Selection of affinity ligands for protein purification from proteolytic digests

A simple method for the selection of affinity ligands from proteolytic digests by affinity chromatography is proposed. A small proportion of the peptides in the trypsin digest of bovine serum albumin (BSA) or the pepsin digest of cytochrome are retarded on insulin-immobilised or HSA (human serum albumin)-immobilised affinity columns, respectively. The peptides in these selected fractions can be immobilised onto solid phases and used in affinity chromatography procedures for the purification of insulin or HSA. © Rapid Science Ltd. 1998     

Identification of affinity ligands for protein purification from synthetic chemical combinatorial libraries

A method to screen combinatorial libraries for the development of selective ligands for protein affinity chromatographic purification is described. The method is based on the application of parallel combinatorial libraries, and it has several potential advantages. The screening procedure is simple and straightforward, and it does not require the chemical derivatization of the target proteins or even that the target protein be pure. The experiment can also be designed to select binders that are less likely to cause protein denaturation. Feasibility of this approach is demonstrated with a model study of the chromatographic purification of bovine albumin serum (BSA) and Avidin.     

Monoclonal antibody purification by affinity chromatography with ligands derived from the screening of peptide combinatory libraries

The peptide, Ala-Pro-Ala-Arg (APAR), was selected from the screening of a tetrapeptide combinatorial synthetic library as the ligand for affinity purification of an anti-Granulocyte Macrophage-Colony Stimulating Factor (GM-CSF) monoclonal antibody (Mab) developed in mouse ascitis. The affinity chromatographic matrix obtained by attachment of APAR to agarose, having a peptide density of 0.5 mol ml^–1, showed a maximum capacity of 9.1 mg Mab ml^–1 and a dynamic capacity of 3.9 mg Mab ml^–1. A 95% yield of electrophoretically pure anti-GM-CSF was obtained in a single step.     

Study on the scale-up of human IgG3 purification using protein A affinity chromatography

The purification of human IgG3 subclass out of IgG (Immunoglobulin-G) was studied using protein A-Sepharose affinity chromatography. The effect of operational parameters such as flow rate, ionic strength, pH and size of sample was investigated, and the process was scaled-up 10-fold. The use of 0.5 m NaCl in the loading buffer had a dramatic effect in the purity of IgG3 recovered in the flowthrough fraction (values in the order of 97% were consistently obtained). This was attributed to a more effective binding of IgG subclasses 1, 2 and 4 to protein A (well known classical mechanism based in Fc fragment) and in some extent to a decrease in the binding of subclass 3 to protein A by the alternative mechanism based in the Fab fragment. The increase in residence time also increased in a relevant way the purity of IgG3. This is attributed to an increased effectiveness of the mechanisms mentioned above. The recovery yields in the IgG3 rich fraction were in the range 21-32% and are possibly a consequence of binding to protein A by the alternative mechanism and also due to deactivation during processing.     

Affinity cross-flow filtration: purification of IgG with a novel protein a affinity matrix prepared from two-dimensional protein crystals

In this article, we describe the use of 1- to 2-mum sized affinity microparticles for the isolation and purification of IgG from artificial IgG-human serum albumin mixtures and clarified hybridoma cell culture supernatants by affinity cross-flow filtration. Affinity microparticles were prepared from cell wall fragments of Clostridium thermohydrosulfuricum L111-69, in which the peptidoglycan-containing layer was completely covered with a hexagonally ordered S-layer lattice. After crosslinking the S-layer protein with glutaraldehyde, carboxyl groups from acidic amino acids were activated with carbodiimide and used for immobilization of Protein. A. Quantitative determination confirmed that Protein A molecules formed a monomolecular layer on the outermost surface of the S-layer lattice. Affinity microparticles were found to withstand high centrifugal and shear forces and revealed no Protein A leakage or S-layer protein release under cross-flow conditions between pH 2 to 12. The IgG-binding capacity of affinity microparticles was investigated under crossflow conditions and compared with that obtained in batch adsorption processes. (c) 1994 John Wiley & Sons, Inc.     

G蛋白亲和色谱法纯化动物血清、抗体效果比较

比较 Hitrap G蛋白 Sepharose亲和色谱系统对不同动物血清或腹水的纯化效果 ,为抗体纯化提供依据。结果显示 ,G蛋白对不同动物血清 Ig G吸附能力不同 ,体现在单位体积抗体回收量明显不同 ,这一特点与 A蛋白亲和色谱系统相似。该方法简便快速 ,纯化抗体纯度高 ,免疫活性好 ,色谱柱可反复使用多次     

Non-specific depurination activity of saporin-S6, a ribosome-inactivating protein, under acidic conditions

Among five ribosome-inactivating proteins tested only saporin-S6 could efficiently release the adenine from adenosine 20 of the synthetic oligoribonucleotide (SRD RNA) mimic of the sarcin/ricin domain of rat 28S rRNA with a Km of 9 microM and a kcat of approximately 0.4 min(-1) at pH 7.6. The optimal pH for the depurination activity of saporin-S6 is 5.0. However, saporin-S6 lost its site-specificity of depurination on SRD RNA around the optimal pH. The non-specific depurination activity of saporin-S6 was dependent on the enzyme concentration and pH conditions. These results are valuable to understand the diversity and the depurination mechanism of ribosome-inactivating proteins.     

The ARiBo tag: a reliable tool for affinity purification of RNAs under native conditions

Although RNA-based biological processes and therapeutics have gained increasing interest, purification of in vitro transcribed RNA generally relies on gel-based methods that are time-consuming, tedious and denature the RNA. Here, we present a reliable procedure for affinity batch purification of RNA, which exploits the high-affinity interaction between the boxB RNA and the N-peptide from bacteriophage λ. The RNA of interest is synthesized with an ARiBo tag, which consists of an activatable ribozyme (the glmS ribozyme) and the λBoxB RNA. This ARiBo-fusion RNA is initially captured on Glutathione-Sepharose resin via a GST/λN-fusion protein, and the RNA of interest is subsequently eluted by ribozyme self-cleavage using glucosamine-6-phosphate. Several GST/λN-fusion proteins and ARiBo tags were tested to optimize RNA yield and purity. The optimized procedure enables one to quickly obtain (3 h) highly pure RNA (>99%) under native conditions and with yields comparable to standard denaturing gel-based protocols. It is widely applicable to a variety of RNAs, including riboswitches, ribozymes and microRNAs. In addition, it can be easily adapted to a wide range of applications that require RNA purification and/or immobilization, including isolation of RNA-associated complexes from living cells and high-throughput applications.     

A蛋白亲和层析法纯化动物血清抗体的效果比较

用ＨｉｔｒａｐＰｒｏｔｅｉｎ－ＡＳｅｐｈａｒｏｓｅ亲和层析系统,对不同动物血清或抗血清抗体的纯化效率进行了比较,为选择抗体纯化方法提供依据。该方法简便快速,纯化的抗体纯度高,能较好地保持抗体免疫学活性。层析柱反复使用４０多次,纯化抗体效率不变。但Ｐｒｏｔｅｉｎ－Ａ对不同动物血清的ＩｇＧ吸附能力不同：对兔和豚鼠的血清抗体吸附能力强     

A蛋白亲和色谱法纯化动物血清抗体的效果比较

比较Hitrap A蛋白琼脂糖凝胶亲和色谱系统,对不同动物血清或抗血清抗体的纯化效率,提供选择抗体纯化方法的依据。该方法简使快速,纯化的抗体纯度高,能较好地保持抗体免疫学活性。色谱柱反复使用40多次,纯化抗体效率不变。但A蛋白对不同动物血清的IgG吸附能力不同,对兔和豚鼠的血清抗体吸附能力强,而对小鼠、山羊和驴的血清抗体吸附能力较弱。说明虽然该方法纯化的抗体纯度高,但它对动物品种有选择。因此,应根据动物品种,选择适合的纯化方法。     

Sephadex-binding RNA ligands: rapid affinity purification of RNA from complex RNA mixtures

Sephadex-binding RNA ligands (aptamers) were obtained through in vitro selection. They could be classified into two groups based on their consensus sequences and the aptamers from both groups showed strong binding to Sephadex G-100. One of the highest affinity aptamers, D8, was chosen for further characterization. Aptamer D8 bound to dextran B512, the soluble base material of Sephadex, but not to isomaltose, isomaltotriose and isomaltotetraose, suggesting that its optimal binding site might consist of more than four glucose residues linked via alpha-1,6 linkages. The aptamer was very specific to the Sephadex matrix and did not bind appreciably to other supporting matrices, such as Sepharose, Sephacryl, cellulose or pustulan. Using Sephadex G-100, the aptamer could be purified from a complex mixture of cellular RNA, giving an enrichment of at least 60 000-fold, compared with a non-specific control RNA. These RNA aptamers can be used as affinity tags for RNAs or RNA subunits of ribonucleoproteins to allow rapid purification from complex mixtures of RNA using only Sephadex.     

Denaturation and partial renaturation of a tightly tetramerized DsRed protein under mildly acidic conditions

The red fluorescent protein, DsRed, recently cloned from coral Discosoma sp. has one of the longest fluorescence waves and one of the most complex absorbance spectra among the family of fluorescent proteins. In this work we found that with time DsRed fluorescence decreases under mildly acidic conditions (pH 4.0-4.8) in a pH-dependent manner, and this fluorescence inactivation could be partially recovered by subsequent re-alkalization. The DsRed absorbance and circular dichroism spectra under these conditions revealed that the fluorescence changes were caused by denaturation followed by partial renaturation of the protein. Further, analytical ultracentrifugation determined that native DsRed formed a tight tetramer under various native conditions. Quantitative analysis of the data showed that several distinct states of protein exist during the fluorescence inactivation and recovery, and the inactivation of fluorescence can be caused by protonation of a single ionogenic group in each monomer of DsRed tetramer.     

Formation of a diazoquinone-type mutagen from acetaminophen treated with nitrite under acidic conditions

Acetaminophen (paracetamol) showed mutagenicity to Salmonella typhimurium TA100 and TA98 either with or without S9 mix when treated with excess nitrite in acidic solution. The mutagen was isolated and identified as 4-acetylamino-6-diazo-2,4-cyclohexadienone. Mutation tests and product analysis by high-performance liquid chromatography, however, suggested that this type of mutagen was hardly formed in the digestive tract of normal subjects.     

A modified tandem affinity purification tag technique for the purification of protein complexes in mammalian cells

The tandem affinity purification (TAP) tag technique has been used with success to identify under nondenaturing conditions protein complexes in yeast. The technique can be used in mammalian cells, but we found that the original technique does not yield enough recovery for the identification of proteins when mammalian cells growing in monolayer have to be used. We present here a modified TAP tag technique that allows sufficient recovery of proteins from mouse fibroblasts growing in monolayer cultures. The recovery allows protein identification by mass spectrometry.     

Suitability of immobilized metal affinity chromatography for protein purification from canola

This work demonstrates that proper selection of a metal ion and chelating ligand enables recovery of a his(6)-tagged protein from canola (Brassica napus) extracts by immobilized metal affinity chromatography (IMAC). When using Co(2+) with iminodiacetate (IDA) as the chelating ligand, beta-glucuronidase-his(6) (GUSH6) can be purified from canola protein extract with almost homogeneous purity in a single chromatographic step. The discrimination with which metal ions bound native canola proteins followed the order Cu(2+) < Ni(2+) < Zn(2+) < Co(2+) in regard to elimination of proteins coeluted with the fusion protein. IDA- and nitrilotriacetate (NTA)-immobilized metal ions showed different binding patterns, whose cause is attributed to a more rigid binding orientation of the his(6) in forming a tridentate with Me(2+)-IDA than in forming a bidentate with Me(2+)-NTA. The more flexible binding allows for multisite interactions over the protein.