Anatoly Yatsimirsky

Anatoly Yatsimirsky
Universidad Nacional Autónoma de México | UNAM · Department of Inorganic Chemistry

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137
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Publications

Publications (137)
Article
The binding types (H-bonding or coordinate) and stability constants for complexes of 11 mono- and di-anions with benzoxaborole (1) were determined by 1H and 11B NMR titrations in DMSO or MeCN. Compared to phenylboronic acid (PBA), 1 is a stronger Lewis acid and a poorer H-bond donor with only one B-OH group, which is expected therefore to recognize...
Article
Phenylboronic acid (PBA) forms neutral tetrahedral N,O-coordinated 6-membered cyclic complexes with stability constants reaching the values as large as 1.3×10⁴ M⁻¹ at pH 7.4 in water with amino phenolic compounds including 2-(2’-hydroxyphenyl)-1H-benzimidazole (HPBI) often used for protein probing and labeling. The crystal structures of isolated co...
Article
Aza-flavonols are compounds containing the 3-hydroxy-4(1H)-quinolone moiety, a unique scaffold with applications expanding from fluorescent probes and bioimaging to potential metal-related pharmaceutical drugs. Compositions and stability constants of metal complexes of an aza-flavonol 1-methyl-2-phenyl-3-hydroxy-4(1H)-quinolone (LH) in aqueous mice...
Article
The interaction of pinanediol with 2-fluorophenylboronic and several other substituted phenylboronic acids was studied in 40% vol. aqueous acetonitrile by 1H and 11B NMR, potentiometric and spectrophotometric titrations at variable pH. The experimental results reveal a formation of a very stable trigonal ester (Ktrig = 2×10⁴ M⁻¹) and a significantl...
Article
Two tridentate and one tetradentate new ligands containing the terminal oxime group separated from a secondary amino and pyridine groups as additional binding sites by two or three methylene groups have been prepared. Their acid-base properties, as well as the composition and stability of their complexes with Zn(II) and Cd(II) ions were determined...
Article
Hybrid materials based in mesoporous silica nanoparticles (MSN) have attracted plentiful attention due to the versatility of their chemistry, and the field of drug delivery systems (DDS) is not an exception. MSN present a desirable biocompatibility, high surface area values, and a well-studied surface reactivity for tailoring a vast diversity of ch...
Article
Sensing of pyrophosphate anion (PPi) in the presence of nucleotide triphosphates allows the real time monitoring of the polymerase chain reaction. To get a deeper understanding of the factors involved in PPi/nucleotide triphosphate discrimination, a detailed study on the performance of a dimethyltin(IV)-catecholate complex capable of both separate...
Article
We used our recently proposed Acidity-Basicity Interplay (ABI) model (Chem. Sci., 2018, 9, 4402), and the Jorgensen Secondary Interactions Hypothesis (JSIH) to rationalise the experimentally observed trends in the formation constants of doubly and triply H-bonded systems with−NH···O=C− and −NH···N− interactions. Unlike the JSIH, the ABI interpretat...
Article
Stability constants of boronate complexes with a highly efficient bioconjugation ligand salicylhydroxamic acid, its derivatives and some structurally related compounds were determined by potentiometric and spectroscopic titrations at variable pH allowing one to obtain detailed stability – pH profiles and to identify the optimum pH for complexation...
Article
Two 2,6-pyridinedicarboxamide derivatives containing arylboronic acid fragments were prepared and fully characterized including X-ray crystal diffraction analysis of a pinacol ester. These compounds are potential bifunctional receptors for sugars and anions. Acid dissociation and stability constants for complexation of both receptors with glucose a...
Article
In this work, the optical properties of N,N-bis(aminobenzyl)naphthalenediimides 2a–2d (BzNDIs) and their interaction with fluoride were studied. The results demonstrated that the amino group position in the benzyl substituent exerts an effect in the absorption and emission properties. Particularly, the N,N-bis(2-aminobenzyl)NDI 2b presented non-typ...
Article
Deprotonated zinc(II) and cadmium(II) complexes of a tridentate oxime nucleophile (1, OxH) show a very high reactivity, breaking by 2-3 orders of magnitude the previously established limiting reactivity of oximate nucleophiles in the cleavage of substituted phenyl acetates and phosphate triesters, but are unreactive with p-nitrophenyl phosphate di-...
Article
The majority of reagentless affinity sensors suffer from poor selectivity because specific binding and non-specific interactions generate responses in the same direction, commonly causing resistance increase. We report on the advanced transducer, synthesized in course of molecular imprinting, which generates conductivity increase as a result of spe...
Article
2-Phenyl-3-hydroxy-4(1H)-quinolone possessing dual fluorescence due to excited-state intramolecular proton transfer (ESIPT) forms stable complex with phenylboronic acid with blue shifted emission maximum in micellar medium of a cationic surfactant even though the compound lacks required for complexation with boronic acids cis-diol structure. No com...
Article
A new 1, 4, 5, 8-naphthalene diimide functionalized with two 3-phenylboronic acid groups (1) was prepared and employed as a selective sensor for fluoride. The proposed sensor is based on anion-π interactions between fluoride and naphthalene diimide core and the cooperative effect of boronic acid groups acting as Lewis acid anion receptors. The resu...
Article
Testing phosphodiesterase activity of Eu(III) in the presence of native cyclodextrins revealed capacity of β-cyclodextrin (β-CD) to stabilize catalytically active metal hydroxocomplexes in mildly basic solutions. Kinetics of the hydrolysis of bis(4-nitrophenyl) phosphate (BNPP) and transesterification of 2-hydroxypropyl 4-nitrophenyl phosphate (HPN...
Article
The acid–base and coordination properties of 2-phenyl-3-hydroxy-4(1H)-quinolone (1) and 1-methyl-2-phenyl-3-hydroxy-4(1H)-quinolone (2) were characterized by potentiometric, UV-Visible and fluorescence titrations in water containing 5 or 30% vol MeCN and in a micellar solution of a cationic surfactant. The first dissociation constants (pKa1) corres...
Article
We report on the novel reagentless and label-free detection principle allowing discrimination of specific binding over non-specific interactions. Unlike majority of impedimetric and conductometric (bio)sensors, which specific and unspecific signals are directed in the same way (resistance increase), making doubtful their real applications, the resp...
Article
Interactions between arylboronic acids and a series of anions as tetrabutylammonium salts in DMSO and MeCN were studied by 1H and 11B NMR and spectrophotometrically. Boronic acids act as Bronsted acid type receptors through hydrogen bonding with B(OH)2 hydroxyl groups toward Cl-, Br-, HSO4- and AcO-, but as Lewis acid type receptors toward F- and H...
Article
Full-text available
A tetraanionic [2+2] boronate ester macrocycle is self-assembled from a dicatechol 3,3,3′,3′-tetramethyl-1,1′-spirobiindane-5,5′,6,6′-tetraol and 1,4-benzenediboronic acid in the presence of 2 equivalents of NaOH in water containing 0-5 % vol. DMSO. No templating by potential guest molecules is required for the self-assembly with close to quantitat...
Article
A 20-membered dioxadiaza-calix[4]arene analog (1) was combined with a series of inorganic acids to explore the anion-inclusion properties of the corresponding ammonium dication [1-H2]2+. The neutral calix[4]arene analog 1 and six salts of the receptor in the mono- or diprotonated form, [1-H2]Cl2 (2), [1-H2]Br2 (3), [1-H2][MeOSO3]2 (4), [1-H2][NO3]2...
Article
Boronate-substituted polyanilines are able to serve as advanced affinity transducers if synthesized at their highest conductivity and remind properties (particularly, cyclic voltammograms in acidic media) of common conductive polyaniline. This presumes growing conditions, when the substituent promotes electrophilic substitution in para- position re...
Article
We report on the novel reagentless and label-free detection principle based on electroactive (conducting) polymers considering sensors for polyols, particularly, saccharides and hydroxy acids. Unlike the majority of impedimetric and conductometric (bio)sensors, which specific and unspecific signals are directed in the same way (resistance increase)...
Article
Full-text available
Dicationic N-methylated at quinolyl moieties derivatives of three isomers of N,N′-bis(quinolyl)pyridine-2,6-dicarboxamide, and respective N-methyl quinolinium benzamides as reference compounds, have been prepared and characterized by crystal structures, spectral and acid-base properties in water. First pKa values of dicarboxamides between 8.1 and 9...
Article
Zinc(ii) and cadmium(ii) complexes of a tridentate oximate ligand cleave 4-nitrophenyl acetate with rate constants surpassing by two orders of magnitude those reported as the maximum possible level for highly basic free oximate anions as a result of removal of the "solvational imbalance" of the nucleophile by metal coordination.
Article
Complexations of natural products with synthetic receptors as well as the use of natural products as host compounds are reviewed, with an emphasis on possible practical uses or on biomedical significance. Applications such as separation, sensing, enzyme monitoring, and protection of natural drugs are first outlined. We then discuss examples of comp...
Article
Stability constants of boronic acid diol esters in aqueous solution have been determined potentiometrically for a series of meta-, para-substituted phenylboronic acids and diols of variable acidity. The constants beta11-1 for reactions between neutral forms of reactants producing the anionic ester plus proton follow the Hammett equation with rho de...
Article
3-Hydroxyflavonate-diphenyltin(iv) chloride (Ph(2)Sn(Ofl)Cl) was prepared and characterized structurally by single crystal X-ray diffraction. The compound possesses high fluorescence (λ(max) 464 nm with excitation at 400 nm) in neutral aqueous solutions containing 5 mM cetyltrimethylammonium chloride and does not lose the flavonol ligand even at hi...
Article
Kinetics of transesterification of the RNA model substrate 2-hydroxypropyl 4-nitrophenyl phosphate promoted by Mg(2+) and Ca(2+), the most common biological metals acting as cofactors for nuclease enzymes and ribozymes, as well as by Co(NH(3))(6)(3+), Co(en)(3)(3+), Li(+), and Na(+) cations, often employed as mechanistic probes, was studied in 80%...
Article
Full-text available
Interactions of 2-, 3- and 4-formyl phenylboronic acids (FPBAs) with sugars, amino sugars, aminoglycosides and various poly- and monoamines have been studied by UV-vis, (1)H and (11)B NMR titrations in water at variable pH. Behavior of 2-FPBA was anomalous in several aspects. Transformation of the acid into its conjugate base was slow in NMR time s...
Chapter
Structures, recognition, and some relevant physicochemical properties of small biological molecules, as well as their applications in analysis, are described. The following classes of compounds are discussed: biological ionophores, glycopeptide antibiotics, rifamycins, bile acids and their salts, aminoglycosides, cyclic polypeptide (including thiop...
Article
Binding of alkaloids by different hosts (native and modified cyclodextrins, cucurbiturils, calixarenes, and metal complexes of porphyrin and Salphen-type ligands), as well as receptor properties of alkaloid based hosts are reviewed. With alkaloids as guests, the largest binding constants and most significant spectral changes, in particular strong f...
Article
Potentiometric titrations of alizarin complexone (ALC) in the presence of La(III), Eu(III) and Y(III) in 50% vol. DMSO reveal formation of mostly binuclear complexes with monoprotonated (LH) and completely deprotonated (L) forms of the ligand of the type M2L2H2, M2L2H and M2L2. Only for La(III) a single mononuclear complex LaLH is observed in acidi...
Article
A series of organotin(IV) compounds R3Sn(A) where R = Me or Ph and A is a chromogenic nitrophenolate ligand were prepared and studied as possible colorimetric sensors for anions (F−, Cl−, Br−, AcO−, H2PO4−). Equilibrium constants for a complete set of reactions between R3Sn(A) with A = 2-amino-4-nitrophenolate (ANP) or 4-nitrophenolate and anions (...
Article
Full-text available
Highly selective detection of pyrophosphate in the presence of inorganic phosphate, halides, acetate, ATP, other nucleotides and phosphate esters in neutral aqueous solutions is achieved by using fluorescent dimethyltin(iv)-alizarin red S complex.
Article
Two thiacalix[4]arenes in 1,3-alternate conformation functionalized by two (CH2)2NH(C=X)NHC6H4-NO2-p groups (X=S,O) as well as two related monofunctional receptors MeO(CH2)2NH(C=X)NHC6H4-NO2-p were prepared and characterized by X-ray crystal structures. The thioureido and ureido derivatives have E,Z and E,E conformations respectively both in monofu...
Article
Protonation of an aminoglycoside antibiotic kanamycin A sulfate was studied by potentiometric titrations at variable ionic strength, sulfate concentration and temperature. From these results the association constants of differently protonated forms of kanamycin A with sulfate and enthalpy changes for protonation of each amino group were determined....
Article
Full-text available
Interactions of protonated forms of kanamycin A with nucleotides and several simple phosphate anions have been studied by potentiometric and NMR titrations. The affinity of kanamycin A to anions is comparable to that observed with other aliphatic polyammonium receptors of similar charge, but it discriminates triphosphate nucleotides with different...
Article
Dicationic N-methylated at pyridyl or quinolyl moieties derivatives of three isomers of N,N'-bis(pyridyl)pyridine-2,6-dicarboxamide (o-, m-, and p-1) and of N,N'-bis(3-quinolyl)pyridine-2,6-dicarboxamide (4) strongly bind anions in MeCN (log K in the range 3.5-6.5) with pronounced selectivity for Cl(-) and also bind neutral urea and amide guests wi...
Article
Full-text available
Using 80% vol aqueous DMSO as the reaction medium for transesterification of an RNA model substrate 2-hydroxypropyl 4-nitrophenyl phosphate allows one to observe catalysis in buffer mixtures composed of highly basic components such as guanidines, amidines or alkylamines, which provide up to 10(3)-fold accelerations over the background reaction in t...
Article
Full-text available
Data from potentiometric titrations of Eu(CF(3)SO(3))(3) by Me(4)NOH in 80% v/v DMSO/water agree equally well with formation of two sets of hydroxo complexes: either Eu(2)OH(5+) and Eu(OH)(n)(3-n) (n = 1-3) or Eu(2)OH(5+), Eu(2)(OH)(2)(4+), Eu(2)(OH)(5)(+) and Eu(OH)(3). Studies using direct excitation luminescence spectroscopy and time-resolved de...
Article
The binding of seven ureas and amides to Cu(terpy)2+ in methanol has been studied by EPR, NMR and UV–Vis spectroscopy. The association constants range from 6.5M−1 for acetamide to 45.3M−1 for propyleneurea and correlate with the gas phase basicity of ligands. In methanol/water mixtures the affinity drops rapidly on increase in water content to 20vo...
Article
Full-text available
Association of amino acids and some other low molecular weight compounds with rifamycin SV in water has been studied by 1H NMR titrations. Rifamycin binds aromatic amino acids with pronounced enantioselectivity in favor of l-enantiomers and forms complexes with heterocyclic compounds but does not interact with simple benzene derivatives. Binding co...
Article
Kinetics of the cleavage of two phosphate diesters, bis(4-nitrophenyl) phosphate and 2-hydroxypropyl 4-nitrophenyl phosphate and a triester, 4-nitrophenyl diphenyl phosphate, in the presence of Mg(II), Ca(II) and Sr(II) were studied in 90% vol. DMSO at 37 degrees C. The alkaline hydrolysis of the triester was inhibited by all cations, but with both...
Article
Potentiometric titrations of La(III), Nd(III), and Eu(III) perchlorates by Me 4N(OH) in 80% vol aq DMSO revealed formation of predominantly mononuclear complexes M(OH)n(3- n) (n = 1, 2, or 3) and a single binuclear complex M2(OH)(5+). Kinetics of the cleavage of two phosphate diesters, bis (4-nitrophenyl) phosphate (BNPP) and 2-hydroxypropyl 4-nitr...
Article
Spectrophotometric and 1H NMR titrations of N-methoxyethyl-N'-(4-nitrophenyl)thiourea (3) by Bu(4-)NOAc show that in DMSO deprotonation of the receptor and formation of a hydrogen-bonded complex with anion proceed simultaneously but in MeCN deprotonation requires the participation of the second acetate anion. The formation constants of hydrogen-bon...
Article
Full-text available
The background of possible selectivity-affinity correlations and their limitations is reviewed, with typical crown ether and cryptand complexes, ionic associations, hydrogen bonded complexes and complexes driven by van der Waals, stacking or hydrophobic interactions, with some additional topics including associations based on metal coordination as...
Article
The kinetics of the alkaline hydrolysis of bis(p-nitrophenyl) phosphate (BNPP) have been studied in aqueous DMSO, dioxane, and MeCN. In all solvent mixtures the reaction rate steadily decreases to half of its value in pure water in the range of 0-70 vol % of organic cosolvent and sharply increases in mixtures with lower water content. Correlations...
Article
The anion of 4-imidazolecarboxylic acid (HL) stabilizes hydroxo complexes of trivalent lanthanides of the type ML(OH)+ (M = La, Pr) and M2L(n)(OH)(6-n) (M = La, n = 2; M = Pr, n = 2, 3; M = Nd, Eu, Dy, n = 1-3). Compositions and stability constants of the complexes have been determined by potentiometric titrations. Spectrophotometric and (1)H NMR t...
Article
Imine formation between 25 aldehydes and 13 amines in aqueous solution in the pH range 7–11 was studied by 1H NMR spectroscopy. A three-parameter linear equation correlating logarithms of imine formation constants with pKa and HOMO energies of amines and LUMO energies of aldehydes is proposed. In view of the widespread occurrence of imine-forming p...
Article
Interpretation of the role of metal ions in catalysis in terms of direct binding of the catalyst to the transition state of the uncatalyzed reaction allows one to view transition states as ligands and to apply the concepts elaborated for analysis of stability of coordination compounds to reactivity. This paper reviews recent results on kinetics of...
Article
Full-text available
A chiral cyclophane-type macrocycle bearing two thiol groups has been prepared by chemical modification of S,S-(+)-tetrandrine. Cleavage of p-nitrophenyl acetate by deprotonated form of this macrocycle proceeds with a rate constant expected for a simple thiol anion of similar basicity, but the reactivity toward p-nitrophenyl esters of N-protected a...
Article
Neutral aqueous solutions of cerium ammonium nitrate obtained by dilution of their acetonitrile stock solution with imidazole buffer show high catalytic activity in the hydrolysis of bis(p-nitrophenyl) phosphate (BNPP) and better reproducibility than other similar systems, but suffer from low stability. The kinetics of catalytic hydrolysis is secon...
Article
Potentiometric titrations of N,N-bis(2-hydroxyethyl)glycine (bicine) in the presence of Ln(III) cations (Ln=La, Pr, Nd and Eu) in the pH range extended to ca. 9.5 reveal formation of two types of binuclear hydroxo complexes Ln2(bic)2(OH)4 and Ln2(bic)(OH)4+ (bicH=bicine) in addition to previously reported mononuclear mono- and bis-complexes Ln(bic)...
Article
Full-text available
Complexation of free and N-acetylated α-amino acid anions (Gly, Ala, Phe) and some structurally related guests by a dicationic cyclophane-type N,N′-dibenzylated chiral derivative of a bisisoquinoline macrocyclic alkaloid S,S-(+)-tetrandrine (DBT) has been studied by 1H-NMR titrations in D2O. In contrast to other macrocyclic hosts like cyclodextrins...
Article
Rate of the hydrolysis of bis(p-nitrophenyl) phosphate in 90% v/v aqueous DMSO increases 103–105 times in the presence of 1–2 mM alkaline-earth cations, which in the same concentration range do not affect the reaction rate in water.
Article
The hydroperoxide anion cleaves unactivated amides and peptides although it is completely unreactive toward ethyl esters. The cleavage by HO2(-) proceeds faster than by OH(-) and involves additional routes with general acid assistance by H2O2 and general base assistance by OH(-) and HO2(-). Cleavage of polypeptides occurs at the N-terminal peptide...
Article
Glycine and N,N-dimethylglycine stabilize La(III) hydroxide complexes of the type La2L2(OH)4 which possess phosphodiesterolytic activity close to that observed with most active tetravalent cations like Ce(IV).
Article
Potentiometric and spectrophotometric titrations of hydrogen peroxide in the presence of La(III), Nd(III), Pr(III) and Eu(III) cations reveal formation of several types of di-, tri- and tetranuclear species. Complexes M2(O2)2(OH)2 or the respective tetranuclear complexes M4(O2)4(OH)4 as well as their monoprotonated forms are observed for all cation...
Article
Kinetics of the hydroxylaminolysis of acetamide, glycinamide, glycylglycine and triglycine have been studied in the range of temperatures 37-60 degrees C as a function of pH and hydroxylamine concentration. Rate constants for specific acid, general-acid and general-base catalyzed pathways have been determined for all substrates (for glycine derivat...
Article
Interactions of aliphatic ,ω-diamines [H2N(CH2)nNH2, 2 ≤ n ≤ 8] with coproporphyrin I tetraanion (CP) were studied by spectrophotometry, fluorimetry and 1H NMR spectroscopy in the pH range 7–10 and ionic strengths 0.01–0.1 M. Diprotonated diammonium cations induce dimerization of CP by forming 1:1 complexes with CP which undergo much stronger self-...
Article
Potentiometric titrations of hydrogen peroxide in the presence of Y(III) revealed formation of dinuclear Y2(O2)22+ and Y2(O2)2(OH)2 complexes. Kinetics of the cleavage of bis(4-nitrophenyl) phosphate (BNPP) in the presence of Y(III) and H2O2 was studied at 25°C in pH range 6–8 and at variable metal and H2O2 concentrations. Comparison of the pH-depe...
Article
Unusual second-order, in metal, kinetics were observed for the hydrolysis of bis(4-nitrophenyl) phosphate (BNPP) and 4-nitrophenyl diphenylphosphate (NPDPP) catalyzed by Y(III) in the presence of Bis-Tris propane (BTP) and Tris ligands at 25 °C in weakly basic aqueous solutions. Potentiometric and 1H-NMR titrations of BTP in the presence of Y(III)...
Article
Potentiometric titrations of the mixtures of lanthanide(III) perchlorates and bis-Tris propane (BTP) reveal formation of dinuclear hydroxo complexes M2(BTP)2(OH)n(6-n), where M = La(III), Pr(III), Nd(III), Eu(III), Gd(III), and Dy(III) and n = 2, 4, 5, or 6, in the pH range 7-9. ESI-MS data confirm the presence of dinuclear species. Kinetics of the...
Article
Dicationic N,N′-dibenzylated cyclophane-type derivative 1 of a bisisoquinoline macrocyclic alkaloid, S,S-(+)-tetrandrine, was prepared and characterized. In aqueous solution 1 undergoes dimerization, which was studied by the concentration dependence of its 1H NMR signals. The salt effect on the dimerization constant was analyzed by using different...
Article
Reaction of alkaline hydrogen peroxide with tris(4-nitrophenyl) phosphate generates ca 1.5 equiv. of 4-nitrophenol per mole of substrate with no evidence of build-up of an intermediate, and reaction of bis(4-nitrophenyl) phosphate anion is too slow to give a product. The initially formed bis(4-nitrophenyl) peroxophosphate is assumed to decompose to...
Article
A bicyclic polypeptide antibiotic thiostrepton forms both 1:1 and 1:2 complexes with anions (as tetrabutylammonium salts) in organic solvents with K2 >K1 for F- and K2<K1 for all other anions studied. Relative stabilities of 1:1 complexes in DMSO are AcO- approximatelyF->Cl-, Br-, HSO4-, H2PO4-, but in CHCl3 they follow a different order: Cl- appro...
Article
Reaction of alkaline hydrogen peroxide with bis(4-nitrophenyl) phosphate ion proceeds with simultaneous liberation of ca 2 equiv. of 4-nitrophenol per mole of substrate, and no evidence for build-up of an intermediate. Reaction of HO2− with the more activated 4-nitrophenyl phosphorochloridate gives 4-nitrophenol in up to 40% yield with simple first...
Article
Reaction of alkaline hydrogen peroxide with bis(4-nitrophenyl) phosphate ion proceeds with simultaneous liberation of ca 2 equiv. of 4-nitrophenol per mole of substrate, and no evidence for build-up of an intermediate. Reaction of HO2- with the more activated 4-nitrophenyl phosphorochloridate gives 4-nitrophenol in up to 40% yield with simple first...
Article
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Alzheimer's disease is characterized by the presence of insoluble, fibrous deposits composed principally of amyloid beta (Abeta) peptide. A number of studies have provided information on the fibril structure and on the factors affecting fiber formation, but the details of the fibril structure are not known. We used fluorescence quenching to investi...
Article
Micellar rate effects on hydrolyses of substituted benzoyl chlorides, 1, depend on headgroup charge and electron donation or withdrawal by substituents. Micellized sodium dodecyl sulfate, SDS, inhibits hydrolyses, and first-order rate constants in the micellar pseudophase, k‘M, decrease, relative to those in water, k‘W, over a range of ca. 10, but...
Article
[reaction: see text] A synthetic supramolecular system is described that models the effect of phosphoryl transfer in molecular recognition. beta-Cyclodextrin-6A-phosphate (pCD), which is shown to be a substrate of alkaline phosphatase, binds cationic aromatic guests, including anticancer agents, up to 100-fold better than native beta-CD. The above...
Article
Binding of Zn(II), Cu(II) and Fe(II) ions to A beta1-40, A beta1-42 and a single tryptophan mutant of Abeta 1-40 in solution at pH 7.4 was studied by fluorescent titration. Job plots and fitting of titration curves revealed formation of 1:1 and 1:2 peptide-metal complexes. For dimeric peptides A beta1-40 and A betaF4W the order of metal to peptide...
Article
Equilibrium constants of dimerization of the tetraanion of coproporphyrin-I free base were determined spectrophotometrically in aqueous solution at pH 9.0 in the presence of nine electrolytes, including salts of alkali metal, tetraalkylammonium and Ca(II) cations. Additions of all electrolytes promoted dimerization and the effect increased in the o...
Article
The kinetics of methanolysis of acetyl imidazole (1) and acetyl pyrazole (2) have been investigated under anhydrous conditions in the presence of Zn(ClO4)(2), Co(ClO4)(2), and HClO4 at 25 degrees C. In all cases, the plots of the pseudo-first-order rate constant for methanolysis (k(obs)) vs. [metal ion] or [HClO4] show saturation behavior indicativ...
Article
Equilibrium constants of dimerization of the tetraanion of coproporphyrin-I free base were determined spectrophotometrically in aqueous solution at pH 9.0 in the presence of nine electrolytes, including salts of alkali metal, tetraalkylammouium and Ca(II) cations. Additions of all electrolytes promoted dimerization and the effect increased in the o...
Article
Full-text available
The esterase and complexation properties of the zwitterionic form of a macrocyclic alkaloid (+)-tubocurarine possessing two phenolic nucleophilic groups are described. Cleavage of 4-nitrophenyl esters of N-protected phenylalanine enantiomers involves reaction paths with one and two alkaloid molecules. Substrate binding enantioselectivity is large a...