Semiquantitative analysis of isomeric oligosaccharides by negative-ion mode UV-MALDI TOF postsource decay mass spectrometry and their fragmentation mechanism study at N-acetyl hexosamine moiety

Postsource decay (PSD) spectra of isomeric neutral lactooligosaccharide mixtures were measured from the chlorinated molecules [M + Cl]- by negative-ion mode ultraviolet matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (UV-MALDI TOF MS) to estimate quantitatively the mixing ratios in their mixtures. The PSD ions specific to each isomeric structure were used to distinguish the linkage and branching isomers, and the molar ratios of the isomers were estimated from their ion abundances. The relative ion abundances changed linearly in the PSD spectra of the mixtures of the isomers as their molar ratio was varied in the analyte solutions. Therefore, the molar ratios of the isomers in the analyte mixtures could be estimated semiquantitatively. In addition, we studied their fragmentation mechanisms in N-acetyl hexosamines such as GlcNAc, which enabled us to quantitatively analyze the structures of the isomers of lactooligosaccharides. The conjugated systems elongate in the chemical species of the Z-type fragmentation on the 3-linked GlcNAc owing to the acetoamido groups at the C-2 positions, which made the chemical species of the Z-type ions stable. The glycosyl bonds of the front of GlcNAc cleaved easily as a C-type fragmentation because the negative charge at the anomeric position could be delocalized to the carbonyl oxygen atom at the acetoamido group of GlcNAc. These factors caused the stabilization of the chemical species of the C/Z fragment ions produced by the double cleavage around GlcNAc.     

Development of a Ca2+‐Sensitive Electrostatic Self‐Assembly Films for the Fabrication of Reproducible Immunosensor

Abstract

A novel strategy for fabricating reproducible immunosensor has been developed by employing the merits of Ca²⁺‐induced cross‐linkage of sodium alginate and negative‐carboxyl groups of alginate. The alginate was used to modify the gold electrode and render the gold electrode negative charge to immobilize antibodies via electrostatic interaction between carboxyl groups on alginate and amino groups on antibodies to realize the fabrication of immunosensor in 0.01 mol/l pH 7.5 acetic‐acetate buffer solution. The Ca²⁺‐induced cross‐linkage of alginate on the immnosensor can release antibodies from electrode and regenerate one fresh alginate‐modified electrode for the fabrication of new immunosensor. The feasibility of the proposed strategy and qualities of the fabricated immunosensor was evaluated by being applied to a competitive transferrin‐transferrin antiserum immunoassay system.     

Meta‐linked and para‐linked water‐soluble poly(arylene ethynylene)s with amino acid side chains: Effects of different linkage on Hg2+ ion sensing properties in aqueous media

Water‐soluble, meta‐ and para‐linked poly(arylene ethynylene)s containing L ‐aspartic acid‐functionalized fluorene units (P1 and P2) and their model compounds (M1 and M2) have been synthesized, and their photophysical properties and fluorescent sensing properties were investigated in aqueous solution. P1 and M1 with the meta‐linkage show blue‐shifted absorption and emission spectra, and decreased photoluminescence quantum yields compared with those of P2 and M2 with para‐linkage. Their absorption and fluorescence spectra are pH dependent perhaps due to the aggregation of the polymer chains at low pH values. In buffer solutions, both polymers and their model compounds exhibit the excellent selectivity and sensitivity to Hg²⁺ over other common metal ions. Furthermore, the quenching constant and detection limit of P1 are determined to be 1.04 × 10⁷ M^?1 and 10 nM, and show the higher sensitivity compared to P2. Further comparison of their model compounds reveal that the sensitivity and quenching efficiency of M1 is also higher than that of M2, indicating that the meta‐linkage pattern plays a key role in improving their Hg²⁺ ion sensing properties. In addition, both meta‐ and para‐linked polymers exhibit the higher quenching efficiency than their model compounds due to the amplified fluorescence response of conjugated polymer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

工程机械中的机构-结构一体化优化设计

工程机械中的运动机构同时往往也是承载机构,其结构优化问题须同时考虑机构运动和结构受力,较传统的结构优化问题需要考虑的因素更多,约束条件更为复杂。本文以广泛应用于工程机械中的四连杆式俯仰机构为对象,研究了工程机械中机构-结构一体化优化问题,探讨了此类优化问题的目标函数、设计变量和约束条件,并对实际工程机械进行了分析和优化,达到了理想的效果。     

连锁—遗传算法中的一种启发式方法

１引言遗传算法（ＧｅｎｅｔｉｃＡｌｇｏｒｉｔｈｍｓ,简称ＧＡ）是由美国密执安大学教授ＪｏｈｎＨｏｌｌａｎｄ提出的,其依据为达尔文的进化论和盂德尔的遗传学说．该算法效法自然界中各物种的进化过程,是一种随机搜索算法,广泛应用于解决各种优化问题．２生物遗传学中的连锁生物遗传学中的连锁现象是Ｂａｔｅｓｏｎ和Ｐｕｎｎｅｔｔ在１９０６年发现的,他们在研究香豌豆的两对性状的遗传时,观察到同一亲体遗传来的基因较多地联在一起,这就是基因的连锁（ｌｉｎｋａｇｅ）现象．这里应给玉米的例子来说明遗传学上的连锁现象．设基…     

Design,Synthesis, and Biological Evaluation of HDAC Degraders with CRBN E3 Ligase Ligands

Histone deacetylases (HDACs) play important roles in cell growth, cell differentiation, cell apoptosis, and many other cellular processes. The inhibition of different classes of HDACs has been shown to be closely related to the therapy of cancers and other diseases. In this study, a series of novel CRBN-recruiting HDAC PROTACs were designed and synthesized by linking hydroxamic acid and benzamide with lenalidomide, pomalidomide, and CC-220 through linkers of different lengths and types. One of these PROTACs, denoted 21a, with a new benzyl alcohol linker, exhibited comparably excellent HDAC inhibition activity on different HDAC classes, acceptable degradative activity, and even better in vitro anti-proliferative activities on the MM.1S cell line compared with SAHA. Moreover, we report for the first time the benzyl alcohol linker, which could also offer the potential to be used to develop more types of potent PROTACs for targeting more proteins of interest (POI).     

Preparation and characterization of aromatic polyamides based on a bis(ether‐carboxylic acid) or a dietheramine extended from 1,1‐bis(4‐hydroxyphenyl)‐1‐phenylethane

Thermoplastic and organic‐soluble aromatic polyamides containing both bulky triphenylethane units and flexible ether linkages were prepared directly from 1,1‐bis[4‐(4‐carboxyphenoxy)phenyl]‐1‐phenylethane ( III ) with various aromatic diamines or from 1,1‐bis[4‐(4‐aminophenoxy)phenyl]‐1‐phenylethane ( V ) with various aromatic dicarboxylic diacids via triphenyl phosphite and pyridine. These polyamides had inherent viscosities ranging from 0.71 to 1.77 dL/g. All the polymers easily were dissolved in aprotic polar solvents such as N‐methyl‐2‐pyrrolidone and N,N‐dimethylacetamide, and some even could be dissolved in less polar solvents such as tetrahydrofuran. The flexible and tough films cast from the polymer solutions possessed tensile strengths of 89 to 104 MPa. The polyamides were thermally stable up to 460°C in air or nitrogen. Glass‐transition temperatures of these polyamides were observed in a range of 179 to 268°C via differential scanning calorimetry or thermomechanical analysis. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 247–260, 2000     

(+)-Sorangicin A: evolution of a viable synthetic strategy

An effective, asymmetric total synthesis of the antibiotic (+)-sorangicin A (1) has been achieved. Central to this venture was the development of first- and second-generation syntheses of the signature dioxabicyclo[3.2.1]octane core, the first featuring chemo- and stereoselective epoxide ring openings facilitated by a Co₂(CO)₆-alkyne complex, the second involving a KHMDS-promoted epoxide ring formation/opening cascade. Additional highlights include effective construction of the dihydro- and tetrahydropyran ring systems, respectively, via a stereoselective conjugate addition/α-oxygenation protocol and a thioketalization/hydrostannane reduction sequence. Late-stage achievements entailed two Julia-Kociénski olefinations to unite three advanced fragments with high E-stereoselectivity, followed by a modified Stille protocol to introduce the Z,Z,E trienoate moiety, thereby completing the carbon skeleton. Mukaiyama macrolactonization, followed by carefully orchestrated Lewis and protic acid-promoted deprotections that suppressed isomerization and/or destruction of the sensitive (Z,Z,E)-trienoate linkage completed the first, and to date only, total synthesis of (+)-sorangicin A (1).     

Structural Engineering of Semiconductor Nanoparticles by Conjugated Interfacial Bonds

Surface functionalization of semiconductor nanoparticles plays a significant role in the manipulation of the nanoparticle physicochemical properties and diverse applications. Conventional points of anchor involve mercapto, carboxyl and phenol moieties, forming largely nonconjugated interfacial linkages. In this personal account, we summarize recent progress in surface functionalization of semiconductor nanoparticles with olefin and acetylene derivatives, where the formation of conjugated interfacial bonds leads to ready manipulation of the nanoparticle optical and electronic properties, by using Si and TiO₂ nanoparticles as the illustrating examples. Finally, a perspective is included where the promises and challenges of structural engineering of semiconductor nanoparicles are highlighted.     

A combined theoretical and thermal analysis study on the solid state linkage isomerization of Ni(II)-nitrite complexes with ethylenediamine derivatives*

Solid state stepwise nitro–nitrito linkage isomerization of trans-[dinitrobis(ethylenediamine)nickel(II)], [Ni(en)₂(NO₂)₂] (N,N-en), trans-[dinitrobis(N,N′-dimethylethylenediamine)nickel(II)], [Ni(N,N′-dmen)₂(NO₂)₂] (N,N-dmen), and trans-[dinitritobis(N,N-dimethylethylenediamine)nickel(II)], [Ni(N,N-dmen)₂(ONO)₂] (O,O-udmen) were investigated by performing non-isothermal differential scanning calorimetry (DSC) analyses and the thermodynamic and thermokinetic parameters of isomerization were determined using DSC curves. Both N,N-en and N,N-dmen DSC curves show an endothermic peak at elevated temperatures, attributed to dinitro-to-dinitrito linkage isomerization. Similar exothermic peaks were observed in the cooling cycle, assigned to the reverse dinitrito-to-dinitro isomerization. The O,O-udmen isomer is more stable than the corresponding dinitro one at ambient temperatures, but an exothermic dinitrito-to-dinitro isomerization occurs upon cooling down to ?70 °C and reverts endothermically to dinitrito isomer upon heating up to ambient temperature. The overlapping DSC peaks associated with stepwise linkage isomerization were resolved using nonlinear fitting method. The peak temperature and the enthalpy changes of linkage isomerization are inversely dependent on the steric hindrance provided by diamine ligands, which increases in the order udmen > dmen > en. The results showed that the steric factor of the co-ligands also influences the kinetic parameters of isomerization, so that more bulky ligand substituent leads to higher isomerization rate constants. A DFT and TD-DFT calculations have been carrid out on both dinitro complexes of this investigation .