Molecular Mass Distribution Research Articles

Polycondensation Kinetics: 2. Time-Dependent29Si NMR Spectra of Poly-Dimethyldimethoxysilane

The polycondensation of dimethyldimethoxysilane has been studied by 29Si NMR to high degrees of conversion at pH 2.8. The relative concentrations of nonbonded Si atoms (D0) and bound by one (D1) and two (D2) Si–O–Si bonds have been determined from the integrated intensities of the multiplets assigned to them. The measurement results have been considered in terms of the kinetic scheme proposed in the first paper. It has been found that the D0(t), D1(t), and D2(t) curves coincide with those measured for the ratio of the constants of competing processes of aggregation and addition of monomers k ≈ 0.15. The time-dependent molecular mass distributions have been determined with allowance for chain termination during the formation of cyclic and entangled oligomers.

Influence of Group Hydrocarbon Composition of Diesel Fuels on Depressant Additive Efficiency

The physicochemical properties of nine summer base diesel fuels were compared. The influence of the group hydrocarbon composition on the low-temperature properties was examined using two fuels with similar physicochemical properties as examples. The physicochemical characteristics of the fuel were shown not to be definitive, rather, its detailed group chemical composition reflecting the molecular-mass distribution of n-alkanes and ratio of mono-, bi-, and polycyclic aromatic hydrocarbons that affect the injectivity of the fuel additives was important. A study of the cold filter plugging point and pour point of these fuels in the presence of two depressant additives based on ethylene-vinyl acetate copolymers showed that additive 1 exhibited more universal properties in fuels differing in group chemical composition while additive 2 reduced effectively the cold filter plugging point in fuels with lower contents of high-melting n-alkanes and exhibited pour point depression comparable to that of additive 1 in fuels with high contents of this hydrocarbon group.

Molecular Signatures of Humic Acids from Different Sources as Revealed by Ultrahigh Resolution Mass Spectrometry

Humic acid (HA) is extremely important for understanding the geochemical cycle of pollutants in different environments. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has performed molecular-level analysis of two standard HAs from the Suwannee River (SRHA) and leonardite (LEHA) and HA from Jiufeng forest in Beijing (JFHA), which is impossible for other conventional instruments. Regardless of the source of HA, compounds containing more heteroatoms (such as nitrogen and sulfur) have a higher degree of unsaturation and aromaticity. JFHA, SRHA, and LEHA from soil, river, and leonardite, respectively, are arranged in order from the lowest to highest degree of humification, according to molecular unsaturation and aromaticity of HAs. Soil HA is more labile and contains many large molecular weight compounds with low unsaturation. Regardless of unsaturation, molecules of River HA have a homogeneous molecular mass distribution and contain many plant-derived lignin- and tannin-like compounds, which are more stable than lipid and more labile than condensed aromatics. Leonardite HA with a high degree of humification contains a large number of compounds with high aromaticity and more heteroatoms and has low lability. Our results reveal the diversity of humic acid at molecular level because of different degree of humification and the lability. These conclusions are significant for understanding the role of humic acid from different sources in pollutant transformation and the geochemical cycle at the molecular level.

Proteins Features of the Far Eastern Region Bivalve Mollusk Mactra Сhinensis

Bivalve mollusk are protein raw materials, their soft tissues are characterized by a hard-rubbery consistency due to its proteins characteristics and should be considered when processing into food. The proteins fractional composition study of different groups (water-soluble, myofibrillar, and stroma) is an urgent task, since it is possible to justify the processing technology based on the obtained data. The article presents the fractional composition study results of the water-soluble proteins and peptides, the molecular mass distribution of the separate components of myofibrillary proteins and muscle tissue stroma proteins of the Mactra Chinensis mollusk motor muscle. The researchers noted that the total amount of the high-molecular fraction (molecular weight above 10 kDa) is 62.16 %, and the total peptide fraction amount (molecular weight below 10 kDa) is 37.84 %. There are four main components in myofibrillar proteins – myosin, actin, troponin complex components, and collagen. The content of the main myofibrillar protein that is myosin of various polymerization degrees of is 69.3 %; heavy myosin chains – 30.5 % of the total myofibrillar proteins content and 44.0 % of the relative content of the total myosin content; light myosin chains – 38.8 % of the total myofibrillar proteins content and 56.0 % of the relative content of the total myosin content. The authors determined that actin (molecular weight 43 kDa) and troponin complex components (molecular weight from 15 to 30 kDa) are approximately equal in content. The collagen content (molecular weight more than 300 kDa) in the myofibrillar fraction is only 8.2 %. Stroma proteins are represented by two main fractions with molecular weights of more than 250 and 500 kDa. Collagen is the predominant stroma protein, its content account for 62.6 %. There is a high connectin content in stroma proteins.

Polycondensation Kinetics: 1. Bifunctional Organosilicon Monomers

Polycondensation of bifunctional organosilicon monomers as a chain unbranched process includes initiation (hydrolysis of nonreactive end groups), propagation (sequential addition of monomers and bimolecular aggregation of n-mers), and termination (cyclization and entanglement of end groups in a nonreactive environment). Kinetic models of these steps with a minimum number of rate constants have been proposed. It has been shown that the chain propagation pathways involving different end groups are mixed and the competition of the chain growth and termination processes determines the molecular mass distribution of oligomers and their fractal packing in nanoscale aggregates.

The Oil-Bearing Strata of Permian Deposits of the Ashal’cha Oil Field Depending on the Content, Composition, and Thermal Effects of Organic Matter Oxidation in the Rocks

The features of the oil-bearing capacity of the productive strata of Permian deposits in the interval of 117.5-188.6 m along the section of individual wells of the Ashal’cha field of heavy superviscous oil (Tatarstan) were revealed depending on the content, composition, and thermal effects of organic matter (OM) oxidation in the rocks. It is shown that the rocks are very heterogeneous in their mineral composition and in the content of both free hydrocarbons by extraction with organic solvents and insoluble OM closely associated with the rock. The total content of OM in rocks varies from 1.72 to 9.12%. The features of group and hydrocarbon composition of extracts from rocks are revealed depending on their mineral composition and the content of organic matter in them. According to the molecular mass distribution of alkanes of normal and isoprenoid structure, extracts from rocks are differentiated according to three chemical types of oil: type A1, in which n-alkanes of composition C14 and above are present, and types A2 and B2, in which n-alkanes are destroyed to varying degrees by processes microbial destruction, which indicates a different intensity of biochemical processes in productive strata of Permian sediments. These processes lead to a decrease in the amount of OM in the rocks and an increase in the content of resins and asphaltenes in the oil extracted from them, as well as an increase in the viscosity of the oil. Using the method of differential scanning calorimetry of high pressure, it was found that the studied rock samples differ from each other in quantitative characteristics of exothermic effects in both low-temperature (LTO) 200-350°С and high-temperature (HTO) 350-600°С zones of OM oxidation. The total thermal effect of destruction processes of OM depends on the content of OM in the rocks and its composition. The research results show that when heavy oil is extracted using thermal technologies, the Permian productive strata with both low and high OM contents will be involved in the development, and the general thermal effect of the oxidation of which will contribute to increased oil recovery.

Corrigendum to “The Oil-Bearing Strata of Permian Deposits of the Ashal’cha Oil Field Depending on the Content, Composition, and Thermal Effects of Organic Matter Oxidation in the Rocks”

The features of the oil-bearing capacity of the productive strata of Permian deposits in the interval of 117.5-188.6 m along the section of individual wells of the Ashal’cha field of heavy superviscous oil (Tatarstan) were revealed depending on the content, composition, and thermal effects of organic matter (OM) oxidation in the rocks. It is shown that the rocks are very heterogeneous in their mineral composition and in the content of both free hydrocarbons by extraction with organic solvents and insoluble OM closely associated with the rock. The total content of OM in rocks varies from 1.72 to 9.12%. The features of group and hydrocarbon composition of extracts from rocks are revealed depending on their mineral composition and the content of organic matter in them. According to the molecular mass distribution of alkanes of normal and isoprenoid structure, extracts from rocks are differentiated according to three chemical types of oil: type A1, in which n-alkanes of composition C14 and above are present, and types A2 and B2, in which n-alkanes are destroyed to varying degrees by processes microbial destruction, which indicates a different intensity of biochemical processes in productive strata of Permian sediments. These processes lead to a decrease in the amount of OM in the rocks and an increase in the content of resins and asphaltenes in the oil extracted from them, as well as an increase in the viscosity of the oil. Using the method of differential scanning calorimetry of high pressure, it was found that the studied rock samples differ from each other in quantitative characteristics of exothermic effects in both low-temperature (LTO) 200-350°С and high-temperature (HTO) 350-600°С zones of OM oxidation. The total thermal effect of destruction processes of OM depends on the content of OM in the rocks and its composition. The research results show that when heavy oil is extracted using thermal technologies, the Permian productive strata with both low and high OM contents will be involved in the development, and the general thermal effect of the oxidation of which will contribute to increased oil recovery.

Human bone morphogenetic protein-2 (hBMP-2) characterization by physical\u2013chemical, immunological and biological assays

Commercially available preparations of methionyl-human BMP-2 and CHO-derived hBMP-2, which belongs to the transforming growth factor β (TGF-β) superfamily, were used for a complete characterization. This protein is an extremely efficient osteoinductor that plays an important role during bone regeneration and embryonic development. Characterization was carried out via SDS-PAGE and Western blotting, followed by reversed-phase HPLC, size-exclusion HPLC and MALDI-TOF-MS. The classical in vitro bioassay, based on the induction of alkaline phosphatase activity in C2C12 cells, confirmed that hBMP-2 biological activity is mostly related to the dimeric form, being ~ 4-fold higher for the CHO-derived glycosylated form when compared with the E. coli counterpart. The E. coli-derived met-hBMP-2 has shown, by MALDI-TOF-MS, a large presence of the bioactive dimer. A more complex molecular mass (MM) distribution was found for the CHO-derived product, whose exact MM has never been reported because of its variable glycosylation. A method based on RP-HPLC was set up, allowing a quantitative and qualitative hBMP-2 determination even directly on ongoing culture media. Considering that hBMP-2 is highly unstable, presenting moreover an extremely high aggregate value, we believe that these data pave the way to a necessary characterization of this important factor when synthesized by DNA recombinant techniques in different types of hosts.

Weighing synthetic polymers of ultra-high molar mass and polymeric nanomaterials: What can we learn from charge detection mass spectrometry?

Advances in soft ionization techniques for mass spectrometry (MS) of polymeric materials make it possible to determine the masses of intact molecular ions exceeding megadaltons. Interfacing MS with separation and fragmentation methods has additionally led to impressive advances in the ability to structurally characterize polymers. Even if the gap to the megadalton range has been bridged by MS for polymers standards, the MS-based analysis for more complex polymeric materials is still challenging. Charge detection mass spectrometry (CDMS) is a single-molecule method where the mass and the charge of each ion are directly determined from individual measurements. The entire molecular mass distribution of a polymer sample can be thus accurately measured. Described in this perspective paper is how molecular weight distribution as well as charge distribution can provide new insights into the structural and compositional studies of synthetic polymers and polymeric nanomaterials in the megadalton to gigadalton range of molecular weight. The recent multidimensional CDMS studies involving couplings with separation and dissociation techniques will be presented. And, finally, an outlook for the future avenues of the CDMS technique in the field of synthetic polymers of ultra-high molar mass and polymeric nanomaterials will be provided.

Деградация D,L-полилактидов в биологических средах: эксперимент и модель

The processes of changes in the surface morphology and internal structure, as well as the molecular mass distribution of amorphous D, L polylactides during their hydrolytic degradation in the presence of extra-germinal mesenchymal stem cells (MSCs) (ratschwart jelly umbilical cord) of the rat and their metabolic products have been studied. It was shown that the degradation of initially monolithic polymer samples in culture and conditioned media occurs almost identically. However, in a culture medium containing MSCs, this process is much more intense. This effect can be interpreted in terms of the influence of enzymes secreted by living cells, which diffuse from the surface into the polymer sample and accelerate its hydrolysis, entering into a catalytic reaction with the ether bonds of polylactide molecules. A mathematical model has been developed and verified that takes into account both non-catalytic and catalytic channels of hydrolysis, changes in the porosity of the polymer sample, diffusion of short-length oligomers, and adequately interprets the experimental results.

Исследования по подбору отечественной вязкостной присадки для всесезонных гидравлических масел уровня HVLP

At the present time, imported viscosity additives purchased abroad are used to produce premium multi-grade hydraulic oils in Russia. The high technology production such oils is entirely dependent on the import of these additives. At the JSC "MidVolgaNIINP" conducted research on the development and selection of domestic viscosity additives is not inferior to foreign analogues in the composition of hydraulic oils of the HVLP. For select the domestic viscous additive of optimal quality were studied three laboratory samples of polyalkyl methacrylate additives in physicochemical and operational properties in base oil. The results obtained were selected a domestic viscosity additive with a narrow molecular-mass distribution (2.19 Р) and a minimal weighted average molecular weight (34983 Da) that allows hydraulic oils to meet the requirements DIN 51524-3 and OEM. Studies had found that the quality of thickened oils is affected by the content viscous additive. The optimal contents of domestic additives for obtaining oils of viscosity levels ISO VG 32 and ISO VG 46 have been determined. The results are used in further research on the development of multi-grade hydraulic oils HVLP.

SULFATED DERIVATIVES OF ARABINOGALACTAN AND THEIR ANTICOAGULANT ACTIVITY

The IR spectra and molecular mass distribution of arabinogalactan sulfates in the form of sodium and ammonium salts, obtained using various sulfating reagents, were compared.
 According to the obtained data, the sulfated derivatives of arabinogalactan differ from each other by the nature of the hydrogen bonds and the molecular weight distribution.
 Using coagulological tests at the activation of coagulation of platelet-poor human plasma, in vitro study of the anticoagulant properties of arabinogalactan sulfated derivatives in various salt forms differing in methods of preparation, degree of sulfation and molecular weight was conducted.
 It was established that the sample in the form of arabinogalactan sodium salt (SAG 1) with a sulfur content of 13.2 wt.% аnd a polydispersity degree of 1.52 showed 2 times more anticoagulant activity than the sample in the form of ammonium salt of arabinogalactan (SAG 2) with the sulfur content of 6.6 wt.% and the degree of polydispersity of 1.30.
 Antithrombin (aIIa) activity of samples obtained by sulfation with pyridine and sulfuric anhydride complex (SAG 1) and sulfamic acid complex (SAG 2) was, respectively, 23.42±1.86 and 10.20±1.50 U/mg; the anti-factor Xa activity of SAG 1 and SAG 2 was 2.13±0.42 and 0.37±0.08 U/mg; and the ratio aIIa/aXa for SAG1 and SAG 2 was 11 and 28, respectively.
 The less activity of antifactor Xa(aXA) of SAG as compared to unfractionated heparin (UFG) and higher rations of activities aIIa/aXa may contribute the less provocation of bleeding by SAG samples in the comparition with UFG.

Identification of hydrocarbon compositions of diesel fractions and assessment of their effect on fuel operational characteristics

Using the chromatography-mass spectrometric method of analysis the group hydrocarbon compositions of straight-run and hydro-dewaxed diesel fractions have been determined. The effects of hydrocarbons on the physicochemical and operational properties of the fractions were analyzed and compared with the requirements of the standard for winter diesel fuels. The molecular-mass distribution of normal paraffin hydrocarbons was considered in detail, as well as their relationship with the low-temperature properties of the fractions. The aromatic compounds were analyzed in the two-dimensional chromatography method. It was found that naphthalene hydrocarbons predominated in the straight-run diesel fraction, and benzene and indan derivatives dominated in the hydro-dewaxed fraction. It was proved by chromatographic analysis. For the straight-run and hydro-dewaxed diesel fractions optimal concentrations of a cetane-raising additive have been determined, which enable to achieve the requirements of standards for diesel fuels.

Термическая переработка древесных отходов

Describes the processes of thermal conversion of soft– and hardwood waste to obtain gaseous, liquid and solid products. During the initial stage of the work, the thermogravimetric study of initial samples of birch and pine sawdust was performed in the temperature range from 35 to 1000 °C. On the basis of the thermal analysis data obtained, a method of pyrolysis process of wood waste in the temperature range of 400–500 °C in an inert environment was developed. As a result of experiments on pyrolysis of wood waste, the dependence of the conversion of selected samples into final products, the properties of the resulting gaseous and solid carbon-containing products depending on the conditions of the process, the size of the fraction and the type of wood were obtained. It was found that the optimal temperature of the pyrolysis process in the studied range of system parameters is 450 °C, and the particle size of wood waste is 1–2 mm. Data on the molecular mass distribution of volatile pyrolysis products and kinetic parameters of the pyrolysis process were obtained. The activation energies of the pyrolysis process for pine and birch sawdust samples were 119.3 and 128.2, respectively. The specific surface area of the initial samples of birch and pine wood waste was 9.3 and 8.5 m2/g, respectively. The specific surface area of coal pyrolysis residues for hardwoods increased by 2.4 times and for conifers by 2.1 times, respectively, and assumed values of 22.3 and 17.9 m2/g. Therefore, the coal residues of pyrolysis of wood waste can potentially be used as raw materials for the production of activated carbons and carbon sorbents of various applications.

Experimental Testing of a Size-Exclusion Chromatography Method Used for Evaluation of Molecular Parameters of Equine Anti-Ebola Immunoglobulin

Haemorrhagic fever caused by the Ebola virus is a highly hazardous infectious disease with a mortality rate of 50– 90 %. Heterologous immunoglobulins with a high virus-neutralizing titer are an important element of the WHO-endorsed set of measures for emergency prevention and treatment of the disease. Specific activity of these products is largely determined by their fractional composition, and, in particular, by molecular mass distribution (MMD). The size-exclusion-high-performance liquid chromatography (SEC-HPLC) has traditionally been used for determination of the MMD of the target protein in human immunoglobulin-based products. The use of this method for evaluation of molecular parameters of heterologous immunoglobulin requires confirmation of its specificity, accuracy and precision, and establishment of the chromatographic system suitability criteria in the context of a new test object.The aimof the study was to test the applicability of the SEC-HPLC method to the assessment of molecular parameters of anti-Ebola immunoglobulin derived from horse serum.Materials and methods: three batches of purified equine anti-Ebola immunoglobulin were used in the study. Normal equine and human immunoglobulins of the IgG isotype were used as reference standards. The HPLC test procedures described in the European Pharmacopoeia 9.6 and State Pharmacopoeia of the Russian Federation, 14th ed., were used for determination of monomers and other immunoglobulin fractions. An Agilent 1260 Infinity (Agilent, USA) HPLC system with a diode array detector and an Agilent Bio SEC-3 HPLC column were used for quality evaluation of the tested products.Results: the resolution factor between IgG monomer and dimer peaks (1.69 and 2.10), and the chromatographic column efficiency (>2000) make it possible to use the SEC-HPLC system for evaluation of molecular parameters of heterologous immunoglobulin. The study demonstrated reproducibility of the test procedure.Conclusions: the study confirmed the applicability of the SEC-HPLC procedure for evaluation of molecular parameters of anti-Ebola immunoglobulin derived from horse serum. It demonstrated the compliance of the purified immunoglobulin to the national and international quality requirements in terms of «Molecular parameters».

CO Multi-line Imaging of Nearby Galaxies (COMING). IV. Overview of the project

Abstract Observations of the molecular gas in galaxies are vital to understand the evolution and star-forming histories of galaxies. However, galaxies with molecular gas maps of their whole discs at sufficient resolution to distinguish galactic structures are severely lacking. Millimeter-wavelength studies at a high angular resolution across multiple lines and transitions are particularly needed, severely limiting our ability to infer the universal properties of molecular gas in galaxies. Hence, we conducted a legacy project with the 45 m telescope of the Nobeyama Radio Observatory, called the CO Multi-line Imaging of Nearby Galaxies (COMING), which simultaneously observed 147 galaxies with high far-infrared (FIR) flux in 12CO, 13CO, and C18O J = 1–0 lines. The total molecular gas mass was derived using the standard CO–to–H2 conversion factor and found to be positively correlated with the total stellar mass derived from the WISE 3.4 μm band data. The fraction of the total molecular gas mass to the total stellar mass in galaxies does not depend on their Hubble types nor the existence of a galactic bar, although when galaxies in individual morphological types are investigated separately, the fraction seems to decrease with the total stellar mass in early-type galaxies and vice versa in late-type galaxies. No differences in the distribution of the total molecular gas mass, stellar mass, or the total molecular gas to stellar mass ratio was observed between barred and non-barred galaxies, which is likely the result of our sample selection criteria, in that we prioritized observing FIR bright (and thus molecular gas-rich) galaxies.

Effect of dextran and enzymatically decomposed dextran on the sucrose crystal shape

The effect of dextran’s molecular mass distribution on the sucrose crystal shape was key to this study. Therefore, sucrose crystals were produced by evaporating crystallization experiments using synthetic thick juices in the form of pure sugar syrups containing high (T2000) and low (T40) molecular mass dextran fractions as well as enzymatically decomposed dextran. The combined analysis of molecular mass distributions by size exclusion chromatography and sucrose crystal shapes by static image analysis were used to identify the least harmful reaction products resulting from the enzymatic decomposition of dextran. The combined evaluation of two shape parameters, circularity and width-to-length ratio, has shown that three different shape modifications can be related to the presence of dextran, namely cube-shaped crystals, elongated needle-shaped crystals and agglomerates. In the main, the data indicated that high T2000 contents and generally all T40 dextran contents led to an increased occurrence of agglomerated and occasionally elongated crystals. The latter was especially found for high T2000 dextran contents. In contrast, low T2000 dextran contents predominantly increased the amount of cube-like crystals. The enzymatic decomposition of dextran resulted in a gradual reduction of the molecular mass. It was shown that an insufficient decomposition to broadly distributed low molecular mass dextran fragments, which are realistic to assume for technical cane and beet juices, still dramatically affected the sucrose crystal shape. Once dextran was decomposed to molecules with molecular masses of less than 5 kDa, no dextran-related effects on the sucrose crystal shape were found.

Comparative Study of Changes in the Composition of Organic Matter of Rocks from Different Sampling-Depth Intervals of Domanik and Domankoid Deposits of the Romashkino Oilfield

This paper presents the results of a comparative study of rock samples from depth intervals of 1705–1728 m of Semilukian–Mendymian (domanik) deposits of the Berezovskaya area and 1379–1394 m of carbonate (domanikoid) deposits of the Dankovian–Lebedyanian horizon of the Zelenogorskaya area of the Romashkino oilfield. It has been shown that rocks with different mineral compositions differ in the content and composition of organic matter (OM), including kerogen, and its resistance to thermal impacts. The yield of extracts from the rocks and the differences in their group, structural-group, and hydrocarbon-group compositions have been determined. According to the molecular-mass distribution of normal and isoprenoid alkanes, the extracts from the rocks are oils of types A1 and A2. Peculiarities in the distribution of higher biomarkers have been revealed, indicating that the hydrocarbons of the examined samples of domanik and domanikoid rocks are genetically uniform in nature, but differ in the geochemical environment of the transformation of the original OM and, possibly, in the effect of migration processes.

Kinetics of Radical Chain Polymerization: 2. Linear Waves of Macroradical Growth

The chain growth in radical chain polymerization is associated with the wave of transformation of primary radicals into macroradicals. The change in chain length n and molecular mass distribution R(t, n) with time t corresponds to the movement of a wave packet with velocity dn/dt and width ∆(n), both dependent on monomer concentration M(t). The formation of macroradicals in the absence of chain transfer when the rate constant of chain growth K(n) depends on n has been considered, and it has been shown that the packet is described by the Poisson distribution law with the event probability depending on K(n) and t. As K(n) decreases, R(t,n) narrows and its maximum shifts to the region of the minimum of K(n). Relations of K(n), M(t), and R(t, n) to dn/dt and ∆(n) have been found.

Synthesis of Polyester-graft-Polyoxazolines on the Basis of Macroinitiators of Sulfonyl Chloride Type

Comb-shaped thermosensitive polymers have been synthesized on macroinitiators of sulfochloride type via cationic polymerization of 2-ethyl-2-oxazoline. It has been proved that, on sulfochloride macroinitiators, the polymerization proceeds in the “living” chain mode and allows one to obtain polymers with a narrow molecular mass distribution, in particular, without the intermediate isolation of the macroinitiator.