The contribution of olfactory receptor neurons to the perception of pheromone component ratios in male redbanded leafroller moths

Summary (Z)-11-tetradecenyl acetate (Z-11, 14:AC) must be in a 1009 ratio with (E)-11-tetradecenyl acetate (E-11,14:AC) to produce maximal wing fanning and attraction in male redbanded leafrollers. Earlier electrophysiological studies had indicated that mixtures of these pheromone components elicited responses from olfactory receptor neurons that appeared to differ from those expected on the basis of the responses to the individual components. Here we evaluate whether the behavioral sensitivity to particular ratios of Z- and E-11,14:AC has a correlate in the response properties of olfactory receptor neurons.The stimuli included the ratios of Z- and E-11, 14:AC used in earlier behavioral work plus several different mixtures of the seven components found in the pheromone blend, and equivalent amounts of the individual components. These stimuli were presented over a range of intensities to individual trichoid sensilla on the male antenna. In common with earlier results, the receptor neuron with the larger amplitude action potential responded most strongly to Z-11,14:AC, whereas the companion receptor neuron in the sensillum responded most strongly to E-11,14:AC. In contrast with earlier results, each receptor neuron responded exclusively to its own most effective stimulus, without regard to the presence of any other compound. They failed to respond uniquely to any of the other five compounds in the female pheromone blend, or to any of the tested combinations of these compounds. These minor components also failed to modulate the responses elicited in receptor neurons by appropriate ratios of Z- and E-11,14:AC. Thus, the responses of the two types of olfactory receptor neurons found in trichoid sensilla failed to show an optimum at the pheromone ratio known to elicit peak behavioral activity.Abbreviation RBLR redbanded leafroller moth     

Evolutionary divergence of enterobacterial genes coding for the glucose phosphotransferase system components

Abstract The DNA relatedness of 64 enterobacterial species to Escherichia coli genes pts I, pts H, crr , pts G, and pts LPM, was determined by quantitative filter hybridization. DNA relatedness was expressed relative to E. coli K-12 DNA. Enterobacterial DNAs were 0 to 100% related to E. coli genes and the level of relatedness (except for crr data) reflected the known taxonomic (phylogenetic) position of species with respect to E. coli . When pts I relatedness data were plotted against pts H data, correlation was excellent. In pts G versus pts LPM plots, the data points (species) were scattered along the diagonal with a large gap separating E. coli strains (80–100% relatedness to both probes) from the 63 other species (1 to 40% relatedness to E. coli genes). Serratia (9 species), Buttiauxella agrestis , and Klebsiella planticola gave higher relatedness values with crr probe than with the other probes tested.     

Activity and operational stability of immobilized mandelonitrile lyase in methanol/water mixtures

Summary The enzyme mandelonitrile lyase was covalently immobilized on solid support materials using different methods. Immobilization on porous silica using coupling with glutaraldehyde afforded preparations with high enzyme loading (up to 9% (w/w)). The immobilized enzyme was used in a packed bed reactor for the continuous production of d-mandelonitrile from benzaldehyde and cyanide. The influence of the flow rate, pH, substrate concentrations and enzyme loading on the reaction yield and the enantiomeric purity of the product was investigated. In order to suppress the competing spontaneous reaction, the enzymatic reaction must be rapid. A flow rate of 9.5 ml/min (0.1 M benzaldehyde and 0.3 M HCN) through a 3 ml reactor afforded a 86% yield of mandelonitrile with 92% enantiomeric excess. No leakage of enzyme occurred under continuous operation. One column was used continuously for 200 h without any decrease in yield or enantiomeric purity of the product. High concentrations of benzoic acid were shown to decrease the operational stability of the system.     

Cross-Homologies and Structural Differences Between Human Cholinesterases Revealed by Antibodies Against cDNA-Produced Human Butyrylcholinesterase Peptides

To study the polymorphism of human cholinesterases (ChEs) at the levels of primary sequence and three-dimensional structure, a fragment of human butyrylcholinesterase (BuChE) cDNA was subcloned into the pEX bacterial expression vector and its polypeptide product analyzed. Immunoblot analysis revealed that the clone-produced BuChE peptides interact specifically with antibodies against human and Torpedo acetylcholinesterase (AChE). Rabbit polyclonal antibodies prepared against the purified clone-produced BuChE polypeptides interacted in immunoblots with denatured serum BuChE as well as with purified and denatured erythrocyte AChE. In contrast, native BuChE tetramers from human serum, but not AChE dimers from erythrocytes, interacted with these antibodies in solution to produce antibody-enzyme complexes that could be precipitated by second antibodies and that sedimented faster than the native enzyme in sucrose gradient centrifugation. Furthermore, both AChE and BuChE dimers from muscle extracts, but not BuChE tetramers from muscle, interacted with these antibodies. To reveal further whether the anti-cloned BuChE antibodies would interact in situ with ChEs in the neuromuscular junction, bundles of muscle fibers were microscopically dissected from the region in fetal human diaphragm that is innervated by the phrenic nerve. Muscle fibers incubated with the antibodies and with 125I-Protein A were subjected to emulsion autoradiography, followed by cytochemical ChE staining. The anti-cloned BuChE antibodies, as well as anti-Torpedo AChE antibodies, created patches of silver grains in the muscle endplate region stained for ChE, under conditions where control sera did not. These findings demonstrate that the various forms of human AChE and BuChE in blood and in neuromuscular junctions share sequence homologies, but also display structural differences between distinct molecular forms within particular tissues, as well as between similarly sedimenting molecular forms from different tissues.     

Gelsolin has three actin-binding sites

Gelsolin, a Ca2+-modulated actin filament-capping and -severing protein, complexes with two actin monomers. Studies designed to localize binding sites on proteolytic fragments identify three distinct actin-binding peptides. 14NT, a 14-kD fragment that contains the NH2 terminal, will depolymerize F-actin. This peptide forms a 1:1 complex with G-actin which blocks the exchange of etheno-ATP from bound actin. The estimated association and dissociation rates for this complex are 0.3 microM-1 s-1 and 1.35 x 10(-6) s-1 which gives a maximum calculated Kd = 4.5 x 10(-12) M. 26NT, the adjacent peptide on the NH2-terminal half of gelsolin, binds to both G- and F-actin. This fragment has little or no intrinsic severing activity and will bind to F-actin to nearly stoichiometric ratios. The interactions of 14NT and 26NT with actin are largely Ca2+ independent and one of these sites, probably 14NT, is the EGTA-stable site identified in the intact protein. 41CT, the COOH-terminal half of gelsolin, forms a rapidly reversible 1:1 complex with actin, Kd = 25 nM, that slows but does not block etheno-ATP exchange. This interaction is Ca2+ dependent and is the exchangeable site in the intact protein. One of these sites is hidden in the intact protein, but cleavage into half fragments exposes all three and removes the Ca2+ dependence of severing.     

Comparison of diaphragmatic fatigue in newborn and older rabbits

The ability to maintain occlusion pressure (i.e., fatigability) during activation of the diaphragm via phrenic nerve stimulation was compared in newborn (less than 14 days old) and older (greater than 30 days old) rabbits. The younger animals had lower maximum inspiratory pressures (MIP) and markedly greater falls in pressure during sustained diaphragmatic contractions at greater than 40% MIP than did the older animals. Histological analysis showed a paucity of high-oxidative type I fibers in the diaphragms of the young animals. We therefore conclude that the newborn rabbit diaphragm is extremely susceptible to fatigue and that this susceptibility correlates with the distribution of muscle fiber types.     

A group contribution method for the estimation of equilibrium constants for biochemical reactions

Using Gibbs Energies of compounds, as well as Gibbs Energy changes and equilibrium constants of biochemical reactions, the contributions of functional groups to the Gibbs Energy (in aqueous solution, temperature 25°C, and pH=7) have been estimated. These contributions allow the estimation of the Gibbs Free Energy and the equilibrium constant of a biochemical reaction, given the structure of the reactants and products.