Evaluating Nuclei Concentration in Amyloid Fibrillation Reactions Using Back-Calculation Approach

Background: In spite of our extensive knowledge of the more than 20 proteins associated with different amyloid diseases, we do not know how amyloid toxicity occurs or how to block its action. Recent contradictory reports suggest that the fibrils and/or the oligomer precursors cause toxicity. An estimate of their temporal concentration may broaden understanding of the amyloid aggregation process. Methodology/Principal Findings: Assuming that conversion of folded protein to fibril is initiated by a nucleation event, we back-calculate the distribution of nuclei concentration. The temporal in vitro concentration of nuclei for the model hormone, recombinant human insulin, is estimated to be in the picomolar range. This is a conservative estimate since the back-calculation method is likely to overestimate the nuclei concentration because it does not take into consideration fibril fragmentation, which would lower the amount of nuclei Conclusions: Because of their propensity to form aggregates (non-ordered) and fibrils (ordered), this very low concentration could explain the difficulty in isolating and blocking oligomers or nuclei toxicity and the long onset time for amyloid diseases

nES GEMMA analysis of lectins and their interactions with glycoproteins – separation, detection, and sampling of noncovalent biospecific complexes

In order to better understand biological events, lectin–glycoprotein interactions are of interest. The possibility to gather more information than the mere positive or negative response for interactions brought mass spectrometry into the center of many research fields. The presented work shows the potential of a nano-electrospray gas-phase electrophoretic mobility molecular analyzer (nES GEMMA) to detect weak, noncovalent, biospecific interactions besides still unbound glycoproteins and unreacted lectins without prior liquid phase separation. First results for Sambucus nigra agglutinin, concanavalin A, and wheat germ agglutinin and their retained noncovalent interactions with glycoproteins in the gas phase are presented. Electrophoretic mobility diameters (EMDs) were obtained by nES GEMMA for all interaction partners correlating very well with molecular masses determined by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) of the individual molecules. Moreover, EMDs measured for the lectin–glycoprotein complexes were in good accordance with theoretically calculated mass values. Special focus was laid on complex formation for different lectin concentrations and binding specificities to evaluate the method with respect to results obtained in the liquid phase. The latter was addressed by capillary electrophoresis on-a-chip (CE-on-a-chip). Of exceptional interest was the fact that the formed complexes could be sampled according to their size onto nitrocellulose membranes after gas-phase separation. Subsequent immunological investigation further proved that the collected complex actually retained its native structure throughout nES GEMMA analysis and sampling.Austrian Science Foundation (FWF)1

Electrohydrodynamic phenomena

This work is a review article focused on exploring the interactions between external and induced electric fields and fluid motion, in the presence of embedded charges. Such interactions are generally termed electrohydrodynamics (EHD), which encompasses a vast range of flows stemming from multiscale physical effects. In this review article we shall mainly emphasize on two mechanisms of particular interest to fluid dynamists and engineers, namely electrokinetic flows and the leaky dielectric model. We shed light on the underlying physics behind the above mentioned phenomena and subsequently demonstrate the presence of a common underpinning pattern which governs any general electrohydrodynamic motion. Hence we go on to show that the seemingly unrelated fields of electrokinetics and the leaky dielectric models are indeed closely related to each other through the much celebrated Maxwell stresses, which have long been known as stresses caused in fluids in presence of electric and magnetic fields. Interactions between Maxwell Stresses and charges (for instance, in the form of ions) present in the fluid generates a body force on the same and eventually leads to flow actuation. We show that the manifestation of the Maxwell stresses itself depends on the charge densities, which in turn is dictated by the underlying motion of the fluid. We demonstrate how such inter-related dynamics may give rise intricately coupled and non-linear system of equations governing the dynamical state of the system. This article is mainly divided into two parts. First, we explore the realms of electrokinetics, wherein the formation and the structure of the so-called electrical double layer (EDL) is delineated. Subsequently, we review EDL’s relevance to electroosmosis and streaming potential with the key being the presence and absence of an applied pressure gradient. We thereafter focus on the leaky dielectric model, wherein the fundamental governing equations and its main difference with electrokinetics are described. We limit our attentions to the leaky dielectric motion around droplets and flat surfaces and subsequent interface deformation. To this end, through a rigorous review of a number of previous articles, we establish that the interface shapes can be finely tailored to achieve the desired geometrical characteristics by tuning the fluid properties. We further discuss previous studies, which have shown migration of droplets in the presence of strong electric fields. Finally, we describe the effects of external agents such as surface impurities on leaky dielectric motion and attempt to establish a qualitative connection between the leaky dielectric model and EDLs. We finish off with some pointers for further research activities and open questions in this field.by Aditya Bandopadhyay and Uddipta Ghos