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Development and Evaluation of a Ground CO2 Measurement System

Mon, 01 Dec 2025 00:00:00 GMT

Title: Development and Evaluation of a Ground CO2 Measurement System Authors: Park, Keunbo Abstract: 지구 평균 기온 상승은 산업화 이후 증가한 온실가스 배출과 밀접한 관련이 있으며, 특히 고위도 지역의 영구동토층 해빙은 저장된 유기탄소의 대기 방출을 통해 지구가열화를 가속할 잠재성이 크다. 이에 따라 동토？대기 경계면에서 발생하는 CO2 교환 특성을 정량적으로 규명하기 위한 정밀 현장 관측 기술의 필요성이 증대되고 있다. 본 연구에서는 이러한 과학적·정책적 요구에 대응하여 비분산적외선(NDIR) 분광 원리를 기반으로 한 정밀 CO2 측정시스템을 설계·제작하였다. 측정 시스템은 MCU 기반 제어기, 실시간 보정 알고리즘, 통신 모듈 및 GUI 기반 시각화 시스템을 통합하여 안정적으로 운용 가능하도록 구현하였다. 개발된 측정 시스템은 표준가스를 이용한 영점 및 스팬 교정 기능을 포함하며, 이동평균 및 적응형 필터 기반 신호 처리, 비정상 신호 제거 알고리즘, 실시간 데이터 로깅 기능을 적용하였다. 성능 검증은 0.600 ppm, 429.860 ppm, 953.550 ppm의 CO2 표준가스를 이용해 정확도, 정밀도, 응답시간, 선형성 및 영점 안정성을 평가하는 방식으로 수행하였다. 실험 결과, 모든 농도 구간에서 측정값은 표준가스 농도와 일치하는 수준을 유지하였으며, 정확도 ±1% 이내, 정밀도 0.560 이하, 장기 영점 드리프트를 포함하여 상용되고 있는 정밀 측정 시스템(LI-COR LI-7810)와 동등한 성능을 확보하였다. 또한 1:1 비교 분석에서 두 장비의 측정값은 높은 상관성을 보이며 우수한 선형성을 나타냈다.

A CALB-like Cold-Active Lipolytic Enzyme from Pseudonocardia antarctica: Expression, Biochemical Characterization, and AlphaFold-Guided Dynamics

Mon, 01 Dec 2025 00:00:00 GMT

Title: A CALB-like Cold-Active Lipolytic Enzyme from Pseudonocardia antarctica: Expression, Biochemical Characterization, and AlphaFold-Guided Dynamics Authors: Liu Lixiao; Do, Hackwon; Kim Jong-Oh; Lee, Jun Hyuck; Kim Hak Jun Abstract: Cold-active lipolytic enzymes enable low-temperature biocatalysis, but remain underexplored in Antarctic actinomycetes. Here, we report the discovery and first-step characterization of a CALB-like cold-active lipolytic enzyme (PanLip) from Pseudonocardia antarctica. Sequence and structure analyses revealed a canonical alpha/beta-hydrolase fold with a conserved Ser-Asp-His triad and short helical elements around the pocket reminiscent of CALB's alpha 5/alpha 10 lid. Mature PanLip was expressed primarily as inclusion bodies in E. coli; an N-terminally truncation (PanLip Delta N) improved solubility and PanLip Delta N was purified by Ni-NTA. Far-UV CD confirmed a folded alpha/beta architecture. PanLip Delta N favored short-chain substrates (p-NPA, kcat/KM = 2.4 x 105 M-1s-1) but also showed measurable hydrolytic activity toward natural triglycerides, consistently with a lipase-family esterase. The enzyme showed an activity optimum near 25 degrees C and pH 8.0. The enzyme tolerated low salt (maximal at 0.1 M NaCl), mild glycerol, and selected organic solvents (notably n-hexane), but was inhibited by high salt, Triton X-100, and SDS. AlphaFold predicted high local confidence for the catalytic core; DALI placed PanLip closest to fungal lipases (AFLB/CALB). Temperature-series MD and CABS-flex indicated enhanced surface breathing and flexible segments adjacent to the active site-including a region topologically matching CALB alpha 10-supporting a flexibility-assisted access mechanism at low temperature. Structure-based MSAs did not support a cold adaptation role for the reported VDLPGRS motif. Taken together, these findings position PanLip as a promising cold-active catalyst with CALB-like access control and potential for low-temperature biocatalysis.

Exogenous abscisic acid enhances freeze-thaw stress tolerance in Antarctic moss Sanionia uncinata through coordinated antioxidant defense and osmoprotectant accumulation

Mon, 01 Dec 2025 00:00:00 GMT

Title: Exogenous abscisic acid enhances freeze-thaw stress tolerance in Antarctic moss Sanionia uncinata through coordinated antioxidant defense and osmoprotectant accumulation Authors: Seo, Suyeon; Ahn, Yong-Yoon; Kim, Kitae; Lee, Jun Hyuck; Min, Kyungwon; Lee, Hyoungseok Abstract: Abscisic acid (ABA) is known to improve plant freeze-thaw stress tolerance (FTST), but its role in Antarctic mosses remains largely unexplored. Accordingly, this study investigated the effects of exogenous ABA application on FTST of gametophore Sanionia uncinata, one of the most widespread moss species in maritime Antarctica. Samples were treated with 10 mu M ABA for 72 h under controlled culture conditions, then subjected to freezing stress at -13 and -16 degrees C. Various physiological parameters were measured to assess ABA-induced FTST, including ion-leakage, photosynthetic efficiency (Fv/Fm), malondialdehyde (MDA) content, compatible solutes/osmolytes (proline and total sugars), and antioxidant enzyme activities, e.g., superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX). Gametophores treated with ABA efficiently assimilated ABA, evident by similar to 20-fold higher than controls. ABA application did not impede gametophore growth but slightly increased dry weight/fresh weight ratio (5 % increase). ABA significantly improved freezing tolerance, reducing freeze-induced membrane injury by similar to 20 % at both stress temperatures, alleviating oxidative stress with 25-34 % lower MDA accumulation, and enhancing PSII maximum quantum yield (Fv/Fm) by 6-7 % following freeze-thaw stress. Improved FTST was paralleled by enhanced activities of antioxidant enzymes, CAT and APX increasing by similar to 11 % and 56 %, respectively, while SOD remained unchanged. ABA treatment also promoted osmoprotectant accumulation, with proline content increasing by 33.5 % and total soluble sugars nearly doubling (99 % increase). These findings provide the first quantitative evidence that exogenous ABA markedly improves FTST in an Antarctic moss through coordinated antioxidant defense and osmoprotectant accumulation, highlighting ABA as a critical regulator of stress resilience in S. uncinata.

Regulation of anti-CRISPR operons by structurally distinct families of Aca proteins

Sat, 01 Nov 2025 00:00:00 GMT

Title: Regulation of anti-CRISPR operons by structurally distinct families of Aca proteins Authors: So Yeon Lee; Nils Birkholz; Lee, Jun Hyuck; Peter C. Fineran; Hyun Ho Park Abstract: CRISPR-Cas systems provide bacteria with adaptive immunity against bacteriophages and mobile genetic elements, driving an evolutionary arms race in which phages deploy anti-CRISPR (Acr) proteins. Acr proteins are often co-encoded in operons with anti-CRISPR-associated (Aca) proteins, which coordinate the regulation of acr gene expression. Here, we reveal the molecular basis of DNA binding that mediates transcriptional repression by two distinct Aca family members: Aca7 and Aca11. Crystal structures of Aca7 and Aca11 highlight conserved helix-turn-helix (HTH) motifs within α-helix bundles, providing a universal DNA-binding platform. Aca7 forms a symmetrical dimer to recognize a 19-bp inverted repeat (IR) within the acrIF11-aca7 operon. Strikingly, Aca11 binds 22-bp IRs in two distinct promoters, suggesting that Aca proteins can control multiple target operons. Mutagenesis and electrophoretic mobility shift assays (EMSAs) confirm that dimerization and sequence-specific IR recognition are essential for DNA binding. Despite mechanistic similarities, these and other Aca proteins exhibit notable differences. Structural comparisons across Aca families reveal that while monomer structures are generally similar with conserved HTH motifs, the structures of their dimeric functional units vary significantly. These structural differences might be essential for Aca proteins to bind to various promoters and regulate the expression of different Acr proteins.