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Introduction Most coronavirus disease 2019 (COVID-19) pediatric patients are asymptomatic; however, several neurological manifestations associated with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection have been reported. Demyelinating events such as acute disseminated encephalomyelitis have been recently included among potential complications of COVID-19. Case Report We describe the case of a 12-year-old boy who developed central nervous system demyelinating lesions following SARS-CoV-2 infection. Two months prior he had been diagnosed with panuveitis but was otherwise healthy. Three weeks after testing positive for SARS-CoV-2, he started to complain of right temporal headache associated with right orbital pain without vision impairment. Brain magnetic resonance imaging showed large leukodystrophy-like demyelinating lesions. Standard electroencephalogram revealed a slow activity on the right hemisphere. His clinical and electroencephalographic course was favorable, with a good response to corticosteroid therapy and infusions of intravenous immunoglobulins. Delayed but complete resolution of brain lesions was noted on imaging. Conclusion Our case contributes to broaden the knowledge regarding the spectrum of possible complications of SARS-CoV-2 infection. The relative lack of clinical manifestations in our patient can be seen as a warning not to underestimate even mild neurological symptoms correlated with COVID-19.

Nucleic acids (NAs) in modern biology accomplish a variety of tasks, and the emergence of primitive nucleic acids is broadly recognized as a crucial step for the emergence of life. While modern NAs have been optimized by evolution to accomplish various biological functions, such as catalysis or transmission of genetic information, primitive NAs could have emerged and been selected based on more rudimental chemical–physical properties, such as their propensity to self-assemble into supramolecular structures. One such supramolecular structure available to primitive NAs are liquid crystal (LC) phases, which are the outcome of the collective behavior of short DNA or RNA oligomers or monomers that self-assemble into linear aggregates by combinations of pairing and stacking. Formation of NA LCs could have provided many essential advantages for a primitive evolving system, including the selection of potential genetic polymers based on structure, protection by compartmentalization, elongation, and recombination by enhanced abiotic ligation. Here, we review recent studies on NA LC assembly, structure, and functions with potential prebiotic relevance. Finally, we discuss environmental or geological conditions on early Earth that could have promoted (or inhibited) primitive NA LC formation and highlight future investigation axes essential to further understanding of how LCs could have contributed to the emergence of life.

We investigated the electrostatic behavior of ferroelectric liquid droplets exposed to the pyroelectric field of a lithium niobate ferroelectric crystal substrate. The ferroelectric liquid is a nematic liquid crystal in which almost complete polar ordering of the molecular dipoles generates an internal macroscopic polarization locally collinear to the mean molecular long axis. Upon entering the ferroelectric phase by reducing the temperature from the nematic phase, the liquid crystal droplets become electromechanically unstable and disintegrate by the explosive emission of fluid jets. These jets are mostly interfacial, spreading out on the substrate surface, and exhibit fractal branching out into smaller streams to eventually disrupt, forming secondary droplets. We understand this behavior as a manifestation of the Rayleigh instability of electrically charged fluid droplets, expected when the electrostatic repulsion exceeds the surface tension of the fluid. In this case the charges are due to the bulk polarization of the ferroelectric fluid which couples to the pyroelectric polarization of the underlying lithium niobate substrate through its fringing field and solid-fluid interface coupling. Since the ejection of fluid does not neutralize the droplet surfaces, they can undergo multiple explosive events as the temperature decreases., 15 pages, 10 figures

Background Quarantine and isolation measures during COVID-19 pandemic may have caused additional stress and challenged the mental health of the youth. Aim of the study is to investigate the COVID-19 pandemic impact on neuropsychological disorders (NPD) of Italian children and adolescents to provide general pediatric recommendations. Material and methods A retrospective multicenter observational study was planned by the Italian Pediatric Society (SIP) to explore the impact of COVID-19 on the access of children to pediatric Emergency Departments (pED) for the evaluation of neuropsychological symptoms, collecting the classification codes of diagnoses between March 1, 2019 and March 2, 2021. The period study was split into two sub-periods: a pre COVID-19 period (from March 1 2019 to March 1, 2020) and a COVID-19 period (from March 2, 2020 to March 2, 2021). As additional information, data on NPD hospitalizations in any pediatric department of the involved centers were recorded. Results During the study period, a total of 533,318 children were admitted to the pED involved in the study. Despite a 48.2% decline of pED admissions, there was a significant increase (83.1%) in patient admissions for NPD. The most frequent NPD conditions which increased during the COVID-19 pandemic were suicidal ideation (+ 147%), depression (+ 115%), eating disorder (+ 78.4%), and psychosis (+ 17.2%). During the pandemic period, a 39.5% increase in NPD hospitalizations was observed as well. The NPD disorders that mostly required hospitalizations were suicidal ideation (+ 134%), depression (+ 41.4%), eating disorder (+ 31.4%), and drug abuse (+ 26.7%). COVID-19 pandemic had a major impact on children's health, mainly on their NPD development. Neuropsychological assessment should be required at the primary level, in the pediatrician's office, to facilitate early capture of the sign of impairment and provide an adequate treatment. Conclusion SIP underlines the psychological consequences of COVID 19 pandemic on the youngest and recommends an early identification of NPD in the pediatric population to avoid other serious consequences for children's physical and mental health.

Molecular ecology uses molecular genetic data to answer traditional ecological questions in biogeography and biodiversity, among others. Several ecological principles, such as the niche hypothesis and the competitive exclusions, are based on the fact that species compete for resources. More in generally, it is now recognized that species interactions play a crucial role in determining the coexistence and abundance of species. However, experimentally controllable platforms, which allow us to study and measure competitions among species, are rare and difficult to implement. In this work, we suggest exploiting a Molecular Dynamics coarse-grained model to study interactions among single strands of DNA, representing individuals of different species, which compete for binding to other oligomers considered as resources. In particular, the well-established knowledge of DNA–DNA interactions at the nanoscale allows us to test the hypothesis that the maximum consecutive overlap between pairs of oligomers measure the species’ competitive advantages. However, we suggest that a more complex structure also plays a role in the ability of the species to successfully bind to the target resource oligomer. We complement the simulations with experiments on populations of DNA strands which qualitatively confirm our hypotheses. These tools constitute a promising starting point for further developments concerning the study of controlled, DNA-based, artificial ecosystems.

Concentrated solutions of blunt-ended DNA oligomer duplexes self-assemble in living polymers and order into lyotropic nematic liquid crystal phase. Using the optical torque provided by three distinct illumination geometries, we induce independent splay, twist, and bend deformations of the DNA nematic and measure the corresponding elastic coefficients

The effectiveness of several biological and biotechnological processes relies on the remarkably selective pairing of nucleic acids in contexts of molecular complexity. Relevant examples are the on-target binding of primers in genomic PCR and the regulatory efficacy of microRNA via binding on the transcriptome. Here, we propose a statistical framework that enables us to describe and understand such selectivity by means of a model that is extremely cheap from a computational point of view. By re-parametrizing the hybridization thermodynamics on three classes of base pairing errors, we find a convenient way to obtain the free energy of pairwise interactions between nucleic acids. We thus evaluate the hybridization statistics of a given oligonucleotide within a large number of competitive sites that we assume to be random, and we compute the probability of on-target binding. We apply our strategy to PCR amplification and microRNA-based gene regulation, shedding new light on their selectivity. In particular, we show the relevance of the defectless pairing of 3′ terminals imposed by the polymerase in PCR selection. We also evaluate the selectivity afforded by the microRNA seed region, thus quantifying the extra contributions given by mechanisms beyond pairing statistics.

Very young age could be a potential risk factor for community‐acquired severe acute respiratory syndrome coronavirus 2, due to immature immune systems. We retrospectively enrolled 39 infants up to 6 months of age who had presented to our tertiary Italian children's hospital emergency room between 9 March 2020 and 8 March 2021 and tested positive for the virus. Of those, 38 had a non‐specific mild or asymptomatic clinical course and only one patient was admitted to intensive care with severe symptoms. We concluded that very young infants with COVID‐19 had a generally favourable disease course.

The success of nematic liquid crystals in displays and optical applications is due to the combination of their optical uniaxiality, fluidity, elasticity, responsiveness to electric fields and controllable coupling of the molecular orientation at the interface with solid surfaces. The discovery of a polar nematic phase opens new possibilities for liquid crystal-based applications, but also requires a new study of how this phase couples with surfaces. Here we explore the surface alignment of the ferroelectric nematic phase by testing different rubbed and unrubbed substrates that differ in coupling strength and anchoring orientation and find a variety of behaviors – in terms of nematic orientation, topological defects and electric field response – that are specific to the ferroelectric nematic phase and can be understood as a consequence of the polar symmetry breaking. In particular, we show that by using rubbed polymer surfaces it is easy to produce cells with a planar polar preferential alignment and that cell electrostatics (e.g. grounding the electrodes) has a remarkable effect on the overall homogeneity of the ferroelectric ordering.

The terms "epididymal cyst" and "spermatocele" are commonly used to describe the same entity, but, conversely, they are slightly different. Epididymal cyst is a benign mass, and it is more common than previously thought in prepubertal age. Pathogenic mechanisms for epididymal cyst have not been fully clarified yet, even if epididymal cysts have been reported in association with other malformations of the urinary tract or complex syndromes. Epididymal cyst is easily characterized and differentiated from spermatocele using ultrasound imaging. Conservative management constitutes the treatment of choice in the majority of cases, and surgery is recommended only in selected cases. Conclusion: To date, a review on epididymal cyst in childhood is lacking in the literature. Herein, an overview of knowledge about epididymal cyst in children has been carried out with particular attention to differential diagnosis, proper management, and practice guidelines for caregivers of children who may present with an epididymal cyst. What is Known: • Epididymal cyst is a benign sac in the testicles which is usually asymptomatic. • Epididymal cyst is easily diagnosed by ultrasound scans, and it is considered a self-limiting disease in the majority of cases. What is New: • Insight on differential diagnosis between epididymal cyst and spermatocele. • Valuable knowledge on the best management strategy for epididymal cyst and on practice guidelines for parents of children presenting with epididymal cyst.

Genome instability is a condition characterized by the accumulation of genetic alterations and is a hallmark of cancer cells. To uncover new genes and cellular pathways affecting endogenous DNA damage and genome integrity, we exploited a Synthetic Genetic Array (SGA)-based screen in yeast. Among the positive genes, we identified VID22, reported to be involved in DNA double-strand break repair. vid22Δ cells exhibit increased levels of endogenous DNA damage, chronic DNA damage response activation and accumulate DNA aberrations in sequences displaying high probabilities of forming G-quadruplexes (G4-DNA). If not resolved, these DNA secondary structures can block the progression of both DNA and RNA polymerases and correlate with chromosome fragile sites. Vid22 binds to and protects DNA at G4-containing regions both in vitro and in vivo. Loss of VID22 causes an increase in gross chromosomal rearrangement (GCR) events dependent on G-quadruplex forming sequences. Moreover, the absence of Vid22 causes defects in the correct maintenance of G4-DNA rich elements, such as telomeres and mtDNA, and hypersensitivity to the G4-stabilizing ligand TMPyP4. We thus propose that Vid22 is directly involved in genome integrity maintenance as a novel regulator of G4 metabolism., Associazione Italiana per la Ricerca sul Cancro (AIRC) [15631, 21806 to M.M.F.]; MIUR [PRIN 2015-2015SJLMB9; PRIN 2017-2017KSZZJW to M.M.F.]; Telethon [GGP15227 to M.M.F.]; F.L. was supported by the University of Milano: ‘‘Piano di Sviluppo dell’Ateneo per la Ricerca. Linea B: Supporto per i Giovani Ricercatori’’; M.C.B. was supported by Fondazione Veronesi; Research at the laboratory of A.A. was funded by the Spanish Ministry of Economy and Competitiveness [BFU2016-75058-P]; B.G.G. was funded by the Spanish Association Against Cancer; MIUR [PRIN2017-2017Z55KC to T.B.]; M.C., D.S.H. are supported by MIUR [PRIN 2017] and CNRbiomics [PIR01_00017]; H2020 Projects ELIXIR-EXCELERATE, EOSC-Life, EOSC-Pillar and Elixir-IIB; G.W.B. was supported by the Canadian Institutes of Health Research[FDN-159913]. Funding for open access charge: Associazione Italiana per la Ricerca sul Cancro (AIRC) [21806].

Yield stress materials deform as elastic solids or flow as viscous liquids, depending on the applied stress, which also allows them to trap particles below a certain size or density threshold. To investigate the conditions for such a transition at the microscale, we use an optofluidic microrheometer, based on the scattering of an infrared beam onto a microbead, which reaches forces in the nN scale. We perform creep experiments on a model soft material composed of swollen microgels, determining the limits of linear response and yield stress values, and observe quantitative agreement with bulk measurements. However, the motion of the microbead, both below and above yielding, reflects distinctive microscale features of the surrounding material, whose plastic rearrangements were investigated by us using small, passive tracers.

Deoxyribonucleic acid (DNA) hybridization is at the heart of countless biological and biotechnological processes. Its theoretical modeling played a crucial role, since it has enabled extracting the relevant thermodynamic parameters from systematic measurements of DNA melting curves. In this article, we propose a framework based on statistical physics to describe DNA hybridization and melting in an arbitrary mixture of DNA strands. In particular, we are able to analytically derive closed expressions of the system partition functions for any number $N$ of strings and explicitly calculate them in two paradigmatic situations: (i) a system made of self-complementary sequences and (ii) a system comprising two mutually complementary sequences. We derive the melting curve in the thermodynamic limit ($N\ensuremath{\rightarrow}\ensuremath{\infty}$) of our description, which provides a full justification for the extra entropic contribution that in classic hybridization modeling was required to correctly describe within the same framework the melting of sequences either self-complementary or not. We thus provide a thorough study comprising limit cases and alternative approaches showing how our framework can give a comprehensive view of hybridization and melting phenomena.

DNA hybridization is at the heart of countless biological and biotechnological processes. Its theoretical modeling played a crucial role, since it has enabled extracting the relevant thermodynamic parameters from systematic measurements of DNA melting curves. However, in its current state, hybridization modelling requires introducing an extra entropic contribution in self-complementary sequences that lacks any biophysical meaning. In this article, we propose a framework based on statistical physics to describe DNA hybridization and melting in an arbitrary mixture of DNA strands. In particular, we are able to analytically derive closed expressions of the system partition functions for any numberNof strings, and explicitly calculate them in two paradigmatic situations: (i) a system made of self-complementary sequences and (ii) a system comprising two mutually complementary sequences. We derive the melting curve in the thermodynamic limit (N→ ∞) of our description, which differs from the expression commonly used to evaluate the melting of self-complementary systems in that it does not require correcting terms. We provide a thorough study comprising limit cases and alternative approaches showing how our framework can give a comprehensive view of hybridization and melting phenomena.SIGNIFICANCEIn this study, we provide a transparent derivation of the melting curves of DNA duplexes using basic tools of statistical mechanics. We find that in the case of self-complementary sequences, our expression differs from the one used in literature, which is generally amended by the introduction of a phenomenological correction which in our approach becomes unnecessary. By offering a clean formal description of DNA hybridization, our approach sharpens our understanding of DNA interactions and opens the way to study the pairing of DNA oligomers away from any thermodynamic limit.

MicroRNAs are widely studied as circulating biomarkers for early stage diagnosis of several diseases, but their detection and quantification are currently performed through complex and time consuming procedures. Herein, we demonstrate a rapid, multiplex, homogenous detection method based on two-step amplification of the signal measured by a recent label-free optical biosensor, Reflective Phantom Interface (RPI). The specific capture with surface DNA probes is combined to mass amplification by an antibody targeting DNA-RNA hybrids and polyclonal secondary antibody, all performed without washing steps. Through this method, we achieved linear, sub-pM quantification of different miRNAs in less than 2 hours.The RPI enabled the characterization of equilibrium and kinetics of each individual interaction involved in this multi-step process, which allowed to model and optimize the relative concentrations and the time intervals of the assay. In particular, we found that the sensitivity for a miRNA target is affected by its sequence features, like the binding affinity and the degree of self-complementarity, which indirectly regulates probe-probe interactions. The limit of detection is ultimately determined by the kinetic constant for association between the probe and the target. Therefore, the performance of the assay may be further improved by acting on the probe architecture, favouring additional stacking interactions with the miRNA.

We evaluate, by means of synchrotron small-angle X-ray scattering, the shape and mutual interactions of DNA tetravalent nanostars as a function of temperature in both the gas-like state and across the gel transition. To this end, we calculate the form factor from coarse-grained molecular dynamics simulations with a novel method that includes hydration effects; we approximate the radial interaction of DNA nanostars as a hard-sphere potential complemented by a repulsive and an attractive Yukawa term; and we predict the structure factors by exploiting the perturbative random phase approximation of the Percus-Yevick equation. Our approach enables us to fit all the data by selecting the particle radius and the width and amplitude of the attractive potential as free parameters. We determine the evolution of the structure factor across gelation and detect subtle changes of the effective interparticle interactions, that we associate to the temperature and concentration dependence of the particle size. Despite the approximations, the approach here adopted offers new detailed insights into the structure and interparticle interactions of this fascinating system.

MicroRNAs are widely studied as circulating biomarkers for early stage diagnosis of several diseases. Detection and quantification of miRNAs is currently performed through complex and time consuming procedures. Herein we demonstrate a rapid, multiplex, one-pot detection method based on two-step amplification of the signal measured by Reflective Phantom Interface (RPI) label-free optical biosensor. We achieved sub-pM quantification of different miRNAs in about 1.5 h, through specific capture with surface DNA probes combined to a 35-fold mass amplification by an antibody targeting DNA-RNA hybrids and polyclonal secondary antibody, all performed without washing steps. The assay is the result of a modelling and optimization of the multi-step process that has been made possible by the RPI characterization of each individual interaction involved.

We propose and demonstrate an on-chip optofluidic device allowing active oscillatory microrheological measurements with sub-μL sample volume, low cost and high flexibility. Thanks to the use of this optofluidic microrheometer it is possible to measure the viscoelastic properties of complex fluids in the frequency range 0.01–10 Hz at different temperatures. The system is based on the optical forces exerted on a microbead by two counterpropagating infrared laser beams. The core elements of the optical part, integrated waveguides and an optical modulator, are fabricated by fs-laser writing on a glass substrate. The system performance is validated by measuring viscoelastic solutions of aqueous worm-like micelles composed by Cetylpyridinium Chloride (CPyCl) and Sodium Salicylate (NaSal).

Self-synthesizing materials, in which supramolecular structuring enhances the formation of new molecules that participate to the process, represent an intriguing notion to account for the first appearance of biomolecules in an abiotic Earth. We present here a study of the abiotic formation of interchain phosphodiester bonds in solutions of short RNA oligomers in various states of supramolecular arrangement and their reaction kinetics. We found a spectrum of conditions in which RNA oligomers self-assemble and phase separate into highly concentrated ordered fluid liquid crystal (LC) microdomains. We show that such supramolecular state provides a template guiding their ligation into hundred-bases long chains. The quantitative analysis presented here demonstrates that nucleic acid LC boosts the rate of end-to-end ligation and suppresses the formation of the otherwise dominant cyclic oligomers. These results strengthen the concept of supramolecular ordering as an efficient pathway toward the emergence of the RNA World in the primordial Earth.

Liquid crystals (LCs) ordering of DNA and RNA oligomers relies on the presence of inter-duplex end-to-end attraction, driving the formation of linear aggregates. Such interactions are gauged, at a macroscopic level, by the osmotic pressure at the isotropic-nematic and nematic-columnar phase transitions. We studied aqueous solutions of PEG and DNA duplex-forming oligomers, finding that there is a wide range of concentrations in which these mixtures phase separate into coexisting PEG-rich and DNA-rich phases, the latter being either in the isotropic state or ordered as a nematic or columnar LC. We determined the phase diagram in mixtures of PEG and DNA duplexes with different terminal motifs – blunt ends, sticky overhangs, aggregation-preventing overhangs – and measured the partitioning of the species in the coexisting phases. On this basis, we determined the osmotic pressure as a function of the DNA concentration across the phase diagram. We compared the equation of state obtained in this way with ...