Influence of the peculiarities of using typical chernozem of the Kursk region on the molecular weight composition of labile humus substances

polydisperse compounds. Under the influence of agricultural use, the dispersion of LHS increases, and the molecular weight composition of LHS is trans-formed towards the accumulation of fractions with lower molecular weights in their composition. As a result, the number average molecular weight of LHS decreases from 15230 amu. in LHS virgin chernozem up to 11180-12770 amu. near LHS chernozem under permanent crops and fallow. The replacement of permanent steam with a deposit does not fundamentally affect the degree of dispersion of LHS and the values of the molecular weights of the fractions. There is only a tendency towards an increase in the relative content of fractions with high molecular weights. This is reflected in the value of the average molecular mass of LHS, which increased from 11180 amu in the variant with permanent vapor to 12530 amu. LHS has deposits. Keywords: TYPICAL CHERNOZEM, GEL-CHROMATOGRAM, FRACTION, MOLECULAR MASS OF FRACTION, AVERAGE MOLECULAR MASS, LGS (LABILE HUMUS SUBSTANCES)

Synthesis of oligotetramethylene oxides with terminal amino groups as curing agents for an epoxyurethane oligomer

A method for the synthesis of oligotetramethylene oxides with terminal amino groups is presented. Its use as a hardener for urethane-containing oligomers has been demonstrated. The diamines were synthesized by a two-stage method based on oligotetramethylene oxide diol. The compounds can be used for the production of non-toxic, biocompatible and biodegradable segmented urethane-containing elastomers. The oligotetramethylene oxide diol with an average molecular mass of 1008 was chosen as a typical precursor component. Its dibromide was formed using a quasi-phosphonium reagent in various solvents. The corresponding amine was obtained by high-pressure amination. The compounds have been identified by 1H and 13C NMR spectroscopy, IR spectroscopy, and elemental analysis.

Substantiation of an approach to determination of ketoprofen macrogol 400 esters

The aim. The work is concerned with the substantiation of the approach to the identification and quantitative determination of ketoprofen macrogol 400 esters. Materials and methods. Ketoprofen, macrogol 400, ketoprofen macrogol 400 ester (KM400E), as well as model cream-gels were studied by the following methods: absorption spectrophotometry ultraviolet (UV) and visible, high-performance liquid chromatography (HPLC), gas chromatography (GC), GC / mass spectrometry, nuclear magnetic resonance (NMR) spectrometry and thermogravimetry. Results. It was found by GC and GC / mass spectrometry that the average molecular mass (Mr) of the test macrogol 400 is 383.50 and it contains oligomers with molecular masses from 150.17 to 546.65. KM400E, which is a mixture of esters of ketoprofen with macrogol oligomers, was synthesized. The formed esters were characterized by 1H NMR spectra. It was shown that the ratio of the average molecular mass of KM400E, calculated for monoesters, and the molecular mass of ketoprofen corresponds to the ratio of specific absorbances of solutions of ketoprofen and solutions of KM400E, this fact indicated the formation of monoesters. Taking into account the risk of variability of the fractional composition of macrogol 400 in different batches, it is advisable to quantify KM400E using ketoprofen reference standard (RS) and not KM400E RS. Using HPLC with diode array detection the peak of KM400E should be identified by the UV absorption spectrum with λmax≈255 nm, which is characteristic for ketoprofen, and the relative retention time (RRt) of the peak; KM400E should be quantified by the content of ketoprofen in this impurity. During storage of model cream-gels the content of KM400E impurity is significantly lower than the content of ketoprofen propylene glycol ester (mixture of isomers). Conclusions. The approach to the identification and quantitative determination of KM400E is substantiated. The analytical procedure for determination of KM400E impurity by HPLC with a diode array detection using ketoprofen RS was developed. Correctness of the procedure was proved by the results of the validation studies.

Determination of Cellulose Degree of Polymerization in Historical Papers with High Lignin Content

Determination of cellulose degree of polymerization (DP) is one of the most commonly used methods in paper degradation studies, performed either by a standardized method using viscometry (as average degree of polymerization (DPv)) or size-exclusion chromatography (SEC) (as weight average molecular mass (Mw)). Due to the insolubility of papers with high lignin content in cupriethylenediamine (CED), such as groundwood papers, viscometric determination is not possible; therefore, pretreatment is required to allow subsequent dissolution of the papers. In this study, the pretreatment of historical papers containing groundwood with sodium chlorite in acetic acid was investigated, which enables dissolution of the paper samples in CED and determination of the cellulose average degree of polymerization by viscometry (DPv). Kappa number was determined to estimate the lignin content in the papers. The suitability of SEC UV-VIS analysis for determination of Mw in papers with high lignin content had been verified before it was used as a comparative method for viscometry. Using SEC, changes in the weight average molecular mass (Mw) of cellulose tricarbanilate (CTC) derivative during delignification were evaluated. The results indicate that no significant depolymerization occurred in the selected samples under the studied delignification conditions, which was additionally confirmed with determination of monosaccharides by ion chromatography. The results of the Mw determinations by SEC and DPv by viscometry are in good correlation, justifying the use of viscometry after chlorite/acetic acid pretreatment to determine the cellulose average degree of polymerization in historical papers with high lignin content.

Nanomechanical Molecular Mass Sensing Using Suspended Microchannel Resonators

In this work we study the different phenomena taking place when a hydrostatic pressure is applied in the inner fluid of a suspended microchannel resonator. Additionally to pressure-induced stiffness terms, we have theoretically predicted and experimentally demonstrated that the pressure also induces mass effects which depend on both the applied pressure and the fluid properties. We have used these phenomena to characterize the frequency response of the device as a function of the fluid compressibility and molecular masses of different fluids ranging from liquids to gases. The proposed device in this work can measure the mass density of an unknown liquid sample with a resolution of 0.7 µg/mL and perform gas mixtures characterization by measuring its average molecular mass with a resolution of 0.01 atomic mass units.

Techniques involving UV absorption spectroscopy for estimation of structural changes in soil organic matter

<p>UV spectroscopy is extensively used for the quantitative analysis of natural macromolecules because of simplicity. As a qualitative method it is not very selective. The absorption spectra of organic macromolecules are generally broad bands without distinct peaks decreasing with the increasing wavelength making thus impossible to draw conclusions about exact chemical composition. However certain optical properties enable to obtain information about the organic matter transformation and changes in soils.</p><p>In present study soil samples from different depths were investigated by UV spectroscopic methods to measure the absorbance ratios at several wavelengths that could be related to chemical properties of the organic matter, for example the aromaticity, average molecular mass, functional groups, etc. The aim was to study the changes in structural characteristics of humic acids in soil profiles by using their UV absorbance ratios (A254/A436, A280/A350, A470/A664, A254/A354, A254/A204). The top layer of the soil was also characterized by comparing the structure of humic and fulvic acids and unfractionated dissolved organic matter. The spectra and molecular masses were additionally obtained by high performance size exclusion chromatography (HPSEC) with diode array detection.</p><p>Our results showed that there is a systematic change in the absorbance ratios at different wavelengths of humic- and fulvic acids and dissolved organic matter spectra in the soil profile that indicates to structural changes in the soil in time. The comparison of all fractions indicated that fulvic acid and unfractionated organic matter are structurally more similar to each other than to humic acid. Although the values obtained by two studied methods (UV spectroscopy and HPSEC) did not give the same values for the absorbance ratios, the correlations are mostly comparable and therefore, both methods can be used to estimate the changes of structural properties in soil.</p>

Novel Capsular Polysaccharide from Lobochlamys segnis

In recent years there has been a significant effort from food, nutraceutical, cosmeceutical, pharmaceutical, and biomedical industries to discover and develop new natural ingredients. Microalgae have been recognised as potential sources of high value chemicals, with most attention focused upon antioxidants, pigments, and specialty oils. An under-exploited group of biochemicals produced by microalgae are extracellular polymeric substances (EPS). Lobochlamys segnis (formerly called Chlamydomonas segnis) was previously reported to produce a large amount of capsular polysaccharide (CPS) closely related to hyaluronan (HA) under stress conditions. In this work, the purified CPS was characterised and shown to have an average molecular mass (Mn) of about 3.7 MDa, and displayed a highly branched random coil structure unlike the simple repeating linear HA polysaccharide. Chemical analysis showed the presence of galactose, glucuronic acid, and glucose sugars confirming that the product has a different composition to that of HA. Mixotrophic growth and stress conditions were identified and improved upon with a pH control system using acetic acid solution to induce efficient production of CPS. Extraction and purification conditions were also identified exploiting the high Mn of the product. The CPS showed thickening properties and both significant antioxidant capacity and reducing power, which could have commercial applications. This is the first report on the characterization of this novel polysaccharide with non-Newtonian properties similar to HA.

Structure and chemical composition of exopolysaccharides of frost-damaged sugar beet

In this research paper, development of a procedure of isolation of exopolysaccharides from frost-damaged beet and an analysis of structural and chemical composition of polymers isolated from sugar beet of different origin are presented. Total acid hydrolysis degradation integrated with HPAEC-ED analysis has been utilized to confirm the monomeric composition of the separated polysaccharides. The implementation of NMR spectral analysis and SEC chromatography of the structure of exopolysaccharides has been investigated. The results demonstrate that the chemical composition and structure of exopolysaccharides depend on their origin. Typical exopolysaccharides from Central European beet roots consist mainly of glucose monomers – and they have low branched structure – about 90% of α-1,6 linkage which is typical for dextran. The exopolysaccharides isolated from Swedish beet are characterized by 50–60% fructose monomers. They contain only about 65% α-1,6 linkages. Exopolysaccharides extracted from various origin beet differ in average molecular mass. The molecular distribution is not normal.

Synthesis of a New Hyperbranched Pyridylphenylene Polymer Based on an АB2 Monomer and a Pair of АB/АB2 Monomers

A hyperbranched pyridylphenylene polymer with the weight average molecular mass of 56000 Da is synthesized for the first time from an AB2 monomer bearing one diene and two internal triple bonds. The introduction of a linear AB comonomer into the reaction system leads to an increase in the yield of the polymer which has the weight average molecular mass of 21400 Da. Due to the limited degree of intramolecular cyclization, the high content of functional groups facilitates the formation of defect-free structures and provides an opportunity to modify the resulting polymers.

The Effect of Cladode Drying Techniques on the Prebiotic Potential and Molecular Characteristics of the Mucilage Extracted from Opuntia ficus-indica and Opuntia joconostle

The dry, powdered cladodes of Opuntia ficus-indica are often-used in over-the-counter (OTC) pharmaceutical formulations. Gentle drying techniques, such as lyophilization and vacuum drying are compared with convection drying for the cladodes and also compared with another species of economic importance, Opuntia joconostle. The heteropolysaccharide purified from the mucilage extracted from the dried powders were investigated in their monosaccharide composition (HPAEC-PAD, TLC), mineral and protein content, molecular dimensions (SEC) and fermentability by probiotic bacteria (Bioscreen technique) for evaluation of the prebiotic potential of the mucilage. The heteropolysaccharide is composed of galactose, arabinose, xylose, galacturonic acid and rhamnose. O. ficus-indica includes an additional 13% of glucose coming from an α-glucan. The content of Ca (0.3%) and Mg (0.4%) is relatively low in both species; the content of protein adds up to 1.5% in O. ficus-indica but is significantly lower in O. joconostle with 0.8%. The average molecular mass Mw of the extracted mucilage ranges from 3.7 to 4.7 × 105 g∙mol−1 for both species; only the mucilage from long-time convection drying (C2) delivers a lower average Mw of 2.6 × 105 g∙mol−1, due to partial breakdown of the mucilage matrix. All tested probiotic strains utilized the mucilage to some extent; C2 being the most active, and thus confirms the prebiotic potential of cladode’s powder and its derived products. In general, the molecular dimensions and prebiotic potential are not extremely sensitive to the drying treatment, yet temperature and drying time can modify the cladode’s powder to a profile with better prebiotic characteristics.