Biomedical subjects

M Pelillo

Publications and source records attributed to M Pelillo.

3 recordsLinked to original sources

PubMed2004

Calculation of the molar absorptivity of polyphenols by using liquid chromatography with diode array detection: the case of carnosic acid.

Antioxidant activity of vegetable extracts is related to the nature and the amount of active components, mainly polyphenols; therefore, a correct quantification of these molecules should be required to define their concentration in such kind of vegetable extracts. A fast and accurate method to calculate molar absorption coefficients (epsilon), by using HPLC, has been tested on standard polyphenols and caffeine, and should be widely adapted for standardless quantitative analysis. Molar absorptivity (epsilon) of carnosic acid (CA) was determined from 200 to 300 nm, by the proposed method and those values were compared to tert-butyl-hydroxytoluene (BHT) ones for further comparative quantification.

Abietanes↗

PubMed2000

Mass spectral fragmentations of cholesterol acetate oxidation products.

In this work, electron-impact mass spectroscopy (EI-MS) was employed on a wide range of sterol compounds in order to study their behaviour with regard to their functional groups. In particular, some specific mechanisms of fragmentation occurring in these substrates (i.e. retro-Diels-Alder reaction, neutral molecules eliminations, specific hydrogen migrations) were investigated. Loss of the alkyl side chain and of the D ring were observed in all cases. Finally, a classification of sterols on the basis of characteristic mass spectral fragments is suggested, and further applications to substrates with functional groups on positions other than the A and B rings is proposed.

Animals↗

PubMed1999

Replicator equations, maximal cliques, and graph isomorphism.

We present a new energy-minimization framework for the graph isomorphism problem that is based on an equivalent maximum clique formulation. The approach is centered around a fundamental result proved by Motzkin and Straus in the mid-1960s, and recently expanded in various ways, which allows us to formulate the maximum clique problem in terms of a standard quadratic program. The attractive feature of this formulation is that a clear one-to-one correspondence exists between the solutions of the quadratic program and those in the original, combinatorial problem. To solve the program we use the so-called replicator equations--a class of straightforward continuous- and discrete-time dynamical systems developed in various branches of theoretical biology. We show how, despite their inherent inability to escape from local solutions, they nevertheless provide experimental results that are competitive with those obtained using more elaborate mean-field annealing heuristics.

Mathematics↗