Sequence-specific fluorescence detection of DNA by polyamide-thiazole orange conjugates

Fluorescent methods to detect specific double-stranded DNA sequences without the need for denaturation may be useful in the field of genetics. Three hairpin pyrrole-imidazole polyamides 2-4 that target their respective sequences 5'-WGGGWW-3', 5'-WGGCCW-3', and 5'-WGWWCW-3' (W = A or T) were conjugated to thiazole orange dye at the C-termini to examine their fluorescence properties in the presence and absence of match duplex DNA. The conjugates fluoresce weakly in the absence of DNA but showed significant enhancement (>1000-fold) upon the addition of 1 equiv of match DNA and only slight enhancement with the addition of mismatch DNA. The polyamide-dye conjugates bound specific DNA sequences with high affinity (Ka > 10(8) M(-1)) and unwound the DNA duplex through intercalation (unwinding angle, phi, approximately 8 degrees). This new class of polyamides provides a method to specifically detect DNA sequences without denaturation.     

Copper and iron interactions with angiotensin-converting enzyme inhibitors. A study by fast-atom bombardment tandem mass spectrometry

Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd.     

A Sucrose-Based Approach to Enantiomerically Pure Glycerol Derivatives

Abstract

Taking advantage of the same configuration present at C-5 and C-5′ in sucrose, 6,6′-diprotected sucrose derivatives were transformed into enantiomerically pure glycerol derivatives. This was achieved by oxidative ring cleavage of both the glucopyranosyl ring as well as the fructofuranosyl moiety followed by reduction of the resulting tetraaldehyde and subsequent per-O-protection of the resulting pentahydroxy compound. The obtained intermediate was hydrolysed under acidic conditions to furnish two equivalents of partially protected chiral glycerol derivative per molecule of starting material. The efficiencies of sodium metaperiodate and lead tetraacetate as oxidizing agents were compared and the side reactions observed in these procedures were investigated.     

Graphical Representations of Speed: Obstacles Preservice K‐8 Teachers Experience

This study examines the difficulties college students experience when creating and interpreting graphs in which speed is one of the variables. Nineteen students, all preservice elementary or middle school teachers, completed an upper‐level course exploring algebraic concepts. Although all of these preservice teachers had previously completed several mathematics courses, including calculus, they demonstrated widespread misconceptions about the variable speed. This study identifies four cognitive obstacles held by the students, provides excerpts of their graphical constructions and verbal interpretations, and discusses potential causes for the confusion. In particular, misconceptions arose when students interpreted the behavior and nature of speed within a graphical context, as well as in situations where they were required to construct a graph involving speed as a variable. The study concludes by offering implications for the teaching and learning of speed and its interpretation within a graphical setting.     

Sensory threshold estimation from a continuously graded response produced by reflex modification audiometry

This article describes the use of reflex modification to determine sensory detection thresholds. The method is based upon the finding that low-intensity sensory stimuli presented shortly before a reflex eliciting stimulus are able to modify the amplitude of the reflex. The extent of such modification is related to the intensity of the initial low-intensity stimulus. In contrast to earlier reported procedures for threshold estimation, the method described in this article consists of fitting a smooth function to the relationship between startle response amplitude and the intensity of the inhibiting stimulus. The method entails fitting a cubic spline function to the medians of the square-root reflex amplitude at each prestimulus intensity. The resulting audiometric curves closely approximate audiometric data obtained from traditional operant methods both in sensitivity and shape. Parametric data are also presented that allow for optimizing stimulus presentation so as to obtain reliable thresholds using a minimal number of test trials. The procedures developed in this article may prove useful in other situations involving the estimation of a threshold effect from a continuously graded response.     

Hydroxynitrile lyase catalysed synthesis of heterocyclic (R)- and (S)-cyanohydrins

Heterocyclic saturated five- and six-membered ring ketones sometimes bearing a methyl substituent were reacted with HCN under enzyme catalysis using recombinant hydroxynitrile lyase from Hevea brasiliensis, as a rule (S)-selective, and Prunus amygdalus, (R)-selective. The resulting cyanohydrins were stereochemically characterised. The steric outcome of these transformations was interpreted by molecular modelling.     

A rapid technique to determine the internal area function of finite-length ducts using maximum length sequence analysis

This paper describes a rapid technique for reconstruction of the internal area function of a duct using blockage-induced eigenvalue shifts determined from eigenfrequencies measured under two sets of duct termination boundary conditions. A single broad band maximum length sequence (MLS) measurement of short duration is utilized to obtain the transfer function of the duct, which in turn can be utilized to determine its eigenvalue shifts and subsequently its internal area function using an inverse perturbation technique. The reconstruction results display the same order of accuracy as those obtained previously using swept sine measurements of extended duration. An expression for the determination of the area function is presented utilizing resonant frequency information alone, thus rendering duct length determination unnecessary. A computational routine further simplifies the process such that the accuracy of the technique could be ascertained for a range of configurations including longer ducts and ducts that initially have nonuniform internal cross section over their length. Development of a relationship between obstacle length and wavelength of the lowest eigenfrequency required for successful reconstruction is also described. This is an important result for longer ducts where measurement of lower eigenfrequencies may present problems using standard measurement equipment.