Substrate Distortion in Lysozyme-Substrate Interactions

The evidence supporting the hypothesis that substrate distortion towards the transition-state conformation in the lysozyme catalysed hydrolysis of glycosides makes an important contribution towards the rate enhancement observed for the enzymic hydrolysis is reviewed in the light of the currently held views on the mechanism of action of lysozyme and the known interactions of the enzyme with substrates and inhibitors. A series of oligosaccharides having the general structure (NAG)r-X, where n= 1-3, NAG= N-acetyl-D-glucosamine and X= an aryl glycoside were prepared. When X is an aryl glycoside of N-acetyl-D-xylosamine the effect of substrate distortion in the lysosyme catalysed hydrolysis should be eliminated. Therefore by comparison with other oligosaccharides for which substrate distortion could play a role in the enzymic hydrolysis, an estimation of this factor could be made. p-Nitrophenyl 2-acetamido-2-deoxy-beta-D-xylopyranoside was shown by N. M. R. to exhibit a dissociation constant and bound chemical shift value on association with lysozyme consistent with the sugar residue being bound in subsite C of the active cleft. This is in accord with the results obtained for the binding of other monosaccharide inhibitors having a 2-acetamido group, Nacetyl-D-glucosamine, methyl 2-acetamido-2-deoxy-alpha-D-gLucopyrano-side and p-nitrophenyl 2-acetamido-2-deoxy-beta-D-glucopyranoside, confirming the strong interaction of the 2-acetamido group at subsite C. NAG-NAX-PNP was shown by N. M. R. to bind to lysozyme with the sugar residue proximal to the aglycone occupying subsite C of the active cleft, predicting that the compound binds to a considerable extent in the binding mode B, C. This binding mode was shown by N. M. R. to be present in the binding of NAG2, p-nitrophenyl beta-NAG2 and NAG-Glu-PNP to lysozyme. Within experimental error the same dissociation constant for the binding of NAG-NAX-PNP was obtained from fluorescence and inhibition studies. This compound was shown to bind more strongly to lysozyme than either NAG2 or p-nitrophenyl beta-NAG2 with a favourable energy difference of approximately 1Kcal/mole. Similarly from fluorescence and inhibition studies NAG2-NAX-PNP was shown to bind more strongly to lysozyme than either NAG3 or p-nitrophenyl beta-NAG3 by about 1Kcal/mole. The kinetics of the lysozyme catalysed hydrolysis of p-nitrophenyl beta-NAX, NAG-NAX-PNP, NAG2-NAX-PNP and NAG3-NAX-PNP were studied and compared with the lysozyme catalysed hydrolysis of the corresponding NAG glycosides. The rate of hydrolysis of the NAX compounds was found to be considerably slower than that of the NAG compounds. The upper limit of kcat /Km (apparent) found for the lysozyme catalysed hydrolysis of NAG3-NAX-PNP was 1,000 times less than kcat /km (apparent) found for p-nitrophenyl beta-NAG4 consistent with the hypothesis that substrate distortion is important in the lysozyme catalysed hydrolysis of glycosides. 3,4-dinitrophenyl beta-NAX, NAG-NAX-DNP and NAG2-NAX-DNP did not show any increase in the rate of hydrolysis in the presence of lysozyme over that found for the spontaneous hydrolysis, confirming the role of substrate distortion in the enzymic catalysis. The account that must be taken of the binding modes and strength of binding observed for the lower NAX containing oligosaccharides in the interpretation of the kinetic results is discussed. NAG-NAX-PNP, NAG2-NAX-PNP and NAG-Glu-PNP were shown to be competitive inhibitors of the lysozyme catalysed hydrolysis of 3,4-dinitro-phenyl beta-NAG4. The inhibition constant found for NAG-Glu-PNP differed from the dissociation constant for this compound found by N. M. R. The reasons for this difference are discussed in relation to the possible binding, modes available for this compound and the ability of the N. M. R. method to distinguish between different binding modes. p-Nitrophenyl 2-deoxy-beta-D-glucopyranoside was synthesized and fully characterised. Attempted transglycosylation reactions of this compound with lysozyme are discussed

Problems encountered in the wholesaling of raw wool, and the wholesale wool market of Boston.

Thesis (M.B.A.)--Boston Universit

To the Members of the Graduating Class

Commencement address given by William McPherson, President of The Ohio State University, to the Spring 1939 graduating class of The Ohio State University, Ohio Stadium, Columbus, Ohio, June 12, 1939

AN ECONOMIC EVALUATION OF SOYBEAN STINK BUG CONTROL ALTERNATIVES FOR THE SOUTHEASTERN UNITED STATES

Methyl parathion or Penncap M (an encapsulated methyl parathion) are used extensively throughout the United States for controlling stink bug pests in soybeans, Glycine Max (L.) Merrill. However, this insecticide is highly toxic to mammals, birds, and non-target arthropods, and thus is less environmentally sound than other insecticides. For environmental and human health considerations, investigating alternative insecticides for control is desired. For this investigation, research based on field experimental data from Florida, Georgia, and Louisiana during the 1988 and 1989 growing seasons were employed. Results indicate that alternative, currently available, and less toxic insecticides may reduce producer costs, increase yield, and improve soybean quality. These alternative insecticides include Scout (tralomethrin), Karate (lambda-cyhalothrin), Orthene (acephate), and Baythroid (cyfluthrin). In terms of improved profits these alternative insecticides may dominate methyl parathion or encapsulated methyl parathion.Crop Production/Industries,

Assessing the Relative Perspective of the Regulation of Kinesiologists Among Other Health Professionals

Formerly a self-governed profession, in the Province of Ontario, Canada, kinesiology was designated a regulated profession under the Regulated Health Professions Act (1991). The purpose of this study was to evaluate the perceptions of current health delivery agents to the regulation of kinesiology. An 18-item survey was used to collect data, and a SWOT (strengths, weaknesses, opportunities and threats) framework was used for analysis. The data indicated that kinesiology provides a unique expertise adding to client and patient care and is a needed partner within the multidisciplinary health environment. Similarly, despite the need for the profession to clearly define, delineate, and promote its scope of practice to professionals and to the public, there are increased opportunities that exist within the health care sector, particularly in chronic disease prevention. The addition of kinesiology as a regulated health profession was not considered to be a threat by existing key stakeholders

A climatological analysis of heatbursts in Oklahoma (1994–2009)

Heatbursts are characterized by a sudden and highly localized increase in air temperature, a simultaneous decrease in relative humidity and dewpoint temperature, and strong gusty winds, typically associated with decaying thunderstorms. The small spatial extent and short duration of most heatbursts makes detailed study of these events difficult using the standard federal observation network (e.g. hourly observations) established in most countries. Thus, many discussions of heatbursts note that they are ‘rare’ phenomena. However, observations from the Oklahoma Mesonet indicate that although heatbursts are meso-alpha scale phenomena, they are not rare. Using multi-criteria analysis, 207 heatburst events of various magnitudes, areal coverage and duration were identified between 1994 and 2009 across Oklahoma. Significantly more heatbursts were detected in the western two-thirds of the state as compared to the eastern third. Heatbursts were primarily nocturnal events, with 70% of heatburst events initiated between 0000 and 0800 UTC (i.e. between 6 p.m. and 2 a.m. Central Standard Time). With 62 of the 207 events, June was the most active month for heatbursts. At the other extreme, no heatbursts were detected during February and November, and only one was observed during January and December. Almost all of the heatbursts occurred underneath or adjacent to weak radar echoes at the time of the event. Four basic radar patterns were associated with the events: (1) radar echoes associated with rapidly weakening convection, (2) weak reflectivity not produced by or associated with deep moist convection, (3) weak radar echoes to the rear of a dissipating mesoscale convective system (MCS) and (4) weak reflectivity along the periphery of intense convection that did not appear to be weakening