Lithological influences on contemporary and long-term regolith weathering at the Luquillo Critical Zone Observatory

Lithologic differences give rise to the differential weatherability of the Earth’s surface and globally variable silicate weathering fluxes, which provide an important negative feedback on climate over geologic timescales. To isolate the influence of lithology on weathering rates and mechanisms, we compare two nearby catchments in the Luquillo Critical Zone Observatory in Puerto Rico, which have similar climate history, relief and vegetation, but differ in bedrock lithology. Regolith and pore water samples with depth were collected from two ridgetops and at three sites along a slope transect in the volcaniclastic Bisley catchment and compared to existing data from the granitic Río Icacos catchment. The depth variations of solid-state and pore water chemistry and quantitative mineralogy were used to calculate mass transfer (tau) and weathering solute profiles, which in turn were used to determine weathering mechanisms and to estimate weathering rates. Regolith formed on both lithologies is highly leached of most labile elements, although Mg and K are less depleted in the granitic than in the volcaniclastic profiles, reflecting residual biotite in the granitic regolith not present in the volcaniclastics. Profiles of both lithologies that terminate at bedrock corestones are less weathered at depth, near the rock-regolith interfaces. Mg fluxes in the volcaniclastics derive primarily from dissolution of chlorite near the rock-regolith interface and from dissolution of illite and secondary phases in the upper regolith, whereas in the granitic profile, Mg and K fluxes derive from biotite dissolution. Long-term mineral dissolution rates and weathering fluxes were determined by integrating mass losses over the thickness of solid-state weathering fronts, and are therefore averages over the timescale of regolith development. Resulting long-term dissolution rates for minerals in the volcaniclastic regolith include chlorite: 8.9 × 10‾¹⁴ mol m‾² s‾¹, illite: 2.1 × 10‾¹⁴ mol m‾² s‾¹ and kaolinite: 4.0 × 10‾¹⁴ mol m‾² s‾¹. Long-term weathering fluxes are several orders of magnitude lower in the granitic regolith than in the volcaniclastic, despite higher abundances of several elements in the granitic regolith. Contemporary weathering fluxes were determined from net (rain-corrected) solute profiles and thus represent rates over the residence time of water in the regolith. Contemporary weathering fluxes within the granitic regolith are similar to the long-term fluxes. In contrast, the long-term fluxes are faster than the contemporary fluxes in the volcaniclastic regolith. Contemporary fluxes in the granitic regolith are generally also slightly faster than in the volcaniclastic. The differences in weathering fluxes over space and time between these two watersheds indicate significant lithologic control of chemical weathering mechanisms and rates

A Novel Solid-Phase Site-Specific PEGylation Enhances the In Vitro and In Vivo Biostabilty of Recombinant Human Keratinocyte Growth Factor 1

Keratinocyte growth factor 1 (KGF-1) has proven useful in the treatment of pathologies associated with dermal adnexae, liver, lung, and the gastrointestinal tract diseases. However, poor stability and short plasma half-life of the protein have restricted its therapeutic applications. While it is possible to improve the stability and extend the circulating half-life of recombinant human KGF-1 (rhKGF-1) using solution-phase PEGylation, such preparations have heterogeneous structures and often low specific activities due to multiple and/or uncontrolled PEGylation. In the present study, a novel solid-phase PEGylation strategy was employed to produce homogenous mono-PEGylated rhKGF-1. RhKGF-1 protein was immobilized on a Heparin-Sepharose column and then a site-selective PEGylation reaction was carried out by a reductive alkylation at the N-terminal amino acid of the protein. The mono-PEGylated rhKGF-1, which accounted for over 40% of the total rhKGF-1 used in the PEGylation reaction, was purified to homogeneity by SP Sepharose ion-exchange chromatography. Our biophysical and biochemical studies demonstrated that the solid-phase PEGylation significantly enhanced the in vitro and in vivo biostability without affecting the over all structure of the protein. Furthermore, pharmacokinetic analysis showed that modified rhKGF-1 had considerably longer plasma half-life than its intact counterpart. Our cell-based analysis showed that, similar to rhKGF-1, PEGylated rhKGF-1 induced proliferation in NIH 3T3 cells through the activation of MAPK/Erk pathway. Notably, PEGylated rhKGF-1 exhibited a greater hepatoprotection against CCl4-induced injury in rats compared to rhKGF-1

Expression profiles of genes involved in TLRs and NLRs signaling pathways of water buffaloes infected with Fasciola gigantica

Infection of ruminants and humans with Fasciola gigantica is attracting increasing attention due to its economic impact and public health significance. However, little is known of innate immune responses during F. gigantica infection. Here, we investigated the expression profiles of genes involved in Toll-like receptors (TLRs) and NOD-like receptors (NLRs) signaling pathways in buffaloes infected with 500 F. gigantica metacercariae. Serum, liver and peripheral blood mononuclear cell (PBMC) samples were collected from infected and control buffaloes at 3, 10, 28, and 70 days post infection (dpi). Then, the levels of 12 cytokines in serum samples were evaluated by ELISA. Also, the levels of expression of 42 genes, related to TLRs and NLRs signaling, in liver and PBMCs were determined using custom RT2 Profiler PCR Arrays. At 3 dpi, modest activation of TLR4 and TLR8 and the adaptor protein (TICAM1) was detected. At 10 dpi, NF-κB1 and Interferon Regulatory Factor signaling pathways were upregulated along with activation of TLR1, TLR2, TLR6, TLR10, TRAF6, IRF3, TBK1, CASP1, CD80, and IFNA1 in the liver, and inflammatory response with activated TLR4, TLR9, TICAM1, NF- κB1, NLRP3, CD86, IL-1B, IL-6, and IL-8 in PBMCs. At 28 dpi, there was increase in the levels of cytokines along with induction of NLRP1 and NLRP3 inflammasomes-dependent immune responses in the liver and PBMCs. At 70 dpi, F. gigantica activated TLRs and NLRs, and their downstream interacting molecules. The activation of TLR7/9 signaling (perhaps due to increased B-cell maturation and activation) and upregulation of NLRP3 gene were also detected. These findings indicate that F. gigantica alters the expression of TLRs and NLRs genes to evade host immune defenses. Elucidation of the roles of the downstream effectors interacting with these genes may aid in the development of new interventions to control disease caused by F. gigantica infection

An Investigation of the Factors Controlling the Terrestrial Sulfur Cycle

AbstractAn Investigation of the Factors Controlling the Terrestrial Sulfur Cycleby Simona Andreea Yi-BalanDoctor of Philosophy in Environmental Science, Policy, and ManagementUniversity of California, BerkeleyProfessor Ronald Amundson, ChairSulfur (S), like nitrogen (N), is an essential macronutrient for life on Earth. Its deficit in soils decreases primary productivity, but its excess can impair ecosystem health. Unlike N cycling however, for which both the natural and the human-impacted cycles have been well studied, most research on S has focused on S pollution. My thesis addressed S cycling in pristine terrestrial systems, to understand the potential effects of global change on these essential functions. I used chemical analyses and stable isotopes to investigate the impact of climate, vegetation, topography, parent material and landscape age on the natural terrestrial S cycle in comparison to that of N.I examined the S content and isotopic composition (as δ34S values) in soils and vegetation at 11 sites spanning broad gradients of climate globally. Soil S content generally increased with mean annual precipitation (MAP), but was uncorrelated with mean annual temperature (MAT). Soil and plant δ34S values increased with increasing MAP and MAT. MAP and MAT together accounted for about half of the observed variability in folial δ34S values, and for over a quarter of the observed variability in soil δ34S. These S patterns resembled those of soil N, known from previous studies. The difference between the δ34S values of soils and atmospheric inputs increased significantly, but weakly, with MAP, suggesting greater biological S isotope fractionation in wetter climates.To directly explore the impact of vegetation, topography and parent material on soil S biogeochemistry, I collected soil, plant, pore water and precipitation samples from the wet tropical Luquillo Experimental Forest, Puerto Rico. Topography impacted S cycling by influencing soil redox conditions, while vegetation and parent material had a minimal impact. Pore water data suggested the co-occurrence of at least three major S-fractionating processes: plant uptake, mineralization and dissimilatory bacterial sulfate reduction (DBSR). This complex biogeochemical cycling appeared to be driven by the high rainfall. I modeled soil isotopic fractionation assuming advective transport of organic matter through the soil profile. This model worked well for N, but failed to describe S transformations, revealing a decoupling of the N and S biogeochemical cycles in these soils due to biotic processes. I found a similar decoupling of S from N cycling on a chronosequence of marine terraces in Santa Cruz, California, where I investigated the impact of landscape age. I propose that two factors account for this apparent greater redox sensitivity of S compared to N isotopes. First, S is in less biological demand, and thus more readily fractionated by redox reactions, unlike N, which might be fully consumed for plant and microbial cellular metabolism during biological processes. Second, S may experience several reduction-reoxidation cycles due to its retention in soils via adsorption on iron and aluminum oxides, unlike N, which is easily lost from soils once reduced to gaseous form. In the deeper soil layers, processes that deplete the heavy S isotope (such as DBSR) dominated in the youngest soils, while processes that enrich the soil in the heavy isotope (such as mineralization) dominated in the older soils. Furthermore, pore water data revealed a division in soil processes with depth in the older soils, with large fluctuations in sulfate concentration and isotope fractionation near the surface (likely due to DBSR), but little change below the well-developed argillic horizons. My data showed no significant effect of phosphorus limitation on S cycling in the older soils. Rather, age impacted soil S content and δ34S values mostly due to changes in hydrology, including the development of a water restrictive argillic horizon, with increasing soil age.In summary, my results showed that, of the factors examined, rainfall effects modified by landform characteristics are the most important controls on S biogeochemistry that dictate the types and rates of processes. S cycling should, therefore, most directly respond to the changes in rainfall predicted to occur due to global change. Specifically, a significant decrease in rainfall in many regions may reduce soil S content and the extent of its biological cycling

Cristallochimie des apatites biologiques et géologiques (marqueurs minéralogiques de la fossilisation)

Cette Thèse a pour but d étudier la cristallochimie des apatites, constituants majeurs des dents et des os des vertébrés, afin de discuter leur utilisation comme marqueurs de la fossilisation. Nous avons combiné des techniques expérimentales avancées (spectrométrie IR à basse température et RMN du solide) et des modélisations théoriques réalisées par des méthodes ab initio de type DFT. Le mécanisme de substitution des groupes carbonate aux groupes phosphate dans la "francolite" a pour la première fois été élucidé. L accord entre les résultats expérimentaux et leurs contreparties théoriques a permis de valider un modèle de substitution couplée où le carbonate occupe l'une des faces du site tétraédrique et le fluor le sommet opposé. Les propriétés spectrométriques spécifiques de ce défaut ont été déterminées et permettent son identification dans les échantillons naturels. D'autres modèles d'incorporation du carbonate ont également été étudiés et discutés à la lumière des résultats expérimentaux. Ces résultats ont ensuite été appliqués à l'étude de la transformation de fossiles de dents et d os. L'identification de l'environnement du carbonate de type "francolite" dans les échantillons d'émail de dents fossiles implique que celles-ci se transforment par dissolution-recristallisation. Cette observation est donc susceptible de remettre en cause l'utilisation des fossiles les plus transformés pour les reconstitutions paléo-environnementales. En comparaison, la fossilisation des os procède par un mécanisme plus complexe impliquant des réorganisations précoces de la structure phosphatée suivies à plus long terme par des remplacements par dissolution-recristallisationThis Thesis aims to study the crystal-chemistry of apatite, the main mineral constituent of vertebrate bones and teeth, in order to discuss its use as marker of fossilization. We have combined advanced experimental techniques (FTIR at low temperature and solid-state NMR MAS) and theoretical ab initio modelling carried out by DFT methods. The substitution mechanism of carbonate groups for phosphate groups in the sedimentary carbonate fluorapatite (francolite) has been for the first time elucidated. The agreement between experimental results and their theoretical counterparts allows validating a model of coupled substitution where carbonate occupies one face of the tetrahedral site and fluorine the opposite vertex. Specific spectroscopic properties of this defect have been determined and allow its identification in natural samples. Other models of carbonate incorporation have also been investigated and discussed under the light of experimental results. These results have been then applied to the study of the transformation of fossil teeth and bones. The identification of the "francolite-type carbonate defect in fossil tooth enamel implies that their transformation may occur through dissolution and recrystallization mechanisms. Our findings challenge the use of the most transformed fossils for paleoenvironmental reconstructions. In comparison, the fossil bones proceed by a complex mechanism involving early reorganization of the phosphate structure followed by longer-term replacements by dissolution-recrystallization mechanisms.PARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

An Investigation of the Factors Controlling the Terrestrial Sulfur Cycle

AbstractAn Investigation of the Factors Controlling the Terrestrial Sulfur Cycleby Simona Andreea Yi-BalanDoctor of Philosophy in Environmental Science, Policy, and ManagementUniversity of California, BerkeleyProfessor Ronald Amundson, ChairSulfur (S), like nitrogen (N), is an essential macronutrient for life on Earth. Its deficit in soils decreases primary productivity, but its excess can impair ecosystem health. Unlike N cycling however, for which both the natural and the human-impacted cycles have been well studied, most research on S has focused on S pollution. My thesis addressed S cycling in pristine terrestrial systems, to understand the potential effects of global change on these essential functions. I used chemical analyses and stable isotopes to investigate the impact of climate, vegetation, topography, parent material and landscape age on the natural terrestrial S cycle in comparison to that of N.I examined the S content and isotopic composition (as δ34S values) in soils and vegetation at 11 sites spanning broad gradients of climate globally. Soil S content generally increased with mean annual precipitation (MAP), but was uncorrelated with mean annual temperature (MAT). Soil and plant δ34S values increased with increasing MAP and MAT. MAP and MAT together accounted for about half of the observed variability in folial δ34S values, and for over a quarter of the observed variability in soil δ34S. These S patterns resembled those of soil N, known from previous studies. The difference between the δ34S values of soils and atmospheric inputs increased significantly, but weakly, with MAP, suggesting greater biological S isotope fractionation in wetter climates.To directly explore the impact of vegetation, topography and parent material on soil S biogeochemistry, I collected soil, plant, pore water and precipitation samples from the wet tropical Luquillo Experimental Forest, Puerto Rico. Topography impacted S cycling by influencing soil redox conditions, while vegetation and parent material had a minimal impact. Pore water data suggested the co-occurrence of at least three major S-fractionating processes: plant uptake, mineralization and dissimilatory bacterial sulfate reduction (DBSR). This complex biogeochemical cycling appeared to be driven by the high rainfall. I modeled soil isotopic fractionation assuming advective transport of organic matter through the soil profile. This model worked well for N, but failed to describe S transformations, revealing a decoupling of the N and S biogeochemical cycles in these soils due to biotic processes. I found a similar decoupling of S from N cycling on a chronosequence of marine terraces in Santa Cruz, California, where I investigated the impact of landscape age. I propose that two factors account for this apparent greater redox sensitivity of S compared to N isotopes. First, S is in less biological demand, and thus more readily fractionated by redox reactions, unlike N, which might be fully consumed for plant and microbial cellular metabolism during biological processes. Second, S may experience several reduction-reoxidation cycles due to its retention in soils via adsorption on iron and aluminum oxides, unlike N, which is easily lost from soils once reduced to gaseous form. In the deeper soil layers, processes that deplete the heavy S isotope (such as DBSR) dominated in the youngest soils, while processes that enrich the soil in the heavy isotope (such as mineralization) dominated in the older soils. Furthermore, pore water data revealed a division in soil processes with depth in the older soils, with large fluctuations in sulfate concentration and isotope fractionation near the surface (likely due to DBSR), but little change below the well-developed argillic horizons. My data showed no significant effect of phosphorus limitation on S cycling in the older soils. Rather, age impacted soil S content and δ34S values mostly due to changes in hydrology, including the development of a water restrictive argillic horizon, with increasing soil age.In summary, my results showed that, of the factors examined, rainfall effects modified by landform characteristics are the most important controls on S biogeochemistry that dictate the types and rates of processes. S cycling should, therefore, most directly respond to the changes in rainfall predicted to occur due to global change. Specifically, a significant decrease in rainfall in many regions may reduce soil S content and the extent of its biological cycling

First-principles study of OH defects in zircon

The infrared spectroscopic properties of selected OH defects in zircon are investigated by first-principles calculations. The explicit treatment of the coupled nature of OH motions in the stretching modes, together with the calculation of the intensity and polarization of absorption bands, makes it possible to directly compare theoretical and experimental data. The bands observed at 3,420 cm(-1) (polarization parallel to c axis) and 3,385 cm(-1) (polarization perpendicular to c axis) in natural and synthetic samples correspond to the IR-active vibrational modes of the hydrozircon defect, that is, fully protonated Si vacancy. The broad band observed at 3,515 cm(-1) in the spectrum of zircon crystals grown in F-rich environments is consistent with the occurrence of composite (OH,F) tetrahedral defects. Calculations also show that the band observed at 3,200 cm(-1) in the spectrum of synthetic undoped samples can be ascribed to fully protonated Zr vacancies. The theoretical values of integrated absorption coefficients indicate that general correlations can be reasonably used to determine the concentration of OH groups in zircon

Theoretical study of OH-defects in pure enstatite

The infrared spectroscopic properties of selected defects in orthoenstatite are investigated by first-principles calculations. The considered defects include doubly protonated Mg vacancies at M1 and M2 sites, fully protonated SiA and SiB vacancies (hydrogarnet defects), and doubly protonated SiA and SiB vacancies associated with interstitial Mg2+ cations. The bands observed at 3,070 and 3,360 cm(-1) in the spectrum of synthetic enstatite samples are ascribed to O2A-H and O2B-H groups, respectively, associated with M2 vacancies. The theoretical models suggest that bands observed at 3,590 and 3,690 cm(-1) in the spectrum of enstatite samples synthesized under low silica-activity conditions correspond to O2H and O1H groups associated with SiB vacancies partially compensated by interstitial Mg2+ cations in fivefold coordination. The theoretical relation between the integrated absorption coefficient of OH-defects and vibrational frequencies is consistent with previous observations indicating that the absorption coefficients of OH-defects are comparatively stronger in enstatite than in the olivine polymorphs