Influence of halogenation on the properties of uracil and its noncovalent interactions with alkali metal ions. Threshold collision-induced dissociation and theoretical studies

The influence of halogenation on the properties of uracil and its noncovalent interactions with alkali metal ions is investigated both experimentally and theoretically. Bond dissociation energies of alkali metal ion-halouracil complexes, M+(XU), are determined using threshold collision-induced dissociation techniques in a guided ion beam mass spectrometer, where M+ = Li+, Na+, and K+ and XU = 5-fluorouracil, 5-chlorouracil, 6-chlorouracil, 5-bromouracil, and 5-iodouracil. The structures and theoretical bond dissociation energies of these complexes are determined from ab initio calculations. Theoretical calculations are also performed to examine the influence of halogenation on the acidities, proton affinities, and Watson-Crick base pairing energies. Halogenation of uracil is found to produce a decrease in the proton affinity, an increase in the alkali metal ion binding affinities, an increase in the acidity, and stabilization of the A::U base pair. In addition, alkali metal ion binding is expected to lead to an increase in the stability of nucleic acids by reducing the charge on the nucleic acid in a zwitterion effect as well as through additional noncovalent interactions between the alkali metal ion and the nucleobases.     

Supramolecular template‐directed synthesis of stable and high‐efficiency photoluminescence 9,10‐diphenylanthryl‐bridged ladder polysiloxane

A soluble well‐defined 9,10‐diphenylanthryl‐bridged ladder polysiloxane ( DPAnLP ) was prepared via supramolecular assembly‐directed condensation polymerization of silanols. The ladder superstructure ( LS ) was obtained via a synergistic interaction of H‐bonding and π–π stacking between polymerizable precursor 2‐tert‐butyl‐9,10‐bis(methyldihydroxylsilyl)anthracene in organic solvent. The resultant LS was then used as template to direct the condensation of silanol groups to obtain DPAnLP with high regularity. It was found that DPAnLP can emit blue light (430 nm) with great stability and high efficiency in both solution and solid film, which indicated a well organizing of fluorophore within confined environment (ladder structure). TGA and DSC measurements showed that DPAnLP had good thermal stability, and cyclic voltammetry detection gave a low‐lying highest occupied molecular orbital level. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2491–2497, 2010     

Effects of molecular weight on thermal responsive property of pegylated poly-l-glutamates

We investigated the ring opening polymerization (ROP) of di- and tri-ethylene glycol monomethyl ether functionalized L-glutamate N-carboxyanhydrides (NCAs) using hexamethyldisilazane (HMDS) as primary initiator and 1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD) as co-initiator. The binary initiator system afforded a living ROP for these pegylated NCAs, and a series of homopolypeptides with controlled molecular weight (MW) and low polydispersity were obtained. We then systematically studied the helical content and clouding point (CP) dependence on polypeptide MW using circular dichroism (CD) spectroscopy and turbidity measurements, respectively. We found that the helical content of both homopolypeptides increased with MW, but the triethylene glycol functionalized poly-L-glutamate (poly-L-EG3Glu) intended to form more stable α-helical structure than diethylene glycol functionalized counterpart (poly-L-EG2Glu) at similar MW. Accordingly, the CP of poly-L-EG2 Glu with known end group has strong dependence on its helical content, which is essentially determined by MW. Our results suggested that the thermal responsive properties of these unique pegylated poly- L-glutamates not only rely on their chemical structure but also on their secondary structures, which is different from conventional thermal responsive polymers.     

Self-assembly of block copolymer micelles in an ionic liquid

Four amphiphilic poly((1,2-butadiene)-block-ethylene oxide) (PB-PEO) diblock copolymers were shown to aggregate strongly and form micelles in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF(6)]). The universal micellar structures (spherical micelle, wormlike micelle, and bilayered vesicle) were all accessed by varying the length of the corona block while holding the core block constant. The nanostructures of the PB-PEO micelles formed in an ionic liquid were directly visualized by cryogenic transmission electron microscopy (cryo-TEM). Detailed micelle structural information was extracted from both cryo-TEM and dynamic light scattering measurements, with excellent agreement between the two techniques. Compared to aqueous solutions of the same copolymers, [BMIM][PF(6)] solutions exhibit some distinct features, such as temperature-independent micellar morphologies between 25 and 100 degrees C. As in aqueous solutions, significant nonergodicity effects were also observed. This work demonstrates the flexibility of amphiphilic block copolymers for controlling nanostructure in an ionic liquid, with potential applications in many arenas.     

Rapid Formation of a Supramolecular Polypeptide–DNA Hydrogel for In Situ Three‐Dimensional Multilayer Bioprinting

A rapidly formed supramolecular polypeptide–DNA hydrogel was prepared and used for in situ multilayer three‐dimensional bioprinting for the first time. By alternative deposition of two complementary bio‐inks, designed structures can be printed. Based on their healing properties and high mechanical strengths, the printed structures are geometrically uniform without boundaries and can keep their shapes up to the millimeter scale without collapse. 3D cell printing was demonstrated to fabricate live‐cell‐containing structures with normal cellular functions. Together with the unique properties of biocompatibility, permeability, and biodegradability, the hydrogel becomes an ideal biomaterial for 3D bioprinting to produce designable 3D constructs for applications in tissue engineering.     

基于G-四联体的聚多肽-DNA水凝胶响应性研究

利用铜催化的点击反应合成了侧链接枝DNA的聚多肽, 基于DNA自组装的理念, 将含有两段鸟嘌呤(G)的序列引入到体系中, 结合G-四联体在钾离子存在的情况下能够形成分子间四链结构的特性, 获得了具有热响应和离子响应性的聚多肽-DNA超分子水凝胶. 此凝胶制备过程具有原位、快速等特点, 构筑基元具有可设计的响应性和良好的生物相容性. 综合以上特点, 此超分子水凝胶在组织工程和三维生物打印等领域具有潜在的应用.     

Hexapole [9]Helicene

Herein we present the first hexapole [9]helicene ( H9H ). Co‐catalyzed [2+2+2] cyclotrimerization of a dinaphthopyrene (DNP) functionalized alkyne provides the hexaaryl benzene precursor 2 , which is transformed into H9H via a dehydrocyclization reaction. Formation of each embedded [9]helicene involves forging of a new C?C bond, which stitches together two [4]helicene subunits of the neighboring DNP blades, reminiscent of the initial method Martin developed for the preparation of [9]helicene in the 1960s. Single‐crystal X‐ray analysis of both 2 and H9H discloses their extremely distorted and crowded structural features. Chiral resolution, optical and electronic properties of H9H are also presented.     

碳纳米管复合聚丙烯酸钠的制备及吸水性能

以过硫酸铵(APS)为引发剂,N,N′-亚甲基双丙烯酰胺(MBA)为交联剂,采用水溶液聚合法制备了碳纳米管/聚丙烯酸钠高吸水树脂。系统考察了碳纳米管质量分数、引发剂、交联剂和聚合温度对树脂吸水性能的影响。结果表明,以单体丙烯酸质量为基准,当交联剂,引发剂和碳纳米管质量分数分别为0.04%、0.3%和0.3%,聚合温度75℃时,所合成树脂的吸水性能最佳。添加碳纳米管后树脂表面粗糙和形成孔结构导致了其吸水性能的变化,使得碳纳米管/聚丙烯酸钠的吸水量和吸水速率明显提高,其吸去离子水和生理盐水能力分别达到1423和104g/g。该树脂重复吸水5次后,其吸水能力为1081.5g/g,达到最大吸水倍数的76.0%。     

聚苯乙烯微球负载脲催化剂与碱协同催化环内酯的开环聚合

通过环己基异氰酸酯和4-三氟甲基苯异氰酸酯分别与氨基化聚苯乙烯反应, 构筑了聚苯乙烯(PS)负载的环己基脲(PS-U₁)和聚苯乙烯负载的4-三氟甲基苯基脲催化剂(PS-U₂). 利用PS-U/KOMe二元催化体系协同催化环内酯的开环聚合. 结果表明, PS-U/KOMe二元体系可高效催化ε-己内酯(ε-CL)、 δ-戊内酯(δ-VL)和L-丙交酯(L-LA)的开环聚合, 制备了低催化剂残留且环境友好的聚酯材料; 同时实现了PS-U的回收及循环利用.     

基于100 MeV质子回旋加速器与固相萃取方法制备与纯化靶向放射治疗核素锕-225

锕-225可发射4个α粒子和2个β粒子,具有较高的传能线密度和局部肿瘤损伤,因此是靶向放射性核素治疗中受到最多关注的放射性核素之一。经典的锕-225是由铀-233衰变产生,或通过natTh(p,x)225Ac反应生产。但目前我国无论是233U来源或natTh来源的225Ac均无法供应。本研究中,我们基于国产CYCIAE-100高能强流回旋加速器实现了我国首次225Ac的加速器生产,获得了超过600 μCi的225Ac,足够2-3个病人的靶向核素治疗。同时我们设计并优化了全固相萃取的225Ac纯化流程,分离出的225Ac的放射性纯度在99.5%以上,该流程操作简便、高效、且可自动化,可随时用于225Ac的大规模生产。综上所述,我们成功地进行了225Ac的生产和分离的初步研究,为我国进一步发展225Ac供应链奠定基础,为我国学者和医生进行靶向α核素治疗提供了225Ac的额外选择。