Interaction mechanism between low molecular weight chitosan nanofilm and functionalized surfaces in aqueous solutions

Low-molecular-weight chitosan (LMW chitosan, <10 kDa) have a significant potential for biomedical applications (e.g., antimicrobial and gene/drug delivery) because of their higher water solubility at pH values ranging from 3.0 to 8.5, compared to that of the high-molecular-weight (>100 kDa) chitosan. A comprehensive understanding of the LMW interaction mechanism with specific functional groups is necessary to predict their binding efficiency to other molecules for effectively utilizing their potential within biological systems. In this study, we used a surface forces apparatus (SFA) to investigate molecular interactions between LMW chitosan and four different functionalized self-assembled monolayers (SAMs) in aqueous solutions at pH values of 3.0, 6.5, and 8.5. Chitosan exhibited the strongest interaction energy with methyl-terminated SAM (CH3-SAM), indicating the significance of hydrophobic interaction. Many chitin/chitosan fibers in nature bind polyphenols (e.g., eumelanin) to form robust composites, which can be attributed to the strong attraction between chitosan and phenyl-SAM, presumably caused by cation????? interactions. These findings demonstrate the potential of modulating the magnitude of the interaction energy by controlling the solution pH and types of targeted functional groups to realize the optimal design of chitosan-based hybrid composites with other biomolecules or synthetic materials

Sequence variability and expression pattern of the dehydrin gene family in “Populus tremula” x “Populus alba var. glandulosa.” Plant Omics 5

Abstract The dehydrin (Dhn) genes occur as multi-gene families in the plant genome and are suggested to play a protective role in cold and drought tolerance. Here, we have identified 10 unique dehydrin genes (PoDhn) from poplar (Populus alba × P. tremula var. glandulosa), 6 of which have the full ORF. The PoDhn1 encodes for SK 2 -type, PoDhn2 and PoDhn7 for Kn-type, PoDhn3 for K 3 Stype, and PoDhn5 and PoDhn6 for the Y 3 SKn-type dehydrins, respectively. Results of gene expression analysis demonstrated that most of the PoDhn genes were expressed under normal growth conditions and the transcription level of the PoDhns increased by abiotic stress treatment. In particular, PoDhn2 and PoDhn7 transcripts increased dramatically by both cold and drought treatment and PoDhn5 was up-regulated by only drought stress. These results may be useful in further studies of PoDhn genes, including investigations into the mechanisms underlying gene expression, the nature of their variation, and their physiological functions

Development of Poly(methyl methacrylate)-Based Copolymers with Improved Heat Resistance and Reduced Moisture Absorption

Poly(methyl methacrylate) (PMMA) is widely used as a transparent material for optical applications, owing to its high light transmittance. However, it exhibits poor heat resistance and high moisture absorption, leading to distortion and deformation upon exposure to elevated temperatures and/or moisture. These structural changes decrease the transparency of PMMA, critically limiting its applicability. In this study, we synthesized poly(methyl methacrylate-co-styrene-co-acrylamide) (PMSAm) as a reference polymer and introduced one of four different comonomers [N-phenylmaleimide (PMI), N-cyclohexylmaleimide (CHMI), allyltrimethylsilane (ATMS), or 2,2,2-trifluoroethyl methacrylate (TF)] as a means to improve heat resistance and reduce moisture absorption. Four series of PMMA-based random copolymers (PMSAm???PMI, PMSAm???CHMI, PMSAm???ATMS, and PMSAm???TF) were synthesized by conventional thermal radical polymerization. All of the polymers synthesized exhibited improved heat resistance, with PMSAm???CHMI exhibiting the highest glass transition temperature (Tg = 122.54 ??C) and 5% weight loss thermal decomposition temperature (T5d = 343.40 ??C) as well as the lowest thermal expansion coefficient (90.3 ??m m???1 ??C???1). The highest hydrophobicity was exhibited by PMSAm???TF, with a water contact angle of 78.9??, indicating higher hydrophobicity compared to that of pure PMMA (69.4??). More importantly, high transparency (???90%) was exhibited by all of the synthesized polymers. Thus, our copolymerization strategy successfully addresses the limitations, i.e., low heat resistance and high moisture absorption, of conventional PMMA-based materials