The kinetics of the alkylation of the essential sulfhydryl group of papain with chloroacetic acid was studied. The variation of the second order rate constant with pH at 4.5” and 30.5’, r/2 = 0.07, is bell-shaped, with rate constants at a maximum near neutrality, approaching zero at low pH, and approaching a positive minimum at high pH. These profiles are described by a formulation which relate...

We investigated the dependence of membrane binding on amino acid sequence for a series of amphipathic peptides derived from δ-lysin. δ-Lysin is a 26 amino acid, N-terminally formylated, hemolytic peptide that forms an amphipathic α-helix bound at membrane-water interfaces. A shortened peptide, lysette, was derived from δ-lysin by deletion of the four N-terminal amino acid residues. Five variant...

Equilibrium dissociation constants of Bay k 8644, a calcium agonist, and nitrendipine, a calcium antagonist, were determined in canine cardiac sarcolemma. The equilibrium dissociation constant for Bay k 8644 was compared to the concentration that produced a fifty percent increase, and the equilibrium dissociation constant for nitrendipine was compared to the concentration that produced a fifty ...

Cytosolic retinoic acid receptor in carcinoma, chronic pancreatitis, and normal pancreatic tissue were examined using sucrose density gradient centrifugation, isoelectric focussing on agarose gel and saturation analysis. Thirteen patients were studied. Cytosolic retinoic acid binding protein (cRABP) was detected in all the samples with chronic pancreatitis and pancreatic carcinoma, but not in t...

Acid dissociation in the excited state of antihypotensor drug etilefrine [2-(ethylamino1-3-hydroxyphenyl)ethanol] is studied. Fluorescence of etilefrine decreases at pHB7 and is related to phenolic group dissociation. However, intensity of etilefrine fluorescence diminishes as the concentration of the acetate anion increases at pH\7. Analyses of the absorption and fluorescence spectra of aqueou...

The rise of multi- and even totally antibiotic resistant forms of Mycobacterium tuberculosis underlines the need for new antibiotics. The pathogen is resistant to β-lactam compounds due to its native serine β-lactamase, BlaC. This resistance can be circumvented by administration of a β-lactamase inhibitor. We studied the interaction between BlaC and the inhibitor clavulanic acid. Our data show ...

The molecular weight of approximately 1,500-fold purified arginase from rat liver (specific activity = 19,500 pmoles of urea per min at 25’ per mg of protein nitrogen) was determined by the method of sedimentation equilibrium to be 118,000. The sedimentation velocity constant is 6.1 S, the diffusion coefficient 5.2 X 10U7 cm2 per sec. Alteration in pH, removal of Mn2+, and replacement of Mn2+ b...

From the analysis of the potentiometric titration data of polyelectrolytes, we can obtain the electrostatic free energy of the macromolecules. Therefore, potentiometric titration is a useful experimental procedure to study the conformation and conformational change of macromolecules. A few examples of the application of potentiometric titration to the studies on polypeptides, protein and DNA ar...

The kinetics of the reaction of d-glyceraldehyde 3-phosphate dehydrogenase with 5,5'-dithiobis-(2-nitrobenzoic acid) show that NAD(+) dissociates from the enzyme before the reaction. In contrast 2-chloromercuri-4-nitrophenol reacts with the holoenzyme without prior dissociation of NAD(+). These studies and observations on the dissociation constant of NAD(+) to the lobster enzyme show that NAD(+...

The specific interaction of a supramolecular binding motif was quantitatively evaluated by dynamic single-molecule force spectroscopy (SMFS) using an atomic force microscope (AFM). The supramolecular capsule forms by two different cavitands stitched together by four hydrogen bonds between carboxylic acid and pyridyl groups. The tetra(carboxyl)cavitand is monofunctionalized at the lower rim with...