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.

Spastin's microtubule-binding properties and comparison to katanin

Spastin and katanin are ring-shaped hexameric AAA ATPases that sever microtubules, and thus crucially depend on a physical interaction with microtubules. For the first time, we report here the microtubule binding properties of spastin at the single-molecule level, and compare them to katanin. Microscopic fluorescence assays showed that human spastin bound to microtubules by ionic interactions, and diffused along microtubules with a diffusion coefficient comparable to katanin. The microscopic measurement of landing and dissociation rates demonstrated the ionic character of the interaction, which could be mapped to a patch of three lysine residues outside of the catalytic domain of human spastin. This motif is not conserved in Drosophila spastin or katanin, which also bound by non-catalytic parts of the protein. The binding affinities of spastin and katanin were nucleotide-sensitive, with the lowest affinities under ADP,, the highest under ATP-γS conditions. These changes correlated with the formation of higher oligomeric states, as shown in biochemical experiments and electron microscopic images. Vice versa, the artificial dimerization of human spastin by addition of a coiled coil led to a constitutively active enzyme. These observations suggest that dimer formation is a crucial step in the formation of the active complex, and thus the severing process by spastin.

Uncoupled eNOS annihilates neuregulin-1β-induced cardioprotection: a novel mechanism in pharmacological postconditioning in myocardial infarction

Myocardial infarct size can be limited by pharmacological postconditioning (pPC) with cardioprotective agents. Cardioprotective effects of neuregulin-1β (NRG) via activation of protein kinase B (Akt) and downstream pathways like endothelial nitric oxide synthase (eNOS) have been postulated based on results from cell culture experiments. The purpose of this study was to investigate if eNOS may be involved in pPC with NRG. NRG application in an ex vivo mouse model (C57Bl6) of ischemia-reperfusion injury was analyzed. Unexpectedly, the infarct size increased when NRG was infused starting 5 min prior to reperfusion, even though protective Akt and GSK3β phosphorylation were enhanced. In eNOS deficient mice, however, NRG significantly reduced the infarct size. Co-infusion of NRG and L-arginine (Arg) lead to a reduction in infarct size in wild type animals. Electron paramagnetic resonance measurements revealed that NRG treatment prior to reperfusion leads to an enhanced release of reactive oxygen species compared to controls and this effect is blunted by co-infusion of Arg. This study documents the cardioprotective mechanisms of NRG signaling to be mediated by GSK3β inactivation. This is the first study to show that this protection fails in situations with dysfunctional eNOS. In eNOS deficient mice NRG exerts its protective effect via the GSK3β pathway, suggesting that the eNOS can limit cardioprotection. As dysfunctional eNOS has been described in cardiovascular risk factors like diabetes, hypertension, and hypercholesterolemia these findings can help to explain lack of postconditioning performance in models of cardiovascular co-morbidities.

Large carbon isotope fractionation during biodegradation of chloroform by Dehalobacter cultures

Compound specific isotope analysis (CSIA) has been applied to monitor bioremediation of groundwater contaminants and provide insight into mechanisms of transformation of chlorinated ethanes. To date there is little information on its applicability for chlorinated methanes. Moreover, published enrichment factors (ε) observed during the biotic and abiotic degradation of chlorinated alkanes, such as carbon tetrachloride (CT); 1,1,1-trichloroethane (1,1,1-TCA); and 1,1-dichloroethane (1,1-DCA), range from -26.5‰ to -1.8‰ and illustrate a system where similar C-Cl bonds are cleaved but significantly different isotope enrichment factors are observed. In the current study, biotic degradation of chloroform (CF) to dichloromethane (DCM) was carried out by the Dehalobacter containing culture DHB-CF/MEL also shown to degrade 1,1,1-TCA and 1,1-DCA. The carbon isotope enrichment factor (ε) measured during biodegradation of CF was -27.5‰ ± 0.9‰, consistent with the theoretical maximum kinetic isotope effect for C-Cl bond cleavage. Unlike 1,1,1-TCA and 1,1-DCA, reductive dechlorination of CF by the Dehalobacter-containing culture shows no evidence of suppression of the intrinsic maximum kinetic isotope effect. Such a large fractionation effect, comparable to those published for cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC) suggests CSIA has significant potential to identify and monitor biodegradation of CF, as well as important implications for recent efforts to fingerprint natural versus anthropogenic sources of CF in soils and groundwater.

Size-dependent multispectral photoacoustic response of solid and hollow gold nanoparticles

Photoacoustic (PA) imaging attracts a great deal of attention as an innovative modality for longitudinal, non-invasive, functional and molecular imaging in oncology. Gold nanoparticles (AuNPs) are identified as superior, NIR-absorbing PA contrast agents for biomedical applications. Until now, no systematic comparison of the optical extinction and PA efficiency of water-soluble AuNPs of various geometries and small sizes has been performed. Here spherical AuNPs with core diameters of 1.0, 1.4 and 11.2 nm, nanorods with longitudinal/transversal elongation of 38/9 and 44/12 nm and hollow nanospheres with outer/inner diameters of 33/19, 57/30, 68/45 and 85/56 nm were synthesized. The diode laser set-up with excitations at 650, 808, 850 and 905 nm allowed us to correlate the molar PA signal intensity with the molar extinction of the respective AuNPs. Deviations were explained by differences in heat transfer from the particle to the medium and, for larger particles, by the scattering of light. The molar PA intensity of 1.0 nm AuNPs was comparable to the commonly used organic dye methylene blue, and rapidly increased with the lateral size of AuNPs.

Subunit Interactions and cooperativity in the microtubule-severing AAA ATPase spastin

Spastin is a hexameric ring AAA ATPase that severs microtubules. To see whether the ring complex funnels the energy of multiple ATP hydrolysis events to the site of mechanical action, we investigate here the cooperativity of spastin. Several lines of evidence indicate that interactions among two subunits dominate the cooperative behavior: (i) the ATPase activity shows a sigmoidal dependence on the ATP concentration; (ii) ATPγS displays a mixed-inhibition behavior for normal ATP turnover; and (iii) inactive mutant subunits inhibit the activity of spastin in a hyperbolic dependence, characteristic for two interacting species. A quantitative model based on neighbor interactions fits mutant titration experiments well, suggesting that each subunit is mainly influenced by one of its neighbors. These observations are relevant for patients suffering from SPG4-type hereditary spastic paraplegia and explain why single amino acid exchanges lead to a dominant negative phenotype. In severing assays, wild type spastin is even more sensitive toward the presence of inactive mutants than in enzymatic assays, suggesting a weak coupling of ATPase and severing activity.

Network correlates of disease severity in multiple system atrophy

OBJECTIVE

Multiple system atrophy (MSA), the most common of the atypical parkinsonian disorders, is characterized by the presence of an abnormal spatial covariance pattern in resting state metabolic brain images from patients with this disease. Nonetheless, the potential utility of this pattern as a MSA biomarker is contingent upon its specificity for this disorder and its relationship to clinical disability in individual patients.

METHODS

We used [(18)F]fluorodeoxyglucose PET to study 33 patients with MSA, 20 age- and severity-matched patients with idiopathic Parkinson disease (PD), and 15 healthy volunteers. For each subject, we computed the expression of the previously characterized metabolic covariance patterns for MSA and PD (termed MSARP and PDRP, respectively) on a prospective single-case basis. The resulting network values for the individual patients were correlated with clinical motor ratings and disease duration.

RESULTS

In the MSA group, disease-related pattern (MSARP) values were elevated relative to the control and PD groups (p < 0.001 for both comparisons). In this group, MSARP values correlated with clinical ratings of motor disability (r = 0.57, p = 0.0008) and with disease duration (r = -0.376, p = 0.03). By contrast, MSARP expression in the PD group did not differ from control values (p = 1.0). In this group, motor ratings correlated with PDRP (r = 0.60, p = 0.006) but not with MSARP values (p = 0.88).

CONCLUSIONS

MSA is associated with elevated expression of a specific disease-related metabolic pattern. Moreover, differences in the expression of this pattern in patients with MSA correlate with clinical disability. The findings suggest that the MSARP may be a useful biomarker in trials of new therapies for this disorder.

Polystyrene-block-polyglycidol micelles cross-linked with titanium tetraisopropoxide. laser light and small-angle X-ray scattering studies on their formation in solution

Hybrid micelles from polystyrene-block-polyglycidol (PS-b-PG) copolymers with chemically cross-linked cores by titanium tetraisopropoxide (Ti(OC(3)H(7))(4)) were prepared in toluene solution. Additionally, micellization of PS-b-PG copolymers with different mass fractions of polyglycidol (x(PG)), was studied by static and dynamic light scattering as well as small-angle X-ray scattering. It was observed that copolymers with x(PG) smaller than 0.5 self-assembled in toluene into spherical core-shell micelles with hydrodynamic radii R(h) between 12 and 23 nm. On the other hand, copolymers with larger PG content formed particles with R(h) = 50-70 nm and aggregation numbers of several thousands. The presence of these aggregates in solution was attributed to the nonequilibrated form of block copolymers upon dissolving, most probably due to hydrogen bonding. In the following, spherical PS-b-PG micelles were loaded in toluene with hydrochloric acid and titanium tetraisopropoxide. Confined hydrolysis of Ti(OC(3)H(7))(4) induced by HCl in the micellar core was confirmed by small-angle X-ray scattering experiments. The subsequent condensation of the precursor with hydroxyl groups of polyglycidol chains led to covalently stabilized hybrid organic-inorganic particles. The presence of cross-linked PS-b-PG micelles was proven in two ways. First, micelles with "frozen" core showed stable hydrodynamic size in time upon dilution below critical micellization concentration while non-cross-linked PS-b-PG micelles underwent disintegration under the same conditions within several hours. Second, light scattering experiments revealed the presence of stable, swollen particles in N,N-dimethylformamide, which is a good solvent for both blocks.

Interaction of the α2A domain of integrin with small collagen fragments

We here present a detailed study of the ligand-receptor interactions between single and triple-helical strands of collagen and the α2A domain of integrin (α2A), providing valuable new insights into the mechanisms and dynamics of collagen-integrin binding at a sub-molecular level. The occurrence of single and triple-helical strands of the collagen fragments was scrutinized with atom force microscopy (AFM) techniques. Strong interactions of the triple-stranded fragments comparable to those of collagen can only be detected for the 42mer triple-helical collagen-like peptide under study (which contains 42 amino acid residues per strand) by solid phase assays as well as by surface plasmon resonance (SPR) measurements. However, changes in NMR signals during titration and characteristic saturation transfer difference (STD) NMR signals are also detectable when α2A is added to a solution of the 21mer single-stranded collagen fragment. Molecular dynamics (MD) simulations employing different sets of force field parameters were applied to study the interaction between triple-helical or single-stranded collagen fragments with α2A. It is remarkable that even single-stranded collagen fragments can form various complexes with α2A showing significant differences in the complex stability with identical ligands. The results of MD simulations are in agreement with the signal alterations in our NMR experiments, which are indicative of the formation of weak complexes between single-stranded collagen and α2A in solution. These results provide useful information concerning possible interactions of α2A with small collagen fragments that are of relevance to the design of novel therapeutic A-domain inhibitors.

Optical experiments on a crystallizing hard-sphere-polymer mixture at coexistence

We report on the crystallization kinetics in an entropically attractive colloidal system using a combination of time resolved scattering methods and microscopy. Hard sphere particles are polystyrene microgels swollen in a good solvent (radius a=380 nm, starting volume fraction 0.534) with the short ranged attractions induced by the presence of short polymer chains (radius of gyration r g=3 nm, starting volume fraction 0.0224). After crystallization, stacking faulted face centered cubic crystals coexist with about 5% of melt remaining in the grain boundaries. From the Bragg scattering signal we infer the amount of crystalline material, the average crystallite size and the number density of crystals as a function of time. This allows to discriminate an early stage of conversion, followed by an extended coarsening stage. The small angle scattering (SALS) appears only long after completed conversion and exhibits Furukawa scaling for all times. Additional microscopic experiments reveal that the grain boundaries have a reduced Bragg scattering power but possess an increased refractive index. Fits of the Furukawa function indicate that the dimensionality of the scatterers decreases from 2.25 at short times to 1.65 at late times and the characteristic length scale is slightly larger than the average crystallite size. Together this suggests the SALS signal is due scattering from a foam like grain boundary network as a whole.

Why structurally different cyclic peptides can be glycomimetics of the HNK-1 carbohydrate antigen

The cyclic peptides c-(LSETTl) and c-(RTLPFS) are of potential clinical interest--they stimulate neurite outgrowth in a way that is similar to the effects of the HNK-1 (human natural killer cell-1) antigenic carbohydrate chains, which are terminated by 3'-sulfated glucuronic acid attached to an N-acetyllactosamine unit. To investigate the structure-activity relationships of the ability of the cyclic peptides to mimic HNK-1 carbohydrates, conformational analysis and examination of hydrophobic and hydrophilic patterns were performed and compared with the characteristics of a synthetic HNK-1 trisaccharide derivative. Data obtained demonstrate that both the trisaccharide and the glycomimetic peptide c-(LSETTl) exhibit a similar relationship between their hydrophobic moieties and their negatively charged sites. However, the second cyclic glycomimetic peptide investigated here, c-(RTLPFS), has a positively charged group as a potential contact point due to its Arg residue. Therefore, we studied the amino acid composition of all known receptor structures in the Protein Data Bank that are in contact with uronic acid and/or sulfated glycans. Interactions of the HNK-1 trisaccharide, c-(LSETTl), and c-(RTLPFS) with a laminin fragment involved in HNK-1 carbohydrate binding (i.e., the 21mer peptide: KGVSSRSYVGCIKNLEISRST) were also analyzed. Because the structure of the HNK-1-binding laminin domain is not available in the Protein Data Bank, we used the HNK-1-binding 21mer peptide fragment of laminin for the construction of a model receptor that enabled us to compare the molecular interplay of the HNK-1 trisaccharide and the two cyclopeptides c-(LSETTl) and c-(RTLPFS) with a reliable receptor structure in considerable detail.

WITHDRAWN: Corrigendum to "A lectin from the Chinese bird-hunting spider binds sialic acids"

The Publisher regrets that this article is an accidental duplication of an article that has already been published, doi: 10.1016/j.carres.2010.01.003. The duplicate article has therefore been withdrawn.

Metabolic networks for assessment of therapy and diagnosis in Parkinson's disease

Neuroimaging and modern computational techniques like spatial covariance analysis have contributed greatly to the understanding of neural system abnormalities in neurodegenerative disorders such as Parkinson's disease (PD). The application of network analysis to metabolic PET data obtained from patients with PD has led to the identification and validation of two distinct spatial covariance patterns associated with the motor and cognitive manifestations of the disease. Quantifying the activity of these patterns in individual subjects has provided an objective tool for the assessment of treatment efficacy and differential diagnosis. We have found that activity of the PD motor-related network is modulated by antiparkinsonian treatments such as dopaminergic therapy, deep brain stimulation (DBS), and subthalamic nucleus (STN) gene therapy. By contrast, the cognitive-related network is not altered by these interventions for PD motor symptoms. This pattern may however change in response to therapies targeting the cognitive symptoms of this disorder. Recent work has focused on the identification of specific network biomarkers for atypical parkinsonian conditions such as multiple system atrophy (MSA) and progressive supranuclear palsy (PSP). These disease-related patterns can potentially be used in an automated imaging-based algorithm to classify patients with these disorders.

A case of influenza vaccination induced Guillain Barré syndrome with normal cerebrospinal fluid protein and improvement on treatment with corticosteroids

We report a case of a 62-y-old male developing an influenza vaccination induced Guillain Barré syndrome (GBS) showing all clinical and neuropathological symptoms of GBS except the characteristic elevation of protein levels in the cerebrospinal fluid. The patient improved under treatment with 100 mg prednisolone. In these cases the administration of corticosteroids might be considered as a treatment option as they might represent a subgroup of GBS with a different immunological response pattern.

A novel sequence variation in the transactivation regulating domain of the human androgen receptor

OBJECTIVE

To study a novel sequence variation within the androgen receptors' N-terminal CAG repeat region and possible resulting consequences for the receptors' three-dimensional (3D) protein structure.

DESIGN

Controlled clinical study.

SETTING

University research and andrology clinic.

PATIENT(S)

Twenty-one adult infertile men.

INTERVENTION(S)

Ultraviolet laser-assisted microdissection (PALM, Microlaser Technology AG, Bernried, Germany), cloning into pGEM-T vector (Promega, Madison, WI), automated sequencing (Gene Scan 3.7 ABI Prim, Applied Biosystems, Foster City, CA), and Assisted Model Building with Energy Refinement (AMBER).

MAIN OUTCOME MEASURE(S)

Determination of the sequence of the CAG repeat of the androgen receptor gene and analysis of the 3D protein structure.

RESULTS(S)

In one hypergonadotropic azoospermic patient with Sertoli-cell-only syndrome, we found a punctual sequence variation of 212A-->G in the CAG repeat resulting in a glutamine-arginine substitution, which leads to a moderate conformational change of the alpha-helix from 34 A in length and 16 A in diameter (without mutation) to a slightly longer helix (43 A) with a smaller diameter (15 A).

CONCLUSION(S)

Whether the novel 212A-->G exchange in the CAG repeat leading to a glutamine-->arginine substitution and a change in alpha-helix structure may causally be related to the Sertoli-cell-only phenotype of the patient remains to be elucidated.

Implications of bevacizumab on vascular endothelial growth factor and endostatin in human choroidal neovascularisation

AIM

To evaluate the implications of intravitreal bevacizumab on proangiogenic vascular endothelial growth factor (VEGF) with regard to the endogenous angiogenesis inhibitor endostatin in human choroidal neovascularisation (CNV) secondary to age-related macular degeneration.

METHODS

Retrospective review of an interventional case series of 48 patients who underwent full macular translocation surgery with removal of CNV. Twenty-five patients were treated with intravitreal bevacizumab injection 1 to 154 days prior to surgery (bevacizumab CNV). Twenty-three CNV without any kind of previous treatment were used as controls (control CNV). CNV were stained for CD34, cytokeratin18, VEGF, endostatin and E-selectin. A "predominance score of VEGF over endostatin" (PS) was defined by the difference between VEGF and endostatin staining scores.

RESULTS

Bevacizumab CNV revealed a weaker VEGF expression in endothelial cells (p = 0.0245) but significantly more intense endostatin in retina pigment epithelium (RPE) (p = 0.0001) and stroma (p<0.0001). Consequently, PS was significantly lower in RPE (p = 0.02), vessels (p = 0.03) and stroma (p = 0.0004) in bevacizumab CNV. The intensity of E-selectin expression in bevacizumab CNV was comparable with that in control CNV.

CONCLUSIONS

A shift within the angiogenic balance in terms of decreased VEGF predominance over endostatin is detected in human CNV treated with bevacizumab.