Novel Cell Permeable Polymers of N-Substituted L-2,3-Diaminopropionic Acid (DAPEGs) and Cellular Consequences of Their Interactions with Nucleic Acids

The present study aimed to synthesize novel polycationic polymers composed of N-substituted L-2,3-diaminopropionic acid residues (DAPEGs) and investigate their cell permeability, cytotoxicity, and DNA-binding ability. The most efficient cell membrane-penetrating compounds (O2Oc-Dap(GO2)_n-O2Oc-NH₂, where n = 4, 6, and 8) showed dsDNA binding with a binding constant in the micromolar range (0.3, 3.4, and 0.19 µM, respectively) and were not cytotoxic to HB2 and MDA-MB-231 cells. Selected compounds used in the transfection of a GFP plasmid showed high transfection efficacy and minimal cytotoxicity. Their interaction with plasmid DNA and the increasing length of the main chain of tested compounds strongly influenced the organization and shape of the flower-like nanostructures formed, which were unique for 5/6-FAM-O2Oc-[Dap(GO2)]₈-O2Oc-NH₂ and typical for large proteins.     

PRESSURE DISTRIBUTION IN THE AIR-SPARGED HYDROCYCLONE

ＰＲＥＳＳＵＲＥＤＩＳＴＲＩＢＵＴＩＯＮＩＮＴＨＥＡＩＲ－ＳＰＡＲＧＥＤＨＹＤＲＯＣＹＣＬＯＮＥ￥Ｃｈｕ，Ｌｉａｎｇｙｉｎ；ＬｕｏＱｉａｎ（ＭｉｎｅｒａｌＥｎｇｉｎｅｅｒｉｎｇＤｅｐａｒｔｍｅｎｔ，ＮｏｒｔｈｅａｓｔｅｒｎＵｎｉｖｅｒｓｉｔｙ，Ｓｈｅ...     

Flow field in air-sparged hydrocyclone

ＦＬＯＷＦＩＥＬＤＩＮＡＩＲ－ＳＰＡＲＧＥＤＨＹＤＲＯＣＹＣＬＯＮＥＣｈｕ，Ｌｉａｎｇｙｉｎ；Ｌｕｏ，Ｑｉａｎ（ＭｉｎｅｒａｌＥｎｇｉｎｅｅｒｉｎｇＤｅｐａｒｔｍｅｎｔ，Ｐ．Ｏ．Ｂｏｘ１３９ＮｏｒｔｈｅａｓｔｅｒｎＵｎｉｖｅｒｓｉｔｙ，Ｓｈｅｎｙａｎ...     

Ti－24Al－11Nb腐蚀疲劳断口形貌的研究

Ｔｉ－２４Ａｌ－１１Ｎｂ腐蚀疲劳断口形貌的研究张跃，褚武扬，王燕斌，肖纪美（北京科技大学北京１０００８３）１引言对Ｔｉ－２４ＡＩ－１１Ｎｂ合金的断裂特征和断口形貌已进行了较多的研究［“］．在３００ｏＣ的氢气中该合金能发生氢致开裂，其断口形貌与过载断口...     

VAc/AA改性的VAE乳液高速接嘴卷烟胶的研制

介绍了VAc/AA改性的VAE乳液高速接嘴卷烟胶的制备方法。研究了各种因素对胶粘剂性能的影响。结果表明 :VAc/AA用量增加 ,VAE乳液的粘接性能增强。选择与VAE乳液相适应的乳化剂和控制适宜的pH值 ,可以增加VAE乳液的稳定性。采用滴加引发剂和混合单体的方法 ,可以避免过速反应产生及大粒径胶粒生成     

Preparation of Protein-Stabilized β-Carotene Nanodispersions by Emulsification–Evaporation Method

This work was initiated to prepare protein-stabilized β-carotene nanodispersions using emulsification–evaporation. A pre-mix of the aqueous phase composed of a protein and hexane containing β-carotene was subjected to high-pressure homogenization using a microfluidizer. Hexane in the resulting emulsion was evaporated under reduced pressures, causing crystallization and precipitation of β-carotene inside the droplets and formation of β-carotene nanoparticles. Sodium caseinate (SC) was the most effective emulsifier among selected proteins in preparing the nanodispersion, with a monomodal β-carotene particle-size distribution and a 17-nm mean particle size. The results were confirmed by transmission-electron microscopy analysis. SC-stabilized nanodispersion also had considerably high ζ-potential (−27 mV at pH 7), suggesting that the nanodispersion was stable against particle aggregation. Increasing the SC concentration decreased the mean particle size and improved the polydispersity of the nanodispersions. Nanodispersions prepared with higher β-carotene concentrations and higher organic-phase ratios resulted in larger β-carotene particles. Although increased microfluidization pressure did not decrease particle size, it did improve the polydispersity of the nanodispersions. Repeating the microfluidization process at 140 MPa caused the nanodispersions to become polydisperse, indicating the loss of emulsifying capacity of SC due to protein denaturation.     

Effects of enzymes and gamma irradiation on the tensile strength and morphology of poly(p-dioxanone) fibers

The objective of this study was to examine how and to what extent a new degradable polymeric fiber, poly(p-dioxanone), used as a surgical suture material, degrades in the presence of enzymes and after γ-irradiation. The degradation of the fiber was studied mechanically using an Instron and morphologically by SEM. Both esterase and trypsin enzymes and their corresponding buffer controls were used. The fibers were γ-irradiated at the dosages ranging from 0 to 20 Mrad, immersed in the solution for up to 70 days, and then removed for tensile strength and morphological examinations. It was found that γ-irradiation alone lowered the tensile strength of PDS fibers and made them more susceptible to hydrolysis. Esterase and trypsin did not accelerate the hydrolytic degradtion of this fiber to any significant level. Both γ-irradiation and enzymes influenced the gross morphological characteristic of PDS fibers when they were subjected to hydrolysis. The most important morphological observations were the formation of surface cracks and chips on the fibers and the subsequent peeling of the chips. Enzyme-treated PDS fibers exhibited similar morphological findings but the size of the chips was smaller. The morphological observations of PDS fibers were consistent with the tensile strength data.     

The mechanism of color reversion in soybean salad oil

An enzymatic reaction might be the major cause of color reversion in soybean oil. During the soybean flaking process, enzymatic reactions take place to convertγ-tocopherol to 5-(tocopheryloxy)-γ-tocopherol (γ-TED), and then further convertγ-TED to the precursors which are the cause of color reversion. The variations ofγ-tocopherol andγ-TED contents in soybean oil are accompanied by an inverse change in the precursors’ concentration. Therefore, the contents ofγ-tocopherol orγ-TED in crude soybean oil could be used as an index for predicting the color quality (color reversion) of soybean salad oil. Almost all the precursors (such as tocored) were converted to color-reverted substances under catalysis after bleaching treatment, and they were converted back to the precursors during deodorization. Those precursors might be gradually reconverted into the color reverted substances during storage to cause the color reversion in soybean salad oil.     

Hydrolytic degradation of polyglycolic acid: Tensile strength and crystallinity study

The hydrolytic degradation of polyglycolic acid (PGA) was studied by examining the changes of tensile strength and the level of crystallinity of the suture material. It was found that the breaking stress decreased from 6.369 × 10^?1 at 0 day to 3.97 × 10^?3 Newton/Tex at 49 days. The sigmodial shape of the stress–strain curves gradually disappeared with increase in the duration of in vitra degradation. The endpoint titration method used to assess the degree of degradation beyond the period of measurable tensile strength showed that the percent of PGA degraded were 42, 56, and 70% at 49, 60, and 90 days, respectively. The level of crystallinity of PGA at various durations of degradation exhibited an initial increase in the degree of crystallinity from 40% at 0 day to an upper limit of 52% at 21 days, then gradual decrease to 23% at 90 days. This observation is essentially parallel to hydrolysis of cellulose and polyethylene terephthalate. The concept of microfibrillar structure of fibers provides the basis for the proposed degradation mechanism of PGA in vitro. It is believed that degradation proceeds through two main stages which are different in rate of degradation.     

A rheological model for iron oxide suspensions

We have examined the rheological properties of a Co-adsorbed γ-Fe₂O₃ magnetic suspension with polyurethane (PU) as a binder and methyl ethyl ketone (MEK) or cyclohexanone (CH) as a solvent. A Haake RV20 viscometer was used to measure the suspension viscosity and the vane method was adopted to determine the fluid yield stress. A rheological model which can be viewed as a combination of the Casson model and the Bingham model is proposed to describe the suspension viscosity. The effects of temperature, particle content, and binder concentration are included in the model.