Surface Potential Patterns Research Articles

The Biological Properties of the SARS-CoV-2 Cameroon Variant Spike: An Intermediate between the Alpha and Delta Variants.

An analysis of the structural effect of the mutations of the B.1.640.2 (IHU) Spike Receptor Binding Domain (RBD) and N-terminal Domain (NTD) is reported along with a comparison with the sister lineage B.1.640.1. and a selection of variants of concern. The effect of the mutations on the RBD–ACE2 interaction was also assessed. The structural analysis applied computational methods that are able to carry out in silico mutagenesis to calculate energy minimization and the folding energy variation consequent to residue mutations. Tools for electrostatic calculation were applied to quantify and display the protein surface electrostatic potential. Interactions at the RBD–ACE2 interface were scrutinized using computational tools that identify the interactions and predict the contribution of each interface residue to the stability of the complex. The comparison among the RBDs shows that the most evident differences between the variants is in the distribution of the surface electrostatic potential: that of B.1.640.1 is as that of the Alpha RBD, while B.1.640.2 appears to have an intermediate surface potential pattern with characteristics between those of the Alpha and Delta variants. Moreover, the B.1.640.2 Spike includes the mutation E484K that in other variants has been suggested to be involved in immune evasion. These properties may hint at the possibility that B.1.640.2 emerged with a potentially increased infectivity with respect to the sister B.1.640.1 variant, but significantly lower than that of the Delta and Omicron variants. However, the analysis of their NTD domains highlights deletions, destabilizing mutations and charge alterations that can limit the ability of the B.1.640.1 and B.1.640.2 variants to interact with cellular components, such as cell surface receptors.

Establishing a correlation between interfacial microstructures and corrosion initiation sites in Al/Cu joints by SEM–EDS and AFM–SKPFM

A lap joint of AA3003 and pure copper was produced by friction stir welding and the induced interfaces were investigated. Interfacial regions were characterized by SEM–EDS, AFM, SKPFM, OM and Vickers micro-hardness. Multimodal Gaussian distribution (for characterization of surface potential patterns) showed the formation of multiple compounds. A quantitative correlation between microstructure constituents and Volta potential distribution was recognized and confirmed by corrosion attacked sites observations. It was observed that the Al-rich regions proximate the dispersed Cu particles and Cu–Al intermetallics were most susceptible to corrosion attack initiation due to a galvanic driving force between these surface constituents.

A basis for determining body surface potential patterns attributable to single-site coronary arterial occlusion

The authors focus on computational separation of the individual patterns of occlusion of the major segments of the right coronary artery. The raw patterns of occlusion throughout 15 standard subdivisions of the coronary arterial tree and body surface isoarea maps for 8 consecutive 10-msec intervals of QRS were examined in 200 patients with known coronary artery disease. Mean patterns of occlusion and of potential distribution were formed into 15 groups according to which patients showed ≧90% occlusion of the respective segments. By diagonalization of the occlusion matrix, individual potential map patterns were obtained to represent the effect of isolated occlusion of each segment. While these patterns appeared consistent with the known anatomy of ventricular myocardial perfusion, further correlative, study will be needed. The authors suggest that the use of such prototypical patterns of single-site obstruction may be helpful in forming and assessing recognition patterns in the clinical setting of multiple-site, multiple-vessel disease.

Experimental evidence for regional cardiac influence in body surface isopotential maps of dogs.

Isopotential mpas based on 192-200 body surface electrocardiograms were obtained for 20 dogs during multiple patterns of ventricular activation. The purposes of the study were to determine whether the cardiac location of events responsible for surface potentials had a recognizable influence on surface potential patterns and to examine the influence of electrical events occurring simultaneously in multiple cardiac regions. Substantially different effects of electrical activity in various cardiac regions on body surface potentials were evidenced by the body surface location of potential maxima and minima and by patterns of isopotential lines during early portions of ventricular excitation initiated at different ventricular sites. Simultaneous stimulation at some sites gave surface potential distributions with multiple extrema. These were demonstrated to be due to effects of the different cardiac regions, because addition of potentials due to stimulation of the individual sites duplicated those associated with simultaneous stimulation of the same sites. It was also shown that body surface locations of maxima and minima are not related in the same manner to the cardiac location of the responsible events when these events are present in single and multiple regions. Slopes of potentials due to events in single cardiac regions were shown to combine with slopes produced by events in other regions to yield maxima or minima at new body surface locations. Results of the study support the possibility of regional cardiac examination by electrocardiography but suggest that this will require quantitative descriptions of the details of potential patterns in addition to the location of potential peaks.

Comparative surface potential patterns in obstructive and nonobstructive cardiomyopathy

Extensive noninvasive electrophysiologic studies have been performed on patients with cardiomyopathy. Body surface potential maps in the nonobstructive patients mimicked the normal in the general progression of the surface manifestations of activation, but demonstrated relatively more prominent patterns of electrical breakthrough in terms of absolute magnitude and in terms of the perimeter of negativity at a given instant in time. The pattern of the obstructive group was distinctly different, being marked by increased magnitude and duration of positivity with an obvious delay in septal, right ventricular, and left ventricular breakthrough contiguous to the septum, with attenuated negativity at the time of those break-throughs. Maximum negativity also usually occurred 15 to 20 msec. later in the patients with IHSS. The patients with nonobstructive disease characteristically had posteriorly and equatorially oriented VCG loops and often lacked evidence of normal early left-to-right activation of the interventricular septum. Loops of the patients with obstructive disease were usually oriented below the horizontal and were less posteriorly oriented. Additional abnormalities noted in some patients with obstructive disease included slowing of the loop through at least 24 msec. The most extreme form of abnormal sequence of ventricular activation was seen in one third of the patients with IHSS in the form of false infarction patterns. An electrophysiologic rationale of this latter abnormality has been suggested by van Dam and Durrer and is thought by us to represent the best current explanation.

The surface properties of lung extract

The surface tension, surface potential, and surface flow characteristics of crude lung surfactant (LS) monolayers were studied as functions of surface compression and also as functions of age of extract solution. The surface tension characteristics show almost no change with age whereas the surface potential data have maxima at one to two weeks of age. The surface flow measurements, which show qualitative as well as quantitative changes with age, indicate that LS forms a two-dimensional network. The ability to form this network decreases with the age of the extract, and the variation correlates with the surface potential pattern. The rate of network formation is accelerated by compression and/or flow of the LS film. These results suggest that the nonlipid components of LS are probably involved in the formation of the network and that the LS network may be involved in the mechanism which stabilizes the alveoli.