Monomer Level Research Articles

Frondoside A Attenuates Amyloid-β Proteotoxicity in Transgenic Caenorhabditis elegans by Suppressing Its Formation

Oligomeric assembly of Amyloid-β (Aβ) is the main toxic species that contribute to early cognitive impairment in Alzheimer’s patients. Therefore, drugs that reduce the formation of Aβ oligomers could halt the disease progression. In this study, by using transgenic Caenorhabditis elegans model of Alzheimer’s disease, we investigated the effects of frondoside A, a well-known sea cucumber Cucumaria frondosa saponin with anti-cancer activity, on Aβ aggregation and proteotoxicity. The results showed that frondoside A at a low concentration of 1 µM significantly delayed the worm paralysis caused by Aβ aggregation as compared with control group. In addition, the number of Aβ plaque deposits in transgenic worm tissues was significantly decreased. Frondoside A was more effective in these activities than ginsenoside-Rg3, a comparable ginseng saponin. Immunoblot analysis revealed that the level of small oligomers as well as various high molecular weights of Aβ species in the transgenic C. elegans were significantly reduced upon treatment with frondoside A, whereas the level of Aβ monomers was not altered. This suggested that frondoside A may primarily reduce the level of small oligomeric forms, the most toxic species of Aβ. Frondoside A also protected the worms from oxidative stress and rescued chemotaxis dysfunction in a transgenic strain whose neurons express Aβ. Taken together, these data suggested that low dose of frondoside A could protect against Aβ-induced toxicity by primarily suppressing the formation of Aβ oligomers. Thus, the molecular mechanism of how frondoside A exerts its anti-Aβ aggregation should be studied and elucidated in the future.

Poly-Amido-Saccharides (PASs): Functional Synthetic Carbohydrate Polymers Inspired by Nature.

Carbohydrates are ubiquitous in nature, playing vital roles in all organisms ranging from metabolism to intercellular signaling. Polysaccharides, repeating units of small molecule carbohydrates, are hydrophilic, densely functionalized, stereoregular, and rigid macromolecules, and these characteristics are simultaneously advantageous in biomedical applications while presenting major hurdles for synthetic methodology and development of structure property relationships. While naturally obtained polysaccharides are widely utilized in the biochemical and medical literature, their poor physicochemical definition and the potential for contaminated samples hinders the clinical translation of this work. To address the need for new methods to synthesize carbohydrate polymers, we reported a novel class of biomaterials (Poly-Amido-Saccharides; PAS) in 2012. PASs share many properties with natural polysaccharides, such as hydrophilicity, dense hydroxyl functionality, stereoregularity, and a rigid backbone. PASs are connected by an α-1,2-amide linkage, instead of an ether linkage, that confers resistance to enzymatic and hydrolytic degradation and leads to a unique helical conformation. Importantly, our synthetic methodology affords control over molecular weight distribution resulting in pure, well-defined polymers. This Account provides an overview of the development of PAS, from the factors that initially motivated our research to current efforts to translate functional PAS to biomedical applications. We detail the synthesis of glucose- and galactose-based PAS and their biophysical properties including conformation analysis, lectin interactions, cell internalization, and water solubility. Additionally, we describe postpolymerization modification strategies to afford PASs that act as protein stabilizers. We also highlight our recent efforts toward a mechanistic understanding of monomer synthesis via [2 + 2] cycloaddition reactions in order to develop novel monomers with different stereochemistry and amine or alkyl functionality, thereby accessing functional carbohydrate polymers. Throughout our work, we apply computational and theoretical analysis to explain how properties at the monomer level (e.g., stereochemistry, functionality) significantly impact polymer properties, helical conformation, and bioactivities. Collectively, the results from the theoretical, synthetic, and applied aspects of this research advance us toward our goal of utilizing PASs in key biomedical applications as alternatives to natural polysaccharides. The importance of carbohydrates in nature and the versatility of their functions continue to inspire our investigation of new monomers, polymers, and copolymers, leveraging the advantageous properties of PAS to develop potential therapies.

Estimation of Alpha-Synuclein Monomer and Oligomer Levels in the Saliva of the Children With Autism Spectrum Disorder: A Possibility for an Early Diagnosis.

BackgroundIn degenerative brain diseases like Parkinson's disease (PD), alpha-synuclein (a-syn) can be in its monomeric (a-syn-mono) or toxic oligomeric (a-syn-oligo) or as a total (a-syn-total) forms in the biological body fluids including saliva. Past research has observed major a-syn plasma variations in children with autism spectrum disorder (ASD) pointing toward brain degenerative components in their pathophysiology. No prior study has shown a-syn levels in ASD patients' saliva.Objective This study estimates the levels of alpha-synuclein monomer (a-syn-mono) and alpha-synuclein oligomer (a-syn-oligo) in the saliva of ASD affected children so that saliva can be a method for detecting disorder.Materials and methodsThis cross-sectional, multi-center study was conducted in Islamic International Medical College, Autism Resource Centre (ARC), and Step-to-learn Rehabilitation center for the slow learner in Rawalpindi. The research was performed for one year from August 2018 to August 2019. Saliva samples from 80 children (40 ASD affected children, and 40 age- and sex-comparable healthy controls) were collected. Specific anti-alpha-synuclein monomers (anti-a-syn-mono) and anti-alpha-synuclein oligomers (anti-a-syn-oligo) enzyme-linked immunosorbent assay (ELISA) kits analyzed the salivary samples. Mean ± SD were reported for quantitative data. The data between the two groups were compared using an independent t-test. The p-value of ≤ 0.05 was considered statistically significant.ResultsA total of 80 children were included in the study (n=40 ASD affected, n=40 healthy controls). The age of participating children was between four and eight years. The mean alpha-synuclein monomer level in the saliva of ASD children was 92.03 ± 117.09 pg/ml (p≤0.05), and in healthy subjects was 186.78 ± 239.31 ρg/ml. The levels of alpha-synuclein oligomer in the saliva of patients with ASD children were 0.13 ± 0.05 ng/ml (p<0.001), and in the healthy subjects was 0.33 ± 0.26 ng/ml. Both alpha-synuclein monomer and alpha-synuclein oligomer levels were low in the saliva of ASD children.ConclusionChildren with ASD had low levels of alpha-synuclein monomer and oligomer than healthy children which are unique than that of levels found in other degenerative brain diseases.

Structures of the intrinsically disordered Aβ, tau and α-synuclein proteins in aqueous solution from computer simulations

Intrinsically disordered proteins (IDPs) play many biological roles in the human proteome ranging from vesicular transport, signal transduction to neurodegenerative diseases. The Aβ and tau proteins, and the α-synuclein protein, key players in Alzheimer’s and Parkinson’s diseases, respectively are fully disordered at the monomer level. The structural heterogeneity of the monomeric and oligomeric states and the high self-assembly propensity of these three IDPs have precluded experimental structural determination. Simulations have been used to determine the atomic structures of these IDPs. In this article, we review recent computer models to capture the equilibrium ensemble of Aβ, tau and α-synuclein proteins at different association steps in aqueous solution and present new results of the PEP-FOLD framework on α-synuclein monomer.

Development of a New Coarse-Grained Model to Simulate Assembly of Cellulose Chains Due to Hydrogen Bonding.

In this work, we present a new coarse-grained (CG) model that captures the directional hydrogen bonding interactions that drive cellulose chains to assemble into ordered aggregates. This CG model balances the incorporation of chemical details at the monomer level needed to represent directional interactions and the coarse-graining needed to capture large length scales and time scales associated with macromolecular assembly. We validate this CG model by first comparing the cellulose single-chain structure in the CG molecular dynamics (MD) simulations with that in atomistic MD simulations. We also compare the hydrogen bonding pattern, interchain distance, and interchain orientation seen in assembled cellulose chains observed in CG MD simulations with those seen in experimental crystal structures of cellulose. Upon validation, we present the aggregation behavior of cellulose chains with "silenced" hydrogen bonding site interactions to mimic cellulose chains that are chemically modified at the donor and acceptor hydrogen bonding sites (e.g., methylcellulose). We expect this type of CG model to be useful in predicting the morphology of cellulose chains in solution under a wide range of solution conditions and chemical modifications.

Electromechanical fatigue of dielectric viscoelastomers

Dielectric elastomers (DEs) have extensive applications. However, their applications are commonly limited by fatigue damage since DEs are often subjected to cyclic electromechanical load. In this work, the fatigue life of dielectric elastomers under various electromechanical loads is investigated with a theory developed through configurational mechanics. The simulation results are also interpreted from the monomer level. Under charge-induced actuation, the fatigue damage of dielectric elastomers is dictated by the polarization of dipoles. Moreover, the polymerization degree and the portion of free chains exert a significant effect on the fatigue life of dielectric elastomers. It is concluded that a longer fatigue life is expected for dielectric elastomers under charge-induced actuation than mechanical deformation.

The origin of biological homochirality along with the origin of life.

How homochirality concerning biopolymers (DNA/RNA/proteins) could have originally occurred (i.e., arisen from a non-life chemical world, which tended to be chirality-symmetric) is a long-standing scientific puzzle. For many years, people have focused on exploring plausible physic-chemical mechanisms that may have led to prebiotic environments biased to one chiral type of monomers (e.g., D-nucleotides against L-nucleotides; L-amino-acids against D-amino-acids)-which should have then assembled into corresponding polymers with homochirality, but as yet have achieved no convincing advance. Here we show, by computer simulation-with a model based on the RNA world scenario, that the biased-chirality may have been established at polymer level instead, just deriving from a racemic mixture of monomers (i.e., equally with the two chiral types). In other words, the results suggest that the homochirality may have originated along with the advent of biopolymers during the origin of life, rather than somehow at the level of monomers before the origin of life.

Interface engineering of microelectrodes toward ultrasensitive monitoring of β-amyloid peptides in cerebrospinal fluid in Alzheimer's disease.

Ultrasensitive detection of monomeric β-amyloid peptides is of fundamental significance for studying the pathological progression of Alzheimer's disease (AD). In this article, by facilely engineering a gold microelectrode interface, we developed a novel electrochemical biosensor for sensitive and selective monitoring of β-amyloid peptide (Aβ) monomers in cerebrospinal fluid (CSF). Through specific Cu2+-Aβ-hemin coordination, Aβ directed the assembly of Cu2+-PEI/AuNPs-hemin nanoprobes into network aggregates on a microelectrode interface, which promoted the enrichment of Aβ monomers on the microelectrode. Furthermore, the AuNP aggregate promotes the deposition of silver nanoparticles, which were utilized for the electrochemical stripping analysis of the Aβ monomer. The proposed method displayed ultra-sensitivity for Aβ monomers with the detection limit down to 0.2 pM. Besides, high selectivity toward Aβ monomers was observed. These remarkable analytical performances render the electrochemical biosensor useful for evaluating the dynamic change of Aβ monomer level in CSF of live mice with AD, promoting the investigation of the role that Aβ monomers play in brain events.

Local and Global Stretching of Polymer Chains during Startup of Extensional Flow.

The nonlinear rheological response to extensional flows in entangled polymers is related to the segmental chain stretching and to the chemical identity of the monomeric units. The latter has a strong effect on the drag coefficients, and therefore, quantification of molecular conformation changes in the subnanometer scale (at the monomer level) are crucial to fully understand nonlinear viscoelastic behavior in polymer melts. We report in situ time-resolved extensional rheo-small-angle neutron scattering (tEr-SANS) and wide-angle X-ray scattering (tEr-WAXS) during startup of uniaxial flow on a monodisperse polystyrene melt. Flow-induced segmental alignment was quantified with tEr-SANS, whereas local alignment of the backbone-backbone and phenyl-phenyl interactions were measured with tEr-WAXS. Linear relations between the three alignment factors and stress were observed at low stresses, which confirmed the validity of simple stress-SANS and stress-WAXS rules (SSR and SWR, respectively). Significant differences in SSR and SWR coefficients, as well as the stress values for failure of the two rules suggest very different correlations between global (at the segmental level) and local (at the monomer level) conformations with stress.

Computational Reverse-Engineering Analysis for Scattering Experiments on Amphiphilic Block Polymer Solutions

In this paper, we present a computational reverse-engineering analysis for scattering experiments (CREASE) based on genetic algorithms and molecular simulation to analyze the structure within self-assembled amphiphilic polymer solutions. For a given input comprised of scattering intensity profiles and information about the amphiphilic polymers in solution, CREASE outputs the structure of the self-assembled micelles (e.g., core and corona diameters, aggregation number) as well as the conformations of the amphiphilic polymer chains in the micelle (e.g., blocks' radii of gyration, chain radii of gyration, monomer concentration profiles). First, we demonstrate CREASE's ability to reverse-engineer self-assembled nanostructures for scattering profiles obtained from molecular simulations (or in silico experiments) of generic coarse-grained bead-spring polymer chains in an implicit solvent. We then present CREASE's outputs for scattering profiles obtained from small-angle neutron scattering (SANS) experiments of poly(d-glucose carbonate) block copolymers in solution that exhibit assembly into spherical nanoparticles. The success of this method is demonstrated by its ability to replicate, quantitatively, the results from in silico experiments and by the agreement in micelle core and corona sizes obtained from microscopy of the in vitro solutions. The primary strength of CREASE is its ability to analyze scattering profiles without an off-the-shelf scattering model and the ability to provide chain and monomer level structural information that is otherwise difficult to obtain from scattering and microscopy alone.

Energy Exchange Network Model Demonstrates Protein Allosteric Transition: An Application to an Oxygen Sensor Protein.

The effects of ligand binding on an oxygen sensor protein, FixLH, were investigated by molecular dynamics simulation. To illustrate the network of residue interactions in the deoxy, oxy, and carbomonoxy states of FixLH, we employed the energy exchange network (EEN) model in which residue interactions were evaluated in terms of local transport coefficients of energy flow. As a result, the difference map of EEN between the deoxy and oxy (deoxy and carbomonooxy) states clearly demonstrated the allosteric transition, although the structural changes by ligand binding are small. It is known that the FixLH forms a homodimer in solution, although neither O2 nor CO binding exhibits cooperativity. Therefore, we conjectured that the primary event after ligand binding occurs essentially at the monomer level, and it is subsequently followed by quaternary structural changes. The difference EEN maps showed that two regions, (A) the junction between the coiled-coil linker and the sensor domain and (B) the potential dimer interface, experienced considerable change of the energy-transport coefficients, indicating that these two regions play important roles in quaternary structural changes and signal transduction in response to ligand binding.

Relative Contribution of Framework and CDR Regions in Antibody Variable Domains to Multimerisation of Fv- and scFv-Containing Bispecific Antibodies.

Bispecific antibodies represent an emerging class of antibody drugs that are commonly generated by fusion of Fv or scFv antigen binding domains to IgG or Fab scaffolds. Fv- or scFv-mediated multimerisation of bispecific antibodies via promiscuous vH-vL pairing can result in sub-optimal monomer levels during expression, and hence, undesirable therapeutic protein yields. We investigate the contribution of disulphide stabilised Fv and scFv to Fab-Fv and Fab-scFv multimerisation. We show that monomer levels of isolated Fv/scFv cannot always be used to predict monomer levels of Fab-linked Fv/scFv, and that Fab-scFv monomer levels are greater than the equivalent Fab-Fv. Through grafting bispecifics with framework/CDR-‘swapped’ Fv and scFv, we show that monomer levels of disulphide stabilised Fab-Fv and Fab-scFv can be improved by Fv framework ‘swapping’. The Fab-Fv and Fab-scFv can be considered representative of the significant number of bispecific antibody formats containing appended Fv/scFv, as we also used Fv framework ‘swapping’ to increase the monomer level of an IgG-scFv bispecific antibody. This research may, therefore, be useful for maximising the monomeric yield of numerous pharmaceutically-relevant bispecific formats in pre-clinical development.

Concurrent improvements in crosslinking degree and interfacial adhesion of hemp fibers reinforced acrylated epoxidized soybean oil composites

Biocomposites with high performance and biobased contents were prepared from renewable feedstocks, i.e., hemp fibers (HFs) and acrylated epoxidized soybean oil (AESO). Two bifunctional isocyanates, i.e., isocyanatoethyl methacrylate (IEM) and 3-isopropenyldimethylbenzyl isocyanate (TMI), were used as reactive diluents for AESO, respectively. The incorporated IEM or TMI carrying both CC bonds and isocyanate groups not only crosslinked with the CC bonds of AESO by a free-radical polymerization, but also reacted with the –OH groups of both AESO and HFs to concurrently improve the unsaturation level of AESO monomers and the interfacial adhesion between HFs and AESO matrix, which was verified by FTIR and DSC analyses. Both IEM-AESO and TMI-AESO resins exhibited favorable viscosities and curing temperatures for the production of HFs-reinforced composites while without the emission of hazardous air pollutants. The composite with 15 wt% IEM modified AESO (based on the total weight of IEM-AESO blend) had comparable tensile and flexural strengths with the composite from 30 wt% styrene; while the 15 wt% TMI resulting composite obtained higher tensile strength and modulus as well as flexural strength and modulus than the composites from 15 wt% IEM or 30 wt% styrene. This indicated that TMI has a higher reinforcing efficiency on the composites than IEM. Significant improvements in storage modulus, glass transition temperature, and water resistance were obtained for the composites from IEM or TMI relative to the composite from pure AESO resin, which is attributed to the simultaneously improved crosslinking density and interfacial adhesion of the composites as confirmed by SEM analysis.

Efficient and simplified nanomechanical analysis of intrinsically disordered proteins.

Intrinsically disordered proteins (IDPs) lack a tertiary structure. Amyloidogenic IDPs (aIDPs) in particular have attracted great interest due to their implication in several devastating diseases as well as in critical biological functions. However, the conformational changes that trigger amyloid formation in aIDPs are largely unknown. aIDPs' conformational polymorphism at the monomer level encumbers their study using bulk techniques. Single-molecule techniques like atomic force microscopy-based single-molecule force spectroscopy represent a promising approach and a "carrier-guest" strategy, in which the protein of interest is mechanically protected, was developed to overcome the spurious signals from the noisy proximal region. However, since the carrier and single-molecule markers have similar mechanostabilities, their signals can intermingle in the force-extension recordings, making peak selection and analysis very laborious, cumbersome and prone to error for the non-expert. Here we have developed a new carrier, the c8C module from the CipC scaffoldin, with a higher mechanostability so that the signals from the protected protein will appear at the end of the recordings. This assures an accurate, more efficient and expert-independent analysis, simplifying both the selection and analysis of the single-molecule data. Furthermore, this modular design can be integrated into any SMFS polyprotein-based vector, thus constituting a useful utensil in the growing toolbox of protein nanomechanics.

Detection of protonated non-Watson-Crick base pairs using electrospray ionization mass spectrometry.

Many studies have shown that protonated nucleic acid base pairs are involved in a wide variety of nucleic acid structures. However, little information is available on relative stability of hemiprotonated self- and non-self-dimers at monomer level. We used electrospray ionization mass spectrometry (ESI-MS) to evaluate the relative stability under various concentrations of hydrogen ion. These enable conjecture of the formation of protonated non-Watson-Crick base pairs based on DNA and RNA base sequence. In the present study, we observed that ESI-MS peaks corresponded to respective self-dimers for all examined nucleosides except for adenosine. Peak heights depended on the concentration of hydrogen ion. The ESI-MS peak heights of the hemiprotonated cytidine dimers and the hemiprotonated thymidine dimer sharply increased with increased concentration of hydrogen ion, suggesting direct participation of hydrogen ion in dimer formations. In ESI-MS measurements of the solutions containing adenosine, cytidine, thymidine and guanosine, we observed protonated cytidine-guanosine dimer (CH+-G) and protonated cytidine-thymidine dimer (CH+-T) in addition to hemiprotonated cytidine-cytidine dimer (CH+-C) with following relative peak height, (CH+-C) > (CH+-G) ≈ (CH+-T) > (CH+-A). Additionally, in the ESI-MS measurements of solutions containing adenosine, thymidine and guanosine, we observed a considerable amount of protonated adenosine-guanosine (AH+-G) and protonated adenosine-thymidine (AH+-T).

The ubiquitin conjugating enzyme Ube2W regulates solubility of the Huntington's disease protein, huntingtin

Huntington's disease (HD) is caused by a CAG repeat expansion that encodes a polyglutamine (polyQ) expansion in the HD disease protein, huntingtin (HTT). PolyQ expansion promotes misfolding and aggregation of mutant HTT (mHTT) within neurons. The cellular pathways, including ubiquitin-dependent processes, by which mHTT is regulated remain incompletely understood. Ube2W is the only ubiquitin conjugating enzyme (E2) known to ubiquitinate substrates at their amino (N)-termini, likely favoring substrates with disordered N-termini. By virtue of its N-terminal polyQ domain, HTT has an intrinsically disordered amino terminus. In studies employing immortalized cells, primary neurons and a knock-in (KI) mouse model of HD, we tested the effect of Ube2W deficiency on mHTT levels, aggregation and neurotoxicity. In cultured cells, deficiency of Ube2W activity markedly decreases mHTT aggregate formation and increases the level of soluble monomers, while reducing mHTT-induced cytotoxicity. Consistent with this result, the absence of Ube2W in HdhQ200 KI mice significantly increases levels of soluble monomeric mHTT while reducing insoluble oligomeric species. This study sheds light on the potential function of the non-canonical ubiquitin-conjugating enzyme, Ube2W, in this polyQ neurodegenerative disease.

Synthesis of Altrose Poly-amido-saccharides with β-N-(1→2)-d-amide Linkages: A Right-Handed Helical Conformation Engineered in at the Monomer Level.

The design and synthesis of amide-linked saccharide oligomers and polymers, which are predisposed to fold into specific ordered secondary structures, is of significant interest. Herein, right-handed helical poly amido-saccharides (PASs) with β-N-(1→2)-d-amide linkages are synthesized by the anionic ring-opening polymerization of an altrose β-lactam monomer (alt-lactam). The right-handed helical conformation is engineered into the polymers by preinstalling the β configuration of the lactam ring in the monomer via the stereospecific [2+2] cycloaddition of trichloroacetyl isocyanate with a d-glycal possessing a 3-benzyloxy group oriented to the α-face of the pyranose. The tert-butylacetyl chloride initiated polymerization of the alt-lactam proceeds smoothly to afford stereoregular polymers with narrow dispersities. Birch reduction of the benzylated polymers gives water-soluble altrose PASs (alt-PASs) in high yields without degradation of the polymer backbone. Circular dichroism analysis shows the alt-PASs adopt a right-handed helical conformation in aqueous solutions. This secondary conformation is stable over a wide range of different conditions, such as pH (2.0 to 12.0), temperature (5 to 75 °C), ionic salts (2.0 M LiCl, NaCl, and KCl), as well as in the presence of protein denaturants (4.0 M urea and guanidinium chloride). Cytotoxicity studies reveal that the alt-PASs are nontoxic to HEK, HeLa, and NIH3T3 cells. The results showcase the ability to direct solution conformation of polymers through monomer design. This approach is especially well-suited and straightforward for PASs as the helical conformations formed result from constraints imposed by the relatively rigid and sterically bulky repeating units.

Specific sequences in the N-terminal domain of human small heat-shock protein HSPB6 dictate preferential hetero-oligomerization with the orthologue HSPB1

Small heat-shock proteins (sHSPs) are a conserved group of molecular chaperones with important roles in cellular proteostasis. Although sHSPs are characterized by their small monomeric weight, they typically assemble into large polydisperse oligomers that vary in both size and shape but are principally composed of dimeric building blocks. These assemblies can include different sHSP orthologues, creating additional complexity that may affect chaperone activity. However, the structural and functional properties of such hetero-oligomers are poorly understood. We became interested in hetero-oligomer formation between human heat-shock protein family B (small) member 1 (HSPB1) and HSPB6, which are both highly expressed in skeletal muscle. When mixed in vitro, these two sHSPs form a polydisperse oligomer array composed solely of heterodimers, suggesting preferential association that is determined at the monomer level. Previously, we have shown that the sHSP N-terminal domains (NTDs), which have a high degree of intrinsic disorder, are essential for the biased formation. Here we employed iterative deletion mapping to elucidate how the NTD of HSPB6 influences its preferential association with HSPB1 and show that this region has multiple roles in this process. First, the highly conserved motif RLFDQXFG is necessary for subunit exchange among oligomers. Second, a site ∼20 residues downstream of this motif determines the size of the resultant hetero-oligomers. Third, a region unique to HSPB6 dictates the preferential formation of heterodimers. In conclusion, the disordered NTD of HSPB6 helps regulate the size and stability of hetero-oligomeric complexes, indicating that terminal sHSP regions define the assembly properties of these proteins.

Molecular dynamics simulations of hexopyranose ring distortion in different force fields

Abstract The four classical, biomolecular force fields designed to study hexopyranose-based carbohydrates (GROMOS 56a6CARBO/56a6CARBO_R, GROMOS 53a6GLYC, CHARMM and GLYCAM06) have been tested in the context of ring-inversion properties. These properties were evaluated for both unfunctionalized monomers of all hexopyranoses of the d series and for residues in a chain composed of uniform units connected by α(1→4) and β(1→4) glycosidic linkages. The results indicate that the tested force fields differ in their predictions of the ring-inversion properties of both monomers and residues in a chain. The comparison with the available experimental data and with the semi-empirical Angyal scheme reveals that, at the level of monomers, GROMOS 56a6CARBO, GROMOS 53a6GLYC and CHARMM correctly reproduce the ring-inversion free energies. However, due to the lack of analogous reference data we cannot state which force field is more or less accurate in the context of ring distortion of residues in a chain. Therefore, the use of ab initio potentials is recommended in the prospective, quantitative studies on the related subject.

P-064: Measures of thrombodynamics test and fibrin monomer level in pregnant women with complicated obstetric history

P-064: Measures of thrombodynamics test and fibrin monomer level in pregnant women with complicated obstetric history