Tributyl phosphate degradation by immobilized cells of aCitrobacter sp.

Tributyl phosphate (TBP), a plasticizer and solvent, is used in nuclear fuel reprocessing, generating TBP wastes laden with residual uranium. ACitrobacter sp. accumulated heavy metals via a phosphohydrolase(s) that precipitated metals with inorganic phosphate liberated from an organic phosphate “donor” molecule (TBP). Mutant analysis suggested that TBP hydrolysis was not attributable to a previously documented acid phosphatase (monoesterase). Purified monoesterase had little activity against phospho di- and triesters, had no requirement for Mg²⁺ or Mn²⁺, and was EDTA-resistant. Conversely, TBP cleavage by immobilized cells was enhanced by Mg²⁺, and ininhibited by Mn²⁺ and EDTA. A separate phosphotri/diesterase was implicated.     

Photosensitized dehydrochlorination of poly(vinyl chloride). III. Reaction of thermally degraded poly(vinyl chloride) with hydrogen chloride

Films prepared from thermally degraded poly(vinyl chloride) were photolyzed in the presence of hydrogen chloride. When the light was filtered through a Pyrex disk, the absorbance in the region between 270 nm and about 415 nm decreased and reached a minimum value but the absorbance increased at wavelengths shorter than 270 nm and longer than 415 nm. Maximum bleaching occurred at a wavelength which depended on that of the irradiating light. When the Pyrex filter was omitted, an additional slower photodehydrochlorination reaction was superimposed on the photobleaching reaction. Photolysis of hexane or ethanol solutions of 1,8-diphenyloctatetra-1,3,5,7-ene and hydrogen chloride showed a similar reaction involving bleaching of the absorption of the polyene structure. The problems of using absorbance as an indication of the extent of the photodegradation of poly(vinyl chloride) are discussed.     

The Scope and Generality of Bell’s Theorem

I present what might seem to be a local, deterministic model of the EPR-Bohm experiment, inspired by recent work by Joy Christian, that appears at first blush to be in tension with Bell-type theorems. I argue that the model ultimately fails to do what a hidden variable theory needs to do, but that it is interesting nonetheless because the way it fails helps clarify the scope and generality of Bell-type theorems. I formulate and prove a minor proposition that makes explicit how Bell-type theorems rule out models of the sort I describe here.     

Synthesis of Oligonucleotides Containing Trans Mitomycin C DNA Adducts at N6 of Adenine and N2 of Guanine

Mitomycin C, (MC), an antitumor drug, is a DNA alkylating agent currently used in the clinics. Inert in its native form, MC is reduced to reactive mitosenes, which undergo nucleophilic attack by guanine or adenine bases in DNA to form monoadducts as well as interstrand crosslinks (ICLs). Although ICLs are considered the most cytotoxic lesions, the role of each individual adduct in the drug's cytotoxicity is still not fully understood. Synthetic routes have been developed to access modified oligonucleotides containing dG MC-monoadducts and dG-MC-dG ICL at a single position of their base sequences to investigate the biological effects of these adducts. However, until now, oligonucleotides containing monoadducts formed by MC at the adenine base had not been available, thus preventing the examination of the role played by these lesions in the toxicity of MC. Here, we present a route to access these substrates. Structural proof of the adducted oligonucleotides were provided by enzymatic digestion to nucleosides and high-resolution mass spectral analysis. Additionally, parent oligonucleotides containing a dG monoadduct and a dG-MC-dG ICL were also produced. The stability and physical properties of all substrates were compared via CD spectroscopy and UV melting temperature studies. Finally, virtual models were created to explore the conformational space and structural features of these MC-DNA complexes.     

The Interaction of Benzyl Alcohol with Trimethoxyboroxine : Amine Adducts of Triarylboroxines as Model Compounds

The interaction of benzyl alcohol with trimethoxyboroxine has been investigated by hydrogen-1 and carbon-13 NMR and IR spectroscopy. These techniques indicate formation of a weak Lewis acid/base adduct, additionally stabilized by a hydrogen-bonding interaction, which undergoes rapid ligand exchange at room temperature. The system has been modelled by the synthesis and characterization of a series of amine-triarylboroxine adducts. These adducts rapidly undergo ligand dissociation-recombination in solution with ΔG⁺ of ca. 40-50 kJ/mol.     

Charge Site Mass Spectra: Conformation-Sensitive Components of the Electron Capture Dissociation Spectrum of a Protein

A conventional electron capture dissociation (ECD) spectrum of a protein is uniquely characteristic of the first dimension of its linear structure. This sequence information is indicated by summing the primary c ^m+ and z ^m+? products of cleavage at each of its molecular ion’s inter-residue bonds. For example, the ECD spectra of ubiquitin (M?+?nH)ⁿ⁺ ions, n?=?7–13, provide sequence characterization of 72 of its 75 cleavage sites from 1843 ions in seven c ^(1–7)+ and eight z ^(1–8)+? spectra and their respective complements. Now we find that each of these c/z spectra is itself composed of “charge site (CS)” spectra, the c ^m+ or z ^m+? products of electron capture at a specific protonated basic residue. This charge site has been H-bonded to multiple other residues, producing multiple precursor ion forms; ECD at these residues yields the multiple products of that CS spectrum. Closely similar CS spectra are often formed from a range of charge states of ubiquitin and KIX ions; this indicates a common secondary conformation, but not the conventional α-helicity postulated previously. CS spectra should provide new capabilities for comparing regional conformations of gaseous protein ions and delineating ECD fragmentation pathways.