Mahidol University's Institutional Repository
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Recent Submissions
Discovery and biochemical characterization of enzymes completing the 4-hydroxyphenylacetate pathway in Acinetobacter baumannii TH
(2025-12-01) Chinantuya W.; Kungchuai K.; Chaiyen P.; Maenpuen S.; Tinikul R.; Chinantuya W.; Mahidol University
A metabolic pathway for degrading 4-hydroxyphenylacetate (4-HPA) is crucial for environmental and pathogenic microbes to assimilate aromatic compounds. The 4-HPA degradation pathway in Acinetobacter baumannii TH comprises multiple reactions that are not fully understood. Enzymes involved in the first two steps (a two-component 4-HPA-3-hydroxylase, and 3,4-dihydroxyphenylacetate 2,3-dioxygenase) and the last two steps (4-hydroxy-2-keto-heptane-1,7-dioate aldolase and succinic semialdehyde (SSA) dehydrogenase (SSADH)) have been identified and studied, while the enzymes functioning in the middle of the pathway remain uncharacterized. Here, we identified products associated with individual enzymes including 5-carboxymethyl-2-hydroxymuconate-semialdehyde (CHMS) dehydrogenase (CHMSD), 5-carboxymethyl-2-hydroxymuconate (CHM) isomerase (CHMI), five-oxo-pent-3-ene-1,2,5-tricarboxylate (OPET) decarboxylase (OPETD), 2-hydroxy-hept-2,4-diene-1,7-dioate (HHDD) isomerase (HHDDI) and two-oxo-hept-3-ene-1,7-dioate (OHED) hydratase (OHEDH). We used enzymatically synthesized OPET (a tri-acid) to probe the decarboxylation step and found that the highest decarboxylation efficiency was achieved when OPETD, CHMI, and HHDDI were all present in the reaction. We demonstrated that CHMI was responsible for tri-acid tautomerization, while the protein-protein interactions between OPETD and HHDDI enhanced the decarboxylation by OPETD to generate OHED (a di-acid). OHEDH is distinct from other hydratases in that it requires Mn2+ as a cofactor. Notably, besides CHMS, CHMSD can use SSA, a substrate of SSADH, suggesting that CHMSD can substitute for SSADH to generate succinate for cellular utilization. Our studies herein completely assigned the catalytic functions of all enzymes in the 4-HPA degradation pathway. The knowledge gained will be valuable for developing inhibitors targeting enzymes unique to pathogenic microbes or for constructing cascade reactions to convert lignin-derived compounds into valuable biochemicals.
Validity and Practicality of Web-Based Self-Study Learning Platform to Improve Students’ English Proficiency
(2025-09-30) Fitrawati; Tiarina Y.; Amri Z.; Perrodin D.D.; Fitrawati; Mahidol University
This article examines the validity and practicality of the web-based self-study learning platform for English proficiency developed by the English Department of Universitas Negeri Padang. It explores the conversion of the platform into selected online booklets and the requirement for students to respond to exercise questions, receiving automated feedback within a short period to improve their English skills. A descriptive quantitative research design was employed to conduct this study, which involved administering questionnaires to 18 content and technical professionals and 177 students to assess the feasibility and value of the proposed platform. The results of the study indicate that the identified platform is a highly valid platform, not only from the perspective of content, pedagogy, and self-study, but also from the technical perspective. In addition, it is very practical in terms of usability, accessibility, adaptability, feedback, and cost. The current study demonstrates that the module can help university students engage in independent learning and enhance their English language skills when easily accessible, comprehensive, and versatile tools are utilised. These results ultimately demonstrate that the web-based learning platform can be effectively applied to self-regulating learning and cognitive development of the necessary language skills. Future research would need to explore the effects of performance and flexibility on university students in other areas more deeply. At the same time, the study reveals the direction of future development of the web-based learning environment as a means of intensifying possibilities for implementing conventional learning methods within an educational organisation.
Cultural Nuances in Romantic Stress: Psychometric Properties of the Thai Romantic Relationship Stress Scale (Thai-RRSS)
(2025-01-01) Puranachaikere T.; Thana-udom K.; Ratta-arpa W.; Kooptiwoot S.; Sa-nguanpanich N.; Sher T.G.; Puranachaikere T.; Mahidol University
Romantic relationship stress significantly impacts individual and dyadic well-being. This study aimed to validate the Romantic Relationship Stress Scale (RRSS) for use in Thailand (Thai-RRSS). A sample of 367 Thai adults (94% female; Mean age = 40.90) completed the measure. We examined its factor structure using Exploratory (EFA) and Confirmatory Factor Analysis (CFA). EFA revealed a three-factor structure: Stressful Events, Relational Negativity, and Relational Positivity. The overall scale demonstrated excellent internal consistency (Cronbach’s α = 0.94), with subscale alphas of 0.93, 0.85, and 0.66, respectively. CFA confirmed an adequate fit for both the original and the Thai EFA-derived models, with the latter showing slightly superior fit indices (χ2(374) = 1035.71, CFI = 0.933 vs. original: χ2(374) = 1210.29, CFI = 0.928). External validity was supported by strong negative correlations with Couple Satisfaction Index-4 (r = − 0.70 to − 0.48, p <.001). The findings suggest that the Thai-RRSS is a reliable and valid instrument for measuring relationship stress in Thailand. However, lower factor loadings on certain items suggest cultural nuances— such as the prioritization of relational harmony, conflict avoidance, and family involvement—influence the interpretation of stress, offering important considerations for future cultural adaptations.
EnNRJ Vol. 12 No. 2
(2014)
EnNRJ Vol. 15 No. 1
(2016)