Preparative size exclusion chromatography combined with detergent removal as a versatile tool to prepare unilamellar and spherical liposomes of highly uniform size distribution

Detergent removal from mixed micelles was combined with preparative size exclusion chromatography (SEC) on Sephacryl S 500 HR to prepare unilamellar and spherical liposomes of defined sizes between 50 and 100 nm with a very narrow size distribution (RSD of vesicle diameter between 13% and 25%). For neutral phosphatidylcholine and negatively charged phosphatidylcholine/phosphatidylglycerol liposome preparations, efficient sizing at the preparative scale was demonstrated by analyzing isolated SEC peak fractions with cryo-transmission electron microscopy and dynamic light scattering. The number-weighted average vesicle diameters obtained using both methods are in very good agreement for fractions of low polydispersity.     

High-temperature two-dimensional liquid chromatography of ethylene-vinylacetate copolymers

Temperature rising elution fractionation hyphenated to size exclusion chromatography (TREF × SEC) is a routine technique to determine the chemical heterogeneity of semicrystalline olefin copolymers. Its applicability is limited to well crystallizing samples. High-temperature two-dimensional liquid chromatography, HT 2D-LC, where the chromatographic separation by HPLC is hyphenated to SEC (HPLC × SEC) holds the promise to separate such materials irrespective of their crystallizability. A model blend consisting of ethylene-vinyl acetate (EVA) copolymers covering a broad range of chemical composition distribution including amorphous and semicrystalline copolymers and a polyethylene standard was separated by HT 2D-LC at 140 °C. Both axes of the contour plot, i.e. the compositional axis from the HPLC and the molar mass axis from the SEC separation were calibrated for the first time. Therefore, a new approach to determine the void and dwell volume of the developed HT 2D-LC instrument was applied. The results from the HT 2D-LC separation are compared to those from a cross-fractionation (TREF × SEC) experiment.     

尺寸排阻-反相液相色谱-质谱联用技术在大鼠肾脏翻译后修饰蛋白质鉴定中的应用

LC-MS联用技术在蛋白质组学研究中具有重要的作用,但是在复杂的生物体系中,由于样品的高度复杂性和其中蛋白质含量的巨大差异,执行全面且无倾向的蛋白质组分析是一项挑战。因此,在液相色谱分离中采用基于不同原理的色谱分离方法来降低蛋白质样本的复杂度,并对微量蛋白质进行富集,对后续采用质谱方法进行信息的采集和深入分析至关重要。在这里我们开发了一种基于尺寸排阻色谱(SEC)与反相液相色谱(RPLC)结合的新方法来进行复杂体系蛋白质的分离和鉴定,特别是对于微量蛋白质的分析。首先使用SEC对蛋白质进行分离和富集,并酶解成多肽,再通过RPLC-MS联用的方法对酶解后的多肽进行分离和鉴定。结果显示使用上述方法可以有效降低蛋白质样本的复杂度,并有效提高微量蛋白质的鉴定能力,可从大鼠肾脏鉴定出23621个肽段及1345个蛋白质,比常规的二维强阳离子交换-反相液相色谱法(2D SCX-RPLC)鉴定到的肽段及蛋白质分别多出69%及27%。此外,该方法对肾脏翻译后修饰(PTM)蛋白质的鉴定显示出更多的优势,翻译后修饰的多肽鉴定率显著增加,特别是磷酸化肽段的鉴定效率可达到靶向富集策略的水平。在此展示的SEC-RPLC-MS可以更好地了解蛋白质翻译后修饰对肾脏的影响,最终将有助于增加我们对正常的生理性肾功能以及病理过程机制的理解。     

分离技术在新型冠状病毒研究和防疫检测中的应用

新型冠状病毒肺炎(COVID-19)疫情的爆发给世界公共卫生安全带来前所未有的挑战.随着新型冠状病毒(SARS-CoV-2)相关研究的不断深入,众多分析检测技术相继被应用,推动了病毒检测、疫苗和创新疗法的研发,从而使疫情早日得到控制.分离技术作为生命科学、医学、药学领域的关键技术,操作简单,分离效率高,选择性强,在新型...     

Comparison of the molecular dimensions of di-alkyl and aryl-alkyl-substituted polysilanes in solution using SEC/LS

Polysilanes provide an opportunity for exceptional control of the chain hindrances to rotation through the choice of substituents on each backbone silicon. Two alkyl substituents on each silicon result in a large characteristic ratio of at least 19 for poly (di-n-hexylsilane), determined by extrapolation of intrinsic viscosities. Bulky aromatic substituents provide even more hindrance to backbone rotations, and can be expected to result in a more extended polymer chain. Direct measurement of the dimensions of these polymers by scattering techniques has been limited by the small quantities available, and by the polydispersity of samples. The recent introduction of light-scattering detectors for size exclusion chromatography enables the simultaneous measurement of light scattered at as many as 15 scattering angles as the fractionated polymer elutes from the column. Determination of both M and the root-mean-square radius of gyration R_g of narrow fractions eluting from a column allows determination of the R_g M relation over as much as a decade in M with less than a milligram of sample. Values of R_g and M across the distribution have been determined for alkyl and aryl substituted polysilanes with this technique. Estimation of R_g,0/M unperturbed by long-range interactions is made by an extrapolation procedure. The dependence of R_g,0 on M across the distribution is compared among the different substituents and with other measurements reported for these polymers. © 1994 John Wiley & Sons, Inc.     

Short chain branching profiles in polyethylene from the Phillips Cr/silica catalyst

SEC and on‐line Fourier transform infrared spectroscopy analysis have been combined to study branching profiles from the Phillips Cr/silica catalyst. For the first time, catalyst and reactor variables have been shown to affect the overall level and distribution of branches in polyethylene copolymers. Branching profiles from various chromium catalysts have been shown to vary from highly concentrated in the low MW end, to uniformly distributed over all of the MW range. Activation temperature and the presence of titania were highly influential. These observations, which have been used to gain insight into the chemistry of Cr/silica, explain much of the catalyst behavior that has for decades been used to optimize polymer properties. Trends in ESCR, impact resistance, and other physical characteristics, which were long attributed to changes in MW distribution, can now be seen to also be due in large part to changes in the branching profile. This knowledge should be of value in designing future resins. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3135–3149, 2007     

多检测GPC/SEC技术在高分子表征中的应用 II.C_(70)/PS共聚物的表征

用ＳＥＣ／ＲＩ／ＲＡＬＬＳ／ＤＶ 三检测技术表征了Ｃ７０／ＰＳ 共聚物。解决了用传统ＳＥＣ／ＲＩ不能解释的现象，提出了Ｃ７０ － ＰＳ共聚物的大致结构。结果表明Ｃ７０ － ＰＳ共聚物／ＴＨＦ体系不符合普适标定。     

On the anionic homo‐ and copolymerization of ethyl‐ and butyl‐2‐cyanoacrylates

Ethyl‐(ECA) and butyl‐2‐cyanoacrylate (BCA) monomers of high purity and acidic stabilization were synthesized and anionically polymerized to homo‐ and copolymers in two different ways: by piperidine‐catalyzed bulk polymerization leading to transparent, brittle films (method A) and by polymerization in aqueous medium in the presence of sodium bicarbonate to obtain white powders (Method B). The molecular structure of the synthesized monomers, homopolymers and copolymers were corroborated by spectral methods. The polymers were studied further by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), size exclusion chromatography (SEC) and proton nuclear magnetic resonance (¹H NMR). Controlling the composition of the monomer feed and the way the polymerization was performed, it was possible to obtain phase separated or homogeneous cyanoacrylate copolymers with glass transitions varying between the T_g of polyECA and that of polyBCA. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5142–5156, 2008     

美国PRMS与SEC两种油气储量准则差异分析.

为有效区别和准确使用美国PRMS和SEC两种储量评估准则,通过对两种储量分类体系的分析对比,明确了两种准则的相同点和不同点,得到两种准则都要求具有“已发现、可开采、商业性和经济剩余量”的4个要素,SEC在PRMS的基础上不仅评估证实储量,也选择性披露概算储量和可能储量。通过8个方面的分析对比,二者在流体界面确定、断层上下盘储量级别定义、PUD的外推范围、类比油藏、可靠技术、5年PUD规划、经济性、油价及成本等8个方面的界定与要求存在差异与不同。在价值评估方面,SEC按目前的经济条件进行经济评估,强调储量的经济生产能力和公司的最低收益; PRMS则以预测经济条件为基础进行经济评估,强调储量的商业价值,侧重于公司的投资回报。     

On-line measurement of the RMS radius of gyration and molecular weight of polyimide precursor fractions eluting from a size-exclusion chromatograph

The recent introduction of multiangle light-scattering detectors for size-exclusion chromatography has made possible the measurement of the root mean square radius of gyration (R_g) and molecular weight (M) of polymer fractions eluting from a size-exclusion chromatography column. The characterization of the dimensions of a polymer may be accomplished with only a few milligrams. The dimensions of a polyimide precursor prepared by the condensation of the meta-diethyl ester of pyromellitic dianhydride with para-phenylene diamine have been measured with this technique. The dependence of R_g on M across the distribution is compared with that predicted for a freely rotating chain, and with other similar polymers measured with hydrodynamic techniques.