Electrophilic properties of nitroheterocyclic compounds. Potential hypoxic cells radiosensitizers

Investigation of the reduction potential and calculation of the partition coefficient n-octanol/water allow the assessment of the potential suitability of nitropirydine N-oxide compounds in radiotherapy of cancer. Experiments were carried out using cyclic voltammetry with HMDE as working electrode. The electrode reduction of the investigated compounds is quite irreversible and strongly dependent on pH.     

The stereocontrolled total synthesis of altohyrtin A/spongistatin 1: fragment couplings, completion of the synthesis, analogue generation and biological evaluation

The antimitotic marine macrolide altohyrtin A/spongistatin 1 has been synthesised in a highly convergent and stereocontrolled manner, thus contributing to the replenishment of the largely exhausted material from the initial isolation work. Coupling of the AB- and CD-spiroacetal subunits by a stereoselective aldol reaction was achieved by using either a lithium (67 : 33 dr) or boron enolate (90 : 10 dr). A highly (Z)-selective Wittig coupling was used to unite the northern hemisphere aldehyde with the southern hemisphere phosphonium salt . Deprotection and subsequent regioselective macrolactonisation on a triol seco-acid completed the synthesis of altohyrtin A. Two structural analogues were also prepared and evaluated as growth inhibitory agents against a range of human tumour cell lines, including Taxol-resistant strains, alongside altohyrtin A and paclitaxel (Taxol), revealing that dehydration in the E-ring is tolerated and results in enhanced cytotoxicity (at the low picomolar level), whereas the presence of the full C44-C51 side-chain appears to be crucial for biological activity.     

Identification of smoked Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) using PCR-restriction fragment length polymorphism of the p53 gene

Raw and smoked samples of Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) were identified using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of the p53 gene. DNA from S. salar and 0. mykiss was amplified by using primers flanking exons 5 to 6 of the p53 nuclear gene. PCR products of different length were obtained for each species (532 and 518 base pairs, respectively). Sequences of PCR products obtained from S. salar and O. mykiss were compared in the search for polymorphic restriction sites. The restriction fragments obtained with Eco RV, Hinf I, and Taq I endonucleases showed interspecific polymorphism, making it a useful method for identification of Atlantic salmon and rainbow trout.     

Construction of Heterometallic Cubanes

Incorporation of M(CO)(3) fragments by trinuclear Ti complexes [{Ti(3)Cp(μ(3)-CR)}(μ-O)(3)] and [{Ti(3)Cp(μ(3)-N)}(μ-NH)(3)] (Cp*=eta(5)-C(5)Me(5)) leads to the formation of an unprecedented class of heterometallic clusters with cubane structure [e.g., Eq. (a)]. Density functional calculations on these complexes indicate the existence of electron delocalization in the Ti(3)M cores (M=Cr, Mo, W).     

Direct measurement of homovanillic, vanillylmandelic and 5-hydroxyindoleacetic acids in urine by capillary electrophoresis

Separation conditions in CE, with a neutral coated capillary and reversed polarity, have been optimised to make direct measurement of vanillylmandelic acid, homovanillic acid and 5-hydroxyindoleacetic acid possible in urine samples without pre-treatment. The method developed has been validated, presenting adequate parameters for linearity, accuracy and precision. Detection limits range from 0.03 to 2.5 microM. Finally the method has been applied to urine samples taken from patients, both adults and children, in hospital. Some of them were also measured by immunoassay and HPLC-electrochemical detection and results have been compared.     

Method development for the determination of anthocyanins in red wines by high-performance liquid chromatography and classification of German red wines by means of multivariate statistical methods

A novel, positively charged, copolymer of allylamine and 2-hydroxy-3-methacryloyl-beta-cyclodextrin was synthesized to be used as a chiral selector in capillary electrophoresis. In the copolymer, cyclodextrin molecules are spaced from the backbone though a spacer arm which prevents sterical hindrance of the CD cavity. The self-mobility of the CD polymer in its charged form, opposite to the analytes, is the cause for the enhanced separation factor provided by this selector. Moreover, the positive charged polymer induces a reversal of electroosmotic flow which is beneficial in enantioseparations of acidic compounds as it reduces analysis time and increases peak efficiency. The ability of this copolymer to act as a CE chiral selector in the separation of 2,4-dinitrophenylamino acid enantiomers was investigated in coated and uncoated capillaries and its performance was much better then that of native beta-cyclodextrin.     

Dynamics of the Electric Double Layer: Analysis in the Frequency and Time Domains

No rigorous theory of electrokinetic phenomena is conceivable without properly accounting for double layer polarization under the action of external fields. Since processes leading to such polarization need a finite time to develop, an analysis of the behavior of the quantities of interest (potential and ion concentration profiles, particle or fluid velocity, and so on) as a function of time should be extremely illustrative. In this work, we analyze how those quantities evolve in the nanosecond to microsecond time range after the application of an electric field. The network method is proposed (in which, essentially, an electric circuit simulator program is used to solve the differential equations involved, after their proper interpretation in terms of fluxes and forces) to gain information about the evolution with time of the potential, counterion, and co-ion perturbations, the particle velocity, and the fluid velocity profile. The performance of the method is first ckecked in the frequency domain, for which rigorous solutions exist, and then the procedure is used in the time domain. Reasons are discussed for the observed time dependencies of the analyzed quantities. Copyright 2000 Academic Press.     

Hydrothermal Synthesis and Structure of a Novel 1-D Mn(II) Compound with Carboxlyto and Imidazole Ligands

1 INTRODUCTION Mn complexes containing carboxylato ligands attract considerable interest due to the richness in structural chemistry[1～4] and potential applications in catalysis[5, 6], for example, some highly efficient Mn catalase mimics[7, 8]. Recently, we focus on the hy- drothermal synthesis of manganiferous coordination polymers using multiple carboxylato and nitrogen- containing ligands[9, 10]. As one of the interesting bridge ligands, terephthalato ligand (ta) can provide multipl…     

Crystal structure and magnetic interactions in nickel(II) dibridged complexes formed by two azide groups or by both phenolate oxygen-azide, -thiocyanate, -carboxylate, or -cyanate groups

Tridentate/tetradentate Schiff base ligands L(1) and L(2), derived from the condensation of o-vanillin or pyridine-2-aldehyde with N,N-dimethylethylenediammine, react with nickel acetate or perchlorate salt and azide, cyanate, or thiocyanate to give rise to a series of dinuclear complexes of formulas [Ni(L(1))(micro(1,1)-N(3))Ni(L(1))(N(3))(OH(2))].H(2)O (1), [[Ni(L(1))(micro(1,1)-NCS)Ni(L(1))(NCS)(OH(2))][Ni(L(1))(micro-CH(3)COO)Ni(L(1))( NCS) (OH(2))]] (2) [[2A][2B]], [Ni(L(1))(micro(1,1)-NCO)Ni(L(1))(NCO)(OH(2))].H(2)O (3), and [Ni(L(2)-OMe)(micro(1,1)-N(3))(N(3))](2) (4), where L(1) = Me(2)N(CH(2))(2)NCHC(6)H(3)(O(-))(OCH(3)) and L(2) = Me(2)N(CH(2))(2)NCHC(6)H(3)N. We have characterized these complexes by analytical, spectroscopic, and variable-temperature magnetic susceptibility measurements. The coordination geometry around all of the Ni(II) centers is a distorted octahedron with bridging azide, thiocyanate/acetate, or cyanate in a micro(1,1) mode and micro(2)-phenolate oxygen ion for 1-3, respectively, or with a double-bridging azide for 4. The magnetic properties of the complexes were studied by magnetic susceptibility (chi(M)) versus temperature measurements. The chi(M) nus T plot reveals that compounds 1 and 4 are strongly ferromagnetically coupled, 3 shows a weak ferromagnetic behavior, and 2 is very weakly antiferromagnetically coupled.