We present here for the first time the crystal structure of an AT-hook domain. We show the structure of an AT-hook of the ubiquitous nuclear protein HMGA1, combined with the oligonucleotide d(CGAATTAATTCG)2, which has two potential AATT interacting groups. Interaction with only one of them is found. The structure presents analogies and significant differences with previous NMR studies: the AT-hook forms hydrogen bonds between main-chain NH groups and thymines in the minor groove, DNA is bent and the minor groove is widened.

O ne well-established application of biotechnology is the use of enzymes in detergents. Enzymes are proteins that act as biochemical catalysts and that increase the rate of specific reactions by several orders of magnitude (usually g10 6 ). Cells cannot function without enzymes, but under controlled conditions, enzymes can work outside of the cell. This discovery led to the development of a growing number of industrial applications of enzymes. One of the main applications of enzymes is their use in detergents (especially laundry and dishwashing detergents) to help in cleaning. Enzymes (especially proteolytic enzymes) are found in products ranging from household laundry and dishwashing detergents to products for contact lens and denture cleaning. However, household laundry is the biggest market.A measure of success of a laboratory exercise, both in terms of effective learning and motivation, is student engagement. A problembased approach is one way to achieve this, especially if the laboratory relates to familiar industrial or home activities. Thus, a household detergent was chosen to study one of the applications of the catalytic power of enzymes. A number of basic concepts can be examined: the amino acid composition of proteins, the influence of factors such as pH or temperature on enzyme activity, the effect of denaturation, enzyme inhibition, and so forth. Students also become acquainted with polyacrylamide gel electrophoresis, which is used to see the products of the proteolytic enzyme activity on a protein substrate. This exercise has received positive response from students over the four years it has been performed. ' BACKGROUNDAs reviewed elsewhere, 1,2 the first patent for the use of enzymes in a presoaking product originated in 1913. However, it was not until 1965 that the use of enzymes in detergents came into general use. There was a massive increase in the use of enzymes between 1966 and 1969, but this growth reversed dramatically in 1969À1970 due to hypersensitivity reactions in factory workers handling the dusty enzyme products. The situation was readily understood, and dust-free granulated detergent enzymes were developed. The granulated preparations frequently consist of a core containing the enzyme, surrounded by a coating of inert material that contains a pigment to give it the desired color. The quantity of enzymes in detergents is low (0.1À1%).Proteolytic enzymes (proteases) were the first enzymes to be included in detergents and are still the most used. Proteolytic enzymes degrade proteins by cleaving the peptide bonds, thus assisting in the removal of protein-based stains such as blood and many types of food. Some of these enzymes break all peptide bonds, whereas there are other more specific proteases that only cleave those peptide bonds in which a particular amino acid is involved.3 The most widely used protease is subtilisin (named after the bacterium Bacillus subtilis). It is typically obtained by the industrial culture of related Bacillus species. Subtilisin is a nonspecific serine end...

We present a new structure of a DNA dodecamer obtained in the presence of Ni 2+ ions. The DNA forms Ni-guanine cross-links between neighboring molecules. Our results show that an adequate dosage of Ni 2+ may help to form well-defined DNA nanostructures. We also compare our structure with other dodecamers which present unique features and also crystallize in trigonal unit cells, strongly influenced by the counterions associated with DNA. In all cases, the DNA duplexes form parallel pseudohelical columns in the crystal, similar to DNA-protamine and native DNA fibers.

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