Electronic structures of ionic liquids formed by 1-buthyl-3-alkylimidazolium ion [Cnmim]+ (n = 4 and 8) with various inorganic and organic anions have been investigated by ultraviolet photoemission, X-ray photoemission, inverse photoemission and soft X-ray emission spectroscopies (SXES). The comparison of the calculated density of states with the observed spectra revealed that the molecular orbital energies of these ionic liquids are significantly affected by the electrostatic Madelung potential among the ions. The SXES results clearly show that the both highest occupied and lowest unoccupied states of [C4mim]+PF6− are derived from the cation as a result of strong Madelung potential. On the other hand, the SXES results show the valence electronic structures of ionic liquids with larger anion molecules, [Cnmim]+Tf2N− and [Cnmim]+OTf− are contributed from the both cation and anion. 相似文献
Anionic polymerization of triphenylmethyl methacrylate was performed by using P-chiral bisphosphine initiators. According to the optical rotation analysis and circular dichroism measurements, the polymer obtained by using the initiator (S,S)-1,2-bis(boranato(tert-butyl)methylphosphino) ethane exhibited one-handed helical conformation induced by the chirality of phosphorus atoms in the polymer terminal. The enantiomer (R,R)-1,2-bis(boranato(tert-butyl)methylphosphino) ethane gave the opposite one-handed helical polymer. Optically active bisphosphine (S,S)-1,2-bis(boranatomethylphenylphosphino) ethane was employed for the helix-sense-selective polymerization of triphenylmethyl methacrylate in order to obtain the polymer with the same helix sense as the polymer obtained from the initiator (S,S)-1,2-ethane bis(t-butylm-ethylphosphineborane). Further, removal of the coordinated boranes and complexation with platinum(II) on the chiral phosphorus atoms were carried out in order to yield the corresponding polymer-platinum(II) complex without loss of its chiral higher-ordered structure. 相似文献
An in situ, selective, and quantitative hydrogenation of the terminal chlorine (alpha-haloester) in living PMMA-Cl into PMMA-H was achieved via direct transformation of a "polymerization catalyst" into a "hydrogenation catalyst" in the Ru(II)-catalyzed living radical polymerization, where the polymerization mixture of MMA was directly treated in situ with K2CO3 as a base and 2-propanol as a hydrogen donor. The reaction terminated the polymerization and, more importantly, the terminal chlorine was quantitatively hydrogenated, as confirmed by SEC, 1H NMR, and MALDI-TOF MS. 相似文献
Chemical synthesis of homogeneous human glycoproteins exhibiting bioactivity in vivo has been a challenging task. In an effort to overcome this long-standing problem, we selected interferon-β and examined its synthesis. The 166 residue polypeptide chain of interferon-β was prepared by covalent condensation of two synthetic peptide segments and a glycosylated synthetic peptide bearing a complex-type glycan of biological origin. The peptides were covalently condensed by native chemical ligation. Selective desulfurization followed by deprotection of the two Cys(Acm) residues gave the target full-length polypeptide chain of interferon-β bearing either a complex-type sialyl biantennary oligosaccharide or its asialo form. Subsequent folding with concomitant formation of the native disulfide bond afforded correctly folded homogeneous glycosyl-interferon-β. The chemically synthesized sialyl interferon-β exhibited potent antitumor activity in vivo. 相似文献
A known amount of lithium or calcium nitrate solution is added to the sample powder which is then heated in air or oxygen. The oxygen in test samples of UO2+x, Sr0.1U0.9O2 + x and Sr0.2U0.5O2 + x was determined with an estimated standard deviation of ± 0.002. 相似文献
Bagasse, corn husk, and switchgrass were pretreated with ammonia water to enhance enzymatic hydrolysis. The sample (2 g) was
mixed with 1–6 mL ammonia water (25–28% ammonia) and autoclaved at 120°C for 20 min. After treatment, the product was vacuum-dried
to remove ammonia gas. The dried solid could be used immediately in the enzymatic hydrolysis without washing. The enzymatic
hydrolysis was effectively improved with more than 0.5 and 1 mL ammonia water/g for corn husk and bagasse, respectively. In
bagasse, glucose, xylose, and xylobiose were the main products. The adsorption of CMCase and xylanase was related to the initial
rate of enzymatic hydrolysis. In corn husks, arabinoxylan extracted by pretreatment was substantially unhydrolyzed because
of the high ratio of arabinose to xylose (0.6). The carbohydrate yields from cellulose and hemicellulose were 72.9% and 82.4%
in bagasse, and 86.2% and 91.9% in corn husk, respectively. The ammonia/water pretreatment also benefited from switchgrass
(Miscanthus sinensis and Solidago altissima L.) hydrolysis. 相似文献
The syntheses of polylactides (PLAs) with branched peptide end groups containing reactive (ionic) moieties such as amino or carboxyl groups are described and were used to prepare PLA‐based microspheres (MSs) with positively or negatively charged surfaces. Branched peptides with hydroxyl end groups and four protected amino or carboxyl groups, Boc4‐K3‐OH or Bn4‐E3‐OH, were synthesized, and the hydroxyl group converted to an alkoxide and was used as the initiation site for the ring‐opening polymerization of L ‐lactide. Subsequent deprotection gave PLAs end‐capped with branched peptides having four amino or carboxyl groups, respectively (K3‐PLA and E3‐PLA). K3‐PLA and E3‐PLA were converted to K34+‐PLA and E34?‐PLA by acid or base treatment, respectively. MSs with charged surfaces were then prepared using K34+‐PLA or E34?‐PLA as a surfactant [MS(K34+‐PLA) or MS(E34?‐PLA)]. The ionic surface state of the MSs was confirmed by colloidal titration and zeta potential analysis.
Styrene(St) was polymerized in benzene solution in the presence of l, 3:2, 4:5, 6-trimethylene-D-sorbitol(TCA) by means of photo-irradiation of system at 30°C. It was found that the polymerization was depressed by the addition of TCA and then proceeded through a radical mechanism. The chain-transfer constant of the styryl radical to TCA was estimated to be 0.16. Accordingly, the photopolymerization of St in the presence of TCA is studied kinetically with regard to chain transfer and termination. 相似文献