Resonance Raman Spectroscopy Reveals pH-Dependent Active Site Structural Changes of Lactoperoxidase Compound 0 and Its Ferryl Heme O–O Bond Cleavage Products

The first step in the enzymatic cycle of mammalian peroxidases, including lactoperoxidase (LPO), is binding of hydrogen peroxide to the ferric resting state to form a ferric-hydroperoxo intermediate designated as Compound 0, the residual proton temporarily associating with the distal pocket His109 residue. Upon delivery of this “stored” proton to the hydroperoxo fragment, it rapidly undergoes O–O bond cleavage, thereby thwarting efforts to trap it using rapid mixing methods. Fortunately, as shown herein, both the peroxo and the hydroperoxo (Compound 0) forms of LPO can be trapped by cryoradiolysis, with acquisition of their resonance Raman (rR) spectra now permitting structural characterization of their key Fe–O–O fragments. Studies were conducted under both acidic and alkaline conditions, revealing pH-dependent differences in relative populations of these intermediates. Furthermore, upon annealing, the low pH samples convert to two forms of a ferryl heme O–O bond-cleavage product, whose ν(Fe═O) frequencies reflect substantially different Fe═O bond strengths. In the process of conducting these studies, rR structural characterization of the dioxygen adduct of LPO, commonly called Compound III, has also been completed, demonstrating a substantial difference in the strengths of the Fe–O linkage of the Fe–O–O fragment under acidic and alkaline conditions, an effect most reasonably attributed to a corresponding weakening of the trans-axial histidyl imidazole linkage at lower pH. Collectively, these new results provide important insight into the impact of pH on the disposition of the key Fe–O–O and Fe═O fragments of intermediates that arise in the enzymatic cycles of LPO, other mammalian peroxidases, and related proteins

Application uniformity of low pressure center pivot equipment

Center pivot and lateral move irrigation systems consist of a continously moving lateral with sprinklers mounted at an equal or variable spacing. The discharge rate on a center pivot increases linearly from the pivot, and can be as high as 1.5 gallons per minute (gpm) per foot of lateral near the outer end of a 1/4 mile lateral. Due to the high discharge rate, and nozzle size limitations, which typically limit nozzle spacings to 5 to 15 feet, uniformity of application is usually quite high

Cablegation V: Dimensionless Design Relationships

A simplified design method using dimensionless relationships was developed for the cablegation automated surface irrigation system. The method consists of two parts: the pipe flow distribution and the infiltration-runoff distribution. The maximum outlet head, maximum stream size and number of flowing outlets are calculated using a set of dimensionless equations, given the pipe size, pipe slope, outlet size and spacing and total inflow rate. These equations enable a direct determination of the design variables without calculating the entire distribution of outlet flows. If the desired maximum stream size is known, the required outlet size can be calculated directly without trial and error. The infiltration-runoff analysis is presented as a series of dimensionless relationships in graphical form. These curves are used mainly for determining the required maximum stream size given a time-based furrow intake curve, furrow length and spacing, gross water application and percent runoff. Curves are also presented for the case of constant stream size for comparison with cablegation and for use in designing constant-inflow irrigation systems

Sprinkler nozzle options offer choices for growers

Farmers today have a wide range of sprinkler-nozzle combinations from which to choose. The primary consideration in sprinkler system design is to obtain high water application uniformity. Another important consideration is to control droplet sizes to minimize droplet impact on the soil. while minimizing spray drift and evaporation

Reducing Energy Requirements for Sprinkler Systems

According to the 1980 Irrigation Journal Survey, sprinkler irrigation is practiced on approximately 4.1 million acres in Washington, Idaho and Oregon. Of that total, approximately 75 percent is irrigated by hand move, side roll and solid set systems. Much of this land is on rolling hills with fairly shallow soils and is unsuitable for surface irrigation. The soils are mostly medium- to low-intake rate soils which are less than optimum for center pivot application. For these reasons, farmers in the Pacific Northwest will continue using stationary lateral systems despite rising energy costs. Power rates in Idaho are expected to increase approximately 15 percent per year. High levels of application uniformity are easily obtainable with center pivot systems. However, stationary system uniformities are generally lower and may be reduced to unacceptable levels as farmers attempt to reduce power costs by lowering system pressure. The objective of this study was to determine whether pressure could be reduced on existing systems without making major changes in sprinkler spacing. Two types of outdoor grid tests were conducted to measure uniformity. The first type was standard single sprinkler patterns (SSP) as described in ASAE S-330. The second type was lateral sprinkler patterns as described by Hart and Heermann (1976). The lateral tests will be described first

Sprinkler pattern analysis for center pivot irrigation

Users of center pivot and lateral move irrigation systems now have a wide array of sprinkler packages from which to choose, including the traditional overhead impact sprinklers, various types of spray heads and the LEPA-type furrow emitters. The original spray heads used simple, smooth or serrated fixed deflection plates. Recently, rotating plate or wobble-plate spray heads have been developed, combining the advantages of spray heads and rotating sprinklers — medium-size pattern radius, good pattern shape and medium-size droplets at medium to low pressures (10 to 30 psi)

Sprinkler Pattern Radius

A mathematical relationship describing the combined effects of nozzle size, pressure and nozzle discharge on sprinkler pattern radius was proposed and evaluated. The nozzle jet momentum flux was found to be a significant factor in determining pattern radius. A power function is used to relate the momentum parameter to pattern radius. The relationship was evaluated by the use of manufacturers' catalog data and laboratory pattern test data collected at Kimberly, ID. The relationship can be used in computer simulation of sprinkler systems to predict variations in pattern radius with pressure variations due to topography and/or friction losses. The method can also be used to compare the performance of different sprinklers or nozzles and to determine the effect of variables such as nozzle height or jet angle on pattern radius

Prazosin + Naltrexone Decreases Alcohol Drinking More Effectively Than Does Either Drug Alone in P Rats with a Protracted History of Extensive Voluntary Alcohol Drinking, Dependence, and Multiple Withdrawals

Background Prazosin (PRZ, an α1-adrenergic receptor antagonist) and naltrexone (NTX, a non-specific opioid receptor antagonist) each decrease alcohol drinking when administered to rats selectively-bred for high voluntary alcohol drinking (alcohol-preferring, or “P”), and the combination of PRZ+NTX decreases alcohol drinking more effectively than does either drug alone. Since drug responsiveness can depend on history of alcohol drinking and dependence, we investigated whether various schedules of PRZ and NTX administration, alone or in combination, are effective in decreasing alcohol drinking in male P rats with a history of protracted voluntary alcohol drinking, dependence and repeated withdrawals closely resembling human alcoholism. Methods Male P rats became alcohol-dependent during 1 year of ad libitum 24 h/day access to food, water and 20% alcohol with repetitive temporary alcohol withdrawals. Four sequential studies then addressed effects of oral PRZ (2 mg/kg) and NTX (10 mg/kg), alone or together, on alcohol drinking during: 1) daily alcohol access with daily drug treatment, 2) intermittent alcohol access with daily drug treatment, 3) intermittent alcohol access with occasional drug treatment, and 4) post-deprivation reinstatement of alcohol access. Results The combination of PRZ+NTX consistently suppressed alcohol drinking during daily or intermittent alcohol access conditions and when drug treatment was either daily or occasional. PRZ+NTX was consistently more effective than either drug alone. The reduction in alcohol drinking was not due to sedation, motor effects or malaise. Conclusions Both daily and “as-needed” treatment with PRZ+NTX are highly effective in suppressing daily, intermittent and post-deprivation alcohol drinking in male P rats with a protracted history of alcohol dependence and repeated withdrawals. This drug combination may be especially effective for treating individuals with long histories of heavy alcohol abuse, dependence and repeated relapse, as commonly encountered in clinical practice

Doming Modes and Dynamics of Model Heme Compounds

Synchrotron far-IR spectroscopy and density-functional calculations are used to characterize the low-frequency dynamics of model heme FeCO compounds. The “doming” vibrational mode in which the iron atom moves out of the porphyrin plane while the periphery of this ring moves in the opposite direction determines the reactivity of oxygen with this type of molecule in biological systems. Calculations of frequencies and absorption intensities and the measured pressure dependence of vibrational modes in the model compounds are used to identify the doming and related normal modes

Cablegation IV: The Bypass Method and Cutoff Outlets to Improve Water Distribution

TWO techniques of improving the water distribution characteristics of cablegation systems are proposed and evaluated. The bypass method, which largely eliminates the problem of end effects, involves starting the plug at the first outlet and initially bypassing most of the flow to the downstream end of the pipeline, which is plugged. As the plug moves down the pipe, the bypass flow gradually decreases to zero. This method nearly equalizes the inflow distribution to all furrows and allows the use of a constant outlet opening size. The bypass can be accomplished by using a parallel bypass pipe and weir, or with a flow-through bypass plug. The bypass plug appears to be the lower cost method and is as effective as the weir in controlling the bypass. The second technique deals with the low outlet flows during the final stages of a "set" which are insufficient to reach the end of the furrows such that excess water is applied to the upper ends of the furrows. Two types of cutoff outlets, a gravity valve and a siphon type outlet were designed to abruptly cut off the flow at about the same time that runoff ceases, thus maximizing the uniformity of infiltration. The cutoff outlets are recommended for soils having relatively high sustained intake rates