ABSTRACT
Recent advancements in viral hydrodynamics afford the calculation of the transport properties of particle suspensions from first principles, namely, from the detailed particle shapes. For coronavirus suspensions, for example, the shape can be approximated by beading (i) the spherical capsid and (ii) the radially protruding peplomers. The general rigid bead-rod theory allows us to assign Stokesian hydrodynamics to each bead. Thus, viral hydrodynamics yields the suspension rotational diffusivity, but not without first arriving at a configuration for the cationic peplomers. Prior work considered identical peplomers charged identically. However, a recent pioneering experiment uncovers remarkable peplomer size and charge heterogeneities. In this work, we use energy minimization to arrange the spikes, charged heterogeneously to obtain the coronavirus spike configuration required for its viral hydrodynamics. For this, we use the measured charge heterogeneity. We consider 20 000 randomly generated possibilities for cationic peplomers with formal charges ranging from 30 to 55. We find the configurations from energy minimization of all of these possibilities to be nearly spherically symmetric, all slightly oblate, and we report the corresponding breadth of the dimensionless rotational diffusivity, the transport property around which coronavirus cell attachment revolves. © 2023 Author(s).
ABSTRACT
The coronavirus is always idealized as a spherical capsid with radially protruding spikes. However, histologically, in the tissues of infected patients, capsids in cross section are elliptical, and only sometimes spherical [Neuman et al., "Supramolecular architecture of severe acute respiratory syndrome coronavirus revealed by electron cryomicroscopy,"J Virol, 80, 7918 (2006)]. This capsid ellipticity implies that coronaviruses are oblate or prolate or both. We call this diversity of shapes, pleomorphism. Recently, the rotational diffusivity of the spherical coronavirus in suspension was calculated, from first principles, using general rigid bead-rod theory [Kanso et al., "Coronavirus rotational diffusivity,"Phys Fluids 32, 113101 (2020)]. We did so by beading the spherical capsid and then also by replacing each of its bulbous spikes with a single bead. In this paper, we use energy minimization for the spreading of the spikes, charged identically, over the oblate or prolate capsids. We use general rigid bead-rod theory to explore the role of such coronavirus cross-sectional ellipticity on its rotational diffusivity, the transport property around which its cell attachment revolves. We learn that coronavirus ellipticity drastically decreases its rotational diffusivity, be it oblate or prolate. © 2022 Author(s).
ABSTRACT
Recently, the rotational diffusivity of the coronavirus particle in suspension was calculated, from first principles, using general rigid bead-rod theory [M. A. Kanso, Phys. Fluids 32, 113101 (2020)]. We did so by beading the capsid and then also by replacing each of its bulbous spikes with a single bead. However, each coronavirus spike is a glycoprotein trimer, and each spike bulb is triangular. In this work, we replace each bulbous coronavirus spike with a bead triplet, where each bead of the triplet is charged identically. This paper, thus, explores the role of bulb triangularity on the rotational diffusivity, an effect not previously considered. We thus use energy minimization for the spreading of triangular bulbs over the spherical capsid. The latter both translates and twists the coronavirus spikes relative to one another, and we then next arrive at the rotational diffusivity of the coronavirus particle in suspension, from first principles. We learn that the triangularity of the coronavirus spike bulb decreases its rotational diffusivity. For a typical peplomer population of 74, bulb triangularity decreases the rotational diffusivity by
ABSTRACT
Recently, the rotational diffusivity of the coronavirus particle in suspension was calculated, from first principles, using general rigid bead-rod theory [M. A. Kanso, Phys. Fluids 32, 113101 (2020)]. We did so by beading the capsid and then also by replacing each of its bulbous spikes with a single bead. However, each coronavirus spike is a glycoprotein trimer, and each spike bulb is triangular. In this work, we replace each bulbous coronavirus spike with a bead triplet, where each bead of the triplet is charged identically. This paper, thus, explores the role of bulb triangularity on the rotational diffusivity, an effect not previously considered. We thus use energy minimization for the spreading of triangular bulbs over the spherical capsid. The latter both translates and twists the coronavirus spikes relative to one another, and we then next arrive at the rotational diffusivity of the coronavirus particle in suspension, from first principles. We learn that the triangularity of the coronavirus spike bulb decreases its rotational diffusivity. For a typical peplomer population of 74, bulb triangularity decreases the rotational diffusivity by 39 % .
ABSTRACT
Introduction: Lockdowns implemented in response to the COVID-19 pandemic are thought to impact mental health [1,2]. Understanding the mechanisms underlying this impact is critical to mitigating it [3]. We tested the hypothesis that one such mechanism involves impaired mood homeostasis (i.e., failure to stabilize mood via mood-modifying activities) [4,5]. Methods: In this ecological momentary assessment cohort study, students in the Netherlands reported their mood and activities 4 times a day between March 16 and 29, 2020. New and immediate lockdown measures were announced on March 23. The average change in mood an individual experienced when engaging in an activity was recorded as its pleasantness. Mood homeostasis was defined as the extent to which participants preferentially engaged in pleasant activities at time t+1 when their mood was low at time t, thus stabilizing their mood. Participants' history of mental illness was screened at baseline. Using linear regressions we assessed (i) changes in mood homeostasis from before to during lockdown, (ii) their moderation by mental illness history, (iii) their association with changes in mood level, and (iv) their mediation by changes in range of activities undertaken. How changes in mood homeostasis might impact the risk of depression was estimated using computer simulations. Statistical significance was set at 2-sided P<.05. Results: Seventy-eight students were included. Mood homeostasis was significantly higher before than during lockdown (0.37 vs 0.28;95% CI of the difference [0.03,0.15];P=.003). For every 0.1 point drop in mood homeostasis, average mood decreased by 1.9 points (95% CI, [1.3,3.6], P<.001). This is enough to bring someone's average mood from the population's mean to its bottom quartile. The change in mood homeostasis from before to during lockdown was mediated by a reduction in the range of activities (proportion mediated: 11.9%, P<.001). Mood homeostasis dropped significantly more among people with (vs without) a history of mental illness (P<.001): from similar values before lockdown (0.31 vs 0.36;P=.37) to significantly different values during lockdown (0.13 vs 0.35;95% CI of the difference [0.11,0.33];P<.001). In computer simulations, changes in mood homeostasis attributed to the lockdown led to a 3-fold increase in the the yearly incidence of depressed mood episodes: from 9.0% (95% CI [6.6%,11.4%]) before lockdown to 28.2% (95% CI [23.6%,32.6%]) during lockdown. Conclusions: Mood homeostasis appears to decrease during lockdown. Larger decreases correlate with larger decreases in mood level. The impact was larger for students with a history of mental illness. The lack of a control group (as the lockdown was implemented nationally) is the main limitation of our study. However, since the same participants were monitored before and during lockdown, the lockdown itself seems to be the most likely explanation for the observed difference. Identifying interventions that increase mood homeostasis might be a promising avenue to mitigate the impact of lockdowns on mental health Table 1. No conflict of interest.