Supraventricular Tachycardia (SVT) and Stroke: Should We Pump the Brakes on Cardioversion?

In the list of top 10 causes of death worldwide in 2019, stroke ranks number two, with a recent uptick in incidence involving younger adults. While common risk factors like tobacco use, hypertension, diabetes, and atrial fibrillation have been well studied, recent reports have also linked paroxysmal supraventricular tachycardia (PSVT) with strokes. This case highlights a rare presentation of a 25-year-old female who suffered an ischemic stroke shortly after undergoing chemical cardioversion for sustained SVT. To date, there are only three documented cases reporting an ischemic event following shortly after cardioversion of SVT, all confined to the pediatric population. Currently, there is limited evidence to guide the management of these complex patients. This case presents a valuable discussion regarding the futility or efficacy of imaging prior to cardioversion of SVT as well as furthers the conversation behind the theorized mechanisms linking PSVT and strokes.

Blood pH Analysis in Combination with Molecular Medical Tools in Relation to COVID-19 Symptoms

The global outbreak of SARS-CoV-2/COVID-19 provided the stage to accumulate an enormous biomedical data set and an opportunity as well as a challenge to test new concepts and strategies to combat the pandemic. New research and molecular medical protocols may be deployed in different scientific fields, e.g., glycobiology, nanopharmacology, or nanomedicine. We correlated clinical biomedical data derived from patients in intensive care units with structural biology and biophysical data from NMR and/or CAMM (computer-aided molecular modeling). Consequently, new diagnostic and therapeutic approaches against SARS-CoV-2 were evaluated. Specifically, we tested the suitability of incretin mimetics with one or two pH-sensitive amino acid residues as potential drugs to prevent or cure long-COVID symptoms. Blood pH values in correlation with temperature alterations in patient bodies were of clinical importance. The effects of biophysical parameters such as temperature and pH value variation in relation to physical-chemical membrane properties (e.g., glycosylation state, affinity of certain amino acid sequences to sialic acids as well as other carbohydrate residues and lipid structures) provided helpful hints in identifying a potential Achilles heel against long COVID. In silico CAMM methods and in vitro NMR experiments (including ³¹P NMR measurements) were applied to analyze the structural behavior of incretin mimetics and SARS-CoV fusion peptides interacting with dodecylphosphocholine (DPC) micelles. These supramolecular complexes were analyzed under physiological conditions by ¹H and ³¹P NMR techniques. We were able to observe characteristic interaction states of incretin mimetics, SARS-CoV fusion peptides and DPC membranes. Novel interaction profiles (indicated, e.g., by ³¹P NMR signal splitting) were detected. Furthermore, we evaluated GM1 gangliosides and sialic acid-coated silica nanoparticles in complex with DPC micelles in order to create a simple virus host cell membrane model. This is a first step in exploring the structure-function relationship between the SARS-CoV-2 spike protein and incretin mimetics with conserved pH-sensitive histidine residues in their carbohydrate recognition domains as found in galectins. The applied methods were effective in identifying peptide sequences as well as certain carbohydrate moieties with the potential to protect the blood-brain barrier (BBB). These clinically relevant observations on low blood pH values in fatal COVID-19 cases open routes for new therapeutic approaches, especially against long-COVID symptoms.

Evidence for Quantum Chemical Effects in Receptor-Ligand Binding Between Integrin and Collagen Fragments - A Computational Investigation With an Impact on Tissue Repair, Neurooncolgy and Glycobiology

The collagen-integrin interactions are mediated by the doubly charged Mg2+ cation. In nature this cation seems to have the optimal binding strength to stabilize this complex. It is essential that the binding is not too weak so that the complex becomes unstable, however, it is also of importance that the ligand-receptor binding is still labile enough so that the ligand can separate from the receptor in a suited environment. In the case of crystal growing for experimentally useful integrin-collagen fragment complexes it turned out that Co2+ cations are ideal mediators to form stable complexes for such experiments. Although, one can argue that Co2+ is in this context an artificial cation, however, it is now of special interest to test the impact of this cation in cell-culture experiments focusing on integrin-ligand interactions. In order to examine, in particular, the role cobalt ions we have studied a Co2+ based model system using quantum chemical calculations. Thereby, we have shown that hybrid and long-range corrected functional, which are approximations provide already a sufficient level of accuracy. It is of interest to study a potential impact of cations on the binding of collagen-fragments including collagens from various species because different integrins have numerous biological functions (e.g. Integrin - NCAM (Neural cell adhesion molecule) interactions) and are triggered by intact and degraded collagen fragments. Since integrin-carbohydrate interactions play a key role when bio-medical problems such as tumor cell adhesion and virus-host cell infections have to be addressed on a sub-molecular level it is essential to understand the interactions with heavy-metal ions also at the sub-atomic level. Our findings open new routes, especially, in the fields of tissue repair and neuro-oncology for example for cell-culture experiments with different ions. Since Co2+ ions seem to bind stronger to integrin than Mg2+ ions it should be feasible to exchange these cations in suited tumor tissues although different cations are present in other metalloproteins which are active in such tissues. Various staining methods can be applied to document the interactions of integrins with carbohydrate chains and other target structures. Thereby, it is possible to study a potential impact of these interactions on biological functions. It was therefore necessary to figure out first which histological-glycobiological experimental settings of tumor cells are suited for our purpose. Since the interactions of several metalloproteins (integrin, ADAM12) with polysialic acid and the HNK-1 epitope play a crucial role in tumor tissues selected staining methods are proper tools to obtain essential information about the impact of the metal ions under study.

Nanomedical Relevance of the Intermolecular Interaction Dynamics-Examples from Lysozymes and Insulins

Insulin and lysozyme share the common features of being prone to aggregate and having biomedical importance. Encapsulating lysozyme and insulin in micellar nanoparticles probably would prevent aggregation and facilitate oral drug delivery. Despite the vivid structural knowledge of lysozyme and insulin, the environment-dependent oligomerization (dimer, trimer, and multimer) and associated structural dynamics remain elusive. The knowledge of the intra- and intermolecular interaction profiles has cardinal importance for the design of encapsulation protocols. We have employed various biophysical methods such as NMR spectroscopy, X-ray crystallography, Thioflavin T fluorescence, and atomic force microscopy in conjugation with molecular modeling to improve the understanding of interaction dynamics during homo-oligomerization of lysozyme (human and hen egg) and insulin (porcine, human, and glargine). The results obtained depict the atomistic intra- and intermolecular interaction details of the homo-oligomerization and confirm the propensity to form fibrils. Taken together, the data accumulated and knowledge gained will further facilitate nanoparticle design and production with insulin or lysozyme-related protein encapsulation.

Interaction of different Chlamydiae species with bovine spermatozoa

Background

Interaction of spermatozoa and Chlamydiae spp. might contribute to reduced fertility in cattle. To proof this hypothesis, bovine semen was incubated with viable or heat inactivated Chlamydia (C.) abortus or psittaci (Multiplicity of infection = 1) and sperm motility was monitored with a computer-assisted sperm analyzer over 24 h. Additionally, the interaction with the spermatozoa was further investigated by means of light and transmission electron microscopy (TEM).

Results

Only viable Chlamydiae of both species decreased sperm motility and this only after about 9 h. Taking binding rates into account, the loss of sperm motility after about 9 h could likely be a consequence of Chlamydiae attachment to the spermatozoa. About two thirds of the Chlamydiae elementary bodies were bound to the front third of the sperm, the acrosomal region. No inclusions of Chlamydiae in spermatozoa were observed in TEM after 2 h co-incubation.

Conclusions

As initial motility was not affected following co-incubation of viable Chlamydiae and bovine sperm, it seems likely that sperm could serve as a carrier/vehicle for Chlamydiae facilitating cervical passage of Chlamydiae spp. in cattle. Additionally, our results suggest that spermatozoa carrying Chlamydiae may have no initial disadvantage in reaching the oviduct, but are immotile at the time of ovulation what might have an impact on fertilization capacities of the individual sperm. Consequently, high concentrations of the investigated Chlamydiae in the seminal plasma or female genital tract might play a role in reduced fertility in cattle.

Metal-Assisted Assembly of Protein Containers Loaded with Inorganic Nanoparticles

Protein containers are suitable building blocks for bioinorganic materials. Here, we show that high concentrations of magnesium ions induce the formation of a unitary protein scaffold, whereas low magnesium concentration leads to a binary protein scaffold. The molecular interactions in the protein scaffold were characterized with X-ray crystallography to high resolution. We show that the unitary framework can be applied for the assembly of inorganic nanoparticles such as metal oxides into highly ordered bioinorganic structures. Our work emphasizes the structural tunability of protein-container-based materials, important for adjusting emerging properties of such materials.

The 12C(n, 2n)11C cross section from threshold to 26.5 MeV

The ¹²C(n, 2n)¹¹C cross section was measured from just below threshold to 26.5 MeV using the Pelletron accelerator at Ohio University. Monoenergetic neutrons, produced via the ³H(d,n)⁴He reaction, were allowed to strike targets of polyethylene and graphite. Activation of both targets was measured by counting positron annihilations resulting from the β⁺ decay of ¹¹C. Annihilation gamma rays were detected, both in coincidence and singly, using back-to-back NaI detectors. The incident neutron flux was determined indirectly via ¹H(n,p) protons elastically scattered from the polyethylene target. Previous measurements fall into upper and lower bands; the results of the present measurement are consistent with the upper band.

Structure-Function Relationships of Antimicrobial Peptides and Proteins with Respect to Contact Molecules on Pathogen Surfaces

The Antimicrobial peptides (e.g. defensins, hevein-like molecules and food-protecting peptides like nisin) are able to interact specifically with contact structures on pathogen surfaces. Besides protein receptors, important recognition points for such contacts are provided by pathogen glycan chains or surface lipids. Therefore, structural data concerning surface exposed glycans and lipids are of the highest clinical interest since these recognition functions play a key role when optimising anti-infection therapies. Approaches in nanomedicine and nanopharmacology in which various biophysical techniques such as NMR (Nuclear Magnetic Resonance), AFM (Atomic Force Microscopy), SPR (Surface Plasmon Resonance) and X-ray crystallography can be combined with biochemical and cell-biological methods will lead to improved antimicrobial peptides by this rational drug design approach. Such a strategy is extremely well suited to support clinical studies focussing on an effective fight against multiresistant pathogens. The data sets which are described here can be considered as universal for the design of various antimicrobial drugs against certain pathogens (bacteria, viruses and fungi) which cause severe diseases in humans and animals. Furthermore, these insights are also helpful for progressing developments in the field of food conservation and food preservation. A detailed analysis of the structure-function relationships between antimicrobial peptides and contact molecules on pathogen surfaces at the sub-molecular level will lead to a higher degree of specificity of antimicrobial peptides.

Molecular Basis of the Receptor Interactions of Polysialic Acid (polySia), polySia Mimetics, and Sulfated Polysaccharides

Polysialic acid (polySia) and polySia glycomimetic molecules support nerve cell regeneration, differentiation, and neuronal plasticity. With a combination of biophysical and biochemical methods, as well as data mining and molecular modeling techniques, it is possible to correlate specific ligand-receptor interactions with biochemical processes and in vivo studies that focus on the potential therapeutic impact of polySia, polySia glycomimetics, and sulfated polysaccharides in neuronal diseases. With this strategy, the receptor interactions of polySia and polySia mimetics can be understood on a submolecular level. As the HNK-1 glycan also enhances neuronal functions, we tested whether similar sulfated oligo- and polysaccharides from seaweed could be suitable, in addition to polySia, for finding potential new routes into patient care focusing on an improved cure for various neuronal diseases. The knowledge obtained here on the structural interplay between polySia or sulfated polysaccharides and their receptors can be exploited to develop new drugs and application routes for the treatment of neurological diseases and dysfunctions.

Dynamics of suspensions of hydrodynamically structured particles: analytic theory and applications to experiments

We present an easy-to-use analytic toolbox for the calculation of short-time transport properties of concentrated suspensions of spherical colloidal particles with internal hydrodynamic structure, and direct interactions described by a hard-core or soft Hertz pair potential. The considered dynamic properties include self-diffusion and sedimentation coefficients, the wavenumber-dependent diffusion function determined in dynamic scattering experiments, and the high-frequency shear viscosity. The toolbox is based on the hydrodynamic radius model (HRM) wherein the internal particle structure is mapped on a hydrodynamic radius parameter for unchanged direct interactions, and on an existing simulation data base for solvent-permeable and spherical annulus particles. Useful scaling relations for the diffusion function and self-diffusion coefficient, known to be valid for hard-core interaction, are shown to apply also for soft pair potentials. We further discuss extensions of the toolbox to long-time transport properties including the low-shear zero-frequency viscosity and the long-time self-diffusion coefficient. The versatility of the toolbox is demonstrated by the analysis of a previous light scattering study of suspensions of non-ionic PNiPAM microgels [Eckert et al., J. Chem. Phys., 2008, 129, 124902] in which a detailed theoretical analysis of the dynamic data was left as an open task. By the comparison with Hertz potential based calculations, we show that the experimental data are consistently and accurately described using the Verlet-Weis corrected Percus-Yevick structure factor as input, and for a solvent penetration length equal to three percent of the excluded volume radius. This small amount of solvent permeability of the microgel particles has a significant dynamic effect at larger concentrations.

Comparison of the Microstructure of Stimuli Responsive Zwitterionic PNIPAM-co-Sulfobetaine Microgels with PNIPAM Microgels and Classical Hard-Sphere Systems

In this study, we compare the experimental static structure factors of concentrated solutions of amphoteric poly(N-isopropylacrylamide) (PNIPAM) microgels with those of the polydisperse hard-sphere model. We use zwitterionic microgels as model systems for amphoteric microgels with an equal amount of positive and negative charges located in a defined distance. Using small angle neutron scattering (SANS), we measure the static structure factors, S M(q), of a series of zwitterionic microgels with increasing amount of zwitterion, including a reference sample of pure PNIPAM. The experimental S M(q) is compared with predictions based on the Percus-Yevick approximation for hard spheres. We also compare with the PNIPAM reference sample measured for zwitterionic microgels. We find no significant influence of the zwitterionic comonomer on the effective pair potential. The PNIPAM and the zwitterionic microgels can be described by the hard-sphere model for smaller volume fractions ϕ T  ≲ 0.4 only.

Effects of architecture on the stability of thermosensitive unimolecular micelles

The influence of architecture on polymer interactions is investigated and differences between branched and linear copolymers are found. A comprehensive picture is drawn with the help of a fluorescence approach (using pyrene and 4HP as probe molecules) together with IR or NMR spectroscopy and X-ray/light scattering measurements. Five key aspects are addressed: (1) synergistic intramolecular complexation within miktoarm stars. The proximity of thermoresponsive poly(propylene oxide) (PPO) and poly(dimethylaminoethyl methacrylate) (PDMAEMA) within a miktoarm star leads to complexation between these weakly interacting partners. Consequently, the original properties of the constituents are lost, showing hydrophobic domains even at low temperatures, at which all homopolymers are water soluble. (2) Unimolecular micelles for miktoarm stars. The star does not exhibit intermolecular self-assembly in a large temperature range, showing unimers up to 55 °C. This behavior was traced back to a reduced interfacial tension between the PPO-PDMAEMA complex and water (PDMAEMA acts as a "microsurfactant"). (3) Unimolecular to multimolecular micelle transition for stars. The otherwise stable unimolecular micelles self-assemble above 55 °C. This aggregation is not driven by PPO segregation, but by collapse of residual PDMAEMA. This leads to micrometer-sized multilamellar vesicles stabilized by poly(ethylene oxide) (PEO). (4) Prevention of pronounced complexation within diblock copolymers. In contrast to the star copolymers, PPO and PDMAEMA adapt rather their homopolymer behavior within the diblock copolymers. Then they show their immanent LCST properties, as PDMAEMA turns insoluble at elevated temperatures, whereas PPO becomes hydrophobic below room temperature. (5) Two-step micellization for diblock copolymers. Upon heating of linear copolymers, the dehydration of PPO is followed by self-assembly into spherical micelles. An intermediate prevalence of unimolecular micelles is revealed in a small temperature window between PPO collapse and self-assembly of PEO-b-PPO. Also for PPO-b-PDMAEMA, PPO segregation prevails after initial weak complexation, leading to micelles with a PPO core. Considerable amounts of water are entrapped within the collapsed PDMAEMA domains above 55 °C (skin effect), preventing PPO-PDMAEMA complexation within precipitating PPO-b-PDMAEMA. Further, collapsed PDMAEMA is rather polar as sensed by pyrene and 4HP. In summary, advanced macromolecular architectures can lead to an unprecedented intramolecular self-assembly behavior, where internal complexation prevents intermolecular aggregation.