Novel Molecular Matrices

Randic, M., Basak, N. and Plavsic, D. (2004) Novel graphical matrix and distance-based molecular descriptors. Croat. Chem. Acta, 77, 251—257. 

The LB technique may also be combined with solid-state chemistry methods to produce novel molecular architectures. For example, a network of conductive polypyrrole (molecular wires ) may be obtained in a fatty acid matrix [37, 38]. First, monolayers of the iron salt of a long-chain fatty acid (e.g., ferric pahnitate) are assembled on an appropriate substrate. The multilayer film is then exposed to saturated HCl vapor at room temperature for several minutes. During this process, a chemical reaction transforms the fatty acid salt into layers of ferric chloride separated by layers of fatty acid. In the third and final step, the film is exposed to pyrrole vapor and a reaction occurs between the pyrrole and the ferric chloride, producing polypyrrole distributed within the multilayer assembly. 

Summation of nonzero elements in the upper or lower matrix-triangles gives the Wiener index (Wiener number). The edge-Wiener matrix was also found to be a rich and stimulating source of novel molecular descriptors (Randid et al., 1993, 1994 Lucid et al., 2003). 

Abstract. We present novel time integration schemes for Newtonian dynamics whose fastest oscillations are nearly harmonic, for constrained Newtonian dynamics including the Car-Parrinello equations of ab initio molecular dynamics, and for mixed quantum-classical molecular dynamics. The methods attain favorable properties by using matrix-function vector products which are computed via Lanczos method. This permits to take longer time steps than in standard integrators. 

A review focusing on recent genetic and molecular biological studies of the matrix proteoglycans. The structure-function relationships of some paradigmatic proteoglycans are discussed in depth, and novel aspects of their biology are examined. 

The use of novel electrode materials should, in principle, improve the reproducibility of the biosensor, since the screen-printing process is thought to be responsible for the standard deviation of the electrochemical measurements. The developed biosensor can also be applied to the analysis of water. In this case, the matrix is expected to produce fewer effects. Finally, the use of molecularly engineered supersensitive enzymes and the combination with signal amplification systems can contribute to increase the sensitivity of the biosensor. 

The computation of molecular vibrations is possible with all methods for structure refinement which compute the Hessian matrix (for MM this is the case for optimizers based on second derivatives such as the Newton-Raphson method18). The computed frequencies may then be used for comparison with experimental data90. Recent developments in this area are novel QM-based approaches for the efficient computation of specific vibrational frequencies in large molecules.177... 

MS has become an indispensable tool for the determination of carbohydrate structures. The information provided by this methodology ranges from accurate molecular weight determination to the complete primary structure, with picomole sensitivity. These remarkable advances have been possible because of the development of novel methods of ionization, such as fast atom bombardment (FAB) ionization, ESI, and matrix-assisted laser desorption/ionization (MALDI) (Fig. 3). 

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