Applications of Green Chemistry in Asymmetric Transfer Hydrogenation and Chiral Separations

Green chemistry has been applied to all aspects of the life cycle of chemically related products, including design, usage, manufacturing, analysis, and disposal. In this thesis, I focus on the green chemistry applications in organic synthesis and analytical chemistry. More specifically, allylic and chiral alcohols are abundant in natural sources such as in essential oils, and widely utilized as starting materials. They are also major components in food, fragrance, biocides and the pharmaceutical compounds. In this thesis, I report the first Ru-catalysed asymmetric transfer hydrogenation (ATH) of prochiral allylic alcohols. This reaction provides chiral secondary alcohols in excellent enantioselectivities and yield. This new reaction is much safer, more economical and environmentally friendly for the asymmetric reduction of allylic alcohols compared to the high-pressure gaseous hydrogenations. Mechanistic studies through a series of deuterium-labeled experiments provided a new mechanism for the ATH reaction. Specifically, a tandem enantioselective isomerization-transfer hydrogenation process occurs. The asymmetric induction step occurs during the Ru-assisted 1,3-hydrogen shift isomerization through an enal intermediate prior to transfer hydrogenation. Reaction conditions were optimized using chiral ruthenium complexes. The thermodynamic characteristics of the enantioseparation of the chiral benzyl alcohols under ACN-free RP-HPLC were also investigated. The enantiomers of various benzyl alcohols were separated on derivatized cellulose and amylose chiral stationary phases with methanol/water or ethanol/water as mobile phases. Enantioseparation was optimized by varying the percentage of organic modifier and column temperature. Baseline resolution was achieved in 10 min of elution time for most of the selected enantiomers. The effects of the mobile phase composition, column temperature and structural moieties of α-substituents on the enantioseparation were investigated. For all enantiomeric pairs, the experimental van’t Hoff plots (ln k\u27 vs 1/T and ln α vs 1/T) of each mobile phase/stationary phase set were linear in the temperature range between 10 to 40 oC. The corresponding thermodynamic parameters were then calculated. Our studies indicate that chiral separation of benzyl alcohols is controlled by enthalpy. However, bi-aromatic benzyl alcohols showed greater selectivities at higher temperature, indicating that the chiral recognition process is entropy-driven. A linear relationship between changes in enthalpy and entropy, also known as entropy-enthalpy compensation, was observed for all analytes in a wide range of mobile phases. This resulted in relatively constant enantioselectivities under various mobile phase eluting strengths

How to survive in the world’s third poplar: Insights from the genome of the highest altitude woody plant, Hippophae tibetana (Elaeagnaceae)

Hippophae tibetana (Tibetan sea-buckthorn) is one of the highest distributed woody plants in the world (3,000-5,200 meters a.s.l.). It is characterized by adaptation to extreme environment and important economic values. Here, we combined PacBio Hifi platform and Hi-C technology to assemble a 1,452.75 Mb genome encoding 33,367 genes with a Contig N50 of 74.31 Mb, and inferred its sexual chromosome. Two Hippophae-specific whole-genome duplication events (18.7-21.2 million years ago, Ma; 28.6-32.4 Ma) and long terminal repeats retroelements (LTR-RTs) amplifications were detected. Comparing with related species at lower altitude, Ziziphus jujuba (<1, 700 meters a.s.l.), H. tibetana had some significantly rapid evolving genes involved in adaptation to high altitude habitats. However, comparing with Hippophae rhamnoides (<3, 700 meters a.s.l.), no rapid evolving genes were found except microtubule and microtubule-based process genes, H. tibetana has a larger genome, with extra 2, 503 genes (7.5%) and extra 680.46 Mb transposable elements (TEs) (46.84%). These results suggest that the changes in the copy number and regulatory pattern of genes play a more important role for H. tibetana adapting to more extreme and variable environments at higher altitude by more TEs and more genes increasing genome variability and expression plasticity. This suggestion was supported by two findings: nitrogen-fixing genes of H. tibetana having more copies, and intact TEs being significantly closer genes than fragmentary TEs. This study provided new insights into the evolution of alpine plants

Complete mitochondrial genome of Hippophae tibetana: insights into adaptation to high-altitude environments

Hippophae tibetana, belonging to the Elaeagnaceae family, is an endemic plant species of the Qinghai–Tibet Plateau, valued for its remarkable ecological restoration capabilities, as well as medicinal and edible properties. Despite being acknowledged as a useful species, its mitochondrial genome data and those of other species of the Elaeagnaceae family are lacking to date. In this study, we, for the first time, successfully assembled the mitochondrial genome of H. tibetana, which is 464,208 bp long and comprises 31 tRNA genes, 3 rRNA genes, 37 protein-coding genes, and 3 pseudogenes. Analysis of the genome revealed a high copy number of the trnM-CAT gene and a high prevalence of repetitive sequences, both of which likely contribute to genome rearrangement and adaptive evolution. Through nucleotide diversity and codon usage bias analyses, we identified specific genes that are crucial for adaptation to high-altitude conditions. Notably, genes such as atp6, ccmB, nad4L, and nad7 exhibited signs of positive selection, indicating the presence of unique adaptive traits for survival in extreme environments. Phylogenetic analysis confirmed the close relationship between the Elaeagnaceae family and other related families, whereas intergenomic sequence transfer analysis revealed a substantial presence of homologous fragments among the mitochondrial, chloroplast, and whole genomes, which may be linked to the high-altitude adaptation mechanisms of H. tibetana. The findings of this study not only enrich our knowledge of H. tibetana molecular biology but also advance our understanding of the adaptive evolution of plants on the Qinghai–Tibet Plateau. This study provides a solid scientific foundation for the molecular breeding, conservation, and utilization of H. tibetana genetic resources

Self-similar Based Time Series Analysis and Prediction

Fractals have been observed in many natural phenomena, and self-similarity is the most important statistical property of fractals. In the literature, the concepts of self-similarity and long-range-dependence (LRD), the increment process of a self-similar signal when the Hurst parameter is between 0.5 and 1, are often confused. On the other hand, the forecasting of many real-life signals exhibiting these properties is useful yet remains challenging. The objective of this thesis is to provide the readers with a clear and detailed explanation of the relevant concepts, and then to compare forecasting models (including FARIMA, HAR-RV, wavelet-based and average-VAR) for self-similar and LRD signals via real-life data (arterial blood pressure signals and volatility indexes). Numerical studies show that the four models perform similarly, while the FARIMA model is not recommended due to its time-consuming computation; and the performance of detecting large decrease is more accurate than that of detecting large increase.M.A.S

Characterization of the complete chloroplast genome of Hippophae salicifolia D. Don (Elaeagnaceae)

Seabuckthorn (Hippophae L.) is a pioneer species widely distributed in Eurasia. We assembled and annotated the chloroplast genome of Hippophae salicifolia from Illumina pair-end data, which was 155,420 bp in length with 36.74% GC content; this plastome featured a quadripartite structure with two copies of a large inverted repeat (IR) of 26,528 bp separated by large single copy (LSC) region of 83,504 bp and small single copy region (SSC) of 18,860 bp. In total, 131 complete genes were annotated, including 38 tRNA, eight rRNA, and 85 protein-coding genes. Phylogenetic analysis recovered H. salicifolia and H. gyantsensis as monophyletic and sister to all other Hippophae species for which complete plastome sequences have been published

Metallothionein: A Comprehensive Review of Its Classification, Structure, Biological Functions, and Applications

Metallothionein is a cysteine-rich protein with a high metal content that is widely found in nature. In addition to heavy metal detoxification, metallothionein is well known as a potent antioxidant. The high sulfhydryl content of metallothionein confers excellent antioxidant activity, enabling it to effectively scavenge free radicals and mitigate oxidative stress damage. In addition, metallothionein can play a neuroprotective role by alleviating oxidative damage in nerve cells, have an anticancer effect by enhancing the ability of normal cells to resist unfavorable conditions through its antioxidant function, and reduce inflammation by scavenging reactive oxygen species. Due to its diverse biological functions, metallothionein has a broad potential for application in alleviating environmental heavy metal pollution, predicting and diagnosing diseases, and developing skin care products and health foods. This review summarizes the recent advances in the classification, structure, biological functions, and applications of metallothionein, focusing on its powerful antioxidant effects and related functions

Imperfections of Scalar Approximation in Calibration of Computer-Generated Holograms for Optical Surface Measurements

Computer-generated hologram (CGH) null correctors are used as accuracy standards for interferometric measurements of optical surfaces and optical systems. Diffractive optics calibrators (DOCs) have been developed to evaluate the phase tolerance of CGHs based on scalar approximation by measuring variations in duty cycle and etching depth. However, if the grating period of a CGH < 5λ, the scalar approximation is not accurate for phase analysis and reconstruction. In this study, the measurement errors of DOCs with small-period CGHs were investigated and experimentally verified. Results show that the imperfections of scalar approximation in CGHs cannot be ignored and the development of rigorous evaluation methods to improve the measurement accuracy of CGHs is of great practical significance

Genome-Wide Identification and Characterization of the Potato bHLH Transcription Factor Family

Plant basic/helix–loop–helix (bHLH) transcription factors participate in a number of biological processes, such as growth, development and abiotic stress responses. The bHLH family has been identified in many plants, and several bHLH transcription factors have been functionally characterized in Arabidopsis. However, no systematic identification of bHLH family members has been reported in potato (Solanum tuberosum). Here, 124 StbHLH genes were identified and named according to their chromosomal locations. The intron numbers varied from zero to seven. Most StbHLH proteins had the highly conserved intron phase 0, which accounted for 86.2% of the introns. According to the Neighbor-joining phylogenetic tree, 259 bHLH proteins acquired from Arabidopsis and potato were divided into 15 groups. All of the StbHLH genes were randomly distributed on 12 chromosomes, and 20 tandem duplicated genes and four pairs of duplicated gene segments were detected in the StbHLH family. The gene ontology (GO) analysis revealed that StbHLH mainly function in protein and DNA binding. Through the RNA-seq and quantitative real time PCR (qRT-PCR) analyses, StbHLH were found to be expressed in various tissues and to respond to abiotic stresses, including salt, drought and heat. StbHLH1, 41 and 60 were highly expressed in flower tissues, and were predicted to be involved in flower development by GO annotation. StbHLH45 was highly expressed in salt, drought and heat stress, which suggested its important role in abiotic stress response. The results provide comprehensive information for further analyses of the molecular functions of the StbHLH gene family

Genome-wide analysis of the potato Hsp20 gene family: identification, genomic organization and expression profiles in response to heat stress

Abstract Background Heat shock proteins (Hsps) are essential components in plant tolerance mechanism under various abiotic stresses. Hsp20 is the major family of heat shock proteins, but little of Hsp20 family is known in potato (Solanum tuberosum), which is an important vegetable crop that is thermosensitive. Results To reveal the mechanisms of potato Hsp20s coping with abiotic stresses, analyses of the potato Hsp20 gene family were conducted using bioinformatics-based methods. In total, 48 putative potato Hsp20 genes (StHsp20s) were identified and named according to their chromosomal locations. A sequence analysis revealed that most StHsp20 genes (89.6%) possessed no, or only one, intron. A phylogenetic analysis indicated that all of the StHsp20 genes, except 10, were grouped into 12 subfamilies. The 48 StHsp20 genes were randomly distributed on 12 chromosomes. Nineteen tandem duplicated StHsp20s and one pair of segmental duplicated genes (StHsp20-15 and StHsp20-48) were identified. A cis-element analysis inferred that StHsp20s, except for StHsp20-41, possessed at least one stress response cis-element. A heatmap of the StHsp20 gene family showed that the genes, except for StHsp20-2 and StHsp20-45, were expressed in various tissues and organs. Real-time quantitative PCR was used to detect the expression level of StHsp20 genes and demonstrated that the genes responded to multiple abiotic stresses, such as heat, salt or drought stress. The relative expression levels of 14 StHsp20 genes (StHsp20-4, 6, 7, 9, 20, 21, 33, 34, 35, 37, 41, 43, 44 and 46) were significantly up-regulated (more than 100-fold) under heat stress. Conclusions These results provide valuable information for clarifying the evolutionary relationship of the StHsp20 family and in aiding functional characterization of StHsp20 genes in further research