Comprehensive profiling and quantitation of amine group containing metabolites

Primary and secondary amines, including amino acids, biogenic amines, hormones, neurotransmitters, and plant siderophores, are readily derivatized with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate using easily performed experimental methodology. Complex mixtures of these amine derivatives can be fractionated and quantified using liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS). Upon collision induced dissociation (CID) in a quadrupole collision cell, all derivatized compounds lose the aminoquinoline tag. With the use of untargeted fragmentation scan functions, such as precursor ion scanning, the loss of the aminoquinoline tag (Amq) can be monitored to identify derivatized species; and the use of targeted fragmentation scans, such as multiple reaction monitoring, can be exploited to quantitate amine-containing molecules. Further, with the use of accurate mass, charge state, and retention time, identification of unknown amines is facilitated. The stability of derivatized amines was found to be variable with oxidatively labile derivatives rapidly degrading. With the inclusion of antioxidant and reducing agents, tris(2-carboxyethyl)-phosphine (TCEP) and ascorbic acid, into both extraction solvents and reaction buffers, degradation was significantly decreased, allowing reproducible identification and quantification of amine compounds in large sample sets.     

Global identification of O-GlcNAc-modified proteins

The O-linked N-acetylglucosamine (O-GlcNAc) modification of serine/threonine residues is an abundant posttranslational modification present in cytosolic and nuclear proteins. The functions and subproteome of O-GlcNAc modification remain largely undefined. Here we report the application of the tagging-via-substrate (TAS) approach for global identification of O-GlcNAc-modified proteins. The TAS method utilizes an O-GlcNAc azide analogue for metabolic labeling of O-GlcNAc-modified proteins, which can be chemoselectively conjugated for detection and enrichment of the proteins for proteomics studies. Our study led to the identification of 199 putative O-GlcNAc-modified proteins from HeLa cells, among which 23 were confirmed using reciprocal immunoprecipitation. Functional classification shows that proteins with diverse functions are modified by O-GlcNAc, implying that O-GlcNAc might be involved in the regulation of multiple cellular pathways.     

Chemical modification of group IV graphene analogs

Mono-elemental two-dimensional (2D) crystals (graphene, silicene, germanene, stanene, and so on), termed 2D-Xenes, have been brought to the forefront of scientific research. The stability and electronic properties of 2D-Xenes are main challenges in developing practical devices. Therefore, in this review, we focus on 2D free-standing group-IV graphene analogs (graphene quantum dots, silicane, and germanane) and the functionalization of these sheets with organic moieties, which could be handled under ambient conditions. We highlight the present results and future opportunities, functions and applications, and novel device concepts.     

STM induced modification of gold surface in the presence of TMP amine

In this paper we present scanning tunneling microscopy (STM) investigations of gold with 2,2,6,6-Tetramethylpiperidine (TMP) overlayer. During the STM experiments the creation of holes and hills or no changes of the surface were observed depending on the applied bias voltage and polarity. No modifications were observed in the bias range from −0.5 to +0.5 V. The holes were created for the bias voltages greater than +0.5 V and hills for the bias voltages lower than −0.5 V. The observed changes of the surface morphology suggest the presence of electrochemical reaction between the tip and the surface. Additionally, our results suggest that TMP lowers the electrochemical activation energy of gold to +0.5 eV.     

功能分子共聚改性聚乳酸的研究进展

为了获得降解性能、亲水性能和力学性能等更好的生物材料,各种功能分子改性聚乳酸的研究日益受到重视.本文按照官能团的不同,综述了近年来功能分子共聚改性聚乳酸的研究情况,指出利用新颖的功能分子改性聚乳酸和利用直接熔融共聚法降低共聚改性聚乳酸是未来的发展方向.     

MXene的功能化改性及其应用研究进展

MXene是一类新型的具有类石墨烯结构的二维材料,由过渡金属碳化物、氮化物或碳氮化物构成。MXene具有优异的物理化学性质,如较大的比表面积、良好的导电性、优异的催化性、优良的自润滑性能、丰富的表面官能团等,在多个领域展现出广阔的潜在应用前景。本文针对MXene片层易叠加及其与聚合物基体相容性较差等问题,对MXene表面功能化改性的研究进展进行了综述,包括有机物、无机物、有机-无机杂化改性等,并总结了其在储能、催化和摩擦学等领域的应用研究,展望了其未来的研究方向和发展前景。     

聚磷腈接枝官能团的光电性能

合成了3种以聚磷腈为主链,接枝不同官能团的非线性化合物,分别是对硝基苯胺接枝苯酚聚磷腈、2,4-二硝基苯胺接枝苯酚聚磷腈、2,4-二硝基苯胺接枝咔唑聚磷腈,对3种化合物进行光电性能测试,含咔唑聚磷腈接枝2,4-二硝基苯胺的光电导率和电光系数是较大的。通过探索官能团结构与聚磷腈光电性能间的关系,为实验设计合成新的非线性材料提供理论支持。     

双官能基改性硅油的制备和表征

以八甲基环四硅氧烷(D4)、长链烷基甲基二甲氧基硅烷(HD-109)、N-β.氨乙基-γ-氨丙基甲基二甲氧基硅烷(YDH-602)和六甲基二硅氧烷(MM)为原料,在四甲基氢氧化铵(TMAH)催化下,采用本体聚合反应合成了一种新型硅油-氨基与长链烷基共改性硅油(ADMPS).对实验条件进行了优化探索,结果表明:反应温度110～115℃、反应时间8h、YDH-602和HD-109用量占D4的质量分数分别为7%～8%和9%时,可获得黏度适宜、应用性能较好的双官能基硅油.用红外光谱、核磁共振氢谱对其结构进行了表征.     

Polymer-binding peptides for the noncovalent modification of polymer surfaces: effects of peptide density on the subsequent immobilization of functional proteins

Peptides that specifically bind to polyetherimide (PEI) were selected, characterized, and used for the noncovalent modification of the PEI surface. The peptides were successfully identified from a phage-displayed peptide library. A chemically-synthesized peptide composed of the Thr-Gly-Ala-Asp-Leu-Asn-Thr sequence showed an extremely high binding constant for the PEI films (5.6 × 10(8) M(-1)), which was more than three orders of magnitude greater than that for the reference polystyrene films. The peptide was biotinylated and immobilized onto the PEI films to further immobilize streptavidin (SAv). The amount of SAv bound depended on the density of immobilized peptide. It gradually increased with an increasing density of immobilized peptide and achieved a maximum (2.1 pmol cm(-2)) at a peptide density of 19.8 pmol cm(-2). The ratio of peptide used for immobilizing SAv at the maximum value was only 11%, and was partially due to the low accessibility of SAv to the biotin moieties on the PEI films. Moreover, the amount of SAv bound gradually decreased at higher peptide densities, suggesting that the clustering of the peptides also inhibited the binding of SAv. Furthermore, peptides on the PEI films promoted the uniform immobilization of SAv with less structural denaturing. The immobilized SAv was able to further immobilize probe DNA to hybridize with its complementary DNA. These present results suggest that the density of immobilized peptide has a great impact on the surface modifications using polymer-binding peptides.     

Surface modification of zirconia with acid groups

We have studied the effect of surface modification with acids and subsequent heat treatment on the properties of hydrous zirconia. It has been shown that surface modification with phosphate and sulfate groups makes it possible not only to control the phase composition of the heat-treated oxide but also to considerably suppress particle growth. We have discussed the processes involved and shown that, in the initial stages of thermolysis, the process leads to the formation of metastable, tetragonal ZrO₂, which transforms into monoclinic zirconia at higher temperatures. Surface modification with phosphoric acid stabilizes tetragonal zirconia up to 850°C.     

Self-antibacterial UV-curable waterborne polyurethane with pendant amine and modified by guanidinoacetic acid

Enhancing the dispersion stability and self-antibacterial properties of cationic waterborne polyurethane materials is of vital importance to its various applications. In this work, a novel UV-curable waterborne polyurethane with pendant amine (PWPU) from 4-NCO prepolymer and modified by guanidinoacetic acid (GAA) was prepared by a simple method. The 4-NCO prepolymer is originated from the progressively grafting of tridentate polycaprolactone. The GAA, which is rarely used in coating industry, plays a positive reinforced role in our self-antibacterial coatings. Taking fully advantage of the merits of pendant amine and GAA, PWPU without bactericides possesses excellent properties in gram-negative (92.05%) and gram-positive (94.77%) antibacterial tests. Compared with the linear amine waterborne polyurethane (LWPU), PWPU has significant superiority in stability, and the increase in antibacterial efficiency is about 50%. Moreover, antibacterial efficiency still maintained 87.94% after 12 times washing. AFM results display that GAA and pendant amine increase the hydrophilic groups of coating surface, which improves the antibacterial performance. The experiments of thermal, mechanical performance and chemical resistance proof the reliability of the coatings. Therefore, this work has large potential in the applications of antibacterial materials.     

Partial reduction and two-step modification of proteins for identification of disulfide bonds

An experimental protocol was established to combine partial reduction, cyanylation, and a second modification step for the assignment of disulfide bonds in proteins that are resistant to proteolysis under native conditions. After proteolysis, disulfide bonds were assigned via MALDI mass spectrometry with subsequent semiautomatic interpretation using the program SearchXLinks, which enumerates all possible combinations of proteolytic fragments for all observed monoisotopic masses. The putative assignment of disulfide bonds was confirmed by ISD and PSD fragmentation of the corresponding protonated molecules.     

聚乳酸改性的研究进展

综述了聚乳酸化学、物理以及纳米复合改性方面的研究进展,重点讨论了目前的研究热点及其今后的发展趋势,并时其前景做了展望.     

Global sensitivity analysis of computer models with functional inputs

Global sensitivity analysis is used to quantify the influence of uncertain model inputs on the response variability of a numerical model. The common quantitative methods are appropriate with computer codes having scalar model inputs. This paper aims at illustrating different variance-based sensitivity analysis techniques, based on the so-called Sobol's indices, when some model inputs are functional, such as stochastic processes or random spatial fields. In this work, we focus on large cpu time computer codes which need a preliminary metamodeling step before performing the sensitivity analysis. We propose the use of the joint modeling approach, i.e., modeling simultaneously the mean and the dispersion of the code outputs using two interlinked generalized linear models (GLMs) or generalized additive models (GAMs). The “mean model” allows to estimate the sensitivity indices of each scalar model inputs, while the “dispersion model” allows to derive the total sensitivity index of the functional model inputs. The proposed approach is compared to some classical sensitivity analysis methodologies on an analytical function. Lastly, the new methodology is applied to an industrial computer code that simulates the nuclear fuel irradiation.     

含侧环氧基硅油复合改性环氧树脂的研究

采用侧基环氧化硅油(ES)及其改性物(PSA)来复合改性双酚A型环氧树脂(EP).通过测定复合改性固化物的冲击强度、拉伸强度、断裂伸长率和玻璃化转变温度(Tg),扫描电子显微镜对改性固化物的断裂面形态分析等,系统探讨了复合改性方法、有机硅组成及其含量等对复合改性材料性能的影响.结果表明,采用ES和PSA复合改性EP后,其韧性和耐热性均有不同程度的提高,且以环氧值高的ES和PSA的改性效果更好.其中环氧树脂经10份ES-16或10份PSA-16改性后,Tg由未改性的156.73℃提高到177.35℃,比改性前提高了近20.62℃,均达到了很好的增韧和提高耐热性的效果,符合电子封装等高性能材料的改性要求.     

Single functional group interactions with individual carbon nanotubes

Carbon nanotubes display a consummate blend of materials properties that affect applications ranging from nanoelectronic circuits and biosensors to field emitters and membranes. These applications use the non-covalent interactions between the nanotubes and chemical functionalities, often involving a few molecules at a time. Despite their wide use, we still lack a fundamental understanding and molecular-level control of these interactions. We have used chemical force microscopy to measure the strength of the interactions of single chemical functional groups with the sidewalls of vapour-grown individual single-walled carbon nanotubes. Surprisingly, the interaction strength does not follow conventional trends of increasing polarity or hydrophobicity, and instead reflects the complex electronic interactions between the nanotube and the functional group. Ab initio calculations confirm the observed trends and predict binding force distributions for a single molecular contact that match the experimental results. Our analysis also reveals the important role of molecular linkage dynamics in determining interaction strength at the single functional group level.     

Low density polyethylene with an isocyanate functional group

In order to introduce an isocyanate (NCO) functional group into low density polyethylene (LDPE), grafting of 2-hydroxyethyl methacrylate (HEMA) combined with isophorone diisocyanate (IPDI) on to LDPE was carried out in solution using a radical initiator. The spectra of infrared (i.r.) and proton nuclear magnetic resonance for HEMA combined with IPDI showed that the hydroxyl group of HEMA and the NCO group of IPDI were reacted to form urethane, and the secondary NCO group preferentially reacted over the primary NCO group. From the i.r. spectra of the grafted LDPE, it was found that NCO groups were introduced into LDPE. Thermal stability of the grafted LDPE was investigated by differential scanning calorimeter analysis, and rheological values were observed to evaluate processability.     

Characterization and modification of commercial acrylic fibers grafted with acrylic acid

The graft copolymerization of acrylic acid (AA) onto commercial acrylic fibers (PAN) has been studied using Azobis(isobutyro)nitrile (AIBN) as an initiator. AA grafting initiated by radicals formed from thermal decomposition of AIBN. In this study, the effects of monomer and initiator concentration, time and temperature reaction on the grafting yield have been investigated. The optimum conditions for this grafting reaction were obtained with an AA concentration of 1.67 M, an AIBN concentration of 0.0097 M, a reaction temperature of T=85 °C and with reaction time of 60 minutes. The fiber structure has been investigated by different experimental techniques of characterization such as Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), water absorption and also in this study has been investigated the mechanical property. The thermal analysis data showed that increasing in grafting yield, decreases the thermal stability of fiber. Grafting also affected slightly the fiber morphology. The experimental data of mechanical properties show clearly that by increasing of grafting yield, max extension will decrease. Grafting of poly AA improved water absorption.