaining 13 meteorites fall into two age groups within the Amazonian: The nakhlites around 1300 m.y. and the shergottites between 800-160 m.y. Oxygen isotopic analysis of Martian samples shows two distinct O2 reservoirs throughout Martian history indicating late additions of volatiles and a lack of plate tectonics prior to 3.9 Gy. Evidence for percolation of aqueous brines through impact-produced fractures in the rocky surface is contained in the 3.9 Gy-old ALH84001 carbonate deposits. These carbonates precipitated at approx. 100 C. At this time life had already evolved on Earth. Early Mars could have hosted life similar to the bacteria that inhabited early Earth. Potential microorganisms could have been transported into fractures by carbonate-bearing waters and their remains could have become incorporated into the precipitated carbonate. Since Mars had a weak magnetic field at this time, it can be hypothesized that some of the Martian microorganisms may have been similar to terrestrial magnetotactic bacteria. Over geologic time episodic cratering, and tectonic events have occurred on Mars along with the periodic release of subsurface waters which may have produced clays within SNC meteorites. The geochemical data contained within SNC meteorites complements previous observational data and the recent Mars Global Surveyor data to provide a geological and environmental history which spans almost the entire lifespan on Mars. One of the outstanding features of this model is the possible creation of an early (about 4 Gy) volatile reservoir distinct from the outgassed Mars volatiles, and the persistence of this reservoir throughout most

  13. MUC-1 expression in pleomorphic adenomas using two human milk fat globule protein membrane antibodies (HMFG-1 and HMFG-2)

    PubMed Central

    PONCE-BRAVO, Santa; LEDESMA-MONTES, Constantino; GARCÉS-ORTÍZ, Maricela

    2015-01-01

    Pleomorphic adenoma (PA) is the most common salivary gland tumor and its microscopic features and histogenesis are a matter of debate. Human milk fat globule protein membrane (HMFG) monoclonal antibodies (MoAbs) comprise a set of antibodies against the mucin 1 (MUC-1) protein detected in several salivary gland tumors. Objective The aim of this study was to assess the immunoexpression of the PA neoplastic cells to MUC-1 protein using HMFG-1 and HMFG-2 MoAbs, contrasting these results with those from normal salivary gland tissue. Material and Methods Immunohistochemical detection of MUC-1 protein using HMFG-1 and HMFG-2 MoAbs was made in 5 mm thick, paraffin embedded slides, and the avidin-biotin method was used. Results Positivity to HMFG-1 and HMFG-2 MoAbs was found in ductal, squamous metaplastic and neoplastic myoepithelial cells, keratin pearls and intraductal mucous material. Two kinds of myoepithelial cells were identified: classic myoepithelial cells around ducts were negative to both MoAbs, and modified myoepithelial cells were positive to both MoAbs. This last cellular group of the analyzed tumors showed similar MUC-1 immunoexpression to ductal epithelial cells using both HMFG antibodies. Intraductal mucous secretion was also HMFG-1 and HMFG-2 positive. Conclusions Our results showed there are two kinds of myoepithelial cells in PA. The first cellular group is represented by the different kinds of neoplastic myoepithelial cells and is HMFG-positive. The second one is HMFG-negative and represented by the neoplastic myoepithelial cells located around the ducts. PMID:26221920

  14. Sub-micrometer-scale mapping of magnetite crystals and sulfur globules in magnetotactic bacteria using confocal Raman micro-spectrometry.

    PubMed

    Eder, Stephan H K; Gigler, Alexander M; Hanzlik, Marianne; Winklhofer, Michael

    2014-01-01

    The ferrimagnetic mineral magnetite Fe3O4 is biomineralized by magnetotactic microorganisms and a diverse range of animals. Here we demonstrate that confocal Raman microscopy can be used to visualize chains of magnetite crystals in magnetotactic bacteria, even though magnetite is a poor Raman scatterer and in bacteria occurs in typical grain sizes of only 35-120 nm, well below the diffraction-limited optical resolution. When using long integration times together with low laser power (<0.25 mW) to prevent laser induced damage of magnetite, we can identify and map magnetite by its characteristic Raman spectrum (303, 535, 665 cm(-1)) against a large autofluorescence background in our natural magnetotactic bacteria samples. While greigite (cubic Fe3S4; Raman lines of 253 and 351 cm(-1)) is often found in the Deltaproteobacteria class, it is not present in our samples. In intracellular sulfur globules of Candidatus Magnetobacterium bavaricum (Nitrospirae), we identified the sole presence of cyclo-octasulfur (S8: 151, 219, 467 cm(-1)), using green (532 nm), red (638 nm) and near-infrared excitation (785 nm). The Raman-spectra of phosphorous-rich intracellular accumulations point to orthophosphate in magnetic vibrios and to polyphosphate in magnetic cocci. Under green excitation, the cell envelopes are dominated by the resonant Raman lines of the heme cofactor of the b or c-type cytochrome, which can be used as a strong marker for label-free live-cell imaging of bacterial cytoplasmic membranes, as well as an indicator for the redox state. PMID:25233081

  15. Acid-induced molten globule state of a prion protein: crucial role of Strand 1-Helix 1-Strand 2 segment.

    PubMed

    Honda, Ryo P; Yamaguchi, Kei-ichi; Kuwata, Kazuo

    2014-10-31

    The conversion of a cellular prion protein (PrP(C)) to its pathogenic isoform (PrP(Sc)) is a critical event in the pathogenesis of prion diseases. Pathogenic conversion is usually associated with the oligomerization process; therefore, the conformational characteristics of the pre-oligomer state may provide insights into the conversion process. Previous studies indicate that PrP(C) is prone to oligomer formation at low pH, but the conformation of the pre-oligomer state remains unknown. In this study, we systematically analyzed the acid-induced conformational changes of PrP(C) and discovered a unique acid-induced molten globule state at pH 2.0 termed the "A-state." We characterized the structure of the A-state using far/near-UV CD, 1-anilino-8-naphthalene sulfonate fluorescence, size exclusion chromatography, and NMR. Deuterium exchange experiments with NMR detection revealed its first unique structure ever reported thus far; i.e. the Strand 1-Helix 1-Strand 2 segment at the N terminus was preferentially unfolded, whereas the Helix 2-Helix 3 segment at the C terminus remained marginally stable. This conformational change could be triggered by the protonation of Asp(144), Asp(147), and Glu(196), followed by disruption of key salt bridges in PrP(C). Moreover, the initial population of the A-state at low pH (pH 2.0-5.0) was well correlated with the rate of the β-rich oligomer formation, suggesting that the A-state is the pre-oligomer state. Thus, the specific conformation of the A-state would provide crucial insights into the mechanisms of oligomerization and further pathogenic conversion as well as facilitating the design of novel medical chaperones for treating prion diseases. PMID:25217639

  16. The Effect of pH on Globular State of Lipase-3646; an Appropriate Model for Molten Globule Investigations.

    PubMed

    Golaki, Bahram Pooreydy; Aminzadeh, Saeed; Karkhane, Ali Asghar; Yakhchali, Bagher; Farrokh, Parisa; Jazii, Ferdous Rastgar; Nadimifar, Mohammadsadegh

    2015-08-01

    Secondary structure content of proteins in molten globule state is relatively constant while the quantity of tertiary structures clearly declines due to alterations in side-chain packing. In the present study, we analyze the MG state of lipase-3646 for the first time. We introduce lipase-3646 as an appropriate model for investigating the properties and behavior of a protein in MG state as well as folding pathway. Applying fluorescence spectroscopy we measured both intrinsic and extrinsic fluorescence of lipase-3646 in a pH range from 1.0 to 12.0. It was found that at pH 3.0 the protein acquires a MG state. Applying far-UV circular dichroism (CD), our analysis on the secondary structure of lipase-3646 revealed a slight change in the MG state intermediate (pH 3.0) compared to the native state (pH 8.5), which this amount of change is common for MG. Measurements in near-UV CD also showed a significant change in the enzyme conformation at pH 3.0 in comparison with the pH 8.5 wherein the protein acquires its native structure. Quenching the fluorescence by applying acrylamide, the amount 23 and 35 M(-1) were measured at pHs 8.5 and 3.0 respectively for stern-volmer constant (KSV). An increase in the enzyme molecular volume in the MG state was confirmed by gel filtration chromatography. PMID:26239273

  17. The molten globule of β(2)-microglobulin accumulated at pH 4 and its role in protein folding.

    PubMed

    Mukaiyama, Atsushi; Nakamura, Takashi; Makabe, Koki; Maki, Kosuke; Goto, Yuji; Kuwajima, Kunihiro

    2013-01-23

    The acid transition of β(2)-microglobulin (β2m) was studied by tryptophan fluorescence, peptide circular dichroism, and NMR spectroscopy. The protein exhibits a three-state transition with an equilibrium intermediate accumulated at pH4 (25°C). The pH4 intermediate has typical characteristics of the molten globule (MG) state; it showed a native-like secondary structure without specific side-chain tertiary structure, and the hydrodynamic radius determined by pulse field gradient NMR was only 20% larger than that of the native state. The accumulation of the pH4 intermediate is very analogous to the behavior of apomyoglobin, for which the pH4 MG has been well characterized, although β2m, a β-protein, is structurally very different from α-helical apomyoglobin. NMR pH titration of histidine residues of β2m has also indicated that His84 has an abnormally low pK(a) value in the native state. From the pH dependence of the unfolding transition, the protonations of this histidine and 10 weakly abnormal carboxylates triggered the transition from the native to the MG state. This behavior is again analogous to that of apomyoglobin, suggesting a common mechanism of production of the pH4 MG. In contrast to the folding of apomyoglobin, in which the MG was equivalent to the burst-phase kinetic folding intermediate, the burst-phase refolding intermediate of β2m, detected by stopped-flow circular dichroism, was significantly more structured than the pH4 intermediate. It is proposed that the folding of β2m from its acid-denatured state takes place in the following order: denatured state→MG→burst-phase intermediate→native state. PMID:23154171

  18. Shedding and enrichment of the glycolipid-anchored complement lysis inhibitor protectin (CD59) into milk fat globules.

    PubMed

    Hakulinen, J; Meri, S

    1995-07-01

    Protectin (CD59) is a glycolipid-anchored inhibitor of the membrane attack complex (MAC) of human complement (C) that protects blood cells, endothelial cells and various epithelial cells from C-mediated lysis. Because of its activities protectin is a candidate molecule for use in the treatment of paroxysmal nocturnal haemoglobinuria or conditions where MAC causes tissue damage. Soluble, phospholipid-free forms of protectin have been isolated from human urine and produced in recombinant form, but they have only a relatively weak C lysis-inhibiting activity. In the present study we have looked for functionally active protectin in human breast milk. Milk is rich in fat droplets, milk fat globules (MFG), that are enveloped in a plasma membrane derived from secretory cells of the mammary gland. The membranes of MFG contain a variety of glycoproteins expressed by the mammary epithelial cells. Both immunofluorescence and immunoblotting analysis demonstrated that protectin was strongly expressed on human MFG. In sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, MFG protectin (CD59M) appeared as distinct bands with apparent molecular weights of 19,000-23,000 MW, similar to protectin extracted from MCF7 breast carcinoma cells. CD59M in breast milk was functionally active and had a glycophospholipid anchor, as judged by its ability to incorporate into guinea-pig erythrocytes and inhibit their lysis by human complement. These results indicate that functionally active protectin becomes enriched in MFG and imply that secretion of glycophospholipid-anchored molecules, e.g. into cow milk and colostrum, could be exploited as a means of producing bioactive molecules that need to be targeted into cell membranes. PMID:7558140

  19. Force-induced globule-coil transition in laminin binding protein and its role for viral-cell membrane fusion.

    PubMed

    Zaitsev, Boris N; Benedetti, Fabrizio; Mikhaylov, Andrey G; Korneev, Denis V; Sekatskii, Sergey K; Karakouz, Tanya; Belavin, Pavel A; Netesova, Nina A; Protopopova, Elena V; Konovalova, Svetlana N; Dietler, Giovanni; Loktev, Valery B

    2014-12-01

    The specific interactions of the pairs laminin binding protein (LBP)-purified tick-borne encephalitis viral surface protein E and certain recombinant fragments of this protein, as well as West Nile viral surface protein E and certain recombinant fragments of that protein, are studied by combined methods of single-molecule dynamic force spectroscopy (SMDFS), enzyme immunoassay and optical surface waves-based biosensor measurements. The experiments were performed at neutral pH (7.4) and acid pH (5.3) conditions. The data obtained confirm the role of LBP as a cell receptor for two typical viral species of the Flavivirus genus. A comparison of these data with similar data obtained for another cell receptor of this family, namely human αVβ3 integrin, reveals that both these receptors are very important. Studying the specific interaction between the cell receptors in question and specially prepared monoclonal antibodies against them, we could show that both interaction sites involved in the process of virus-cell interaction remain intact at pH 5.3. At the same time, for these acid conditions characteristic for an endosome during flavivirus-cell membrane fusion, SMDFS data reveal the existence of a force-induced (effective already for forces as small as 30-70 pN) sharp globule-coil transition for LBP and LBP-fragments of protein E complexes. We argue that this conformational transformation, being an analog of abrupt first-order phase transition and having similarity with the famous Rayleigh hydrodynamic instability, might be indispensable for the flavivirus-cell membrane fusion process. PMID:25319621

  20. Site-specific hydration dynamics in the nonpolar core of a molten globule by dynamic nuclear polarization of water.

    PubMed

    Armstrong, Brandon D; Choi, Jennifer; López, Carlos; Wesener, Darryl A; Hubbell, Wayne; Cavagnero, Silvia; Han, Songi

    2011-04-20

    Water-protein interactions play a direct role in protein folding. The chain collapse that accompanies protein folding involves extrusion of water from the nonpolar core. For many proteins, including apomyoglobin (apoMb), hydrophobic interactions drive an initial collapse to an intermediate state before folding to the final structure. However, the debate continues as to whether the core of the collapsed intermediate state is hydrated and, if so, what the dynamic nature of this water is. A key challenge is that protein hydration dynamics is significantly heterogeneous, yet suitable experimental techniques for measuring hydration dynamics with site-specificity are lacking. Here, we introduce Overhauser dynamic nuclear polarization at 0.35 T via site-specific nitroxide spin labels as a unique tool to probe internal and surface protein hydration dynamics with site-specific resolution in the molten globular, native, and unfolded protein states. The (1)H NMR signal enhancement of water carries information about the local dynamics of the solvent within ∼10 Å of a spin label. EPR is used synergistically to gain insights on local polarity and mobility of the spin-labeled protein. Several buried and solvent-exposed sites of apoMb are examined, each bearing a covalently bound nitroxide spin label. We find that the nonpoloar core of the apoMb molten globule is hydrated with water bearing significant translational dynamics, only 4-6-fold slower than that of bulk water. The hydration dynamics of the native state is heterogeneous, while the acid-unfolded state bears fast-diffusing hydration water. This study provides a high-resolution glimpse at the folding-dependent nature of protein hydration dynamics. PMID:21443207

  1. What we have learned about Mars from SNC meteorites

    NASA Technical Reports Server (NTRS)

    Mcsween, Harry Y., Jr.

    1994-01-01

    lithosphere, but it is in isotopic equilibrium with the atmosphere and has been since 1.3 Ga. The isotopically heavy atmosphere/hydrosphere composition deduced from these rocks reflects a loss process more severe than current atmospheric evolution models, and the occurence of carbonates in SNC meteorites suggest that they, rather than scapolite or hydrous carbonates, are the major crustal sink for CO2. Weathering products in SNC meteorites support the idea of limited alteration of the lithosphere by small volumes of saline, CO2-bearing water. Atmospheric composition and evolution are further constrained by noble gases in these meteorites, although Xe and Kr isotopes suggest different origins for the atmosphere. Planetary ejection of these rocks has promoted an advance in the understanding of impact physics, which has been accomplished by a model involving spallation during large cratering events. Ejection of all the SNC meteorites (except ALH84001) in one or two events may provide a plausible solution to most constraints imposed by chronology, geochemistry, and cosmic ray exposure, although problems remain with this scenario; ALH84001 may represent older martian crust sampled during a separate impact.

  2. Magnetotactic Bacteria on Earth and on Mars

    NASA Astrophysics Data System (ADS)

    McKay, Christopher P.; Friedmann, E. Imre; Frankel, Richard B.; Bazylinski, Dennis A.

    2003-06-01

    Continued interest in the possibility of evidence for life in the ALH84001 Martian meteorite has focused on the magnetite crystals. This review is structured around three related questions: Is the magnetite in ALH84001 of biological or non-biological origin, or a mixture of both? Does magnetite on Earth provide insight to the plausibility of biogenic magnetite on Mars? Could magnetotaxis have developed on Mars? There are credible arguments for both the biological and non-biological origin of the magnetite in ALH84001, and we suggest that more studies of ALH84001, extensive laboratory simulations of non-biological magnetite formation, as well as further studies of magnetotactic bacteria on Earth will be required to further address this question. Magnetite grains produced by bacteria could provide one of the few inorganic traces of past bacterial life on Mars that could be recovered from surface soils and sediments. If there was biogenic magnetite on Mars in sufficient abundance to leave fossil remains in the volcanic rocks of ALH84001, then it is likely that better-preserved magnetite will be found in sedimentary deposits on Mars. Deposits in ancient lakebeds could contain well-preserved chains of magnetite clearly indicating a biogenic origin.

  3. Magnetotactic bacteria on Earth and on Mars.

    PubMed

    McKay, Christopher P; Friedmann, E Imre; Frankel, Richard B; Bazylinski, Dennis A

    2003-01-01

    Continued interest in the possibility of evidence for life in the ALH84001 Martian meteorite has focused on the magnetite crystals. This review is structured around three related questions: is the magnetite in ALH84001 of biological or non-biological origin, or a mixture of both? does magnetite on Earth provide insight to the plausibility of biogenic magnetite on Mars? could magnetotaxis have developed on Mars? There are credible arguments for both the biological and non-biological origin of the magnetite in ALH84001, and we suggest that more studies of ALH84001, extensive laboratory simulations of non-biological magnetite formation, as well as further studies of magnetotactic bacteria on Earth will be required to further address this question. Magnetite grains produced by bacteria could provide one of the few inorganic traces of past bacterial life on Mars that could be recovered from surface soils and sediments. If there was biogenic magnetite on Mars in sufficient abundance to leave fossil remains in the volcanic rocks of ALH84001, then it is likely that better-preserved magnetite will be found in sedimentary deposits on Mars. Deposits in ancient lakebeds could contain well-preserved chains of magnetite clearly indicating a biogenic origin. PMID:14577877

  4. Mineralization of Bacteria in Terrestrial Basaltic Rocks: Comparison With Possible Biogenic Features in Martian Meteorite Allan Hills 84001

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; McKay, D. S.; Wentworth, S. J.; Stevens, T. O.; Taunton, A. E.; Allen, C. C.; Gibson, E. K., Jr.; Romanek, C. S.

    1998-01-01

    The identification of biogenic features altered by diagenesis or mineralization is important in determining whether specific features in terrestrial rocks and in meteorites may have a biogenic origin. Unfortunately, few studies have addressed the formation of biogenic features in igneous rocks, which may be important to these phenomena, including the controversy over possible biogenic features in basaltic martian meteorite ALH84001. To explore the presence of biogenic features in igneous rocks, we examined microcosms growing in basaltic small-scale experimental growth chambers or microcosms. Microbial communities were harvested from aquifers of the Columbia River Basalt (CRB) group and grown in a microcosm containing unweathered basalt chips and groundwater (technique described in. These microcosms simulated natural growth conditions in the deep subsurface of the CRB, which should be a good terrestrial analog for any putative martian subsurface ecosystem that may have once included ALH84001. Here we present new size measurements and photomicrographs comparing the putative martian fossils to biogenic material in the CRB microcosms. The range of size and shapes of the biogenic features on the CRB microcosm chips overlaps with and is similar to those on ALH84001 chips. Although this present work does not provide evidence for the biogenicity of ALH84001 features, we believe that, based on criteria of size, shape, and general morphology, a biogenic interpretation for the ALH84001 features remains plausible.

  5. Magnetotactic bacteria on Earth and on Mars

    NASA Technical Reports Server (NTRS)

    McKay, Christopher P.; Friedmann, E. Imre; Frankel, Richard B.; Bazylinski, Dennis A.

    2003-01-01

    Continued interest in the possibility of evidence for life in the ALH84001 Martian meteorite has focused on the magnetite crystals. This review is structured around three related questions: is the magnetite in ALH84001 of biological or non-biological origin, or a mixture of both? does magnetite on Earth provide insight to the plausibility of biogenic magnetite on Mars? could magnetotaxis have developed on Mars? There are credible arguments for both the biological and non-biological origin of the magnetite in ALH84001, and we suggest that more studies of ALH84001, extensive laboratory simulations of non-biological magnetite formation, as well as further studies of magnetotactic bacteria on Earth will be required to further address this question. Magnetite grains produced by bacteria could provide one of the few inorganic traces of past bacterial life on Mars that could be recovered from surface soils and sediments. If there was biogenic magnetite on Mars in sufficient abundance to leave fossil remains in the volcanic rocks of ALH84001, then it is likely that better-preserved magnetite will be found in sedimentary deposits on Mars. Deposits in ancient lakebeds could contain well-preserved chains of magnetite clearly indicating a biogenic origin.

  6. Cholesterol strongly affects the organization of lipid monolayers studied as models of the milk fat globule membrane: Condensing effect and change in the lipid domain morphology.

    PubMed

    Murthy, Appala Venkata Ramana; Guyomarc'h, Fanny; Paboeuf, Gilles; Vié, Véronique; Lopez, Christelle

    2015-10-01

    The biological membrane that surrounds the milk fat globules exhibits phase separation of polar lipids that is poorly known. The objective of this study was to investigate the role played by cholesterol in the organization of monolayers prepared as models of the milk fat globule membrane (MFGM). Differential scanning calorimetry and X-ray diffraction experiments allowed characterization of the gel to liquid crystalline phase transition temperature of lipids, Tm ~35°C, in vesicles prepared with a MFGM lipid extract. For temperature below Tm, atomic force microscopy revealed phase separation of lipids at 30 mN·m(-1) in Langmuir-Blodgett monolayers of the MFGM lipid extract. The high Tm lipids form liquid condensed (LC) domains that protrude by about 1.5 nm from the continuous liquid expanded (LE) phase. Cholesterol was added to the MFGM extract up to 30% of polar lipids (cholesterol/milk sphingomyelin (MSM) molar ratio of 50/50). Compression isotherms evidenced the condensing effect of the cholesterol onto the MFGM lipid monolayers. Topography of the monolayers showed a decrease in the area of the LC domains and in the height difference H between the LC domains and the continuous LE phase, as the cholesterol content increased in the MFGM lipid monolayers. These results were interpreted in terms of nucleation effects of cholesterol and decrease of the line tension between LC domains and LE phase in the MFGM lipid monolayers. This study revealed the major structural role of cholesterol in the MFGM that could be involved in biological functions of this interface (e.g. mechanisms of milk fat globule digestion). PMID:26087463

  7. Microstructure and properties of pure iron/copper composite cladding layers on carbon steel

    NASA Astrophysics Data System (ADS)

    Wan, Long; Huang, Yong-xian; Lü, Shi-xiong; Huang, Ti-fang; Lü, Zong-liang

    2016-08-01

    In the present study, pure iron/copper composite metal cladding was deposited onto carbon steel by tungsten inert gas welding. The study focused on interfacial morphological, microstructural, and mechanical analyses of the composite cladding layers. Iron liquid-solid-phase zones were formed at copper/steel and iron interfaces because of the melting of the steel substrate and iron. Iron concentrated in the copper cladding layer was observed to exhibit belt, globule, and dendrite morphologies. The appearance of iron-rich globules indicated the occurrence of liquid phase separation (LPS) prior to solidification, and iron-rich dendrites crystallized without the occurrence of LPS. The maximum microhardness of the iron/steel interface was lower than that of the copper/steel interface because of the diffusion of elemental carbon. All samples fractured in the cladding layers. Because of a relatively lower strength of the copper layer, a short plateau region appeared when shear movement was from copper to iron.

  8. LABORATORY INVESTIGATIONS IN SUPPORT OF CARBON DIOXIDE-LIMESTONE SEQUESTRATION IN THE OCEAN

    SciTech Connect

    Dan Golomb; Eugene Barry; David Ryan; Carl Lawton; Peter Swett; John Hannon; Huishan Duan

    2004-09-01

    In the second half of the second contractual year the construction of the High Pressure Flow Reactor (HPFR) was completed, tested, and satisfactory results have been obtained. The major component of the HPFR is a Kenics-type static mixer in which two fluids are thoroughly mixed. In our case the two fluids are liquid or supercritical CO{sub 2} and a slurry of pulverized limestone (CaCO{sub 3}) in pure or artificial seawater. The outflow from the static mixer is an emulsion consisting of CO{sub 2} droplets coated with a sheath of CaCO{sub 3} particles dispersed in water. The coated CO{sub 2} droplets are called globules, and the emulsion is called globulsion. By adjusting the proportions of the two fluids, carbon dioxide and water, the length and pressure drop across the static mixer, globules with a fairly uniform distribution of diameters can be obtained. By using different particle sizes of CaCO{sub 3}, globules can be obtained that are lighter or heavier than water, thus floating or sinking in a water column. The globulsion ensuing from the static mixer flows into a high pressure cell with windows, where the properties of the globules can be observed, such as their diameter and settling velocity. Using the Stokes' equation, the specific gravity of the globules can be determined. Also, a second generation High Pressure Batch Reactor (HPBR) was constructed. This reactor allows better mixing of the ingredients, more accurate temperature and pressure control, better illumination and video camera observations. In this reactor we established that CO{sub 2}-in-water globulsions can be formed stabilized by other particles than pulverized limestone. So far, we used flyash obtained from a local coal-fired power plant, and a pulverized magnesium silicate mineral, lizardite, Mg{sub 3}Si{sub 2}O{sub 5}(OH){sub 4}, obtained from DOE's Albany Research Laboratory. In the reporting period we conducted joint experiments in NETL's high pressure water tunnel facility. Thanks to the

  9. Hydrophobic photolabeling as a new method for structural characterization of molten globule and related protein folding intermediates.

    PubMed Central

    D'Silva, P. R.; Lala, A. K.

    1999-01-01

    Recent advances in attempts to unravel the protein folding mechanism have indicated the need to identify the folding intermediates. Despite their transient nature, in a number of cases it has been possible to detect and characterize some of the equilibrium intermediates, for example, the molten globule (MG) state. The key features of the MG state are retention of substantial secondary structure of the native state, considerable loss of tertiary structure leading to increased hydrophobic exposure, and a compact structure. NMR, circular dichroism, and fluorescence spectroscopies have been most useful in characterizing such intermediates. We report here a new method for structural characterization of the MG state that involves probing the exposed hydrophobic sites with a hydrophobic photoactivable reagent--2[3H]diazofluorene. This carbene-based reagent binds to hydrophobic sites, and on photolysis covalently attaches itself to the neighboring amino acid side chains. The reagent photolabels alpha-lactalbumin as a function of pH (3-7.4), the labeling at neutral pH being negligible and maximal at pH 3. Chemical and proteolytic fragmentation of the photolabeled protein followed by peptide sequencing permitted identification of the labeled residues. The results obtained indicate that the sequence corresponding to B (23-34) and C (86-98) helix of the native structure are extensively labeled. The small beta-domain (40-50) is poorly labeled, Val42 being the only residue that is significantly labeled. Our data, like NMR data, indicate that in the MG state of alpha-lactalbumin, the alpha-domain has a greater degree of persistent structure than the beta-domain. However, unlike the NMR method, the photolabeling method is not limited by the size of the protein and can provide information on several new residues, for example, Leu115. The current method using DAF thus allows identification of stable and hydrophobic exposed regions in folding intermediates as the reagent binds and on

  10. Heterogeneity of equilibrium molten globule state of cytochrome c induced by weak salt denaturants under physiological condition.

    PubMed

    Rahaman, Hamidur; Alam Khan, Md Khurshid; Hassan, Md Imtaiyaz; Islam, Asimul; Moosavi-Movahedi, Ali Akbar; Ahmad, Faizan

    2015-01-01

    While many proteins are recognized to undergo folding via intermediate(s), the heterogeneity of equilibrium folding intermediate(s) along the folding pathway is less understood. In our present study, FTIR spectroscopy, far- and near-UV circular dichroism (CD), ANS and tryptophan fluorescence, near IR absorbance spectroscopy and dynamic light scattering (DLS) were used to study the structural and thermodynamic characteristics of the native (N), denatured (D) and intermediate state (X) of goat cytochorme c (cyt-c) induced by weak salt denaturants (LiBr, LiCl and LiClO4) at pH 6.0 and 25°C. The LiBr-induced denaturation of cyt-c measured by Soret absorption (Δε400) and CD ([θ]409), is a three-step process, N ↔ X ↔ D. It is observed that the X state obtained along the denaturation pathway of cyt-c possesses common structural and thermodynamic characteristics of the molten globule (MG) state. The MG state of cyt-c induced by LiBr is compared for its structural and thermodynamic parameters with those found in other solvent conditions such as LiCl, LiClO4 and acidic pH. Our observations suggest: (1) that the LiBr-induced MG state of cyt-c retains the native Met80-Fe(III) axial bond and Trp59-propionate interactions; (2) that LiBr-induced MG state of cyt-c is more compact retaining the hydrophobic interactions in comparison to the MG states induced by LiCl, LiClO4 and 0.5 M NaCl at pH 2.0; and (3) that there exists heterogeneity of equilibrium intermediates along the unfolding pathway of cyt-c as highly ordered (X1), classical (X2) and disordered (X3), i.e., D ↔ X3 ↔ X2 ↔ X1 ↔ N. PMID:25849212

  11. Characterization of pre-molten globule state of yeast iso-1-cytochrome c and its deletants at pH 6.0 and 25 °C.

    PubMed

    Haque, Md Anzarul; Ubaid-Ullah, Shah; Zaidi, Sobia; Hassan, Md Imtaiyaz; Islam, Asimul; Batra, Janendra K; Ahmad, Faizan

    2015-01-01

    To understand the role of five extra N-terminal residues, we prepared wild type (WT) yeast iso-1-cytochrome c (y-cyt-c) and its deletants by subsequently deleting these residues. Denaturation of all these proteins induced by LiCl was followed by observing changes in molar absorption coefficient at 405 nm (Δɛ405), the mean residue ellipticity at 222 nm ([θ]222), and the difference mean residue ellipticity at 409 nm (Δ[θ]409) near physiological pH and temperature (pH 6.0 and 25 °C). It was observed that in each case LiCl induces biphasic transition, N (native) state ↔ X (intermediate) state ↔ D (denatured) state. The intermediate (X) was characterized by the far-UV, near-UV and Soret circular dichroism, ANS (8-anilino-1-naphthalenesulfonic acid) binding and dynamic light scattering measurements. These measurements led us to conclude that X state of each protein has structural characteristics of PMG (pre-molten globule) state. Thermodynamic stability of all proteins was also determined. It was observed that the N-terminal extension stabilizes the native WT protein but it has no effect on the stability of PMG state. Another state was observed for each protein, in the presence of 0.33 M Na2SO4 at pH 2.1, which when characterized showed all structural characteristics of MG (molten globule) state. PMID:25450045

  12. Functional Role of Milk Fat Globule-Epidermal Growth Factor VIII in Macrophage-Mediated Inflammatory Responses and Inflammatory/Autoimmune Diseases

    PubMed Central

    2016-01-01

    Inflammation involves a series of complex biological processes mediated by innate immunity for host defense against pathogen infection. Chronic inflammation is considered to be one of the major causes of serious diseases, including a number of autoimmune/inflammatory diseases, cancers, cardiovascular diseases, and neurological diseases. Milk fat globule-epidermal growth factor 8 (MFG-E8) is a secreted protein found in vertebrates and was initially discovered as a critical component of the milk fat globule. Previously, a number of studies have reported that MFG-E8 contributes to various biological functions including the phagocytic removal of damaged and apoptotic cells from tissues, the induction of VEGF-mediated neovascularization, the maintenance of intestinal epithelial homeostasis, and the promotion of mucosal healing. Recently, emerging studies have reported that MFG-E8 plays a role in inflammatory responses and inflammatory/autoimmune diseases. This review describes the characteristics of MFG-E8-mediated signaling pathways, summarizes recent findings supporting the roles of MFG-E8 in inflammatory responses and inflammatory/autoimmune diseases, and discusses MFG-E8 targeting as a potential therapeutic strategy for the development of anti-inflammatory/autoimmune disease drugs. PMID:27429513

  13. A study of xenon isotopes in a martian meteorite using the RELAX ultrasensitive mass spectrometer

    SciTech Connect

    Whitby, J A; Gilmour, J D; Turner, G

    1997-01-15

    The Refrigerator Enhanced Analyser for Xenon (RELAX), an ultrasensitive resonance ionization time-of-flight mass spectrometer, has been used with a laser microprobe to investigate the isotopic composition of xenon trapped in the martian meteorite ALH84001. The laser microprobe has a spatial resolution of the order of 100{mu}m thus allowing the in situ analysis of individual mineral grains in a polished section when combined with ultrasensitive, low blank sample analysis. We present results showing that the mineral orthopyroxene in ALH84001 contains a trapped xenon component consistent with a martian origin. Additionally, a cosmic ray exposure age of 15Ma for ALH84001 is obtained from spallation derived xenon trapped within an apatite grain.

  14. Amino Acids in the Antarctic Martian Meteorite MIL03346

    NASA Technical Reports Server (NTRS)

    Glavin, D. P.; Aubrey, A.; Dworkin, J. P.; Botta, O.; Bada, J. L.

    2005-01-01

    The report by McKay et al. that the Martian meteorite ALH84001 contains evidence for life on Mars remains controversial. Of central importance is whether ALH84001 and other Antarctic Martian meteorites contain endogenous organic compounds. In any investigation of organic compounds possibly derived from Mars it is important to focus on compounds that play an essential role in biochemistry as we know it and that have properties such as chirality which can be used to distinguish between biotic versus abiotic origins. Amino acids are one of the few compounds that fulfill these requirements. Previous analyses of the Antarctic Martian meteorites ALH84001 and EETA79001 have shown that these meteorites contain low levels of terrestrial amino acid contamination derived from Antarctic ice meltwater. Here we report preliminary amino acid investigations of a third Antarctic Martian meteorite MIL03346 which was discovered in Antarctica during the 2003-04 ANSMET season. Additional information is included in the original extended abstract

  15. Extinct Life on Mars: Looking for Traces of Viruses Instead of Bacteria

    NASA Astrophysics Data System (ADS)

    Ksanfomality, Leonid

    The finds in the ALH 84001 meteorite were reported as a sign of traces and fossils of ancient Martian primitive life. Despite many experiments, the issue has not been settled. A study of geochemical data suggests that simple inorganic processes sometimes offer a more plausible explanation of the suspicious structures found in the ALH 84001 meteorite that had been discussed by many authors. A photo of certain micro structures got in the paper of N. Yushkin (Fig. 1) proves the point. (Figure: The inorganic structures in granites.) It is known that viruses possess an ability to survive under very severe external conditions. The Martian biogenic activity (if any) could leave its virus' sign. Thus it could make a sense to look for viruses or even DNA traces both in the body of the ALH 84001 meteorite and on Mars in future space missions instead of traces of the extinct bacteria.

  16. Independent of Their Localization in Protein the Hydrophobic Amino Acid Residues Have No Effect on the Molten Globule State of Apomyoglobin and the Disulfide Bond on the Surface of Apomyoglobin Stabilizes This Intermediate State

    PubMed Central

    Melnik, Tatiana N.; Majorina, Maria A.; Larina, Daria S.; Kashparov, Ivan A.; Samatova, Ekaterina N.; Glukhov, Anatoly S.; Melnik, Bogdan S.

    2014-01-01

    At present it is unclear which interactions in proteins reveal the presence of intermediate states, their stability and formation rate. In this study, we have investigated the effect of substitutions of hydrophobic amino acid residues in the hydrophobic core of protein and on its surface on a molten globule type intermediate state of apomyoglobin. It has been found that independent of their localization in protein, substitutions of hydrophobic amino acid residues do not affect the stability of the molten globule state of apomyoglobin. It has been shown also that introduction of a disulfide bond on the protein surface can stabilize the molten globule state. However in the case of apomyoglobin, stabilization of the intermediate state leads to relative destabilization of the native state of apomyoglobin. The result obtained allows us not only to conclude which mutations can have an effect on the intermediate state of the molten globule type, but also explains why the introduction of a disulfide bond (which seems to “strengthen” the protein) can result in destabilization of the protein native state of apomyoglobin. PMID:24892675

  17. Independent of their localization in protein the hydrophobic amino acid residues have no effect on the molten globule state of apomyoglobin and the disulfide bond on the surface of apomyoglobin stabilizes this intermediate state.

    PubMed

    Melnik, Tatiana N; Majorina, Maria A; Larina, Daria S; Kashparov, Ivan A; Samatova, Ekaterina N; Glukhov, Anatoly S; Melnik, Bogdan S

    2014-01-01

    At present it is unclear which interactions in proteins reveal the presence of intermediate states, their stability and formation rate. In this study, we have investigated the effect of substitutions of hydrophobic amino acid residues in the hydrophobic core of protein and on its surface on a molten globule type intermediate state of apomyoglobin. It has been found that independent of their localization in protein, substitutions of hydrophobic amino acid residues do not affect the stability of the molten globule state of apomyoglobin. It has been shown also that introduction of a disulfide bond on the protein surface can stabilize the molten globule state. However in the case of apomyoglobin, stabilization of the intermediate state leads to relative destabilization of the native state of apomyoglobin. The result obtained allows us not only to conclude which mutations can have an effect on the intermediate state of the molten globule type, but also explains why the introduction of a disulfide bond (which seems to "strengthen" the protein) can result in destabilization of the protein native state of apomyoglobin. PMID:24892675

  18. Molten globule of bovine alpha-lactalbumin at neutral pH induced by heat, trifluoroethanol, and oleic acid: a comparative analysis by circular dichroism spectroscopy and limited proteolysis.

    PubMed

    Polverino de Laureto, Patrizia; Frare, Erica; Gottardo, Rossella; Fontana, Angelo

    2002-11-15

    The calcium-depleted form of alpha-lactalbumin (alpha-LA) at neutral pH can be induced to adopt a partly folded state or molten globule upon moderate heating, by dissolving the protein in aqueous TFE or by adding oleic acid. This last folding variant of the protein, named HAMLET, can induce apoptosis in tumor cells. The aim of the present work was to unravel from circular dichroism (CD) measurements and proteolysis experiments structural features of the molten globule of apo-alpha-LA at neutral pH. CD spectra revealed that the molten globule of apo-alpha-LA can be obtained upon mild heating at 45 degrees C, as well as at room temperature in the presence of 15% TFE or by adding to the protein solution 7.5 equivalents of oleic acid. Under these various conditions the far- and near-UV CD spectra of apo-alpha-LA are essentially identical to those of the most studied molten globule of alpha-LA at pH 2.0 (A-state). Proteolysis of the 123-residue chain of apo-alpha-LA by proteinase K at 4 degrees C occurs slowly as an all-or-none process leading to small peptides only. At 37 degrees C, proteinase K preferentially cleaves apo-alpha-LA at peptide bonds Ser34-Gly35, Gln39-Ala40, Gln43-Asn44, Phe53-Gln54, and Asn56-Asn57. All these peptide bonds are located at level of the beta-subdomain of the protein (chain region 34-57). Similar sites of preferential cleavage have been observed with the TFE- and oleic acid-induced molten globule of apo-alpha-LA. A protein species given by the N-terminal fragment 1-34 linked via the four disulfide bridges to the C-terminal fragment 54-123 or 57-123 can be isolated from the proteolytic mixture. The results of this study indicate that the same molten globule state of apo-alpha-LA can be obtained at neutral pH under mildly denaturing conditions, as indicated by using a classical spectroscopic technique such as CD and a simple biochemical approach as limited proteolysis. We conclude that the molten globule of alpha-LA maintains a native

  19. Ferromagnetic resonance and low-temperature magnetic tests for biogenic magnetite

    NASA Astrophysics Data System (ADS)

    Weiss, Benjamin P.; Sam Kim, Soon; Kirschvink, Joseph L.; Kopp, Robert E.; Sankaran, Mohan; Kobayashi, Atsuko; Komeili, Arash

    2004-07-01

    Magnetite is both a common inorganic rock-forming mineral and a biogenic product formed by a diversity of organisms. Magnetotactic bacteria produce intracellular magnetites of high purity and crystallinity (magnetosomes) arranged in linear chains of crystals. Magnetosomes and their fossils (magnetofossils) have been identified using transmission electron microscopy (TEM) in sediments dating back to ˜510-570 Ma, and possibly in 4 Ga carbonates in Martian meteorite ALH84001. We present the results from two rock magnetic analyses—the low-temperature Moskowitz test and ferromagnetic resonance (FMR)—applied to dozens of samples of magnetite and other materials. The magnetites in these samples are of diverse composition, size, shape, and origin: biologically induced (extracellular), biologically controlled (magnetosomes and chiton teeth), magnetofossil, synthetic, and natural inorganic. We confirm that the Moskowitz test is a distinctive indicator for magnetotactic bacteria and provide the first direct experimental evidence that this is accomplished via sensitivity to the magnetosome chain structure. We also demonstrate that the FMR spectra of four different strains of magnetotactic bacteria and a magnetofossil-bearing carbonate have a form distinct from all other samples measured in this study. We suggest that this signature also results from the magnetosomes' unique arrangement in chains. Because FMR can rapidly identify samples with large fractions of intact, isolated magnetosome chains, it could be a powerful tool for identifying magnetofossils in sediments.

  20. Evidence for Microfossils in Ancient Rocks and Meteorites

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.; Rozanov, A. Y.; Zhmur, S. I.; Gorlenko, V. M.

    1998-01-01

    The McKay et all. detection of chemical biomarkers and possible microfossils in an ancient meteorite from Mars (ALH84001) stimulated research in several areas of importance to the newly emerging field of Astrobiology. Their report resulted in a search for additional evidence of microfossils in ancient terrestrial rocks and meteorites. These studies of ancient rocks and meteorites were conducted independently (and later collaboratively) in the United States and Russia using the SEM, Environmental Scanning Electron Microscope (ESEM), and Field Emission Scanning Electron Microscope (FESEM). We have encountered in-situ in freshly broken carbonaceous chondrites a large number of complex microstructures that appear to be lithified microbial forms. The meteoritic microstructures have characteristics similar to the lithified remains of filamentous cyanobacteria and bacterial microfossils we have found in ancient phosphorites, ancient graphites and oil shales. Energy Dispersive Spectroscopy (EDS) and Link microprobe analysis shows the possible microfossils have a distribution of chemical elements characteristic of the meteorite rock matrix, although many exhibit a superimposed carbon enhancement. We have concluded that the mineralized bodies encountered embedded in the rock matrix of freshly fractured meteoritic surfaces can not be dismissed as recent surface contaminants. Many of the forms found in-situ in the Murchison, Efremovka, and Orgueil carbonaceous meteorites are strikingly similar to microfossils of coccoid bacteria, cyanobacteria and fungi such as we have found in the Cambrian phosphorites of Khubsugul, Mongolia and high carbon Phanerozoic and Precambrian rocks of the Siberian and Russian Platforms.

  1. Safety evaluation of the consumption of high dose milk fat globule membrane in healthy adults: a double-blind, randomized controlled trial with parallel group design.

    PubMed

    Hari, Sayaka; Ochiai, Ryuji; Shioya, Yasushi; Katsuragi, Yoshihisa

    2015-01-01

    Consumption of milk fat globule membrane (MFGM) in combination with habitual exercise suppresses age-associated muscle loss. The effects of high dose MFGM, however, are not known. A double-blind, randomized controlled trial with parallel group design was conducted to evaluate the safety of consuming high dose MFGM tablets. The subjects were 32 healthy adult men and women. Subjects were given 5 times the recommended daily intake of the tablets containing 6.5 g of MFGM or whole milk powder for 4 weeks. Stomach discomfort and diarrhea were observed; however, these symptoms were transitory and slight and were not related to consumption of the test tablets. In addition, there were no clinically significant changes in anthropometric measurements or blood tests. Total degree of safety assessed by the physicians of all subjects was "safe." These findings suggest that consumption of the tablets containing 6.5 g MFGM for 4 weeks is safe for healthy adults. PMID:25704503

  2. Evidence for Past Life on Early Mars: How the Evidence Stands

    NASA Astrophysics Data System (ADS)

    Gibson, Everett K.; Thomas-Keprta, Kathie L.; Clemett, Simon J.; McKay, David S.; Romanek, Christopher; Wentworth, Susan J.

    2004-06-01

    Martian Meteorite ALH84001 contains four unusual features which have been interpreted as possible signatures of relic biogenic activity. After six years of intense study by the world's scientific community, the current status of the biogenic hypothesis is reviewed and shown to still be valid. Furthermore additional features have been observed in two younger Martian meteorites. The strongest argument for possible evidence of biogenic activity within the ALH84001 meteorite is the presence of truncated hexa-octahedral magnetite crystals which are only known on Earth to be the products of biology.

  3. Hydrolysis of bovine and caprine milk fat globules by lipoprotein lipase. Effects of heparin and skim milk on lipase distribution and on lipolysis

    SciTech Connect

    Sundheim, G.; Bengtsson-Olivecrona, G.

    1987-12-01

    Heparin can dissociate lipoprotein lipase from casein micelles, and addition of heparin enhances lipolysis in bovine but not in caprine milk. Heparin shortened the lag-time for binding of lipoprotein lipase to milk fat globules and for lipolysis. Heparin counteracted the inhibitory effects of skim milk on binding of lipase and on lipolysis. Heparin stimulated lipolysis in all bovine milk samples when added before cooling and in spontaneously lipolytic milk samples also when added after cooling. Heparin enhanced lipolysis of isolated milk fat globules. Hence, its effect is not solely due to dissociation of lipoprotein lipase from the casein micelles. Cooling of goat milk caused more marked changes in the distribution of lipase than cooling of bovine milk; the fraction of added /sup 125/I-labeled lipase that bound to cream increased from about 8 to 60%. In addition, caprine skim milk caused less inhibition of lipolysis than bovine skim milk. These observations provide an explanation for the high degree of cold storage lipolysis in goat milk. Heparin had only small effects on the distribution of lipoprotein lipase in caprine milk, which explains why heparin has so little effect on lipolysis in caprine milk. The distribution of /sup 35/S-labeled heparin in bovine milk was studied. In warm milk less than 10% bound to the cream fraction, but when milk was cooled, binding of heparin to cream increased to 45%. These results suggest that there exists in the skim fraction a relatively small amount of a heparin-binding protein, which on cooling of milk adsorbs to the milk fat, or suggests that cooling induces a conformational change in a membrane protein such that its affinity for heparin increases.

  4. Cholesterol Decreases the Size and the Mechanical Resistance to Rupture of Sphingomyelin Rich Domains, in Lipid Bilayers Studied as a Model of the Milk Fat Globule Membrane.

    PubMed

    Murthy, Appala Venkata Ramana; Guyomarc'h, Fanny; Lopez, Christelle

    2016-07-01

    Sphingomyelin-rich microdomains have been observed in the biological membrane surrounding milk fat globules (MFGM). The role played by cholesterol in these domains and in the physical properties and functions of the MFGM remains poorly understood. The objective of this work was therefore to investigate the phase state, topography, and mechanical properties of MFGM polar lipid bilayers as a function of cholesterol concentration, by combining X-ray diffraction, atomic force microscopy imaging, and force spectroscopy. At room temperature, i.e. below the phase transition temperature of the MFGM polar lipids, the bilayers showed the formation of sphingomyelin-rich domains in the solid ordered (so) phase that protruded about 1 nm above the liquid disordered (ld) phase. These so phase domains have a higher mechanical resistance to rupture than the ld phase (30 nN versus 15 nN). Addition of cholesterol in the MFGM polar lipid bilayers (i) induced the formation of liquid ordered (lo) phase for up to 27 mol % in the bilayers, (ii) decreased the height difference between the thicker ordered domains and the surrounding ld phase, (iii) promoted the formation of small sized domains, and (iv) decreased the mechanical resistance to rupture of the sphingomyelin-rich domains down to ∼5 nN. The biological and functional relevance of the lo phase cholesterol/sphingomyelin-rich domains in the membrane surrounding fat globules in milk remains to be elucidated. This study brought new insight about the functional role of cholesterol in milk polar lipid ingredients, which can be used in the preparation of food emulsions, e.g. infant milk formulas. PMID:27300157

  5. Carbonate inclusions in Lower Cretaceous picrites from the Hončova hůrka Hill (Czech Republic, Outer Western Carpathians): Evidence for primary magmatic carbonates?

    NASA Astrophysics Data System (ADS)

    Kropáč, Kamil; Dolníček, Zdeněk; Buriánek, David; Urubek, Tomáš; Mašek, Vlastimil

    2015-07-01

    Porphyritic picrites from the Hončova hůrka site in the Silesian Unit (Western Carpathians) are composed mostly of olivine phenocrysts enclosed in a black fine-grained groundmass, which consists of clinopyroxene, biotite, magnetite, chlorite, feldspars, and zeolites. The rocks are variably affected by hydrothermal alteration. The freshest samples contain potentially primary igneous calcite and aragonite, which occur as globular inclusions hosted by olivine phenocrysts, or as fillings of the miarolitic cavities in the picrite groundmass. In this paper, we try to clarify the nature of investigated carbonates using the combination of several petrological methods. Based on the texture, mineral composition, and relationship to the alteration patterns of the host mineral, we distinguished three basic types of inclusions: carbonate inclusions, silicate inclusions, and a combined type consisting of both carbonate and silicate domains. Only the fresh olivine-hosted round carbonate globules can contain the primary igneous calcite. These globules cannot represent immiscible carbonatite melt since they lack Si, alkalis, and other essential components (e.g. P, F, Cl, and S) present in natural carbonate melts. Instead, they can be interpreted as product of equilibrium crystallization of calcite from carbonated silicate melt (i.e. crystal cumulates). In contrast, the calcite-aragonite assemblage in inclusions hosted by altered olivine and in miaroles most probably originated during recrystallization of primary calcite during late-magmatic or post-magmatic stages or is related to the superimposed hydrothermal alteration.

  6. Bacteria in the Tatahouine meteorite: nanometric-scale life in rocks.

    PubMed

    Gillet, P h; Barrat, J A; Heulin, T h; Achouak, W; Lesourd, M; Guyot, F; Benzerara, K

    2000-02-15

    We present a study of the textural signature of terrestrial weathering and related biological activity in the Tatahouine meteorite. Scanning and transmission electron microscopy images obtained on the weathered samples of the Tatahouine meteorite and surrounding soil show two types of bacteria-like forms lying on mineral surfaces: (1) rod-shaped forms (RSF) about 70-80 nm wide and ranging from 100 nm to 600 nm in length; (2) ovoid forms (OVF) with diameters between 70 and 300 nm. They look like single cells surrounded by a cell wall. Only Na, K, C, O and N with traces of P and S are observed in the bulk of these objects. The chemical analyses and electron diffraction patterns confirm that the RSF and OVF cannot be magnetite or other iron oxides, iron hydroxides, silicates or carbonates. The sizes of the RSF and OVF are below those commonly observed for bacteria but are very similar to some bacteria-like forms described in the Martian meteorite ALH84001. All the previous observations strongly suggest that they are bacteria or their remnants. This conclusion is further supported by microbiological experiments in which pleomorphic bacteria with morphology similar to the OVF and RSF objects are obtained from biological culture of the soil surrounding the meteorite pieces. The present results show that bacteriomorphs of diameter less than 100 nm may in fact represent real bacteria or their remnants. PMID:11543579

  7. Mars Atmospheric Composition, Isotope Ratios and Seasonal Variations: Overview and Updates of the SAM Measurements at Gale Crater

    NASA Technical Reports Server (NTRS)

    Niles, Paul

    2014-01-01

    We will summarize the in situ measurements of atmospheric composition and the isotopic ratios of D/H in water, C-13/C-12, O-18/O-16, O-17 / O-16, and C-13 O-18 / C-12 O-16 in carbon dioxide, and Ar-38 / Ar-36, Kr-x / Kr-84, and N-15 / N-14 made in the martian atmosphere at Gale Crater from the Curiosity Rover using the Sample Analysis at Mars (SAM)'s Quadrupole Mass Spectrometer (QMS) and Tunable Laser Spectrometer (TLS). With data over 700 sols since the Curiosity landing, we will discuss evidence and implications for changes on seasonal and other timescales. We will also present results for continued methane and methane enrichment experiments over this time period. Comparison between our measurements in the modern atmosphere and those of martian meteorites like ALH 84001 implies that the martian reservoirs of CO2 and H2O were largely established approximately 4 billion years ago, but that atmospheric loss or surface interaction may be still ongoing.

  8. Nanobacteria from blood: the smallest culturable autonomously replicating agent on Earth

    NASA Astrophysics Data System (ADS)

    Kajander, E. Olavi; Kuronen, Ilpo; Akerman, Kari K.; Pelttari, Alpo; Ciftcioglu, Neva

    1997-07-01

    Nanobacteria are the first mineral forming bacteria isolated from blood and blood products. They are coccoid cell-walled organisms with a size of 0.08 - 0.5 micrometers in EM, occure in clusters, produce a biofilm containing carbonate or hydroxyl apatite, and are highly resistant to heat, gamma-irradiation and antibiotics. Their growth rate is about one hundredth that of ordinary bacteria and they divide via several mechanisms. Taq polymerase was able to use their nontraditional nucleic acid as a template. 16S rRNA gene sequence results positioned them into the alpha-2 subgroup of Proteobacteria. Nanobacteria are smallest cell-walled bacteria since they can pass through 0.07 micrometers pores. In low-serum cultures, they form even smaller elementary particles or tubular units. How can blood be infected with such slow growing, heat and radio-resistant bacteria? The answer may lie in their phylogeny: alpha-2 subgroup has organisms from soil exposed to radiation and heat, that can penetrate into eukaryotic cells. Nanobacteria grow so slowly that they require a niche `cleaned' with heat, radiation or immunodefence. For survival they cloak themselves in apatite, a normal constituent of mammalian body. This may link nanobacteria to nannobacteria discovered from sedimentary rocks by Dr. Folk. Both have similar size, size variation, clustering and mineral deposits. They may resemble the probable ancient bacterial fossils in the Martian meteorite ALH84001.

  9. Carbon Dioxide-Water Emulsions for Enhanced Oil Recovery and Permanent Sequestration of Carbon Dioxide

    SciTech Connect

    Ryan, David; Golomb, Dan; Shi, Guang; Shih, Cherry; Lewczuk, Rob; Miksch, Joshua; Manmode, Rahul; Mulagapati, Srihariraju; Malepati, Chetankurmar

    2011-09-30

    This project involves the use of an innovative new invention Particle Stabilized Emulsions (PSEs) of Carbon Dioxide-in-Water and Water-in-Carbon Dioxide for Enhanced Oil Recovery (EOR) and Permanent Sequestration of Carbon Dioxide. The EOR emulsion would be injected into a semi-depleted oil reservoir such as Dover 33 in Otsego County, Michigan. It is expected that the emulsion would dislocate the stranded heavy crude oil from the rock granule surfaces, reduce its viscosity, and increase its mobility. The advancing emulsion front should provide viscosity control which drives the reduced-viscosity oil toward the production wells. The make-up of the emulsion would be subsequently changed so it interacts with the surrounding rock minerals in order to enhance mineralization, thereby providing permanent sequestration of the injected CO{sub 2}. In Phase 1 of the project, the following tasks were accomplished: 1. Perform laboratory scale (mL/min) refinements on existing procedures for producing liquid carbon dioxide-in-water (C/W) and water-in-liquid carbon dioxide (W/C) emulsion stabilized by hydrophilic and hydrophobic fine particles, respectively, using a Kenics-type static mixer. 2. Design and cost evaluate scaled up (gal/min) C/W and W/C emulsification systems to be deployed in Phase 2 at the Otsego County semi-depleted oil field. 3. Design the modifications necessary to the present CO{sub 2} flooding system at Otsego County for emulsion injection. 4. Design monitoring and verification systems to be deployed in Phase 2 for measuring potential leakage of CO{sub 2} after emulsion injection. 5. Design production protocol to assess enhanced oil recovery with emulsion injection compared to present recovery with neat CO{sub 2} flooding. 6. Obtain Federal and State permits for emulsion injection. Initial research focused on creating particle stabilized emulsions with the smallest possible globule size so that the emulsion can penetrate even low-permeability crude

  10. A Critical Examination of Relative Concentrations of Volume-correlated and Surface-correlated Submicron Globules of Pure Fe-0 in Lunar Soils

    NASA Technical Reports Server (NTRS)

    Basu, A.; McKay, D. S.; Wentworth, S. J.

    2003-01-01

    Impacts on lunar soils produce melt and vapor in an approximate proportion of 7:1. The melt scavenges soil grains of diverse size, quenches and forms agglutinates, thereby converting surface correlated components of soil grains as volume correlated components; simultaneously, parts of the vapor may condense or escape. Cumulative small impacts increase the maturity of the soils, increase the abundance of agglutinates, and increase the concentration of vapor condensated material. Since the discovery of vapor deposited crystalline Fe-0 in vugs of regolith breccias and the theoretical anticipation of amorphous vapor deposits of diverse composition coating lunar soils grains, empirical evidence is gathering in support of such deposits, now commonly called vapor deposited patina (VDP). In addition, submicron globules of Fe-0 are seen to be ubiquitous in VDP. The amorphous VDP lowers the albedo of lunar soils, affects magnetic properties of soils, changes the slopes of uv-vis-ir reflectance spectra, and potentially also alters the gamma and x-ray spectra of lunar soils, compromising compositional inferences from remote sensing.

  11. Quantitative proteomic analysis of milk fat globule membrane (MFGM) proteins in human and bovine colostrum and mature milk samples through iTRAQ labeling.

    PubMed

    Yang, Mei; Cong, Min; Peng, Xiuming; Wu, Junrui; Wu, Rina; Liu, Biao; Ye, Wenhui; Yue, Xiqing

    2016-05-18

    Milk fat globule membrane (MFGM) proteins have many functions. To explore the different proteomics of human and bovine MFGM, MFGM proteins were separated from human and bovine colostrum and mature milk, and analyzed by the iTRAQ proteomic approach. A total of 411 proteins were recognized and quantified. Among these, 232 kinds of differentially expressed proteins were identified. These differentially expressed proteins were analyzed based on multivariate analysis, gene ontology (GO) annotation and KEGG pathway. Biological processes involved were response to stimulus, localization, establishment of localization, and the immune system process. Cellular components engaged were the extracellular space, extracellular region parts, cell fractions, and vesicles. Molecular functions touched upon were protein binding, nucleotide binding, and enzyme inhibitor activity. The KEGG pathway analysis showed several pathways, including regulation of the actin cytoskeleton, focal adhesion, neurotrophin signaling pathway, leukocyte transendothelial migration, tight junction, complement and coagulation cascades, vascular endothelial growth factor signaling pathway, and adherens junction. These results enhance our understanding of different proteomes of human and bovine MFGM across different lactation phases, which could provide important information and potential directions for the infant milk powder and functional food industries. PMID:27159491

  12. The Pathogenic Mutation T182A Converts the Prion Protein into a Molten Globule-like Conformation Whose Misfolding to Oligomers but Not to Fibrils Is Drastically Accelerated.

    PubMed

    Singh, Jogender; Udgaonkar, Jayant B

    2016-01-26

    Delineation of the effects of pathogenic mutations linked with familial prion diseases on the structure and misfolding of prion protein (PrP) will be useful in understanding the molecular mechanism of PrP misfolding. Here, it has been shown that the pathogenic mutation T182A causes a drastic reduction in the apparent cooperativity and enthalpy of unfolding of the mouse prion protein (moPrP) under misfolding-prone conditions by converting the protein into a molten globule (MG)-like conformation. Hydrogen-deuterium exchange studies in conjunction with mass spectrometry indicate that the T182A mutation disrupts the core of the protein, thereby increasing overall structural dynamics. T182A moPrP is shown to misfold to oligomers very much faster than does wild-type (wt) moPrP but to misfold to fibrils at a rate similar to that of wt moPrP. This observation suggests that oligomers are unlikely to play a productive role in the direct pathway of aggregation from monomer to fibrils. The observation that fully folded T182A moPrP has a MG-like structure, and that it misfolds to oligomers much faster than does wt moPrP, suggests that a MG-like intermediate, whose structure resembles that of fully folded T182A moPrP, might be populated early on the pathway of misfolding of wt moPrP to oligomers. PMID:26713717

  13. Evidence for Dry Molten Globule-Like Domains in the pH-Induced Equilibrium Folding Intermediate of a Multidomain Protein.

    PubMed

    Acharya, Nirbhik; Mishra, Prajna; Jha, Santosh Kumar

    2016-01-01

    The role of van der Waals (vdW) packing interactions compared to the hydrophobic effect in stabilizing the functional structure of proteins is poorly understood. Here we show, using fluorescence resonance energy transfer, dynamic fluorescence quenching, red-edge excitation shift, and near- and far-UV circular dichroism, that the pH-induced structural perturbation of a multidomain protein leads to the formation of a state in which two out of the three domains have characteristics of dry molten globules, that is, the domains are expanded compared to the native protein with disrupted packing interactions but have dry cores. We quantitatively estimate the energetic contribution of vdW interactions and show that they play an important role in the stability of the native state and cooperativity of its structural transition, in addition to the hydrophobic effect. Our results also indicate that during the pH-induced unfolding, side-chain unlocking and hydrophobic solvation occur in two distinct steps and not in a concerted manner, as commonly believed. PMID:26700266

  14. Molten globule-like partially folded state of Bacillus licheniformis α-amylase at low pH induced by 1,1,1,3,3,3-hexafluoroisopropanol.

    PubMed

    Abd Halim, Adyani Azizah; Zaroog, Mohammed Suleiman; Kadir, Habsah Abdul; Tayyab, Saad

    2014-01-01

    Effect of 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) on acid-denatured Bacillus licheniformis α -amylase (BLA) at pH 2.0 was investigated by far-UV CD, intrinsic fluorescence, and ANS fluorescence measurements. Addition of increasing HFIP concentrations led to an increase in the mean residue ellipticity at 222 nm (MRE 222 nm) up to 1.5 M HFIP concentration beyond which it sloped off. A small increase in the intrinsic fluorescence and a marked increase in the ANS fluorescence were also observed up to 0.4 M HFIP concentration, both of which decreased thereafter. Far- and near-UV CD spectra of the HFIP-induced state observed at 0.4 M HFIP showed significant retention of the secondary structures closer to native BLA but a disordered tertiary structure. Increase in the ANS fluorescence intensity was also observed with the HFIP-induced state, suggesting exposure of the hydrophobic clusters to the solvent. Furthermore, thermal denaturation of HFIP-induced state showed a non-cooperative transition. Taken together, all these results suggested that HFIP-induced state of BLA represented a molten globule-like state at pH 2.0. PMID:24977228

  15. Interaction of insulin with methyl tert-butyl ether promotes molten globule-like state and production of reactive oxygen species.

    PubMed

    Valipour, Masoumeh; Maghami, Parvaneh; Habibi-Rezaei, Mehran; Sadeghpour, Mostafa; Khademian, Mohamad Ali; Mosavi, Khadijeh; Sheibani, Nader; Moosavi-Movahedi, Ali Akbar

    2015-09-01

    Interaction of methyl tert-butyl ether (MTBE) with proteins is a new look at its potential adverse biological effects. When MTBE is released to the environment it enters the blood stream through inhalation, and could affect the properties of various proteins. Here we investigated the interaction of MTBE with insulin and its effect on insulin structural changes. Our results showed that insulin formed a molten globule (MG)-like structure in the presence of 8 μM MTBE under physiological pH. The insulin structural changes were studied using spectroscopy methods, viscosity calculation, dynamic light scattering and differential scanning calorimetry. To delineate the mechanisms involved in MTBE-protein interactions, the formation of reactive oxygen specious (ROS) and formation of protein aggregates were measured. The chemiluminscence experiments revealed an increase in ROS production in the presence of MTBE especially in the MG-like state. These results were further confirmed by the aggregation tests, which indicated more aggregation of insulin at 40 μM MTBE compared with 8 μM. Thus, the formation of initial aggregates and exposure of the hydrophobic patches upon formation of the MG-like state in the presence of MTBE drives protein oxidation and ROS generation. PMID:26193678

  16. Magnetite biomineralization and ancient life on Mars.

    PubMed

    Frankel, R B; Buseck, P R

    2000-04-01

    Certain chemical and mineral features of the Martian meteorite ALH84001 were reported in 1996 to be probable evidence of ancient life on Mars. In spite of new observations and interpretations, the question of ancient life on Mars remains unresolved. Putative biogenic, nanometer magnetite has now become a leading focus in the debate. PMID:10742183

  17. Evaluation of Meterorite Amono Acid Analysis Data Using Multivariate Techniques

    NASA Technical Reports Server (NTRS)

    McDonald, G.; Storrie-Lombardi, M.; Nealson, K.

    1999-01-01

    The amino acid distributions in the Murchison carbonaceous chondrite, Mars meteorite ALH84001, and ice from the Allan Hills region of Antarctica are shown, using a multivariate technique known as Principal Component Analysis (PCA), to be statistically distinct from the average amino acid compostion of 101 terrestrial protein superfamilies.

  18. Fission Xenon on Mars

    NASA Technical Reports Server (NTRS)

    Mathew, K. J.; Marti, K.; Marty, B.

    2002-01-01

    Fission Xe components due to Pu-244 decay in the early history of Mars have been identified in nakhlites; as in the case of ALH84001 and Chassigny the fission gas was assimilated into indigenous solar-type Xe. Additional information is contained in the original extended abstract.

  19. Fossilized microorganisms associated with zeolite-carbonate interfaces in sub-seafloor hydrothermal environments.

    PubMed

    Ivarsson, M; Lindblom, S; Broman, C; Holm, N G

    2008-03-01

    In this paper we describe carbon-rich filamentous structures observed in association with the zeolite mineral phillipsite from sub-seafloor samples drilled and collected during the Ocean Drilling Program (ODP) Leg 197 at the Emperor Seamounts. The filamentous structures are approximately 5 microm thick and approximately 100-200 microm in length. They are found attached to phillipsite surfaces in veins and entombed in vein-filling carbonates. The carbon content of the filaments ranges between approximately 10 wt% C and 55 wt% C. They further bind to propidium iodide (PI), which is a dye that binds to damaged cell membranes and remnants of DNA. Carbon-rich globular microstructures, 1-2 microm in diameter, are also found associated with the phillipsite surfaces as well as within wedge-shaped cavities in phillipsite assemblages. The globules have a carbon content that range between approximately 5 wt% C and 55 wt% C and they bind to PI. Ordinary globular iron oxides found throughout the samples differ in that they contain no carbon and do not bind to the dye PI. The carbon-rich globules are mostly concentrated to a film-like structure that is attached to the phillipsite surfaces. This film has a carbon content that ranges between approximately 25 wt% C and 75 wt% C and partially binds to PI. EDS analyses show that the carbon in all structures described are not associated with calcium and therefore not bound in carbonates. The carbon content and the binding to PI may indicate that the filamentous structures could represent fossilized filamentous microorganisms, the globules could represent fossilized microbial cells and the film-like structures could represent a microbially produced biofilm. Our results extend the knowledge of possible habitable niches for a deep biosphere in sub-seafloor environments and suggests, as phillipsite is one of the most common zeolite mineral in volcanic rocks of the oceanic crust, that it could be a common feature in the oceanic crust

  20. Nanoanalytical Electron Microscopy Reveals a Sequential Mineralization Process Involving Carbonate-Containing Amorphous Precursors.

    PubMed

    Nitiputri, Kharissa; Ramasse, Quentin M; Autefage, Hélène; McGilvery, Catriona M; Boonrungsiman, Suwimon; Evans, Nicholas D; Stevens, Molly M; Porter, Alexandra E

    2016-07-26

    A direct observation and an in-depth characterization of the steps by which bone mineral nucleates and grows in the extracellular matrix during the earliest stages of maturation, using relevant biomineralization models as they grow into mature bone mineral, is an important research goal. To better understand the process of bone mineralization in the extracellular matrix, we used nanoanalytical electron microscopy techniques to examine an in vitro model of bone formation. This study demonstrates the presence of three dominant CaP structures in the mineralizing osteoblast cultures: <80 nm dense granules with a low calcium to phosphate ratio (Ca/P) and crystalline domains; calcium phosphate needles emanating from a focus: "needle-like globules" (100-300 nm in diameter) and mature mineral, both with statistically higher Ca/P compared to that of the dense granules. Many of the submicron granules and globules were interspersed around fibrillar structures containing nitrogen, which are most likely the signature of the organic phase. With high spatial resolution electron energy loss spectroscopy (EELS) mapping, spatially resolved maps were acquired showing the distribution of carbonate within each mineral structure. The carbonate was located in the middle of the granules, which suggested the nucleation of the younger mineral starts with a carbonate-containing precursor and that this precursor may act as seed for growth into larger, submicron-sized, needle-like globules of hydroxyapatite with a different stoichiometry. Application of analytical electron microscopy has important implications in deciphering both how normal bone forms and in understanding pathological mineralization. PMID:27383526

  1. Milk fat globule membrane coating of large lipid droplets in the diet of young mice prevents body fat accumulation in adulthood.

    PubMed

    Baars, Annemarie; Oosting, Annemarie; Engels, Eefje; Kegler, Diane; Kodde, Andrea; Schipper, Lidewij; Verkade, Henkjan J; van der Beek, Eline M

    2016-06-01

    Epidemiological studies have demonstrated protective effects of breast-feeding on childhood obesity. Differences between human milk and infant milk formula (IMF) in dietary lipid structure may contribute to this effect. In our mouse model, feeding a diet containing large lipid droplets coated with phospholipids (PL) (Nuturis®; PL of milk fat globule membrane (MFGM) fraction origin) in early life protected against excessive body fat accumulation following a diet challenge in adult life. We now set out to determine the relevance of increased droplet size and/or MFGM lipid droplet coating to the observed anti-obesogenic effects in adult life. From day 16 to 42, male mouse pups were exposed to diets with small (S) or large (L) lipid droplets (0·3 v. 2·9 µm average mode diameter, respectively), either without MFGM or with MFGM coating around the lipid droplet, resulting in four groups: S (control diet), L, Scoating and Lcoating (Nuturis® IMF diet). Mice were subsequently challenged with a Western-style diet until dissection at postnatal day 98. A non-challenged group served as reference (REF). We repeatedly determined body composition between postnatal day 42 and 98. At day 98 plasma and gene expression measurements were performed. Only the Nuturis® IMF diet (Lcoating) in early life containing MFGM-coated large lipid droplets reduced body fat mass to a level comparable with the REF group. These data support the notion that the structural aspects of lipids in human milk, for example, both lipid droplet size as well as the MFGM coating, may contribute to its reported protective effect against obesity in later life. PMID:27040581

  2. The temperature-dependent physical state of polar lipids and their miscibility impact the topography and mechanical properties of bilayer models of the milk fat globule membrane.

    PubMed

    Murthy, Appala Venkata Ramana; Guyomarc'h, Fanny; Lopez, Christelle

    2016-09-01

    The polar lipid assembly and biophysical properties of the biological membrane enveloping the milk fat globules (the MFGM) are yet poorly known, especially in connection with the temperature history that milk can experience after its secretion. However, bioactive mechanisms depend on biological structure, which itself highly depend on temperature. The objectives of this study were to investigate polar lipid packing in hydrated bilayers, models of the MFGM, and to follow at intermolecular level temperature-induced changes in the range 60-6°C, using the combination of differential scanning calorimetry, X-ray diffraction, atomic force microscopy (AFM) imaging and force spectroscopy. MFGM polar lipids, especially sphingomyelin, contain long chain saturated fatty acids with high phase transition temperatures. On cooling, the liquid disordered ld to solid ordered so (gel) phase transition of MFGM polar lipids started at about 40°C, leading to phase separation and formation of so phase domains protruding by about 1nm from the ld phase. Indentation measurements using AFM revealed that the resistance of the so phase domains to rupture was significantly higher than that of the ld phase and that it increased for both the domain and fluid phases with decreasing temperature. However, packing and stability of the bilayers were adversely affected by fast cooling to 6°C or by cooling-rewarming cycle. This study showed that MFGM polar lipid bilayers are dynamic systems. Heterogeneity in the structure and mechanical properties of the membrane was induced by temperature-dependent so/ld phase immiscibility of the lipid components. This could have consequences on the MFGM technological and biological functions (e.g. immunity and milk lipid digestion). PMID:27349732

  3. Role of ionic liquid on the conformational dynamics in the native, molten globule, and unfolded states of cytochrome c: a fluorescence correlation spectroscopy study.

    PubMed

    Sen Mojumdar, Supratik; Chowdhury, Rajdeep; Chattoraj, Shyamtanu; Bhattacharyya, Kankan

    2012-10-11

    The role of a room temperature ionic liquid (RTIL, [pmim][Br]) on the size and conformational dynamics of a protein, horse heart cytochrome c (Cyt C) in its native, molten globule (MG-I and II), and unfolded states is studied using fluorescence correlation spectroscopy (FCS). For this purpose, the protein was covalently labeled by a fluorescent dye, Alexa Fluor 488. It is observed that the addition of the RTIL leads to an increase in the hydrodynamic radius (r(H)) of the protein, Cyt C in the native or MG-I state. In contrast, the addition of RTIL causes a decrease in the size (hydrodynamic radius, r(H)) of Cyt C unfolded by GdnHCl or MG-II state. The decrease in size indicates the formation of a relatively compact structure. We detected two types of conformational relaxation of the protein. The shorter relaxation time component (~3-5.5 μs) corresponds to the protein folding or intrachain contact formation, while the relatively longer time component (~63-122 μs) may be assigned to the motion of the protein side chains or concerted chain dynamics. The burst integrated fluorescence lifetime histograms indicate that the increase in size of the protein is accompanied by an increase in the contribution of the shorter component (~0.3-0.4 ns) with a concomitant decrease of the contribution of the longer component (~2.8-3.6 ns). An opposite trend is observed during the decrease in size of the protein. PMID:22989328

  4. Genetic polymorphism in milk fat globule-EGF factor 8 (MFG-E8) is associated with systemic lupus erythematosus in human.

    PubMed

    Hu, C Y; Wu, C S; Tsai, H F; Chang, S K; Tsai, W I; Hsu, P N

    2009-07-01

    Milk fat globule-EGF factor 8 (MFG-E8) is a molecule implicated in phagocytic clearance of apoptotic cells by bridging between macrophages and apoptotic cells. Defects in MFG-E8 cause lupus-like disease in murine models. The aim of our study is to determine whether genetic variation in MFG-E8 predisposes human to systemic lupus erythematosus (SLE). A case-control study of MFG-E8 genetic polymorphism was performed on 147 SLE patients and 146 non-lupus control subjects. Single nucleotide polymorphisms (SNPs) in the coding sequence of human MFG-E8 gene were investigated. SNPs on MFG-E8 residues 3 (3(Arg or Ser)) and 76 (76(Leu or Met)) did not show genetic linkage. Genetic polymorphism on MFG-E8 residue 76 correlated significantly to SLE. The MFG-E8-76(Met) allele predisposed subjects to SLE in a recessive mode (odds ratio: 2.1, P = 0.020), while carriage of MFG-E8-76(Leu) were negatively associated with SLE. The MFG-E8 genotypic combinations with 3(Ser) and 76(Leu) showed the most pronounced protective effect on SLE when compared to the most predisposing genotype 3(Arg/Arg)-76(Met/Met) (OR: 0.29, P = 0.007). According to our result, MFG-E8 is associated with SLE predisposition in Taiwanese. Our study implicates that the impairment of phagocytic clearance of apoptotic cells through phosphotidylserine-dependent MFG-E8 system may lead to the development of human SLE. PMID:19502262

  5. Microstructure, elastic and inelastic properties of partially graphitized biomorphic carbons

    NASA Astrophysics Data System (ADS)

    Orlova, T. S.; Kardashev, B. K.; Smirnov, B. I.; Gutierrez-Pardo, A.; Ramirez-Rico, J.; Martinez-Fernandez, J.

    2015-03-01

    The microstructural characteristics and amplitude dependences of the Young's modulus E and internal friction (logarithmic decrement δ) of biocarbon matrices prepared by beech wood carbonization at temperatures T carb = 850-1600°C in the presence of a nickel-containing catalyst have been studied. Using X-ray diffraction and electron microscopy, it has been shown that the use of a nickel catalyst during carbonization results in a partial graphitization of biocarbons at T carb ≥ 1000°C: the graphite phase is formed as 50- to 100-nm globules at T carb = 1000°C and as 0.5- to 3.0-μm globules at T carb = 1600°C. It has been found that the measured dependences E( T carb) and δ( T carb) contain three characteristic ranges of variations in the Young's modulus and logarithmic decrement with a change in the carbonization temperature: E increases and δ decreases in the ranges T carb < 1000°C and T carb > 1300°C; in the range 1000 < T carb < 1300°C, E sharply decreases and δ increases. The observed behavior of E( T carb) and δ( T carb) for biocarbons carbonized in the presence of nickel correlates with the evolution of their microstructure. The largest values of E are obtained for samples with T carb = 1000 and 1600°C. However, the samples with T carb = 1600°C exhibit a higher susceptibility to microplasticity due to the presence of a globular graphite phase that is significantly larger in size and total volume.

  6. Micelles: Rod-to-Globule Transition of pDNA/PEG-Poly(l-Lysine) Polyplex Micelles Induced by a Collapsed Balance Between DNA Rigidity and PEG Crowdedness (Small 9/2016).

    PubMed

    Tockary, Theofilus A; Osada, Kensuke; Motoda, Yusuke; Hiki, Shigehiro; Chen, Qixian; Takeda, Kaori M; Dirisala, Anjaneyulu; Osawa, Shigehito; Kataoka, Kazunori

    2016-03-01

    Upon PEG removal, the change of rod shapes into globule shapes is observed for packaged DNA in polyplex micelles that are prepared from block copolymers with acid-labile linkage between the PEG and poly(L-lysine) (PLys). On page 1193, K. Osada, K. Kataoka, and co-workers use the details of this transition behavior to elucidate the essential regulating factors of polyplex micelle structures, in order to find their structure-function relationship and promote their utilization as a gene delivery system. PMID:26928997

  7. Milk Fat Globule-Epidermal Growth Factor 8 (MFG-E8) Is a Novel Anti-inflammatory Factor in Rheumatoid Arthritis in Mice and Humans.

    PubMed

    Albus, Elise; Sinningen, Kathrin; Winzer, Maria; Thiele, Sylvia; Baschant, Ulrike; Hannemann, Anke; Fantana, Julia; Tausche, Anne-Kathrin; Wallaschofski, Henri; Nauck, Matthias; Völzke, Henry; Grossklaus, Sylvia; Chavakis, Triantafyllos; Udey, Mark C; Hofbauer, Lorenz C; Rauner, Martina

    2016-03-01

    Milk fat globule-epidermal growth factor 8 (MFG-E8) is an anti-inflammatory glycoprotein that mediates the clearance of apoptotic cells and is implicated in the pathogenesis of autoimmune and inflammatory diseases. Because MFG-E8 also controls bone metabolism, we investigated its role in rheumatoid arthritis (RA), focusing on inflammation and joint destruction. The regulation of MFG-E8 by inflammation was assessed in vitro using osteoblasts, in arthritic mice and in patients with RA. K/BxN serum transfer arthritis (STA) was applied to MFG-E8 knock-out mice to assess its role in the pathogenesis of arthritis. Stimulation of osteoblasts with lipopolysaccharide (LPS) and tumor necrosis factor (TNF)-α downregulated the expression of MFG-E8 by 30% to 35%. MFG-E8-deficient osteoblasts responded to LPS with a stronger production of pro-inflammatory cytokines. In vivo, MFG-E8 mRNA levels were 52% lower in the paws of collagen-induced arthritic (CIA) mice and 24% to 42% lower in the serum of arthritic mice using two different arthritis models (CIA and STA). Similarly, patients with RA (n = 93) had lower serum concentrations of MFG-E8 (-17%) compared with healthy controls (n = 140). In a subgroup of patients who had a moderate to high disease activity (n = 21), serum concentrations of MFG-E8 rose after complete or partial remission had been achieved (+67%). Finally, MFG-E8-deficient mice subjected to STA exhibited a stronger disease burden, an increased number of neutrophils in the joints, and a more extensive local and systemic bone loss. This was accompanied by an increased activation of osteoclasts and a suppression of osteoblast function in MFG-E8-deficient mice. Thus, MFG-E8 is a protective factor in the pathogenesis of RA and subsequent bone loss. Whether MFG-E8 qualifies as a novel biomarker or therapeutic target for the treatment of RA is worth addressing in further studies. © 2015 American Society for Bone and Mineral Research. PMID:26391522

  8. Isotope geochemistry of caliche developed on basalt

    NASA Astrophysics Data System (ADS)

    Knauth, L. Paul; Brilli, Mauro; Klonowski, Stan

    2003-01-01

    Enormous variations in oxygen and carbon isotopes occur in caliche developed on < 3 Ma basalts in 3 volcanic fields in Arizona, significantly extending the range of δ 18O and δ 13C observed in terrestrial caliche. Within each volcanic field, δ 18O is broadly co-variant with δ 13C and increases as δ 13C increases. The most 18O and 13C enriched samples are for subaerial calcite developed on pinnacles, knobs, and flow lobes that protrude above tephra and soil. The most 18O and 13C depleted samples are for pedogenic carbonate developed in soil atmospheres. The pedogenic caliche has δ 18O fixed by normal precipitation in local meteoric waters at ambient temperatures and has low δ 13C characteristic of microbial soil CO 2. Subaerial caliche has formed from 18O-rich evapoconcentrated meteoric waters that dried out on surfaces after local rains. The associated 13C enrichment is due either to removal of 12C by photosynthesizers in the evaporating drops or to kinetic isotope effects associated with evaporation. Caliche on basalt lava flows thus initially forms with the isotopic signature of evaporation and is subsequently over-layered during burial by calcite carrying the isotopic signature of the soil environment. The large change in carbon isotope composition in subsequent soil calcite defines an isotopic biosignature that should have developed in martian examples if Mars had a "warm, wet" early period and photosynthesizing microbes were present in the early soils. The approach can be similarly applied to terrestrial Precambrian paleocaliche in the search for the earliest record of life on land. Large variations reported for δ 18O of carbonate in Martian meteorite ALH84001 do not necessarily require high temperatures, playa lakes, or flood runoff if the carbonate is an example of altered martian caliche.

  9. Entrainment in solution of an oscillating NADH oxidase activity from the bovine milk fat globule membrane with a temperature-compensated period length suggestive of an ultradian time-keeping (clock) function

    NASA Technical Reports Server (NTRS)

    Morre, D. James; Lawler, Juliana; Wang, Sui; Keenan, Thomas W.; Morre, Dorothy M.

    2002-01-01

    Entrainment in solution of an oscillating activity with a temperature compensated period of 24 min is described for a NADH oxidase (NOX) activity of the bovine milk fat globule membrane, a derivative of the mammary epithelial cell plasma membrane. The period of 24 min remained unchanged at 17 degrees C, 27 degrees C and 37 degrees C whereas the amplitude approximately doubled with each 10 degree C rise in temperature (Q(10)congruent with 2). The periodicity was observed with both intact milk fat globule membranes and with detergent-solubilized membranes, demonstrating that the oscillations did not require an association with membranes. The periodicity was not the result of instrument variation or of chemical interactions among reactants in solution. Preparations with different periodicities entrained (autosynchronized) when mixed. Upon mixing, the preparations exhibited two oscillatory patterns but eventually a single pattern representing the mean of the farthest separated maxima of the two preparations analyzed separately emerged. The cell surface NOX protein is the first reported example of an entrainable biochemical entity with a temperature-compensated periodicity potentially capable of functioning as an ultradian or circadian clock driver.

  10. Cathodoluminescence : an imaging technique for the search of extraterrestrial life

    NASA Astrophysics Data System (ADS)

    Ramboz, C.; Rubert, Y.; Bost, N.; Westall, F.; Lerouge, C.

    2012-04-01

    Solids irradiated by a 10-20 keV electron beam emit ligth in the UV-visible range, which is called cathodoluminescence (CL). CL imagery is a powerful tool for visualizing minerals and their internal structures (lattice defects, zoning). For example, terrestrial calcite, either of sedimentary or biogenic origin, often display a bright orange CL, as a result of the incorporation of trace Mn2+ in its lattice. Aragonite can also be discriminated from calcite by its green CL. Carbonates are a major target for the search of life on Mars, and CL imagery could contribute to reveal carbonates in situ. Thomas et al. [1] have validated the concept of an electron lamp to make CL imagery of a rock surface placed in a martian CO2 atmosphere. We present 2 examples of terrestrial bacterial microstructures that are revealed by CL. (1) In Sinemurian sediments from the Montmiral borehole (Valence Basin, France), banded wavy calcite in contact with pyrite represents fossilized biofilms of sulfato-reducing bacteria, as confirmed by the sulfur isotopic composition of pyrite ~+36 %0 PDB. (2) At l'Ile Crémieux, north of the Valence basin, a dense filamentous microbial/fungal community with a bright orange CL signature is embedded in vuggy calcite from a tectonic vein. The mat is anchored 1-2 mm deep in the oolitic veinwall and emerges at right angle in the 'open' fracture space. Finally, carbonate vesicles and exhalite crusts from the Svalbard basalt in Groendland, with orange CL, are shown as analogues to carbonates from the martian ALH84001 igneous meteorite. [1]Thomas et al. (2009) in A. Gucsik (Ed.) "Cathodoluminescence and Its Application in the Planetary Sciences"

  11. Early Mars: A Warm Wet Niche for Life

    NASA Technical Reports Server (NTRS)

    Gibson, Everett K.; McKay, David S.; Thomas-Keprta, Kathie L.; Clemett, Simon J.

    2010-01-01

    Exploration of Mars has begun to unveil the history of the planet. Combinations of remote sensing, in situ compositional measurements and photographic observations have shown Mars had a dynamic and active geologic evolution. Mars geologic evolution had conditions that were suitable for supporting life. A habitable planet must have water, carbon and energy sources along with a dynamic geologic past. Mars meets all of these requirements. The first 600 Ma of Martian history were ripe for life to develop because of the abundance of: (i) Water-as shown by carved canyons and oceans or lakes with the early presence of near surface water shown by precipitated carbonates in ALH84001, well-dated at approx.3.9 Ga, (ii) Energy from the original accretional processes, a molten core which generated a strong magnetic field leaving a permanent record in the early crust, active volcanism continuing throughout Martian history, and continuing impact processes, (iii) Carbon, water and a likely thicker atmosphere from extensive volcanic outgassing (i.e. H2O, CO2, CH4, CO, O2, N2, H2S, SO2, etc.) and (iv) crustal tectonics as revealed by faulting and possible plate movement reflected by the magnetic patterns in the crust [1]. The question arises: "Why would life not develop from these favorable conditions on Mars in its first 600 Ma?" During this period, environmental near-surface conditions on Mars were more favorable to life than at any later time. Standing bodies of water, precipitation and flowing surface water, and possibly abundant hydrothermal energy would favor the formation of early life. (Even if life developed elsewhere on Earth, Venus, or on other bodies-it was transported to Mars where surface conditions were suitable for life to evolve)

  12. Conditions on Early Mars Might Have Fostered Rapid and Early Development of Life

    NASA Technical Reports Server (NTRS)

    Gibson, Everett K.; McKay, David S.; Thomas-Keprta, Kathie L.; Clemett, Simon J.; Wentworth, Susan J.

    2007-01-01

    The exploration of Mars during the past decades has begun to unveil the history of the planet. The combinations of remote sensing, in situ geochemical compositional measurements and photographic observations from both above and on the surface have shown Mars to have a dynamic and active geologic evolution. Mars geologic evolution clearly had conditions that were suitable for supporting life. For a planet to be able to be habitable, it must have water, carbon sources, energy sources and a dynamic geologic past. Mars meets all of these requirements. The first 600 My of Martian history were ripe for life to develop because of the abundance of (i) Water-carved canyons and oceans or lakes with the early presence of near surface water shown by precipitated carbonates in ALH84001 well-dated at approx.3.9 Gy., (ii) Energy from the original accretional processes, a molten core which generated a strong magnetic field leaving a permanent record in the early crust, early active volcanism continuing throughout Martian history, and, and continuing impact processes, (iii) Carbon and water from possibly extensive volcanic outgassing (i.e. H2O, CO2, CH4, CO, O2, N2, H2S, SO2, etc.) and (iv) some crustal tectonics as revealed by faulting and possible plate movement reflected by the magnetic pattern in the crust. The question arises: "Why would life not evolve from these favorable conditions on early Mars in its first 600 My?" During this period, it seems likely that environmental near-surface conditions on Mars were more favorable to life than at any later time. Standing bodies of water, precipitation and flowing surface water, and possibly abundant hydrothermal energy would all favor the formation of early life. Even if life developed elsewhere (on Earth, Venus, or on other solar systems) and was transported to Mars, the surface conditions were likely very hospitable for that introduced life to multiply and evolve.

  13. Carbonate-silicate liquid immiscibility in the mantle propels kimberlite magma ascent

    NASA Astrophysics Data System (ADS)

    Kamenetsky, Vadim S.; Yaxley, Gregory M.

    2015-06-01

    Kimberlite is a rare volcanic rock renowned as the major host of diamonds and originated at the base of the subcontinental lithospheric mantle. Although kimberlite magmas are dense in crystals and deeply-derived rock fragments, they ascend to the surface extremely rapidly, enabling diamonds to survive. The unique physical properties of kimberlite magmas depend on the specific compositions of their parental melts that, in absence of historical eruptions and due to pervasive alteration of kimberlite rocks, remain highly debatable. We explain exceptionally rapid ascent of kimberlite magma from mantle depths by combining empirical data on the essentially carbonatite composition of the kimberlite primary melts and experimental evidence on interaction of the carbonate liquids with mantle minerals. Our experimental study shows that orthopyroxene is completely dissolved in a Na2CO3 melt at 2.0-5.0 GPa and 1000-1200 °C. The dissolution of orthopyroxene results in homogeneous silicate-carbonate melt at 5.0 GPa and 1200 °C, and is followed by unmixing of carbonate and carbonated silicate melts and formation of stable magmatic emulsion at lower pressures and temperatures. The dispersed silicate melt has a significant capacity for storing a carbonate component in the deep mantle (13 wt% CO2 at 2.0 GPa). We envisage that this component reaches saturation and is gradually released as CO2 bubbles, as the silicate melt globules are transported upwards through the lithosphere by the carbonatite magma. The globules of unmixed, CO2-rich silicate melt are continuously produced upon further reaction between the natrocarbonatite melt and mantle peridotite. On decompression the dispersed silicate melt phase ensures a continuous supply of CO2 bubbles that decrease density and increase buoyancy and promote rapid ascent of the magmatic emulsion.

  14. Beagle 2: The Next Exobiology Mission to Mars

    NASA Technical Reports Server (NTRS)

    Gibson, Everett K., Jr.; Pillinger, Colin T.; Wright, Ian P.; Morse, Andy; Stewart, Jenny; Morgan, G.; Praine, Ian; Leigh, Dennis; Sims, Mark R.

    2001-01-01

    Beagle 2 is a 60 kg probe (with a 30 kg lander) developed in the United Kingdom for inclusion on the European Space Agency's 2003 Mars Express. Beagle 2 will deliver to the Martian surface a payload which consists of a high percentage of science instruments to landed spacecraft mass. Beagle 2 will be launched in June, 2003 with Mars Express on a Soyuz-Fregat rocket from the Baikonur Cosmodrome in Kazakhstan. Beagle 2 will land on Mars on December 26, 2003 in the Isidis Planitia basin (approximately 10 degrees N and 275 degrees W), a large sedimentary basin that overlies the boundary between ancient highlands and northern plains. Isidis Planitia, the third largest basin on Mars, which is possibly filled with sediment deposited at the bottom of long-standing lakes or seas, offers an ideal environment for preserving traces of life. Beagle 2 was developed to search for organic material and other volatiles on and below the surface of Mars in addition to the study of the inorganic chemistry and mineralogy. Beagle 2 will utilize a mechanical mole and grinder to obtain samples from below the surface, under rocks and inside rocks. A pair of stereo cameras will image the landing site along with a microscope for examination of surface and rock samples. Analyses will include both rock and soil samples at various wavelengths, X-ray spectrometer and Mossbauer spectrometer as well as a search for organics and other light element species (e.g. carbonates and water) and measurement of their isotopic compositions. Beagle 2 has as its focus the goal of establishing whether evidence for life existed in the past on Mars at the Isidis Planitia site or at least establishing if the conditions were ever suitable. Carbonates and organic components were first recognized as existing on Mars when they were found in the Martian meteorite Nakhla. Romanek et al showed the carbonates in ALH84001 were formed at low temperatures. McKay et al noted possible evidence of early life on Mars within the

  15. A review of meteorite evidence for the timing of magmatism and of surface or near-surface liquid water on Mars

    NASA Astrophysics Data System (ADS)

    Borg, Lars; Drake, Michael J.

    2005-09-01

    There is widespread photogeological evidence for ubiquitous water flowing on the surface of Mars. However, the age of surface and near-surface water cannot be deduced with high precision from photogeology. While there is clear evidence for old and young fluvial features in the photogeologic record, the uncertainty in the absolute calibration of the Martian crater flux results in uncertainties of +/-1.5 Gyr in the middle period of Martian geologic history. Aqueous alteration of primary igneous minerals produces secondary minerals in Martian meteorites. Here we use the ages of secondary alteration minerals in Martian meteorites to obtain absolute ages when liquid water was at or near the surface of Mars. Aqueous alteration events in Martian meteorites occurred at 3929 +/- 37 Ma (carbonates in ALH84001), 633 +/- 23 Ma (iddingsite in nakhlites), and 0-170 Ma (salts in shergottites). Furthermore, these events appear to be of short duration, suggesting episodic rather than continuous aqueous alteration of the meteorites. The Martian meteorites appear to be contaminated by Martian surface Pb characterized by a 207Pb/206Pb ratio near 1. Lead of this composition could be produced by water-based alteration on the Martian surface. The high 129Xe/132Xe ratio in the Martian atmosphere compared to Martian meteorites indicates fractionation of I from Xe within ~100 Myr after nucleosynthesis of 129I. Such fractionation is difficult to achieve through magmatic processes. However, water very efficiently fractionates I from Xe, raising the intriguing possibility that Mars had a liquid water ocean within its first 100 Myr.1.

  16. Fluid Inclusions in Extraterrestrial Samples Fact or Fiction?

    NASA Technical Reports Server (NTRS)

    Bodnar, R. J.; Zolensky, M. E.; Gibson, E. K.

    2000-01-01

    Over the years there have been numerous reports of liquid inclusions in meteorites. Roedder reviews the reported occurrences of liquid inclusions in meteorites and states that "silicate-melt inclusions are expectable and apparently ubiquitous, but the presence of actual liquid inclusions (i.e., with moving bubbles at room temperature) would seem almost impossible." The reason for this conclusion is that meteorites (presumably) form in space at high temperatures and very low pressures where liquid water (or carbon dioxide) is not stable. Perhaps the most infamous report of fluid inclusions in meteorites was that of Warner et al. In that study, the authors reported the presence of two-phase, liquid-vapor inclusions in a diogenite from Antarctica. This report of fluid inclusions generated considerable interest in the meteorite community, and caused many to question existing models for the origin of the diogenites. This interest was short-lived however, as later investigations of the same samples showed that the inclusions were most likely artifacts. Rudnick et al. showed that many of the inclusions in meteorites prepared at the Johnson Space Center contained a fluid that fluoresced strongly under the laser beam on the Raman microprobe. They interpreted this to indicate that the inclusions contained Almag oil used in the preparation of thin sections. Presumably, the Almag oil entered empty vesicles along fractures that were opened intermittently during cutting. Here, the occurrence of unambiguous fluid inclusions that could not have been introduced during sample preparation are described in samples from two different extraterrestrial environments. One environment is represented by the SNC (martian) meteorites ALH 84001 and Nakhla. The second environment is represented by the Monahans 1998 meteorite that fell recently in the USA.

  17. Microfossils, biominerals, and chemical biomarkers in meteorites

    NASA Astrophysics Data System (ADS)

    Hoover, Richard B.; Rozanov, Alexei Y.

    2003-01-01

    The discovery of biominerals, chemical biomarkers and evidence of microfossils in the Mars meteorite (ALH84001) stimulated research into biomarkers, microbial extremophiles and provided impetus to the newly emerging fields of Astrobiology and Bacterial Paleontology. The debate following the ALH84001 results has highlighted the importance of developing methodologies for recognition of mineral and elemental bioindicators, chemical biomarkers and microfossils in terrestrial rocks and meteorites prior to sample return missions to comets, asteroids, and Mars. Comparative studies of living and fossil micro-organisms and biomarkers are vital to developing expertise needed to recognize indigenous biosignatures and recent contaminants. This paper reviews elemental and mineral bioindicators, chemical biomarkers and keropgen in terrestrial rocks and meteorites. Electron Microscopy images of hyperthermophilic nanobacteria, sulfur and sulfate reducing bacteria, and mineralized microfossils and kerogen found in-situ in carbonaceous meteorite rock matrix are presented.

  18. Nannobacterial alteration of pyroxenes in martian meteorite Allan Hills 84001

    NASA Astrophysics Data System (ADS)

    Folk, Robert L.; Taylor, Lawrence A.

    2002-08-01

    In martian meteorite Allan Hills (ALH) 84001, this scanning electron microscope study was focused on the ferromagnesian minerals, which are extensively covered with nanometer-size bodies mainly 30-100 nm in diameter. These bodies range from spheres to ovoids to caterpillar shapes and resemble, both in size and shape, nannobacteria that attack weathered rocks on Earth and that can be cultured. Dense colonies alternate with clean, smooth cleavage surfaces, possibly formed later. Statistical study shows that the distribution of presumed nannobacteria is very clustered. In addition to the small bodies, there are a few occurrences of ellipsoidal 200-400 nm objects, that are within the lower size range of "normal" earthly bacteria. We conclude that the nanobodies so abundant in ALH 84001 are indeed nannobacteria, confirming the initial assertion of McKay et al. (1996). However, whether these bodies originated on Mars or are Antarctic contamination remains a valid question.

  19. Micro-scale experimental investigation of the effect of flow rate on trapping in sandstone and carbonate rock samples

    NASA Astrophysics Data System (ADS)

    Khishvand, Mahdi; Akbarabadi, Morteza; Piri, Mohammad

    2016-08-01

    We present the results of a pore-scale experimental study of residual trapping in consolidated sandstone and carbonate rock samples under confining stress. We investigate how the changes in wetting phase flow rate impacts pore-scale distribution of fluids during imbibition in natural, water-wet porous media. We systematically study pore-scale trapping of the nonwetting phase as well as size and distribution of its disconnected globules. Seven sets of drainage-imbibition experiments were performed with brine and oil as the wetting and nonwetting phases, respectively. We utilized a two-phase miniature core-flooding apparatus integrated with an X-ray microtomography system to examine pore-scale fluid distributions in small Bentheimer sandstone (D = 4.9 mm and L = 13 mm) and Gambier limestone (D = 4.4 mm and L = 75 mm) core samples. The results show that with increase in capillary number, the residual oil saturation at the end of the imbibition reduces from 0.46 to 0.20 in Bemtheimer sandstone and from 0.46 to 0.28 in Gambier limestone. We use pore-scale displacement mechanisms, in-situ wettability characteristics, and pore size distribution information to explain the observed capillary desaturation trends. The reduction was believed to be caused by alteration of the order in which pore-scale displacements took place during imbibition. Furthermore, increase in capillary number produced significantly different pore-scale fluid distributions during imbibition. We explored the pore fluid occupancies and studied size and distribution of the trapped oil clusters during different imbibition experiments. The results clearly show that as the capillary number increases, imbibition produces smaller trapped oil globules. In other words, the volume of individual trapped oil globules decreased at higher brine flow rates. Finally, we observed that the pore space in the limestone sample was considerably altered through matrix dissolution at extremely high brine flow rates. This

  20. Carbon-carbon cylinder block

    NASA Technical Reports Server (NTRS)

    Ransone, Philip O. (Inventor)

    1998-01-01

    A lightweight cylinder block composed of carbon-carbon is disclosed. The use of carbon-carbon over conventional materials, such as cast iron or aluminum, reduces the weight of the cylinder block and improves thermal efficiency of the internal combustion reciprocating engine. Due to the negligible coefficient of thermal expansion and unique strength at elevated temperatures of carbon-carbon, the piston-to-cylinder wall clearance can be small, especially when the carbon-carbon cylinder block is used in conjunction with a carbon-carbon piston. Use of the carbon-carbon cylinder block has the effect of reducing the weight of other reciprocating engine components allowing the piston to run at higher speeds and improving specific engine performance.

  1. Carbon-Carbon Radiator

    NASA Technical Reports Server (NTRS)

    Butler, Dan; Powers, Edward I. (Technical Monitor)

    2001-01-01

    Carbon-Carbon (C-C) Radiator was a success and proved that the technology can work to reduce Spacecraft weight. C-C has a niche, especially for high temperatures. C-C still needs further development: reduction in fabrication time and cost - high conductivity "traditional" composites are more competitive, and CTE interface issues with heat pipes. Redundancy a good idea - we flew the spare panel. CSRP was a success -informal inter-agency partnership. Possible follow-on: C-C foam for low CTE mirrors/optical benches.

  2. Carbon Smackdown: Carbon Capture

    ScienceCinema

    Jeffrey Long

    2010-09-01

    In this July 9, 2010 Berkeley Lab summer lecture, Lab scientists Jeff Long of the Materials Sciences and Nancy Brown of the Environmental Energy Technologies Division discuss their efforts to fight climate change by capturing carbon from the flue gas of power plants, as well as directly from the air

  3. Carbon Smackdown: Carbon Capture

    SciTech Connect

    Jeffrey Long

    2010-07-12

    In this July 9, 2010 Berkeley Lab summer lecture, Lab scientists Jeff Long of the Materials Sciences and Nancy Brown of the Environmental Energy Technologies Division discuss their efforts to fight climate change by capturing carbon from the flue gas of power plants, as well as directly from the air

  4. Paleointensity of the Martian field from SQUID Microscopy

    NASA Astrophysics Data System (ADS)

    Weiss, B. P.; Fong, L. E.; Lima, E. A.; Baudenbacher, F. J.; Vali, H.

    2005-12-01

    Crustal magnetic anomalies in the southern Martian hemisphere have intensities an order of magnitude larger than typical crustal anomalies on Earth. Two possible explanations for this difference are that compared to the present-day Earth, Mars has either (i) larger amounts of crustal ferromagnetic minerals or (ii) the crust was magnetized by a larger paleofield. ALH84001, the only pre-Amazonian Martian meteorite, possesses a stable magnetization dating to 4 Ga or earlier. Previous paleomagnetic studies with SQUID moment magnetometers on bulk ALH84001 grains have estimated that the paleointensity of the field which magnetized the meteorite was between 0.1-1 times that of the Earth's present field. However, these estimates may be lower limits on the true paleointensity because the orientation of the magnetization in ALH84001 is spatially heterogeneous on the submillimeter scale. This complication could have profound implications for hypothesis (ii) above. Here we first demonstrate that superconducting quantum interference device (SQUID) microscopy can recover the same magnetization intensity and direction of a well characterized modern-day terrestrial basalt as that measured with a 2G Enterprises SQUID moment magnetometer. A SQUID microscope paleointensity analysis of this basalt gives the expected present day field intensity of a few tens of microtesla. We further show that our new high resolution SQUID microscopy study of ALH84001, which has mapped its heterogeneous magnetization with the highest resolution yet (0.1 mm), favors the upper range of previous paleointensity estimates for the 4 Ga Martian paleofield (e.g., within a factor of several of that of the present-day Earth). However, this field, were it dynamo in origin, is still too weak to easily explain the intensity of the Martian magnetic anomalies.

  5. Carbonate precipitation under bulk acidic conditions as a potential biosignature for searching life on Mars

    NASA Astrophysics Data System (ADS)

    Fernández-Remolar, David C.; Preston, Louisa J.; Sánchez-Román, Mónica; Izawa, Matthew R. M.; Huang, L.; Southam, Gordon; Banerjee, Neil R.; Osinski, Gordon R.; Flemming, Roberta; Gómez-Ortíz, David; Prieto Ballesteros, Olga; Rodríguez, Nuria; Amils, Ricardo; Darby Dyar, M.

    2012-10-01

    Recent observations of carbonate minerals in ancient Martian rocks have been interpreted as evidence for the former presence of circumneutral solutions optimal for carbonate precipitation. Sampling from surface and subsurface regions of the low-pH system of Río Tinto has shown, unexpectedly, that carbonates can form under diverse macroscopic physicochemical conditions ranging from very low to neutral pH (1.5-7.0). A multi-technique approach demonstrates that carbonate minerals are closely associated with microbial activity. Carbonates occur in the form of micron-size carbonate precipitates under bacterial biofilms, mineralization of subsurface colonies, and possible biogenic microstructures including globules, platelets and dumbbell morphologies. We propose that carbonate precipitation in the low-pH environment of Río Tinto is a process enabled by microbially-mediated neutralization driven by the reduction of ferric iron coupled to the oxidation of biomolecules in microbially-maintained circumneutral oases, where the local pH (at the scale of cells or cell colonies) can be much different than in the macroscopic environment. Acidic conditions were likely predominant in vast regions of Mars over the last four billion years of planetary evolution. Ancient Martian microbial life inhabiting low-pH environments could have precipitated carbonates similar to those observed at Río Tinto. Preservation of carbonates at Río Tinto over geologically significant timescales suggests that similarly-formed carbonate minerals could also be preserved on Mars. Such carbonates could soon be observed by the Mars Science Laboratory, and by future missions to the red planet.

  6. Carbon-carbon piston development

    NASA Technical Reports Server (NTRS)

    Gorton, Mark P.

    1994-01-01

    A new piston concept, made of carbon-carbon refractory-composite material, has been developed that overcomes a number of the shortcomings of aluminum pistons. Carbon-carbon material, developed in the early 1960's, is lighter in weight than aluminum, has higher strength and stiffness than aluminum and maintains these properties at temperatures over 2500 F. In addition, carbon-carbon material has a low coefficient of thermal expansion and excellent resistance to thermal shock. An effort, called the Advanced Carbon-Carbon Piston Program was started in 1986 to develop and test carbon-carbon pistons for use in spark ignition engines. The carbon-carbon pistons were designed to be replacements for existing aluminum pistons, using standard piston pin assemblies and using standard rings. Carbon-carbon pistons can potentially enable engines to be more reliable, more efficient and have greater power output. By utilizing the unique characteristics of carbon-carbon material a piston can: (1) have greater resistance to structural damage caused by overheating, lean air-fuel mixture conditions and detonation; (2) be designed to be lighter than an aluminum piston thus, reducing the reciprocating mass of an engine, and (3) be operated in a higher combustion temperature environment without failure.

  7. Mars as the parent body of the CI carbonaceous chondrites and implications for Mars biological and climatic history

    NASA Astrophysics Data System (ADS)

    Brandenburg, John E.

    1997-07-01

    The hypothesis that CI meteorites have an origin on Mars is presented along with supporting data and implications. A Martian origin for the CI will support Martian biogenesis and effect assessments of Martian histories, suggesting Mars and Earth evolved in parallel in both biologic and geologic realms for a long period. The CI containing a Martian pattern of oxygen isotopes and mineralogy indicative of deposition by liquid water. The CI contain no evidence of hypervelocity impact, but contain space-exposed olivine grains and are thus regolith material, indicating their formation under a planetary atmosphere. They contain organic matter similar to that found in Martian meteorites, ALH84001 and EETA79001. A scenario of formation of CI meteorites as being water altered late planetary accretion material is proposed. The 4.5 Gyr age of the CI, matching ALH84001, and their high concentration of organic matter, including possible fossil bacteria, strongly supports the hypothesis of early Martian biogenesis. With CI plus ALH84001 being old, and the SNCs being young, the Martian crustal age dichotomy is now well reflected in Martian meteorite ages. This suggests Mars has a strongly bimodal pattern of crustal ages, either very old or very young with liquid water moving on the planets surface until late in the planets history.

  8. Calcium Carbonate

    MedlinePlus

    Calcium carbonate is a dietary supplement used when the amount of calcium taken in the diet is not ... for healthy bones, muscles, nervous system, and heart. Calcium carbonate also is used as an antacid to relieve ...

  9. Carbon photonics

    NASA Astrophysics Data System (ADS)

    Konov, V. I.

    2015-11-01

    The properties of new carbon materials (single-crystal and polycrystalline CVD diamond films and wafers, single-wall carbon nanotubes and graphene) and the prospects of their use as optical elements and devices are discussed.

  10. Addition of a dairy fraction rich in milk fat globule membrane to a high-saturated fat meal reduces the postprandial insulinaemic and inflammatory response in overweight and obese adults.

    PubMed

    Demmer, Elieke; Van Loan, Marta D; Rivera, Nancy; Rogers, Tara S; Gertz, Erik R; German, J Bruce; Smilowitz, Jennifer T; Zivkovic, Angela M

    2016-01-01

    Meals high in SFA, particularly palmitate, are associated with postprandial inflammation and insulin resistance. Milk fat globule membrane (MFGM) has anti-inflammatory properties that may attenuate the negative effects of SFA-rich meals. Our objective was to examine the postprandial metabolic and inflammatory response to a high-fat meal composed of palm oil (PO) compared with PO with an added dairy fraction rich in MFGM (PO+MFGM) in overweight and obese men and women (n 36) in a randomised, double-blinded, cross-over trial. Participants consumed two isoenergetic high-fat meals composed of a smoothie enriched with PO with v. without a cream-derived complex milk lipid fraction ( dairy fraction rich in MFGM) separated by a washout of 1-2 weeks. Serum cytokines, adhesion molecules, cortisol and markers of inflammation were measured at fasting, and at 1, 3 and 6 h postprandially. Glucose, insulin and lipid profiles were analysed in plasma. Consumption of the PO + MFGM v. PO meal resulted in lower total cholesterol (P = 0·021), LDL-cholesterol (P = 0·046), soluble intracellular adhesion molecule (P = 0·005) and insulin (P = 0·005) incremental AUC, and increased IL-10 (P = 0·013). Individuals with high baseline C-reactive protein (CRP) concentrations (≥3 mg/l, n 17) had higher (P = 0·030) insulin at 1 h after the PO meal than individuals with CRP concentrations <3 mg/l (n 19). The addition of MFGM attenuated this difference between CRP groups. The addition of a dairy fraction rich in MFGM attenuated the negative effects of a high-SFA meal by reducing postprandial cholesterol, inflammatory markers and insulin response in overweight and obese individuals, particularly in those with elevated CRP. PMID:27313850

  11. Myeloid-Epithelial-Reproductive Receptor Tyrosine Kinase and Milk Fat Globule Epidermal Growth Factor 8 Coordinately Improve Remodeling After Myocardial Infarction via Local Delivery of Vascular Endothelial Growth Factor

    PubMed Central

    Howangyin, Kiave-Yune; Zlatanova, Ivana; Pinto, Cristina; Ngkelo, Anta; Cochain, Clément; Rouanet, Marie; Vilar, José; Lemitre, Mathilde; Stockmann, Christian; Fleischmann, Bernd K.; Mallat, Ziad

    2016-01-01

    Background— In infarcted heart, improper clearance of dying cells by activated neighboring phagocytes may precipitate the transition to heart failure. We analyzed the coordinated role of 2 major mediators of efferocytosis, the myeloid-epithelial-reproductive protein tyrosine kinase (Mertk) and the milk fat globule epidermal growth factor (Mfge8), in directing cardiac remodeling by skewing the inflammatory response after myocardial infarction. Methods and Results— We generated double-deficient mice for Mertk and Mfge8 (Mertk−/−/Mfge8−/−) and challenged them with acute coronary ligature. Compared with wild-type, Mertk-deficient (Mertk−/−), or Mfge8-deficient (Mfge8−/−) animals, Mertk−/−/Mfge8−/− mice displayed greater alteration in cardiac function and remodeling. Mertk and Mfge8 were expressed mainly by cardiac Ly6CHigh and Low monocytes and macrophages. In parallel, Mertk−/−/Mfge8−/− bone marrow chimeras manifested increased accumulation of apoptotic cells, enhanced fibrotic area, and larger infarct size, as well as reduced angiogenesis. We found that the abrogation of efferocytosis affected neither the ability of circulating monocytes to infiltrate cardiac tissue nor the number of resident Ly6CHigh and Ly6CHow monocytes/macrophages populating the infarcted milieu. In contrast, combined Mertk and Mfge8 deficiency in Ly6CHigh/Ly6CLow monocytes/macrophages either obtained from in vitro differentiation of bone marrow cells or isolated from infarcted hearts altered their capacity of efferocytosis and subsequently blunted vascular endothelial growth factor A (VEGFA) release. Using LysMCre+/VEGFAfl/fl mice, we further identified an important role for myeloid-derived VEGFA in improving cardiac function and angiogenesis. Conclusions— After myocardial infarction, Mertk- and Mfge8-expressing monocyte/macrophages synergistically engage the clearance of injured cardiomyocytes, favoring the secretion of VEGFA to locally repair the

  12. Carbon-carbon composites

    NASA Technical Reports Server (NTRS)

    Maahs, Howard G.

    1992-01-01

    The current applications of C-C composites extend to aircraft brakes, rocket nozzles, missile nosetips, and leading edges of the Space Shuttle. More advanced, secondary and even primary structure applications in cyclic, high-temperature oxidizing environments depend on effective oxidation protection for repeated missions. Accounts are presently given of state-of-the-art methods in substrate fabrication, carbon deposition, and SiC and Si3N4 protective coatings. Attention is given to current levels of high temperature oxidation protection for various mission and vehicle types, as well as to performance projections for C-C composites used by a representative National Aerospace Plane airframe structure. Future technology requirements in C-C composites are projected.