Charles Eric Brown

Developments in analytical fourier-transform mass spectrometry

Abstract Development of a differentially-pumped, dual-cell geometry, coupled with the evolution of pulsed-laser desorption and Cs + -secondary-ion mass spectrometric (s.i.m.s.) desorption methods, has improved the analytical utility of Fourier-transform mass spectrometry (F.t.m.s.). A survey of applications and performances obtained in our laboratories is presented. Among the topics covered are ultra-high-resolution electron-impact and chemical-ionization mass spectra, gas chromatography/F.t.m.s. performance, pulsed Cs + -s.i.m.s./F.t.m.s. with cooled liquid matrices and solid samples, laser desorption/F.t.m.s. and accurate mass measurements taken under each of these modes of operation.

Interactions among carnosine, anserine, ophidine and copper in biochemical adaptation.

Abstract Recent findings indicate that carnosine, anserine and ophidine should chelate copper in the tissues where these dipeptides are present in high concentration. The observations that carnosine, anserine and ophidine are located in skeletal muscles exhibiting active oxidative metabolism and/or glycolysis and that their accumulation appears to occur ontogenetically at the same time as these tissues begin to function suggests that these dipeptides may be involved in the intracellular transport of copper for activation of cytochrome oxidase at the end of the electron transport chain and in the regulation of anaerobic glycolysis. This hypothesis provides explanations for the presence of ophidine in the skeletal muscle of whale, the presence of anserine in the flight muscles of birds, the regulatory mechanism that permits orderly replacement of the primary olfactory neuron within the nasal olfactory epithelium, and the high activity of carnosinase in the uterus.

Assay method for the in vivo quantitative determination of mineral content in bone

An in vivo assay for quantifying the mineral content of bone comprises placing living bone into or adjacent to the coil of a nuclear magnetic resonance (NMR) spectrometer, recording a 31 P NMR spectrum while the bone is stationary, and comparing the spectrum obtained with the NMR spectrum of a reference standard containing a known concentration of a reference compound. The assay can be used to diagnose and determine the efficacy of treatment of osteodystrophy if used in conjunction with radiographic densitometry to estimate the calcium content of the bone.

Apparatus and assay method for the quantitative determination of mineral content in bone

An assay method for the quantitative determination of the mineral content of bone comprises using proton decoupling and magic angle sample spinning techniques to record well resolved 31 P nuclear magnetic resonance spectra of unfractionated bone biopsy samples and characterizing the differences in mineral identity and content from those of normal bone. A rotor for performing the assay includes a compartment for the sample to be assayed, and a separate compartment for a reference material.

Laser desorption/fourier transform mass spectral analysis of various conducting polymers

Abstract Laser desorption/Fourier transform mass spectrometry provides very detailed characterization of conjugated aromatic ‘conducting’ polymers that cannot be obtained by other currently available techniques. The technique shows that many of the synthetic routes to these materials yield complex mixtures of dissimilar oligomers. Thus, it is not appropriate at present to attribute electrical conductivities to distinct, individual polymers. The intent of this paper is to present an introductory description of this analytical technique and to give examples of the experimental results that can be expected with intractable aromatic polymers which become electrically conductive upon doping.

Response of tissue phosphate content to acute dietary phosphate deprivation in the X-linked hypophosphatemic mouse

SummaryIn order to evaluate a possible role for tissue phosphate or phosphorylated compounds in mediating the increase in plasma 1,25(OH)2D3 levels during dietary phosphate deprivation, renal cortical phosphate content has been measured in both normal and X-linked hypophosphatemic mice on a normal diet and also after acute dietary phosphate deprivation. We find that the metabolism of inorganic phosphate and phosphorylated organic compounds in the renal cortex ofHyp mice is not altered in response to their very low levels of serum phosphate. Skeletal muscle does not lose inorganic phosphate and/or phosphorylated metabolites to compensate for drastic loses of serum phosphate during acute dietary deprivation in either normal orHyp mice. Furthermore, the chronic low level of serum phosphate and altered hormonal regulation inHyp mice do not produce alterations in mineral composition of the bone with the possible exception that the stoichiometry of the apatite might be slightly different.

Multiple forms of the cobalt(II)-carnosine complex.

Abstract Cobalt(II) ion and L-carnosine produce two different complexes when mixed in aqueous solution at pH 7.2. One complex has coordination of N-3 of the imidazole ring to the cobalt(II) and is produced when the concentration of peptide exceeds that of cobalt(II). The second complex has chelation of three nitrogen atoms of a single carnosine. This second complex produces a reversible oxygen carrier by making stable mixed chelates with additional carnosine, histidine or cysteine. These results indicate that cobalt complexes with mixed ligands should be of more importance in vivo than those with carnosine as the only ligand. They provide an explanation for the high activity and substrate specificity of carnosinase in kidney.

Multiple forms of the copper(II)–carnosine complex

The effects of pH, temperature, and stoicheiometry on e.s.r. spectra of the copper(II)–carnosine complex have been measured at both X- and S-band. Four different complexes of Cu2+ and carnosine are found. At physiological pH a magnetically coupled copper(II) dimer is formed, but this is converted into a monomer in which the Cu2+ is co-ordinated to four equivalent carnosine molecules when the carnosine is present in excess. Anserine produces the same complexes as does carnosine, but homocarnosine and glycyl-L-histidine produce only the monomeric complex. The mechanism of crystallization of copper–carnosine and its possible importance in biological systems is reappraised.

Regulation of plasma 1,25-(OH)2-D3 by phosphate: Evidence against a role for total or acid-soluble renal phosphate content

SummaryIn order to evaluate a possible role for tissue phosphate or phosphorylated compounds in mediating the increase in plasma 1,25-(OH)2-D3 levels during dietary phosphate deprivation, measurements of total and acid-soluble renal cortical phosphate content have been made in both intact and hypophysectomized (hypox) rats eating a normal diet and also after four days of dietary phosphate deprivation. Similar measurements were also made in phosphate-deprived hypophysectomized rats replaced with growth hormone (GH). Total and acid-soluble renal cortical phosphate content averaged 81±8 µmol/g and 4.1±0.6 µmol/g, respectively, in intact rats eating the normal diet and were not significantly altered after phosphate deprivation despite a fall in plasma phosphate of about 40% and a fourfold increase in plasma 1,25-(OH)2-D3 levels. Total and acid-soluble renal cortical phosphate content levels were higher in hypox rats, averaging 92±8 µmol/g and 4.9±0.7 µmol/g, respectively, but also did not change after phosphate deprivation. Replacement of phosphate-deprived hypox rats with GH resulted in a further fall in plasma phosphate and a significant increase in plasma 1,25-(OH)2-D3 levels, but there was no change in either total or acid-soluble renal cortical phosphate content. The distribution of organophosphorus compounds in the acid-soluble phosphate fraction in these experiments was also evaluated using31P NMR spectroscopy. Although there appeared to be an increase in the total concentration of organophosphorus compounds after phosphate deprivation, this effect was not altered by hypophysectomy or by replacement of phosphate-deprived hypox rats with GH. These data suggest that unless phosphate deprivation affects only a small or specific cellular phosphate pool, some factor other than renal cell inorganic phosphate content must initiate the increase in renal 1,25-(OH)2-D3 synthesis that occurs during phosphate deprivation.

Evidence that carnosine and anserine may participate in Wilson's disease

Abstract Carnosine, anserine and copper(II) ion all bind to specific sites on bovine serum albumin, and, in addition, both dipeptides chelate copper(II) ion in the absence of serum albumin. Thus a solution of dipeptide, copper(II) ion and serum albumin exhibits several complexes that arise from the competing binding reactions. Since a change in this complex equilibrium might occur in Wilsons disease, we have investigated the reactions between the various complexes with NMR and ESR spectroscopy. Serum albumin simultaneously binds the copper(II) ion and carnosine to separate sites rather than forming a mixed chelate, but carnosine still is capable of competing with serum albumin for subsaturating amounts of copper.