Nuclear magnetic resonance determination of intramolecular distances in bovine pancreatic trypsin inhibitor using nitrotyrosine chelation of lanthanides.

Nitration of tyrosine has been investigated as a means for chemically introducing lanthanide chelating sites at known positions in proteins. The low-field portions of the 250-MHZ and 270-MHZ 1H nuclear magnetic resonance spectra of native and chemically modified bovine pancreatic trypsin inhibitor have been studied in the presence of lanthanide ions. Comparisons of spectral changes observed with native, mononitro (tryosine 10) and dinitro (tyrosines 10 and 21) derivatives enable these changes to be separately attributed to metal bound at nitrotyrosine 21, nitrotyrosine 10, or the set of five carboxyl groups. The pH dependence of Pr(III) and Eu(III) induced chemical shifts yields stability constants of 50 and 159 M-1 for the association between lanthanides and nitrotyrosines 10 and 21, respectively. Correlation times for the interactions with Gd(III) bound to specific nitrotyrosines are estimated from the induced line broadening of resonances of the nitrotyrosine ring protons. These stability constants and correlation times are used to determine the distances from the different metal binding sites to buried backbone NH protons having resolved resonances. Comparisons with distances in the x-ray crystal structure give assignments of the NH resonances to a small set of buried backbone NH's.     

Complete tyrosine assignments in the high field 1H nuclear magnetic resonance spectrum of the bovine pancreatic trypsin inhibitor.

The low-field portions of the 250-MHz 1H nuclear magnetic resonance (NMR) specra of native and chemically modified bovine basic pancreatic trypsin inhibitor (BPTI) have been studied as a function of pH over the range pH 5-13. Resonances associated with the 16 protons of the aromatic rings of the four BPTI tyrosines have been located and assigned to specific tyrosyl residues. Titrations of pH yielded pK's for tyrosines-10, -21, -23, and -35 of 10.4, 11.0, 11.7, and 11.1, respectively. The resonances associated with the nitrotyrosine-10 protons of mononitrated BPTI and the nitrotyrosine-10 and -21 protons of dinitrated BPTI have been similarly located, assigned and titrated yielding pK's for nitrotyrosine-10 and -21 of 6.6 and 6.4, respectively. The high-field NMR spectrum indicates that the aromatic ring of tyrosine-35 rotates less than 160 times per second at 25 degrees for pH's in the range 5-9.     

Reduction of hypoxic pulmonary vasoconstriction during trichloroethylene anesthesia.

A double-lumen tube was inserted into the trachea of dogs anesthetized with intravenous pentobarbital (30-40 mg/kg). Blood flow/unit lung volume in each lung was measured with 133Xe. Both lungs were initially ventilated with oxygen and measurements of pulmonary blood flow, CO2 output, cardiac output, and blood gases were made. When nitrogen was administered to one lung blood flow was diverted to the opposite lung. The diversion of flow was reduced by the inhalation of 1% trichloroethylene but returned after withdrawal of the anesthetic. There were no significant changes in cardiac output. Changes in CO2 output and arterial Po2 were compatible with the xenon results. It is concluded that trichloroethylene may increase arterial hypoxemia by reducing vasoconstriction in hypoxic areas of lung.     

Detection of a β-Lactamase Markedly Active Against Carbenicillin in a Strain of Pseudomonas aeruginosa

Examination of the substrate profile of a number of beta-lactamases synthesized by strains of Pseudomonas aeruginosa has shown the presence of at least two distinct types of enzyme, one of which is more active against carbenicillin than against benzyl penicillin.