Distribution of the best nonzero differential and linear approximations of s-box functions, Journal of Telecommunications and Information Technology, 2006, nr 3

In the paper the differential and the linear approximations of two classes of s-box functions are considered. The classes are the permutations and arbitrary functions with n binary inputs and m binary outputs, where 1≤n=m≤10. For randomly chosen functions from each of the classes, the two-dimensional distributions of the best nonzero approximations are investigated. The obtained results indicate that starting from some value of n, the linear approximation of s-box functions becomes more effective than the differential approximation. This advantage of the linear approximation rises with the increase of n and for DES size s-boxes is not yet visible

A homology model of restriction endonuclease SfiI in complex with DNA

BACKGROUND: Restriction enzymes (REases) are commercial reagents commonly used in recombinant DNA technologies. They are attractive models for studying protein-DNA interactions and valuable targets for protein engineering. They are, however, extremely divergent: the amino acid sequence of a typical REase usually shows no detectable similarities to any other proteins, with rare exceptions of other REases that recognize identical or very similar sequences. From structural analyses and bioinformatics studies it has been learned that some REases belong to at least four unrelated and structurally distinct superfamilies of nucleases, PD-DxK, PLD, HNH, and GIY-YIG. Hence, they are extremely hard targets for structure prediction and homology-based inference of sequence-function relationships and the great majority of REases remain structurally and evolutionarily unclassified. RESULTS: SfiI is a REase which recognizes the interrupted palindromic sequence 5'GGCCNNNN^NGGCC3' and generates 3 nt long 3' overhangs upon cleavage. SfiI is an archetypal Type IIF enzyme, which functions as a tetramer and cleaves two copies of the recognition site in a concerted manner. Its sequence shows no similarity to other proteins and nothing is known about the localization of its active site or residues important for oligomerization. Using the threading approach for protein fold-recognition, we identified a remote relationship between SfiI and BglI, a dimeric Type IIP restriction enzyme from the PD-DxK superfamily of nucleases, which recognizes the 5'GCCNNNN^NGGC3' sequence and whose structure in complex with the substrate DNA is available. We constructed a homology model of SfiI in complex with its target sequence and used it to predict residues important for dimerization, tetramerization, DNA binding and catalysis. CONCLUSIONS: The bioinformatics analysis suggest that SfiI, a Type IIF enzyme, is more closely related to BglI, an "orthodox" Type IIP restriction enzyme, than to any other REase, including other Type IIF REases with known structures, such as NgoMIV. NgoMIV and BglI belong to two different, very remotely related branches of the PD-DxK superfamily: the α-class (EcoRI-like), and the β-class (EcoRV-like), respectively. Thus, our analysis provides evidence that the ability to tetramerize and cut the two DNA sequences in a concerted manner was developed independently at least two times in the evolution of the PD-DxK superfamily of REases. The model of SfiI will also serve as a convenient platform for further experimental analyses

Networks of companies and branches in Poland

In this study we consider relations between companies in Poland taking into account common branches they belong to. It is clear that companies belonging to the same branch compete for similar customers, so the market induces correlations between them. On the other hand two branches can be related by companies acting in both of them. To remove weak, accidental links we shall use a concept of threshold filtering for weighted networks where a link weight corresponds to a number of existing connections (common companies or branches) between a pair of nodes.Comment: 13 pages, 10 figures and 4 table

Prefazione

La speciale attenzione con la quale il mondo delle lingue romanze oggi si riferisce alle questioni degli studi gender nel mondo accademico, affonda le sue radici in una tradizione antica, basata innanzitutto su uno sforzo costante di comprensio e. La letteratura contemporanea è un luogo privilegiato per la ricerca dell’identità sessuale. È, d’altro canto, significativo che una delle fasi più feconde dell’approfondimento dell’argomento si ha nel XXI secolo, in parallelo con lo sviluppo del clima culturale orientato verso la rinascita dell’antropologia

Isochronal conditions - the key to maintain the given solubility limit, of a small molecule within the polymer matrix, at elevated pressure

In this work, we proposed the method to maintain the desired level of drug’s solubility within the polymer matrix by adjusting conditions to uphold the same molecular dynamics of the system (e.g., temperature for set elevated pressure or vice versa). Namely, we observed, that recrystallization of the drug from the supersaturated drug−polymer system, initiated for the same structural relaxation time of the sample (τα‑1) ceases when certain, different than the initial, molecular mobility of the systems is reached (τα‑2)regardless of a given combination of temperature and pressure conditions. Based on the presented results, one can conclude that the molecular dynamics seem to control the process of recrystallization of the excess amount of solute from the supersaturated solution (e.g., small molecules dissolved within the polymer). Therefore, it appears that the elevated pressure compensates the effect of solubility enhancement caused by the elevated temperature. Such information not only is of fundamental relevance in science but also, from a much broader perspective, could be potentially very useful considering extrusion-based manufacturing methods

Physical Stability and Viscoelastic Properties of Co-Amorphous Ezetimibe/Simvastatin System

The purpose of this paper is to examine the physical stability as well as viscoelastic properties of the binary amorphous ezetimibe–simvastatin system. According to our knowledge, this is the first time that such an amorphous composition is prepared and investigated. The tendency toward re-crystallization of the amorphous ezetimibe–simvastatin system, at both standard storage and elevated temperature conditions, have been studied by means of X-ray diffraction (XRD). Our investigations have revealed that simvastatin remarkably improves the physical stability of ezetimibe, despite the fact that it works as a plasticizer. Pure amorphous ezetimibe, when stored at room temperature, begins to re-crystallize after 14 days after amorphization. On the other hand, the ezetimibe-simvastatin binary mixture (at the same storage conditions) is physically stable for at least 1 year. However, the devitrification of the binary amorphous composition was observed at elevated temperature conditions (T = 373 K). Therefore, we used a third compound to hinder the re-crystallization. Finally, both the physical stability as well as viscoelastic properties of the ternary systems containing different concentrations of the latter component have been thoroughly investigated

Compression-Induced Phase Transitions of Bicalutamide

The formation of solid dispersions with the amorphous drug dispersed in the polymeric matrix improves the dissolution characteristics of poorly soluble drugs. Although they provide an improved absorption after oral administration, the recrystallization, which can occur upon absorption of moisture or during solidification and other formulation stages, serves as a major challenge. This work aims at understanding the amorphization-recrystallization changes of bicalutamide. Amorphous solid dispersions with poly(vinylpyrrolidone-co-vinyl acetate) (PVP/VA) were obtained by either ball milling or spray drying. The applied processes led to drug amorphization as confirmed using X-ray diffraction and differential scanning calorimetry. Due to a high propensity towards mechanical activation, the changes of the crystal structure of physical blends of active pharmaceutical ingredient (API) and polymer upon pressure were also examined. The compression led to drug amorphization or transition from form I to form II polymorph, depending on the composition and applied force. The formation of hydrogen bonds confirmed using infrared spectroscopy and high miscibility of drug and polymer determined using non-isothermal dielectric measurements contributed to the high stability of amorphous solid dispersions. They exhibited improved wettability and dissolution enhanced by 2.5- to 11-fold in comparison with the crystalline drug. The drug remained amorphous upon compression when the content of PVP/VA in solid dispersions exceeded 20% or 33%, in the case of spray-dried and milled systems, respectively.Polish National Science Centre 2015/16/W/NZ7/0040

Mot de la Redaction

Si on peut constater que notre monde contemporain est orienté vers le ra-tionalisme, la technologie, la productivité, l’efficacité et la performance, on peut toujours s’interroger sur la place qu’il laisse encore aux manifestations rituelles. En effet, à l’origine de toute capacité de conceptualisation, l’existence des rites fut associée à la religion et, par ailleurs, au sacré. Dans ce contexte, il est utile de se poser la question de savoir si, aujourd’hui, l’espace relevant du sacrum se réduit dans l’ordre social, compte tenu du recul des pratiques religieuses dans les sociétés occidentales et autres (...

Mot de la Redaction

La diversité des opinions concerne tous les domaines de la vie sociale, ce qui engendre irrémédiablement de nombreux conflits entre différents points de vue. Suite à Raymond Williams (KeyworLa diversité des opinions concerne tous les domaines de la vie sociale, ce qui engendre irrémédiablement de nombreux conflits entre différents points de vue. Suite à Raymond Williams (Keywords: A Vocabulary of Culture and Society, 1983), qui disait que la culture était un processus social et historique, il est légitime de considérer cette dernière comme une succession ininterrompue de conflits, ainsi que de tentatives cherchant à les apaiser.ds: A Vocabulary of Culture and Society, 1983), qui disait que la culture était un processus social et historique, il est légitime de considérer cette dernière comme une succession ininterrompue de conflits, ainsi que de tentatives cherchant à les apaise (...