Global fit and structure optimization of flexible and rigid macromolecules and nanoparticles from analytical ultracentrifugation and other dilute solution properties

The calculation of hydrodynamic and other solution properties from structural information (size and shape or flexibility) of macromolecules and nanoparticles is feasible thanks to existing theories and computational tools. Here we review our recent advances in the inverse problem of extracting structural information from those properties. The concepts of equivalent radii and ratios of radii are particularly useful in global-fitting structural analysis, when one has to treat simultaneously with various properties, eventually for a series of samples. Based on the equivalent radii or their ratios, we define target functions that measure the adequacy of a given structure to fit a set of experimental properties. Structural determination is carried out by minimization of those target functions. We review a variety of examples. Some of them refer to the simple, yet important models like ellipsoids, cylinders and wormlike chains, whose structure is determined by optimization of the model parameters. In other, more complex cases, properties are calculated with computational tools like programs in the HYDRO suite. We have devised other tools to make the structure optimization from the results of those calculations in a quite direct, simple and systematic manner.     

裂褶菌深层培养及多糖测定

为了深层培养裂褶菌Schizophyllum commune Fr.产生多糖,对产多糖的适宜培养基,最佳时间,高产菌株进行了研究。从南京灵谷寺及南京大学校园生长的裂褶菌子实体分离到3株产多糖的裂褶菌菌株,编号南大835,南大843,南大853。对南大843用6种不同培养基进行深层培养,测定和比较了多糖和菌丝产量,其结果表明黄豆粉葡萄糖液体培养基是适于裂褶菌合成多糖的培养基,能培养出密集、白色、均匀的菌球和丰富的多糖。其组成为(g/L):葡萄糖30,黄豆粉5,酵母膏2,KH_2PO_4 1,MgSO_4·7H_2O0.5。pH5.5。最适发酵条件:pH5—5.5,温度26—28℃,振速:100—110次/分,当pH降至4.9—4.7,残糖量在1%以下,5—6天可终止发酵。在培养6天的浓缩滤液中加入等体积的95%乙醇后大量白色粘稠、纤维状的多糖被沉淀下来。在上述发酵条件下,3个菌株比较结果,南大853能明显提高多糖产量,6天的培养液中多糖量可达5.5—6g/L,南大843和南大835分别是5g/L和2.8g/L。     

裂褶菌胞内多糖的分离纯化鉴定及其性质

裂褶菌菌丝体用热水提取,乙醇沉淀,Sevag法脱蛋白,逆向流水透析,得胞内多糖粗品,经Sephadex A-50、Sephadex G-200柱层析纯化,得胞内多糖纯品,称SPG。纯度经纸层析、Sephadex G-200柱层析、高效液相色谱分析、聚丙烯酰胺凝胶电泳测定,结果表明SPG为单一均匀组分。 SPG水解物经纸层析、薄层层析分析证实它是由葡萄糖组成的一种葡聚糖结构,SPG的部分水解、酶解、红外光谱、核磁共振氢谱分析表明具有β(1→3),β(1→6)糖苷键。凝胶过滤法测定SPG的分子量约为10万。     

Rod-like architecture and helicity of the poly(C)/schizophyllan complex observed by AFM and SEM

Microscopic studies of the complex between poly(C) and schizophyllan (SPG), employing both AFM and SEM, revealed that the complex takes the same rod-like architecture on the mica surface as those of the renatured SPG and the original triple helix of SPG, indicating that the complex also has a helical structure. The SEM observations showed the helical pattern on the rod surface, only when the sample was metal shadowed. The pitch evaluated from the image is comparable with that obtained from crystallographic data. The ability to visualize the helical structure can be explained from the hypothesis that the platinum grains may assemble on the sample using the molecular surface of the SPG (or complex) as the template.     

Naphthalene-hydrophobized β-1,3-glucan nanogel for doxorubicin delivery to immunocytes

A water soluble β-1,3-glucan schizophyllan (SPG) can be recognized by an immunocyte receptor called dectin-1. When we introduced naphthalene into the side chain of SPG (nSPG), it formed nanogel by physical cross-link and gained capability to ingest hydrophobic compounds such as doxorubicin. Our in vitro assay revealed that this nanogel can be used as specific delivery of anti-cancer drugs to immunocytes.