scholarly journals THEORETICAL AND EXPERIMENTAL STUDY OF MACROMOLECULAR NANOSTRUCTURES BASED ON HEPARIN AND LANTHANOIDS

2021 ◽  
pp. 513-521
Author(s):  
Михаил Игоревич Скобин ◽  
Мариана Александровна Феофанова ◽  
Тимофей Владимирович Крюков
Keyword(s):  
Experimental Study ◽  
Ionic Strength ◽  
Physicochemical Properties ◽  
Quantum Chemical ◽  
Good Choice ◽  
Chemical Modeling ◽  
Chemical Equilibria ◽  
Basic Set ◽  
The Stability ◽  
Ph Range

Исследование синтетических и природных материалов пригодных для создания наноносителей и их модификация обеспечит прорыв в лечении многих заболеваний. Хорошим выбором для создания наноносителей являются гликозаминогликаны (гепарин и его производные), благодаря их уникальным биологическим и физико-химическим особенностям. Формирование композиций было исследовано методом pH -метрического титрования при 37 °С на фоне 0,15 М NaCl. С использованием программы NewDALSFEK определены значимые формы и химические равновесия. В диапазоне pH от 2,7 до 5 образуется комплекс вида {[LnHep]}, где Hep - мономерное звено макромолекулы гепарина. Получены данные об устойчивости нанокомпозиций: lgβ[PrHep] = 4,27 ± 0,04, lgβ[SmHep] = 4,28 ± 0,03 , lgβ[EuHep] = 4,28 ± 0,03. Методом M06-HF в сочетании с базисным набором CSDZ+* выполнено квантово-химическое моделирование комплексов. Study of synthetic and natural materials suitable for the creation of nanocarriers and their modification will provide a breakthrough in the treatment of many diseases. Glycosaminoglycans (heparin and its derivatives) are a good choice for creating nanocarriers due to their unique biological and physicochemical properties. The complexation of Pr (III), Sm (III), Eu (III) with heparin anions was studied by potentiometric titration at 37 °C and an ionic strength of 0,15 M NaCl. Significant forms and chemical equilibria were determined using the NewDALSFEK program. In the pH range from 2,7 to 5 , a complex of the type {[LnHep]} is formed, where Hep is a monomeric unit of the heparin macromolecule. Data on the stability of nanocompositions were obtained: lgβ[PrHep] = 4,27 ±0,04, lgβ[SmHep] = 4,28±0,03, lgβ[EuHep] = 4,28±0,03. The M06-HF method in combination with the CSDZ+* basic set was used to perform quantum chemical modeling of the complexes.

Redox properties of [Fe2(SC6H5)2(NO)4]: an experimental study and quantum chemical modeling

2012 ◽  
Vol 61 (10) ◽  
pp. 1860-1866 ◽  
Author(s):  
N. A. Sanina ◽  
A. G. Krivenko ◽  
R. A. Manzhos ◽  
N. S. Emel’yanova ◽  
K. V. Bozhenko ◽  
...  
Keyword(s):  
Experimental Study ◽  
Quantum Chemical ◽  
Redox Properties ◽  
Quantum Chemical Modeling ◽  
Chemical Modeling

Beryllium-chrome-azurol-S complexes

1968 ◽  
Vol 21 (3) ◽  
pp. 603 ◽  
Author(s):  
WG Baldwin ◽  
DR Stranks
Keyword(s):  
Ionic Strength ◽  
Complex Formation ◽  
Ion Exchange ◽  
Stability Constant ◽  
Anionic Complex ◽  
Acidity Constants ◽  
Chrome Azurol S ◽  
Major Species ◽  
The Stability ◽  
Ph Range

Complex formation between the aquated beryllium cation and the tetrabasic dyestuff chrome-azurol-S (H4CAS) has been studied by spectrophotometric, potentiometric, electrophoretic, and ion-exchange techniques. At least two complexes are shown to exist within the pH range 3-6. The major species is the anionic complex BeHCAS- for which log β11, = 4.66 � 0.08 at 25� and at ionic strength 0.lM (NaClO4) Coordination of beryllium is considered to occur at the quinonoid-,). carboxylato site in the HCAS8- ligand. The stability constant for the dinuclear species Be2CASO is shown to be log β21 = 15.8 � 0.1 under the same medium conditions. The dinuclear complex interferes with spectrophotometric measurements at beryllium concentrations exceeding 2.5 x 10-4. The acidity constants of H4CAS were determined at 25� and at an ionic strength 0.IM (NaClO,) as pK2a = 2.25 � 0.10,pK3a, = 4.88 � 0.05, pK4, = 11.75 � 0.05, whilst pK1a = -1.2 � 0.4.

scholarly journals Quantum-chemical modeling of structure and properties of nitrogen derivatives of phloroglucinol

2019 ◽  
Vol 57 (3) ◽  
pp. 51-57
Author(s):  
Mikhail A. Ryabov ◽  
◽  
Thi Ngok Anh Vu ◽  
Olga V. Kovalchukova ◽  
Dmitry S. Gusarov ◽  
...  
Keyword(s):  
Electronic Absorption ◽  
Quantum Chemical ◽  
Electronic Absorption Spectra ◽  
Bathochromic Shift ◽  
Dft Method ◽  
Chemical Modeling ◽  
Tautomeric Forms ◽  
The Stability ◽  
Intramolecular Hydrogen ◽  
L1 And L2

The DFT/B3LYP quantum-chemical method has been used to simulate the structure of 2-((2-hydroxyphenyl) diazonyl) benzene-1,3,5-triol (L1) and 2-((2-hydroxy-4-nitrophenyl) diazonyl) benzene-1,3,5-triol (L2) molecules. The spatial and electronic structure of molecules in various tautomeric forms was determined. It was shown that the stability of these compounds is primarily due to the presence of strong intramolecular hydrogen bonds (IHB), which form six-membered cycles, and the isomerism of the molecule, which assume the formation of IHB. The structures where IHB form five-membered cycles, are less stable. In general, for the L1 and L2 molecules, azo-tautomers were found to be 4 and 3 kJ/mol more stable than the hydrazo-tautomers, respectively. Such a small difference in energy of molecules for the gas phase did not allow us to conclude about the form of existence of molecules in solutions or in the crystalline state. To assess the possibility of transition between tautomers, we used the DFT method to calculate the transition states (TS) between the azo and hydrazo tautomers of the L1 and L2 molecules. The barrier of the transition from the azo form to the hydrazo form was found to be 14 kJ/mol for the molecules L1 and L2, respectively. The interatomic distances, angles, charges on atoms, IR and electronic absorption spectra of tautomeric forms of L1 and L2 molecules were calculated. It has been established that the long-wave absorption band (LB) of the electronic absorption spectrum bathochromically shifts at transition from azo to hydrazo-tautomers by 41 nm for L1 and 40 nm for L2. The introduction of a nitro group also leads to a bathochromic shift of the LB by 22 nm at transition from azo-tautomer L1 to hydrazo-L1 L2 and by 21nm at transition from azo-L2 to hydrazo-L2.

scholarly journals Studies on the Structure of Ribosomal Ribonucleic Acid from Normal and Tumour Tissues

1967 ◽  
Vol 22 (10) ◽  
pp. 1035-1043 ◽  
Author(s):  
H. Bielka ◽  
G. Lutsch
Keyword(s):  
Ionic Strength ◽  
Nucleic Acids ◽  
Ribosomal Rna ◽  
Molecular Conformation ◽  
Monovalent Cations ◽  
Degree Of Dissociation ◽  
Bivalent Cations ◽  
The Stability ◽  
Ph Range ◽  
Ionizable Groups

The dissociation properties of ribosomal RNA from liver and hepatoma were found to be dependent upon the temperature, ionic strength and cationic valency of the solvent. On increasing the temperature the pK values of the Ν1 H— C6=O and N1= C6 — NH2 groups of nucleobases were displaced towards neutrality due to the thermal cleavage of Η-bridge linkages. Consequently, as the temperature is increased the nucleic acids bind increasingly more equivalents of acid or alkali. On forward- and back-titration hysteresis is observed in the acid pH range and the degree of hysteresis is found to decrease as the temperature is increased. Increasing the ionic strength of monovalent cations from μ=0.005 to 0.05 Na® leads to a reduced binding of equivalents of acid and alkali brought about by the displacement of pK values towards more extreme pH-values and to an increase in the stability of secondary structure.Bivalent cations exert a stronger stabilizing effect on the molecular conformation of nucleic acids than monovalent cations of equal ionic strength. The more pronounced displacement of the PK values of ionizable groups on titration from pH 7 to pH 3 may be attributed to the additional action of bivalent cations as chelate formers.Significant differences in the acid-base properties of ribosomal RNA from liver and hepatoma were observed especially at low temperatures and high ionic strength. At 5 °C and μ=0.1 NaCl less equivalents of acid and alkali are bound by hepatoma RNA than by liver RNA due to a lower degree of dissociation particularly of the N1=C6—NH2, and Ν1H — C6=0 groups.

Ionic Strength Dependence of Formation Constants, Protonation and Complexation of Phenylalanine with Dioxovanadium(V) at different temperatures

2000 ◽  
Vol 2000 (4) ◽  
pp. 186-187 ◽  
Author(s):  
Farrokh Gharib ◽  
Karim Zare ◽  
Kavosh Majlesi
Keyword(s):  
Ionic Strength ◽  
Stability Constants ◽  
Sodium Perchlorate ◽  
Type Equation ◽  
Formation Constants ◽  
Ionic Strength Dependence ◽  
Different Temperatures ◽  
Strength Dependence ◽  
The Stability ◽  
Ph Range

The protonation constants of phenylalanine and the stability constants of the complexes between dioxovanadium(V) ion and phenylalanine have been determined spectrophotometrically, in the temperature range 15–35°C and ionic strength ranging from 0.1 to 1.5 mol dm−3 sodium perchlorate as a background salt, in the pH range 1.5–10.5, with high ligand to metal ratios. The values of enthalpy and entropy changes based on these formation constants were calculated. The dependence of protonation and the stability constants on ionic strength are described by a Debye-Huckel type equation.

A simulation apparatus for the experimental study of batch reactor control methods

1986 ◽  
Vol 51 (6) ◽  
pp. 1259-1267
Author(s):  
Josef Horák ◽  
Petr Beránek
Keyword(s):  
Experimental Study ◽  
Closed Loop ◽  
Dynamic Properties ◽  
Batch Reactor ◽  
Exothermic Reaction ◽  
Electric Heating ◽  
Batch Reactors ◽  
Exchange Area ◽  
The Stability ◽  
Methods Of Control

A simulation apparatus for the experimental study of the methods of control of batch reactors is devised. In this apparatus, the production of heat by an exothermic reaction is replaced by electric heating controlled by a computer in a closed loop; the reactor is cooled with an external cooler whose dynamic properties can be varied while keeping the heat exchange area constant. The effect of the cooler geometry on its dynamic properties is investigated and the effect of the cooler inertia on the stability and safety of the on-off temperature control in the unstable pseudostationary state is examined.

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