| 11. |
- Kim, Ji-Hoon, et al.
(author)
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A Pulse of Meteoric Subsurface Fluid Discharging Into the Chukchi Sea During the Early Holocene Thermal Maximum (EHTM)
- 2021
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In: Geochemistry Geophysics Geosystems. - 1525-2027. ; 22:8
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Journal article (peer-reviewed)abstract
- The response of Arctic Ocean biogeochemistry to subsurface flow driven by permafrost thaw is poorly understood. We present dissolved chloride and water isotopic data from the Chukchi Sea Shelf sediments that reveal the presence of a meteoric subsurface flow enriched in cations with a radiogenic Sr fingerprint. This subsurface fluid is also enriched in dissolved inorganic carbon and methane that bear isotopic compositions indicative of a carbon reservoir modified by reactions in a closed system. Such fluid characteristics are in stark contrast with those from other sites in the Chukchi Sea where the pore water composition shows no sign of meteoric input, but reflect typical biogeochemical reactions associated with early diagenetic sequences in marine sediment. The most likely source of the observed subsurface flow at the Chukchi Sea Shelf is from the degradation of permafrost that had extended to the shelf region during the Last Glacial Maximum. Our data suggest that the permafrost-driven subsurface flow most likely took place during the 2-3 degrees C warming in the Early Holocene Thermal Maximum. This time scale is supported by numerical simulation of pore water profiles, which indicate that a minimum of several thousand years must have passed since the cessation of the subsurface methane-bearing fluid flow.
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| 12. |
- Kim, Ji-Hoon, et al.
(author)
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Assessing the impact of freshwater discharge on the fluid chemistry in the Svalbard fjords
- 2022
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In: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 835
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Journal article (peer-reviewed)abstract
- Changes in the cryosphere extent (e.g., glacier, ice sheet, permafrost, and snow) have been speculated to impact (bio)geochemical interactions and element budgets of seawater and pore fluids in Arctic regions. However, this process has rarely been documented in Arctic fjords, which leads to a poor systematic understanding of land-ocean interactions in such a warming-susceptible region. Here, we present the chemical and isotopic (δ18O, δD, δ11B, and 87Sr/86Sr) compositions of seawater and pore fluids from five fjords in the Svalbard archipelago. Compared to bottom seawater, the low Cl− concentrations and depleted water isotopic signatures (δ18O and δD) of surface seawater and pore fluids delineate freshwater discharge originating from precipitation and/or meltwater of the cryosphere (i.e., glacier, snow, and permafrost). In contrast, the high Cl− concentrations with light water isotopic values in pore fluids from Dicksonfjorden indicate a brine probably resulted from submarine permafrost formation during the late Holocene, a timing supported by the numerical simulation of dissolved Cl− concentration.The freshwater is influenced by the local diagenetic processes such as ion exchanges indicated by δ11B signatures as well as interactions with bedrock during fluid migration inferred from pore fluid 87Sr/86Sr ratios. The interactions with bedrock significantly alter the hydrogeochemical properties of pore fluids in each fjord, yielding spatiotemporal variations. Consequently, land-ocean interactions in combination with the hydrosphere-cryosphere-lithosphere are critical factors for understanding and predicting the hydrology and elemental cycling during global climate change periods in the past, present, and future of the Svalbard archipelago.
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| 13. |
- Park, Hee-Sung, et al.
(author)
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Design and evolution of new catalytic activity with an existing protein scaffold.
- 2006
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In: Science. - 1095-9203. ; 311:5760, s. 535-8
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Journal article (peer-reviewed)abstract
- The design of enzymes with new functions and properties has long been a goal in protein engineering. Here, we report a strategy to change the catalytic activity of an existing protein scaffold. This was achieved by simultaneous incorporation and adjustment of functional elements through insertion, deletion, and substitution of several active site loops, followed by point mutations to fine-tune the activity. Using this approach, we were able to introduce beta-lactamase activity into the alphabeta/betaalpha metallohydrolase scaffold of glyoxalase II. The resulting enzyme, evMBL8 (evolved metallo beta-lactamase 8), completely lost its original activity and, instead, catalyzed the hydrolysis of cefotaxime with a (kcat/Km)app of 1.8 x 10(2) (mole/liter)(-1) second(-1), thus increasing resistance to Escherichia coli growth on cefotaxime by a factor of about 100.
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| 14. |
- Park, Ji-Won, et al.
(author)
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Beetle Immunity
- 2010
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In: Advances in Experimental Medicine and Biology. - Boston, MA : Springer US. - 0065-2598 .- 2214-8019. ; 708, s. 163-180
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Journal article (peer-reviewed)abstract
- Genetic studies have elegantly characterized the innate immune response in Drosophila melanogaster. However, these studies have a limited ability to reveal the biochemical mechanisms underlying the innate immune response. To investigate the biochemical basis of how insects recognize invading microbes and how these recognition signals activate the innate immune response, it is necessary to use insects, from which larger amounts of hemolymph can be extracted. Using the larvae from two species of beetle, Tenebrio molitor and Holotrichia diomphalia, we elucidated the mechanisms underlying pathogenic microbe recognition. In addition, we studied the mechanism of host defense molecule amplification. In particular, we identified several pattern recognition proteins, serine proteases, serpins and antimicrobial peptides and examined how these molecules affect innate immunity.
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| 15. |
- Roh, Kyung-Baeg, et al.
(author)
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Proteolytic cascade for the activation of the insect toll pathway induced by the fungal cell wall component
- 2009
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In: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 284:29, s. 19474-19481
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Journal article (peer-reviewed)abstract
- The insect Toll signaling pathway is activated upon recognition of Gram-positive bacteria and fungi, resulting in the expression of antimicrobial peptides via NF-kappaB-like transcription factor. This activation is mediated by a serine protease cascade leading to the processing of Spätzle, which generates the functional ligand of the Toll receptor. Recently, we identified three serine proteases mediating Toll pathway activation induced by lysine-type peptidoglycan of Gram-positive bacteria. However, the identities of the downstream serine protease components of Gram-negative-binding protein 3 (GNBP3), a receptor for a major cell wall component beta-1,3-glucan of fungi, and their order of activation have not been characterized yet. Here, we identified three serine proteases that are required for Toll activation by beta-1,3-glucan in the larvae of a large beetle, Tenebrio molitor. The first one is a modular serine protease functioning immediately downstream of GNBP3 that proteolytically activates the second one, a Spätzle-processing enzyme-activating enzyme that in turn activates the third serine protease, a Spätzle-processing enzyme. The active form of Spätzle-processing enzyme then cleaves Spätzle into the processed Spätzle as Toll ligand. In addition, we show that injection of beta-1,3-glucan into Tenebrio larvae induces production of two antimicrobial peptides, Tenecin 1 and Tenecin 2, which are also inducible by injection of the active form of Spätzle-processing enzyme-activating enzyme or processed Spätzle. These results demonstrate a three-step proteolytic cascade essential for the Toll pathway activation by fungal beta-1,3-glucan in Tenebrio larvae, which is shared with lysine-type peptidoglycan-induced Toll pathway activation.
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