The ribosomal proteins S4 and S9 were isolated from the 30S ribosomal subunit of Escherichia coli to greater than 95% purity and characterized in the reconstitution buffer. Neither of the proteins indicated any tendency to self associate at 3 degrees C in the concentration range studied. At higher temperatures (greater than 20 degrees C), protein S9 forms a significant amount of a soluble aggregate as seen from the sedimentation velocity and sedimentation equilibrium experiments. From an analysis of the solution mixture of S4 and S9 at 1:1.08 molar concentration ratio by sedimentation velocity experiment, an s20,w value of 1.77 +/- 0.02S was obtained. A fast moving component which accounts for approximately 20% of the mass was also observed. Increasing the concentration of S9 does not alter the observed s20w value significantly for that component which could be followed. A detailed analysis of the data obtained at 3 degrees C from sedimentation equilibrium experiments on mixtures of the proteins indicated that a species of molecular weight greater than either of the two proteins was present. The proteins were found to interact with a mean equilibrium constant of association of 3.66 +/- 2.39 x 10(4) M-1 and a Gibbs free energy of interaction, delta Go = -5.8 kcal/mole at 3 degrees C in TMKD buffer. This information helps in understanding the energetics of the 30S ribosomal subunits of E. coli.

Escherichia coli↗

PubMedDate not supplied

Interactions of methoxyamine with pyridoxal-5'-phosphate-Schiff's base at the active site of sheep liver serine hydroxymethyltransferase.

The mechanism of interaction of methoxyamine with sheep liver serine hydroxymethyltransferase (EC 2.1.2.1) (SHMT) was established by measuring changes in enzyme activity, visible absorption spectra, circular dichroism and fluorescence, and by evaluating the rate constant by stopped-flow spectrophotometry. Methoxyamine can be considered as the smallest substituted aminooxy derivative of hydroxylamine. It was a reversible noncompetitive inhibitor (Ki = 25 microM) of SHMT similar to O-amino-D-serine. Like in the interaction of O-amino-D-serine and aminooxyacetic acid, the first step in the reaction was very fast. This was evident by the rapid disappearance of the enzyme-Schiff base absorbance at 425 nm with a rate constant of 1.3 x 10(3) M-1 sec-1 and CD intensity at 430 nm. Concomitantly, there was an increase in absorbance at 388 nm (intermediate I). The next step in the reaction was the unimolecular conversion (1.1 x 10(-3) sec-1) of this intermediate to the final oxime absorbing at 325 nm. The identity of the oxime was established by its characteristic fluorescence emission at 460 nm when excited at 360 nm and by high performance liquid chromatography. These results highlight the specificity in interactions of aminooxy compounds with sheep liver serine hydroxymethyltransferase and that the carboxyl group of the inhibitors enhances the rate of the initial interaction with the enzyme.

Animals↗

PubMedDate not supplied

Indian Medical Association. Third World Conference on Medical Education. India 1966.

Explore the source record for details and available documents.

Education, Medical↗

PubMedDate not supplied

Endoscopic sphincterotomy for common bile duct stones with and without gall bladder/'T' tube 'in situ'.

Eighty-seven patients underwent endoscopic sphincterotomy (ES) for common bile duct (CBD) stones. Out of these, 66 patients had post-cholecystectomy CBD stones and 21 had CBD stones with gall bladder 'in situ'. In post-cholecystectomy group, 15 patients had 'T' Tube 'in situ'. The presenting symptoms in the post-cholecystectomy group were: pain abdomen, jaundice and cholangitis in 51, 20 and 11 patients respectively. The fifteen patients with 'T' tube used to experience pain after clamping of 'T' tube. Those with gall bladder 'in situ' had cholangitis in 12 and jaundice only in 9 patients. CBD clearance was achieved in 80 patients (91.95%). The sphincterotomy cut had to be extended in 19 patients. There was no mortality following sphincterotomy. Nine patients (10.3%) had minor complications such as bleeding (4), cholangitis (3), pancreatitis and impaction of Dormia basket in one patient each. Thus ES is a safe and effective treatment for CBD stones with or without gall bladder/'T' tube 'in situ'.

Adult↗