Study of additions of disilanes to acetylenes and their applications in organic and polymer synthesis

Three separate studies are included in this dissertation;The first section of this thesis addresses the discovery of the trans-addition of disilanes to acetylenes. The reaction was performed with the 5,5,6,6-tetramethyl-3,3,8,8-tetraphenyl-4,7-dioxa-5,6-disila-cyclooctayne (1) under argon flow at 600°C to give 1,1,4,4-tetramethyl-3,3,6, 6-tetraphenyl-2,5-dioxa-1,4-disila-dicyclo (3,3,0) octa-7-ene (2). Ab initio calculations with MP4/6-31G** were carried out to find the transition state structure. The activation energy was determined to be 34 kcal/mol. It was found that the intramolecular trans-addition of disilane to acetylene also occurred photochemically when the acetylene is conjugated with an aromatic group;The second section of this thesis involves the synthesis of a novel, blue light-emitting molecules containing the 3,3,3\u27,3\u27-tetramethyl-3,3 \u27-disila-indeno (2,1-a) indene unit were synthesized with our recently discovered intramolecular addition of disilanes to acetylenes. Light-emitting diodes (LEDs) were fabricated by vapor deposition. The chromophore was also incorporated into polysiloxanes and polymethacrylate as pendent groups. Due to their high chemical stabilies and quantum yields, these polymers are excellent candidates for fabrication of polymer-based blue-light LEDs;The last section deals with the synthesis of a 2-silaoxetane molecule by the catalytic intramolecular addition of disilane to acetylene. The stability of the molecule was studied thermochemically and photochemically. The activation energy of decomposition of the 2-silaoxetane was found to be about 49.24 kcal/mol and Log(A) was 15.37. This process was also studied by ab initio calculations which showed that the decomposition was a highly non-synchronized but concerned process. The four-membered ring system expanded to a five-membered ring photochemically

Single crystal of a one-dimensional metallo-covalent organic framework.

Although polymers have been studied for well over a century, there are few examples of covalently linked polymer crystals synthesised directly from solution. One-dimensional (1D) covalent polymers that are packed into a framework structure can be viewed as a 1D covalent organic framework (COF), but making a single crystal of this has been elusive. Herein, by combining labile metal coordination and dynamic covalent chemistry, we discover a strategy to synthesise single-crystal metallo-COFs under solvothermal conditions. The single-crystal structure is rigorously solved using single-crystal electron diffraction technique. The non-centrosymmetric metallo-COF allows second harmonic generation. Due to the presence of syntactic pendant amine groups along the polymer chains, the metallopolymer crystal can be further cross-linked into a crystalline woven network

TNFRSF1B +676 T>G polymorphism predicts survival of non-Small cell lung cancer patients treated with chemoradiotherapy

<p>Abstract</p> <p>Background</p> <p>The dysregulation of gene expression in the TNF-TNFR superfamily has been involved in various human cancers including non-small cell lung cancer (NSCLC). Furthermore, functional polymorphisms in <it>TNF-α </it>and <it>TNFRSF1B </it>genes that alter gene expression are likely to be associated with risk and clinical outcomes of cancers. However, few reported studies have investigated the association between potentially functional SNPs in both <it>TNF-α </it>and <it>TNFRSF1B </it>and prognosis of NSCLC patients treated with chemoradiotherapy.</p> <p>Methods</p> <p>We genotyped five potentially functional polymorphisms of <it>TNF-α </it>and <it>TNFRSF1B </it>genes [<it>TNF-α </it>-308 G>A (rs1800629) and -1031 T>C (rs1799964); <it>TNFRSF1B </it>+676 T>G (rs1061622), -1709A>T(rs652625) and +1663A>G (rs1061624)] in 225 NSCLC patients treated with chemoradiotherapy or radiotherapy alone. Kaplan-Meier survival analysis, log-rank tests and Cox proportional hazard models were used to evaluate associations between these variants and NSCLC overall survival (OS).</p> <p>Results</p> <p>We found that the <it>TNFRSF1B </it>+676 GG genotype was associated with a significantly better OS of NSCLC (GG <it>vs. </it>TT: adjusted HR = 0.38, 95% CI = 0.15-0.94; GG <it>vs. </it>GT/TT: adjusted HR = 0.35, 95% CI = 0.14-0.88). Further stepwise multivariate Cox regression analysis showed that the <it>TNFRSF1B </it>+676 GG was an independent prognosis predictor in this NSCLC cohort (GG <it>vs. </it>GT/TT: HR = 0.35, 95% CI = 0.14-0.85), in the presence of node status (N_2-3<it>vs. </it>N_0-1: HR = 1.60, 95% CI = 1.09-2.35) and tumor stage (T_3-4<it>vs. </it>T_0-2: HR = 1.48, 95% CI = 1.08-2.03).</p> <p>Conclusions</p> <p>Although the exact biological function for this SNP remains to be explored, our findings suggest a possible role of <it>TNFRSF1B </it>+676 T>G (rs1061622) in the prognosis of NSCLC. Further large and functional studies are needed to confirm our findings.</p

Study of additions of disilanes to acetylenes and their applications in organic and polymer synthesis

Three separate studies are included in this dissertation;The first section of this thesis addresses the discovery of the trans-addition of disilanes to acetylenes. The reaction was performed with the 5,5,6,6-tetramethyl-3,3,8,8-tetraphenyl-4,7-dioxa-5,6-disila-cyclooctayne (1) under argon flow at 600°C to give 1,1,4,4-tetramethyl-3,3,6, 6-tetraphenyl-2,5-dioxa-1,4-disila-dicyclo (3,3,0) octa-7-ene (2). Ab initio calculations with MP4/6-31G** were carried out to find the transition state structure. The activation energy was determined to be 34 kcal/mol. It was found that the intramolecular trans-addition of disilane to acetylene also occurred photochemically when the acetylene is conjugated with an aromatic group;The second section of this thesis involves the synthesis of a novel, blue light-emitting molecules containing the 3,3,3',3'-tetramethyl-3,3 '-disila-indeno (2,1-a) indene unit were synthesized with our recently discovered intramolecular addition of disilanes to acetylenes. Light-emitting diodes (LEDs) were fabricated by vapor deposition. The chromophore was also incorporated into polysiloxanes and polymethacrylate as pendent groups. Due to their high chemical stabilies and quantum yields, these polymers are excellent candidates for fabrication of polymer-based blue-light LEDs;The last section deals with the synthesis of a 2-silaoxetane molecule by the catalytic intramolecular addition of disilane to acetylene. The stability of the molecule was studied thermochemically and photochemically. The activation energy of decomposition of the 2-silaoxetane was found to be about 49.24 kcal/mol and Log(A) was 15.37. This process was also studied by ab initio calculations which showed that the decomposition was a highly non-synchronized but concerned process. The four-membered ring system expanded to a five-membered ring photochemically.</p

Smart City, Digitalization and CO2 Emissions: Evidence from 353 Cities in China

The development of digital technology provides new governance methods for achieving the goal of &ldquo;carbon peaking and carbon neutrality&rdquo;. Since 2013, the pilot construction of smart cities in China has strengthened the government&rsquo;s digital governance capabilities and significantly influenced the reduction in carbon emissions. This paper provides empirical evidence for the driving effect of digitization on carbon emission reduction based on panel data from 353 cities in China. The results show that digital governance based on smart city construction pilots has significantly reduced regional carbon emissions, and the implementation of smart city construction pilots has reduced regional carbon emissions by an average of 6.6%, and this effect is sustainable over the long term. The increase in the level of digitalization has significantly promoted carbon emission reduction. From the perspective of the impact path, regional green patent innovation has played a significant partial intermediary effect in the process of digitization-driven carbon emission reduction. From a micro-mechanism standpoint, digitization plays a significant role in promoting the green innovation of high-polluting listed companies

Ascorbate Protects The Diheme Enzyme, Maug, Against Self-Inflicted Oxidative Damage By An Unusual Antioxidant Mechanism

Ascorbate protects MauG from self-inactivation that occurs during the autoreduction of the reactive bis-FeIV state of its diheme cofactor. The mechanism of protection does not involve direct reaction with reactive oxygen species in solution. Instead, it binds to MauG and mitigates oxidative damage that occurs via internal transfer of electrons from amino acid residues within the protein to the high-valent hemes. The presence of ascorbate does not inhibit the natural catalytic reaction of MauG, which catalyzes oxidative posttranslational modifications of a substrate protein that binds to the surface of MauG and is oxidized by the high-valent hemes via long-range electron transfer. Ascorbate was also shown to prolong the activity of a P107V MauG variant that is more prone to inactivation. A previously unknown ascorbate peroxidase activity of MauG was characterized with a kcat of 0.24 s−1 and a Km of 2.2 μM for ascorbate. A putative binding site for ascorbate was inferred from inspection of the crystal structure of MauG and comparison with the structure of soybean ascorbate peroxidase with bound ascorbate. The ascorbate bound to MauG was shown to accelerate the rates of both electron transfers to the hemes and proton transfers to hemes which occur during the multistep autoreduction to the diferric state which is accompanied by oxidative damage. A structural basis for these effects is inferred from the putative ascorbate-binding site. This could be a previously unrecognized mechanism by which ascorbate mitigates oxidative damage to heme-dependent enzymes and redox proteins in nature