Catalysis of hydrolysis of a schiff base by a carboxyl-containing poly(ethylenimine) derivative

Hydrolysis of 3-methyl-2-cyclohexenylidene laurylamine (I) in the presence and absence of laurylsuccinoylpoly(ethylenimine) has been studied. Water attack on the conjugate acid of I in the polymer environment is about 10² times faster than in bulk medium. To achieve the same rate in bulk media by general base catalysis, about 70 M acetate or cacodylate would be needed. This indicates that the reactivity of the carboxylate attached to the polymer is substantially enhanced by the polymer environment.     

Applications of nuclear magnetic resonance in biochemistry: An analysis of the aromatic region of the proton magnetic resonance spectrum of staphylococcal nuclease

Summary General procedures for the simplification and analysis of nuclear magnetic resonance spectra of proteins are presented. These are illustrated with current results with the enzyme staphylococcal nuclease which have permitted a partial analysis of the aromatic region of its proton nuclear magnetic resonance spectrum.

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Zusammenfassung Allgemeine Verfahren zur Auswertung und Vereinfachung der kernmagnetischen Resonanzspektren von Proteinen werden diskutiert und an Hand neuer Ergebnisse mit dem Enzym Staphylococcus-Nuclease demonstriert. Bei diesem Enzym gelang eine Teilanalyse des aromatischen Bereichs des KMR-Spektrums.

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Abbreviations used Nase Staphylococcal nuclease from Foggi strain - Nase-Dl selectively deuterated analog of Nase in which all amino acids except the following are deuterated — (1) Trp; (2) Met; (3) Tyr in ring positions 2 and 6; (4) His in ring methine 2; (5) Asx -methylene; and (6) Glx -methylene - HMS hexamethyldisiloxane - CAT computer of average transients - EDTA ethylendiaminetetraacetate     

The boat conformation of α-parachloral. Notes on the revised structures of α- andβ-parachloral

The boat conformation of-parachloral [2,4,6-tris(trichloromethyl)-1,3,5-trioxane] has been confirmed by X-ray crystallography. Evidence for a chair conformation based upon calculations of dipole moments has been shown to be unreliable, but the possibility of this existing in solution has been studied by¹H and¹³C NMR spectroscopy. The X-ray structures of both- and-parachloral have been redetermined.     

Complexes of chromium(III) with nitrilotriacetic acid and their extraction by solutions of aliquat-336 in dichloro-ethane

It has been shown that chromium(III) and nitrilotriacetic acid (NTA; H₃Z) form only a series of 1:1 complexes in solution. The violet uncharged species [CrZ(H₂O)₂] cannot be extracted by a solution of the long-chain quaternary ammonium chloride, Aliquat-336, in dichloroethane. Its acid dissociation constant (pK₁ = 5.87) was determined spectrophotometrically. On increasing the pH of the solution the blue anion CrZ(H₂O)(OH)^- of pK₂=8.74 and its conjugate base the binegative anion CrZ(OH)^2-₂ of pK₃= 11.81 are successively formed. Both of these anionic species are extracted by Aliquat-336 with maximal extraction (ca. 60%) at about pH 9. At still higher pH values the olive-green anion, CrZ(OH)₃^3-of much lower or negligible extractability, is formed.     

Studies with dithizone--XII. Formation of thiadiazolines by condensation with aldehydes and ketones

The red colour that develops when mineral acids are added to solutions of dithizone (I; 3-mercapto-1,5-diphenylformazan) in certain samples of dioxan is mainly due to the formation of 2-methyl-3-phenyl-5-phenylazo-1,3,4-thiadiazoline (II) derived in part from adventitious traces of 2-methyldioxalane. A purple compound of molecular formula C(13)H(10)N(4)S is also formed from (I) by an independent and slower reaction. The thiadiazoline (II) is readily prepared from (I) and acetaldehyde, but analogous compounds from formaldehyde benzaldehyde, acetone and ethyl methyl ketone are obtained in better yield by starting from diphenylthiocarbazide. Di-p-tolyldithizone gives similar reactions. Reduction of the thiadiazoline (II) [which has spectra very closely resembling those of 1:1 complexes of (I) with arylmercury (II) cations] with ammonium hydrogen sulphide in ethanol yields diphenylthiocarbazide by opening of the hetero-ring and elimination of an alkyl residue from the intermediate 3-alkylmercapto-1,5-diphenylformazan. Other examples of nucleophilic displacements from the formazan group by SH(-) have been investigated.     

Real time MRI-ultrasound image guided stereotactic prostate biopsy

To report a technique for target directed transperineal ultrasound guided biopsy using high resolution endorectal MRI images Ultrasound fusion. Two patients presented after external beam irradiation for prostate cancer with a rising PSA. An Endorectal MRI using a 1.5 Tesla scanner was obtained. Subsequently a Transrectal Ultrasound guided biopsy was performed. The Ultrasound probe was fixed to a stepper-stabilizer to provide a reference coordinate system for stereotaxic needle biopsy needle placement. The MRI image set was fused to the Ultrasound images in real time. Abnormal areas determined in the MR images were targeted for biopsy. Recurrent prostate carcinoma was detected pathologically in 3 of 4 stereotactic biopsies. Abnormal areas suspicious for cancer detected on T1 weighted images obtained in a strong field Endorectal MRI scan can be targeted for stereotactic biopsy using Transrectal Ultrasound. This image guide technique may be very useful in directing biopsies.