Comparative enantioseparations with native beta-cyclodextrin and heptakis-(2-O-methyl- 3,6-di-O-sulfo)-beta-cyclodextrin in capillary electrophoresis

Twenty-three cationic chiral analytes were resolved in capillary electrophoresis using native beta-cyclodextrin and single isomer heptakis-(2-O-methyl-3,6-di-O-sulfo)-beta-cyclodextrin as chiral selectors. For 12 of 16 chiral analytes resolved with both chiral selectors the enantiomer migration order was opposite. In selected cases the structure of cyclodextrin-analyte complexes in aqueous solution was investigated using one-dimensional transverse rotating frame nuclear Overhauser and exchange spectroscopy. It was found that in contrast to mainly inclusion-type complexes between chiral analytes and beta-cyclodextrin, external complexes are formed between the chiral analytes and structurally crowded, highly charged heptakis-(2-O-methyl-3,6-di-O-sulfo)-beta-cyclodextrin.     

MACBETHSort: a multiple criteria decision aid procedure for sorting strategic products

Efficient companies need to know which their strategic products are. For this purpose, the ABC classification based on the item’s value was developed and was used for a long time. Later, it was recognised that several other criteria need to be considered and multi-criteria ranking methods were applied. However, the classes have always been defined based only on a relative proportion. Therefore, the number of products in a class is independent of the actual importance of the products. In this paper, a new sorting procedure MACBETHSort is introduced, which is an evolution of the choice, ranking and rating technique MACBETH. The procedure has been validated in a real case study for assigning access and entrance solutions in ABC classes.     

DNA recognition by the anthracycline antibiotic respinomycin D: NMR structure of the intercalation complex with d(AGACGTCT)2

Respinomycin D is a member of the anthracycline family of antitumour antibiotics that interact with double stranded DNA through intercalation. The clinical agents daunomycin and doxorubicin are the most well-studied of this class but have a relatively simple molecular architecture in which the pendant daunosamine sugar resides in the DNA minor groove. Respinomycin D, which belongs to the nogalamycin group of anthracyclines, possesses additional sugar residues at either end of the aglycone chromophore that modulate the biological activity but whose role in molecular recognition is unknown. We report the NMR structure of the respinomycin D-d(AGACGTCT)2 complex in solution derived from NOE restraints and molecular dynamics simulations. We show that the drug threads through the DNA double helix forming stabilising interactions in both the major and minor groove, the latter through a different binding geometry to that previously reported. The bicycloaminoglucose sugar resides in the major groove and makes specific contacts with guanine at the 5'-CpG intercalation site, however, the disaccharide attached at the C4 position plays little part in drug binding and DNA recognition and is largely solvent exposed.     

Protein micropatterns using a pH-responsive polymer and light

Protein and peptide microarrays are popular candidates for medical diagnostics because of the possibility for high sensitivity and simultaneous marker screening. To realize the potential of these arrays, new strategies for ligand patterning are needed. We report a method for patterning proteins that utilizes a pH-responsive polymer, deep ultraviolet (DUV) light, and a photoacid generator (PAG). Poly(3,3'-diethoxypropyl methacrylate) (PDEPMA) contains reactive acetal side chains which are converted to aldehydes following treatment with acid. PDEPMA was spin-coated onto Si-SiO(2) substrates and was either chemically deprotected with 1 M HCl or photochemically deprotected by exposure to DUV in the presence of triphenylsulfonium triflate. Conversion to aldehyde groups was confirmed with Purpald and by reaction with a green fluorescent hydroxylamine. Protein microarrays were demonstrated by incubating photochemically patterned surfaces with an aldehyde-reactive biotin followed by red fluorescent streptavidin. This methodology provides a new substrate for the precise patterning of both peptides and proteins for various biological applications including medical sensors.     

On the lifetime of excited states of frustration model of spin glasses

An analysis of the low energy excited states of the ± J model of Ising spins on a square lattice is developped in terms of clustering of solidary spins. Two types of clusters are exhibited : entropic and pinned clusters regarding the occurence of potential barriers in the relaxation. The mean reversal time of these clusters is determined and interpreted as one dimensional random walk in phase space. The size dependence of this mean reversal time varies as n² (n denoting the number of spins in the cluster) or $\text{n}{}^2\text{x exp(?}\text{ΔE}\text{k}{}_{\mathrm{B}}\text{T}\text{)}$ where ΔE is the potential barrier, instead of n in the case of ferromagnetic Ising model.     

Cyclocondensation adducts from the lewis acid mediated reaction of 4-acetoxy-2-azetidinone with siloxydienes

A successful trapping of 1-azetin-4-one with siloxydienes as cyclocondensation adducts is described.     

Critical dynamics of finite Ising model

The Glauber kinetics of Ising spins is considered as a queueing process and simulated event by event as first proposed by Bortz, Kalos, and Lebowitz. The advantage of this algorithm compared to the standard single-flip Monte Carlo method is discussed for the situation of slowing down of dynamics. This process is used to generate fluctuations of magnetization and energy in the critical regimeT=T_c of two-dimensional Ising models. The analysis of these fluctuations leads to numerical determination of the critical exponents for dynamics: for the size dependence of correlation time atT _c , and for frequency dependence of the power spectrumS()~ ^–µ . From the finite-size scaling hypothesis, scaling relations are settled which are confirmed by this numerical experiment.     

Heptakis(2-O-methyl-3,6-di-O-sulfo)-beta-cyclodextrin: a single isomer, 14-sulfated beta-cyclodextrin for use as a chiral resolving agent in capillary electrophoresis

The first single-isomer, 14-sulfated beta-cyclodextrin, the sodium salt of heptakis(2-O-methyl-3,6-di-O-sulfo)-beta-cyclodextrin (HMdiSu) has been used to separate 24 pharmaceutical weak base enantiomers in pH 2.5 background electrolytes using capillary electrophoresis. For the weakly binding bases, the cationic effective mobilities decreased, approached zero, and then increased again. For the strongly binding bases, the cationic effective mobilities decreased, became anionic at very low concentrations of HMdiSu, passed an anionic mobility maximum, then decreased again as the HMdiSu concentration was increased. Viscosity corrections according to Walden's rule did not eliminate these unexpected effective mobility extrema. The mobility extrema were rationalized by extending the charged resolving agent migration model (CHARM model) to include ionic strength effects.