Standardization of BSE rapid test performances and experiences gathered during the implementation of large-scale testing

The accumulation of pathological prion protein is used as a diagnostic marker for transmissible spongiform encephalopathies. According to European Union (EU) regulations cattle older than 30 months of age (Germany, France, Italy, and Spain by national law >24 months) and slaughtered for human consumption must be tested by using rapid tests for bovine spongiform encephalopathy (BSE). Likewise fallen stock and clinically affected animals must be tested. This article gives a short overview of the incidence of BSE in Europe. The diagnostic hierarchy, i.e., the officially approved methodology for the confirmation of suspect rapid test cases, and the organization of the numerous laboratories involved in this large-scale testing for BSE are described. Special emphasis is given to necessary quality control measures currently in place for BSE rapid testing laboratories and to measures intended to assure a consistent performance of the commercially available rapid test kits.Presented at BERM-9—Ninth International Symposium on Biological and Environmental Reference Materials, 15–19 June 2003, Berlin, Germany.     

A Lagrangean heuristic algorithm for disassembly scheduling with capacity constraints

This paper considers the problem of determining the disassembly schedule (quantity and timing) of products in order to satisfy the demand of their parts or components over a finite planning horizon. The objective is to minimize the sum of set-up, disassembly operation, and inventory holding costs. As an extension of the uncapacitated versions of the problem, we consider the resource capacity restrictions over the planning horizon. An integer program is suggested to describe the problem mathematically, and to solve the problem, a heuristic is developed using a Lagrangean relaxation technique together with a method to find a good feasible solution while considering the trade-offs among different costs. The effectiveness of the algorithm is tested on a number of randomly generated problems and the test results show that the heuristic suggested in this paper can give near optimal solutions within a short amount of computation time.     

Complexation of Some Amino Acids and Peptides by p-Sulfonatocalix[4]arene and Hexasodium p-Sulfonatocalix[6]arene in Aqueous Solution

The stability constants (log K), the reaction enthalpy( H) and entropy ( S) of the complexesformed between some amino acids (glycine, L-alanine,L-valine, L-leucine, L-phenylalanine, L-tryptophan,L-threonine, and L-lysine) and peptides (glycyl-glycine,glycyl-L-alanine, glycyl-L-leucine, glycyl-L-phenylalanine,L-leucyl-glycine, L-leucyl-L-alanine, glycyl-L-valine,L-leucyl-glycyl-glycine, and glycyl-glycyl-glycine) withp-sulfonatocalix[4]arene and hexasodiump-sulfonatocalix[6]arene in aqueous solutions by meansof calorimetric titration have been investigated. The reportedresults demonstrate that the amino acids and peptides under studyform complexes with both p-sulfonatocalix[4]areneand hexasodium p-sulfonatocalix[6]arene. In the case of theamino acids and peptides the complexation with water-solublecalixarenes in aqueous solution is favored by enthalpiccontributions and disfavored by entropic contributions. However,no influence of the ring size of the calixarenes upon thecomplexation is observed. By comparison with the reaction ofthe sodium salt of phenol-4-sulfonic acid with amino acids amacrocyclic effect in case of the calixarenes is possible.     

Sulfur Compounds. 183. A Derivative of Perthiocarbonic Acid H2CS4: X-ray structural analysis of bis(triphenylmethyl) perthiocarbonate (Ph3C)2CS4

The molecular structure of Ph₃CSSC(S)SCPh₃ · CS₂ has been determined by X-ray structural analysis. The substance crystallizes in the triclinic crystal system [a = 884.9(2) pm, b = 1 039.5(2) pm, c = 2 064.6(3) pm, α = 75.86(1)°, β = 79.83(2)°, γ = 77.31(5)°, Z = 2, space group P1 ]. The CS₃ group is planar; the S? S-bond (201.4 pm) forms an angle of 5.7° with the CS₃ plane. The torsional angle CSSC equals 96.3°. (Ph₃C)₂CS₄ was obtained by reaction of TosNSCl₂ (Tos = p-MeC₆H₄SO₂) with Ph₃CSH in CS₂ in the presence of triethylamine. The reaction mechanism is discussed.     

Influence of protein concentration and order of addition on thermal stability of beta-lactoglobulin stabilized n-hexadecane oil-in-water emulsions at neutral pH

The influence of protein concentration and order of addition relative to homogenization (before or after) on the extent of droplet flocculation in heat-treated oil-in-water emulsions stabilized by a globular protein were examined using laser diffraction. n-Hexadecane (10 wt%) oil-in-water emulsions (pH 7, 150 mM NaCl) stabilized by beta-lactoglobulin (beta-Lg) were prepared by three methods: (1) 4 mg/mL beta-Lg added before homogenization; (2) 4 mg/mL beta-Lg added before homogenization and 6 mg/mL beta-Lg added after homogenization; (3) 10 mg/mL beta-Lg added before homogenization. The emulsions were then subjected to various isothermal heat treatments (30-95 degrees C for 20 min), with the 150 mM NaCl being added either before or after heating. Emulsion 1 contained little nonadsorbed protein and exhibited extensive droplet aggregation at all temperatures, which was attributed to the fact that the droplets had a high surface hydrophobicity, e.g., due to exposed oil or extensive protein surface denaturation. Emulsions 2 and 3 contained a significant fraction of nonadsorbed beta-Lg. When the NaCl was added before heating, these emulsions were relatively stable to droplet flocculation below a critical holding temperature (75 and 60 degrees C, respectively) but showed extensive flocculation above this temperature. The stability at low temperatures was attributed to the droplets having a relatively low surface hydrophobicity, e.g., due to complete saturation of the droplet surface with protein or due to more limited surface denaturation. The instability at high temperatures was attributed to thermal denaturation of the adsorbed and nonadsorbed proteins leading to increased hydrophobic interactions between droplets. When the salt was added to Emulsions 2 and 3 after heating, little droplet flocculation was observed at high temperatures, which was attributed to the dominance of intra-membrane over inter-membrane protein-protein interactions. Our data suggests that protein concentration and order of addition have a strong influence on the flocculation stability of protein-stabilized emulsions, which has important implications for the formulation and production of many emulsion-based products.     

Silver(I) Complexes with Nitrogen-Containing Noncyclic, Macrocyclic, and Macrobicyclic Ligands in Propylene Carbonate

Stability constants and thermodynamic data for complex formation of silver(I) with noncyclic, macrocyclic, and macrobicyclic ligands have been measured in propylene carbonate using potentiometric and calorimetric methods. All ligands containing two nitrogen donor atoms form extremely stable complexes. Only if substituents reduce the basicity of the nitrogen donor atoms, the stability of the complexes decreases drastically. However, the cryptand (221) forms the most stable complex of all ligands examined. In this case, the dimensions of the ligand cavity and of the cation are nearly identical.