羧甲基壳聚糖在果蔬保鲜中的应用研究进展

综述了羧甲基壳聚糖的特性及其在果蔬的涂膜保鲜中的应用研究进展,讨论了羧甲基壳聚糖的浓度、分子量、pH值、取代度对其特性的影响,介绍了羧甲基壳聚糖对果蔬的涂膜保鲜效果。本文对开发羧甲基壳聚糖在果蔬防腐保鲜方面的应用具有理论指导意义。     

Cesium-137 spatial activity in surface soils near and surrounding the Gurí Reservoir (Venezuela)

Summary The ¹³⁷Cs activities (Bq ^. kg^-1) were determined in more than ninety soil samples between 2 and 5 cm depths surrounding and near the Guri Reservoir (state of Bolivar, Venezuela). The measurements were performed by high-resolution gamma-ray spectroscopy, employing Soil-6 as a comparator. In general, the values of the ¹³⁷Cs activities were about double on the west side of the reservoir than on the east side, the environmental parameters were similar on both sides, but the soils were very different, they were untisols on the western side and entisols on the eastern one. The soils were highly mineralized and on the western side they were above rich iron deposits. Many of the sampling sites on the eastern side were annually covered with water, when the reservoir was at high levels. The anomalously high ¹³⁷Cs values, southeast of the reservoir were found in a small area that had very different environmental characteristics and can be explained by the direct deposition of the fallout by the clouds on the vegetation and surface, since this area is in a dense cloud forest.     

Biomimetic superhydrophobic UHMWPE/nanosilica films with different sticky behavior on several metals

A kind of organic–inorganic composite film with biomimetic superhydrophobic performance was prepared on several metals including steel, aluminum, and copper. The organic matrix was ultrahigh‐molecular‐weight polyethylene (UHMWPE), and the inorganic filler was nanosilica. Scanning electron microscope observation indicated addition of nanosilica greatly changed the topography of the UHMWPE film. Special convexities were formed on the surfaces of the composite films, which made the composite films rougher than that of pure UHMWPE film. The nanosilica randomly scattered on the surface of the convexities and formed hierarchical structure similar to that of some plant leaves with superhydrophobic characteristics. Interestingly, it was found that there were remarkable differences between the sliding angles (SA) of water droplet on the composite films on different metals although the contact angles (CA) of water droplet on these films were quite close. The CA on the composite films on steel was about 157°, and the SA was larger than 90°, which demonstrated obvious superhydrophobic and sticky characteristic. But to the films on aluminum and copper, the CAs on them were larger than 160° and the SAs were between 3° and 4°, which meant excellent superhydrophobic and roll‐off performance. Scanning electron microscope observation indicated that there were some micro‐orifices in the film on steel and these micro‐orifices were connected to some extent. It was believed that these micro‐orifices provided capillary force and restrained sliding of water droplet. A sticky model based on capillary mechanism was proposed. Copyright © 2017 John Wiley & Sons, Ltd.     

Growth and characterization of pyrene crystals on carbon nanofibers

Pyrene crystals were grown on carbon nanofibers (CNFs) by dispersing pyrene polycrystals and CNFs in water during ultrasonic irradiation, and they were characterized by scanning electron microscopy, X-ray diffractometry (XRD) and spectroscopy. The XRD measurements indicated that the orientation and size of the pyrene crystals on the CNF aggregates were different from that of the added pyrene polycrystals. Based on the spectroscopic properties of the pyrene crystals on the CNFs, the pyrene crystals on the CNF aggregates and on the individual CNFs were determined to be polycrystals and single crystals, respectively. These results indicate that pyrene crystals are produced on the CNFs by recrystallization of the added pyrene polycrystals and their crystal states depend on the aggregation state of the CNFs.     

Site-specific dense immobilization of antibody fragments on polymer brushes supported by silicone nanofilaments

For site-specific dense immobilization of antibodies on a solid support, we prepared phosphorylcholine copolymer brushes on silicone nanofilaments. The nanofilaments were prepared on a silicon wafer by treatment with trichloromethylsilane (MeSiCl 3). To generate Si-OH groups on the nanofilaments, O 2 plasma was irradiated on the surface. Initiators for atom transfer radical polymerization (ATRP) were then coupled on the filaments. Phosphorylcholine copolymer brushes were prepared by a "grafting from" process, and pyridyl disulfide groups were introduced into the polymer chains. F(ab') fragments were then specifically immobilized onto these surfaces via a thiol-disulfide interchange reaction. The amount of antibodies immobilized on the nanofilament-supported copolymer brushes was approximately 65 times greater than that on smooth wafer-supported copolymer brushes.     

Surface-enhanced Raman scattering of a series of n-hydroxybenzoic acids (n = P, M and O) on the silver nano-particles

Surface-enhanced Raman scattering (SERS) spectra of a series of n-hydroxybenzoic acids (n-HBA, n = P, M and O) adsorbed on the silver nano-particles were studied, respectively, in the silver colloidal solution and on the dried silver-coated filter paper. On the same substrate, the different molecules' SERS spectra were different, while on the different substrates the same molecules' SERS spectra were also different. Significant changes were found in the SERS spectra of PHBA molecules adsorbed on the two substrates, and the changes found in MHBA's spectra on two substrates were next to PHBA's, while almost no changes were found in the spectra of OHBA molecules. Moreover, it was found, on the filter paper, that the SERS spectra of the same molecules would change with the coverage density of the silver nano-particles. The analyses showed that the origins of these changes were the different adsorption behavior of molecules adsorbed on the silver nano-particles. Because in these three molecules the relative positions of the carboxyls and hydroxyls on the benzenes are different, the adsorption behaviors of these three molecules adsorbed on the silver surfaces are also different. The experimental results suggest that the surface characteristic of the substrate and the surface configuration of the adsorbate could exert a great influence on the adsorption behavior of the adsorbates on the substrates.     

用离子交换/ICP-AES联用技术研究溶液中配合铝的形态及分布

以阳离子交换微柱分离与ICP-AES检测联用技术为分离/检测手段,系统地研究了不同配体配合物体系中铝的形态及其分布.当pH=6.0时,溶液中非稳定态单核铝被微柱所保留,而稳定态配合铝直接从微柱中流出.所选择的研究体系分别为:Al-氟化物(Al-Fluoride),Al-磷酸盐(Al-Phosphate),Al-柠檬酸盐(Al-Citrate),Al-草酸盐(Al-Oxalate)及Al-EDTA.在确定的pH值条件下,研究了不同的摩尔比[n(Al)/n(配合剂)]对铝的形态分布的影响,得到了一些对实际应用有指导意义的规律性结论.     

Hybrid gold-nanoparticle-cored conjugated thiophene dendrimers: synthesis, characterization, and energy-transfer studies

A series of hybrid Au-nanoparticle-dendrimer materials: nanoparticle-cored thiophene dendrimers (NCTDs) were synthesized, characterized, and investigated for their energy-transfer properties. These hybrid nanoparticles were obtained by the simultaneous and in situ reduction of gold(III) chloride and self-assembly of the thiol-containing thiophene dendritic ligands. The dendron ligands were radially attached to the gold nanoparticles and were analyzed by TEM, UV/Vis, (1)H NMR, and FTIR spectroscopies. The solution fluorescence of the attached thiophene dendrons are quenched progressively. Both alkyl-chain length and dendron size have significant influence on the energy-transfer efficiency, as well as on core sizes and size distribution of the Au nanoparticles. In spite of the phenomenon's dependence on nanoparticle size, the energy transfer generally follows the 1/d(2) distance dependence. Single NCTD nanoparticles were also adsorbed on highly ordered pyrolytic graphite (HOPG) and uniform aggregates were observed on mica flat substrates.     

大黄药材指纹图谱研究

采用高效液相色谱法,Hypersil ODS柱,甲醇-1．0%冰醋酸为梯度流动相,研究了大黄的指纹图谱,其中大黄酸、大黄素、大黄酚、大黄素甲醚、芦荟大黄素作为为参照物,并对它们进行了含量测定．检测波长：430nm．共找出了23个共有峰,其中的5个峰是参照物,12个样品之间的相似度在90％以上．样品处理方法简单,研究所得的大黄指纹图谱稳定性、重复性好,可作为大黄药材的特征指纹图谱．     

The chiral effects on the responses of osteoblastic cells to the polymeric substrates

In order to study the chiral effects of polylactides on responses of osteoblastic cells, poly(l-lactide) (PLLA), poly(d-lactide) (PDLA), poly(dl-lactide) (PDLLA) and the stereocomplex of PLLA and PDLLA (SC) films with different stereoforms were prepared. The surface properties of the four polylactide films were tested and the osteoblastic ROS 17/2.8 cells were cultured on the films. The protein adsorption behaviors of fibrinogen and bovine serum albumin on films were studied. The cell proliferation, total protein amount, DNA content and alkaline phosphatase activity of osteoblastic ROS 17/2.8 cells were evaluated. The results showed that the protein adsorption was dependant on the type of proteins. The observation of cell morphologies revealed that the PDLA film provide an unfavorable surface for cell attachment. The total protein amount, DNA content and ALP activity were closely related to the stereoforms of polylactide films. All the levels of total protein amount, DNA content and ALP activity of ROS 17/2.8 cells on PDLA film were decreased. The racemic stereocomplex of PLLA and PDLA showed relatively higher positive effects on both cell growth and proliferation.     

Distribution of olfactory marker protein on a tissue section of vomeronasal organ measured by AFM

Distribution of olfactory marker protein (OMP) on a tissue section of vomeronasal organ (VNO) was successfully measured by atomic force microscopy (AFM). Anti-OMP antibodies were covalently crosslinked with the tip of the AFM and were used as a probe to observe the distribution of OMP on a tissue section. First, force measurements were performed using a glass surface on which OMP was covalently immobilized to verify the success of tip modification. Clear differences of interaction forces were observed between a specific pair and the control experiments, indicating that the tip preparation succeeded. Next, distributions of OMP on the tissue section were observed by AFM and were compared with immunohistochemical observations. For large scale observation, a microbead was used as a probe in the AFM measurements. The results of the AFM measurements were well overlapped with that of immunohistochemistry, confirming the reliability of our method. A mapping of the AFM measurement with high resolution was also successfully obtained, which showed an advantage of the application of the AFM measurement in analysis of proteins on the tissue section.     

Covalently immobilized choline oxidase and cholinesterases on a methacrylate copolymer for disposable membrane biosensors

Bienzymatic sensors for the determination of esters of choline were prepared by covalent co-immobilization of cholinesterases and choline oxidase on polymer membranes, obtained by radiation-induced copolymerization of 2-hydroxyethyl methacrylate and glycidyl methacrylate at low temperature. Optimization of the covalent attachment of choline oxidase and acetyl-or butyrylcholinesterase to copolymer was explored. The enzyme-modified polymers were applied on platinum electrodes to form amperometric sensors, based on the electrochemical detection of enzymatically developed hydrogen peroxide. Acetyl-, acetylthiobutyryl-, and butyrylthiocholine contents in standard solutions were measured, and linear calibration curves were determined. Temperature and pH effects on the electrochemical response are described.     

Soft,Oxidative Stripping of Alkyl Thiolate Ligands from Hydroxyapatite‐Supported Gold Nanoclusters for Oxidation Reactions

A strategy for the mild deprotection of alkyl‐thiolated (6‐mercaptohexanoic acid, MHA, and 3‐mercaptopropanoic acid, MPA) gold nanoclusters (Au NCs) supported on hydroxyapatite (HAP) has been developed by employing a peroxide (tert‐butyl hydroperoxide, TBHP, or hydrogen peroxide, H₂O₂) as an oxidant. The thiol ligands on the supported Au NCs were removed after oxidation, and the size and integrity of the supported clusters were well‐preserved. The bare gold clusters on HAP after removal of the ligands were catalytically effective for the epoxidation of styrene and the aerobic oxidation of benzyl alcohol. These two reactions were also investigated on calcined Au NCs that were supported on HAP for comparison, and the resulting Au NCs that were prepared by using this new strategy showed superior catalytic activity.     

High-performance liquid chromatographic separation of the enantiomers of organophosphorus pesticides on polysaccharide chiral stationary phases.

High-performance liquid chromatographic separation of the individual enantiomers of 12 organophosphorus pesticides (OPs) was obtained on polysaccharide enantioselective HPLC columns using alkane-alcohol mobile phase. The OP pesticides were crotoxyphos, dialifor, fonofos, fenamiphos, fensulfothion, isofenphos, malathion, methamidophos, profenofos, crufomate, prothiophos and trichloronate. The enantiomers of fenamiphos, fensulfothion, profenofos and crufomate were separated on CHIRALPAK AD; the enantiomers of fenamiphos were also separated on CHIRALPAK AS; the enantiomers of methamidophos, crufomate and trichloronate were separated on CHIRALCEL OD; the enantiomers of crotoxyphos, dialifor, fonofos, malathion, prothiophos and trichloronate were separated on CHIRALCEL OJ; and the enantiomers of isofenphos were separated on CHIRALCEL OG. Baseline or partial separation of the enantiomers of six of these OP pesticides was obtained on CHIRALCEL OJ. In continued method development, the separation of the enantiomers of the 12 OPs was investigated more extensively on CHIRALCEL OJ to determine whether the mobile phase composition, flow-rate and column temperature could be optimized to yield at least partial separation of the enantiomers. Chromatographic conditions were found that gave either baseline or near baseline separations of the enantiomers of the 12 OPs on the CHIRALCEL OJ column.     

减压化学气相沉积法制备规则螺旋状纳米碳管

以硅胶负载的Co纳米颗粒为催化剂,在低流量的减压体系中通过化学气相沉积法制备了规则螺旋状的纳米碳管.通过TEM和HRTEM研究了螺旋碳管的形貌、尺度分布以及管身、曲面和节点处的晶型;讨论了催化剂制备中pH值对催化剂的尺寸、规则程度和存在形态以致对螺旋碳管产量、管径厚度以及螺旋管的相对比例的影响;此外,还分析了反应压力对碳管生长的影响.     

On the surface coverage of alumina by molybdenum-oxide in nickel - and cobalt-promoted MoOx/Al2O3 catalysts

The chemisorption of CO₂ has been studied on alumina-supported Co-and Ni-promoted molybdenum-oxide (CoMo, NiMo) and, besides those, on monometallic Co and Ni. Chemisorbed amounts on the monometallic samples were equal to that on the alumina support. XPS measurements were performed with the NiMo and Ni samples. The amounts of surface Mo-and Al-ions were calculated. It could be established that molybdenum oxide forms a near to monomolecular layer on the Co-and Ni-promoted molybdena-alumina samples.     

Multiple genotyping based on multiplex PCR and microarray

The genetic variability has obtained more and more attention in the process of diagnosis and treatment of tumors.Herein,we have described a multiple genotyping method based on magnetic enrichmentmultiplex PCR (MEM-PCR) and microarray technology.Monodisperse magnetic beads were fabricated and modified with streptavidin.Four loci on two genes (M235T and A-6G loci on AGT gene,A1298C and C677T loci on MTHFR gene) were selected to study single nucleotide polymorphisms (SNP).Target sequences of these SNP loci were amplified using Cy3-labeled primers through multiplex PCR in one tube after the templates were enriched and purified by functional magnetic beads (MB).Four pairs of NH₂-labeled probes,corresponding to each locus,were fixed on CHO-modified glass slide by covalent binding.Hybridization between target sequences and probes was performed under suitable conditions.The spotting locations on microarray and the ratio of fluorescence intensity,produced by different loci,were used to distinguish the SNP genotypes.Finally,three of gastric cancer samples were collected and genotyping analysis for these four SNP loci was carried out successfully simultaneously by this method.     

Using HPTLC/DESI-MS for peptide identification in 1D separations of tryptic protein digests

Desorption electrospray ionization mass spectrometry (DESI-MS) was investigated as a method to detect and identify peptides from tryptic digests of cytochrome c and myoglobin separated on ProteoChrom HPTLC Silica gel 60 F(254s) plates and ProteoChrom HPTLC Cellulose sheets. Full-scan mass spectra and data-dependent tandem mass spectra were acquired in separate plate scans and used to identify peptide ions. Peptide distributions along the development lane were mapped for each separated protein digest. Signal levels ranged over several orders of magnitude. In general, highest signal levels were obtained for the peptides with the highest R (f) values on a plate, while peptides with very low R (f) values were often not detected. Sequence coverages for cytochrome c were 58% for the digest separated on the silica gel plate and 72% for the separation on the cellulose sheet; myoglobin sequence coverages were 62% and 68% on silica gel and cellulose, respectively. Weak correlations between peptide hydrophilicity and R (f) values on the silica gel and cellulose plates were found, with the more hydrophilic peptides having lower R (f) values.     

固定化木瓜蛋白酶的制备和性质研究

多孔硅球固定化木瓜蛋白酶具有热增活性 .本文在前文研究的基础上 ,用载体交联法制备了甲壳胺固定化木瓜蛋白酶和纤维素固定化木瓜蛋白酶 .考察了固定化pH值、戊二醛浓度和给酶量对固定化木瓜蛋白酶活力的影响 .研究了固定化木瓜蛋白酶的性质 ,特别是热稳定性和耐热性 ,并与溶液酶和多孔硅球固定化木瓜蛋白酶进行了比较 .所制得的甲壳胺固定化木瓜蛋白酶和纤维素固定化木瓜蛋白酶的最适反应温度均达到了 80℃ ;90℃温育 1h后固定化酶的活力保持在 95 %以上 ;70℃温育处理 5h和 6h后固定化酶的活力也仍能保持在 90 %以上 .固定化木瓜蛋白酶的热稳定性和耐热性得到了显著提高     

Effects of peak anomalies with the hydrophilic or hydrophobic properties of reservoirs during serial injection on a capillary electrophoresis microchip

Several anomalies, e.g., in peak shape, migration time, and baseline drift, all due to pressure-driven backflow, were previously reported to occur during serial injection on capillary electrophoresis (CE) chips. Since these anomalies were worse for polydimethylsiloxane (PDMS) microchips than for glass microchips, reproducible data on PDMS microchips were difficult to obtain. In this paper, we found that these problems were affected by the hydrophilic or hydrophobic properties of the reservoirs on the microchip and demonstrated that these anomalies were reduced by converting the hydrophobic properties of the reservoirs on the PDMS microchip into hydrophilic ones. Thus, compared with hydrophobic reservoirs, hydrophilic reservoirs were suitable for the formation of a stable plug. Several chip designs were suggested to reduce these pressure-driven backflows.