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.

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.

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.

Untersuchungen zur Struktur ribosomaler RNS aus Normal- und Tumorgeweben

1964 ◽  
Vol 19 (12) ◽  
pp. 1121-1126 ◽  
Author(s):  
H. Bielka ◽  
I. Junghahn ◽  
I. Schneiders
Keyword(s):  
Secondary Structure ◽  
Normal Liver ◽  
The Other ◽  
Monovalent Cations ◽  
Inverse Relation ◽  
Direct Relation ◽  
Bivalent Cations ◽  
Ribosomal Ribonucleic Acid ◽  
Ion Radius ◽  
The Stability

Ribosomal ribonucleic acid (rRNA) from rat liver has been investigated as to the stability of its secondary structure, using UV hyperchromism under heating at different ion conditions of the solvent. The Tm value is directly related to log [H®] within pH 5 -8 and at pH 7 to log µ of monovalent cations. In presence of monovalent cations (Li⊕, K⊕) an inverse relation exists between ion radius and Tm value, while the Tm is directly related to the ion radius of bivalent cations (Mg2⊕, Ba2⊕). Bivalent cations are more effective in stabilizing the secondary structure than monovalent ones of the same strength and radius.rRNA from rat hepatomas has a more stabile secondary structure. Under almost any conditions tested the Tm values are higher than those for rRNA from liver. rRNA from hepatomas differ from rRNA of normal liver in Tm depending upon solvent conditions. Within pH 5-7 the Tm values drop with decreasing [H⊕], whereas at pH 8 they raise again in contrast to the behaviour of rRNA from liver. The dependence of the Tm values on the ion strength is more pronounced for hepatoma rRNA. The differences in Tm of rRNA from hepatomas and liver (ΔTm) follow a direct linear dependence on log μ in presence of Na⊕. On the other hand, ΔTm increases in presence of Li® with decreasing ion strength. The direct relation between the ion radius of bivalent cations and Tm values is less pronounced in the case of hepatoma rRNA compared with rRNA from liver.

scholarly journals Role of pH in The Stability of Cytosine-Cytosine Mismatch and Canonical AT & GC Base Pairs Mediated With Silver Ion: A DFT Study

2021 ◽  
Author(s):  
Surjit Bhai ◽  
Bishwajit Ganguly
Keyword(s):  
Hydrogen Bonding ◽  
Nucleic Acids ◽  
Base Pair ◽  
Dna Duplexes ◽  
Base Pairs ◽  
Aim Analysis ◽  
C Complex ◽  
The Stability ◽  
Ph Range

Abstract Metallo-nucleic acids have been investigated for their applications in the field of nanodevices and genetic expansion. The cytosine-Ag+-cytosine mismatch base pair interactions and their stability in nucleic acids have attracted the attention of chemists. We report a systematic study of canonical, mismatch, Ag+ mediated system with CC, AT, and GC base pairs computationally. The stability of such mismatch base pairs is dependent on the pH range ~5 to 9 and the duplexes beyond this range are unstable. The DFT calculations performed with the model DNA duplexes comprising of such mismatch pairs reveal the stability trend while varying the pH conditions. The stability of canonical Watson-Crick ATGC base pairs was compared with the CCAT and CCGC mismatch base pairs and the calculated results at B3LYP-D3/6-31G* level of theory in the aqueous phase suggest that the base stacking and hydrogen bonding are well maintained in the former case, however, the larger perturbations in the geometry are observed with the mispair and relatively unstable. The calculated binding energy at B3LYP/6-31G* level of theory of ATGC is energetically more stable (~15 kcal/mol) than the mismatch base pairs. The Ag+ mediated mismatch base pairs i.e., C_CAT and C_CGC examined at the same level of theory suggest that the CC mismatch base pairs complexed with proper alignment to the Ag+ ion and the AT and GC bases maintained the hydrogen bonding interactions. The mismatched base pair duplex systems i.e., C_CAT and C_CGC are structurally similar to the canonical Watson-Crick base pairs and energetically stable by ~40 and ~50 kcal/mol compared to the canonical ATGC base pairs. The experimental report on the thermal transition profile in 5’-(A)10C(A)10-3’ and 5’ (T)10C(T)10-3’ duplexes showed remarkable stability and corroborate the calculated results.[1] The stability of Ag+ mediated mismatch bases at the higher pH 9 was also examined and the nucleobases such as guanine and thymine would be deprotonated under this condition. The calculated results suggest that the CCA_T and CCG_C duplexes are largely distorted with the complexation of Ag+ with the AT and GC base pairs and would in turn denature the duplex. The AIM analysis performed at B3LYP-D3/6-31G* level of theory for all the studied Ag+ mediated complexes reveals that the Ag+ interaction with the corresponding nucleobases was electrostatic in nature. The role of pH in governing the stability of C-Ag+-C complex formation in mismatch base nucleic acids is crucial for their application of genetic expansion and nucleic acid-based nanodevices.

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.

Schiff base equilibria. II. Beryllium complexes of N-n-butylsalicylideneimine and the hydrolysis of the Be2+ ion

1965 ◽  
Vol 18 (5) ◽  
pp. 651 ◽  
Author(s):  
RW Green ◽  
PW Alexander
Keyword(s):  
Aqueous Solution ◽  
Schiff Base ◽  
Complex Formation ◽  
Distribution Coefficient ◽  
Dilute Aqueous Solution ◽  
The Stability ◽  
Ph Range ◽  
Hydrolysis Of ◽  
Beryllium Complexes ◽  
Equilibria In Aqueous Solution

The Schiff base, N-n-butylsalicylideneimine, extracts more than 99.8% beryllium into toluene from dilute aqueous solution. The distribution of beryllium has been studied in the pH range 5-13 and is discussed in terms of the several complex equilibria in aqueous solution. The stability constants of the complexes formed between beryllium and the Schiff base are log β1 11.1 and log β2 20.4, and the distribution coefficient of the bis complex is 550. Over most of the pH range, hydrolysis of the Be2+ ion competes with complex formation and provides a means of measuring the hydrolysis constants. They are for the reactions: Be(H2O)42+ ↔ 2H+ + Be(H2O)2(OH)2, log*β2 - 13.65; Be(H2O)42+ ↔ 3H+ + Be(H2O)(OH)3-, log*β3 -24.11.

scholarly journals Investigations of ternary complexes of Co(II) and Ni(II) with thiodiacetate anion and 1,10-phenanthroline or 2,2’-bipyridine in aqueous solutions

2014 ◽  
Vol 13 (1) ◽  
Author(s):  
Dariusz Wyrzykowski ◽  
Joanna Pranczk ◽  
Dagmara Jacewicz ◽  
Aleksandra Tesmar ◽  
Bogusław Pilarski ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Substitution Reactions ◽  
Experimental Conditions ◽  
Kinetic Measurements ◽  
Hydroxo Complexes ◽  
Binary Complexes ◽  
Vis Spectroscopy ◽  
Potentiometric Titration Method ◽  
The Stability ◽  
Ph Range

AbstractA potentiometric titration method (PT) and a stopped-flow kinetic technique monitored by a UV−Vis spectroscopy have been used to characterize the stability of series of Co(II)- and Ni(II)-thiodiacetato complexes, M(TDA), in the presence of 1,10-phenanthroline (phen) or 2,2’-bipyridine (bipy) in aqueous solutions. The stability constants of the binary (1:1), ternary (1:1:1) as well as the resulting hydroxo complexes were evaluated and compared to the corresponding oxydiacetate complexes. Based on the species distribution as a function of pH the relative predominance of the species in the system over a pH range was discussed. Furthermore, the kinetic measurements of the substitution reactions of the aqua ligands to phen or bipy in the coordination sphere of the binary complexes M(TDA) were performed in the 288–303 K temperature range, at a constant concentration of phen or bipy and at seven different concentrations of the binary complexes (0.2–0.5 mM). The kinetic stability of the M(TDA) complexes was discussed in relation to the experimental conditions and the kind of the auxiliary ligands (phen/bipy). Moreover, the influence of the type of primary ligand (thiodiacetate/oxydiacetate) on the substitution rate of the auxiliary ligands was also compared.

scholarly journals An Investigation into the Adsorption of Aniline from Aqueous Solution Using H-Beta Zeolites and Copper-Exchanged Beta Zeolites

2005 ◽  
Vol 23 (3) ◽  
pp. 255-266 ◽  
Author(s):  
J. O'Brien ◽  
T. Curtin ◽  
T.F. O'Dwyer
Keyword(s):  
Aqueous Solution ◽  
Adsorption Process ◽  
Zeolite Beta ◽  
Langmuir Model ◽  
Beta Zeolite ◽  
Copper Leaching ◽  
Beta Zeolites ◽  
The Stability ◽  
Ph Range ◽  
Adsorbent Materials

Zeolite beta, a large-pore zeolite, was investigated in this study with a view to examining it as a potential adsorbent for the removal of aniline from aqueous solutions. Two different metal-loaded zeolites were prepared by exchanging H-beta zeolite (SiO2/Al2O3 = 75:1) with copper. The influence of exchanged copper on the uptake level was assessed. The effect of varying the silica-to-alumina ratio of the H-beta zeolite on the aniline uptake level was also examined, using three different H-beta zeolites with ratios of 25:1, 75:1 and 150:1 as adsorbents. The sorption experiments indicated an uptake level of ca. 110–120 mg/g for each zeolite and this level was also adsorbed by the copper-modified H-beta zeolites (SiO2/Al2O3 = 75:1). In all cases, the adsorption process followed the Langmuir model for adsorption and the level of aniline adsorbed was largely unaffected by a change in temperature or the presence of extra framework copper. The stability of the exchanged copper on these zeolites was then examined by measuring the quantity of copper leached from each zeolite into solution as a function of pH. Minimum copper leaching was observed in the pH range 5–11. This provided a stable pH working range for the adsorbent materials.

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