scholarly journals Mercury(II)-Catalyzed Cleavage, Isomerization and Depurination of RNA and DNA Model Compounds and Desulfurization of Their Phosphoromonothioate Analogs

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 219
Author(s):  
Lange Yakubu Saleh ◽  
Mikko Ora ◽  
Tuomas Lönnberg
Keyword(s):  
Metal Ion ◽  
Model Compound ◽  
Model Compounds ◽  
Cleavage Rate ◽  
Artificial Nucleases ◽  
Order Of Magnitude ◽  
Ph Range ◽  
Rna And Dna

The potential of Hg(II), a metal ion so-far overlooked in the development of artificial nucleases, to cleave RNA and DNA has been assessed. Accordingly, Hg(II)-promoted cleavage and isomerization of the RNA model compound adenylyl-3′,5′-(2′,3′-O-methyleneadenosine) and depurination of 2′-deoxyadenosine were followed by HPLC as a function of pH (5.0–6.0) and the desulfurization of both diastereomers of the phosphoromonothioate analog of adenylyl-3′,5′-(2′,3′-O-methyleneadenosine) at a single pH (6.9). At 5 mM [Hg(II)], cleavage of the RNA model compound was accelerated by two orders of magnitude at the low and by one order of magnitude at the high end of the pH range. Between 0 and 5 mM [Hg(II)], the cleavage rate showed a sigmoidal dependence on [Hg(II)], suggesting the participation of more than one Hg(II) in the reaction. Isomerization and depurination were also facilitated by Hg(II), but much more modestly than cleavage, less than 2-fold over the entire pH range studied. Phosphoromonothioate desulfurization was by far the most susceptible reaction to Hg(II) catalysis, being accelerated by more than four orders of magnitude.

Efficient Preconcentration of Cu2+, Zn2+ and Fe3+ with an Agarose-Schiff Base Sorbent

2007 ◽  
Vol 72 (7) ◽  
pp. 908-916 ◽  
Author(s):  
Payman Hashemi ◽  
Hatam Hassanvand ◽  
Hossain Naeimi
Keyword(s):  
Schiff Base ◽  
Metal Ions ◽  
Metal Ion ◽  
Good Accuracy ◽  
Kinetic Studies ◽  
Sample Volume ◽  
Effects Of Ph ◽  
Glass Column ◽  
High Concentrations ◽  
Ph Range

Sorption and preconcentration of Cu2+, Zn2+ and Fe3+ on a salen-type Schiff base, 2,2'- [ethane-1,2-diylbis(nitrilomethylidyne)]bis(2-methylphenol), chemically immobilized on a highly crosslinked agarose support, were studied. Kinetic studies showed higher sorption rates of Cu2+ and Fe3+ in comparison with Zn2+. Half-times (t1/2) of 31, 106 and 58 s were obtained for sorption of Cu2+, Zn2+ and Fe3+ by the sorbent, respectively. Effects of pH, eluent concentration and volume, ionic strength, buffer concentration, sample volume and interferences on the recovery of the metal ions were investigated. A 5-ml portion of 0.4 M HCl solution was sufficient for quantitative elution of the metal ions from 0.5 ml of the sorbent packed in a 6.5 mm i.d. glass column. Quantitative recoveries were obtained in a pH range 5.5-6.5 for all the analytes. The volumes to be concentrated exceeding 500 ml, ionic strengths as high as 0.5 mol l-1, and acetate buffer concentrations up to 0.3 mol l-1 for Zn2+ and 0.4 mol l-1 for Cu2+ and Fe3+ did not have any significant effect on the recoveries. The system tolerated relatively high concentrations of diverse ions. Preconcentration factors up to 100 and detection limits of 0.31, 0.16 and 1.73 μg l-1 were obtained for Cu2+, Zn2+ and Fe3+, respectively, for their determination by a flame AAS instrument. The method was successfully applied to the metal ion determinations in several river water samples with good accuracy.

scholarly journals Donor Atom Preference of Organoruthenium and Organorhodium Cations on the Interaction with Novel Ambidentate (N,N) and (O,O) Chelating Ligands in Aqueous Solution

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3586
Author(s):  
Sándor Nagy ◽  
András Ozsváth ◽  
Attila Cs. Bényei ◽  
Etelka Farkas ◽  
Péter Buglyó
Keyword(s):  
Aqueous Solution ◽  
Metal Ion ◽  
Platinum Group Metal ◽  
Molecular Structures ◽  
Chelating Ligands ◽  
Metal Ion Binding ◽  
Biologically Relevant ◽  
X Ray Crystallography ◽  
Ligand Ratio ◽  
Ph Range

Two novel, pyridinone-based chelating ligands containing separated (O,O) and (Namino,Nhet) chelating sets (Namino = secondary amine; Nhet = pyrrole N for H(L3) (1-(3-(((1H-pyrrole-2-yl)methyl)amino)propyl)-3-hydroxy-2-methylpyridin-4(1H)-one) or pyridine N for H(L5) (3-hydroxy-2-methyl-1-(3-((pyridin-2-ylmethyl)amino)propyl)pyridin-4(1H)-one)) were synthesized via reduction of the appropriate imines. Their proton dissociation processes were explored, and the molecular structures of two synthons were assessed by X-ray crystallography. These ambidentate chelating ligands are intended to develop Co(III)/PGM (PGM = platinum group metal) heterobimetallic multitargeted complexes with anticancer potential. To explore their metal ion binding ability, the interaction with Pd(II), [(η6-p-cym)Ru]2+ and [(η5-Cp*)Rh]2+ (p-cym = 1-methyl-4-isopropylbenzene, Cp* = pentamethyl-cyclopentadienyl anion) cations was studied in aqueous solution with the combined use of pH-potentiometry, NMR and HR ESI-MS. In general, organorhodium was found to form more labile complexes over ruthenium, while complexation of the (N,N) chelating set was slower than the processes of the pyridinone unit with (O,O) coordination. Formation of the organoruthenium complexes starts at lower pH (higher thermodynamic stabilities of the corresponding complexes) than for [(η5-Cp*)Rh]2+ but, due to the higher affinity of [η6-p-cym)Ru]2+ towards hydrolysis, the complexed ligands are capable of competing with hydroxide ion in a lesser extent than for the rhodium systems. As a result, under biologically relevant conditions, the rhodium binding effectivity of the ligands becomes comparable or even slightly higher than their effectivity towards ruthenium. Our results indicate that H(L3) is a less efficient (N,N) chelator for these metal ions than H(L5). Similarly, due to the relative effectivity of the (O,O) and (N,N) chelates at a 1:1 metal-ion-to-ligand ratio, H(L5) coordinates in a (N,N) manner to both cations in the whole pH range studied while, for H(L3), the complexation starts with (O,O) coordination. At a 2:1 metal-ion-to-ligand ratio, H(L3) cannot hinder the intensive hydrolysis of the second metal ion, although a small amount of 2:1 complex with [(η5-Cp*)Rh]2+ can also be detected.

Copper(II) and zinc(II) dinuclear enzymes model compounds: The nature of the metal ion in the biological function

2017 ◽  
Vol 1150 ◽  
pp. 316-328 ◽  
Author(s):  
L.G. Ferraresso ◽  
E.G.R. de Arruda ◽  
T.P.L. de Moraes ◽  
R.B. Fazzi ◽  
A.M. Da Costa Ferreira ◽  
...  
Keyword(s):  
Metal Ion ◽  
Biological Function ◽  
Model Compounds

Halogenation of Butyl Rubber—A Model Compound Approach

1984 ◽  
Vol 57 (2) ◽  
pp. 275-283 ◽  
Author(s):  
R. Vukov
Keyword(s):  
Model Compound ◽  
Product Distribution ◽  
Butyl Rubber ◽  
Methyl Groups ◽  
Reaction Site ◽  
Model Compounds ◽  
Reaction Conditions ◽  
Basic Study ◽  
Rubber Model ◽  
Trisubstituted Alkenes

Abstract The study of the halogenation behavior of butyl rubber model compounds has brought about a better understanding of the behavior of these systems. It has been established that the presence of methyl groups, in a position B to the reaction site in the butyl rubber model compound, profoundly influences the course of halogenation. Due to the steric hindrance imposed by these groups, both the products of chlorination and bromination deviate from patterns typical of other trisubstituted alkenes. In the case of chlorination, this deviation is demonstrated by the absence of addition products of chlorine across the double bond. In the case of bromination reactions, the change in product distribution is even more dramatic. Thus, substitution products normally not observed in bromination reactions of other trisubstituted alkenes become predominant products found in yields of between 70–90% depending on the precise reaction conditions. The behavior of the butyl model compound appears to be entirely consistent with the behavior of butyl rubber itself; the model compound approach is therefore a valuable tool for use in the basic study of this type of system.

Kinetics and Mechanisms for the Isomerization of Internucleosidic 3'-O-P-CH2-5' and 3'-O-P-CH(OH)-5' Linkages to Their 2',5'-Counterparts

2006 ◽  
Vol 71 (6) ◽  
pp. 859-870 ◽  
Author(s):  
Tuomas Lönnberg ◽  
Šárka Králíková ◽  
Ivan Rosenberg ◽  
Harri Lönnberg
Keyword(s):  
Hydrogen Bond ◽  
Hydroxy Group ◽  
Phosphorus Atom ◽  
Hydrolytic Stability ◽  
Model Compounds ◽  
Hydroxide Ion ◽  
Wide Ph Range ◽  
Acid Catalyzed ◽  
Ph Range

Isomerization of internucleosidic 3'-O-P-CH2-5' and 3'-O-P-CH(OH)-5' phosphonate linkages to their 2',5'-counterparts has been studied over a wide pH-range. The model compounds employed are phosphonate analogs of adenylyl-(3',5')-adenosine and adenylyl-(2',5')-adenosine having either adenosine ((R,S)-1, (R,S)-2) or 5'-deoxyadenosine (3, 4) bonded to the phosphorus atom through the C5'-atom. For comparative purposes, the hydrolytic stability of C5'-hydroxyphosphonate analogs derived from 2'-deoxyadenosine ((R,S)-5) has also been studied. In addition to the expected acid-catalyzed (pH < 3) and pH-independent reactions (pH 3-9), the diastereomeric C5'-hydroxyphosphonate analogs ((R,S)-1, (R,S)-2), but not their deoxy counterparts (3, 4), have been observed to undergo a hydroxide-ion-catalyzed isomerization around pH 11 (90 °C). Evidently a hydrogen bond between the dianionic phosphorane and the C5'-hydroxy group stabilize the phosphorane to such an extent that isomerization via kinetically invisible protonation to monoanion becomes possible. The mechanisms of the isomerization reactions taking place under various conditions are discussed.

scholarly journals Characterization of a New Intracellular Alginate Lyase with Metal Ions-Tolerant and pH-Stable Properties

Marine Drugs ◽  
2020 ◽  
Vol 18 (8) ◽  
pp. 416
Author(s):  
Yan Ma ◽  
Jie Li ◽  
Xin-Yue Zhang ◽  
Hao-Dong Ni ◽  
Feng-Biao Wang ◽  
...  
Keyword(s):  
Metal Ion ◽  
Brown Seaweed ◽  
Alginate Lyase ◽  
Industrial Applications ◽  
Alginate Oligosaccharides ◽  
Potential Applications ◽  
Pharmaceutical Industries ◽  
Ph Range ◽  
Alginate Lyases

Alginate lyases play an important role in alginate oligosaccharides (AOS) preparation and brown seaweed processing. Many extracellular alginate lyases have been characterized to develop efficient degradation tools needed for industrial applications. However, few studies focusing on intracellular alginate lyases have been conducted. In this work, a novel intracellular alkaline alginate lyase Alyw202 from Vibrio sp. W2 was cloned, expressed and characterized. Secretory expression was performed in a food-grade host, Yarrowia lipolytica. Recombinant Alyw202 with a molecular weight of approximately 38.3 kDa exhibited the highest activity at 45 °C and more than 60% of the activity in a broad pH range of 3.0 to 10.0. Furthermore, Alyw202 showed remarkable metal ion-tolerance, NaCl independence and the capacity of degrading alginate into oligosaccharides of DP2-DP4. Due to the unique pH-stable and high salt-tolerant properties, Alyw202 has potential applications in the food and pharmaceutical industries.

scholarly journals Development of Functional Models for a SOD

2002 ◽  
Vol 9 (1-2) ◽  
pp. 9-18 ◽  
Author(s):  
Ali Arslantas
Keyword(s):  
Model Compound ◽  
Active Oxygen Species ◽  
Active Species ◽  
Phagocytic Cells ◽  
Model Compounds ◽  
Protective Mechanisms ◽  
Sod Activity ◽  
Functional Models ◽  
Electron Transport Chains ◽  
The Relationship

Superoxide dismutase (SOD) is the scavenger of superoxide anion (O2−) and functions as a protector of living bodies. Study of a model compound of SOD is important when searching for the relationship between functions and structures of enzymes. Furthermore, SOD model compounds have potential for therapeutic usefulness. Although many SOD: model compounds have been reported, their structures are quite different from those of the native enzyme. Cu,Zn-SOD has been proposed for clinical uses. Unfortunately, many problems such as half-lifetime and antigenicity have not been overcome even though several copper(II) complexes are known to show SOD activity. Active oxygen species such as superoxide (O2−) from various components of the cellular electron transport chains, and provided during the respiratory burst of phagocytic cells, have been implicated both in the aging process and in degenerative diseases, including arthritis and cancer. Therefore, the biological system posseses the protective mechanisms against active species.

scholarly journals Ion Exchange Properties of a Terpolymer Resin Derived from 2, 4-Dihydroxybenzaldehyde, Oxamide and Formaldehyde

2009 ◽  
Vol 6 (3) ◽  
pp. 639-650 ◽  
Author(s):  
M. V. Tarase ◽  
W. B. Gurnule ◽  
A. B. Zade
Keyword(s):  
Hydrochloric Acid ◽  
Ion Exchange ◽  
Metal Ions ◽  
Metal Ion ◽  
Polymer Sample ◽  
Equilibrium Method ◽  
Wide Ph Range ◽  
Ph Range ◽  
Exchange Properties

Terpolymer resins (2,4-DHBOF) were synthesized by the condensation of 2,4-dihydroxybenzaldehyde and oxamide with formaldehyde in the presence of hydrochloric acid as catalyst, proved to be selective chelation ion exchange terpolymer resins for certain metals. Chelation ion exchange properties of these polymers were studied for Fe+3, Cu+2, Hg+2, Cd+2, Co+2, Zn+2, Ni+2and Pb+2ions. A batch equilibrium method was employed in the study of the selectivity of the distribution of a given metal ions between the polymer sample and a solution containing the metal ion. The study was carried out over a wide pH range and in a media of various ionic strengths. The polymer showed a higher selectivity for Fe+3, Cd+2and Co+2ions than for Cu+2, Hg+2, Zn+2, Ni+2and Pb+2ions.

scholarly journals Kinetic studies on the acid hydrolysis of the methyl ketoside of unsubstituted and O-acetylated N-acetylneuraminic acid

1973 ◽  
Vol 133 (4) ◽  
pp. 623-628 ◽  
Author(s):  
A. Neuberger ◽  
Wendy A. Ratcliffe
Keyword(s):  
Sialic Acid ◽  
Acid Hydrolysis ◽  
Model Compound ◽  
Kinetic Studies ◽  
Order Rate Constant ◽  
Neuraminic Acid ◽  
Acetylneuraminic Acid ◽  
Rate Of Hydrolysis ◽  
Ph Range ◽  
Hydrolysis Of

The hydrolysis of the model compound 2-O-methyl-4,7,8,9-tetra-O-acetyl-N-acetyl-α-d-neuraminic acid and neuraminidase (Vibrio cholerae) closely resembled that of the O-acetylated sialic acid residues of rabbit Tamm–Horsfall glycoprotein. This confirmed that O-acetylation was responsible for the unusually slow rate of acid hydrolysis of O-acetylated sialic acid residues observed in rabbit Tamm–Horsfall glycoprotein and their resistance to hydrolysis by neuraminidase. The first-order rate constant of hydrolysis of 2-methyl-N-acetyl-α-d-neuraminic acid by 0.05m-H2SO4 was 56-fold greater than that of 2-O-methyl-4,7,8,9-tetra-O-acetyl-N-acetyl -α-d-neuraminic acid. Kinetic studies have shown that in the pH range 1.00–3.30, the observed rate of hydrolysis of 2-methyl-N-acetyl-α-d-neuraminic acid can be attributed to acid-catalysed hydrolysis of the negatively charged CO2− form of the methyl ketoside.

Convenient preparation of a β-O-4-type lignin model trimer via KOH-catalyzed hydroxymethylation and a new protection method

Holzforschung ◽  
2013 ◽  
Vol 67 (2) ◽  
pp. 129-136 ◽  
Author(s):  
Maarit Lahtinen ◽  
Anssi Haikarainen ◽  
Jussi Sipilä
Keyword(s):  
Model Compound ◽  
Catalytic Amount ◽  
Side Chain ◽  
Hydroxyl Groups ◽  
Chemical Behavior ◽  
Model Compounds ◽  
Protection Method ◽  
Convenient Synthesis ◽  
Lignin Model ◽  
Convenient Preparation

Abstract Lignin, as the second most abundant biopolymer on earth, is one of the targets for plant biorefinery studies. Its complex chemical behavior is frequently studied by dimeric, trimeric, etc. model compounds, preferably with a β-O-4-type structure. In the present study, a convenient synthesis of a β-O-4-type trimeric model compound possessing a free syringylic hydroxyl has been investigated. Two key modifications were in focus: (1) Protection of the aliphatic hydroxyl groups of the starting phenolic dimer prior to the SN2 displacement reaction before introducing the syringylic moiety with 2,2-dimethoxypropane. (2) The hydroxymethylation step to introduce the full side chain moiety. When this reaction was performed in dioxane/water in the presence of a catalytic amount of KOH instead of K2CO3, the formation of a side product via dehydration was markedly reduced. In addition, a convenient method for introducing an α,β-epoxide structure in acetophenone is recommended.

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