Labeling of proteins and oligopeptides with luminescent lanthanide(III) chelates.

Synthesis of a building block that allows introduction of photoluminescent europium(III) and samarium(III) chelates to synthetic oligopeptides on solid phase using standard Fmoc chemistry is described. Upon completion of the oligopeptide synthesis, these conjugates were converted to the corresponding lanthanide(III) chelates by treatment with appropriate lanthanide(III) salt. Also synthesis of a new terpyridine-based europium(III) chelate designed for solution phase protein labeling is demonstrated.     

Antibacterial Co(II), Ni(II), Cu(II) and Zn(II) Complexes of Schiff bases Derived from Fluorobenzaldehyde and Triazoles

Antibacterial Schiff bases derived from 1,2,4-triazoles as well as their metal complexes incorporating cobalt(II), nickel(II), copper(II) and zinc(II) have been synthesized and characterized. Physico-chemical studies suggest that an octahedral geometry for the cobalt(II), nickel(II) and zinc(II)and square-planer geometry for the copper(II) complexes. These complexes have been screened for antibacterial activity against three Gram-positive (Staphylococcus aureus, Staphylococcus epidermidis and Bacillus subtilis) and two Gram-negative (Salmonella typhi and Pseudomonas aeruginosa) bacterial strains, and results compared with the activity of the free ligands. The metal complexes were found to be more potent against one or more bacterial strains than the free ligands.     

Strategies for labeling proteins with PARACEST agents

Reactive surface lysine groups on the monoclonal antibody (3G4) and on human serum albumin (HSA) were labeled with two different PARACEST chelates. Between 7.4 and 10.1 chelates were added per 3G4 molecule and between 5.6 and 5.9 chelates per molecule of HSA, depending upon which conjugation chemistry was used. The immunoreactivity of 3G4 as measured by ELISA assays was highly dependent upon the number of attached chelates: 88% immunoreactivity with 7.4 chelates per antibody versus only 17% immunoreactivity with 10.1 chelates per antibody. Upon conjugation to 3G4, the bound water lifetime of Eu-1 increased only marginally, up from 53 ??s for the non-conjugated chelate to 65-77 ??s for conjugated chelates. Conjugation of a chelate Eu-2 to HSA via a single side-chain group also resulted in little or no change in bound water lifetime (73-75 ??s for both the conjugated and non-conjugated forms). These data indicate that exchange of water molecules protons between the inner-sphere site on covalently attached PARACEST agent and bulk water is largely unaffected by the mode of attachment of the agent to the protein and likely its chemical surroundings on the surface of the protein.     

Methacrylamidohistidine in affinity ligands for immobilized metal-ion affinity chromatography of human serum albumin

Different biologands carrying synthetic adsorbents have been reported in the literature for protein separation. We have developed a novel and new approach to obtain high protein adsorption capacity utilizing 2-methacrylamidohistidine (MAH) as a bioligand. MAH was synthesized by reacting methacrylochloride and histidine. Spherical beads with an average size of 150–200 μm were obtained by the radical suspension polymerization of MAH and 2-hydroxyethyl-methacrylate (HEMA) conducted in an aqueous dispersion medium. p(HEMA-co-MAH) beads had a specific surface area of 17.6 m²/g. Synthesized MAH monomer was characterized by NMR. p(HEMA-co-MAH) beads were characterized by swelling test, FTIR and elemental analysis. Then, Cu(II) ions were incorporated onto the beads and Cu(II) loading was found to be 0.96 mmol/g. These affinity beads with a swelling ratio of 65%, and containing 1.6 mmol. MAH/g were used in the adsorption/desorption of human serum albumin (HSA) from both aqueous solutions and human serum. The adsorption of HSA onto p(HEMA-co-MAH) was low (8.8 mg/g). Cu(II) chelation onto the beads significantly increased the HSA adsorption (56.3 mg/g). The maximum HSA adsorption was observed at pH 3.0 Higher HSA adsorption was observed from human plasma (94.6 mg HSA/g). Adsorption of other serum proteins were obtained as 3.7 mg/g for fibrinogen and 8.5 mg/g for γ-globulin. The total protein adsorption was determined as 107.1 mg/g. Desorption of HSA was obtained using 0.1 M Tris/HCl buffer containing 0.5M NaSCN. High desorption ratios (up to 98% of the adsorbed HSA) were observed. It was possible to reuse Cu(II) chelated-p(HEMA-co-MAH) beads without significant decreases in the adsorption capacities.     

Chelation of ThIV, EuIII and NdIII by dianionic N,N'-bis(pyridoxylideneiminato)ethylene, (Pyr2en)2-. On the search of feasible modelings for heavy metals damage inhibition in living beings

The neutral Schiff base N,N'-bis(pyridoxylideneiminato)ethylene {H(2)pyr(2)en} reacts with Th(NO(3))4.4H2O, NdCl3.6H2O and EuCl3.6H2O to give [Th(pyr(2)en)2(H2O)] (1), [Nd(pyr(2)en)(Hpyr(2)en)].12H2O (2) and [Eu(pyr(2)en)(Hpyr(2)en)] (3). In the three not yet reported bimolecular chelate systems the endo hydroxyl groups of the rings undergo deprotonation confirming the remarkable ability of the pyridoxal-containing ligand H(2)pyr(2)en to yield stable heavy metal chelates with unusual coordination polyhedra. Complexes 2 and 3 show a coordination number 8 for Nd and Eu, achieving a distorted quadratic antiprism. In complex 1 the additional water molecule increases the coordination number of Th to 9 producing a capped square antiprism. The synthesis and structural elucidation of the title complexes starting from a probably non-toxic metabolite like H(2)pyr(2)en should represent a useful contribution to the research on models of prevention and therapy of damage caused by radioactive and heavy elements.     

氨基酸微量元素螯合物的研究与应用

氨基酸微量元素螯合物是一种新型营养元素添加剂,因其具有稳定性好、易消化吸收、生物效价高、抗干扰性强等优势而备受微量元素营养研究的关注,并在动物饲料添加剂行业中得到广泛应用。就氨基酸微量元素螯合物的定义及分类、结构及营养特性、合成方法进展和在各个领域的应用进行综述,并对其前景予以讨论。     

Conformational fluctuation in palladium(II)-methyl aldopentopyranoside complexes

Four methyl d-pentopyranosides (β-Ara, α-Lyx, β-Rib, β-Xyl), as well as Me-β-l-Ara, some of them residing in a well-defined conformation in the solution state (Ara, Xyl) and some showing pronounced chair inversion in solution (Lyx, Rib), form bidentate chelates of the general formula [Pd(chxn)(LH₋₂)-κO,O′] and [Pd(tmen)(LH₋₂)-κO,O′], chxn = (R,R)-cyclohexane-1,2-diamine, tmen = N,N,N′,N′-ethane-1,2-diamine and L = glycoside, with Pd^IIN₂-type metal probes. The dynamic behaviour of the free glycosides is maintained in their chelates, the only case where the metal is bonded by a cis-vicinal diol function. Thus, one fluctuating chelate was detected with the lyxopyranoside in the κO^2,3 binding mode, and two fluctuating chelates were found for the ribopyranoside (κO^2,3 and κO^3,4). No fluctuating chelate was found for the arabinopyranoside (the free arabinopyranoside being non-fluctuating as well), or for the xylopyranoside (no cis-vicinal diol function). In addition, syn-diaxial chelation (κO^2,4) was observed for the ribopyranoside and the xylopyranoside. The spectroscopic results were supplemented by X-ray analyses.     

Avoiding autofluorescence problems: time-resolved fluorescence microscopy with plant and fungal cells in ectomycorrhiza

Sections of Pinus sylvestris-Suillus bovinus ectomycorrhiza were used to test the applicability of time-resolved fluorescence microscopy for studying plant and fungal material. The autofluorescence problems encountered with standard indirect immunofluorescence microscopy when studying specialized plant material were eliminated by the technique. The europium-labeled structures of both plant and fungal cells were the only visible areas in the sections. However, fine details were lost due to the coarse pixel size of the digital camera used to transfer the image on screen. Even with current resolution, time-resolved imaging can be an efficient method for detection of targets in both plant and fungal tissues with autofluorescence problems.     

A laboratory test for screening iron chelates for use in alkaline soils

Summary A soil incubation test is described for screening Fe-chelates for use under alkaline conditions. Ten grams of air-dry soil were mixed with 4 ml of an aqueous solution containing the appropriate amount of iron of the test chelate adding to the soil 24 ppm of iron (soil air-dry weight basis). The moistened soil was incubated in stoppered plastic vials at 24°C. On day 4 from the start of incubation, and at weekly intervals thereafter, the contents of triplicate vials were extracted with 16 ml of DTPA solution prepared according to the method of Lindsay and Norvell. The Fe extracted in this way was considered to be a measure of the stability of the chelates tested in comparison to Sequestrene 138.