Time- and pH-dependent copper binding to Aβ(1-16) peptide: An electrospray ionization-mass spectrometric approach

An elevated concentration of copper ions in the brain of Alzheimer’s disease patients has been reported in many studies and might be associated with an increased aggregation of b-amyloid (Ab) peptides. In the present work, the interaction with copper ions of a model b-amyloid peptide, Ab(1–16), was investigated by electrospray ionization-mass spectrometry (ESI–MS) at two pH values, 7.4 and 6.6, as well as at various peptide: copper ion ratios in the first minutes after components mixing and time intervals. Our results indicated that copper ions specifically bound to Ab(1–16) peptide in solution and that the complex formation increased with time. Once formed in solution, Cu2?-Ab(1–16) complexes could easily be detected in the gas phase by ESI–MS. The pH shift from 7.4 to 6.6 only slightly influenced the Cu2? binding to Ab(1–16). No oligomerization of Ab(1–16) peptide was noticed in the first minutes of copper-peptide interaction

Turbidimetric determination of raw fat in crop seeds

A variant of a turbidimetric method of raw fat determination from seed, which proved to be simple, fast, and accurate, was described in this paper. The method was based on the extraction of lipids from 20 mg samples into acetone followed by their treatment with 1.5% solution of sulfosalicylic acid and spectral measurement at 440 nm against a blank of the reagents. Suitable volumes of acetone extracts should be taken for oily seed samples such as flax, sunflower, or soybean. A standard curve was made with raw fat extracted from the species being analysed. For analysing a large number of samples, the standardization of the turbidimetric method with a few representative Soxhlet values was recommended. Possible interferences, as well as the real results obtained within large scale analyses ,are also shown

Effect of Heavy Metals on the Germination of Wheat Seeds: Enzymatic Assay

Stress caused by heavy metals is a major problem which affects agricultural productivity and, implicitly, human health. Natural flora presents differences of tolerance to heavy metals. Some plants grow well in a soil enriched with heavy metals, while others cannot develop in such conditions. This study investigates the effect of heavy metals on plant viability at molecular level and draws attention to the danger of the widespread use of toxic compounds

Interaction of beta-amyloid(1-40) peptide with pairs of metal ions : an electrospray ion trap mass spectrometric model study

The stoichiometries and the affinity toward simple and paired metal ions of synthetic amyloid-β(1-40) peptide (Aβ1-40) were investigated by electrospray ion trap mass spectrometry (ESI-MS), circular dichroism (CD), and atomic force microscopy (AFM). The results lead to the working hypothesis that pH-dependent metal binding to Aβ1-40 may induce conformational changes, which affect the affinity toward other metals. A significant copper and zinc binding to Aβ1-40 peptide at pH 5.5 was found, whereas nickel ions commonly bind to each molecule of β-amyloid peptide. Some complexes of Aβ1-40 with more than one nickel ion were identified by ESI-MS. In addition, nickel ions proved to enhance Aβ oligomerization. On increasing pH, up to 12 ions of zinc may bind to a single Aβ molecule. Under the same pH and concentration conditions, the binding pattern of the independent copper and silver ions to Aβ1-40 was different from that of the equimolecular mixture of the two metal ions. One might assume that some conformational changes due to water loss altered the capacity of Aβ peptide to bind certain heavy metal ions. As a consequence, copper silver interaction with the binding process to Aβ1-40 became highly complex. A competition between silver and nickel ions for Aβ1-40 binding sites at high pH was also observed. New strategies were proposed to identify the characteristic signals for some important metal ion peptide complexes in the spectra recorded at high pH or high concentrations of metal ions. To explain the formation of such a large number of high metal ion Aβ complexes, we took into consideration the participation of both histidine residues and free amino groups as well as carboxylate ones in the binding process. Finally, CD and AFM studies supported the mass spectrometric data