Pseudomonas aeruginosa H181 and H185 are resistant to initial exposure to polymyxin B and continue to grow in its presence. Growth of the strains in the presence of 50 U of polymyxin B per ml was characterized by a doubling time of 120 min, whereas the doubling time in the absence of polymyxin was 60 min. Growth for two generations in the presence of polymyxin caused a 23 to 31% increase in lip...

Covalently-attached fluorophores may impart enhanced chemosensing capabilities to calixarene frameworks. Synthesis and characterization of six novel dansyl-appended calix[4]arenes, namely, H/Dan4, NO2/Dan4, H/(OH)2Dan2, H/(Ester)2(Dan)2, t-Bu/(OH)2Dan2, and t-Bu/(Ester)2Dan2, containing two or four dansyl moieties are reported. Among these, fluorescence intensity of NO2/Dan4 is observed to decr...

Polymyxin B (PX) forms complexes with the O-antigenic lipopolysaccharide (LPS) of Salmo­ nella typhimurium which are stable in aqueous 0.14 M sodium chloride at neutral pH. PX can be quantitatively recovered from the complex by changing the pH from 7 to 1, or by treatment with the cationic detergent cetylpyridinium chloride. This proves that complex formation does not involve covalent linkages,...

The enzyme cystathionase from rat liver is inactivated by incubation with 5,5’-dithiobis(Z-nitrobenzoic acid) at pH 7.4. The reaction of four -SH groups per mole of enzyme brings about 95% loss of the homoserine deaminase activity. Kinetically, the reactive --SH groups can be classified into two classes. The substrate L-homoserine or the competitive inhibitor L-alanine has no effect on the rate...

A series of acyl derivatives and a dansyl derivative of the synthetic peptide Leu-Arg-Arg-Ala-Ser-Leu-Gly have been tested as substrates for the catalytic subunit of the CAMP-dependent protein kinase (ED 2.7.1.37; ATP: phosphotransferase). The purpose of this study was to test whether substitution of the NH2-terminal leucine with acyl substituents of varying chain length and hydrophobicity woul...

Receptor-mediated binding of leukocyte chemotactic peptide, N-formylMet-Leu-Phe (fMLP), occurs in the ciliated protozoon Tetrahymena thermophila. In vivo labelling of the cells with N-formylMet-Leu-[3H]Phe ([3H]fMLP) shows that the cells bind the ligand with high affinity (KD = 4 x 10(-9) M to 1 x 10(-8) M). Moreover, Scatchard transformations of the binding data show that there are about 5 x 1...

We have used fluorescence and spin-label EPR spectroscopy to investigate how the phosphorylation of phospholamban (PLB) by cAMP-dependent protein kinase (PKA) modifies structural interactions between PLB and the Ca(2+)- and Mg(2+)-dependent ATPase (Ca-ATPase) that result in enzyme activation. Following covalent modification of N-terminal residues of PLB with dansyl chloride or the spin label 4-...

Fluorescence techniques have been employed to study the interaction of porcine and equine colipase with pure taurodeoxycholate and mixed micelles. Nitrotyrosine-55 of porcine colipase is obtained by modification with tetranitromethane (low excess, in the presence of taurodeoxycholate) of the protein followed by gel filtration and ion-exchange chromatography. Verification of the residue modified...

Previous work from our laboratory [1] has established the efficient syntheses of lysine (APA-Lys)* and ornithine (APA-Orn) analogues of the folate antagonist drug methotrexate (MTX). Both analogues are potent inhibitors of dihydrofolate reductase (DHFR) , the intracellular target for MTX and other antifolate drugs. Reaction of APA-Lys and APA-Orn with dansyl chloride furnishes the corresponding...