Core-shell molecularly imprinted polymer nanoparticles with assistant recognition polymer chains for effective recognition and enrichment of natural low-abundance protein.

Core-shell molecular imprinting of nanomaterials overcomes difficulties with template transfer and achieves higher binding capacities for macromolecular imprinting, which are more important to the imprinting of natural low-abundance proteins from cell extracts. In the present study, a novel strategy of preparing core-shell nanostructured molecularly imprinted polymers (MIPs) was developed that combined the core-shell approach with assistant recognition polymer chains (ARPCs). Vinyl-modified silica nanoparticles were used as support and ARPCs were used as additional functional monomers. Immunoglobulin heavy chain binding protein (BiP) from the endoplasmic reticulum (ER) was chosen as the model protein. The cloned template protein BiP was selectively assembled with ARPCs from their library, which contained numerous limited-length polymer chains with randomly distributed recognition and immobilization sites. The resulting complex was copolymerized onto the surface of vinyl-modified silica nanoparticles under low concentrations of the monomers. After template removal, core-shell-structured nanoparticles with a thin imprinted polymer layer were produced. The particles demonstrated considerably high adsorption capacity, fast adsorption kinetics and selective binding affinities toward the template BiP. Furthermore, the synthesized MIP nanoparticles successfully isolated cloned protein BiP from protein mixtures and highly enriched BiP from an ER extract containing thousands of kinds of proteins. The enrichment reached 115-fold and the binding capacity was 5.4 µg g(-1), which were higher than those achieved by using traditional MIP microspheres. The advantageous properties of MIP nanoparticles hold promise for further practical applications in biology, such as protein analysis and purification.

Imprinted polymers with cyclodextrin pseudo-polyrotaxanes as pseudo-supports for protein recognition.

We report a novel approach for preparing protein molecularly imprinted polymers (MIPs) with cyclodextrin pseudo-polyrotaxanes (CD-PPRs) as pseudo-supports, which are formed by self-assembling assistant recognition polymer chains with γ-cyclodextrins. The conformation of the CD-PPRs was characterised by 2D-NOESY, TGA and WAXD. To prepare MIPs, template bovine serum albumin (BSA) was first selectively assembled with modified CD-PPRs to form complexes in the presence of Cu ions. These assemblies were then immobilised by the polymerisation of acrylamide as the monomer and N,N'-methylenebisacrylamide as the cross-linker to prepare protein MIPs. The amount of BSA template adsorbed initially increased with the increase in the amount of CD-PPR and then decreased with the further increase in the CD-PPR content. To obtain the specific adsorption protein, MIPs were washed with KCl solutions of different concentrations. The results of sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed that the specific adsorption proteins could be collected with a 0.500 mol L(-1) KCl solution. The recognition specificity to the template relies on the spatial configuration constructed by CD-PPR and metal ions. Finally, this imprinted polymer was used to purify the template from the protein mixtures containing either two (BSA and ovalbumin) or four (BSA, ovalbumin, soybean trypsine inhibitor and lysozyme) different proteins. Both experiments have demonstrated MIPs high selectivity.

The design of protein-imprinted polymers as antibody substitutes for investigating protein-protein interactions.

Co-immunoprecipitation is a very effective method for studying protein-protein interactions. However, the preparation of antibodies in this method involves the injection of antigen into mammals, and requires the use of the expensive protein A-Sepharose 4B. Molecular imprinting polymer can compensate for these deficiencies. In this paper, a new strategy for studying protein interactions is reported; this method is based on the use of protein-imprinted polymers (PIPs). PIP is a proper substitute for antibody. We designed and synthesized assistant recognition polymer chains (ARPCs), which were limited length polymer chains with randomly distributed recognition and immobilizing sites. The template protein was selectively assembled with ARPCs. The assemblies were adsorbed by macroporous microspheres, and were immobilized by cross-linking polymerization. After removing the templates, the two kinds of synthesized PIPs were used to adsorb natural BiP or FKBP23 from ER extract; both showed high selectivity. Furthermore, we investigated the binding specificity of BiP to FKBP23, using synthesized PIPs. The results showed that FKBP23 could bind to BiP in ER in a process regulated by the concentration of Ca(2+), which was consistent with the immunoprecipitation results. This strategy may provide a general solution for investigating protein interactions.

Bis[µ-1,1'-methyl-enebis(1H-imidazole)-κN:N]bis-[dichloridocobalt(II)].

The title compound, [Co(2)Cl(4)(C(7)H(8)N(4))(2)], contains a dinuclear complex molecule in which each Co(II) atom is tetra-hedrally coordinated by two N atoms and two chloride ions. The 1,1'-methyl-enebis(1H-imidazole) ligands adopt a bis-monodentate bridging mode linking two Co(II) atoms.

Poly[[(µ(3)-2,4,6-tri-4-pyridyl-1,3,5-triazine)copper(I)] nitrate monohydrate].

In the title compound, {[Cu(C(18)H(12)N(6))]NO(3)·H(2)O}(n), the Cu(I) ion is coordinated by three N atoms [Cu-N 1.962 (3)-2.019 (3) Å] from three 2,4,6-tri-4-pyridyl-1,3,5-triazine (L) ligands. Each L ligand bridges three Cu(I) atoms, generating a positively charged three-dimensional polymeric network with voids propagated along the b axis. These voids are filled with NO(3) (-) anions with a shortest Cu⋯O distance of 2.645 (3) Šand water mol-ecules, which are linked into negatively charged helical chains via inter-molecular O-H⋯O hydrogen bonds.

Tetra-kis(2,2'-bipyrid-ine)di-µ(3)-hydroxido-bis(µ-2-oxidobenzoato)tetra-copper(II) dinitrate tetra-hydrate.

The tetra-nuclear title complex, [Cu(4)(C(7)H(4)O(3))(2)(OH)(2)(C(10)H(8)N(2))(4)](NO(3))(2)·4H(2)O, has a crystallographically imposed centre of symmetry. The Cu(II) atoms display a distorted square-pyramidal coordination geometry and are linked by two µ(2)-phenolate O atoms from the salicylate ligands and two µ(3)-hydroxo groups, forming a Cu(4)O(4) core that adopts a 'stepped-cubane' geometry. In the crystal, the cations are linked by O-H⋯O hydrogen bonds to the nitrate anions, which are in turn connected via O-H⋯O inter-actions to centrosymmentric water tetra-mers.

catena-Poly[[diaqua-bis-(formato-κO)nickel(II)]-µ-2,4,6-tris-(4-pyrid-yl)-1,3,5-triazine-κN:N].

In the title compound, [Ni(CHO(2))(2)(C(18)H(12)N(6))(H(2)O)(2)](n), the Ni(II) ion, lying on a crystallographic inversion center, has a distorted octa-hedral coordination comprising two water ligands, two O-atom donors from formate ligands and two N-atom donors from the 2,4,6-tris-(4-pyrid-yl)-1,3,5-triazine ligands. These ligands bridge the Ni(II) complex units, forming zigzag chains along the c axis. Adjacent chains are linked by O-H⋯O hydrogen bonds, forming a three-dimensional supra-molecular network.

Mouse FKBP23 mediates conformer-specific functions of BiP by catalyzing Pro117 cis/trans isomerization.

FK506-binding proteins (FKBPs) are cellular receptors for the immunosuppressant FK506 and rapamycin. They belong to the ubiquitous peptidyl-prolyl cis/trans isomerases (PPIases) family, which can catalyze the cis/trans isomerization of peptidyl-prolyl bond in peptides and proteins. In previous work, we revealed that mouse FKBP23 binds immunoglobulin binding protein (BiP), the major heat shock protein (Hsp) 70 chaperone in the ER, and the binding is interrelated with [Ca(2+)]. Furthermore, the binding can suppress the ATPase activity of BiP through the PPIase activity of FKBP23. In this work, FKBP23 is demonstrated to mediate functions of BiP by catalyzing the Pro(117)cis/trans conformational interconversion in the ATPase domain of BiP. This result may provide new understanding to the novel role of PPIase as a molecular switch.

Preparation of molecular imprinted polymer with quaternary ammonium groups as recognition sites for separation of pig cyclophilin 18 and bovine serum albumin.

We introduce a new type of molecular imprinted polymer (MIP) with immobilized assistant recognition polymer chains (ARPCs) to create effective recognition sites. In this work, cloned pig cyclophilin 18 (pCyP18) and BSA were used as templates, respectively. The template protein was selectively assembled with ARPCs from the library which consists of numerous limited length polymer chains with randomly distributed recognition sites of the quaternary ammonium cationic groups and immobilizing sites. The assemblies of protein and ARPCs were adsorbed by macroporous microspheres and immobilized by cross-linking polymerization. After removing the templates, the two kinds of synthesized MIPs were used to adsorb cloned pCyP18 and BSA from protein mixtures respectively and both showed high selectivity. It confirms that this new method is suitable to separate proteins of both low and high molecular weight. The extended experiment on adsorption of natural pCyP18 from cytosol shows that the obtained MIP using cloned protein as template can be used to enrich natural protein of low content.

[Construction of the dioxin bioassay method based on the clonal expressed aryl hydrocarbon receptor system].

OBJECTIVE: To study the specific binding of the artificial clonal aryl hydrocarbon receptor translocator (ARNT) with the natural aryl hydrocarbon receptor (AhR) and the recolonization by polyclonal antibody. The dose-response relationship with tetrachlo-rodibenzo-dioxin (TCDD) was also studied to develop TCDD detection method and the binding degree related to dose response. METHODS: (1) The target genes including AhR-PAS, AhR-C and ARNT-PAS were amplified by RT-PCR by using the total RNA purified from the liver cells of C57BL/6J mice as templates to construct pGEX-5X1 recombinants. The recombinant plasmids were expressed in E. coli. (2) The rabbits were immuned by the clonal fusion proteins: AhR-PAS, AhR-C to prepare the polyclonal antibody. (3) The natural AhR from the hepatic cytosol of C57BL/6J mice was extracted. The artificial cloning expressed fusion protein:GST-ARNT-PAS and the natural AhR were incubated in different dose of TCDD. The quantity of the heterodimer through affinity adsorption and Western blots were measured. RESULTS: (1) The target proteins including AhR-PAS, AhR-C and ARNT-PAS were successfully cloned and expressed in E. coli. (2) The detection limit of polyclonal antibody AhR-PAS and AhR-C were 5 ng and 1 ng, respectively. (3) The total protein concentration prepared from the liver cells was 60.5 mg/ml. The artificial clonal protein ARNT-PAS could specifically bind to the natural AhR complex with the existence of TCDD. The detection limit of TCDD was 0.25 pmol which was 80 pg approximately. CONCLUSION: A TCDD detection method based on the aryl hydrocarbon receptor system was established and the detection limit might reach pg grade.

De-novo cloning of FKBP23 cDNA from pig ER using nested PCR.

FK506 binding proteins (FKBPs) in cells are known as immunophilins. We have identified and characterized a cDNA encoding an endoplasmic reticulum (ER) immunophilin, FKBP23, from pig liver by nested PCR. The predicted amino acid sequence of pig FKBP23 shows high identity to those of human FKBP23 and mouse FKBP23. It possesses a conserved FKBP-type peptidylprolyl cis-trans isomerase (PPIase) domain and EF-hand domain. We constructed a plasmid to express pFKBP23. Furthermore, we proved that the recombinant pFKBP23 can specifically bind to natural BiP, the main protein of the molecular chaperone Hsp70 in ER lumen; the binding is interrelated with the Ca2+ concentration just as the FKBP23 from mice.

A peptide fragment derived from the T-cell antigen receptor protein alpha-chain adopts beta-sheet structure and shows potent antimicrobial activity.

A 9-residue peptide, CP-1 (GLRILLLKV-NH(2)), is synthesized by solid-phase synthesis method. CP-1 is a C-terminal amidated derivative of a hydrophobic transmembrane segment (CP) of the T-cell antigen receptor (TCR) alpha-chain. CP-1 shows broad-spectrum antimicrobial activities against Gram-positive and Gram-negative bacteria with the minimal inhibitory concentration (MIC) values between 3 and 77microM. Circular dichroism (CD) spectral data shows that CP-1 adopts a well-defined beta-sheet structure in membrane-mimicking environments. CP-1 kills E. coli without lysing the cell membrane or forming transmembrane pores. However, CP-1 can penetrate the bacterial cell membranes and accumulate in the cytoplasm in both Gram-positive S. aureus and Gram-negative E. coli. Moreover CP-1 shows binding affinity for plasmid DNA. These results indicate that the killing mechanism of CP-1 likely involves the penetration into the cytoplasm and binding to intracellular components such as DNA.

Separation/enrichment of active natural low content protein using protein imprinted polymer.

We describe a new type of protein-imprinted polymer for separation/enrichment of active natural protein present at a relatively low level in cell extracts, with a cloned bacterial protein as template. In this work, cloned pig cyclophilin 18 (pCyP18) was used as template. The template protein was selectively assembled with assistant recognition polymer chains (ARPCs) from their library, which consists of numerous limited length polymer chains with randomly distributed recognition and immobilizing sites. These assemblies of protein and ARPCs were adsorbed by porous polymeric beads and immobilized by cross-linking polymerization. After removing the template, the synthesized imprinted polymer was used to adsorb authentic pCyP18 from cell extract, and its proportional content was enriched 200 times. The assay of peptidyl-prolyl cis-trans-isomerase (PPIase) activity showed that natural pCyP18 is more active than cloned pCyP18 and, in particular, it is much more sensitive to the suppressant cyclosporine A (CsA).

Two-step purification of low-content cellular protein using protein-imprinted polymers.

We introduce a new method, based on molecular imprinting, for purification of low-content cellular protein. This is a combination method that uses two types of protein-imprinting polymers (PIPs) synthesized with limited-length polymer chains that contain randomly distributed recognition sites, namely assistant recognition polymer chains, and uses cloned bacterial protein as a template. The low-content cellular target protein was purified from cell extract by this method. This is believed to be the first time that low-content cellular protein has been purified by using PIPs and with only two steps.

LEF-1 negatively controls interleukin-4 expression through a proximal promoter regulatory element.

Lymphoid enhancer-binding factor 1 (LEF-1) and T cell factor (TCF-1) are downstream effectors of the Wnt signaling pathway and are involved in the regulation of T cell development in the thymus. LEF-1 and TCF-1 are also expressed in mature peripheral primary T cells, but their expression is down-regulated following T cell activation. Although the decisive roles of LEF-1 and TCF-1 in the early stages of T cell development are well documented, the functions of these factors in mature peripheral T cells are largely unknown. Recently, LEF-1 was shown to suppress Th2 cytokines interleukin-4 (IL-4), -5, and -13 expression from the developing Th2 cells that overexpress LEF-1 through retrovirus gene transduction. In this study, we further investigated the expression and functions of LEF-1 and TCF-1 in peripheral CD4+ T cells and revealed that LEF-1 is dominantly expressed in Th1 but not in Th2 cells. We identified a high affinity LEF-1-binding site in the negative regulatory element of the IL-4 promoter. Knockdown LEF-1 expression by LEF-1-specific small interfering RNA resulted in an increase in the IL-4 mRNA expression. This study further confirms a negative regulatory role of LEF-1 in mature peripheral T cells. Furthermore, we found that IL-4 stimulation possesses a negative effect on the expressions of LEF-1 and TCF-1 in primary T cells, suggesting a positive feedback effect of IL-4 on IL4 gene expression.

Human CyP33 binds specifically to mRNA and binding stimulates PPIase activity of hCyP33.

Human nuclear cyclophilin 33 (hCyP33) was the first protein which was found to contain an RNA-binding motif and a PPIase domain. It was not known what cellular and physiological roles are played by the RNA-binding activity as well as the PPIase activity of hCyP33. In this paper, we investigated the binding specificity of hCyP33 to different cellular RNA using ion-exchange chromatography and affinity adsorption. Furthermore, the influence of different cellular RNAs to the PPIase activity of hCyP33 was investigated using a protease-coupled method. The results show that hCyP33 binds specifically to mRNA, namely poly(A)(+)RNA, and that binding stimulates the PPIase activity of hCyP33.

Oxidative DNA cleavage by Schiff base tetraazamacrocyclic oxamido nickel(II) complexes.

Nickel is considered a weak carcinogen. Some researches have shown that bound proteins or synthetic ligands may increase the toxic effect of nickel ions. A systematic study of ligand effects on the interaction between nickel complexes and DNA is necessary. Here, we compared the interactions between DNA and six closely related Schiff base tetraazamacrocyclic oxamido nickel(II) complexes NiL(1-3a,1-3b). The structure of one of the six complexes, NiL(3b) has been characterized by single crystal X-ray analysis. All of the complexes can cleave plasmid DNA under physiological conditions in the presence of H(2)O(2). NiL(3b) shows the highest DNA cleavage activity. It can convert supercoiled DNA to nicked DNA then linear DNA in a sequential manner as the complex concentration or reaction time is increased. The cleavage reaction is a typical pseudo-first-order consecutive reaction with the rate constants of 3.27+/-0.14h(-1) (k(1)) and 0.0966+/-0.0042h(-1) (k(2)), respectively, when a complex concentration of 0.6mM is used. The cleavage mechanism between the complex and plasmid DNA is likely to involve hydroxyl radicals as reactive oxygen species. Circular dichronism (CD), fluorescence spectroscopy and gel electrophoresis indicate that the complexes bind to DNA by partial intercalative and groove binding modes, but these binding interactions are not the dominant factor in determining the DNA cleavage abilities of the complexes.

Real-time PCR detection of telomerase activity using specific molecular beacon probes.

Telomerase is a potentially important biomarker and a prognostic indicator of cancer. Several techniques for assessing telomerase activity, including the telomeric repeat amplification protocol (TRAP) and its modified versions, have been developed. Of these methods, real-time quantitative TRAP (RTQ-TRAP) is considered the most promising. In this work, a novel RTQ-TRAP method is developed in which a telomeric repeats-specific molecular beacon is used. The use of the molecular beacon can improve the specificity of the RTQ-TRAP assay, making the method suitable for studying the overall processivity results and the turnover rate of telomerase. In addition, the real-time, closed-tube protocol used obviates the need for post-amplification procedures, reduces the risk of carryover contamination, and supports high throughput. Its performance in synthetic telomerase products and cell extracts suggests that the developed molecular beacon assay can further enhance the clinical utility of telomerase activity as a biomarker/indicator in cancer diagnosis and prognosis. The method also provides a novel approach to the specific detection of some particular gene sequences to which sequence-specific fluorogenic probes cannot be applied directly. Figure Real-time PCR detection of telomerase activity using specific molecular beacon probes.

Binding of FKBP23 to BiP in ER shown by gel filtration chromatography.

FKBP23 was found in mouse endoplasmic reticulum (ER) in 1998. It consists of an N-terminal peptidyl-prolyl cis/trans isomerase (PPIase) domain and a C-terminal domain with Ca2+ binding sites. Previously, we reported that FKBP23 specifically binds to BiP, the main protein of the molecular chaperone Hsp70 in ER lumen, and the binding is interrelated with the Ca2+ concentration. In this work we have found the existence of the complex FKBP23/BiP by separation of an ER extract using gel filtration chromatography (GFC), and that the existence of this complex is Ca2+-interrelated. This result further verified the Ca2+-interrelated binding of these two proteins in vivo.

The binding of FKBP23 to BiP modulates BiP's ATPase activity with its PPIase activity.

Peptidyl-prolyl cis-trans-isomerases (PPIases) are enzymes that can cis-trans-isomerize a Xaa-Pro peptide bond. Three families of PPIases are known: cyclophilins, FKBPs, and parvulins. The physiological functions of the PPIases are only poorly understood. In previous work, we reported that the mouse FK506-binding protein 23 (mFKBP23), which comprises an N-terminal PPIase domain and a C-terminal domain with Ca(2+)-binding sites, binds to mBiP in the endoplasmic reticulum (ER) and this binding is affected by the Ca(2+) concentration. In this study, we demonstrate the ability of mFKBP23 to modulate the ATPase activity of BiP, and that the bound mFKBP23, but not the free mFKBP23, can suppress the ATPase activity of mBiP through its PPIase activity.