Protein modification in nonaqueous media. Preparation and properties of matrix-supported lysozyme

Hen's egg white lysozyme (EC 3.2.1.17) has been covalently attached to a polystyrene matrix via interaction of protein nucleophiles with an aromatic imidazolide function under anhydrous conditions. The polymer-enzyme complex is prepared in a way which allows nonaqueous solubilization of the complex. The activity of the bound enzyme compares favorably with the activity of the native protein. The pH optima for the matrix-supported protein are shifted toward the basic side. The effect of substrate concentration on rate has been determined. (A preliminary report of this work has been published: G. J. Bartling, H. D. Brown, S. K. Chattopadhyay, Nature 243 , 342–344 (1973).)     

A convenient synthesis of (2R,8R)-8-methyl-2-decanol and its 2S epimer,the parent alcohols of rootworm pheromones

A highly stereospecific synthesis of the title compound (2R,8R)-8-methyl-2-decanol (I) has been devised via 16 simple steps. The required chirons (5 and 11) were prepared from easily accessible templates viz. (R)-methyl citronel-late and (S)-glutamic acid. This on Grignard coupling furnished the ketal (12) which was converted to the desired epoxide (14) and subsequently reduced to furnish the alcohol (2R,8R)-I. Its corresponding (2S)-epimer was prepared by total stereoselective inversion of its C-2 center. The title compounds are the parent alcohols of the pheromone components of the female rootworms.     

Absorption,Translocation and Adhering Capacities of Mycobacillin and Versicolin in Rice Plant Tissue

Mycobacillin adheres to the surface of seed or seedling but is not absorbed by rice plant tissue, whereas versicolin not only adheres to the surface but is also absorbed and subsequently translocated. The antibiotic re-extracted from the versicolin-treated plant tissue inhibits the growth of Helminthosporium oryzae. Thus mycobacillin is active only topically, while versicolin both topically and systemically.     

Ouabain inhibition of kidney ATPase is altered by 9.14 GHz radiation.

At each of several stabilized temperatures between 7.0 and 43.8 degrees C, increases in dog-kidney, Na(+)-, K(+)-ATPase catalytic activity were usually observed in association with exposure for 5 min to 9.14 GHz CW microwave radiation in a thin tubular reactor. However, at 24.9 degrees C, a 23% decrease occurred. Comparisons of activity of ouabain-inhibited reactions revealed that the efficacy of the cardiac glycoside as an inhibitor of ATPase activity was severely diminished by the microwave field. The ouabain-site control mechanism may be a specific microwave target at this exposure frequency. Experimental results can be interpreted in terms of molecular structural changes or direct energy input. The estimated SAR of energy that was incident on preparations is 20 W/kg.     

Conformational plasticity and dynamic interactions of the N-terminal domain of the chemokine receptor CXCR1

The dynamic interactions between G protein-coupled receptors (GPCRs) and their cognate protein partners are central to several cell signaling pathways. For example, the association of CXC chemokine receptor 1 (CXCR1) with its cognate chemokine, interleukin-8 (IL8 or CXCL8) initiates pathways leading to neutrophil-mediated immune responses. The N-terminal domain of chemokine receptors confers ligand selectivity, but unfortunately the conformational dynamics of this intrinsically disordered region remains unresolved. In this work, we have explored the interaction of CXCR1 with IL8 by microsecond time scale coarse-grain simulations, complemented by atomistic models and NMR chemical shift predictions. We show that the conformational plasticity of the apo-receptor N-terminal domain is restricted upon ligand binding, driving it to an open C-shaped conformation. Importantly, we corroborated the dynamic complex sampled in our simulations against chemical shift perturbations reported by previous NMR studies and show that the trends are similar. Our results indicate that chemical shift perturbation is often not a reporter of residue contacts in such dynamic associations. We believe our results represent a step forward in devising a strategy to understand intrinsically disordered regions in GPCRs and how they acquire functionally important conformational ensembles in dynamic protein-protein interfaces.