Runoff phosphorus loss immediately after poultry manure application as influenced by the application rate and tillage.

Excessive or N-based application of poultry manure for crops may result in significant risk of P loss with surface runoff. This study assessed P loss immediately after poultry manure application to soybean [Glycine max (L.) Merr.] residue with and without tillage at eight Iowa fields. Manure from chickens (Gallus gallus domesticus) or turkeys (Melleagris gollopavo) was applied at intended rates of 0, 84, or 168 kg total N ha(-1) (total P was 0, 21-63, 50-123 kg P ha(-1), respectively) with three replications. Simulated rainfall (76 mm h(-1)) was applied to 3-m2 sections of larger field plots with 2 to 7% slope, usually within 2 d of application, to collect runoff during 30 min. Runoff was analyzed for concentrations of sediment, dissolved reactive P (DRPC), bioavailable P (BAPC), and total P (TPRC). Non-incorporated manure consistently increased (P < or = 0.10) concentrations of all runoff P fractions in five sites, but there were increasing trends at all sites, and on average manure increased DRPC, BAPC, and TPRC 32, 23, and 12 times, respectively, over the control. Tillage to incorporate manure reduced DRPC, BAPC, and TPRC by 88, 89, and 77% on average, respectively, although in non-manured plots tillage seldom affected DRPC or BAPC and often increased TPRC. Tillage increased sediment concentration in runoff but not enough to offset the benefits of manure P incorporation. Runoff P loads generally followed trends of runoff P concentrations but were more variable, and significant treatment effects were less frequent. Overall, incorporation of manure by tillage was very effective at reducing P loss during runoff events shortly after poultry manure application under the conditions of this study.

Role of glycosylation and membrane environment in nicotinic acetylcholine receptor stability.

The effects of glycosylation and membrane environment on the structural stability of the nicotinic acetylcholine receptor (nAChR) from Torpedo have been investigated to improve our understanding of factors that influence eukaryotic membrane protein crystallization. Gel shift assays and carbohydrate-specific staining show that the deglycosylation enzyme, Endo F1, removes at least 50% of membrane-reconstituted nAChR glycosylation. The extent of deglycosylation with Endo F1 increases upon detergent solubilization. Removal of between 60-100% of high mannose moieties from the nAChR has no effect on nAChR secondary structure, stability, or flexibility. Deglycosylation does not influence either agonist binding or the ability of the nAChR to undergo agonist-induced conformational change. In contrast, nAChR structural stability, flexibility, and function are all negatively influenced by simple changes in reconstituted membrane lipid composition. Our results suggest that deglycosylation may represent a feasible approach for enhancing the crystallizability of the nAChR. Our data also demonstrate that the dependence of nAChR structural stability on lipid environment may represent a significant obstacle to nAChR crystallization. Some membrane proteins may have evolved complex interactions with their lipid environments. Understanding the complexity of these interactions may be essential for devising an appropriate strategy for the crystallization of some membrane proteins.