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Arteriosclerosis, Thrombosis, and... Mar 2011Fibrin structure and stability have been linked to many thrombotic diseases, including venous thromboembolism. Analysis of the molecular mechanisms that affect fibrin... (Review)
Review
Fibrin structure and stability have been linked to many thrombotic diseases, including venous thromboembolism. Analysis of the molecular mechanisms that affect fibrin structure and stability became possible when the crystal structure of fibrinogen was solved. Biochemical studies of natural and recombinant variant fibrinogens have examined the interactions that mediate the conversion of soluble fibrinogen to the insoluble fibrin network. These studies identified intermolecular interactions that control fibrin structure, although some critical events remain ambiguous. Studies show that fibrin structure modulates the enzymatic lysis of the fibrin network, so the molecular mechanisms that control structure also control stability. Studies show that the mechanical stability of the fibrin clot depends on the properties of the fibrin monomer, leading investigators to explore the molecular basis of the monomer's mechanical properties. The work summarized here provides insights that might allow the development of pharmaceuticals and treatments to modulate fibrin structure and stability in vivo and thereby prevent or limit thrombotic disease.
Topics: Animals; Blood Coagulation; Fibrin; Fibrinogen; Fibrinolysis; Fibrinolytic Agents; Humans; Protein Conformation; Structure-Activity Relationship; Venous Thrombosis
PubMed: 21325671
DOI: 10.1161/ATVBAHA.110.213389 -
Polymers Jun 2016Nowadays, "green" is a hot topic almost everywhere, from retailers to universities to industries; and achieving a green status has become a universal aim. However,... (Review)
Review
Nowadays, "green" is a hot topic almost everywhere, from retailers to universities to industries; and achieving a green status has become a universal aim. However, polymers are commonly considered not to be "green", being associated with massive energy consumption and severe pollution problems (for example, the "Plastic Soup") as a public stereotype. To achieve green polymers, three elements should be entailed: (1) green raw materials, catalysts and solvents; (2) eco-friendly synthesis processes; and (3) sustainable polymers with a low carbon footprint, for example, (bio)degradable polymers or polymers which can be recycled or disposed with a gentle environmental impact. By utilizing biobased monomers in enzymatic polymerizations, many advantageous green aspects can be fulfilled. For example, biobased monomers and enzyme catalysts are renewable materials that are derived from biomass feedstocks; enzymatic polymerizations are clean and energy saving processes; and no toxic residuals contaminate the final products. Therefore, synthesis of renewable polymers via enzymatic polymerizations of biobased monomers provides an opportunity for achieving green polymers and a future sustainable polymer industry, which will eventually play an essential role for realizing and maintaining a biobased and sustainable society.
PubMed: 30974520
DOI: 10.3390/polym8070243 -
Nucleic Acids Research Feb 1992In the primate genome, a typical Alu element corresponds to a dimeric structure composed of two different but related monomeric sequences arranged in tandem. However,...
In the primate genome, a typical Alu element corresponds to a dimeric structure composed of two different but related monomeric sequences arranged in tandem. However, the analysis of primate sequences found in GenBank reveals the presence of free left and free right Alu elements. Here, we report the statistical study of those monomeric elements. We found that only a small fraction of them results from a deletion of a dimeric Alu sequence. The majority derives from the amplification of monomeric progenitor sequences and constitutes two families of monomeric elements: a family of free left Alu monomers that is composed of two subfamilies and a small family of free right Alu monomers. Both families predated the dimeric Alu elements, and a phylogenetic analysis strongly suggests that the first progenitor of the dimeric Alu family arose through the fusion of a free left monomer with a free right monomer.
Topics: Animals; Base Sequence; Consensus Sequence; Mathematics; Molecular Sequence Data; Multivariate Analysis; Primates; Repetitive Sequences, Nucleic Acid; Sequence Alignment
PubMed: 1741283
DOI: 10.1093/nar/20.3.487 -
Proceedings of the Japan Academy.... 2022Introduction of functional groups on polyethylene endows it with a higher surface property and thus various catalysts have been developed for the copolymerization of... (Review)
Review
Introduction of functional groups on polyethylene endows it with a higher surface property and thus various catalysts have been developed for the copolymerization of ethylene with polar vinyl monomers. Aside from vinyl monomers, however, other classes of polar monomers have not found application in the copolymerization with ethylene. Here, in this short review article, our latest studies on catalyst development aiming at the use of non-vinyl polar monomers and the properties of the resulting copolymers are summarized.
Topics: Catalysis; Ethylenes; Polymerization; Polymers
PubMed: 35545528
DOI: 10.2183/pjab.98.014 -
Molecules (Basel, Switzerland) Feb 2022The three-dimensional structure of monomers and homodimers of CYP102A1/WT (wild-type) proteins and their A83F and A83I mutant forms was predicted using the AlphaFold2...
Prediction of Monomeric and Dimeric Structures of CYP102A1 Using AlphaFold2 and AlphaFold Multimer and Assessment of Point Mutation Effect on the Efficiency of Intra- and Interprotein Electron Transfer.
The three-dimensional structure of monomers and homodimers of CYP102A1/WT (wild-type) proteins and their A83F and A83I mutant forms was predicted using the AlphaFold2 (AF2) and AlphaFold Multimer (AFMultimer) programs, which were compared with the rate constants of hydroxylation reactions of these enzyme forms to determine the efficiency of intra- and interprotein electron transport in the CYP102A1 hydroxylase system. The electron transfer rate constants (), which determine the rate of indole hydroxylation by the CYP102A1 system, were calculated based on the distances (R) between donor-acceptor prosthetic groups (PG) FAD→FMN→HEME of these proteins using factor β, which describes an exponential decay from R the speed of electron transport (ET) according to the tunnelling mechanism. It was shown that the structure of monomers in the homodimer, calculated using the AlpfaFold Multimer program, is in good agreement with the experimental structures of globular domains (HEME-, FMN-, and FAD-domains) in CYP102A1/WT obtained by X-ray structural analysis, and the structure of isolated monomers predicted in AF2 does not coincide with the structure of monomers in the homodimer, although a high level of similarity in individual domains remains. The structures of monomers and homodimers of A83F and A83I mutants were also calculated, and their structures were compared with the wild-type protein. Significant differences in the structure of all isolated monomers with respect to the structures of monomers in homodimers were also found for them, and at the same time, insignificant differences were revealed for all homodimers. Comparative analysis for CYP102A1/WT between the calculated intra- and interprotein distances FAD→FMN→HEME and the rate constants of hydroxylation in these proteins showed that the distance between prosthetic groups both in the monomer and in the dimer allows the implementation of electron transfer between PGs, which is consistent with experimental literature data about . For the mutant form of monomer A83I, an increase in the distance between PGs was obtained, which can restrict electron transportation compared to WT; however, for the dimer of this protein, a decrease in the distance between PGs was observed compared to the WT form, which can lead to an increase in the electron transfer rate constant and, accordingly, . For the monomer and homodimer of the A83F mutant, the calculations showed an increase in the distance between the PGs compared to the WT form, which should have led to a decrease in the electron transfer rate, but at the same time, for the homodimer, the approach of the aromatic group F262 with heme can speed up transportation for this form and, accordingly, the rate of hydroxylation.
Topics: Bacterial Proteins; Cytochrome P-450 Enzyme System; Electron Transport; Models, Molecular; NADPH-Ferrihemoprotein Reductase; Point Mutation; Protein Binding; Protein Conformation; Protein Multimerization; Structure-Activity Relationship
PubMed: 35209175
DOI: 10.3390/molecules27041386 -
Polymers Mar 2021Commonly, volumetric shrinkage occurs during polymerizations due to the shortening of the equilibrium Van der Waals distance of two molecules to the length of a... (Review)
Review
Commonly, volumetric shrinkage occurs during polymerizations due to the shortening of the equilibrium Van der Waals distance of two molecules to the length of a (significantly shorter) covalent bond. This volumetric shrinkage can have severe influence on the materials' properties. One strategy to overcome this volumetric shrinkage is the use of expanding monomers that show volumetric expansion during polymerization reactions. Such monomers exhibit cyclic or even oligocyclic structural motifs with a correspondingly dense atomic packing. During the ring-opening reaction of such monomers, linear structures with atomic packing of lower density are formed, which results in volumetric expansion or at least reduced volumetric shrinkage. This review provides a concise overview of expanding monomers with a focus on the elucidation of structure-property relationships. Preceded by a brief introduction of measuring techniques for the quantification of volumetric changes, the most prominent classes of expanding monomers will be presented and discussed, namely cycloalkanes and cycloalkenes, oxacycles, benzoxazines, as well as thiocyclic compounds. Spiroorthoesters, spiroorthocarbonates, cyclic carbonates, and benzoxazines are particularly highlighted.
PubMed: 33800726
DOI: 10.3390/polym13050806 -
Heliyon Nov 2022Hartree-Fock (HF) and Density Functional Theory (DFT) studies were conducted to assess the impact of potassium doping on the thermodynamic, optoelectronic, electronic...
Impact of doping on the optoelectronic, electronic and nonlinear optical properties and on the reactivity of photochromic polymers containing styrylquinoline fragments: Hartree-Fock and DFT study.
Hartree-Fock (HF) and Density Functional Theory (DFT) studies were conducted to assess the impact of potassium doping on the thermodynamic, optoelectronic, electronic and nonlinear optical properties and on the reactivity of photochromic polymers containing styrylquinoline fragments. Doping was carried out on the virgin monomer (M1) and on the derivative monomer (M2) with the nitro group NO. Three doped monomers were investigated including, the monomer M3 obtained from M1 by substituting the H atom with a potassium, the monomer M4 by substituting two H atoms and the monomer M5 obtained from M2 by substituting the H atom. Findings proved that the use of potassium and the nitro group is an excellent process to improve the electronics properties of styrylquinoline virgin monomers. In fact, the energy gap decreases from 3.82 eV for M1 to 3.02 eV and to 2.92 eV for M3 and M4, respectively; while the decrease from 3.43 eV for M2 to 2.52 eV for M5 was observed, thus demonstrating the good semiconductor character of the obtained compounds with relevant applications in the manufacture of solar cells. Likewise, the fundamental gap decreases from 6.50 eV for M1 to 5.34 eV and to 4.62 eV for M3 and M4, respectively; while the decrease from 6.11 eV for M2 to 5.21 eV for M5 was observed; thus demonstrating an improvement in the reactivity of our doped monomers. In addition, potassium doping is an appropriate method to enhance optoelectronic properties of styrylquinoline virgin monomers. Thus, the refractive index of our doped monomers is greater than that of glass, which is a reference in optic and can be used under high electric fields of the order of Vm for monomer M4 up to Vm for M3 and to Vm for M5. Finally, the strong enhancement of the linear and nonlinear optical (NLO) properties that we observed leads us to conclude that these doped monomers can be appropriate candidates in devices requiring good NLO properties.
PubMed: 36411919
DOI: 10.1016/j.heliyon.2022.e11491 -
Proceedings of the National Academy of... Mar 1979High-symmetry models of the fibrin fiber are proposed that reproduce the experimentally observed high specific volume of the fiber. The models meet the following...
High-symmetry models of the fibrin fiber are proposed that reproduce the experimentally observed high specific volume of the fiber. The models meet the following criteria: fibrin monomers have the three-domain Hall and Slayter structure; the monomers are arranged lengthwise into strands (protofibrils) in which successive monomers half overlap; the monomers' alignment is nearly parallel to the fiber axis; and the monomers make adequate longitudinal and lateral contacts, as required by observed fiber properties and the high affinity of monomers for one another. All the models contain helical protofibrils related to each other by rotation axes parallel to the fiber axis; as a consequence the protofibrils are in register in the fiber direction. The protofibrils may contain two, three, or four monomers per helical turn and can be packed in four different symmetries (space groups). A large specific volume is achieved only if the D-domain (which are presumed to contain the lateral polymerization sites) are somewhat displaced from the helical axes of the protofibrils. This displacement may involve either a lateral shift of the monomers away from the helix axis or a tilt of the monomers, which swings the D-domains away from the helix axis. It is shown that the fiber containing tilted monomers is more highly interconnected; the two D-domains of each tilted monomer form lateral contacts with different adjacent protofibrils, whereas the two D-domains of each nontilted monomer contact the same adjacent protofibril(s).
Topics: Fibrin; Fibrinogen; Macromolecular Substances; Models, Molecular; Protein Conformation
PubMed: 286304
DOI: 10.1073/pnas.76.3.1189 -
Dental Materials : Official Publication... May 2019Methacrylamides are proposed as components for dental adhesive systems with enhanced resistance to hydrolytic and enzymatic degradation. The specific objective of this...
OBJECTIVES
Methacrylamides are proposed as components for dental adhesive systems with enhanced resistance to hydrolytic and enzymatic degradation. The specific objective of this study was to evaluate the polymerization kinetics, water sorption and solubility, pH-derived degradation and microtensile bond strength of various monofunctional acrylamides and meth(acrylamides) when copolymerized with dimethacrylates.
METHODS
Base monomers were added at 60 wt%, and included either BisGMA or UDMA. Monofunctional monomers were added at 40 wt%, including one (meth)acrylate as the control, two secondary methacrylamides and two tertiary acrylamides. DMPA (0.2 wt%) and DPI-PF6 (0.4 wt%)/BHT (0.1 wt%) were added as initiators/inhibitor. Polymerization kinetics wwere followed with near-IR spectroscopy in real time. Water sorption (WS) and solubility (SL) were measured following ISO 4049. Monomer degradation at different pH levels was assessed with H NMR. Microtensile bond strength (MTBS) was assessed in caries-free human third molars 48 h and 3 weeks after restorations were placed using solvated BisGMA-based adhesives (40 vol% ethanol). Data were analyzed with one-way ANOVA/Tukey's test (α = 0.05).
RESULTS
As expected, rate of polymerization and final degree of conversion (DC) were higher for the acryl versions of each monomer, and decreased with increasing steric hindrance around the vinyl group for each molecule. In general, UDMA copolymerizations were more rapid and extensive than for BisGMA, but this was dependent upon the specific monofunctional monomer added. WS/SL were in general higher for the (meth)acrylamides compared to the (meth)acrylates, except for the tertiary acrylamide, which showed the lowest values. One of the secondary methacrylamides was significantly more stable than the methacrylate control, but the alpha substitutions decreased stability to degradation in acid pH. MTBS in general was higher for the (meth)acrylates. While for all materials the MTBS values at 3 weeks decreased in relation to the 24 h results, the tertiary acrylamide showed no reduction in bond strength.
SIGNIFICANCE
This study highlights the importance of considering steric and electronic factors when designing monomers for applications where rapid polymerizations are needed, especially when co-polymerizations with other base monomers are required to balance mechanical properties, as is the case with dental adhesives. The results of this investigation will be used to design fully formulated adhesives to be tested in clinically-relevant conditions.
Topics: Acrylamides; Bisphenol A-Glycidyl Methacrylate; Composite Resins; Dental Bonding; Dental Cements; Humans; Materials Testing; Methacrylates; Polymerization; Tensile Strength; Water
PubMed: 30826074
DOI: 10.1016/j.dental.2019.02.012 -
Materials (Basel, Switzerland) May 2021Most of the dental materials available on the market are still based on traditional monomers such as bisphenol A-glycidyl methacrylate (Bis-GMA), urethane dimethacrylate...
Most of the dental materials available on the market are still based on traditional monomers such as bisphenol A-glycidyl methacrylate (Bis-GMA), urethane dimethacrylate (UDMA), triethyleneglycol dimethacrylate (TEGDMA), and ethoxylated bisphenol-A dimethacrylate (Bis-EMA). The interactions that arise in the monomer mixture and the characteristics of the resulting polymer network are the most important factors, which define the final properties of dental materials. The use of three different monomers in proper proportions may create a strong polymer matrix. In this paper, fourteen resin materials, based on urethane dimethacrylate with different co-monomers such as Bis-GMA or Bis-EMA, were evaluated. TEGDMA was used as the diluting monomer. The flexural strength (FS), diametral tensile strength (DTS), and hardness (HV) were determined. The impacts of material composition on the water absorption and dissolution were evaluated as well. The highest FS was 89.5 MPa, while the lowest was 69.7 MPa. The median DTS for the tested materials was found to range from 20 to 30 MPa. The hardness of the tested materials ranged from 14 to 16 HV. UDMA/TEGDMA matrices were characterized by the highest adsorption values. The overall results indicated that changes in the materials' properties are not strictly proportional to the material's compositional changes. The matrices showed good properties when the composite contained an equal mixture of Bis-GMA/Bis-EMA and UDMA or the content of the UDMA monomer was higher.
PubMed: 34064213
DOI: 10.3390/ma14112727