Using chromatography on different matrixes, three beta-glucosidases (120, 116, and 70 kDa) were isolated from enzymatic complexes of the mycelial fungi Aspergillus japonicus, Penicillium verruculosum, and Trichoderma reesei, respectively. The enzymes were identified by MALDI-TOF mass-spectrometry. Substrate specificity, kinetic parameters for hydrolysis of specific substrates, ability to catalyze the transglucosidation reaction, dependence of the enzymatic activity on pH and temperature, stability of the enzymes at different temperatures, adsorption ability on insoluble cellulose, and the influence of glucose on catalytic properties of the enzymes were investigated. According to the substrate specificity, the enzymes were shown to belong to two groups: i) beta-glucosidase of A. japonicus exhibiting high specific activity to the low molecular weight substrates cellobiose and pNPG (the specific activity towards cellobiose was higher than towards pNPG) and low activity towards polysaccharide substrates (beta-glucan from barley and laminarin); ii) beta-glucosidases from P. verruculosum and T. reesei exhibiting relatively high activity to polysaccharide substrates and lower activity to low molecular weight substrates (activity to cellobiose was lower than to pNPG).

Nine major cellulolytic enzymes were isolated from a culture broth of a mutant strain of the fungus Penicillium verruculosum: five endo-1, 4-beta-glucanases (EGs) having molecular masses 25, 33, 39, 52, and 70 kDa, and four cellobiohydrolases (CBHs: 50, 55, 60, and 66 kDa). Based on amino acid similarities of short sequenced fragments and peptide mass fingerprinting, the isolated enzymes were preliminary classified into different families of glycoside hydrolases: Cel5A (EG IIa, 39 kDa), Cel5B (EG IIb, 33 kDa), Cel6A (CBH II, two forms: 50 and 60 kDa), Cel7A (CBH I: 55 and 66 kDa), Cel7B (EG I: 52 and 70 kDa). The 25 kDa enzyme was identical to the previously isolated Cel12A (EG III). The family assignment was further confirmed by the studies of the substrate specificity of the purified enzymes. High-molecular-weight forms of the Cel6A, Cel7A, and Cel7B were found to possess a cellulose-binding module (CBM), while the catalytically active low-molecular-weight forms of the enzymes, as well as other cellulases, lacked the CBM. Properties of the isolated enzymes, such as substrate specificity toward different polysaccharides and synthetic glycosides, effect of pH and temperature on the enzyme activity and stability, adsorption on Avicel cellulose and kinetics of its hydrolysis, were investigated.

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Metrological traceability of the research results of the nominal properties of biological substances is currently an unsolved problem. This is primarily due to the absence of CRMs for nominal properties, the lack of requirements and practices in the field of metrology for tools that ensure the traceability of the research results of nominal properties, such as the nucleotide sequence of nucleic acids, DNA, RNA, and the color of urine, and letter codes.In the course of the research, the relevance of the development of the theory, requirements, and practice of using tools in Russian metrology to ensure the traceability of the research results of nominal properties is substantiated. Differences between the process of measurements and studies of nominal properties are given. A project of a metrological traceability chain of the research results of nominal properties to the international harmonization protocol is proposed, taking into account the fact that there are no primary standards of nominal properties, and there are no primary reference methods for measuring nominal properties. Methods for establishing the certified characteristics of reference materials of a fragment of human mitochondrial DNA and the inactivated strain «GK2020/1» of the coronavirus SARS-CoV-2, including additional characteristics of the nominal property «nucleotide sequence of nucleic acids», are presented. Thus, it has been established that the uncertainty of nominal properties can be expressed as a probability or level of confidence. In turn, reference materials of nominal properties are of high interest as a means of metrological assurance of the reliability of identification of the nominal properties of biological substances, which include the DNA nucleotide sequence (genes) of a human being. The main significance of the research is to create prerequisites for the application of the findings given in the work to create a new branch of metrology, which will be related to the creation of methods and means to ensure reliable results for determining the nominal properties of substances and materials.

The redox properties of heterogenized Rh i, Rh I!, and Rh Ill complexes with different, particularly organophosphorus, ligands were studied by cyclic voltammetry (CVA). The support is a carbon-paste electrode based on a fibrous-carbon material and activated carbon. The electrochemical reduction of ~1 tit produces Rh metal, which further catalyzes hydrogen evolution. After the reduction of water-soluble binuclcar Rh II complexes, the CVA curves exhibit peaks of electrocatalytlc hydrogen evolution and in~vcrsible Rh I ~ Rh II oxidation. The Rh It complexes with organophosphorus ligands are characterized only by the peak of Rh I -+ Rh 11 oxidation. After reduction, the Rh I complexes behave as a pseudo-reverse Rh0/Rh ! pair. The electron-donating properties of the l~and determine the reversibility of the system, The degree of structurization of the carbon matrix and the presence of phosphorus(v) atoms in it affect the electrochemical activity of the Rh II and Rll I complexes.Key words: rhodium complexes, organophosphorus ligands, fibrous-carbon support, electrochemistry.Rhodium complexes are widely used in catalysis of organic reactions, t Redox properties of rhodium compounds have been studied by electrochemical methods, mainly in solutions, using mercury, platinum, rhodium, graphite, and carbon Pyroeeram electrodes. 2-9In this work, we studied electrochemically the redox properties of Rhl Rhlt and Rhtll complexes, precursors of the hydroformylation le and eyelopropanation It,12 catalysts heterogenized on the carbon-paste electrode, t3 which is based on phosphorus-doped fibrous-carbon material (FCM). t4,15The following compounds were studied: RhCI 3 9 3H20 (i), Rh2(AeO) 4 (2), 16 Rh2(NaCO3)4 9 2-SH2G (3), 17Rh2(AeO)4[ P(OCH2)3CEt]2 (4), ts Rh2(AcO)4[P(OCH2)3CEt]2" 8P(OCH2)3CEt (5), 18 Rhacac(CO) 2 (6), t9 Rhacac(CO)[P(OCH2)3CEt] (7), 1~ Rhacac(CO)PPh 3 (8), 2e and P(OCH2)3CEt (9). 21 ExperimentalCompounds 1--9 differ sharply in solubility, and the experimental conditions should be standardized for comparison of their electrochemical behavior. For this purpose, compounds i--9 were supported on the carbon-paste electrode by impregnation with different solvents. Complexes 1--8 and phosphite 9 were supported on FCM t4.t5 or AR-3 active carbon (AC) prewashed with 10% HNO 3 and distilled water and dried at 130 ~ in a vacuum desiccator for 2 h. For the preparation of solutions of compounds 1 and 3, bidistilled water was used; for compound 2 and compounds 4--9, methanol and methylene dichloride, respectively, were used. Methanol and methylene dichloride were purified by the known methods. 22Preparatioa of the carlma-paste electrode. The starting materials, FCM and AC, were preliminarily dried at 90 *C in a vacuum.oven for 3 h and then stored in a vacuum desiccator above CaCI 2. Weighed samples of the materials thus prepared (100 nag of FCM or 300 nag of AC) were impregnated with solutions of compounds 1--9 (2 no8 in 2 mL of the corresponding solvent in the case of FCM or 6 nag in 6 mL of the solvent for AC). The suspension...

Complete transligation of (AcO)4Rh 2 with 4-ethyl-2,6,7-tdoxa-l-phosphabicyclo[2.2.2Joc-tane was conducted in the solid phase on ),-A1203. The reduction of Rh II to Rh I on y-AI203 at 130 ~ under the action of the above-mentioned bicyclic phosphite is accompanied by the oxidation of the acetate anion to the acetoxyl radical. The oxidation products were detected by IR and ESR spectroscopy. 2,6-Di-tert-butyl-4-metbylphenol was used as a "spin trap" to identify stable secondary radical cations.Key words: transligation, bicyclic phosphite, dirhodium(n) tetraacetate, ESR.Bicyclic phosphite, 4-ethyl-2,6,7-trioxa-l-phosphabicyclo[2.2.2]octane (P(OCH2)3CEt) (1), which, unlike PPh 3 H P(OPh)3, is characterized by a low steric parameter and the high electron-withdrawing properties, ! can bring about profound transligation of dirhodium tetraacetate(t0 z (AcO)4Rh 2 in organic solvents at elevated temperature to give a cationic rhodium(0 complex Rh[P(OCH2)3CEt]5 + (see Ref. 3). It is assumed that the cleavage of the metal--metal bond and the reduction of Rh II to Rh I under the action of P(OCH2)3CEt is accompanied by the oxidation of the acetate anion to the acetoxy[ radical. However, the experimental data confirming this assumption are missing. 3To clarify the peculiarities of complete transligation of (AcO)4Rh 2 with bicyclic phosphite 1, we carried out a heterophase reaction between these reagents in the absence of any background organic solvent that would prevent such a study. Results and DiscussionHeating of bicyclic phosphite 1 and (AcO)4Rh 2 (ratio P : Rh >_ 5), applied onto ~-A1203, at 130 ~ results in complete replacement of the acyl ligands in the rhodium complex. This process is accompanied by the cleavage of the metal--metal bond and the reduction of Rh I! to Rh i, as in the case for the reaction of P(OCH2)3CEt with (AcO)4Rh 2 in toluene 3 at 100 ~ which yielded a homoligand pentasubstituted complex [Rh(P(OCH2)3CEt)sIAcO (2). The product of the heterophase reaction can be easily eluted from the support with dichloromethane, and its physicochemicaI conslants are virtually identical with those of pentasubstituted rhodium(0 complex 2 obtained earlier. 3 Complete transligation of (AcO)4Rh 2 with bicyclic phosphite I can be represented by the following scheme: This assumption 3 was based only on the identification of the rhodium(0 complex, the only phosphoruscontaining reaction product, using mostly low-temperature 31p NMR spectroscopy.Here, ESR was used to check whether two different types of species, namely, paramagnetic rhodium ions and radical hydrocarbon fragments, can be generated in the (AcO)4Rh2--P(OCH2)3CEt--y-AI20 3 system and can undergo further transformations.The ESR spectra of specimens prior to (I) and aRer (II) heating exhibited no signals for the paramagnetic Rh 2+ ions (the Rh 0 atoms are also paramagnetic, whereas the Rh + and Rh 3+ ions do not contain unpaired electrons). Thus, the initial specimen I contains only binuclear Rh24+ complexes with paired electrons, which do not appear in the ESR spectr...