Kookmin University

As silicon-based transistors face fundamental scaling limits, the search for breakthrough alternatives has led to innovations in 3D architectures, heterogeneous integration, and sub-3 nm semiconductor body thicknesses. However, the true effectiveness of these advancements lies in the seamless integration of alternative semiconductors tailored for next-generation transistors. In this review, we highlight key advances that enhance both scalability and switching performance by leveraging emerging semiconductor materials. Among the most promising candidates are 2D van der Waals semiconductors, Mott insulators, and amorphous oxide semiconductors, which offer not only unique electrical properties but also low-power operation and high carrier mobility. Additionally, we explore the synergistic interactions between these novel semiconductors and advanced gate dielectrics, including high-K materials, ferroelectrics, and atomically thin hexagonal boron nitride layers. Beyond introducing these novel material configurations, we address critical challenges such as leakage current and long-term device reliability, which become increasingly crucial as transistors scale down to atomic dimensions. Through concrete examples showcasing the potential of these materials in transistors, we provide key insights into overcoming fundamental obstacles—such as device reliability, scaling down limitations, and extended applications in artificial intelligence—ultimately paving the way for the development of future transistor technologies.

The problem of arsenic contamination is widespread, posing serious risks to both human health and crop productivity. Therefore, eco-friendly strategies are urgently needed to reduce metal stress-related yield losses and minimize its impacts on human health. Although the roles of nitric oxide (NO) and indole-3-acetic acid (IAA) in combating abiotic stresses, including metal toxicity, have been reported, the mechanisms underlying their interaction remain unclear. This study investigates whether IAA and NO function through shared or independent signaling pathways in regulating arsenate [As(V)] toxicity in tomato seedlings. Results showed that As(V) stress reduced dry weight, increased arsenic and tannin accumulation, suppressed auxin transport, signaling, and IAA content, and disrupted internal root structures. As(V) also induced oxidative stress, reduced stomatal frequency, suppressed glutathione biosynthesis, nitrogen metabolism, and the ascorbate-glutathione cycle, ultimately causing membrane damage. Application of a NO scavenger [2-(4-carboxyphenyl)-4,4,5,5 tetramethylimidazoline-1-oxyl-3-oxide] did not exacerbate As(V) stress in the presence of IAA. In contrast, a polar auxin transport inhibitor [2,3,5-triiodobenzoic acid, TIBA] intensified As(V) toxicity even in the presence of NO. Interestingly, addition of IAA reversed the negative effects of TIBA, suggesting that IAA acts downstream of NO in a signaling pathway that mitigates As(V) toxicity. These findings are promising, as both IAA and NO are inexpensive and could be applied to manage As(V) stress in non-waterlogged arsenic-contaminated soils, where As(V) is the dominant arsenic species under field conditions. Furthermore, biochemical markers associated with As(V) tolerance could aid in developing arsenic-tolerant tomato cultivars using advanced molecular genetic tools, thereby ensuring food security and safety.

The site-specific methylation of (-)-epigallocatechin-3-O-gallate (EGCG), especially 3`` hydroxyl group in D-ring, significantly enhances its stability and bioavailability in human body. Therefore, the methylation is the way to make EGCG more orally active and potent nutraceutical agents. In this study, for the effective synthesis of the methylated EGCG, S-adenosyl-L-methionine dependent O-methyltransferase (OMT) was studied to synthesize the methylated EGCG. OMT from Bacillus licheniformis and B. megaterium were known to have methylation activity for EGCG. Because OMT from B. licheniformis (Bl_OMT) showed higher activity and regioselectivity between two OMTs, rational design was tried using Bl_OMT. F163W mutant of Bl_OMT showed 2-fold increased initial velocity for the methylation of EGCG than wild type Bl_OMT. This engineering result was further utilized as a basis for the identification of highly active OMT from sequence database. 100 homolog sequences of OMT of B. licheniformis and 100 homolog sequences of OMT of B. megaterium, were collected using BLAST. Multiple alignment of 202 sequences was used to generate subgroups. Four representative sequences from each subgroup were further studied. As a result, OMTs from Thermolongibacillus altinseunsis and B. subtilis, which were from homolog group of Bl_OMT, showed higher activity than Bl_OMT while showing the same high regioselectivity. OMTs from T. altinseunsis and B. subtilis showed k_cat/K_M of 17.4 M^-1s^-1 and 11.3 M^-1s^-1, respectively, while Bl_OMT showed 8.7 M^-1s^-1. Therefore, we could find that phenylalanine residue of the active site of OMT is very important to make strong binding of hydrophobic moiety of substrate and mutation to tryptophan is able to give higher binding strength.