A study of some problems in determining the stoicheiometric proton dissociation constants of complexes by potentiometric titrations using a glass electrode

Possible errors in the measurement of acid dissociation constants by potentiometric titration techniques have been considered, with particular references to nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA). Unknown junction potentials can arise when pH measurements are carried out using a glass electrode with saturated calomel reference electrode which have been previously calibrated with a standard buffer solution. The magnitude of the influence of these unknown potentials has been demonstrated and an experimental procedure recommended which gives meaningful results.The precision of calculated acid dissociation constants will also be influenced by the presence of cationic species (e.g. H₄L⁴), the total acid strength, the absolute values of the constants and the value accepted for the auto-dissociation constant of water (K_w). All these factors have been considered quantitatively and their effect on metal complex formation constants, calculated from these acid dissociation constants, noted. The proton dissociation constant of the cationic species of NTA (i.e. H₄L⁺) has been found to have the value of pK₀=0.80 at 20° and μ=0.10 M.     

The first example ot the benzo[b]pyrimido[4,5-f]azocine king system

Base catalyzed cyclization of ethyl 4-[2-(2-amino-4,5-dimethoxyphenyl)ethyl]-2-phenylpyrimidine-5-carboxylate, derived from ethyl 4-methyl-2-phenyl-5-pyrimidinecarboxylate and 3,4-dimethoxy-6-nitrobenz-aldehyde, gave 5,6-dihydro-8,9-dimethoxy-3-phenylbenzo[b]pyrimido[4,5-f]azocine-12(11H)-one, the first reported example of this ring system.     

Nachweis und Bestimmung des Bleis

Ohne Zusammenfassung     

Towards a Pólya–Carlson dichotomy for algebraic dynamics

We present results and background rationale in support of a Pólya–Carlson dichotomy between rationality and a natural boundary for the analytic behaviour of dynamical zeta functions of compact group automorphisms.     

Synchrotron radiation circular dichroism spectroscopy of proteins and applications in structural and functional genomics

The technique of Synchrotron Radiation Circular Dichroism (SRCD) spectroscopy and its advantages over conventional circular dichroism spectroscopy are described in this tutorial review, as well as recent applications of the technique in structural and functional genomics.Circular dichroism (CD) spectroscopy is a well-established method in biological chemistry and structural biology, but its utility can be limited by the low flux of the light source in the far ultraviolet and vacuum ultraviolet wavelength regions in conventional CD instruments. The development of synchrotron radiation circular dichroism (SRCD), using the intense light of a synchrotron beam, has greatly expanded the utility of the method, especially as a tool for both structural and functional genomics. These applications take advantage of the enhanced features of SRCD relative to conventional CD: the ability to measure lower wavelength data containing more electronic transitions and hence more structural information, the higher signal-to-noise hence requiring smaller samples, the higher intensity enabling measurements in absorbing buffers and in the presence of lipids and detergents, and the ability to do faster measurements enabling high throughput and time-resolved spectroscopy.This article discusses recent developments in SRCD instrumentation, software, sample preparation and methods of analyses, with particular emphasis on their applications to the study of proteins. These advances have led to new applications in structural genomics (SG), including the potential for fold recognition as a means of target selection and the examination of membrane proteins, a class of proteins usually excluded from SG programmes. Other SG uses include detection of macromolecular interactions as a screen for complex formation, and examination of glycoproteins and sugar components. In functional genomics (FG) new applications include screening for ligand binding as a means of identifying function, and examination of structural differences in mutant proteins as a means of gaining insight into function.     

Antibodies with broad specificity to azaspiracids by use of synthetic haptens

The development of general, sensitive, portable, and quantitative assays for the azaspiracid (AZA) class of marine toxins is urgently needed. Use of a synthetic hapten containing rings F-I of AZA to generate antibodies that cross-react with the AZAs via their common C28-C40 domain and use of these antibodies in ELISA and immunoaffinity columns are reported. This approach has many advantages over using intact azaspiracids (AZAs) derived from environmental samples or total synthesis as haptens for antibody development. A derivative of the levorotatory C28-C40 azaspiracid domain (1) was synthesized efficiently using a one-pot Staudinger reduction/intramolecular aza-Wittig reaction-imine capture sequence to form the H-I ring spiroaminal and a double intramolecluar hetero-Michael addition to assemble the F-G ring ketal. Conjugation of the hapten 1 to cBSA and immunization in sheep generated antibodies that recognized and bound to ovalbumin-conjugated 1 in the absence of AZA1. This binding was inhibited by 1 in a concentration-dependent manner. A mixture of AZA1, AZA2, AZA3, and AZA6 caused a degree of inhibition of antibody binding consistent with its total AZA content, rather than just its content of AZA1. This result suggests that the antibodies also have a similar affinity for AZA2, AZA3, and AZA6 as they do for AZA1 and that such antibodies are suitable for analysis of AZAs in shellfish samples.     

Blocks with nonabelian defect groups which have cyclic subgroups of index p

In representation theory of finite groups, one of the most important and interesting problems is that, for a p-block A of a finite group G where p is a prime, the numbers k(A) and ℓ(A) of irreducible ordinary and Brauer characters, respectively, of G in A are p-locally determined. We calculate k(A) and ℓ(A) for the cases where A is a full defect p-block of G, namely, a defect group P of A is a Sylow p-subgroup of G and P is a nonabelian metacyclic p-group M _n+1(p) of order p ⁿ⁺¹ and exponent p ⁿ for n \geqslant 2{n \geqslant 2}, and where A is not necessarily a full defect p-block but its defect group P = M _n+1(p) is normal in G. The proof is independent of the classification of finite simple groups.     

A model for optimal execution of atomic orders

Atomic Orders are the basic elements of any algorithm for automated trading in electronic stock exchanges. The main concern in their execution is achieving the most efficient price. We propose two optimal strategies for the execution of atomic orders based on minimization of impact and volatility costs. The first considered strategy is based on a relatively simple nonlinear optimization model while the second allows re-optimization at some time point within a given execution time. In both cases a combination of market and limit orders is used. The key innovation in our approach is the introduction of a Fill Probability function which allows a combination of market and limit orders in the two optimization models we are discussing in this paper. Under certain conditions the objective functions of both considered problems are convex and therefore standard optimization tools can be applied. The efficiency of the resulting strategies is tested against two benchmarks representing common market practice on a representative sample of real trading data.