Structure-function relations in phosphorylcholine-binding mouse myeloma proteins

The binding site interactions between the phosphorylcholine (phosphocholine)-binding mouse myeloma proteins TEPC 15, W3207, McPC 603, MOPC 167, and MOPC 511 and the isotopically substituted hapten phosphoryl-[methyl-13C]choline have been investigated using 13C and 31P nuclear magnetic resonance (NMR) spectroscopy. Each protein exhibits a unique NMR pattern, but extensive similarities in chemical shift parameters upon binding of hapten to immunoglobulin suggest a significant degree of conservation of important hapten-binding site interactions. Moreover, independent binding studies, in conjunction with the NMR data, allow construction of a simple model of the binding sites of these antibodies, analyzed in terms of the relative strength of interaction between hapten and two main subsites. The NMR evidence supports the view that the heavy chains of these proteins dominate in interacting with bound phosphorylcholine; the various subspecificities of these proteins for phosphorylcholine analogues can be accounted for by amino acid changes in the hypervariable regions of the heavy chains

Conformational studies of various hemoglobins by natural-abundance 13C NMR spectroscopy

Studies of variously liganded hemoglobins (both from human and rabbit) by natural-abundance 13C NMR spectroscopy have revealed apparent conformational differences that have been interpreted on the basis of two quaternary structures for the α2ß2 tetramer, and variable tertiary structures for the individual α and ß subunits. In solution, rabbit hemoglobins appear to have somewhat more flexibility than human hemoglobins

Performance of low-pressure thermionic converters is evaluated

Experiments, evaluating the performance of low-pressure thermionic converters, were conducted with cesium, potassium, and sodium-metal vapors. The results of the investigation are useful in the selection of favorable conditions for the design of thermionic reactor fuel elements, including RF output for special applications

Altering Enzymatic Activity: Recruitment of Carboxypeptidase Activity into an RTEM β-Lactamase/Penicillin-Binding Protein 5 Chimera

The D-Ala-D-Ala carboxypeptidases/transpeptidases (penicillin-binding proteins, PBPs) share considerable structural homology with class A β-lactamases (EC 3.5.2.6), although these β-lactamases have no observable D-Ala-D-Ala carboxypeptidase activity. With the objective of recruiting such activity into a β-lactamase background, we have prepared a chimeric protein by inserting a 28-amino acid segment of PBP-5 of Escherichia coli in place of the corresponding region of the RTEM-1 β-lactamase. The segment thus inserted encompasses two residues conserved in both families: Ser-70, which forms the acyl-enzyme intermediate during β-lactam hydrolysis, and Lys-73, whose presence has been shown to be necessary for catalysis. This chimera involves changes of 18 residues and gives a protein that differs at 7% of the residues from the parent. Whereas RTEM β-lactamase has no D-Ala-D-Ala carboxypeptidase activity, that of the chimera is significant and is, in fact, about 1% the activity of PBP-5 on diacetyl-L-Lys-D-Ala-D-Ala; in terms of free energy of activation, the chimera stabilizes the transition state for the reaction to within about 2.7 kcal/mol of the stabilization achieved by PBP-5. Furthermore, the chimera catalyzes hydrolysis exclusively at the carboxyl-terminal amide bond which is the site of cleavage by D-Ala-D-Ala carboxypeptidase. Though containing all those residues that are conserved throughout class A β-Lactamases and are thought to be essential for β-lactamase activity, the chimera has considerably reduced activity ({approx} 10^-5) on penams such as penicillins and ampicillins as substrates. As a catalyst, the chimera shows an induction period of {approx} 30 min, reflecting a slow conformational rearrangement from an inactive precursor to the active enzyme

CASCADE INVESTIGATION OF COOLING CHARACTERISTICS OF A CORRUGATEDINSERT AIR-COOLED TURBINE BLADE FOR USE IN A TURBOPROP ENGINE

Heat transfer of air-cooled turbine blade for turboprop engin

Three-Year Creel Census of Lake Catherine, Lake Hamilton, and Lake Ouachita, Arkansas

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201

A projection method for statics and dynamics of lattice spin systems

A method based on Monte Carlo sampling of the probability flows projected onto the subspace of one or more slow variables is proposed for investigation of dynamic and static properties of lattice spin systems. We illustrate the method by applying it, with projection onto the order-parameter subspace, to the three-dimensional 3-state Potts model in equilibrium and to metastable decay in a three-dimensional 3-state kinetic Potts model.Comment: 4 pages, 3 figures, RevTex, final version to appear in Phys. Rev. Let