On the construction and calculation of optimal nonlifting critical airfoils

Numerical calculations are carried out in the hodograph plane to construct optimal critical airfoil shapes and the flow about them. These optimal airfoil shapes give the highest free-stream Mach numberM for a given thickness ratio and tail angle _t (nonlifting) for which the flow is nowhere supersonic. A relationship betweenM and for various _t is given. Analytical and numerical solutions to the same problem are found on the basis of transonic small-disturbance theory. These results provide a limiting case asM 1, 0 and agree well with the calculations of the full problem. Using a numerical method to calculate the flow about general (subsonic) airfoils, a comparison is made between the critical free-stream Mach numbers for some standard airfoil shapes and the optimal free stream Mach number of the corresponding and _t . A significant increase in the critical free-stream Mach number is found for the optimal airfoils.     

Confirmation of the structure of lipid A from Enterobacter agglomerans by electrospray ionization tandem mass spectrometry

Electrospray ionization (ESI) combined with tandem mass spectrometry (MS/MS) was utilized for the structural confirmation of lipid A derived from Enterobacter agglomerans, a Gram-negative bacterium commonly found in field cotton. Previous ESI-MS studies conducted in our laboratory found that similarities exist between the fatty acid side-chains in the lipid A of E. agglomerans and that of Salmonella minnesota. It was noted that heterogeneity at the fatty acyl chain at position 3' of the diglucosamine backbone of E. agglomerans can take the form of either a myristyloxymyristyl group or, less commonly, a hydroxymyristyloxymyristyl moiety. In this work, tandem mass spectra obtained from heptaacyl and hexaacyl lipid A precursors derived from E. agglomerans and a known standard S. minnesota were compared to assist in structural elucidation. These ESI-MS/MS experiments confirmed the previously reported structure for lipid A derived from E. agglomerans. Moreover, MS/MS data indicated that the additional hydroxyl group of the 3'-position hydroxymyristyloxymyristyl moiety is present as the alpha-isomer.     

Determination of thiols by titrimetric and chromatographic procedures based on reactions with aromatic thiosulfonates

Semimicro titrimetric procedures and micro high-performance liquid chromatographic procedures are described for the determination of aliphatic and aromatic thiols, based on the highly selective reaction with aromatic thiosulfonates. The reaction products, a sulfinic acid and a mixed disulfide, contain an aromatic moiety, permitting the use of an u.v. detector. The chromatographic procedure offers the advantages of application to mixtures, coupled with cross-checking of the determination by material balance from simultaneous measurement of the two reaction products.     

Protein tyrosine kinase Csk-catalyzed phosphorylation of Src containing unnatural tyrosine analogues

Using expressed protein ligation, five unnatural tyrosine analogues (amino-phenylalanine, homotyrosine, 2-methyl-tyrosine, (alphaS,betaR)-beta-methyl-tyrosine, and 2,6-difluoro-tyrosine) were incorporated into Src in place of the natural tail tyrosine residue. These semisynthetic substrates were evaluated as Csk substrates or allosteric activators. It appears that the tyrosine phenol hydroxyl is unlikely to be contributing significantly to Src's ground-state binding affinity for Csk. It has been observed that stabilizing tyrosine conformers can further optimize Src's already high substrate efficiency. These latter findings contrast similar studies with synthetic peptide substrates and highlight the value of investigation of protein kinase substrate selectivity with protein substrates.     

Preparative electrochromatography of proteins in various types of porous media

The performance of commercial and enzymatically modified size-exclusion (SE) gels in electrochromatography was compared for preparative protein separations. Dextran and agarose-based SE gels were subjected to enzymatic digestion under mild conditions. This treatment partially hydrolyzed the gel matrix modifying its pore size distribution. Enzymatic treatment of agarose-based SE gels was found to increase the resolution of the separation. Successful separation of preparative amounts of the A and B forms of beta-lactoglobulin (difference in electrophoretic mobility of 8.5%) was achieved with a high degree of purity using agarose-based SE gels. The four major whey proteins, beta-lactoglobulin, alpha-lactalbumin, BSA and immunoglobulins, were purified from an acid whey preparation. The degree of retention of a protein in electrochromatography followed their free-solution electrophoretic mobility (mu) when the protein was able to enter the gel pores and the ratio of diffusion/mu when the protein was excluded.