Circular dichroic constrained structure optimization of homoalanine peptides

This article describes a new method for peptide structure optimization within a Monte Carlo Simulated Annealing (MCSA) framework, namely the cominimization of potential energies under the constraint of a calculated Circular Dichroism (CD) spectrum. We compute potential energy as well as the CD spectrum of every structure generated within the course of the MCSA run, and cooptimize the mean deviation of this calculated spectrum to a corresponding experimental spectrum together with the potential energies of the respective structures using a modified Metropolis Criterion within the MCSA scheme. We compare the performance of this technique with two other MCSA optimization variants—first, a cominimization of potential energies and free energies of solvation; and second, the standard minimization of potential energy alone. We use homoalanines in lengths of 10 and 15, whose optimized structures are highly α‐helical, and correspondingly give α‐helix characteristic CD signals as the test peptides. This circular dichroic constrained optimization of potential energies is, compared to the other methods, highly efficient in locating α‐helical structures with lowest potential energies in both the 10 alanine and the 15 alanine peptide system, within short MCSA runs. The overall structural information embedded in the CD spectrum efficiently guides the optimization towards the native peptide structure. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 270–281, 2000     

Hybrid thermotropic liquid-crystalline block copolymers

A new approach to the preparation of two classes of block copolymers containing liquid-crystalline segments is reported. Copolymers 1 and 2 are constituted by polytetrahydrofuran and side-chain liquid-crystalline polymethacrylate blocks, whereas block copolymers 3 consist of polystyrene and main-chain liquid-crystalline polyester blocks. The synthetic procedures leading to copolymers 1-3 are extremely versatile and can be used to prepare a great variety of block copolymer architectures. In both copolymer classes the chemically different blocks are strongly segregated in the solid and melt phases and undergo individual phase transitions. The mesophase transition temperatures of the liquid-crystalline blocks are very similar to those of the corresponding homopolymers, and their enthalpies are directly proportional to the content of the liquid-crystalline block.     

CFD modelling of a spray deposition process of paint

The paint deposition process by spraying has been studied by means of Computational Fluid Dynamics in order to predict the final thickness of the coating and to determine theoretically the overspraying phenomenon. The VOF model has been used to describe the impact phenomena onto the wall and the Euler-Lagrange approach to simulate droplet trajectories on their way to the surface. Particular attention has been devoted to the prediction of the maximum diameter reached by an impinging droplet at the end of the spreading phase. This diameter is very important in the study of the paint processes because the high viscosity and the small surface tension of paints reduce the impingement practically only to the spreading phase. Two different configurations of atomizers have been considered. The air flux provides a finer atomisation of the liquid, gives to the droplets the necessary velocity to reach the wall, but is also the main cause of overspray since the small droplets tend to follow its deviation near the wall.     

Phenylhydrazine–borane adduct—characterized in the solid state and in solution

The 1:1 phenylhydrazine–borane adduct, obtained from phenylhydrazine and sodium borohydride in acidic solution, was investigated by IR, NMR spectroscopy, and MS spectrometry. Ab initio MO calculations indicated the isomer in which the boron center is attached to the primary amino group as the more stable. This forecast was confirmed by solution‐state ¹H, ¹¹B, ¹³C, and ¹⁵N NMR spectroscopy, in agreement with the molecular structure in the solid state determined by X‐ray analysis. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:366–372, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10049     

Efficient DNA Extraction and Amplification of Samples from the Archeological Site of Pompei (Italy)

Due to their growth and metabolism, microorganisms can cause severe damage to Cultural Heritage, through mechanical and chemical processes. In this paper we used molecular approaches to study bacterial communities on samples from the archeological site of Pompei (Italy). In particular four DNA extraction methods without prior cultivation of the microflora were compared. In terms of efficiency, the DNA extraction method based on the Tri-Reagent™ kit gave the best results. All extraction protocols coupled with 16S rDNA fragments PCR amplification were satisfactory; but the best results were obtained by Klentaq DNA LA Polymerase™; this enzyme can be considered an effective tool for amplification of DNA from Cultural Heritage and possibly other environmental samples.