Application of artificial neural networks to prediction of new substances with antimicrobial activity against Escherichia coli.

AIMS: This article presents models of artificial neural networks (ANN) employed to predict the biological activity of chemical compounds based of their structure. Regression and classification models were designed to determine antimicrobial properties of quaternary ammonium salts against Escherichia coli strain. METHODS AND RESULTS: The minimum inhibitory concentration microbial growth E. coli was experimentally determined by the serial dilution method for a series of 140 imidazole derivatives. Then, three-dimensional models for imidazole chlorides were constructed with computational chemistry methods which allowed to calculate molecular descriptors. The transformation of chemical information into a useful number is a main result of this operation. The designed regression and classification ANN models were characterized by a high predictive ability (classification accuracy was 95%, regression model: learning set R = 0.87, testing set R = 0.91, validation set R = 0.89). CONCLUSIONS: Artificial neural networks can be successfully used to find potential antimicrobial preparations. SIGNIFICANCE AND IMPACT OF THE STUDY: The neural networks are a very elaborate modelling technique, which allows not only to optimize and minimize labour costs but also to increase food safety.

Small-angle water reorientations in KOH doped hexagonal ice and clathrate hydrates.

Using deuteron nuclear magnetic resonance and dielectric spectroscopy KOH doped tetrahydrofuran clathrate hydrates and KOH doped hexagonal ice are studied at temperatures above 60 and 72 K, respectively. Below these temperatures proton order is established on the lattice formed by the water molecules. In the clathrate hydrate a new type of small-angle motion is discovered using deuteron spin-spin relaxation, line-shape analysis, and stimulated-echo experiments. Based on the latter results a model is developed for the local proton motion that could successfully be tested using random-walk simulations. It is argued that the newly identified small-angle motion, obviously absent in undoped samples, is an important feature of the mechanism which accompanies the establishment of proton order not only in doped clathrate hydrates but also in doped hexagonal ice. Specific motions of OH(-) defects are demonstrated to explain the experimentally observed behavior. The relative importance of localized versus delocalized OH(-) defect motions is discussed.

Water dynamics on the hydrate lattice of a tetrabutyl ammonium bromide semiclathrate.

Deuteron nuclear magnetic resonance (NMR) and dielectric spectroscopy are utilized to investigate the dynamics of the water molecules in the semiclathrate (tetra-n-butyl ammonium bromide) 26 H(2)O. Stimulated-echo spectroscopy reveals a nonexponential correlation function predominantly due to rotational motion with jump angles that are broadly distributed around the tetrahedral angle. The reorientational correlation times from this technique agree excellently with those from dielectric measurements, both resulting in an activation energy of (43+/-1) kJ/mol. Large, spatially varying electrical dipolar fields, set up by the Br(-) and the N(+) ions located on the hydrate lattice, are held responsible for the pronounced stretching of the correlation functions. Solid-echo spectra were acquired over a broad temperature range. They exhibit an apparent two-phase character discussed in terms of various scenarios. Two-dimensional NMR spectra and four-time stimulated echoes were recorded, but an exchange of slow and fast subensembles could not be detected. Spin-lattice relaxation does not directly reflect the local reorientational motion and its nonexponentiality is interpreted with reference to the translational dynamics of the water molecules.

Correlation of primary relaxations and high-frequency modes in supercooled liquids. II. Evidence from spin-lattice relaxation weighted stimulated-echo spectroscopy.

Using spin-lattice relaxation weighted stimulated-echo spectroscopy, we report evidence for a correlation of the primary and secondary relaxation times. The experiments are performed using deuteron nuclear magnetic resonance somewhat above the calorimetric glass-transition of ortho-terphenyl, D-sorbitol, and cresolphthalein-dimethylether. The data analysis is based on the procedure outlined in the accompanying theoretical paper [B. Geil, G. Diezemann, and R. Böhmer, Phys. Rev. E 74, 041504 (2006)]. Direct experimental evidence for a modified spin-lattice relaxation is obtained from measurements on a methyl deuterated acetyl salicylic acid glass. The limitations of the present experimental method are discussed.

Correlation of primary and secondary relaxations in a supercooled liquid.

The widespread assumption that primary and secondary relaxations in glass-forming materials are independent processes is scrutinized using spin-lattice relaxation weighted stimulated-echo spectroscopy. This nuclear magnetic resonance (NMR) technique is simultaneously sensitive to the dynamics on well-separated time scales. For the deeply supercooled liquid sorbitol, which exhibits a strong secondary relaxation, the primary relaxation (that is observable using NMR) can be modified by suppressing the contributions of those subensembles which are characterized by relatively slow secondary relaxations. This is clear evidence for a correlation between primary and secondary relaxation times. In the disordered crystal orthocarborane high-frequency processes are absent and consequently no such modifications could be achieved.

[Treatment of acute immune thrombocytopenic purpura in children--intravenous immunoglobulin or treatment with corticosteroids?]. / Leczenie ostrej immunologicznej skazy maloplytkowej u dzieci--dozylne stosowanie preparatów immunoglobulin czy leczenie kortykosteroidami?

The results of treatment of newly diagnosed patients with immune thrombocytopenic purpura are described. Forty seven patients were treated with prednisone 1-2 mg/kg body weight/24 hours and 13 with simplified methods of giving immunoglobulins (2 x 0.4 g/kg body weight/24 hours). An increase of platelet number to 150 G/l was achieved in 43/47 patients treated with prednisone after 3-104 days (mean 22 days) and significantly faster in 12/13 treated with immunoglobulins (after 3-17 days, mean 7 days). The effect was stable in 30/43 patients in group I (prednisone) and in 11/13 in group II (Igiv). The disease evolved to the chronic form in 15/47 patients treated with prednisone and in 1/13 treated with immunoglobulins. No life-threatening bleedings were observed.