Co-populated Conformational Ensembles of β(2)-Microglobulin Uncovered Quantitatively by Electrospray Ionization Mass Spectrometry

Ordered assembly of monomeric human β(2)-microglobulin (β(2)m) into amyloid fibrils is associated with the disorder hemodialysis-related amyloidosis. Previously, we have shown that under acidic conditions (pH <5.0 at 37 °C), wild-type β(2)m assembles spontaneously into fibrils with different morphologies. Under these conditions, β(2)m populates a number of different conformational states in vitro. However, this equilibrium mixture of conformationally different species is difficult to resolve using ensemble techniques such as nuclear magnetic resonance or circular dichroism. Here we use electrospray ionization mass spectrometry to resolve different species of β(2)m populated between pH 6.0 and 2.0. We show that by linear deconvolution of the charge state distributions, the extent to which each conformational ensemble is populated throughout the pH range can be determined and quantified. Thus, at pH 3.6, conditions under which short fibrils are produced, the conformational ensemble is dominated by a charge state distribution centered on the 9+ ions. By contrast, under more acidic conditions (pH 2.6), where long straight fibrils are formed, the charge state distribution is dominated by the 10+ and 11+ ions. The data are reinforced by investigations on two variants of β(2)m (V9A and F30A) that have reduced stability to pH denaturation and show changes in the pH dependence of the charge state distribution that correlate with the decrease in stability measured by tryptophan fluorescence. The data highlight the potential of electrospray ionization mass spectrometry to resolve and quantify complex mixtures of different conformational species, one or more of which may be important in the formation of amyloid

The Increase of the Lifetime of the Onboard Electronics of Spacecrafts By High-temperature Annealing of Radiation Defects

The technique for increasing the maximum lifetime of the electronic equipment for space applications was developed. The technique is based on controlled temperature annealing of radiation defects accumulated in integrated microcircuits under the impact of ionizing radiations of space environment

Mass spectrometry of B. subtilis CopZ: Cu(I)-binding and interactions with bacillithiol

CopZ from Bacillus subtilis is a well-studied member of the highly conserved family of Atx1-like copper chaperones. It was previously shown via solution and crystallographic studies to undergo Cu(I)-mediated dimerisation, where the CopZ dimer can bind between one and four Cu(I) ions. However, these studies could not provide information about the changing distribution of species at increasing Cu(I) levels. To address this, electrospray ionisation mass spectrometry using soft ionisation was applied to CopZ under native conditions. Data revealed folded, monomeric CopZ in apo- and Cu(I)-bound forms, along with Cu(I)-bound dimeric forms of CopZ at higher Cu(I) loading. Cu4(CopZ)2 was the major dimeric species at loadings >1 Cu(I)/CopZ, indicating the cooperative formation of the tetranuclear Cu(I)-bound species. As the principal low molecular weight thiol in B. subtilis, bacillithiol (BSH) may play a role in copper homeostasis. Mass spectrometry showed that increasing BSH led to a reduction in Cu(I)-bound dimeric forms, and the formation of S-bacillithiolated apo-CopZ and BSH adducts of Cu(I)-bound forms of CopZ, where BSH likely acts as a Cu(I) ligand. These data, along with the high affinity of BSH for Cu(I), determined here to be β2(BSH) = ∼4 × 1017 M−2, are consistent with a role for BSH alongside CopZ in buffering cellular Cu(I) levels. Here, mass spectrometry provides a high resolution overview of CopZ–Cu(I) speciation that cannot be obtained from less discriminating solution-phase methods, thus illustrating the potential for the wider application of this technique to studies of metal–protein interactions

Gold in biogenic apatites of the Baltic-Ladoga phosphorite basin

The distribution of gold in biogenic apatites from the Ordovician deposits in the northwest of the East European Platform shows that the maximum concentration of gold in apatites is found within the Ladoga-Baltic suture zone. Gold mineralization has a superimposed character, which is confirmed by the dependence of the gold content on the size of apatite particles and a number of isotope geochemical systematics in biogenic apatites. Gold is present in the form of high fineness particles to 20 µm in size on the surface of biogenic apatite fragments (phosphate brachiopod shells and conodont elements) and is easily extracted. In 10 % of samples of biogenic apatites, the total content of rare earth elements is more than 1 wt.%

The Technique for I–V Characteristic Measurements of MOSFETs from Output Stage of MOS ICs

Experimental technique for measurements of I–V characteristics of MOSFETs from output stage of MOS ICs is developed and demonstrated using Schmitt trigger array 1594TL2T

ENHANCED LOW DOSE RATE SENSITIVITY (ELDRS) AND REDUCED LOW DOSE RATE SENSITIVITY (RLDRS) IN BIPOLAR DEVICES

Possible physical mechanism of enhanced low dose rate sensitivity (ELDRS) and reduced low dose rate sensitivity (RLDRS)in bipolar devices is described. Modification of the low dose rate conversion model is presented. The enhanced or reduced sensitivity can be connected with a specific position of the effective Fermi level relatively acceptor and donor radiation-induced interface traps. The qualitative and quantitative analysis of the low dose rate effects is presented. The effect of the oxide trapped charge on the value of the oxide electric field and the yield of the oxide charge were taken into account. It leads to dependence of the accumulation of radiation-induced oxide charge and interface traps on the dose rate. In enhancement version the ELDRS and RLDRS conversion model describes the low dose rate effect in as “true” dose rate effect

Schematic Method of Estimation and Increase of Radiation Hardness of the Onboard Radio-electronic Equipment for Space Applications

Experimental and theoretical justification of a schematic method of estimation and increase of radiation hardness of the onboard radio-electronic equipment for space applications on the example of the standard circuit of the voltage follower combining the most widespread schematic decisions: differential stage, current mirror and emitter follower

Methods and Results of Radiation Tests of a Digital-to-Analog Converter LTC1257

The methods and results of radiation tests of a digital-to-analog converter (DAC) LTC1257 is observed in this article

The Methodology and Results of Radiation Tests of ADS 8320 Analog-to-Digital Converter

This article describes a technique ADC ADS8320 radiation tests, as well as circuitry measuring the transfer characteristic of the ADC and the results of tests conducted. It has been found that said ADCs did not show any parametric or functional failure when the absorbed doses to 50 krad (Si) at an intensity of irradiation of 8.5 F/sec passive electric mode

The Application of Schematic Compensation Technique for Increasing of Radioelectronic Devices Reliability

The schematic method development of radiation degradation compensation of operating amplifiers’ input currents and offset voltages on basis of radiation-sensitive parameter degradation research of integral microcircuits and discrete transistors is presented and experimentally verified