Glutaraldehyde in bio-catalysts design: a useful crosslinker and a versatile tool in enzyme immobilization

Glutaraldehyde is one of the most widely used reagents in the design of biocatalysts. It is a powerful crosslinker, able to react with itself, with the advantages that this may bring forth. In this review, we intend to give a general vision of its potential and the precautions that must be taken when using this effective reagent. First, the chemistry of the glutaraldehyde/amino reaction will be commented upon. This reaction is still not fully clarified, but it seems to be based on the formation of 6-membered heterocycles formed by 5 C and one O. Then, we will discuss the production of intra- and inter-molecular enzyme crosslinks (increasing enzyme rigidity or preventing subunit dissociation in multimeric enzymes). Special emphasis will be placed on the preparation of cross-linked enzyme aggregates (CLEAs), mainly in enzymes that have low density of surface reactive groups and, therefore, may be problematic to obtain a final solid catalyst. Next, we will comment on the uses of glutaraldehyde in enzymes previously immobilized on supports. First, the treatment of enzymes immobilized on supports that cannot react with glutaraldehyde (only inter and intramolecular cross-linkings will be possible) to prevent enzyme leakage and obtain some enzyme stabilization via cross-linking. Second, the cross-linking of enzymes adsorbed on aminated supports, where together with other reactions enzyme/support crosslinking is also possible; the enzyme is incorporated into the support. Finally, we will present the use of aminated supports preactivated with glutaraldehyde. Optimal glutaraldehyde modifications will be discussed in each specific case (one or two glutaraldehyde molecules for amino group in the support and/or the protein). Using preactivated supports, the heterofunctional nature of the supports will be highlighted, with the drawbacks and advantages that the heterofunctionality may have. Particular attention will be paid to the control of the first event that causes the immobilization depending on the experimental conditions to alter the enzyme orientation regarding the support surface. Thus, glutaraldehyde, an apparently old fashioned reactive, remains the most widely used and with broadest application possibilities among the compounds used for the design of biocatalyst.

The EU internal market - a stake or a tool in European-Russian gas relations. OSW Commentary No. 54, 2011-06-24

Since 2010 we have observed a new quality in EU energy policy. It is related to the European Commission’s more or less direct engagement in the bilateral gas relations of a part of the new member states – Poland, Bulgaria and Lithuania – with Russia. Although the long term outcome of this activity of the EC is as yet unclear it seems to be important for several reasons. Firstly it might increase the possibilities of the enforcement of the EU’s directives liberalising the internal gas market and specifically their implementation in individual gas agreements with suppliers from third countries (Gazprom). The consistency and determination of the EC in this field may be decisive for the future direction and depth of the liberalisation of the EU gas market. Furthermore, present developments may lead to an increase in EU and specifically EC competence in the field of energy policy, especially its external dimension. So what lessons can we draw from recent Commission activities on the following issues: – Implementing EU gas market 2nd and 3rd liberalisation packages and their main provisions – EU energy policy and its external dimension – recent developments and the EU’s role – EU-Russia gas relations – where Russian and EU interests diverge.

Control charts as a tool in data quality improvement.

Mode of access: Internet.

Maximum likelihood as an operational tool in socio-economic modeling: as outlined in a recent thesis of D. W. Peterson. Final report.

Transportation Department, Office of Systems Engineering, Washington, D.C.

Soil analysis; a tool in crop production,

Mode of access: Internet.

The beta distribution in reliability and quality control /

Bibliography: leaves 41-43.

Self-assessment benchmarking as a quality management tool in primary healthcare

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Using the Agglomerative Method of Hierarchical Clustering as a Data Mining Tool in Capital Market

The purpose of this paper is to explain the notion of clustering and a concrete clustering method- agglomerative hierarchical clustering algorithm. It shows how a data mining method like clustering can be applied to the analysis of stocks, traded on the Bulgarian Stock Exchange in order to identify similar temporal behavior of the traded stocks. This problem is solved with the aid of a data mining tool that is called XLMiner™ for Microsoft Excel Office.