Effect of temperature on adsorption of mixtures in porous materials

The effect of temperature on the adsorption of a simple mixture (Ar/Kr) in disordered porous materials is investigated by means of molecular simulation. In the larger mesopores of porous silica glasses, capillary condensation occurs upon decreasing the temperature. At temperatures above the capillary condensation temperature, Kr is preferentially adsorbed at the pore surface and Ar adsorption occurs in regions of low Kr density. For temperatures below the capillary condensation temperature, Ar density surprisingly increases as temperature increases, the behaviour that is consistent with an over-solubility effect. In contrast, in the disordered sub-nanoporous carbon, filling of the pores occurs in a reversible and continuous way upon decreasing the temperature, owing to the small size and amorphous shape of the pores. These results show that the crossover between capillary condensation and continuous reversible filling observed for pure fluids in pores also exists for mixtures. We also show that the Kr selectivity exhibits a minimum in the disordered porous silica that is located at the capillary condensation temperature. In contrast, in the disordered porous carbon where no capillary condensation occurs, the selectivity decreases monotonically with increasing the temperature. These results shed light on low-temperature adsorption of mixtures confined in porous materials and provide a guide to design efficient phase separation processes.     

大孔吸附树脂分离纯化地黄中梓醇工艺的研究

利用大孔吸附树脂分离提取地黄中梓醇。以地黄粗提液中梓醇含量为指标,高效液相色谱(HPLC)为含量测定方法,考察九种不同极性大孔吸附树脂对梓醇的吸附和解吸附性能,筛选出最佳树脂D101进行分离实验。结果表明,D101大孔吸附树脂的静态吸附容量为69.2mg/g干树脂,其吸附等温线符合Langmuir和Freundlich吸附等温式。采用5%乙醇作为洗脱剂,洗脱液减压浓缩后进行硅胶柱层析分离,氯仿：甲醇（8：2）梯度洗脱得到梓醇单体,纯度达90%以上,梓醇得率为6%。     

Porous graphitic carbon shows promise for the rapid chromatographic analysis of polar drug metabolites

A rapid and simple HPLC method has been developed and used to separate the polar metabolic conjugates of AZT, chloramphenicol, and β-estradiol based upon the use of porous graphitic carbon. The HPLC system is sufficiently selective to resolve the polar drug conjugates from their parent compounds and from endogenous material present in urine. The compounds are separated, without the need for sample pretreatment or gradient elution, on a porous graphitic carbon (Hypercarb) column using aqueous trifluoroacetic acid modified with tetrahydrofuran as the mobile phase. Porous graphitic carbon exhibits a novel mechanism of retention towards these very polar substances, which are unretained under reversed-phase conditions on alkyl-bonded silica phases.     

Chemically modified porous silica gel as a bioadsorbent and a biocatalyst.

Aminopropyl silica gel was prepared from porous silica gel by reaction with γ-aminopropyltrimethoxysilane in toluene and was used for immobilizing chymotrypsin (EC 3.4.4.5) and human serum albumin. Immobilized chymotrypsin was used for the resolution of N-acetyl-dl-phenylalanine and immobilized human serum albumin was used for the purification of goat anti-human serum albumin. Epoxy silica gel, prepared by reaction of porous silica gel with γ-glycidoxypropyltriethoxysilane, was coupled with m-aminobenzamidine and the resulting matrix was used for trypsin purification.     

Improved production of teicoplanin using adsorbent resin in fermentations

AIMS: To use adsorbent resins in fermentations to eliminate toxic effects on growth, reduce feedback repression of production and assist in recovery of teicoplanin. METHODS AND RESULTS: An adsorbent resin was added to the culture broth for the adsorption of teicoplanin. Amberlite XAD-16, Diaion HP-20, charcoal and silica gel were investigated as adsorbent resins. The adsorbed teicoplanin was extracted from the resin by 80% methanol after fermentation. Antibiotic activity was quantified by the disc-agar diffusion assay against Bacillus substilis, and qualitative evaluations were based on HPLC using YMC-Pack ODS-A column. Diaion HP-20 was the most effective adsorbent resin when added at a concentration of 5% (w/v) in the inoculation stage. CONCLUSIONS: Addition of Diaion HP-20 in fermentations eliminated toxic effects on growth and reduced feedback repression of teicoplanin by adsorption. There was a 4.2-fold increase in the quantities of teicoplanin. Addition of adsorbent assisted in the recovery of teicoplanin by reducing the recovery steps. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this study provide useful information for the production of teicoplanin, a glycopeptide antibiotic produced by Actinoplanes teicomyceticus. Addition of adsorbent in fermentation increased productivity of teicoplanin by more than five times.     

Enhanced Sequence Coverage in Tryptic Fragment Analysis by Two-Dimensional HPLC/MS Using a Monolithic Silica Capillary Column

The HPLC/MS system, in which a monolithic silica capillary column is directly connected to an electronspray-ionization mass spectrometer, showed superior performance at high mobile phase linear velocity. A two-dimensional (2D) HPLC/MS system was established, using an ion-exchange particle-packed capillary column at the first dimension and a monolithic silica capillary column at the second dimension. In an analysis of tryptic fragments from bovine serum albumin, an 81% sequence coverage, obtained by the 2D-HPLC/MS system, increased by 23% as compared to a 1D-HPLC/MS system. This 2D-HPLC/MS system using a monolithic silica capillary column should be useful for enhancing sequence coverage of tryptic fragments in proteomics.     

Enhanced sequence coverage in tryptic fragment analysis by two-dimensional HPLC/MS using a monolithic silica capillary column

The HPLC/MS system, in which a monolithic silica capillary column is directly connected to an electronspray-ionization mass spectrometer, showed superior performance at high mobile phase linear velocity. A two-dimensional (2D) HPLC/MS system was established, using an ion-exchange particle-packed capillary column at the first dimension and a monolithic silica capillary column at the second dimension. In an analysis of tryptic fragments from bovine serum albumin, an 81% sequence coverage, obtained by the 2D-HPLC/MS system, increased by 23% as compared to a 1D-HPLC/MS system. This 2D-HPLC/MS system using a monolithic silica capillary column should be useful for enhancing sequence coverage of tryptic fragments in proteomics.     

Selective extraction of polyunsaturated triacylglycerols using a novel ionic liquid precursor immobilized on a mesoporous complexing adsorbent

Mesoporous silica (SBA‐15) synthesized by using Pluronic123 as the structure‐directing template was functionalized by imidazolium‐based ionic liquid precursors. Silver salts were then immobilized onto the supported ionic liquids using the incipient wetness impregnation technique. The separation of unsaturated species was achieved through the reversible and specific interaction between silver ions and carbon–carbon double bonds. This adsorbent was examined for the selective separation of polyunsaturated triacylglycerols (PUTAG) using High Pressure Liquid Chromatography (HPLC) with Evaporative Light Scattering Detection (ELSD) as the quantification methodology. AgBF₄/SBA15 · HPSiOEtIM · PF₆ showed an adsorption capacity for linolenin of about 217 mg adsorbed/gram of sorbent. This adsorbent had good selectivity and a high capacity for the most highly unsaturated triacylglycerol when applied to a mixture of triacylglycerols with varying degrees of unsaturation. Consequently, a stepwise methodology was also developed to increase the recovery of the adsorbed components. This adsorbent retained its selectivity and capacity when recycled up to five times. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Macrokinetics of enzyme sorption on porous beads accompanied by complex formation with an immobilized ligand

A mathematical model has been proposed for enzyme sorption on porous beads accompanied by formation of a stable complex with an immobilized ligand. It has been experimentally verified by using the system trypsin (EC 3.2.21.4) - immobilized bovine basic polyvalent trypsin inhibitor on porous silica gel. The experimental results for kinetics of the non-specific/specific trypsin sorption on a carrier agree with the model. The value of the coefficient of trypsin diffusion in macroporous silica gel was calculated.     

Polystyrene/Divinylbenzene Based Monolithic and Encapsulated Capillary Columns for the Analysis of Nucleic Acids by High‐Performance Liquid Chromatography‐Electrospray Ionisation Mass Spectrometry

Monolithic capillary columns are prepared by copolymerization of styrene and divinylbenzene, encapsulated capillary columns by immobilizing silica particles with different pore sizes inside a 200 μm i.d. fused silica capillary by encapsulation of the derivatized silica sorbent in a poly(styrene/divinylbenzene) (PS/DVB) matrix. Both allow the rapid and highly efficient separation of single‐ and double‐stranded DNA by ion‐pair reversed‐phase high‐performance liquid chromatography (IP‐RP‐HPLC). The high resolving power of monolithic and encapsulated capillary columns can be utilized for mutation screening in polymerase chain reaction (PCR) amplified polymorphic loci by denaturing HPLC (DHPLC). Recognition of mutations is based on the separation of homo‐ and heteroduplex species by IP‐RP‐HPLC under denaturing conditions, resulting in characteristic peak patterns both for homozygous and heterozygous samples. Separations can be readily hyphenated to electrospray ionization‐mass spectrometry.     

Bacterial Motion in Porous Media

The motion of chemotactically different Escherichia coli C600, cheB287, and AW405 cells was studied using a column packed with silica gel. The model chemotaxis of bacteria in porous media seems to be adequate for natural bacterial chemotaxis in soils. The porous structure of silica gel prevents interfering convective flows. Silica gel columns make it possible to separate bacterial cells differing in motility and chemotaxis. Relevant physical phenomena are discussed. The concept of fast and slow chemotaxis is considered.     

Aminopropyl silica gel as a solid support for preparation of glycolipid immunoadsorbent and purification of antibodies.

Aminopropyl silica gel was prepared from porous silica gel and was used as a solid support for immunoadsorbent in the purification of anti-glycolipid antibodies. For neutral glycosphingolipids, a carboxyl function was generated by oxidation of the olefinic double bond of the sphingosine moiety, whereas for gangliosides the carboxyl group of sialic acid was used to couple with aminopropyl silica gel in the presence of a carbodiimide. These compounds were used for purifying anti-glycolipid antibodies from serum of immunized rabbits. The antibodies bound to the su-strate were released by 2 M potassium thiocyanate and their immunological properties were studied. Aminopropyl silica gel may be preferred over conventional organic solid supports for the following reasons: 1) faster flow rate; 2) higher capacity; 3) easier handling; 4) more economical; and 5) lower susceptibility to microbial attack.     

Bacterial motion in porous media

The motion of chemotactically different Escherichia coli C600, cheB287, and AW405 cells was studied using a column packed with silica gel. The model chemotaxis of bacteria in porous media seems to be adequate to natural bacterial chemotaxis in soils. The porous structure of silica gel prevents interfering convective flows. Silica gel columns make it possible to separate bacterial cells differing in motility and chemotaxis. Relevant physical phenomena are discussed. The concept of fast and slow chemotaxis is considered.     

A large-scale purification of paclitaxel from cell cultures of Taxus chinensis

A large-scale purification method was developed for producing paclitaxel, to guarantee high purity and yield from plant cell cultures. The complete method for mass production was a simple and efficient procedure, for the isolation and purification of paclitaxel from the biomass of Taxus chinensis, consisting of solvent extraction, synthetic adsorbent treatment, and two steps of precipitation, followed by two steps of high performance liquid chromatography (HPLC). The organic solvent extraction of biomass obtained crude extract containing paclitaxel. The use of synthetic adsorbent treatment and precipitation in the prepurification process allows for rapid and efficient separation of paclitaxel from interfering compounds and dramatically increases the yield and purity of crude paclitaxel for HPLC purification steps compared to alternative processes. This prepurification process serves to minimise solvent usage, size, and complexity of the HPLC operations for paclitaxel purification. The paclitaxel of over 99.5% purity can be simply obtained with high yield from crude paclitaxel by HPLC using reverse-phase separation on C18 as the first step and normal-phase separation on silica as the second step.     

快速鉴定格尔德霉素产生菌——吸水链霉菌17997中的洋橄榄叶素

对格尔德霉素产生菌吸水链霉菌17997的发酵液乙酸乙酯提取物进行了硅胶板TLC 初步分离和NaOH溶液喷涂显色,对显红色、具有抗革兰阳性菌活性的条带进行了HPLC分析,提示抗革兰阳性菌活性化合物可能为大环二内酯类抗生素洋橄榄叶素;以dTDP-葡萄糖-4,6-脱水酶 (Tgd) 基因保守区设计PCR引物,扩增了吸水链霉菌17997基因组DNA中的tgd并进行了序列分析,表明吸水链霉菌17997含有洋橄榄叶素生物合成基因簇中的tgd基因;对NaOH溶液喷涂显红色的化合物进行LC-(+)-ESI-MS分析,证实     

New matrices for the purification of pectinases by affinity chromatography

Polygalacturonic acid was used as a ligand in the affinity technique for pectinases purification from the filtrate of Aspergillus niger 71 culture. For this purpose four matrices were examined, namely, alkylamine controlled porous glass (CPG), alkylamine silica gel as well as keratin or polyamide coated silica gel. Good results of pectinase purification was obtained on silanized CPG or keratin coated silica gel supports.     

Use of hexadecyl Fractosil as a hydrophobic carrier for adsorptive immobilization of proteins

Fractosil, a porous form of silica, has been used for the preparation of a hydrophobically derivatized carrier for protein immobilization. Interaction of a number of arbitrarily chosen proteins with hexadecyl-substituted Fractosil has been investigated. Binding of proteins was found to take place with retention of their native properties. Glutamate dehydrogenase, used as a model allosteric protein, was found to retain its catalytic and allosteric properties upon binding to the adsorbent in the form of suspension or column. Positive cooperative interactions for binding of bovine serum albumin and glutamate dehydrogenase to the matrix were observed. These findings are discussed in terms of hydrophobic interactions occurring between various residues of the protein molecules and the hydrophobic ligands in addition to those interactions which may occur with the unsubstituted gel. Results presented on immobilized glutamate dehydrogenase, trypsin, alpha-chymotrypsin, alpha-amylase, and amyloglucosidase clearly indicate possible potential of the support for continuous catalytic transformations.     

Octadecylated silica monolith capillary column with integrated nanoelectrospray ionization emitter for highly efficient proteome analysis

An improved strategy for the preparation of octadecylated silica monolith capillary column with high homogeneity was proposed. Column performance was evaluated by nanoscale HPLC. The design for constructing an integrated nanoelectrospray emitter on the octadecylated silica monolith capillary column was first introduced. In comparison with the separated configuration where the emitter is connected to monolithic capillary column by the aid of a zero dead volume union, the integrated capillary column has the inherent advantage of the minimized extracolumn volume thus providing improved separation quality. The performance of the integrated monolithic capillary column was evaluated by separation of BSA tryptic digest, and peak capacity of 313 with a 30-cm column was obtained. The high separation performance allowed highly confident identification of 662 distinct proteins through assignment of 1933 unique peptides by analysis of tryptic digest of 0.5 mug of Saccharomyces cerevisiae proteins. The higher separation efficiency by a 60-cm monolithic capillary column increased the proteome coverage with identification of 1323 proteins through assignment of 5501 unique peptides over 400-min gradient elution.     

An improved enzymatic cycle for nicotinamide-adenine dinucleotide phosphate.

We describe the use of column chromatography on the nonpolar adsorbent. Amberlite XAD-2, and on silanized silica gel in the desalting and partial purification of cobalamins. These techniques are both simpler and more versatile than phenol extraction, without sacrificing efficiency. In addition, a solvent system for thin-layer chromatography on silanized silica gel is described which rapidly separates naturally occurring cobalamins.     

Cytochalasin B: preparation, analysis in tissue extracts, and pharmacokinetics after intraperitoneal bolus administration in mice

Cytochalasin B (CB) was prepared by methanol extraction of dehydrated mold (Drechslera dematioidea) matte, reverse-phase C18 silica gel batch adsorption, selective elution with 1:1 (v/v) hexane:tetrahydrofuran (THF), crystallization, preparative TLC, and recrystallization. Unit gravity silica gel normal phase chromatography afforded additional CB. Yield per liter of medium was 300 mg of CB greater than 95% pure by NMR, HPLC (60:40 hexane:THF, Lichrosorb Si60 silica gel, 230 nm), and TLC. CB added exogenously to mouse organs at 1 and 5 micrograms/organ was recovered 70 to 100% by methanol extraction, adsorption to C18 silica gel Sep-Pak cartridges, elution with ethyl acetate, and analysis by TLC and/or HPLC. Limiting sensitivity (micrograms/extract) was 0.5 TLC; 1.0 HPLC. Quantitative extraction was confirmed with 3H-labeled CB. CB ip in mice at 50 mg/kg (LD10) distributed rapidly into liver, renal fat, kidney, intestines, mesentery, pancreas, spleen, and blood cells and was cleared from all but liver within 24 h. CB was below detectable levels in thymus, lymph nodes, heart, brain, bone marrow, and lungs. Cytochalasin A is fixed to tissues and not extractable. This work affords a source of CB in quantities permitting in vivo study, provides methods for extraction and analysis, and reveals the pharmacokinetics of ip bolus CB.